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LU-3469 osp: osp_sync() to flush pending changes synchronously
[fs/lustre-release.git] / lustre / lfsck / lfsck_layout.c
index efe305a..98e61d2 100644 (file)
@@ -34,6 +34,7 @@
 #define DEBUG_SUBSYSTEM S_LFSCK
 
 #include <linux/bitops.h>
+#include <linux/rbtree.h>
 
 #include <lustre/lustre_idl.h>
 #include <lu_object.h>
@@ -64,6 +65,10 @@ struct lfsck_layout_seq {
 struct lfsck_layout_slave_target {
        /* link into lfsck_layout_slave_data::llsd_master_list. */
        struct list_head        llst_list;
+       /* The position for next record in the rbtree for iteration. */
+       struct lu_fid           llst_fid;
+       /* Dummy hash for iteration against the rbtree. */
+       __u64                   llst_hash;
        __u64                   llst_gen;
        atomic_t                llst_ref;
        __u32                   llst_index;
@@ -77,6 +82,10 @@ struct lfsck_layout_slave_data {
        struct list_head         llsd_master_list;
        spinlock_t               llsd_lock;
        __u64                    llsd_touch_gen;
+       struct dt_object        *llsd_rb_obj;
+       struct rb_root           llsd_rb_root;
+       rwlock_t                 llsd_rb_lock;
+       unsigned int             llsd_rbtree_valid:1;
 };
 
 struct lfsck_layout_object {
@@ -133,6 +142,34 @@ struct lfsck_layout_slave_async_args {
        struct lfsck_layout_slave_target *llsaa_llst;
 };
 
+static struct lfsck_layout_object *
+lfsck_layout_object_init(const struct lu_env *env, struct dt_object *obj,
+                        __u16 gen)
+{
+       struct lfsck_layout_object *llo;
+       int                         rc;
+
+       OBD_ALLOC_PTR(llo);
+       if (llo == NULL)
+               return ERR_PTR(-ENOMEM);
+
+       rc = dt_attr_get(env, obj, &llo->llo_attr, BYPASS_CAPA);
+       if (rc != 0) {
+               OBD_FREE_PTR(llo);
+
+               return ERR_PTR(rc);
+       }
+
+       lu_object_get(&obj->do_lu);
+       llo->llo_obj = obj;
+       /* The gen can be used to check whether some others have changed the
+        * file layout after LFSCK pre-fetching but before real verification. */
+       llo->llo_gen = gen;
+       atomic_set(&llo->llo_ref, 1);
+
+       return llo;
+}
+
 static inline void
 lfsck_layout_llst_put(struct lfsck_layout_slave_target *llst)
 {
@@ -195,14 +232,17 @@ lfsck_layout_llst_del(struct lfsck_layout_slave_data *llsd,
 
 static inline struct lfsck_layout_slave_target *
 lfsck_layout_llst_find_and_del(struct lfsck_layout_slave_data *llsd,
-                              __u32 index)
+                              __u32 index, bool unlink)
 {
        struct lfsck_layout_slave_target *llst;
 
        spin_lock(&llsd->llsd_lock);
        list_for_each_entry(llst, &llsd->llsd_master_list, llst_list) {
                if (llst->llst_index == index) {
-                       list_del_init(&llst->llst_list);
+                       if (unlink)
+                               list_del_init(&llst->llst_list);
+                       else
+                               atomic_inc(&llst->llst_ref);
                        spin_unlock(&llsd->llsd_lock);
 
                        return llst;
@@ -222,6 +262,26 @@ static inline void lfsck_layout_object_put(const struct lu_env *env,
        }
 }
 
+static struct lfsck_layout_req *
+lfsck_layout_req_init(struct lfsck_layout_object *parent,
+                     struct dt_object *child, __u32 ost_idx, __u32 lov_idx)
+{
+       struct lfsck_layout_req *llr;
+
+       OBD_ALLOC_PTR(llr);
+       if (llr == NULL)
+               return ERR_PTR(-ENOMEM);
+
+       INIT_LIST_HEAD(&llr->llr_list);
+       atomic_inc(&parent->llo_ref);
+       llr->llr_parent = parent;
+       llr->llr_child = child;
+       llr->llr_ost_idx = ost_idx;
+       llr->llr_lov_idx = lov_idx;
+
+       return llr;
+}
+
 static inline void lfsck_layout_req_fini(const struct lu_env *env,
                                         struct lfsck_layout_req *llr)
 {
@@ -242,6 +302,377 @@ static inline bool lfsck_layout_req_empty(struct lfsck_layout_master_data *llmd)
        return empty;
 }
 
+static int lfsck_layout_get_lovea(const struct lu_env *env,
+                                 struct dt_object *obj,
+                                 struct lu_buf *buf, ssize_t *buflen)
+{
+       int rc;
+
+again:
+       rc = dt_xattr_get(env, obj, buf, XATTR_NAME_LOV, BYPASS_CAPA);
+       if (rc == -ERANGE) {
+               rc = dt_xattr_get(env, obj, &LU_BUF_NULL, XATTR_NAME_LOV,
+                                 BYPASS_CAPA);
+               if (rc <= 0)
+                       return rc;
+
+               lu_buf_realloc(buf, rc);
+               if (buflen != NULL)
+                       *buflen = buf->lb_len;
+
+               if (buf->lb_buf == NULL)
+                       return -ENOMEM;
+
+               goto again;
+       }
+
+       if (rc == -ENODATA)
+               rc = 0;
+
+       if (rc <= 0)
+               return rc;
+
+       if (unlikely(buf->lb_buf == NULL)) {
+               lu_buf_alloc(buf, rc);
+               if (buflen != NULL)
+                       *buflen = buf->lb_len;
+
+               if (buf->lb_buf == NULL)
+                       return -ENOMEM;
+
+               goto again;
+       }
+
+       return rc;
+}
+
+static int lfsck_layout_verify_header(struct lov_mds_md_v1 *lmm)
+{
+       __u32 magic;
+       __u32 pattern;
+
+       magic = le32_to_cpu(lmm->lmm_magic);
+       /* If magic crashed, keep it there. Sometime later, during OST-object
+        * orphan handling, if some OST-object(s) back-point to it, it can be
+        * verified and repaired. */
+       if (magic != LOV_MAGIC_V1 && magic != LOV_MAGIC_V3) {
+               struct ost_id   oi;
+               int             rc;
+
+               lmm_oi_cpu_to_le(&oi, &lmm->lmm_oi);
+               if ((magic & LOV_MAGIC_MASK) == LOV_MAGIC_MAGIC)
+                       rc = -EOPNOTSUPP;
+               else
+                       rc = -EINVAL;
+
+               CDEBUG(D_LFSCK, "%s LOV EA magic %u on "DOSTID"\n",
+                      rc == -EINVAL ? "Unknown" : "Unsupported",
+                      magic, POSTID(&oi));
+
+               return rc;
+       }
+
+       pattern = le32_to_cpu(lmm->lmm_pattern);
+       /* XXX: currently, we only support LOV_PATTERN_RAID0. */
+       if (lov_pattern(pattern) != LOV_PATTERN_RAID0) {
+               struct ost_id oi;
+
+               lmm_oi_cpu_to_le(&oi, &lmm->lmm_oi);
+               CDEBUG(D_LFSCK, "Unsupported LOV EA pattern %u on "DOSTID"\n",
+                      pattern, POSTID(&oi));
+
+               return -EOPNOTSUPP;
+       }
+
+       return 0;
+}
+
+#define LFSCK_RBTREE_BITMAP_SIZE       PAGE_CACHE_SIZE
+#define LFSCK_RBTREE_BITMAP_WIDTH      (LFSCK_RBTREE_BITMAP_SIZE << 3)
+#define LFSCK_RBTREE_BITMAP_MASK       (LFSCK_RBTREE_BITMAP_WIDTH - 1)
+
+struct lfsck_rbtree_node {
+       struct rb_node   lrn_node;
+       __u64            lrn_seq;
+       __u32            lrn_first_oid;
+       atomic_t         lrn_known_count;
+       atomic_t         lrn_accessed_count;
+       void            *lrn_known_bitmap;
+       void            *lrn_accessed_bitmap;
+};
+
+static inline int lfsck_rbtree_cmp(struct lfsck_rbtree_node *lrn,
+                                  __u64 seq, __u32 oid)
+{
+       if (seq < lrn->lrn_seq)
+               return -1;
+
+       if (seq > lrn->lrn_seq)
+               return 1;
+
+       if (oid < lrn->lrn_first_oid)
+               return -1;
+
+       if (oid - lrn->lrn_first_oid >= LFSCK_RBTREE_BITMAP_WIDTH)
+               return 1;
+
+       return 0;
+}
+
+/* The caller should hold llsd->llsd_rb_lock. */
+static struct lfsck_rbtree_node *
+lfsck_rbtree_search(struct lfsck_layout_slave_data *llsd,
+                   const struct lu_fid *fid, bool *exact)
+{
+       struct rb_node           *node  = llsd->llsd_rb_root.rb_node;
+       struct rb_node           *prev  = NULL;
+       struct lfsck_rbtree_node *lrn   = NULL;
+       int                       rc    = 0;
+
+       if (exact != NULL)
+               *exact = true;
+
+       while (node != NULL) {
+               prev = node;
+               lrn = rb_entry(node, struct lfsck_rbtree_node, lrn_node);
+               rc = lfsck_rbtree_cmp(lrn, fid_seq(fid), fid_oid(fid));
+               if (rc < 0)
+                       node = node->rb_left;
+               else if (rc > 0)
+                       node = node->rb_right;
+               else
+                       return lrn;
+       }
+
+       if (exact == NULL)
+               return NULL;
+
+       /* If there is no exactly matched one, then to the next valid one. */
+       *exact = false;
+
+       /* The rbtree is empty. */
+       if (rc == 0)
+               return NULL;
+
+       if (rc < 0)
+               return lrn;
+
+       node = rb_next(prev);
+
+       /* The end of the rbtree. */
+       if (node == NULL)
+               return NULL;
+
+       lrn = rb_entry(node, struct lfsck_rbtree_node, lrn_node);
+
+       return lrn;
+}
+
+static struct lfsck_rbtree_node *lfsck_rbtree_new(const struct lu_env *env,
+                                                 const struct lu_fid *fid)
+{
+       struct lfsck_rbtree_node *lrn;
+
+       OBD_ALLOC_PTR(lrn);
+       if (lrn == NULL)
+               return ERR_PTR(-ENOMEM);
+
+       OBD_ALLOC(lrn->lrn_known_bitmap, LFSCK_RBTREE_BITMAP_SIZE);
+       if (lrn->lrn_known_bitmap == NULL) {
+               OBD_FREE_PTR(lrn);
+
+               return ERR_PTR(-ENOMEM);
+       }
+
+       OBD_ALLOC(lrn->lrn_accessed_bitmap, LFSCK_RBTREE_BITMAP_SIZE);
+       if (lrn->lrn_accessed_bitmap == NULL) {
+               OBD_FREE(lrn->lrn_known_bitmap, LFSCK_RBTREE_BITMAP_SIZE);
+               OBD_FREE_PTR(lrn);
+
+               return ERR_PTR(-ENOMEM);
+       }
+
+       rb_init_node(&lrn->lrn_node);
+       lrn->lrn_seq = fid_seq(fid);
+       lrn->lrn_first_oid = fid_oid(fid) & ~LFSCK_RBTREE_BITMAP_MASK;
+       atomic_set(&lrn->lrn_known_count, 0);
+       atomic_set(&lrn->lrn_accessed_count, 0);
+
+       return lrn;
+}
+
+static void lfsck_rbtree_free(struct lfsck_rbtree_node *lrn)
+{
+       OBD_FREE(lrn->lrn_accessed_bitmap, LFSCK_RBTREE_BITMAP_SIZE);
+       OBD_FREE(lrn->lrn_known_bitmap, LFSCK_RBTREE_BITMAP_SIZE);
+       OBD_FREE_PTR(lrn);
+}
+
+/* The caller should hold lock. */
+static struct lfsck_rbtree_node *
+lfsck_rbtree_insert(struct lfsck_layout_slave_data *llsd,
+                   struct lfsck_rbtree_node *lrn)
+{
+       struct rb_node           **pos    = &llsd->llsd_rb_root.rb_node;
+       struct rb_node            *parent = NULL;
+       struct lfsck_rbtree_node  *tmp;
+       int                        rc;
+
+       while (*pos != NULL) {
+               parent = *pos;
+               tmp = rb_entry(parent, struct lfsck_rbtree_node, lrn_node);
+               rc = lfsck_rbtree_cmp(tmp, lrn->lrn_seq, lrn->lrn_first_oid);
+               if (rc < 0)
+                       pos = &(*pos)->rb_left;
+               else if (rc > 0)
+                       pos = &(*pos)->rb_right;
+               else
+                       return tmp;
+       }
+
+       rb_link_node(&lrn->lrn_node, parent, pos);
+       rb_insert_color(&lrn->lrn_node, &llsd->llsd_rb_root);
+
+       return lrn;
+}
+
+extern const struct dt_index_operations lfsck_orphan_index_ops;
+
+static int lfsck_rbtree_setup(const struct lu_env *env,
+                             struct lfsck_component *com)
+{
+       struct lu_fid                   *fid    = &lfsck_env_info(env)->lti_fid;
+       struct lfsck_instance           *lfsck  = com->lc_lfsck;
+       struct dt_device                *dev    = lfsck->li_bottom;
+       struct lfsck_layout_slave_data  *llsd   = com->lc_data;
+       struct dt_object                *obj;
+
+       fid->f_seq = FID_SEQ_LAYOUT_RBTREE;
+       fid->f_oid = lfsck_dev_idx(dev);
+       fid->f_ver = 0;
+       obj = dt_locate(env, dev, fid);
+       if (IS_ERR(obj))
+               RETURN(PTR_ERR(obj));
+
+       /* Generate an in-RAM object to stand for the layout rbtree.
+        * Scanning the layout rbtree will be via the iteration over
+        * the object. In the future, the rbtree may be written onto
+        * disk with the object.
+        *
+        * Mark the object to be as exist. */
+       obj->do_lu.lo_header->loh_attr |= LOHA_EXISTS;
+       obj->do_index_ops = &lfsck_orphan_index_ops;
+       llsd->llsd_rb_obj = obj;
+       llsd->llsd_rbtree_valid = 1;
+       dev->dd_record_fid_accessed = 1;
+
+       return 0;
+}
+
+static void lfsck_rbtree_cleanup(const struct lu_env *env,
+                                struct lfsck_component *com)
+{
+       struct lfsck_instance           *lfsck = com->lc_lfsck;
+       struct lfsck_layout_slave_data  *llsd  = com->lc_data;
+       struct rb_node                  *node  = rb_first(&llsd->llsd_rb_root);
+       struct rb_node                  *next;
+       struct lfsck_rbtree_node        *lrn;
+
+       lfsck->li_bottom->dd_record_fid_accessed = 0;
+       /* Invalid the rbtree, then no others will use it. */
+       write_lock(&llsd->llsd_rb_lock);
+       llsd->llsd_rbtree_valid = 0;
+       write_unlock(&llsd->llsd_rb_lock);
+
+       while (node != NULL) {
+               next = rb_next(node);
+               lrn = rb_entry(node, struct lfsck_rbtree_node, lrn_node);
+               rb_erase(node, &llsd->llsd_rb_root);
+               lfsck_rbtree_free(lrn);
+               node = next;
+       }
+
+       if (llsd->llsd_rb_obj != NULL) {
+               lu_object_put(env, &llsd->llsd_rb_obj->do_lu);
+               llsd->llsd_rb_obj = NULL;
+       }
+}
+
+static void lfsck_rbtree_update_bitmap(const struct lu_env *env,
+                                      struct lfsck_component *com,
+                                      const struct lu_fid *fid,
+                                      bool accessed)
+{
+       struct lfsck_layout_slave_data  *llsd   = com->lc_data;
+       struct lfsck_rbtree_node        *lrn;
+       bool                             insert = false;
+       int                              idx;
+       int                              rc     = 0;
+       ENTRY;
+
+       CDEBUG(D_LFSCK, "%s: update bitmap for "DFID"\n",
+              lfsck_lfsck2name(com->lc_lfsck), PFID(fid));
+
+       if (unlikely(!fid_is_sane(fid) || fid_is_last_id(fid)))
+               RETURN_EXIT;
+
+       if (!fid_is_idif(fid) && !fid_is_norm(fid))
+               RETURN_EXIT;
+
+       read_lock(&llsd->llsd_rb_lock);
+       if (!llsd->llsd_rbtree_valid)
+               GOTO(unlock, rc = 0);
+
+       lrn = lfsck_rbtree_search(llsd, fid, NULL);
+       if (lrn == NULL) {
+               struct lfsck_rbtree_node *tmp;
+
+               LASSERT(!insert);
+
+               read_unlock(&llsd->llsd_rb_lock);
+               tmp = lfsck_rbtree_new(env, fid);
+               if (IS_ERR(tmp))
+                       GOTO(out, rc = PTR_ERR(tmp));
+
+               insert = true;
+               write_lock(&llsd->llsd_rb_lock);
+               if (!llsd->llsd_rbtree_valid) {
+                       lfsck_rbtree_free(tmp);
+                       GOTO(unlock, rc = 0);
+               }
+
+               lrn = lfsck_rbtree_insert(llsd, tmp);
+               if (lrn != tmp)
+                       lfsck_rbtree_free(tmp);
+       }
+
+       idx = fid_oid(fid) & LFSCK_RBTREE_BITMAP_MASK;
+       /* Any accessed object must be a known object. */
+       if (!test_and_set_bit(idx, lrn->lrn_known_bitmap))
+               atomic_inc(&lrn->lrn_known_count);
+       if (accessed && !test_and_set_bit(idx, lrn->lrn_accessed_bitmap))
+               atomic_inc(&lrn->lrn_accessed_count);
+
+       GOTO(unlock, rc = 0);
+
+unlock:
+       if (insert)
+               write_unlock(&llsd->llsd_rb_lock);
+       else
+               read_unlock(&llsd->llsd_rb_lock);
+out:
+       if (rc != 0 && accessed) {
+               struct lfsck_layout *lo = com->lc_file_ram;
+
+               CERROR("%s: Fail to update object accessed bitmap, will cause "
+                      "incorrect LFSCK OST-object handling, so disable it to "
+                      "cancel orphan handling for related device. rc = %d.\n",
+                      lfsck_lfsck2name(com->lc_lfsck), rc);
+               lo->ll_flags |= LF_INCOMPLETE;
+               lfsck_rbtree_cleanup(env, com);
+       }
+}
+
 static void lfsck_layout_le_to_cpu(struct lfsck_layout *des,
                                   const struct lfsck_layout *src)
 {
@@ -361,7 +792,8 @@ static int lfsck_layout_store(const struct lu_env *env,
                RETURN(rc);
        }
 
-       rc = dt_declare_record_write(env, obj, size, pos, handle);
+       rc = dt_declare_record_write(env, obj, lfsck_buf_get(env, lo, size),
+                                    pos, handle);
        if (rc != 0) {
                CERROR("%s: fail to declare trans for storing lfsck_layout(1): "
                       "rc = %d\n", lfsck_lfsck2name(lfsck), rc);
@@ -428,12 +860,6 @@ static int fid_is_for_ostobj(const struct lu_env *env, struct dt_device *dt,
        if (rc == sizeof(*lma)) {
                lustre_lma_swab(lma);
 
-               /* Generally, the low layer OSD create handler or OI scrub
-                * will set the LMAC_FID_ON_OST for all external visible
-                * OST-objects. But to make the otable-based iteration to
-                * be independent from OI scrub in spite of it got failure
-                * or not, we check the LMAC_FID_ON_OST here to guarantee
-                * that the LFSCK will not repair something by wrong. */
                return lma->lma_compat & LMAC_FID_ON_OST ? 1 : 0;
        }
 
@@ -509,7 +935,10 @@ lfsck_layout_lastid_create(const struct lu_env *env,
        if (rc != 0)
                GOTO(stop, rc);
 
-       rc = dt_declare_record_write(env, obj, sizeof(lastid), pos, th);
+       rc = dt_declare_record_write(env, obj,
+                                    lfsck_buf_get(env, &lastid,
+                                                  sizeof(lastid)),
+                                    pos, th);
        if (rc != 0)
                GOTO(stop, rc);
 
@@ -629,8 +1058,11 @@ lfsck_layout_lastid_store(const struct lu_env *env,
                        continue;
                }
 
+               lastid = cpu_to_le64(lls->lls_lastid);
                rc = dt_declare_record_write(env, lls->lls_lastid_obj,
-                                            sizeof(lastid), pos, th);
+                                            lfsck_buf_get(env, &lastid,
+                                                          sizeof(lastid)),
+                                            pos, th);
                if (rc != 0)
                        goto stop;
 
@@ -638,7 +1070,6 @@ lfsck_layout_lastid_store(const struct lu_env *env,
                if (rc != 0)
                        goto stop;
 
-               lastid = cpu_to_le64(lls->lls_lastid);
                dt_write_lock(env, lls->lls_lastid_obj, 0);
                rc = dt_record_write(env, lls->lls_lastid_obj,
                                     lfsck_buf_get(env, &lastid,
@@ -734,6 +1165,17 @@ out:
        return rc;
 }
 
+static void lfsck_layout_record_failure(const struct lu_env *env,
+                                                struct lfsck_instance *lfsck,
+                                                struct lfsck_layout *lo)
+{
+       lo->ll_objs_failed_phase1++;
+       if (unlikely(lo->ll_pos_first_inconsistent == 0))
+               lo->ll_pos_first_inconsistent =
+                       lfsck->li_obj_oit->do_index_ops->dio_it.store(env,
+                                                       lfsck->li_di_oit);
+}
+
 static int lfsck_layout_master_async_interpret(const struct lu_env *env,
                                               struct ptlrpc_request *req,
                                               void *args, int rc)
@@ -750,15 +1192,17 @@ static int lfsck_layout_master_async_interpret(const struct lu_env *env,
                if (rc != 0) {
                        struct lfsck_layout *lo = com->lc_file_ram;
 
+                       CERROR("%s: fail to notify %s %x for layout start: "
+                              "rc = %d\n", lfsck_lfsck2name(com->lc_lfsck),
+                              (lr->lr_flags & LEF_TO_OST) ? "OST" : "MDT",
+                              ltd->ltd_index, rc);
                        lo->ll_flags |= LF_INCOMPLETE;
-                       lfsck_tgt_put(ltd);
                        break;
                }
 
                spin_lock(&ltds->ltd_lock);
                if (ltd->ltd_dead || ltd->ltd_layout_done) {
                        spin_unlock(&ltds->ltd_lock);
-                       lfsck_tgt_put(ltd);
                        break;
                }
 
@@ -778,17 +1222,17 @@ static int lfsck_layout_master_async_interpret(const struct lu_env *env,
                                              &llmd->llmd_mdt_phase1_list);
                }
                spin_unlock(&ltds->ltd_lock);
-               lfsck_tgt_put(ltd);
                break;
        case LE_STOP:
        case LE_PHASE1_DONE:
        case LE_PHASE2_DONE:
-               if (rc != 0)
-                       CERROR("%s: fail to notify %s %x for layout: "
-                              "event = %d, rc = %d\n",
-                              lfsck_lfsck2name(com->lc_lfsck),
-                              (lr->lr_flags & LEF_TO_OST) ? "OST" : "MDT",
-                              ltd->ltd_index, lr->lr_event, rc);
+       case LE_PEER_EXIT:
+               if (rc != 0 && rc != -EALREADY)
+                       CWARN("%s: fail to notify %s %x for layout: "
+                             "event = %d, rc = %d\n",
+                             lfsck_lfsck2name(com->lc_lfsck),
+                             (lr->lr_flags & LEF_TO_OST) ? "OST" : "MDT",
+                             ltd->ltd_index, lr->lr_event, rc);
                break;
        case LE_QUERY: {
                struct lfsck_reply *reply;
@@ -798,7 +1242,6 @@ static int lfsck_layout_master_async_interpret(const struct lu_env *env,
                        list_del_init(&ltd->ltd_layout_phase_list);
                        list_del_init(&ltd->ltd_layout_list);
                        spin_unlock(&ltds->ltd_lock);
-                       lfsck_tgt_put(ltd);
                        break;
                }
 
@@ -812,7 +1255,6 @@ static int lfsck_layout_master_async_interpret(const struct lu_env *env,
                        list_del_init(&ltd->ltd_layout_phase_list);
                        list_del_init(&ltd->ltd_layout_list);
                        spin_unlock(&ltds->ltd_lock);
-                       lfsck_tgt_put(ltd);
                        break;
                }
 
@@ -842,7 +1284,6 @@ static int lfsck_layout_master_async_interpret(const struct lu_env *env,
                        spin_unlock(&ltds->ltd_lock);
                        break;
                }
-               lfsck_tgt_put(ltd);
                break;
        }
        default:
@@ -851,7 +1292,10 @@ static int lfsck_layout_master_async_interpret(const struct lu_env *env,
                break;
        }
 
-       lfsck_component_put(env, com);
+       if (!laia->laia_shared) {
+               lfsck_tgt_put(ltd);
+               lfsck_component_put(env, com);
+       }
 
        return 0;
 }
@@ -868,7 +1312,6 @@ static int lfsck_layout_master_query_others(const struct lu_env *env,
        struct lfsck_tgt_descs            *ltds;
        struct lfsck_tgt_desc             *ltd;
        struct list_head                  *head;
-       __u32                              cnt   = 0;
        int                                rc    = 0;
        int                                rc1   = 0;
        ENTRY;
@@ -884,6 +1327,7 @@ static int lfsck_layout_master_query_others(const struct lu_env *env,
        lr->lr_active = LT_LAYOUT;
        laia->laia_com = com;
        laia->laia_lr = lr;
+       laia->laia_shared = 0;
 
        if (!list_empty(&llmd->llmd_mdt_phase1_list)) {
                ltds = &lfsck->li_mdt_descs;
@@ -922,20 +1366,15 @@ again:
                               ltd->ltd_index, rc);
                        lfsck_tgt_put(ltd);
                        rc1 = rc;
-               } else {
-                       cnt++;
                }
                spin_lock(&ltds->ltd_lock);
        }
        spin_unlock(&ltds->ltd_lock);
 
-       if (cnt > 0) {
-               rc = ptlrpc_set_wait(set);
-               if (rc < 0) {
-                       ptlrpc_set_destroy(set);
-                       RETURN(rc);
-               }
-               cnt = 0;
+       rc = ptlrpc_set_wait(set);
+       if (rc < 0) {
+               ptlrpc_set_destroy(set);
+               RETURN(rc);
        }
 
        if (!(lr->lr_flags & LEF_TO_OST) &&
@@ -957,21 +1396,20 @@ lfsck_layout_master_to_orphan(struct lfsck_layout_master_data *llmd)
 
 static int lfsck_layout_master_notify_others(const struct lu_env *env,
                                             struct lfsck_component *com,
-                                            struct lfsck_request *lr,
-                                            __u32 flags)
+                                            struct lfsck_request *lr)
 {
        struct lfsck_thread_info          *info  = lfsck_env_info(env);
        struct lfsck_async_interpret_args *laia  = &info->lti_laia;
        struct lfsck_instance             *lfsck = com->lc_lfsck;
        struct lfsck_layout_master_data   *llmd  = com->lc_data;
        struct lfsck_layout               *lo    = com->lc_file_ram;
+       struct lfsck_bookmark             *bk    = &lfsck->li_bookmark_ram;
        struct ptlrpc_request_set         *set;
        struct lfsck_tgt_descs            *ltds;
        struct lfsck_tgt_desc             *ltd;
        struct lfsck_tgt_desc             *next;
        struct list_head                  *head;
        __u32                              idx;
-       __u32                              cnt   = 0;
        int                                rc    = 0;
        ENTRY;
 
@@ -979,17 +1417,15 @@ static int lfsck_layout_master_notify_others(const struct lu_env *env,
        if (set == NULL)
                RETURN(-ENOMEM);
 
+       lr->lr_index = lfsck_dev_idx(lfsck->li_bottom);
        lr->lr_active = LT_LAYOUT;
        laia->laia_com = com;
        laia->laia_lr = lr;
-       lr->lr_flags = 0;
+       laia->laia_shared = 0;
        switch (lr->lr_event) {
        case LE_START:
-               /* Notify OSTs firstly, then other MDTs if needed. */
-               lr->lr_flags |= LEF_TO_OST;
+               /* Notify OSTs firstly, then handle other MDTs if needed. */
                ltds = &lfsck->li_ost_descs;
-
-lable1:
                laia->laia_ltds = ltds;
                down_read(&ltds->ltd_rw_sem);
                cfs_foreach_bit(ltds->ltd_tgts_bitmap, idx) {
@@ -1009,34 +1445,21 @@ lable1:
                                       "MDT", idx, rc);
                                lfsck_tgt_put(ltd);
                                lo->ll_flags |= LF_INCOMPLETE;
-                       } else {
-                               cnt++;
                        }
                }
                up_read(&ltds->ltd_rw_sem);
 
                /* Sync up */
-               if (cnt > 0) {
-                       rc = ptlrpc_set_wait(set);
-                       if (rc < 0) {
-                               ptlrpc_set_destroy(set);
-                               RETURN(rc);
-                       }
-                       cnt = 0;
+               rc = ptlrpc_set_wait(set);
+               if (rc < 0) {
+                       ptlrpc_set_destroy(set);
+                       RETURN(rc);
                }
 
-               if (!(flags & LPF_ALL_MDT))
+               if (!(bk->lb_param & LPF_ALL_TGT))
                        break;
 
-               ltds = &lfsck->li_mdt_descs;
-               /* The sponsor broadcasts the request to other MDTs. */
-               if (flags & LPF_BROADCAST) {
-                       flags &= ~LPF_ALL_MDT;
-                       lr->lr_flags &= ~LEF_TO_OST;
-                       goto lable1;
-               }
-
-               /* non-sponsors link other MDT targets locallly. */
+               /* link other MDT targets locallly. */
                spin_lock(&ltds->ltd_lock);
                cfs_foreach_bit(ltds->ltd_tgts_bitmap, idx) {
                        ltd = LTD_TGT(ltds, idx);
@@ -1051,40 +1474,37 @@ lable1:
                                      &llmd->llmd_mdt_phase1_list);
                }
                spin_unlock(&ltds->ltd_lock);
-
                break;
        case LE_STOP:
-               if (flags & LPF_BROADCAST)
-                       lr->lr_flags |= LEF_FORCE_STOP;
        case LE_PHASE2_DONE:
-               /* Notify other MDTs if needed, then the OSTs. */
-               if (flags & LPF_ALL_MDT) {
-                       /* The sponsor broadcasts the request to other MDTs. */
-                       if (flags & LPF_BROADCAST) {
-                               lr->lr_flags &= ~LEF_TO_OST;
-                               head = &llmd->llmd_mdt_list;
-                               ltds = &lfsck->li_mdt_descs;
-                               goto lable3;
-                       }
-
-                       /* non-sponsors unlink other MDT targets locallly. */
+       case LE_PEER_EXIT: {
+               /* Handle other MDTs firstly if needed, then notify the OSTs. */
+               if (bk->lb_param & LPF_ALL_TGT) {
+                       head = &llmd->llmd_mdt_list;
                        ltds = &lfsck->li_mdt_descs;
-                       spin_lock(&ltds->ltd_lock);
-                       list_for_each_entry_safe(ltd, next,
-                                                &llmd->llmd_mdt_list,
-                                                ltd_layout_list) {
-                               list_del_init(&ltd->ltd_layout_phase_list);
-                               list_del_init(&ltd->ltd_layout_list);
+                       if (lr->lr_event == LE_STOP) {
+                               /* unlink other MDT targets locallly. */
+                               spin_lock(&ltds->ltd_lock);
+                               list_for_each_entry_safe(ltd, next, head,
+                                                        ltd_layout_list) {
+                                       list_del_init(&ltd->ltd_layout_phase_list);
+                                       list_del_init(&ltd->ltd_layout_list);
+                               }
+                               spin_unlock(&ltds->ltd_lock);
+
+                               lr->lr_flags |= LEF_TO_OST;
+                               head = &llmd->llmd_ost_list;
+                               ltds = &lfsck->li_ost_descs;
+                       } else {
+                               lr->lr_flags &= ~LEF_TO_OST;
                        }
-                       spin_unlock(&ltds->ltd_lock);
+               } else {
+                       lr->lr_flags |= LEF_TO_OST;
+                       head = &llmd->llmd_ost_list;
+                       ltds = &lfsck->li_ost_descs;
                }
 
-lable2:
-               lr->lr_flags |= LEF_TO_OST;
-               head = &llmd->llmd_ost_list;
-               ltds = &lfsck->li_ost_descs;
-
-lable3:
+again:
                laia->laia_ltds = ltds;
                spin_lock(&ltds->ltd_lock);
                while (!list_empty(head)) {
@@ -1093,41 +1513,40 @@ lable3:
                        if (!list_empty(&ltd->ltd_layout_phase_list))
                                list_del_init(&ltd->ltd_layout_phase_list);
                        list_del_init(&ltd->ltd_layout_list);
+                       atomic_inc(&ltd->ltd_ref);
                        laia->laia_ltd = ltd;
                        spin_unlock(&ltds->ltd_lock);
                        rc = lfsck_async_request(env, ltd->ltd_exp, lr, set,
                                        lfsck_layout_master_async_interpret,
                                        laia, LFSCK_NOTIFY);
-                       if (rc != 0)
+                       if (rc != 0) {
                                CERROR("%s: fail to notify %s %x for layout "
                                       "stop/phase2: rc = %d\n",
                                       lfsck_lfsck2name(lfsck),
                                       (lr->lr_flags & LEF_TO_OST) ? "OST" :
                                       "MDT", ltd->ltd_index, rc);
-                       else
-                               cnt++;
+                               lfsck_tgt_put(ltd);
+                       }
                        spin_lock(&ltds->ltd_lock);
                }
                spin_unlock(&ltds->ltd_lock);
 
-               if (!(flags & LPF_BROADCAST))
-                       break;
-
-               /* Sync up */
-               if (cnt > 0) {
-                       rc = ptlrpc_set_wait(set);
-                       if (rc < 0) {
-                               ptlrpc_set_destroy(set);
-                               RETURN(rc);
-                       }
-                       cnt = 0;
+               rc = ptlrpc_set_wait(set);
+               if (rc < 0) {
+                       ptlrpc_set_destroy(set);
+                       RETURN(rc);
                }
 
-               flags &= ~LPF_BROADCAST;
-               goto lable2;
+               if (!(lr->lr_flags & LEF_TO_OST)) {
+                       lr->lr_flags |= LEF_TO_OST;
+                       head = &llmd->llmd_ost_list;
+                       ltds = &lfsck->li_ost_descs;
+                       goto again;
+               }
+               break;
+       }
        case LE_PHASE1_DONE:
                llmd->llmd_touch_gen++;
-               lr->lr_flags &= ~LEF_TO_OST;
                ltds = &lfsck->li_mdt_descs;
                laia->laia_ltds = ltds;
                spin_lock(&ltds->ltd_lock);
@@ -1142,18 +1561,19 @@ lable3:
                        list_del_init(&ltd->ltd_layout_phase_list);
                        list_add_tail(&ltd->ltd_layout_phase_list,
                                      &llmd->llmd_mdt_phase1_list);
+                       atomic_inc(&ltd->ltd_ref);
                        laia->laia_ltd = ltd;
                        spin_unlock(&ltds->ltd_lock);
                        rc = lfsck_async_request(env, ltd->ltd_exp, lr, set,
                                        lfsck_layout_master_async_interpret,
                                        laia, LFSCK_NOTIFY);
-                       if (rc != 0)
+                       if (rc != 0) {
                                CERROR("%s: fail to notify MDT %x for layout "
                                       "phase1 done: rc = %d\n",
                                       lfsck_lfsck2name(lfsck),
                                       ltd->ltd_index, rc);
-                       else
-                               cnt++;
+                               lfsck_tgt_put(ltd);
+                       }
                        spin_lock(&ltds->ltd_lock);
                }
                spin_unlock(&ltds->ltd_lock);
@@ -1165,14 +1585,9 @@ lable3:
                break;
        }
 
-       if (cnt > 0)
-               rc = ptlrpc_set_wait(set);
+       rc = ptlrpc_set_wait(set);
        ptlrpc_set_destroy(set);
 
-       if (rc == 0 && lr->lr_event == LE_START &&
-           list_empty(&llmd->llmd_ost_list))
-               rc = -ENODEV;
-
        RETURN(rc);
 }
 
@@ -1185,7 +1600,6 @@ static int lfsck_layout_double_scan_result(const struct lu_env *env,
        struct lfsck_bookmark   *bk    = &lfsck->li_bookmark_ram;
 
        down_write(&com->lc_sem);
-
        lo->ll_run_time_phase2 += cfs_duration_sec(cfs_time_current() +
                                HALF_SEC - lfsck->li_time_last_checkpoint);
        lo->ll_time_last_checkpoint = cfs_time_current_sec();
@@ -1209,27 +1623,1817 @@ static int lfsck_layout_double_scan_result(const struct lu_env *env,
                lo->ll_status = LS_FAILED;
        }
 
-       if (lo->ll_status != LS_PAUSED) {
-               spin_lock(&lfsck->li_lock);
-               list_del_init(&com->lc_link);
-               list_add_tail(&com->lc_link, &lfsck->li_list_idle);
-               spin_unlock(&lfsck->li_lock);
-       }
-
        rc = lfsck_layout_store(env, com);
-
        up_write(&com->lc_sem);
 
        return rc;
 }
 
-static int lfsck_layout_scan_orphan(const struct lu_env *env,
-                                   struct lfsck_component *com,
-                                   struct lfsck_tgt_desc *ltd)
+static int lfsck_layout_lock(const struct lu_env *env,
+                            struct lfsck_component *com,
+                            struct dt_object *obj,
+                            struct lustre_handle *lh, __u64 bits)
 {
-       /* XXX: To be extended in other patch. */
-
-       return 0;
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       ldlm_policy_data_t              *policy = &info->lti_policy;
+       struct ldlm_res_id              *resid  = &info->lti_resid;
+       struct lfsck_instance           *lfsck  = com->lc_lfsck;
+       __u64                            flags  = LDLM_FL_ATOMIC_CB;
+       int                              rc;
+
+       LASSERT(lfsck->li_namespace != NULL);
+
+       memset(policy, 0, sizeof(*policy));
+       policy->l_inodebits.bits = bits;
+       fid_build_reg_res_name(lfsck_dto2fid(obj), resid);
+       rc = ldlm_cli_enqueue_local(lfsck->li_namespace, resid, LDLM_IBITS,
+                                   policy, LCK_EX, &flags, ldlm_blocking_ast,
+                                   ldlm_completion_ast, NULL, NULL, 0,
+                                   LVB_T_NONE, NULL, lh);
+       if (rc == ELDLM_OK) {
+               rc = 0;
+       } else {
+               memset(lh, 0, sizeof(*lh));
+               rc = -EIO;
+       }
+
+       return rc;
+}
+
+static void lfsck_layout_unlock(struct lustre_handle *lh)
+{
+       if (lustre_handle_is_used(lh)) {
+               ldlm_lock_decref(lh, LCK_EX);
+               memset(lh, 0, sizeof(*lh));
+       }
+}
+
+static int lfsck_layout_trans_stop(const struct lu_env *env,
+                                  struct dt_device *dev,
+                                  struct thandle *handle, int result)
+{
+       int rc;
+
+       handle->th_result = result;
+       rc = dt_trans_stop(env, dev, handle);
+       if (rc > 0)
+               rc = 0;
+       else if (rc == 0)
+               rc = 1;
+
+       return rc;
+}
+
+/**
+ * Get the system default stripe size.
+ *
+ * \param[in] env      pointer to the thread context
+ * \param[in] lfsck    pointer to the lfsck instance
+ * \param[out] size    pointer to the default stripe size
+ *
+ * \retval             0 for success
+ * \retval             negative error number on failure
+ */
+static int lfsck_layout_get_def_stripesize(const struct lu_env *env,
+                                          struct lfsck_instance *lfsck,
+                                          __u32 *size)
+{
+       struct lov_user_md      *lum = &lfsck_env_info(env)->lti_lum;
+       struct dt_object        *root;
+       int                      rc;
+
+       root = dt_locate(env, lfsck->li_next, &lfsck->li_local_root_fid);
+       if (IS_ERR(root))
+               return PTR_ERR(root);
+
+       /* Get the default stripe size via xattr_get on the backend root. */
+       rc = dt_xattr_get(env, root, lfsck_buf_get(env, lum, sizeof(*lum)),
+                         XATTR_NAME_LOV, BYPASS_CAPA);
+       if (rc > 0) {
+               /* The lum->lmm_stripe_size is LE mode. The *size also
+                * should be LE mode. So it is unnecessary to convert. */
+               *size = lum->lmm_stripe_size;
+               rc = 0;
+       } else if (unlikely(rc == 0)) {
+               rc = -EINVAL;
+       }
+
+       lfsck_object_put(env, root);
+
+       return rc;
+}
+
+/**
+ * \retval      +1: repaired
+ * \retval       0: did nothing
+ * \retval     -ve: on error
+ */
+static int lfsck_layout_refill_lovea(const struct lu_env *env,
+                                    struct thandle *handle,
+                                    struct dt_object *parent,
+                                    struct lu_fid *cfid,
+                                    struct lu_buf *buf,
+                                    struct lov_ost_data_v1 *slot,
+                                    int fl, __u32 ost_idx)
+{
+       struct ost_id           *oi     = &lfsck_env_info(env)->lti_oi;
+       struct lov_mds_md_v1    *lmm    = buf->lb_buf;
+       int                      rc;
+
+       fid_to_ostid(cfid, oi);
+       ostid_cpu_to_le(oi, &slot->l_ost_oi);
+       slot->l_ost_gen = cpu_to_le32(0);
+       slot->l_ost_idx = cpu_to_le32(ost_idx);
+
+       if (le32_to_cpu(lmm->lmm_pattern) & LOV_PATTERN_F_HOLE) {
+               struct lov_ost_data_v1 *objs;
+               int                     i;
+               __u16                   count;
+
+               count = le16_to_cpu(lmm->lmm_stripe_count);
+               if (le32_to_cpu(lmm->lmm_magic) == LOV_MAGIC_V1)
+                       objs = &lmm->lmm_objects[0];
+               else
+                       objs = &((struct lov_mds_md_v3 *)lmm)->lmm_objects[0];
+               for (i = 0; i < count; i++, objs++) {
+                       if (objs != slot && lovea_slot_is_dummy(objs))
+                               break;
+               }
+
+               /* If the @slot is the last dummy slot to be refilled,
+                * then drop LOV_PATTERN_F_HOLE from lmm::lmm_pattern. */
+               if (i == count)
+                       lmm->lmm_pattern &= ~cpu_to_le32(LOV_PATTERN_F_HOLE);
+       }
+
+       rc = dt_xattr_set(env, parent, buf, XATTR_NAME_LOV, fl, handle,
+                         BYPASS_CAPA);
+       if (rc == 0)
+               rc = 1;
+
+       return rc;
+}
+
+/**
+ * \retval      +1: repaired
+ * \retval       0: did nothing
+ * \retval     -ve: on error
+ */
+static int lfsck_layout_extend_lovea(const struct lu_env *env,
+                                    struct lfsck_instance *lfsck,
+                                    struct thandle *handle,
+                                    struct dt_object *parent,
+                                    struct lu_fid *cfid,
+                                    struct lu_buf *buf, int fl,
+                                    __u32 ost_idx, __u32 ea_off, bool reset)
+{
+       struct lov_mds_md_v1    *lmm    = buf->lb_buf;
+       struct lov_ost_data_v1  *objs;
+       int                      rc;
+       __u16                    count;
+       ENTRY;
+
+       if (fl == LU_XATTR_CREATE || reset) {
+               __u32 pattern = LOV_PATTERN_RAID0;
+
+               count = ea_off + 1;
+               LASSERT(buf->lb_len == lov_mds_md_size(count, LOV_MAGIC_V1));
+
+               if (ea_off != 0 || reset)
+                       pattern |= LOV_PATTERN_F_HOLE;
+
+               memset(lmm, 0, buf->lb_len);
+               lmm->lmm_magic = cpu_to_le32(LOV_MAGIC_V1);
+               lmm->lmm_pattern = cpu_to_le32(pattern);
+               fid_to_lmm_oi(lfsck_dto2fid(parent), &lmm->lmm_oi);
+               lmm_oi_cpu_to_le(&lmm->lmm_oi, &lmm->lmm_oi);
+
+               rc = lfsck_layout_get_def_stripesize(env, lfsck,
+                                                    &lmm->lmm_stripe_size);
+               if (rc != 0)
+                       RETURN(rc);
+
+               objs = &lmm->lmm_objects[ea_off];
+       } else {
+               __u32   magic = le32_to_cpu(lmm->lmm_magic);
+               int     gap;
+
+               count = le16_to_cpu(lmm->lmm_stripe_count);
+               if (magic == LOV_MAGIC_V1)
+                       objs = &lmm->lmm_objects[count];
+               else
+                       objs = &((struct lov_mds_md_v3 *)lmm)->
+                                                       lmm_objects[count];
+
+               gap = ea_off - count;
+               if (gap >= 0)
+                       count = ea_off + 1;
+               LASSERT(buf->lb_len == lov_mds_md_size(count, magic));
+
+               if (gap > 0) {
+                       memset(objs, 0, gap * sizeof(*objs));
+                       lmm->lmm_pattern |= cpu_to_le32(LOV_PATTERN_F_HOLE);
+               }
+
+               lmm->lmm_layout_gen =
+                           cpu_to_le16(le16_to_cpu(lmm->lmm_layout_gen) + 1);
+               objs += gap;
+       }
+
+       lmm->lmm_stripe_count = cpu_to_le16(count);
+       rc = lfsck_layout_refill_lovea(env, handle, parent, cfid, buf, objs,
+                                      fl, ost_idx);
+
+       RETURN(rc);
+}
+
+/**
+ * \retval      +1: repaired
+ * \retval       0: did nothing
+ * \retval     -ve: on error
+ */
+static int lfsck_layout_update_pfid(const struct lu_env *env,
+                                   struct lfsck_component *com,
+                                   struct dt_object *parent,
+                                   struct lu_fid *cfid,
+                                   struct dt_device *cdev, __u32 ea_off)
+{
+       struct filter_fid       *pfid   = &lfsck_env_info(env)->lti_new_pfid;
+       struct dt_object        *child;
+       struct thandle          *handle;
+       const struct lu_fid     *tfid   = lu_object_fid(&parent->do_lu);
+       struct lu_buf           *buf;
+       int                      rc     = 0;
+       ENTRY;
+
+       child = lfsck_object_find_by_dev(env, cdev, cfid);
+       if (IS_ERR(child))
+               RETURN(PTR_ERR(child));
+
+       handle = dt_trans_create(env, cdev);
+       if (IS_ERR(handle))
+               GOTO(out, rc = PTR_ERR(handle));
+
+       pfid->ff_parent.f_seq = cpu_to_le64(tfid->f_seq);
+       pfid->ff_parent.f_oid = cpu_to_le32(tfid->f_oid);
+       /* Currently, the filter_fid::ff_parent::f_ver is not the real parent
+        * MDT-object's FID::f_ver, instead it is the OST-object index in its
+        * parent MDT-object's layout EA. */
+       pfid->ff_parent.f_stripe_idx = cpu_to_le32(ea_off);
+       buf = lfsck_buf_get(env, pfid, sizeof(struct filter_fid));
+
+       rc = dt_declare_xattr_set(env, child, buf, XATTR_NAME_FID, 0, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_trans_start(env, cdev, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_xattr_set(env, child, buf, XATTR_NAME_FID, 0, handle,
+                         BYPASS_CAPA);
+
+       GOTO(stop, rc = (rc == 0 ? 1 : rc));
+
+stop:
+       dt_trans_stop(env, cdev, handle);
+
+out:
+       lu_object_put(env, &child->do_lu);
+
+       return rc;
+}
+
+/**
+ * \retval      +1: repaired
+ * \retval       0: did nothing
+ * \retval     -ve: on error
+ */
+static int lfsck_layout_recreate_parent(const struct lu_env *env,
+                                       struct lfsck_component *com,
+                                       struct lfsck_tgt_desc *ltd,
+                                       struct lu_orphan_rec *rec,
+                                       struct lu_fid *cfid,
+                                       const char *prefix,
+                                       const char *postfix,
+                                       __u32 ea_off)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       char                            *name   = info->lti_key;
+       struct lu_attr                  *la     = &info->lti_la;
+       struct dt_object_format         *dof    = &info->lti_dof;
+       struct lfsck_instance           *lfsck  = com->lc_lfsck;
+       struct lu_fid                   *pfid   = &rec->lor_fid;
+       struct lu_fid                   *tfid   = &info->lti_fid3;
+       struct dt_device                *next   = lfsck->li_next;
+       struct dt_object                *pobj   = NULL;
+       struct dt_object                *cobj   = NULL;
+       struct thandle                  *th     = NULL;
+       struct lu_buf                   *pbuf   = NULL;
+       struct lu_buf                   *ea_buf = &info->lti_big_buf;
+       struct lustre_handle             lh     = { 0 };
+       int                              buflen = ea_buf->lb_len;
+       int                              idx    = 0;
+       int                              rc     = 0;
+       ENTRY;
+
+       /* Create .lustre/lost+found/MDTxxxx when needed. */
+       if (unlikely(lfsck->li_lpf_obj == NULL)) {
+               rc = lfsck_create_lpf(env, lfsck);
+               if (rc != 0)
+                       RETURN(rc);
+       }
+
+       if (fid_is_zero(pfid)) {
+               struct filter_fid *ff = &info->lti_new_pfid;
+
+               rc = lfsck_fid_alloc(env, lfsck, pfid, false);
+               if (rc != 0)
+                       RETURN(rc);
+
+               ff->ff_parent.f_seq = cpu_to_le64(pfid->f_seq);
+               ff->ff_parent.f_oid = cpu_to_le32(pfid->f_oid);
+               /* Currently, the filter_fid::ff_parent::f_ver is not the
+                * real parent MDT-object's FID::f_ver, instead it is the
+                * OST-object index in its parent MDT-object's layout EA. */
+               ff->ff_parent.f_stripe_idx = cpu_to_le32(ea_off);
+               pbuf = lfsck_buf_get(env, ff, sizeof(struct filter_fid));
+               cobj = lfsck_object_find_by_dev(env, ltd->ltd_tgt, cfid);
+               if (IS_ERR(cobj))
+                       RETURN(PTR_ERR(cobj));
+       }
+
+       CDEBUG(D_LFSCK, "Re-create the lost MDT-object: parent "
+              DFID", child "DFID", OST-index %u, stripe-index %u, "
+              "prefix %s, postfix %s\n",
+              PFID(pfid), PFID(cfid), ltd->ltd_index, ea_off, prefix, postfix);
+
+       pobj = lfsck_object_find_by_dev(env, lfsck->li_bottom, pfid);
+       if (IS_ERR(pobj))
+               GOTO(put, rc = PTR_ERR(pobj));
+
+       LASSERT(prefix != NULL);
+       LASSERT(postfix != NULL);
+
+       /** name rules:
+        *
+        *  1. Use the MDT-object's FID as the name with prefix and postfix.
+        *
+        *  1.1 prefix "C-":    More than one OST-objects claim the same
+        *                      MDT-object and the same slot in the layout EA.
+        *                      It may be created for dangling referenced MDT
+        *                      object or may be not.
+        *  1.2 prefix "N-":    The orphan OST-object does not know which one
+        *                      is the real parent, so the LFSCK assign a new
+        *                      FID as its parent.
+        *  1.3 prefix "R-":    The orphan OST-object know its parent FID but
+        *                      does not know the position in the namespace.
+        *
+        *  2. If there is name conflict, append more index for new name. */
+       sprintf(name, "%s"DFID"%s", prefix, PFID(pfid), postfix);
+       do {
+               rc = dt_lookup(env, lfsck->li_lpf_obj, (struct dt_rec *)tfid,
+                              (const struct dt_key *)name, BYPASS_CAPA);
+               if (rc != 0 && rc != -ENOENT)
+                       GOTO(put, rc);
+
+               if (unlikely(rc == 0)) {
+                       CWARN("%s: The name %s under lost+found has been used "
+                             "by the "DFID". Try to increase the FID version "
+                             "for the new file name.\n",
+                             lfsck_lfsck2name(lfsck), name, PFID(tfid));
+                       sprintf(name, "%s"DFID"%s-%d", prefix, PFID(pfid),
+                               postfix, ++idx);
+               }
+       } while (rc == 0);
+
+       memset(la, 0, sizeof(*la));
+       la->la_uid = rec->lor_uid;
+       la->la_gid = rec->lor_gid;
+       la->la_mode = S_IFREG | S_IRUSR;
+       la->la_valid = LA_MODE | LA_UID | LA_GID;
+
+       memset(dof, 0, sizeof(*dof));
+       dof->dof_type = dt_mode_to_dft(S_IFREG);
+
+       rc = lov_mds_md_size(ea_off + 1, LOV_MAGIC_V1);
+       if (buflen < rc) {
+               lu_buf_realloc(ea_buf, rc);
+               buflen = ea_buf->lb_len;
+               if (ea_buf->lb_buf == NULL)
+                       GOTO(put, rc = -ENOMEM);
+       } else {
+               ea_buf->lb_len = rc;
+       }
+
+       /* Hold update lock on the .lustre/lost+found/MDTxxxx/.
+        *
+        * XXX: Currently, we do not grab the PDO lock as normal create cases,
+        *      because creating MDT-object for orphan OST-object is rare, we
+        *      do not much care about the performance. It can be improved in
+        *      the future when needed. */
+       rc = lfsck_layout_lock(env, com, lfsck->li_lpf_obj, &lh,
+                              MDS_INODELOCK_UPDATE);
+       if (rc != 0)
+               GOTO(put, rc);
+
+       th = dt_trans_create(env, next);
+       if (IS_ERR(th))
+               GOTO(unlock, rc = PTR_ERR(th));
+
+       /* 1a. Update OST-object's parent information remotely.
+        *
+        * If other subsequent modifications failed, then next LFSCK scanning
+        * will process the OST-object as orphan again with known parent FID. */
+       if (cobj != NULL) {
+               rc = dt_declare_xattr_set(env, cobj, pbuf, XATTR_NAME_FID, 0, th);
+               if (rc != 0)
+                       GOTO(stop, rc);
+       }
+
+       /* 2a. Create the MDT-object locally. */
+       rc = dt_declare_create(env, pobj, la, NULL, dof, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       /* 3a. Add layout EA for the MDT-object. */
+       rc = dt_declare_xattr_set(env, pobj, ea_buf, XATTR_NAME_LOV,
+                                 LU_XATTR_CREATE, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       /* 4a. Insert the MDT-object to .lustre/lost+found/MDTxxxx/ */
+       rc = dt_declare_insert(env, lfsck->li_lpf_obj,
+                              (const struct dt_rec *)pfid,
+                              (const struct dt_key *)name, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_trans_start(env, next, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       /* 1b. Update OST-object's parent information remotely. */
+       if (cobj != NULL) {
+               rc = dt_xattr_set(env, cobj, pbuf, XATTR_NAME_FID, 0, th,
+                                 BYPASS_CAPA);
+               if (rc != 0)
+                       GOTO(stop, rc);
+       }
+
+       dt_write_lock(env, pobj, 0);
+       /* 2b. Create the MDT-object locally. */
+       rc = dt_create(env, pobj, la, NULL, dof, th);
+       if (rc == 0)
+               /* 3b. Add layout EA for the MDT-object. */
+               rc = lfsck_layout_extend_lovea(env, lfsck, th, pobj, cfid,
+                                              ea_buf, LU_XATTR_CREATE,
+                                              ltd->ltd_index, ea_off, false);
+       dt_write_unlock(env, pobj);
+       if (rc < 0)
+               GOTO(stop, rc);
+
+       /* 4b. Insert the MDT-object to .lustre/lost+found/MDTxxxx/ */
+       rc = dt_insert(env, lfsck->li_lpf_obj,
+                      (const struct dt_rec *)pfid,
+                      (const struct dt_key *)name, th, BYPASS_CAPA, 1);
+
+       GOTO(stop, rc);
+
+stop:
+       dt_trans_stop(env, next, th);
+
+unlock:
+       lfsck_layout_unlock(&lh);
+
+put:
+       if (cobj != NULL && !IS_ERR(cobj))
+               lu_object_put(env, &cobj->do_lu);
+       if (pobj != NULL && !IS_ERR(pobj))
+               lu_object_put(env, &pobj->do_lu);
+       ea_buf->lb_len = buflen;
+
+       return rc >= 0 ? 1 : rc;
+}
+
+static int lfsck_layout_master_conditional_destroy(const struct lu_env *env,
+                                                  struct lfsck_component *com,
+                                                  const struct lu_fid *fid,
+                                                  __u32 index)
+{
+       struct lfsck_thread_info *info  = lfsck_env_info(env);
+       struct lfsck_request     *lr    = &info->lti_lr;
+       struct lfsck_instance    *lfsck = com->lc_lfsck;
+       struct lfsck_tgt_desc    *ltd;
+       struct ptlrpc_request    *req;
+       struct lfsck_request     *tmp;
+       struct obd_export        *exp;
+       int                       rc    = 0;
+       ENTRY;
+
+       ltd = lfsck_tgt_get(&lfsck->li_ost_descs, index);
+       if (unlikely(ltd == NULL))
+               RETURN(-ENXIO);
+
+       exp = ltd->ltd_exp;
+       if (!(exp_connect_flags(exp) & OBD_CONNECT_LFSCK))
+               GOTO(put, rc = -EOPNOTSUPP);
+
+       req = ptlrpc_request_alloc(class_exp2cliimp(exp), &RQF_LFSCK_NOTIFY);
+       if (req == NULL)
+               GOTO(put, rc = -ENOMEM);
+
+       rc = ptlrpc_request_pack(req, LUSTRE_OBD_VERSION, LFSCK_NOTIFY);
+       if (rc != 0) {
+               ptlrpc_request_free(req);
+
+               GOTO(put, rc);
+       }
+
+       memset(lr, 0, sizeof(*lr));
+       lr->lr_event = LE_CONDITIONAL_DESTROY;
+       lr->lr_active = LT_LAYOUT;
+       lr->lr_fid = *fid;
+
+       tmp = req_capsule_client_get(&req->rq_pill, &RMF_LFSCK_REQUEST);
+       *tmp = *lr;
+       ptlrpc_request_set_replen(req);
+
+       rc = ptlrpc_queue_wait(req);
+       ptlrpc_req_finished(req);
+
+       GOTO(put, rc);
+
+put:
+       lfsck_tgt_put(ltd);
+
+       return rc;
+}
+
+static int lfsck_layout_slave_conditional_destroy(const struct lu_env *env,
+                                                 struct lfsck_component *com,
+                                                 struct lfsck_request *lr)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct lu_attr                  *la     = &info->lti_la;
+       ldlm_policy_data_t              *policy = &info->lti_policy;
+       struct ldlm_res_id              *resid  = &info->lti_resid;
+       struct lfsck_instance           *lfsck  = com->lc_lfsck;
+       struct dt_device                *dev    = lfsck->li_bottom;
+       struct lu_fid                   *fid    = &lr->lr_fid;
+       struct dt_object                *obj;
+       struct thandle                  *th     = NULL;
+       struct lustre_handle             lh     = { 0 };
+       __u64                            flags  = 0;
+       int                              rc     = 0;
+       ENTRY;
+
+       obj = lfsck_object_find_by_dev(env, dev, fid);
+       if (IS_ERR(obj))
+               RETURN(PTR_ERR(obj));
+
+       dt_read_lock(env, obj, 0);
+       if (dt_object_exists(obj) == 0) {
+               dt_read_unlock(env, obj);
+
+               GOTO(put, rc = -ENOENT);
+       }
+
+       /* Get obj's attr without lock firstly. */
+       rc = dt_attr_get(env, obj, la, BYPASS_CAPA);
+       dt_read_unlock(env, obj);
+       if (rc != 0)
+               GOTO(put, rc);
+
+       if (likely(la->la_ctime != 0 || la->la_mode & S_ISUID))
+               GOTO(put, rc = -ETXTBSY);
+
+       /* Acquire extent lock on [0, EOF] to sync with all possible written. */
+       LASSERT(lfsck->li_namespace != NULL);
+
+       memset(policy, 0, sizeof(*policy));
+       policy->l_extent.end = OBD_OBJECT_EOF;
+       ost_fid_build_resid(fid, resid);
+       rc = ldlm_cli_enqueue_local(lfsck->li_namespace, resid, LDLM_EXTENT,
+                                   policy, LCK_EX, &flags, ldlm_blocking_ast,
+                                   ldlm_completion_ast, NULL, NULL, 0,
+                                   LVB_T_NONE, NULL, &lh);
+       if (rc != ELDLM_OK)
+               GOTO(put, rc = -EIO);
+
+       dt_write_lock(env, obj, 0);
+       /* Get obj's attr within lock again. */
+       rc = dt_attr_get(env, obj, la, BYPASS_CAPA);
+       if (rc != 0)
+               GOTO(unlock, rc);
+
+       if (la->la_ctime != 0)
+               GOTO(unlock, rc = -ETXTBSY);
+
+       th = dt_trans_create(env, dev);
+       if (IS_ERR(th))
+               GOTO(unlock, rc = PTR_ERR(th));
+
+       rc = dt_declare_ref_del(env, obj, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_declare_destroy(env, obj, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_trans_start_local(env, dev, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_ref_del(env, obj, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_destroy(env, obj, th);
+       if (rc == 0)
+               CDEBUG(D_LFSCK, "Destroy the empty OST-object "DFID" which "
+                      "was created for reparing dangling referenced case. "
+                      "But the original missed OST-object is found now.\n",
+                      PFID(fid));
+
+       GOTO(stop, rc);
+
+stop:
+       dt_trans_stop(env, dev, th);
+
+unlock:
+       dt_write_unlock(env, obj);
+       ldlm_lock_decref(&lh, LCK_EX);
+
+put:
+       lu_object_put(env, &obj->do_lu);
+
+       return rc;
+}
+
+/**
+ * Some OST-object has occupied the specified layout EA slot.
+ * Such OST-object may be generated by the LFSCK when repair
+ * dangling referenced MDT-object, which can be indicated by
+ * attr::la_ctime == 0 but without S_ISUID in la_mode. If it
+ * is true and such OST-object has not been modified yet, we
+ * will replace it with the orphan OST-object; otherwise the
+ * LFSCK will create new MDT-object to reference the orphan.
+ *
+ * \retval      +1: repaired
+ * \retval       0: did nothing
+ * \retval     -ve: on error
+ */
+static int lfsck_layout_conflict_create(const struct lu_env *env,
+                                       struct lfsck_component *com,
+                                       struct lfsck_tgt_desc *ltd,
+                                       struct lu_orphan_rec *rec,
+                                       struct dt_object *parent,
+                                       struct lu_fid *cfid,
+                                       struct lu_buf *ea_buf,
+                                       struct lov_ost_data_v1 *slot,
+                                       __u32 ea_off, __u32 ori_len)
+{
+       struct lfsck_thread_info *info          = lfsck_env_info(env);
+       struct lu_fid            *cfid2         = &info->lti_fid2;
+       struct ost_id            *oi            = &info->lti_oi;
+       char                     *postfix       = info->lti_tmpbuf;
+       struct lov_mds_md_v1     *lmm           = ea_buf->lb_buf;
+       struct dt_device         *dev           = com->lc_lfsck->li_bottom;
+       struct thandle           *th            = NULL;
+       struct lustre_handle      lh            = { 0 };
+       __u32                     ost_idx2      = le32_to_cpu(slot->l_ost_idx);
+       int                       rc            = 0;
+       ENTRY;
+
+       ostid_le_to_cpu(&slot->l_ost_oi, oi);
+       ostid_to_fid(cfid2, oi, ost_idx2);
+
+       CDEBUG(D_LFSCK, "Handle layout EA conflict: parent "DFID
+              ", cur-child "DFID" on the OST %u, orphan-child "
+              DFID" on the OST %u, stripe-index %u\n",
+              PFID(lfsck_dto2fid(parent)), PFID(cfid2), ost_idx2,
+              PFID(cfid), ltd->ltd_index, ea_off);
+
+       /* Hold layout lock on the parent to prevent others to access. */
+       rc = lfsck_layout_lock(env, com, parent, &lh,
+                              MDS_INODELOCK_LAYOUT | MDS_INODELOCK_XATTR);
+       if (rc != 0)
+               GOTO(out, rc);
+
+       rc = lfsck_layout_master_conditional_destroy(env, com, cfid2, ost_idx2);
+
+       /* If the conflict OST-obejct is not created for fixing dangling
+        * referenced MDT-object in former LFSCK check/repair, or it has
+        * been modified by others, then we cannot destroy it. Re-create
+        * a new MDT-object for the orphan OST-object. */
+       if (rc == -ETXTBSY) {
+               /* No need the layout lock on the original parent. */
+               lfsck_layout_unlock(&lh);
+               ea_buf->lb_len = ori_len;
+
+               fid_zero(&rec->lor_fid);
+               snprintf(postfix, LFSCK_TMPBUF_LEN, "-"DFID"-%x",
+                        PFID(lu_object_fid(&parent->do_lu)), ea_off);
+               rc = lfsck_layout_recreate_parent(env, com, ltd, rec, cfid,
+                                                 "C-", postfix, ea_off);
+
+               RETURN(rc);
+       }
+
+       if (rc != 0 && rc != -ENOENT)
+               GOTO(unlock, rc);
+
+       th = dt_trans_create(env, dev);
+       if (IS_ERR(th))
+               GOTO(unlock, rc = PTR_ERR(th));
+
+       rc = dt_declare_xattr_set(env, parent, ea_buf, XATTR_NAME_LOV,
+                                 LU_XATTR_REPLACE, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_trans_start_local(env, dev, th);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       dt_write_lock(env, parent, 0);
+       lmm->lmm_layout_gen = cpu_to_le16(le16_to_cpu(lmm->lmm_layout_gen) + 1);
+       rc = lfsck_layout_refill_lovea(env, th, parent, cfid, ea_buf, slot,
+                                      LU_XATTR_REPLACE, ltd->ltd_index);
+       dt_write_unlock(env, parent);
+
+       GOTO(stop, rc);
+
+stop:
+       dt_trans_stop(env, dev, th);
+
+unlock:
+       lfsck_layout_unlock(&lh);
+
+out:
+       ea_buf->lb_len = ori_len;
+
+       return rc >= 0 ? 1 : rc;
+}
+
+/**
+ * \retval      +1: repaired
+ * \retval       0: did nothing
+ * \retval     -ve: on error
+ */
+static int lfsck_layout_recreate_lovea(const struct lu_env *env,
+                                      struct lfsck_component *com,
+                                      struct lfsck_tgt_desc *ltd,
+                                      struct lu_orphan_rec *rec,
+                                      struct dt_object *parent,
+                                      struct lu_fid *cfid,
+                                      __u32 ost_idx, __u32 ea_off)
+{
+       struct lfsck_thread_info *info          = lfsck_env_info(env);
+       struct lu_buf            *buf           = &info->lti_big_buf;
+       struct lu_fid            *fid           = &info->lti_fid2;
+       struct ost_id            *oi            = &info->lti_oi;
+       struct lfsck_instance    *lfsck         = com->lc_lfsck;
+       struct dt_device         *dt            = lfsck->li_bottom;
+       struct lfsck_bookmark    *bk            = &lfsck->li_bookmark_ram;
+       struct thandle            *handle       = NULL;
+       size_t                    buflen        = buf->lb_len;
+       struct lov_mds_md_v1     *lmm;
+       struct lov_ost_data_v1   *objs;
+       struct lustre_handle      lh            = { 0 };
+       __u32                     magic;
+       int                       fl            = 0;
+       int                       rc            = 0;
+       int                       rc1;
+       int                       i;
+       __u16                     count;
+       bool                      locked        = false;
+       ENTRY;
+
+       CDEBUG(D_LFSCK, "Re-create the crashed layout EA: parent "
+              DFID", child "DFID", OST-index %u, stripe-index %u\n",
+              PFID(lfsck_dto2fid(parent)), PFID(cfid), ost_idx, ea_off);
+
+       rc = lfsck_layout_lock(env, com, parent, &lh,
+                              MDS_INODELOCK_LAYOUT | MDS_INODELOCK_XATTR);
+       if (rc != 0)
+               RETURN(rc);
+
+again:
+       if (locked) {
+               dt_write_unlock(env, parent);
+               locked = false;
+       }
+
+       if (handle != NULL) {
+               dt_trans_stop(env, dt, handle);
+               handle = NULL;
+       }
+
+       if (rc < 0)
+               GOTO(unlock_layout, rc);
+
+       if (buf->lb_len < rc) {
+               lu_buf_realloc(buf, rc);
+               buflen = buf->lb_len;
+               if (buf->lb_buf == NULL)
+                       GOTO(unlock_layout, rc = -ENOMEM);
+       }
+
+       if (!(bk->lb_param & LPF_DRYRUN)) {
+               handle = dt_trans_create(env, dt);
+               if (IS_ERR(handle))
+                       GOTO(unlock_layout, rc = PTR_ERR(handle));
+
+               rc = dt_declare_xattr_set(env, parent, buf, XATTR_NAME_LOV,
+                                         fl, handle);
+               if (rc != 0)
+                       GOTO(stop, rc);
+
+               rc = dt_trans_start_local(env, dt, handle);
+               if (rc != 0)
+                       GOTO(stop, rc);
+       }
+
+       dt_write_lock(env, parent, 0);
+       locked = true;
+       rc = dt_xattr_get(env, parent, buf, XATTR_NAME_LOV, BYPASS_CAPA);
+       if (rc == -ERANGE) {
+               rc = dt_xattr_get(env, parent, &LU_BUF_NULL, XATTR_NAME_LOV,
+                                 BYPASS_CAPA);
+               LASSERT(rc != 0);
+               goto again;
+       } else if (rc == -ENODATA || rc == 0) {
+               rc = lov_mds_md_size(ea_off + 1, LOV_MAGIC_V1);
+               /* If the declared is not big enough, re-try. */
+               if (buf->lb_len < rc)
+                       goto again;
+
+               fl = LU_XATTR_CREATE;
+       } else if (rc < 0) {
+               GOTO(unlock_parent, rc);
+       } else if (unlikely(buf->lb_len == 0)) {
+               goto again;
+       } else {
+               fl = LU_XATTR_REPLACE;
+       }
+
+       if (fl == LU_XATTR_CREATE) {
+               if (bk->lb_param & LPF_DRYRUN)
+                       GOTO(unlock_parent, rc = 1);
+
+               LASSERT(buf->lb_len >= rc);
+
+               buf->lb_len = rc;
+               rc = lfsck_layout_extend_lovea(env, lfsck, handle, parent, cfid,
+                                              buf, fl, ost_idx, ea_off, false);
+
+               GOTO(unlock_parent, rc);
+       }
+
+       lmm = buf->lb_buf;
+       rc1 = lfsck_layout_verify_header(lmm);
+
+       /* If the LOV EA crashed, the rebuild it. */
+       if (rc1 == -EINVAL) {
+               if (bk->lb_param & LPF_DRYRUN)
+                       GOTO(unlock_parent, rc = 1);
+
+               LASSERT(buf->lb_len >= rc);
+
+               buf->lb_len = rc;
+               memset(lmm, 0, buf->lb_len);
+               rc = lfsck_layout_extend_lovea(env, lfsck, handle, parent, cfid,
+                                              buf, fl, ost_idx, ea_off, true);
+
+               GOTO(unlock_parent, rc);
+       }
+
+       /* For other unknown magic/pattern, keep the current LOV EA. */
+       if (rc1 != 0)
+               GOTO(unlock_parent, rc = rc1);
+
+       /* Currently, we only support LOV_MAGIC_V1/LOV_MAGIC_V3 which has
+        * been verified in lfsck_layout_verify_header() already. If some
+        * new magic introduced in the future, then layout LFSCK needs to
+        * be updated also. */
+       magic = le32_to_cpu(lmm->lmm_magic);
+       if (magic == LOV_MAGIC_V1) {
+               objs = &lmm->lmm_objects[0];
+       } else {
+               LASSERT(magic == LOV_MAGIC_V3);
+               objs = &((struct lov_mds_md_v3 *)lmm)->lmm_objects[0];
+       }
+
+       count = le16_to_cpu(lmm->lmm_stripe_count);
+       if (count == 0)
+               GOTO(unlock_parent, rc = -EINVAL);
+       LASSERT(count > 0);
+
+       /* Exceed the current end of MDT-object layout EA. Then extend it. */
+       if (count <= ea_off) {
+               if (bk->lb_param & LPF_DRYRUN)
+                       GOTO(unlock_parent, rc = 1);
+
+               rc = lov_mds_md_size(ea_off + 1, magic);
+               /* If the declared is not big enough, re-try. */
+               if (buf->lb_len < rc)
+                       goto again;
+
+               buf->lb_len = rc;
+               rc = lfsck_layout_extend_lovea(env, lfsck, handle, parent, cfid,
+                                              buf, fl, ost_idx, ea_off, false);
+
+               GOTO(unlock_parent, rc);
+       }
+
+       LASSERTF(rc > 0, "invalid rc = %d\n", rc);
+
+       buf->lb_len = rc;
+       for (i = 0; i < count; i++, objs++) {
+               /* The MDT-object was created via lfsck_layout_recover_create()
+                * by others before, and we fill the dummy layout EA. */
+               if (lovea_slot_is_dummy(objs)) {
+                       if (i != ea_off)
+                               continue;
+
+                       if (bk->lb_param & LPF_DRYRUN)
+                               GOTO(unlock_parent, rc = 1);
+
+                       lmm->lmm_layout_gen =
+                           cpu_to_le16(le16_to_cpu(lmm->lmm_layout_gen) + 1);
+                       rc = lfsck_layout_refill_lovea(env, handle, parent,
+                                                      cfid, buf, objs, fl,
+                                                      ost_idx);
+                       GOTO(unlock_parent, rc);
+               }
+
+               ostid_le_to_cpu(&objs->l_ost_oi, oi);
+               ostid_to_fid(fid, oi, le32_to_cpu(objs->l_ost_idx));
+               /* It should be rare case, the slot is there, but the LFSCK
+                * does not handle it during the first-phase cycle scanning. */
+               if (unlikely(lu_fid_eq(fid, cfid))) {
+                       if (i == ea_off) {
+                               GOTO(unlock_parent, rc = 0);
+                       } else {
+                               /* Rare case that the OST-object index
+                                * does not match the parent MDT-object
+                                * layout EA. We trust the later one. */
+                               if (bk->lb_param & LPF_DRYRUN)
+                                       GOTO(unlock_parent, rc = 1);
+
+                               dt_write_unlock(env, parent);
+                               if (handle != NULL)
+                                       dt_trans_stop(env, dt, handle);
+                               lfsck_layout_unlock(&lh);
+                               buf->lb_len = buflen;
+                               rc = lfsck_layout_update_pfid(env, com, parent,
+                                                       cfid, ltd->ltd_tgt, i);
+
+                               RETURN(rc);
+                       }
+               }
+       }
+
+       /* The MDT-object exists, but related layout EA slot is occupied
+        * by others. */
+       if (bk->lb_param & LPF_DRYRUN)
+               GOTO(unlock_parent, rc = 1);
+
+       dt_write_unlock(env, parent);
+       if (handle != NULL)
+               dt_trans_stop(env, dt, handle);
+       lfsck_layout_unlock(&lh);
+       if (le32_to_cpu(lmm->lmm_magic) == LOV_MAGIC_V1)
+               objs = &lmm->lmm_objects[ea_off];
+       else
+               objs = &((struct lov_mds_md_v3 *)lmm)->lmm_objects[ea_off];
+       rc = lfsck_layout_conflict_create(env, com, ltd, rec, parent, cfid,
+                                         buf, objs, ea_off, buflen);
+
+       RETURN(rc);
+
+unlock_parent:
+       if (locked)
+               dt_write_unlock(env, parent);
+
+stop:
+       if (handle != NULL)
+               dt_trans_stop(env, dt, handle);
+
+unlock_layout:
+       lfsck_layout_unlock(&lh);
+       buf->lb_len = buflen;
+
+       return rc;
+}
+
+static int lfsck_layout_scan_orphan_one(const struct lu_env *env,
+                                       struct lfsck_component *com,
+                                       struct lfsck_tgt_desc *ltd,
+                                       struct lu_orphan_rec *rec,
+                                       struct lu_fid *cfid)
+{
+       struct lfsck_layout     *lo     = com->lc_file_ram;
+       struct lu_fid           *pfid   = &rec->lor_fid;
+       struct dt_object        *parent = NULL;
+       __u32                    ea_off = pfid->f_stripe_idx;
+       int                      rc     = 0;
+       ENTRY;
+
+       if (!fid_is_sane(cfid))
+               GOTO(out, rc = -EINVAL);
+
+       if (fid_is_zero(pfid)) {
+               rc = lfsck_layout_recreate_parent(env, com, ltd, rec, cfid,
+                                                 "N-", "", ea_off);
+               GOTO(out, rc);
+       }
+
+       pfid->f_ver = 0;
+       if (!fid_is_sane(pfid))
+               GOTO(out, rc = -EINVAL);
+
+       parent = lfsck_object_find_by_dev(env, com->lc_lfsck->li_bottom, pfid);
+       if (IS_ERR(parent))
+               GOTO(out, rc = PTR_ERR(parent));
+
+       if (unlikely(dt_object_remote(parent) != 0))
+               GOTO(put, rc = -EXDEV);
+
+       if (dt_object_exists(parent) == 0) {
+               lu_object_put(env, &parent->do_lu);
+               rc = lfsck_layout_recreate_parent(env, com, ltd, rec, cfid,
+                                                 "R-", "", ea_off);
+               GOTO(out, rc);
+       }
+
+       if (!S_ISREG(lu_object_attr(&parent->do_lu)))
+               GOTO(put, rc = -EISDIR);
+
+       rc = lfsck_layout_recreate_lovea(env, com, ltd, rec, parent, cfid,
+                                        ltd->ltd_index, ea_off);
+
+       GOTO(put, rc);
+
+put:
+       if (rc <= 0)
+               lu_object_put(env, &parent->do_lu);
+       else
+               /* The layout EA is changed, need to be reloaded next time. */
+               lu_object_put_nocache(env, &parent->do_lu);
+
+out:
+       down_write(&com->lc_sem);
+       com->lc_new_scanned++;
+       com->lc_new_checked++;
+       if (rc > 0) {
+               lo->ll_objs_repaired[LLIT_ORPHAN - 1]++;
+               rc = 0;
+       } else if (rc < 0) {
+               lo->ll_objs_failed_phase2++;
+       }
+       up_write(&com->lc_sem);
+
+       return rc;
+}
+
+static int lfsck_layout_scan_orphan(const struct lu_env *env,
+                                   struct lfsck_component *com,
+                                   struct lfsck_tgt_desc *ltd)
+{
+       struct lfsck_layout             *lo     = com->lc_file_ram;
+       struct lfsck_instance           *lfsck  = com->lc_lfsck;
+       struct lfsck_bookmark           *bk     = &lfsck->li_bookmark_ram;
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct ost_id                   *oi     = &info->lti_oi;
+       struct lu_fid                   *fid    = &info->lti_fid;
+       struct dt_object                *obj;
+       const struct dt_it_ops          *iops;
+       struct dt_it                    *di;
+       int                              rc     = 0;
+       ENTRY;
+
+       CDEBUG(D_LFSCK, "%s: start the orphan scanning for OST%04x\n",
+              lfsck_lfsck2name(lfsck), ltd->ltd_index);
+
+       ostid_set_seq(oi, FID_SEQ_IDIF);
+       ostid_set_id(oi, 0);
+       ostid_to_fid(fid, oi, ltd->ltd_index);
+       obj = lfsck_object_find_by_dev(env, ltd->ltd_tgt, fid);
+       if (unlikely(IS_ERR(obj)))
+               RETURN(PTR_ERR(obj));
+
+       rc = obj->do_ops->do_index_try(env, obj, &dt_lfsck_orphan_features);
+       if (rc != 0)
+               GOTO(put, rc);
+
+       iops = &obj->do_index_ops->dio_it;
+       di = iops->init(env, obj, 0, BYPASS_CAPA);
+       if (IS_ERR(di))
+               GOTO(put, rc = PTR_ERR(di));
+
+       rc = iops->load(env, di, 0);
+       if (rc == -ESRCH) {
+               /* -ESRCH means that the orphan OST-objects rbtree has been
+                * cleanup because of the OSS server restart or other errors. */
+               lo->ll_flags |= LF_INCOMPLETE;
+               GOTO(fini, rc);
+       }
+
+       if (rc == 0)
+               rc = iops->next(env, di);
+       else if (rc > 0)
+               rc = 0;
+
+       if (rc < 0)
+               GOTO(fini, rc);
+
+       if (rc > 0)
+               GOTO(fini, rc = 0);
+
+       do {
+               struct dt_key           *key;
+               struct lu_orphan_rec    *rec = &info->lti_rec;
+
+               if (OBD_FAIL_CHECK(OBD_FAIL_LFSCK_DELAY3) &&
+                   cfs_fail_val > 0) {
+                       struct ptlrpc_thread    *thread = &lfsck->li_thread;
+                       struct l_wait_info       lwi;
+
+                       lwi = LWI_TIMEOUT(cfs_time_seconds(cfs_fail_val),
+                                         NULL, NULL);
+                       l_wait_event(thread->t_ctl_waitq,
+                                    !thread_is_running(thread),
+                                    &lwi);
+               }
+
+               key = iops->key(env, di);
+               com->lc_fid_latest_scanned_phase2 = *(struct lu_fid *)key;
+               rc = iops->rec(env, di, (struct dt_rec *)rec, 0);
+               if (rc == 0)
+                       rc = lfsck_layout_scan_orphan_one(env, com, ltd, rec,
+                                       &com->lc_fid_latest_scanned_phase2);
+               if (rc != 0 && bk->lb_param & LPF_FAILOUT)
+                       GOTO(fini, rc);
+
+               lfsck_control_speed_by_self(com);
+               do {
+                       rc = iops->next(env, di);
+               } while (rc < 0 && !(bk->lb_param & LPF_FAILOUT));
+       } while (rc == 0);
+
+       GOTO(fini, rc);
+
+fini:
+       iops->put(env, di);
+       iops->fini(env, di);
+put:
+       lu_object_put(env, &obj->do_lu);
+
+       CDEBUG(D_LFSCK, "%s: finish the orphan scanning for OST%04x, rc = %d\n",
+              lfsck_lfsck2name(lfsck), ltd->ltd_index, rc);
+
+       return rc > 0 ? 0 : rc;
+}
+
+/* For the MDT-object with dangling reference, we need to repare the
+ * inconsistency according to the LFSCK sponsor's requirement:
+ *
+ * 1) Keep the inconsistency there and report the inconsistency case,
+ *    then give the chance to the application to find related issues,
+ *    and the users can make the decision about how to handle it with
+ *    more human knownledge. (by default)
+ *
+ * 2) Re-create the missed OST-object with the FID/owner information. */
+static int lfsck_layout_repair_dangling(const struct lu_env *env,
+                                       struct lfsck_component *com,
+                                       struct lfsck_layout_req *llr,
+                                       const struct lu_attr *pla)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct filter_fid               *pfid   = &info->lti_new_pfid;
+       struct dt_allocation_hint       *hint   = &info->lti_hint;
+       struct lu_attr                  *cla    = &info->lti_la2;
+       struct dt_object                *parent = llr->llr_parent->llo_obj;
+       struct dt_object                *child  = llr->llr_child;
+       struct dt_device                *dev    = lfsck_obj2dt_dev(child);
+       const struct lu_fid             *tfid   = lu_object_fid(&parent->do_lu);
+       struct thandle                  *handle;
+       struct lu_buf                   *buf;
+       struct lustre_handle             lh     = { 0 };
+       int                              rc;
+       bool                             create;
+       ENTRY;
+
+       if (com->lc_lfsck->li_bookmark_ram.lb_param & LPF_CREATE_OSTOBJ)
+               create = true;
+       else
+               create = false;
+
+       CDEBUG(D_LFSCK, "Found dangling reference for: parent "DFID
+              ", child "DFID", OST-index %u, stripe-index %u, owner %u:%u. %s",
+              PFID(lfsck_dto2fid(parent)), PFID(lfsck_dto2fid(child)),
+              llr->llr_ost_idx, llr->llr_lov_idx, pla->la_uid, pla->la_gid,
+              create ? "Create the lost OST-object as required.\n" :
+                       "Keep the MDT-object there by default.\n");
+
+       if (!create)
+               RETURN(1);
+
+       memset(cla, 0, sizeof(*cla));
+       cla->la_uid = pla->la_uid;
+       cla->la_gid = pla->la_gid;
+       cla->la_mode = S_IFREG | 0666;
+       cla->la_valid = LA_TYPE | LA_MODE | LA_UID | LA_GID |
+                       LA_ATIME | LA_MTIME | LA_CTIME;
+
+       rc = lfsck_layout_lock(env, com, parent, &lh,
+                              MDS_INODELOCK_LAYOUT | MDS_INODELOCK_XATTR);
+       if (rc != 0)
+               RETURN(rc);
+
+       handle = dt_trans_create(env, dev);
+       if (IS_ERR(handle))
+               GOTO(unlock1, rc = PTR_ERR(handle));
+
+       hint->dah_parent = NULL;
+       hint->dah_mode = 0;
+       pfid->ff_parent.f_seq = cpu_to_le64(tfid->f_seq);
+       pfid->ff_parent.f_oid = cpu_to_le32(tfid->f_oid);
+       /* Currently, the filter_fid::ff_parent::f_ver is not the real parent
+        * MDT-object's FID::f_ver, instead it is the OST-object index in its
+        * parent MDT-object's layout EA. */
+       pfid->ff_parent.f_stripe_idx = cpu_to_le32(llr->llr_lov_idx);
+       buf = lfsck_buf_get(env, pfid, sizeof(struct filter_fid));
+
+       rc = dt_declare_create(env, child, cla, hint, NULL, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_declare_xattr_set(env, child, buf, XATTR_NAME_FID,
+                                 LU_XATTR_CREATE, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_trans_start(env, dev, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       dt_read_lock(env, parent, 0);
+       if (unlikely(lu_object_is_dying(parent->do_lu.lo_header)))
+               GOTO(unlock2, rc = 1);
+
+       rc = dt_create(env, child, cla, hint, NULL, handle);
+       if (rc != 0)
+               GOTO(unlock2, rc);
+
+       rc = dt_xattr_set(env, child, buf, XATTR_NAME_FID, LU_XATTR_CREATE,
+                         handle, BYPASS_CAPA);
+
+       GOTO(unlock2, rc);
+
+unlock2:
+       dt_read_unlock(env, parent);
+
+stop:
+       rc = lfsck_layout_trans_stop(env, dev, handle, rc);
+
+unlock1:
+       lfsck_layout_unlock(&lh);
+
+       return rc;
+}
+
+/* If the OST-object does not recognize the MDT-object as its parent, and
+ * there is no other MDT-object claims as its parent, then just trust the
+ * given MDT-object as its parent. So update the OST-object filter_fid. */
+static int lfsck_layout_repair_unmatched_pair(const struct lu_env *env,
+                                             struct lfsck_component *com,
+                                             struct lfsck_layout_req *llr,
+                                             const struct lu_attr *pla)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct filter_fid               *pfid   = &info->lti_new_pfid;
+       struct lu_attr                  *tla    = &info->lti_la3;
+       struct dt_object                *parent = llr->llr_parent->llo_obj;
+       struct dt_object                *child  = llr->llr_child;
+       struct dt_device                *dev    = lfsck_obj2dt_dev(child);
+       const struct lu_fid             *tfid   = lu_object_fid(&parent->do_lu);
+       struct thandle                  *handle;
+       struct lu_buf                   *buf;
+       struct lustre_handle             lh     = { 0 };
+       int                              rc;
+       ENTRY;
+
+       CDEBUG(D_LFSCK, "Repair unmatched MDT-OST pair for: parent "DFID
+              ", child "DFID", OST-index %u, stripe-index %u, owner %u:%u\n",
+              PFID(lfsck_dto2fid(parent)), PFID(lfsck_dto2fid(child)),
+              llr->llr_ost_idx, llr->llr_lov_idx, pla->la_uid, pla->la_gid);
+
+       rc = lfsck_layout_lock(env, com, parent, &lh,
+                              MDS_INODELOCK_LAYOUT | MDS_INODELOCK_XATTR);
+       if (rc != 0)
+               RETURN(rc);
+
+       handle = dt_trans_create(env, dev);
+       if (IS_ERR(handle))
+               GOTO(unlock1, rc = PTR_ERR(handle));
+
+       pfid->ff_parent.f_seq = cpu_to_le64(tfid->f_seq);
+       pfid->ff_parent.f_oid = cpu_to_le32(tfid->f_oid);
+       /* Currently, the filter_fid::ff_parent::f_ver is not the real parent
+        * MDT-object's FID::f_ver, instead it is the OST-object index in its
+        * parent MDT-object's layout EA. */
+       pfid->ff_parent.f_stripe_idx = cpu_to_le32(llr->llr_lov_idx);
+       buf = lfsck_buf_get(env, pfid, sizeof(struct filter_fid));
+
+       rc = dt_declare_xattr_set(env, child, buf, XATTR_NAME_FID, 0, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       tla->la_valid = LA_UID | LA_GID;
+       tla->la_uid = pla->la_uid;
+       tla->la_gid = pla->la_gid;
+       rc = dt_declare_attr_set(env, child, tla, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_trans_start(env, dev, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       dt_write_lock(env, parent, 0);
+       if (unlikely(lu_object_is_dying(parent->do_lu.lo_header)))
+               GOTO(unlock2, rc = 1);
+
+       rc = dt_xattr_set(env, child, buf, XATTR_NAME_FID, 0, handle,
+                         BYPASS_CAPA);
+       if (rc != 0)
+               GOTO(unlock2, rc);
+
+       /* Get the latest parent's owner. */
+       rc = dt_attr_get(env, parent, tla, BYPASS_CAPA);
+       if (rc != 0)
+               GOTO(unlock2, rc);
+
+       tla->la_valid = LA_UID | LA_GID;
+       rc = dt_attr_set(env, child, tla, handle, BYPASS_CAPA);
+
+       GOTO(unlock2, rc);
+
+unlock2:
+       dt_write_unlock(env, parent);
+
+stop:
+       rc = lfsck_layout_trans_stop(env, dev, handle, rc);
+
+unlock1:
+       lfsck_layout_unlock(&lh);
+
+       return rc;
+}
+
+/* If there are more than one MDT-objects claim as the OST-object's parent,
+ * and the OST-object only recognizes one of them, then we need to generate
+ * new OST-object(s) with new fid(s) for the non-recognized MDT-object(s). */
+static int lfsck_layout_repair_multiple_references(const struct lu_env *env,
+                                                  struct lfsck_component *com,
+                                                  struct lfsck_layout_req *llr,
+                                                  struct lu_attr *la,
+                                                  struct lu_buf *buf)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct dt_allocation_hint       *hint   = &info->lti_hint;
+       struct dt_object_format         *dof    = &info->lti_dof;
+       struct dt_device                *pdev   = com->lc_lfsck->li_next;
+       struct ost_id                   *oi     = &info->lti_oi;
+       struct dt_object                *parent = llr->llr_parent->llo_obj;
+       struct dt_device                *cdev   = lfsck_obj2dt_dev(llr->llr_child);
+       struct dt_object                *child  = NULL;
+       struct lu_device                *d      = &cdev->dd_lu_dev;
+       struct lu_object                *o      = NULL;
+       struct thandle                  *handle;
+       struct lov_mds_md_v1            *lmm;
+       struct lov_ost_data_v1          *objs;
+       struct lustre_handle             lh     = { 0 };
+       __u32                            magic;
+       int                              rc;
+       ENTRY;
+
+       CDEBUG(D_LFSCK, "Repair multiple references for: parent "DFID
+              ", OST-index %u, stripe-index %u, owner %u:%u\n",
+              PFID(lfsck_dto2fid(parent)), llr->llr_ost_idx,
+              llr->llr_lov_idx, la->la_uid, la->la_gid);
+
+       rc = lfsck_layout_lock(env, com, parent, &lh,
+                              MDS_INODELOCK_LAYOUT | MDS_INODELOCK_XATTR);
+       if (rc != 0)
+               RETURN(rc);
+
+       handle = dt_trans_create(env, pdev);
+       if (IS_ERR(handle))
+               GOTO(unlock1, rc = PTR_ERR(handle));
+
+       o = lu_object_anon(env, d, NULL);
+       if (IS_ERR(o))
+               GOTO(stop, rc = PTR_ERR(o));
+
+       child = container_of(o, struct dt_object, do_lu);
+       o = lu_object_locate(o->lo_header, d->ld_type);
+       if (unlikely(o == NULL))
+               GOTO(stop, rc = -EINVAL);
+
+       child = container_of(o, struct dt_object, do_lu);
+       la->la_valid = LA_UID | LA_GID;
+       hint->dah_parent = NULL;
+       hint->dah_mode = 0;
+       dof->dof_type = DFT_REGULAR;
+       rc = dt_declare_create(env, child, la, NULL, NULL, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_declare_xattr_set(env, parent, buf, XATTR_NAME_LOV,
+                                 LU_XATTR_REPLACE, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_trans_start(env, pdev, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       dt_write_lock(env, parent, 0);
+       if (unlikely(lu_object_is_dying(parent->do_lu.lo_header)))
+               GOTO(unlock2, rc = 0);
+
+       rc = dt_xattr_get(env, parent, buf, XATTR_NAME_LOV, BYPASS_CAPA);
+       if (unlikely(rc == 0 || rc == -ENODATA || rc == -ERANGE))
+               GOTO(unlock2, rc = 0);
+
+       lmm = buf->lb_buf;
+       /* Someone change layout during the LFSCK, no need to repair then. */
+       if (le16_to_cpu(lmm->lmm_layout_gen) != llr->llr_parent->llo_gen)
+               GOTO(unlock2, rc = 0);
+
+       rc = dt_create(env, child, la, hint, dof, handle);
+       if (rc != 0)
+               GOTO(unlock2, rc);
+
+       /* Currently, we only support LOV_MAGIC_V1/LOV_MAGIC_V3 which has
+        * been verified in lfsck_layout_verify_header() already. If some
+        * new magic introduced in the future, then layout LFSCK needs to
+        * be updated also. */
+       magic = le32_to_cpu(lmm->lmm_magic);
+       if (magic == LOV_MAGIC_V1) {
+               objs = &lmm->lmm_objects[0];
+       } else {
+               LASSERT(magic == LOV_MAGIC_V3);
+               objs = &((struct lov_mds_md_v3 *)lmm)->lmm_objects[0];
+       }
+
+       lmm->lmm_layout_gen = cpu_to_le16(llr->llr_parent->llo_gen + 1);
+       fid_to_ostid(lu_object_fid(&child->do_lu), oi);
+       ostid_cpu_to_le(oi, &objs[llr->llr_lov_idx].l_ost_oi);
+       objs[llr->llr_lov_idx].l_ost_gen = cpu_to_le32(0);
+       objs[llr->llr_lov_idx].l_ost_idx = cpu_to_le32(llr->llr_ost_idx);
+       rc = dt_xattr_set(env, parent, buf, XATTR_NAME_LOV,
+                         LU_XATTR_REPLACE, handle, BYPASS_CAPA);
+
+       GOTO(unlock2, rc = (rc == 0 ? 1 : rc));
+
+unlock2:
+       dt_write_unlock(env, parent);
+
+stop:
+       if (child != NULL)
+               lu_object_put(env, &child->do_lu);
+
+       dt_trans_stop(env, pdev, handle);
+
+unlock1:
+       lfsck_layout_unlock(&lh);
+
+       return rc;
+}
+
+/* If the MDT-object and the OST-object have different owner information,
+ * then trust the MDT-object, because the normal chown/chgrp handle order
+ * is from MDT to OST, and it is possible that some chown/chgrp operation
+ * is partly done. */
+static int lfsck_layout_repair_owner(const struct lu_env *env,
+                                    struct lfsck_component *com,
+                                    struct lfsck_layout_req *llr,
+                                    struct lu_attr *pla)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct lu_attr                  *tla    = &info->lti_la3;
+       struct dt_object                *parent = llr->llr_parent->llo_obj;
+       struct dt_object                *child  = llr->llr_child;
+       struct dt_device                *dev    = lfsck_obj2dt_dev(child);
+       struct thandle                  *handle;
+       int                              rc;
+       ENTRY;
+
+       CDEBUG(D_LFSCK, "Repair inconsistent file owner for: parent "DFID
+              ", child "DFID", OST-index %u, stripe-index %u, owner %u:%u\n",
+              PFID(lfsck_dto2fid(parent)), PFID(lfsck_dto2fid(child)),
+              llr->llr_ost_idx, llr->llr_lov_idx, pla->la_uid, pla->la_gid);
+
+       handle = dt_trans_create(env, dev);
+       if (IS_ERR(handle))
+               RETURN(PTR_ERR(handle));
+
+       tla->la_uid = pla->la_uid;
+       tla->la_gid = pla->la_gid;
+       tla->la_valid = LA_UID | LA_GID;
+       rc = dt_declare_attr_set(env, child, tla, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_trans_start(env, dev, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       /* Use the dt_object lock to serialize with destroy and attr_set. */
+       dt_read_lock(env, parent, 0);
+       if (unlikely(lu_object_is_dying(parent->do_lu.lo_header)))
+               GOTO(unlock, rc = 1);
+
+       /* Get the latest parent's owner. */
+       rc = dt_attr_get(env, parent, tla, BYPASS_CAPA);
+       if (rc != 0) {
+               CWARN("%s: fail to get the latest parent's ("DFID") owner, "
+                     "not sure whether some others chown/chgrp during the "
+                     "LFSCK: rc = %d\n", lfsck_lfsck2name(com->lc_lfsck),
+                     PFID(lfsck_dto2fid(parent)), rc);
+
+               GOTO(unlock, rc);
+       }
+
+       /* Some others chown/chgrp during the LFSCK, needs to do nothing. */
+       if (unlikely(tla->la_uid != pla->la_uid ||
+                    tla->la_gid != pla->la_gid))
+               GOTO(unlock, rc = 1);
+
+       tla->la_valid = LA_UID | LA_GID;
+       rc = dt_attr_set(env, child, tla, handle, BYPASS_CAPA);
+
+       GOTO(unlock, rc);
+
+unlock:
+       dt_read_unlock(env, parent);
+
+stop:
+       rc = lfsck_layout_trans_stop(env, dev, handle, rc);
+
+       return rc;
+}
+
+/* Check whether the OST-object correctly back points to the
+ * MDT-object (@parent) via the XATTR_NAME_FID xattr (@pfid). */
+static int lfsck_layout_check_parent(const struct lu_env *env,
+                                    struct lfsck_component *com,
+                                    struct dt_object *parent,
+                                    const struct lu_fid *pfid,
+                                    const struct lu_fid *cfid,
+                                    const struct lu_attr *pla,
+                                    const struct lu_attr *cla,
+                                    struct lfsck_layout_req *llr,
+                                    struct lu_buf *lov_ea, __u32 idx)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct lu_buf                   *buf    = &info->lti_big_buf;
+       struct dt_object                *tobj;
+       struct lov_mds_md_v1            *lmm;
+       struct lov_ost_data_v1          *objs;
+       int                              rc;
+       int                              i;
+       __u32                            magic;
+       __u16                            count;
+       ENTRY;
+
+       if (fid_is_zero(pfid)) {
+               /* client never wrote. */
+               if (cla->la_size == 0 && cla->la_blocks == 0) {
+                       if (unlikely(cla->la_uid != pla->la_uid ||
+                                    cla->la_gid != pla->la_gid))
+                               RETURN (LLIT_INCONSISTENT_OWNER);
+
+                       RETURN(0);
+               }
+
+               RETURN(LLIT_UNMATCHED_PAIR);
+       }
+
+       if (unlikely(!fid_is_sane(pfid)))
+               RETURN(LLIT_UNMATCHED_PAIR);
+
+       if (lu_fid_eq(pfid, lu_object_fid(&parent->do_lu))) {
+               if (llr->llr_lov_idx == idx)
+                       RETURN(0);
+
+               RETURN(LLIT_UNMATCHED_PAIR);
+       }
+
+       tobj = lfsck_object_find(env, com->lc_lfsck, pfid);
+       if (tobj == NULL)
+               RETURN(LLIT_UNMATCHED_PAIR);
+
+       if (IS_ERR(tobj))
+               RETURN(PTR_ERR(tobj));
+
+       if (!dt_object_exists(tobj))
+               GOTO(out, rc = LLIT_UNMATCHED_PAIR);
+
+       /* Load the tobj's layout EA, in spite of it is a local MDT-object or
+        * remote one on another MDT. Then check whether the given OST-object
+        * is in such layout. If yes, it is multiple referenced, otherwise it
+        * is unmatched referenced case. */
+       rc = lfsck_layout_get_lovea(env, tobj, buf, NULL);
+       if (rc == 0)
+               GOTO(out, rc = LLIT_UNMATCHED_PAIR);
+
+       if (rc < 0)
+               GOTO(out, rc);
+
+       lmm = buf->lb_buf;
+       magic = le32_to_cpu(lmm->lmm_magic);
+       if (magic == LOV_MAGIC_V1) {
+               objs = &lmm->lmm_objects[0];
+       } else {
+               LASSERT(magic == LOV_MAGIC_V3);
+               objs = &((struct lov_mds_md_v3 *)lmm)->lmm_objects[0];
+       }
+
+       count = le16_to_cpu(lmm->lmm_stripe_count);
+       for (i = 0; i < count; i++, objs++) {
+               struct lu_fid           *tfid   = &info->lti_fid2;
+               struct ost_id           *oi     = &info->lti_oi;
+
+               if (lovea_slot_is_dummy(objs))
+                       continue;
+
+               ostid_le_to_cpu(&objs->l_ost_oi, oi);
+               ostid_to_fid(tfid, oi, le32_to_cpu(objs->l_ost_idx));
+               if (lu_fid_eq(cfid, tfid)) {
+                       *lov_ea = *buf;
+
+                       GOTO(out, rc = LLIT_MULTIPLE_REFERENCED);
+               }
+       }
+
+       GOTO(out, rc = LLIT_UNMATCHED_PAIR);
+
+out:
+       lfsck_object_put(env, tobj);
+
+       return rc;
+}
+
+static int lfsck_layout_assistant_handle_one(const struct lu_env *env,
+                                            struct lfsck_component *com,
+                                            struct lfsck_layout_req *llr)
+{
+       struct lfsck_layout                  *lo     = com->lc_file_ram;
+       struct lfsck_thread_info             *info   = lfsck_env_info(env);
+       struct filter_fid_old                *pea    = &info->lti_old_pfid;
+       struct lu_fid                        *pfid   = &info->lti_fid;
+       struct lu_buf                        *buf    = NULL;
+       struct dt_object                     *parent = llr->llr_parent->llo_obj;
+       struct dt_object                     *child  = llr->llr_child;
+       struct lu_attr                       *pla    = &info->lti_la;
+       struct lu_attr                       *cla    = &info->lti_la2;
+       struct lfsck_instance                *lfsck  = com->lc_lfsck;
+       struct lfsck_bookmark                *bk     = &lfsck->li_bookmark_ram;
+       enum lfsck_layout_inconsistency_type  type   = LLIT_NONE;
+       __u32                                 idx    = 0;
+       int                                   rc;
+       ENTRY;
+
+       rc = dt_attr_get(env, parent, pla, BYPASS_CAPA);
+       if (rc != 0) {
+               if (lu_object_is_dying(parent->do_lu.lo_header))
+                       RETURN(0);
+
+               GOTO(out, rc);
+       }
+
+       rc = dt_attr_get(env, child, cla, BYPASS_CAPA);
+       if (rc == -ENOENT) {
+               if (lu_object_is_dying(parent->do_lu.lo_header))
+                       RETURN(0);
+
+               type = LLIT_DANGLING;
+               goto repair;
+       }
+
+       if (rc != 0)
+               GOTO(out, rc);
+
+       buf = lfsck_buf_get(env, pea, sizeof(struct filter_fid_old));
+       rc= dt_xattr_get(env, child, buf, XATTR_NAME_FID, BYPASS_CAPA);
+       if (unlikely(rc >= 0 && rc != sizeof(struct filter_fid_old) &&
+                    rc != sizeof(struct filter_fid))) {
+               type = LLIT_UNMATCHED_PAIR;
+               goto repair;
+       }
+
+       if (rc < 0 && rc != -ENODATA)
+               GOTO(out, rc);
+
+       if (rc == -ENODATA) {
+               fid_zero(pfid);
+       } else {
+               fid_le_to_cpu(pfid, &pea->ff_parent);
+               /* Currently, the filter_fid::ff_parent::f_ver is not the
+                * real parent MDT-object's FID::f_ver, instead it is the
+                * OST-object index in its parent MDT-object's layout EA. */
+               idx = pfid->f_stripe_idx;
+               pfid->f_ver = 0;
+       }
+
+       rc = lfsck_layout_check_parent(env, com, parent, pfid,
+                                      lu_object_fid(&child->do_lu),
+                                      pla, cla, llr, buf, idx);
+       if (rc > 0) {
+               type = rc;
+               goto repair;
+       }
+
+       if (rc < 0)
+               GOTO(out, rc);
+
+       if (unlikely(cla->la_uid != pla->la_uid ||
+                    cla->la_gid != pla->la_gid)) {
+               type = LLIT_INCONSISTENT_OWNER;
+               goto repair;
+       }
+
+repair:
+       if (bk->lb_param & LPF_DRYRUN) {
+               if (type != LLIT_NONE)
+                       GOTO(out, rc = 1);
+               else
+                       GOTO(out, rc = 0);
+       }
+
+       switch (type) {
+       case LLIT_DANGLING:
+               rc = lfsck_layout_repair_dangling(env, com, llr, pla);
+               break;
+       case LLIT_UNMATCHED_PAIR:
+               rc = lfsck_layout_repair_unmatched_pair(env, com, llr, pla);
+               break;
+       case LLIT_MULTIPLE_REFERENCED:
+               rc = lfsck_layout_repair_multiple_references(env, com, llr,
+                                                            pla, buf);
+               break;
+       case LLIT_INCONSISTENT_OWNER:
+               rc = lfsck_layout_repair_owner(env, com, llr, pla);
+               break;
+       default:
+               rc = 0;
+               break;
+       }
+
+       GOTO(out, rc);
+
+out:
+       down_write(&com->lc_sem);
+       if (rc < 0) {
+               struct lfsck_layout_master_data *llmd = com->lc_data;
+
+               if (unlikely(llmd->llmd_exit)) {
+                       rc = 0;
+               } else if (rc == -ENOTCONN || rc == -ESHUTDOWN ||
+                          rc == -ETIMEDOUT || rc == -EHOSTDOWN ||
+                          rc == -EHOSTUNREACH) {
+                       /* If cannot touch the target server,
+                        * mark the LFSCK as INCOMPLETE. */
+                       CERROR("%s: Fail to talk with OST %x: rc = %d.\n",
+                              lfsck_lfsck2name(lfsck), llr->llr_ost_idx, rc);
+                       lo->ll_flags |= LF_INCOMPLETE;
+                       lo->ll_objs_skipped++;
+                       rc = 0;
+               } else {
+                       lfsck_layout_record_failure(env, lfsck, lo);
+               }
+       } else if (rc > 0) {
+               LASSERTF(type > LLIT_NONE && type <= LLIT_MAX,
+                        "unknown type = %d\n", type);
+
+               lo->ll_objs_repaired[type - 1]++;
+               if (bk->lb_param & LPF_DRYRUN &&
+                   unlikely(lo->ll_pos_first_inconsistent == 0))
+                       lo->ll_pos_first_inconsistent =
+                       lfsck->li_obj_oit->do_index_ops->dio_it.store(env,
+                                                       lfsck->li_di_oit);
+       }
+       up_write(&com->lc_sem);
+
+       return rc;
 }
 
 static int lfsck_layout_assistant(void *args)
@@ -1249,26 +3453,21 @@ static int lfsck_layout_assistant(void *args)
        struct l_wait_info               lwi     = { 0 };
        int                              rc      = 0;
        int                              rc1     = 0;
-       __u32                            flags;
        ENTRY;
 
-       if (lta->lta_lsp->lsp_start != NULL)
-               flags  = lta->lta_lsp->lsp_start->ls_flags;
-       else
-               flags = bk->lb_param;
        memset(lr, 0, sizeof(*lr));
        lr->lr_event = LE_START;
-       lr->lr_index = lfsck_dev_idx(lfsck->li_bottom);
        lr->lr_valid = LSV_SPEED_LIMIT | LSV_ERROR_HANDLE | LSV_DRYRUN |
-                      LSV_ASYNC_WINDOWS;
+                      LSV_ASYNC_WINDOWS | LSV_CREATE_OSTOBJ;
        lr->lr_speed = bk->lb_speed_limit;
        lr->lr_version = bk->lb_version;
        lr->lr_param = bk->lb_param;
        lr->lr_async_windows = bk->lb_async_windows;
+       lr->lr_flags = LEF_TO_OST;
        if (pos->lp_oit_cookie <= 1)
                lr->lr_param |= LPF_RESET;
 
-       rc = lfsck_layout_master_notify_others(env, com, lr, flags);
+       rc = lfsck_layout_master_notify_others(env, com, lr);
        if (rc != 0) {
                CERROR("%s: fail to notify others for layout start: rc = %d\n",
                       lfsck_lfsck2name(lfsck), rc);
@@ -1284,34 +3483,39 @@ static int lfsck_layout_assistant(void *args)
                while (!list_empty(&llmd->llmd_req_list)) {
                        bool wakeup = false;
 
-                       if (unlikely(llmd->llmd_exit))
+                       if (unlikely(llmd->llmd_exit ||
+                                    !thread_is_running(mthread)))
                                GOTO(cleanup1, rc = llmd->llmd_post_result);
 
-                       /* XXX: To be extended in other patch.
-                        *
-                        * Compare the OST side attribute with local attribute,
-                        * and fix it if found inconsistency. */
-
-                       spin_lock(&llmd->llmd_lock);
                        llr = list_entry(llmd->llmd_req_list.next,
                                         struct lfsck_layout_req,
                                         llr_list);
+                       /* Only the lfsck_layout_assistant thread itself can
+                        * remove the "llr" from the head of the list, LFSCK
+                        * engine thread only inserts other new "lld" at the
+                        * end of the list. So it is safe to handle current
+                        * "llr" without the spin_lock. */
+                       rc = lfsck_layout_assistant_handle_one(env, com, llr);
+                       spin_lock(&llmd->llmd_lock);
                        list_del_init(&llr->llr_list);
-                       if (bk->lb_async_windows != 0 &&
-                           llmd->llmd_prefetched >= bk->lb_async_windows)
-                               wakeup = true;
-
                        llmd->llmd_prefetched--;
+                       /* Wake up the main engine thread only when the list
+                        * is empty or half of the prefetched items have been
+                        * handled to avoid too frequent thread schedule. */
+                       if (llmd->llmd_prefetched == 0 ||
+                           (bk->lb_async_windows != 0 &&
+                            bk->lb_async_windows / 2 ==
+                            llmd->llmd_prefetched))
+                               wakeup = true;
                        spin_unlock(&llmd->llmd_lock);
                        if (wakeup)
                                wake_up_all(&mthread->t_ctl_waitq);
 
                        lfsck_layout_req_fini(env, llr);
+                       if (rc < 0 && bk->lb_param & LPF_FAILOUT)
+                               GOTO(cleanup1, rc);
                }
 
-               /* Wakeup the master engine if it is waiting in checkpoint. */
-               wake_up_all(&mthread->t_ctl_waitq);
-
                l_wait_event(athread->t_ctl_waitq,
                             !lfsck_layout_req_empty(llmd) ||
                             llmd->llmd_exit ||
@@ -1330,10 +3534,9 @@ static int lfsck_layout_assistant(void *args)
                        LASSERT(llmd->llmd_post_result > 0);
 
                        memset(lr, 0, sizeof(*lr));
-                       lr->lr_index = lfsck_dev_idx(lfsck->li_bottom);
                        lr->lr_event = LE_PHASE1_DONE;
                        lr->lr_status = llmd->llmd_post_result;
-                       rc = lfsck_layout_master_notify_others(env, com, lr, 0);
+                       rc = lfsck_layout_master_notify_others(env, com, lr);
                        if (rc != 0)
                                CERROR("%s: failed to notify others "
                                       "for layout post: rc = %d\n",
@@ -1349,6 +3552,16 @@ static int lfsck_layout_assistant(void *args)
                        llmd->llmd_in_double_scan = 1;
                        wake_up_all(&mthread->t_ctl_waitq);
 
+                       com->lc_new_checked = 0;
+                       com->lc_new_scanned = 0;
+                       com->lc_time_last_checkpoint = cfs_time_current();
+                       com->lc_time_next_checkpoint =
+                               com->lc_time_last_checkpoint +
+                               cfs_time_seconds(LFSCK_CHECKPOINT_INTERVAL);
+
+                       /* flush all async updating before handling orphan. */
+                       dt_sync(env, lfsck->li_next);
+
                        while (llmd->llmd_in_double_scan) {
                                struct lfsck_tgt_descs  *ltds =
                                                        &lfsck->li_ost_descs;
@@ -1394,11 +3607,13 @@ orphan:
                                                &ltd->ltd_layout_phase_list);
                                        spin_unlock(&ltds->ltd_lock);
 
-                                       rc = lfsck_layout_scan_orphan(env, com,
-                                                                     ltd);
-                                       if (rc != 0 &&
-                                           bk->lb_param & LPF_FAILOUT)
-                                               GOTO(cleanup2, rc);
+                                       if (bk->lb_param & LPF_ALL_TGT) {
+                                               rc = lfsck_layout_scan_orphan(
+                                                               env, com, ltd);
+                                               if (rc != 0 &&
+                                                   bk->lb_param & LPF_FAILOUT)
+                                                       GOTO(cleanup2, rc);
+                                       }
 
                                        if (unlikely(llmd->llmd_exit ||
                                                !thread_is_running(mthread)))
@@ -1419,6 +3634,9 @@ orphan:
 cleanup1:
        /* Cleanup the unfinished requests. */
        spin_lock(&llmd->llmd_lock);
+       if (rc < 0)
+               llmd->llmd_assistant_status = rc;
+
        while (!list_empty(&llmd->llmd_req_list)) {
                llr = list_entry(llmd->llmd_req_list.next,
                                 struct lfsck_layout_req,
@@ -1436,34 +3654,43 @@ cleanup1:
 
 cleanup2:
        memset(lr, 0, sizeof(*lr));
-       lr->lr_index = lfsck_dev_idx(lfsck->li_bottom);
        if (rc > 0) {
                lr->lr_event = LE_PHASE2_DONE;
-               flags = 0;
                lr->lr_status = rc;
        } else if (rc == 0) {
-               lr->lr_event = LE_STOP;
-               if (lfsck->li_status == LS_PAUSED ||
-                   lfsck->li_status == LS_CO_PAUSED) {
-                       flags = 0;
-                       lr->lr_status = LS_CO_PAUSED;
-               } else if (lfsck->li_status == LS_STOPPED ||
-                        lfsck->li_status == LS_CO_STOPPED) {
-                       flags = lfsck->li_flags;
-                       if (flags & LPF_BROADCAST)
-                               lr->lr_status = LS_STOPPED;
-                       else
-                               lr->lr_status = LS_CO_STOPPED;
+               if (lfsck->li_flags & LPF_ALL_TGT) {
+                       lr->lr_event = LE_STOP;
+                       lr->lr_status = LS_STOPPED;
                } else {
-                       LBUG();
+                       lr->lr_event = LE_PEER_EXIT;
+                       switch (lfsck->li_status) {
+                       case LS_PAUSED:
+                       case LS_CO_PAUSED:
+                               lr->lr_status = LS_CO_PAUSED;
+                               break;
+                       case LS_STOPPED:
+                       case LS_CO_STOPPED:
+                               lr->lr_status = LS_CO_STOPPED;
+                               break;
+                       default:
+                               CERROR("%s: unknown status: rc = %d\n",
+                                      lfsck_lfsck2name(lfsck),
+                                      lfsck->li_status);
+                               lr->lr_status = LS_CO_FAILED;
+                               break;
+                       }
                }
        } else {
-               lr->lr_event = LE_STOP;
-               flags = 0;
-               lr->lr_status = LS_CO_FAILED;
+               if (lfsck->li_flags & LPF_ALL_TGT) {
+                       lr->lr_event = LE_STOP;
+                       lr->lr_status = LS_FAILED;
+               } else {
+                       lr->lr_event = LE_PEER_EXIT;
+                       lr->lr_status = LS_CO_FAILED;
+               }
        }
 
-       rc1 = lfsck_layout_master_notify_others(env, com, lr, flags);
+       rc1 = lfsck_layout_master_notify_others(env, com, lr);
        if (rc1 != 0) {
                CERROR("%s: failed to notify others for layout quit: rc = %d\n",
                       lfsck_lfsck2name(lfsck), rc1);
@@ -1473,7 +3700,7 @@ cleanup2:
        /* Under force exit case, some requests may be just freed without
         * verification, those objects should be re-handled when next run.
         * So not update the on-disk tracing file under such case. */
-       if (!llmd->llmd_exit)
+       if (llmd->llmd_in_double_scan && !llmd->llmd_exit)
                rc1 = lfsck_layout_double_scan_result(env, com, rc);
 
 fini:
@@ -1599,7 +3826,6 @@ lfsck_layout_slave_query_master(const struct lu_env *env,
        struct lfsck_layout_slave_target *llst;
        struct obd_export                *exp;
        struct ptlrpc_request_set        *set;
-       int                               cnt   = 0;
        int                               rc    = 0;
        int                               rc1   = 0;
        ENTRY;
@@ -1646,15 +3872,12 @@ lfsck_layout_slave_query_master(const struct lu_env *env,
                        rc1 = rc;
                        lfsck_layout_llst_put(llst);
                        class_export_put(exp);
-               } else {
-                       cnt++;
                }
                spin_lock(&llsd->llsd_lock);
        }
        spin_unlock(&llsd->llsd_lock);
 
-       if (cnt > 0)
-               rc = ptlrpc_set_wait(set);
+       rc = ptlrpc_set_wait(set);
        ptlrpc_set_destroy(set);
 
        RETURN(rc1 != 0 ? rc1 : rc);
@@ -1671,7 +3894,6 @@ lfsck_layout_slave_notify_master(const struct lu_env *env,
        struct lfsck_layout_slave_target *llst;
        struct obd_export                *exp;
        struct ptlrpc_request_set        *set;
-       int                               cnt   = 0;
        int                               rc;
        ENTRY;
 
@@ -1679,56 +3901,255 @@ lfsck_layout_slave_notify_master(const struct lu_env *env,
        if (set == NULL)
                RETURN_EXIT;
 
-       memset(lr, 0, sizeof(*lr));
-       lr->lr_event = event;
-       lr->lr_flags = LEF_FROM_OST;
-       lr->lr_status = result;
-       lr->lr_index = lfsck_dev_idx(lfsck->li_bottom);
-       lr->lr_active = LT_LAYOUT;
-       llsd->llsd_touch_gen++;
-       spin_lock(&llsd->llsd_lock);
-       while (!list_empty(&llsd->llsd_master_list)) {
-               llst = list_entry(llsd->llsd_master_list.next,
-                                 struct lfsck_layout_slave_target,
-                                 llst_list);
-               if (llst->llst_gen == llsd->llsd_touch_gen)
-                       break;
+       memset(lr, 0, sizeof(*lr));
+       lr->lr_event = event;
+       lr->lr_flags = LEF_FROM_OST;
+       lr->lr_status = result;
+       lr->lr_index = lfsck_dev_idx(lfsck->li_bottom);
+       lr->lr_active = LT_LAYOUT;
+       llsd->llsd_touch_gen++;
+       spin_lock(&llsd->llsd_lock);
+       while (!list_empty(&llsd->llsd_master_list)) {
+               llst = list_entry(llsd->llsd_master_list.next,
+                                 struct lfsck_layout_slave_target,
+                                 llst_list);
+               if (llst->llst_gen == llsd->llsd_touch_gen)
+                       break;
+
+               llst->llst_gen = llsd->llsd_touch_gen;
+               list_del(&llst->llst_list);
+               list_add_tail(&llst->llst_list,
+                             &llsd->llsd_master_list);
+               atomic_inc(&llst->llst_ref);
+               spin_unlock(&llsd->llsd_lock);
+
+               exp = lustre_find_lwp_by_index(lfsck->li_obd->obd_name,
+                                              llst->llst_index);
+               if (exp == NULL) {
+                       lfsck_layout_llst_del(llsd, llst);
+                       lfsck_layout_llst_put(llst);
+                       spin_lock(&llsd->llsd_lock);
+                       continue;
+               }
+
+               rc = lfsck_layout_async_notify(env, exp, lr, set);
+               if (rc != 0)
+                       CERROR("%s: slave fail to notify %s for layout: "
+                              "rc = %d\n", lfsck_lfsck2name(lfsck),
+                              exp->exp_obd->obd_name, rc);
+               lfsck_layout_llst_put(llst);
+               class_export_put(exp);
+               spin_lock(&llsd->llsd_lock);
+       }
+       spin_unlock(&llsd->llsd_lock);
+
+       ptlrpc_set_wait(set);
+       ptlrpc_set_destroy(set);
+
+       RETURN_EXIT;
+}
+
+/*
+ * \ret -ENODATA: unrecognized stripe
+ * \ret = 0     : recognized stripe
+ * \ret < 0     : other failures
+ */
+static int lfsck_layout_master_check_pairs(const struct lu_env *env,
+                                          struct lfsck_component *com,
+                                          struct lu_fid *cfid,
+                                          struct lu_fid *pfid)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct lu_buf                   *buf    = &info->lti_big_buf;
+       struct ost_id                   *oi     = &info->lti_oi;
+       struct dt_object                *obj;
+       struct lov_mds_md_v1            *lmm;
+       struct lov_ost_data_v1          *objs;
+       __u32                            idx    = pfid->f_stripe_idx;
+       __u32                            magic;
+       int                              rc     = 0;
+       int                              i;
+       __u16                            count;
+       ENTRY;
+
+       pfid->f_ver = 0;
+       obj = lfsck_object_find_by_dev(env, com->lc_lfsck->li_bottom, pfid);
+       if (IS_ERR(obj))
+               RETURN(PTR_ERR(obj));
+
+       dt_read_lock(env, obj, 0);
+       if (unlikely(!dt_object_exists(obj)))
+               GOTO(unlock, rc = -ENOENT);
+
+       rc = lfsck_layout_get_lovea(env, obj, buf, NULL);
+       if (rc < 0)
+               GOTO(unlock, rc);
+
+       if (rc == 0)
+               GOTO(unlock, rc = -ENODATA);
+
+       lmm = buf->lb_buf;
+       rc = lfsck_layout_verify_header(lmm);
+       if (rc != 0)
+               GOTO(unlock, rc);
+
+       /* Currently, we only support LOV_MAGIC_V1/LOV_MAGIC_V3 which has
+        * been verified in lfsck_layout_verify_header() already. If some
+        * new magic introduced in the future, then layout LFSCK needs to
+        * be updated also. */
+       magic = le32_to_cpu(lmm->lmm_magic);
+       if (magic == LOV_MAGIC_V1) {
+               objs = &lmm->lmm_objects[0];
+       } else {
+               LASSERT(magic == LOV_MAGIC_V3);
+               objs = &((struct lov_mds_md_v3 *)lmm)->lmm_objects[0];
+       }
+
+       fid_to_ostid(cfid, oi);
+       count = le16_to_cpu(lmm->lmm_stripe_count);
+       for (i = 0; i < count; i++, objs++) {
+               struct ost_id oi2;
+
+               ostid_le_to_cpu(&objs->l_ost_oi, &oi2);
+               if (memcmp(oi, &oi2, sizeof(*oi)) == 0)
+                       GOTO(unlock, rc = (i != idx ? -ENODATA : 0));
+       }
+
+       GOTO(unlock, rc = -ENODATA);
+
+unlock:
+       dt_read_unlock(env, obj);
+       lu_object_put(env, &obj->do_lu);
+
+       return rc;
+}
+
+/*
+ * The LFSCK-on-OST will ask the LFSCK-on-MDT to check whether the given
+ * MDT-object/OST-object pairs match or not to aviod transfer MDT-object
+ * layout EA from MDT to OST. On one hand, the OST no need to understand
+ * the layout EA structure; on the other hand, it may cause trouble when
+ * transfer large layout EA from MDT to OST via normal OUT RPC.
+ *
+ * \ret > 0: unrecognized stripe
+ * \ret = 0: recognized stripe
+ * \ret < 0: other failures
+ */
+static int lfsck_layout_slave_check_pairs(const struct lu_env *env,
+                                         struct lfsck_component *com,
+                                         struct lu_fid *cfid,
+                                         struct lu_fid *pfid)
+{
+       struct lfsck_instance    *lfsck  = com->lc_lfsck;
+       struct obd_device        *obd    = lfsck->li_obd;
+       struct seq_server_site   *ss     =
+                       lu_site2seq(lfsck->li_bottom->dd_lu_dev.ld_site);
+       struct obd_export        *exp    = NULL;
+       struct ptlrpc_request    *req    = NULL;
+       struct lfsck_request     *lr;
+       struct lu_seq_range       range  = { 0 };
+       int                       rc     = 0;
+       ENTRY;
+
+       if (unlikely(fid_is_idif(pfid)))
+               RETURN(1);
+
+       fld_range_set_any(&range);
+       rc = fld_server_lookup(env, ss->ss_server_fld, fid_seq(pfid), &range);
+       if (rc != 0)
+               RETURN(rc == -ENOENT ? 1 : rc);
+
+       if (unlikely(!fld_range_is_mdt(&range)))
+               RETURN(1);
+
+       exp = lustre_find_lwp_by_index(obd->obd_name, range.lsr_index);
+       if (unlikely(exp == NULL))
+               RETURN(1);
+
+       if (!(exp_connect_flags(exp) & OBD_CONNECT_LFSCK))
+               GOTO(out, rc = -EOPNOTSUPP);
+
+       req = ptlrpc_request_alloc(class_exp2cliimp(exp), &RQF_LFSCK_NOTIFY);
+       if (req == NULL)
+               GOTO(out, rc = -ENOMEM);
+
+       rc = ptlrpc_request_pack(req, LUSTRE_OBD_VERSION, LFSCK_NOTIFY);
+       if (rc != 0) {
+               ptlrpc_request_free(req);
+
+               GOTO(out, rc);
+       }
+
+       lr = req_capsule_client_get(&req->rq_pill, &RMF_LFSCK_REQUEST);
+       memset(lr, 0, sizeof(*lr));
+       lr->lr_event = LE_PAIRS_VERIFY;
+       lr->lr_active = LT_LAYOUT;
+       lr->lr_fid = *cfid; /* OST-object itself FID. */
+       lr->lr_fid2 = *pfid; /* The claimed parent FID. */
+
+       ptlrpc_request_set_replen(req);
+       rc = ptlrpc_queue_wait(req);
+       ptlrpc_req_finished(req);
+
+       if (rc == -ENOENT || rc == -ENODATA)
+               rc = 1;
+
+       GOTO(out, rc);
+
+out:
+       if (exp != NULL)
+               class_export_put(exp);
+
+       return rc;
+}
+
+static int lfsck_layout_slave_repair_pfid(const struct lu_env *env,
+                                         struct lfsck_component *com,
+                                         struct lfsck_request *lr)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct filter_fid               *ff     = &info->lti_new_pfid;
+       struct lu_buf                   *buf;
+       struct dt_device                *dev    = com->lc_lfsck->li_bottom;
+       struct dt_object                *obj;
+       struct thandle                  *th     = NULL;
+       int                              rc     = 0;
+       ENTRY;
+
+       obj = lfsck_object_find_by_dev(env, dev, &lr->lr_fid);
+       if (IS_ERR(obj))
+               RETURN(PTR_ERR(obj));
+
+       fid_cpu_to_le(&ff->ff_parent, &lr->lr_fid2);
+       buf = lfsck_buf_get(env, ff, sizeof(*ff));
+       dt_write_lock(env, obj, 0);
+       if (unlikely(!dt_object_exists(obj)))
+               GOTO(unlock, rc = 0);
+
+       th = dt_trans_create(env, dev);
+       if (IS_ERR(th))
+               GOTO(unlock, rc = PTR_ERR(th));
 
-               llst->llst_gen = llsd->llsd_touch_gen;
-               list_del(&llst->llst_list);
-               list_add_tail(&llst->llst_list,
-                             &llsd->llsd_master_list);
-               atomic_inc(&llst->llst_ref);
-               spin_unlock(&llsd->llsd_lock);
+       rc = dt_declare_xattr_set(env, obj, buf, XATTR_NAME_FID, 0, th);
+       if (rc != 0)
+               GOTO(stop, rc);
 
-               exp = lustre_find_lwp_by_index(lfsck->li_obd->obd_name,
-                                              llst->llst_index);
-               if (exp == NULL) {
-                       lfsck_layout_llst_del(llsd, llst);
-                       lfsck_layout_llst_put(llst);
-                       spin_lock(&llsd->llsd_lock);
-                       continue;
-               }
+       rc = dt_trans_start_local(env, dev, th);
+       if (rc != 0)
+               GOTO(stop, rc);
 
-               rc = lfsck_layout_async_notify(env, exp, lr, set);
-               if (rc != 0)
-                       CERROR("%s: slave fail to notify %s for layout: "
-                              "rc = %d\n", lfsck_lfsck2name(lfsck),
-                              exp->exp_obd->obd_name, rc);
-               else
-                       cnt++;
-               lfsck_layout_llst_put(llst);
-               class_export_put(exp);
-               spin_lock(&llsd->llsd_lock);
-       }
-       spin_unlock(&llsd->llsd_lock);
+       rc = dt_xattr_set(env, obj, buf, XATTR_NAME_FID, 0, th, BYPASS_CAPA);
 
-       if (cnt > 0)
-               rc = ptlrpc_set_wait(set);
+       GOTO(stop, rc);
 
-       ptlrpc_set_destroy(set);
+stop:
+       dt_trans_stop(env, dev, th);
 
-       RETURN_EXIT;
+unlock:
+       dt_write_unlock(env, obj);
+       lu_object_put(env, &obj->do_lu);
+
+       return rc;
 }
 
 /* layout APIs */
@@ -1768,14 +4189,7 @@ static void lfsck_layout_fail(const struct lu_env *env,
        down_write(&com->lc_sem);
        if (new_checked)
                com->lc_new_checked++;
-       lo->ll_objs_failed_phase1++;
-       if (lo->ll_pos_first_inconsistent == 0) {
-               struct lfsck_instance *lfsck = com->lc_lfsck;
-
-               lo->ll_pos_first_inconsistent =
-                       lfsck->li_obj_oit->do_index_ops->dio_it.store(env,
-                                                       lfsck->li_di_oit);
-       }
+       lfsck_layout_record_failure(env, com->lc_lfsck, lo);
        up_write(&com->lc_sem);
 }
 
@@ -1853,7 +4267,8 @@ static int lfsck_layout_slave_checkpoint(const struct lu_env *env,
 }
 
 static int lfsck_layout_prep(const struct lu_env *env,
-                            struct lfsck_component *com)
+                            struct lfsck_component *com,
+                            struct lfsck_start *start)
 {
        struct lfsck_instance   *lfsck  = com->lc_lfsck;
        struct lfsck_layout     *lo     = com->lc_file_ram;
@@ -1862,18 +4277,21 @@ static int lfsck_layout_prep(const struct lu_env *env,
        fid_zero(&pos->lp_dir_parent);
        pos->lp_dir_cookie = 0;
        if (lo->ll_status == LS_COMPLETED ||
-           lo->ll_status == LS_PARTIAL) {
+           lo->ll_status == LS_PARTIAL ||
+           /* To handle orphan, must scan from the beginning. */
+           (start != NULL && start->ls_flags & LPF_ORPHAN)) {
                int rc;
 
                rc = lfsck_layout_reset(env, com, false);
+               if (rc == 0)
+                       rc = lfsck_set_param(env, lfsck, start, true);
+
                if (rc != 0)
                        return rc;
        }
 
        down_write(&com->lc_sem);
-
        lo->ll_time_latest_start = cfs_time_current_sec();
-
        spin_lock(&lfsck->li_lock);
        if (lo->ll_flags & LF_SCANNED_ONCE) {
                if (!lfsck->li_drop_dryrun ||
@@ -1897,6 +4315,7 @@ static int lfsck_layout_prep(const struct lu_env *env,
                                lo->ll_objs_repaired[i] = 0;
 
                        pos->lp_oit_cookie = lo->ll_pos_first_inconsistent;
+                       fid_zero(&com->lc_fid_latest_scanned_phase2);
                }
        } else {
                lo->ll_status = LS_SCANNING_PHASE1;
@@ -1907,7 +4326,6 @@ static int lfsck_layout_prep(const struct lu_env *env,
                        pos->lp_oit_cookie = lo->ll_pos_first_inconsistent;
        }
        spin_unlock(&lfsck->li_lock);
-
        up_write(&com->lc_sem);
 
        return 0;
@@ -1917,19 +4335,35 @@ static int lfsck_layout_slave_prep(const struct lu_env *env,
                                   struct lfsck_component *com,
                                   struct lfsck_start_param *lsp)
 {
-       struct lfsck_layout             *lo     = com->lc_file_ram;
        struct lfsck_layout_slave_data  *llsd   = com->lc_data;
+       struct lfsck_instance           *lfsck  = com->lc_lfsck;
+       struct lfsck_layout             *lo     = com->lc_file_ram;
+       struct lfsck_start              *start  = lsp->lsp_start;
        int                              rc;
 
-       /* XXX: For a new scanning, generate OST-objects
-        *      bitmap for orphan detection. */
-
-       rc = lfsck_layout_prep(env, com);
-       if (rc != 0 || lo->ll_status != LS_SCANNING_PHASE1 ||
-           !lsp->lsp_index_valid)
+       rc = lfsck_layout_prep(env, com, start);
+       if (rc != 0)
                return rc;
 
+       if (lo->ll_flags & LF_CRASHED_LASTID &&
+           list_empty(&llsd->llsd_master_list)) {
+               LASSERT(lfsck->li_out_notify != NULL);
+
+               lfsck->li_out_notify(env, lfsck->li_out_notify_data,
+                                    LE_LASTID_REBUILDING);
+       }
+
+       if (!lsp->lsp_index_valid)
+               return 0;
+
        rc = lfsck_layout_llst_add(llsd, lsp->lsp_index);
+       if (rc == 0 && start != NULL && start->ls_flags & LPF_ORPHAN) {
+               LASSERT(!llsd->llsd_rbtree_valid);
+
+               write_lock(&llsd->llsd_rb_lock);
+               rc = lfsck_rbtree_setup(env, com);
+               write_unlock(&llsd->llsd_rb_lock);
+       }
 
        return rc;
 }
@@ -1943,10 +4377,11 @@ static int lfsck_layout_master_prep(const struct lu_env *env,
        struct ptlrpc_thread            *mthread = &lfsck->li_thread;
        struct ptlrpc_thread            *athread = &llmd->llmd_thread;
        struct lfsck_thread_args        *lta;
-       long                             rc;
+       struct task_struct              *task;
+       int                              rc;
        ENTRY;
 
-       rc = lfsck_layout_prep(env, com);
+       rc = lfsck_layout_prep(env, com, lsp->lsp_start);
        if (rc != 0)
                RETURN(rc);
 
@@ -1962,10 +4397,11 @@ static int lfsck_layout_master_prep(const struct lu_env *env,
        if (IS_ERR(lta))
                RETURN(PTR_ERR(lta));
 
-       rc = PTR_ERR(kthread_run(lfsck_layout_assistant, lta, "lfsck_layout"));
-       if (IS_ERR_VALUE(rc)) {
+       task = kthread_run(lfsck_layout_assistant, lta, "lfsck_layout");
+       if (IS_ERR(task)) {
+               rc = PTR_ERR(task);
                CERROR("%s: Cannot start LFSCK layout assistant thread: "
-                      "rc = %ld\n", lfsck_lfsck2name(lfsck), rc);
+                      "rc = %d\n", lfsck_lfsck2name(lfsck), rc);
                lfsck_thread_args_fini(lta);
        } else {
                struct l_wait_info lwi = { 0 };
@@ -1983,23 +4419,288 @@ static int lfsck_layout_master_prep(const struct lu_env *env,
        RETURN(rc);
 }
 
+/* Pre-fetch the attribute for each stripe in the given layout EA. */
+static int lfsck_layout_scan_stripes(const struct lu_env *env,
+                                    struct lfsck_component *com,
+                                    struct dt_object *parent,
+                                    struct lov_mds_md_v1 *lmm)
+{
+       struct lfsck_thread_info        *info    = lfsck_env_info(env);
+       struct lfsck_instance           *lfsck   = com->lc_lfsck;
+       struct lfsck_bookmark           *bk      = &lfsck->li_bookmark_ram;
+       struct lfsck_layout             *lo      = com->lc_file_ram;
+       struct lfsck_layout_master_data *llmd    = com->lc_data;
+       struct lfsck_layout_object      *llo     = NULL;
+       struct lov_ost_data_v1          *objs;
+       struct lfsck_tgt_descs          *ltds    = &lfsck->li_ost_descs;
+       struct ptlrpc_thread            *mthread = &lfsck->li_thread;
+       struct ptlrpc_thread            *athread = &llmd->llmd_thread;
+               struct l_wait_info       lwi     = { 0 };
+       struct lu_buf                   *buf;
+       int                              rc      = 0;
+       int                              i;
+       __u32                            magic;
+       __u16                            count;
+       __u16                            gen;
+       ENTRY;
+
+       buf = lfsck_buf_get(env, &info->lti_old_pfid,
+                           sizeof(struct filter_fid_old));
+       count = le16_to_cpu(lmm->lmm_stripe_count);
+       gen = le16_to_cpu(lmm->lmm_layout_gen);
+       /* Currently, we only support LOV_MAGIC_V1/LOV_MAGIC_V3 which has
+        * been verified in lfsck_layout_verify_header() already. If some
+        * new magic introduced in the future, then layout LFSCK needs to
+        * be updated also. */
+       magic = le32_to_cpu(lmm->lmm_magic);
+       if (magic == LOV_MAGIC_V1) {
+               objs = &lmm->lmm_objects[0];
+       } else {
+               LASSERT(magic == LOV_MAGIC_V3);
+               objs = &((struct lov_mds_md_v3 *)lmm)->lmm_objects[0];
+       }
+
+       for (i = 0; i < count; i++, objs++) {
+               struct lu_fid           *fid    = &info->lti_fid;
+               struct ost_id           *oi     = &info->lti_oi;
+               struct lfsck_layout_req *llr;
+               struct lfsck_tgt_desc   *tgt    = NULL;
+               struct dt_object        *cobj   = NULL;
+               __u32                    index  =
+                                       le32_to_cpu(objs->l_ost_idx);
+               bool                     wakeup = false;
+
+               if (unlikely(lovea_slot_is_dummy(objs)))
+                       continue;
+
+               l_wait_event(mthread->t_ctl_waitq,
+                            bk->lb_async_windows == 0 ||
+                            llmd->llmd_prefetched < bk->lb_async_windows ||
+                            !thread_is_running(mthread) ||
+                            thread_is_stopped(athread),
+                            &lwi);
+
+               if (unlikely(!thread_is_running(mthread)) ||
+                            thread_is_stopped(athread))
+                       GOTO(out, rc = 0);
+
+               ostid_le_to_cpu(&objs->l_ost_oi, oi);
+               ostid_to_fid(fid, oi, index);
+               tgt = lfsck_tgt_get(ltds, index);
+               if (unlikely(tgt == NULL)) {
+                       CERROR("%s: Cannot talk with OST %x which did not join "
+                              "the layout LFSCK.\n",
+                              lfsck_lfsck2name(lfsck), index);
+                       lo->ll_flags |= LF_INCOMPLETE;
+                       goto next;
+               }
+
+               cobj = lfsck_object_find_by_dev(env, tgt->ltd_tgt, fid);
+               if (IS_ERR(cobj)) {
+                       rc = PTR_ERR(cobj);
+                       goto next;
+               }
+
+               rc = dt_declare_attr_get(env, cobj, BYPASS_CAPA);
+               if (rc != 0)
+                       goto next;
+
+               rc = dt_declare_xattr_get(env, cobj, buf, XATTR_NAME_FID,
+                                         BYPASS_CAPA);
+               if (rc != 0)
+                       goto next;
+
+               if (llo == NULL) {
+                       llo = lfsck_layout_object_init(env, parent, gen);
+                       if (IS_ERR(llo)) {
+                               rc = PTR_ERR(llo);
+                               goto next;
+                       }
+               }
+
+               llr = lfsck_layout_req_init(llo, cobj, index, i);
+               if (IS_ERR(llr)) {
+                       rc = PTR_ERR(llr);
+                       goto next;
+               }
+
+               cobj = NULL;
+               spin_lock(&llmd->llmd_lock);
+               if (llmd->llmd_assistant_status < 0) {
+                       spin_unlock(&llmd->llmd_lock);
+                       lfsck_layout_req_fini(env, llr);
+                       lfsck_tgt_put(tgt);
+                       RETURN(llmd->llmd_assistant_status);
+               }
+
+               list_add_tail(&llr->llr_list, &llmd->llmd_req_list);
+               if (llmd->llmd_prefetched == 0)
+                       wakeup = true;
+
+               llmd->llmd_prefetched++;
+               spin_unlock(&llmd->llmd_lock);
+               if (wakeup)
+                       wake_up_all(&athread->t_ctl_waitq);
+
+next:
+               down_write(&com->lc_sem);
+               com->lc_new_checked++;
+               if (rc < 0)
+                       lfsck_layout_record_failure(env, lfsck, lo);
+               up_write(&com->lc_sem);
+
+               if (cobj != NULL && !IS_ERR(cobj))
+                       lu_object_put(env, &cobj->do_lu);
+
+               if (likely(tgt != NULL))
+                       lfsck_tgt_put(tgt);
+
+               if (rc < 0 && bk->lb_param & LPF_FAILOUT)
+                       GOTO(out, rc);
+       }
+
+       GOTO(out, rc = 0);
+
+out:
+       if (llo != NULL && !IS_ERR(llo))
+               lfsck_layout_object_put(env, llo);
+
+       return rc;
+}
+
+/* For the given object, read its layout EA locally. For each stripe, pre-fetch
+ * the OST-object's attribute and generate an structure lfsck_layout_req on the
+ * list ::llmd_req_list.
+ *
+ * For each request on above list, the lfsck_layout_assistant thread compares
+ * the OST side attribute with local attribute, if inconsistent, then repair it.
+ *
+ * All above processing is async mode with pipeline. */
 static int lfsck_layout_master_exec_oit(const struct lu_env *env,
                                        struct lfsck_component *com,
                                        struct dt_object *obj)
 {
-       /* XXX: To be implemented in other patches.
-        *
-        * For the given object, read its layout EA locally. For each stripe,
-        * pre-fetch the OST-object's attribute and generate an structure
-        * lfsck_layout_req on the list ::llmd_req_list.
-        *
-        * For each request on the ::llmd_req_list, the lfsck_layout_assistant
-        * thread will compare the OST side attribute with local attribute,
-        * if inconsistent, then repair it.
-        *
-        * All above processing is async mode with pipeline. */
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct ost_id                   *oi     = &info->lti_oi;
+       struct lfsck_layout             *lo     = com->lc_file_ram;
+       struct lfsck_layout_master_data *llmd   = com->lc_data;
+       struct lfsck_instance           *lfsck  = com->lc_lfsck;
+       struct lfsck_bookmark           *bk     = &lfsck->li_bookmark_ram;
+       struct thandle                  *handle = NULL;
+       struct lu_buf                   *buf    = &info->lti_big_buf;
+       struct lov_mds_md_v1            *lmm    = NULL;
+       struct dt_device                *dev    = lfsck->li_bottom;
+       struct lustre_handle             lh     = { 0 };
+       ssize_t                          buflen = buf->lb_len;
+       int                              rc     = 0;
+       bool                             locked = false;
+       bool                             stripe = false;
+       ENTRY;
 
-       return 0;
+       if (!S_ISREG(lfsck_object_type(obj)))
+               GOTO(out, rc = 0);
+
+       if (llmd->llmd_assistant_status < 0)
+               GOTO(out, rc = -ESRCH);
+
+       fid_to_lmm_oi(lfsck_dto2fid(obj), oi);
+       lmm_oi_cpu_to_le(oi, oi);
+       dt_read_lock(env, obj, 0);
+       locked = true;
+
+again:
+       rc = lfsck_layout_get_lovea(env, obj, buf, &buflen);
+       if (rc <= 0)
+               GOTO(out, rc);
+
+       buf->lb_len = rc;
+       lmm = buf->lb_buf;
+       rc = lfsck_layout_verify_header(lmm);
+       /* If the LOV EA crashed, then it is possible to be rebuilt later
+        * when handle orphan OST-objects. */
+       if (rc != 0)
+               GOTO(out, rc);
+
+       if (memcmp(oi, &lmm->lmm_oi, sizeof(*oi)) == 0)
+               GOTO(out, stripe = true);
+
+       /* Inconsistent lmm_oi, should be repaired. */
+       CDEBUG(D_LFSCK, "Repair bad lmm_oi for "DFID"\n",
+              PFID(lfsck_dto2fid(obj)));
+
+       if (bk->lb_param & LPF_DRYRUN) {
+               down_write(&com->lc_sem);
+               lo->ll_objs_repaired[LLIT_OTHERS - 1]++;
+               up_write(&com->lc_sem);
+
+               GOTO(out, stripe = true);
+       }
+
+       if (!lustre_handle_is_used(&lh)) {
+               dt_read_unlock(env, obj);
+               locked = false;
+               buf->lb_len = buflen;
+               rc = lfsck_layout_lock(env, com, obj, &lh,
+                                      MDS_INODELOCK_LAYOUT |
+                                      MDS_INODELOCK_XATTR);
+               if (rc != 0)
+                       GOTO(out, rc);
+
+               handle = dt_trans_create(env, dev);
+               if (IS_ERR(handle))
+                       GOTO(out, rc = PTR_ERR(handle));
+
+               rc = dt_declare_xattr_set(env, obj, buf, XATTR_NAME_LOV,
+                                         LU_XATTR_REPLACE, handle);
+               if (rc != 0)
+                       GOTO(out, rc);
+
+               rc = dt_trans_start_local(env, dev, handle);
+               if (rc != 0)
+                       GOTO(out, rc);
+
+               dt_write_lock(env, obj, 0);
+               locked = true;
+
+               goto again;
+       }
+
+       lmm->lmm_oi = *oi;
+       rc = dt_xattr_set(env, obj, buf, XATTR_NAME_LOV,
+                         LU_XATTR_REPLACE, handle, BYPASS_CAPA);
+       if (rc != 0)
+               GOTO(out, rc);
+
+       down_write(&com->lc_sem);
+       lo->ll_objs_repaired[LLIT_OTHERS - 1]++;
+       up_write(&com->lc_sem);
+
+       GOTO(out, stripe = true);
+
+out:
+       if (locked) {
+               if (lustre_handle_is_used(&lh))
+                       dt_write_unlock(env, obj);
+               else
+                       dt_read_unlock(env, obj);
+       }
+
+       if (handle != NULL && !IS_ERR(handle))
+               dt_trans_stop(env, dev, handle);
+
+       lfsck_layout_unlock(&lh);
+       if (stripe) {
+               rc = lfsck_layout_scan_stripes(env, com, obj, lmm);
+       } else {
+               down_write(&com->lc_sem);
+               com->lc_new_checked++;
+               if (rc < 0)
+                       lfsck_layout_record_failure(env, lfsck, lo);
+               up_write(&com->lc_sem);
+       }
+       buf->lb_len = buflen;
+
+       return rc;
 }
 
 static int lfsck_layout_slave_exec_oit(const struct lu_env *env,
@@ -2016,10 +4717,21 @@ static int lfsck_layout_slave_exec_oit(const struct lu_env *env,
        int                              rc;
        ENTRY;
 
-       /* XXX: Update OST-objects bitmap for orphan detection. */
-
        LASSERT(llsd != NULL);
 
+       if (OBD_FAIL_CHECK(OBD_FAIL_LFSCK_DELAY5) &&
+           cfs_fail_val == lfsck_dev_idx(lfsck->li_bottom)) {
+               struct l_wait_info       lwi = LWI_TIMEOUT(cfs_time_seconds(1),
+                                                          NULL, NULL);
+               struct ptlrpc_thread    *thread = &lfsck->li_thread;
+
+               l_wait_event(thread->t_ctl_waitq,
+                            !thread_is_running(thread),
+                            &lwi);
+       }
+
+       lfsck_rbtree_update_bitmap(env, com, fid, false);
+
        down_write(&com->lc_sem);
        if (fid_is_idif(fid))
                seq = 0;
@@ -2230,6 +4942,9 @@ static int lfsck_layout_slave_post(const struct lu_env *env,
 
        lfsck_layout_slave_notify_master(env, com, LE_PHASE1_DONE, result);
 
+       if (result <= 0)
+               lfsck_rbtree_cleanup(env, com);
+
        return rc;
 }
 
@@ -2327,7 +5042,8 @@ static int lfsck_layout_dump(const struct lu_env *env,
                const struct dt_it_ops *iops;
                cfs_duration_t duration = cfs_time_current() -
                                          lfsck->li_time_last_checkpoint;
-               __u64 checked = lo->ll_objs_checked_phase1 + com->lc_new_checked;
+               __u64 checked = lo->ll_objs_checked_phase1 +
+                               com->lc_new_checked;
                __u64 speed = checked;
                __u64 new_checked = com->lc_new_checked * HZ;
                __u32 rtime = lo->ll_run_time_phase1 +
@@ -2375,8 +5091,47 @@ static int lfsck_layout_dump(const struct lu_env *env,
 
                buf += rc;
                len -= rc;
+       } else if (lo->ll_status == LS_SCANNING_PHASE2) {
+               cfs_duration_t duration = cfs_time_current() -
+                                         lfsck->li_time_last_checkpoint;
+               __u64 checked = lo->ll_objs_checked_phase2 +
+                               com->lc_new_checked;
+               __u64 speed1 = lo->ll_objs_checked_phase1;
+               __u64 speed2 = checked;
+               __u64 new_checked = com->lc_new_checked * HZ;
+               __u32 rtime = lo->ll_run_time_phase2 +
+                             cfs_duration_sec(duration + HALF_SEC);
+
+               if (duration != 0)
+                       do_div(new_checked, duration);
+               if (lo->ll_run_time_phase1 != 0)
+                       do_div(speed1, lo->ll_run_time_phase1);
+               if (rtime != 0)
+                       do_div(speed2, rtime);
+               rc = snprintf(buf, len,
+                             "checked_phase1: "LPU64"\n"
+                             "checked_phase2: "LPU64"\n"
+                             "run_time_phase1: %u seconds\n"
+                             "run_time_phase2: %u seconds\n"
+                             "average_speed_phase1: "LPU64" items/sec\n"
+                             "average_speed_phase2: "LPU64" items/sec\n"
+                             "real-time_speed_phase1: N/A\n"
+                             "real-time_speed_phase2: "LPU64" items/sec\n"
+                             "current_position: "DFID"\n",
+                             lo->ll_objs_checked_phase1,
+                             checked,
+                             lo->ll_run_time_phase1,
+                             rtime,
+                             speed1,
+                             speed2,
+                             new_checked,
+                             PFID(&com->lc_fid_latest_scanned_phase2));
+               if (rc <= 0)
+                       goto out;
+
+               buf += rc;
+               len -= rc;
        } else {
-               /* XXX: LS_SCANNING_PHASE2 will be handled in the future. */
                __u64 speed1 = lo->ll_objs_checked_phase1;
                __u64 speed2 = lo->ll_objs_checked_phase2;
 
@@ -2448,8 +5203,11 @@ static int lfsck_layout_slave_double_scan(const struct lu_env *env,
        int                              rc;
        ENTRY;
 
-       if (unlikely(lo->ll_status != LS_SCANNING_PHASE2))
+       if (unlikely(lo->ll_status != LS_SCANNING_PHASE2)) {
+               lfsck_rbtree_cleanup(env, com);
+               lfsck_layout_slave_notify_master(env, com, LE_PHASE2_DONE, 0);
                RETURN(0);
+       }
 
        atomic_inc(&lfsck->li_double_scan_count);
 
@@ -2492,6 +5250,8 @@ static int lfsck_layout_slave_double_scan(const struct lu_env *env,
 done:
        rc = lfsck_layout_double_scan_result(env, com, rc);
 
+       lfsck_rbtree_cleanup(env, com);
+       lfsck_layout_slave_notify_master(env, com, LE_PHASE2_DONE, rc);
        if (atomic_dec_and_test(&lfsck->li_double_scan_count))
                wake_up_all(&lfsck->li_thread.t_ctl_waitq);
 
@@ -2556,8 +5316,6 @@ static void lfsck_layout_slave_data_release(const struct lu_env *env,
 
        LASSERT(llsd != NULL);
 
-       com->lc_data = NULL;
-
        list_for_each_entry_safe(lls, next, &llsd->llsd_seq_list,
                                     lls_list) {
                list_del_init(&lls->lls_list);
@@ -2571,6 +5329,8 @@ static void lfsck_layout_slave_data_release(const struct lu_env *env,
                OBD_FREE_PTR(llst);
        }
 
+       lfsck_rbtree_cleanup(env, com);
+       com->lc_data = NULL;
        OBD_FREE_PTR(llsd);
 }
 
@@ -2590,6 +5350,12 @@ static void lfsck_layout_master_quit(const struct lu_env *env,
                     &lwi);
 }
 
+static void lfsck_layout_slave_quit(const struct lu_env *env,
+                                   struct lfsck_component *com)
+{
+       lfsck_rbtree_cleanup(env, com);
+}
+
 static int lfsck_layout_master_in_notify(const struct lu_env *env,
                                         struct lfsck_component *com,
                                         struct lfsck_request *lr)
@@ -2599,11 +5365,21 @@ static int lfsck_layout_master_in_notify(const struct lu_env *env,
        struct lfsck_layout_master_data *llmd  = com->lc_data;
        struct lfsck_tgt_descs          *ltds;
        struct lfsck_tgt_desc           *ltd;
+       bool                             fail  = false;
        ENTRY;
 
+       if (lr->lr_event == LE_PAIRS_VERIFY) {
+               int rc;
+
+               rc = lfsck_layout_master_check_pairs(env, com, &lr->lr_fid,
+                                                    &lr->lr_fid2);
+
+               RETURN(rc);
+       }
+
        if (lr->lr_event != LE_PHASE1_DONE &&
            lr->lr_event != LE_PHASE2_DONE &&
-           lr->lr_event != LE_STOP)
+           lr->lr_event != LE_PEER_EXIT)
                RETURN(-EINVAL);
 
        if (lr->lr_flags & LEF_FROM_OST)
@@ -2615,7 +5391,7 @@ static int lfsck_layout_master_in_notify(const struct lu_env *env,
        if (ltd == NULL) {
                spin_unlock(&ltds->ltd_lock);
 
-               RETURN(-ENODEV);
+               RETURN(-ENXIO);
        }
 
        list_del_init(&ltd->ltd_layout_phase_list);
@@ -2624,7 +5400,12 @@ static int lfsck_layout_master_in_notify(const struct lu_env *env,
                if (lr->lr_status <= 0) {
                        ltd->ltd_layout_done = 1;
                        list_del_init(&ltd->ltd_layout_list);
+                       CWARN("%s: %s %x failed/stopped at phase1: rc = %d.\n",
+                             lfsck_lfsck2name(lfsck),
+                             (lr->lr_flags & LEF_TO_OST) ? "OST" : "MDT",
+                             ltd->ltd_index, lr->lr_status);
                        lo->ll_flags |= LF_INCOMPLETE;
+                       fail = true;
                        break;
                }
 
@@ -2646,23 +5427,29 @@ static int lfsck_layout_master_in_notify(const struct lu_env *env,
                ltd->ltd_layout_done = 1;
                list_del_init(&ltd->ltd_layout_list);
                break;
-       case LE_STOP:
+       case LE_PEER_EXIT:
+               fail = true;
                ltd->ltd_layout_done = 1;
                list_del_init(&ltd->ltd_layout_list);
-               if (!(lr->lr_flags & LEF_FORCE_STOP))
+               if (!(lfsck->li_bookmark_ram.lb_param & LPF_FAILOUT)) {
+                       CWARN("%s: the peer %s %x exit layout LFSCK.\n",
+                             lfsck_lfsck2name(lfsck),
+                             (lr->lr_flags & LEF_TO_OST) ? "OST" : "MDT",
+                             ltd->ltd_index);
                        lo->ll_flags |= LF_INCOMPLETE;
+               }
                break;
        default:
                break;
        }
        spin_unlock(&ltds->ltd_lock);
 
-       if (lr->lr_flags & LEF_FORCE_STOP) {
+       if (fail && lfsck->li_bookmark_ram.lb_param & LPF_FAILOUT) {
                struct lfsck_stop *stop = &lfsck_env_info(env)->lti_stop;
 
                memset(stop, 0, sizeof(*stop));
                stop->ls_status = lr->lr_status;
-               stop->ls_flags = lr->lr_param;
+               stop->ls_flags = lr->lr_param & ~LPF_BROADCAST;
                lfsck_stop(env, lfsck->li_bottom, stop);
        } else if (lfsck_layout_master_to_orphan(llmd)) {
                wake_up_all(&llmd->llmd_thread.t_ctl_waitq);
@@ -2678,34 +5465,72 @@ static int lfsck_layout_slave_in_notify(const struct lu_env *env,
        struct lfsck_instance            *lfsck = com->lc_lfsck;
        struct lfsck_layout_slave_data   *llsd  = com->lc_data;
        struct lfsck_layout_slave_target *llst;
+       int                               rc;
        ENTRY;
 
-       if (lr->lr_event != LE_PHASE2_DONE &&
-           lr->lr_event != LE_STOP)
+       switch (lr->lr_event) {
+       case LE_FID_ACCESSED:
+               lfsck_rbtree_update_bitmap(env, com, &lr->lr_fid, true);
+               RETURN(0);
+       case LE_CONDITIONAL_DESTROY:
+               rc = lfsck_layout_slave_conditional_destroy(env, com, lr);
+               RETURN(rc);
+       case LE_PAIRS_VERIFY: {
+               lr->lr_status = LPVS_INIT;
+               /* Firstly, if the MDT-object which is claimed via OST-object
+                * local stored PFID xattr recognizes the OST-object, then it
+                * must be that the client given PFID is wrong. */
+               rc = lfsck_layout_slave_check_pairs(env, com, &lr->lr_fid,
+                                                   &lr->lr_fid3);
+               if (rc <= 0)
+                       RETURN(0);
+
+               lr->lr_status = LPVS_INCONSISTENT;
+               /* The OST-object local stored PFID xattr is stale. We need to
+                * check whether the MDT-object that is claimed via the client
+                * given PFID information recognizes the OST-object or not. If
+                * matches, then need to update the OST-object's PFID xattr. */
+               rc = lfsck_layout_slave_check_pairs(env, com, &lr->lr_fid,
+                                                   &lr->lr_fid2);
+               /* For rc < 0 case:
+                * We are not sure whether the client given PFID information
+                * is correct or not, do nothing to avoid improper fixing.
+                *
+                * For rc > 0 case:
+                * The client given PFID information is also invalid, we can
+                * NOT fix the OST-object inconsistency.
+                */
+               if (rc != 0)
+                       RETURN(rc);
+
+               lr->lr_status = LPVS_INCONSISTENT_TOFIX;
+               rc = lfsck_layout_slave_repair_pfid(env, com, lr);
+
+               RETURN(rc);
+       }
+       case LE_PHASE2_DONE:
+       case LE_PEER_EXIT:
+               break;
+       default:
                RETURN(-EINVAL);
+       }
 
-       llst = lfsck_layout_llst_find_and_del(llsd, lr->lr_index);
+       llst = lfsck_layout_llst_find_and_del(llsd, lr->lr_index, true);
        if (llst == NULL)
-               RETURN(-ENODEV);
+               RETURN(-ENXIO);
 
        lfsck_layout_llst_put(llst);
-       if (list_empty(&llsd->llsd_master_list)) {
-               switch (lr->lr_event) {
-               case LE_PHASE2_DONE:
-                       wake_up_all(&lfsck->li_thread.t_ctl_waitq);
-                       break;
-               case LE_STOP: {
-                       struct lfsck_stop *stop = &lfsck_env_info(env)->lti_stop;
+       if (list_empty(&llsd->llsd_master_list))
+               wake_up_all(&lfsck->li_thread.t_ctl_waitq);
 
-                       memset(stop, 0, sizeof(*stop));
-                       stop->ls_status = lr->lr_status;
-                       stop->ls_flags = lr->lr_param;
-                       lfsck_stop(env, lfsck->li_bottom, stop);
-                       break;
-               }
-               default:
-                       break;
-               }
+       if (lr->lr_event == LE_PEER_EXIT &&
+           lfsck->li_bookmark_ram.lb_param & LPF_FAILOUT) {
+               struct lfsck_stop *stop = &lfsck_env_info(env)->lti_stop;
+
+               memset(stop, 0, sizeof(*stop));
+               stop->ls_status = lr->lr_status;
+               stop->ls_flags = lr->lr_param & ~LPF_BROADCAST;
+               lfsck_stop(env, lfsck->li_bottom, stop);
        }
 
        RETURN(0);
@@ -2731,36 +5556,43 @@ static int lfsck_layout_master_stop_notify(const struct lu_env *env,
        struct lfsck_instance             *lfsck = com->lc_lfsck;
        int                                rc;
 
-       LASSERT(list_empty(&ltd->ltd_layout_list));
-       LASSERT(list_empty(&ltd->ltd_layout_phase_list));
+       spin_lock(&ltds->ltd_lock);
+       if (list_empty(&ltd->ltd_layout_list)) {
+               LASSERT(list_empty(&ltd->ltd_layout_phase_list));
+               spin_unlock(&ltds->ltd_lock);
+
+               return 0;
+       }
+
+       list_del_init(&ltd->ltd_layout_phase_list);
+       list_del_init(&ltd->ltd_layout_list);
+       spin_unlock(&ltds->ltd_lock);
 
        memset(lr, 0, sizeof(*lr));
        lr->lr_index = lfsck_dev_idx(lfsck->li_bottom);
-       lr->lr_event = LE_STOP;
+       lr->lr_event = LE_PEER_EXIT;
        lr->lr_active = LT_LAYOUT;
-       if (ltds == &lfsck->li_ost_descs) {
+       lr->lr_status = LS_CO_PAUSED;
+       if (ltds == &lfsck->li_ost_descs)
                lr->lr_flags = LEF_TO_OST;
-       } else {
-               if (ltd->ltd_index == lfsck_dev_idx(lfsck->li_bottom))
-                       return 0;
-
-               lr->lr_flags = 0;
-       }
-       lr->lr_status = LS_CO_STOPPED;
 
        laia->laia_com = com;
        laia->laia_ltds = ltds;
+       atomic_inc(&ltd->ltd_ref);
        laia->laia_ltd = ltd;
        laia->laia_lr = lr;
+       laia->laia_shared = 0;
 
        rc = lfsck_async_request(env, ltd->ltd_exp, lr, set,
                                 lfsck_layout_master_async_interpret,
                                 laia, LFSCK_NOTIFY);
-       if (rc != 0)
+       if (rc != 0) {
                CERROR("%s: Fail to notify %s %x for co-stop: rc = %d\n",
                       lfsck_lfsck2name(lfsck),
                       (lr->lr_flags & LEF_TO_OST) ? "OST" : "MDT",
                       ltd->ltd_index, rc);
+               lfsck_tgt_put(ltd);
+       }
 
        return rc;
 }
@@ -2778,7 +5610,8 @@ static int lfsck_layout_slave_join(const struct lu_env *env,
        ENTRY;
 
        if (!lsp->lsp_index_valid || start == NULL ||
-           !(start->ls_flags & LPF_ALL_MDT))
+           !(start->ls_flags & LPF_ALL_TGT) ||
+           !(lfsck->li_bookmark_ram.lb_param & LPF_ALL_TGT))
                RETURN(-EALREADY);
 
        spin_unlock(&lfsck->li_lock);
@@ -2786,7 +5619,8 @@ static int lfsck_layout_slave_join(const struct lu_env *env,
        spin_lock(&lfsck->li_lock);
        if (rc == 0 && !thread_is_running(&lfsck->li_thread)) {
                spin_unlock(&lfsck->li_lock);
-               llst = lfsck_layout_llst_find_and_del(llsd, lsp->lsp_index);
+               llst = lfsck_layout_llst_find_and_del(llsd, lsp->lsp_index,
+                                                     true);
                if (llst != NULL)
                        lfsck_layout_llst_put(llst);
                spin_lock(&lfsck->li_lock);
@@ -2804,6 +5638,7 @@ static struct lfsck_operations lfsck_layout_master_ops = {
        .lfsck_exec_oit         = lfsck_layout_master_exec_oit,
        .lfsck_exec_dir         = lfsck_layout_exec_dir,
        .lfsck_post             = lfsck_layout_master_post,
+       .lfsck_interpret        = lfsck_layout_master_async_interpret,
        .lfsck_dump             = lfsck_layout_dump,
        .lfsck_double_scan      = lfsck_layout_master_double_scan,
        .lfsck_data_release     = lfsck_layout_master_data_release,
@@ -2824,6 +5659,7 @@ static struct lfsck_operations lfsck_layout_slave_ops = {
        .lfsck_dump             = lfsck_layout_dump,
        .lfsck_double_scan      = lfsck_layout_slave_double_scan,
        .lfsck_data_release     = lfsck_layout_slave_data_release,
+       .lfsck_quit             = lfsck_layout_slave_quit,
        .lfsck_in_notify        = lfsck_layout_slave_in_notify,
        .lfsck_query            = lfsck_layout_query,
        .lfsck_join             = lfsck_layout_slave_join,
@@ -2877,6 +5713,8 @@ int lfsck_layout_setup(const struct lu_env *env, struct lfsck_instance *lfsck)
                INIT_LIST_HEAD(&llsd->llsd_seq_list);
                INIT_LIST_HEAD(&llsd->llsd_master_list);
                spin_lock_init(&llsd->llsd_lock);
+               llsd->llsd_rb_root = RB_ROOT;
+               rwlock_init(&llsd->llsd_rb_lock);
                com->lc_data = llsd;
        }
        com->lc_file_size = sizeof(*lo);
@@ -2963,3 +5801,574 @@ out:
 
        return rc;
 }
+
+struct lfsck_orphan_it {
+       struct lfsck_component           *loi_com;
+       struct lfsck_rbtree_node         *loi_lrn;
+       struct lfsck_layout_slave_target *loi_llst;
+       struct lu_fid                     loi_key;
+       struct lu_orphan_rec              loi_rec;
+       __u64                             loi_hash;
+       unsigned int                      loi_over:1;
+};
+
+static int lfsck_fid_match_idx(const struct lu_env *env,
+                              struct lfsck_instance *lfsck,
+                              const struct lu_fid *fid, int idx)
+{
+       struct seq_server_site  *ss;
+       struct lu_server_fld    *sf;
+       struct lu_seq_range      range  = { 0 };
+       int                      rc;
+
+       /* All abnormal cases will be returned to MDT0. */
+       if (!fid_is_norm(fid)) {
+               if (idx == 0)
+                       return 1;
+
+               return 0;
+       }
+
+       ss = lu_site2seq(lfsck->li_bottom->dd_lu_dev.ld_site);
+       if (unlikely(ss == NULL))
+               return -ENOTCONN;
+
+       sf = ss->ss_server_fld;
+       LASSERT(sf != NULL);
+
+       fld_range_set_any(&range);
+       rc = fld_server_lookup(env, sf, fid_seq(fid), &range);
+       if (rc != 0)
+               return rc;
+
+       if (!fld_range_is_mdt(&range))
+               return -EINVAL;
+
+       if (range.lsr_index == idx)
+               return 1;
+
+       return 0;
+}
+
+static void lfsck_layout_destroy_orphan(const struct lu_env *env,
+                                       struct dt_device *dev,
+                                       struct dt_object *obj)
+{
+       struct thandle *handle;
+       int             rc;
+       ENTRY;
+
+       handle = dt_trans_create(env, dev);
+       if (IS_ERR(handle))
+               RETURN_EXIT;
+
+       rc = dt_declare_ref_del(env, obj, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_declare_destroy(env, obj, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       rc = dt_trans_start_local(env, dev, handle);
+       if (rc != 0)
+               GOTO(stop, rc);
+
+       dt_write_lock(env, obj, 0);
+       rc = dt_ref_del(env, obj, handle);
+       if (rc == 0)
+               rc = dt_destroy(env, obj, handle);
+       dt_write_unlock(env, obj);
+
+       GOTO(stop, rc);
+
+stop:
+       dt_trans_stop(env, dev, handle);
+
+       RETURN_EXIT;
+}
+
+static int lfsck_orphan_index_lookup(const struct lu_env *env,
+                                    struct dt_object *dt,
+                                    struct dt_rec *rec,
+                                    const struct dt_key *key,
+                                    struct lustre_capa *capa)
+{
+       return -EOPNOTSUPP;
+}
+
+static int lfsck_orphan_index_declare_insert(const struct lu_env *env,
+                                            struct dt_object *dt,
+                                            const struct dt_rec *rec,
+                                            const struct dt_key *key,
+                                            struct thandle *handle)
+{
+       return -EOPNOTSUPP;
+}
+
+static int lfsck_orphan_index_insert(const struct lu_env *env,
+                                    struct dt_object *dt,
+                                    const struct dt_rec *rec,
+                                    const struct dt_key *key,
+                                    struct thandle *handle,
+                                    struct lustre_capa *capa,
+                                    int ignore_quota)
+{
+       return -EOPNOTSUPP;
+}
+
+static int lfsck_orphan_index_declare_delete(const struct lu_env *env,
+                                            struct dt_object *dt,
+                                            const struct dt_key *key,
+                                            struct thandle *handle)
+{
+       return -EOPNOTSUPP;
+}
+
+static int lfsck_orphan_index_delete(const struct lu_env *env,
+                                    struct dt_object *dt,
+                                    const struct dt_key *key,
+                                    struct thandle *handle,
+                                    struct lustre_capa *capa)
+{
+       return -EOPNOTSUPP;
+}
+
+static struct dt_it *lfsck_orphan_it_init(const struct lu_env *env,
+                                         struct dt_object *dt,
+                                         __u32 attr,
+                                         struct lustre_capa *capa)
+{
+       struct dt_device                *dev    = lu2dt_dev(dt->do_lu.lo_dev);
+       struct lfsck_instance           *lfsck;
+       struct lfsck_component          *com    = NULL;
+       struct lfsck_layout_slave_data  *llsd;
+       struct lfsck_orphan_it          *it     = NULL;
+       int                              rc     = 0;
+       ENTRY;
+
+       lfsck = lfsck_instance_find(dev, true, false);
+       if (unlikely(lfsck == NULL))
+               RETURN(ERR_PTR(-ENXIO));
+
+       com = lfsck_component_find(lfsck, LT_LAYOUT);
+       if (unlikely(com == NULL))
+               GOTO(out, rc = -ENOENT);
+
+       llsd = com->lc_data;
+       if (!llsd->llsd_rbtree_valid)
+               GOTO(out, rc = -ESRCH);
+
+       OBD_ALLOC_PTR(it);
+       if (it == NULL)
+               GOTO(out, rc = -ENOMEM);
+
+       it->loi_llst = lfsck_layout_llst_find_and_del(llsd, attr, false);
+       if (it->loi_llst == NULL)
+               GOTO(out, rc = -ENXIO);
+
+       if (dev->dd_record_fid_accessed) {
+               /* The first iteration against the rbtree, scan the whole rbtree
+                * to remove the nodes which do NOT need to be handled. */
+               write_lock(&llsd->llsd_rb_lock);
+               if (dev->dd_record_fid_accessed) {
+                       struct rb_node                  *node;
+                       struct rb_node                  *next;
+                       struct lfsck_rbtree_node        *lrn;
+
+                       /* No need to record the fid accessing anymore. */
+                       dev->dd_record_fid_accessed = 0;
+
+                       node = rb_first(&llsd->llsd_rb_root);
+                       while (node != NULL) {
+                               next = rb_next(node);
+                               lrn = rb_entry(node, struct lfsck_rbtree_node,
+                                              lrn_node);
+                               if (atomic_read(&lrn->lrn_known_count) <=
+                                   atomic_read(&lrn->lrn_accessed_count)) {
+                                       rb_erase(node, &llsd->llsd_rb_root);
+                                       lfsck_rbtree_free(lrn);
+                               }
+                               node = next;
+                       }
+               }
+               write_unlock(&llsd->llsd_rb_lock);
+       }
+
+       /* read lock the rbtree when init, and unlock when fini */
+       read_lock(&llsd->llsd_rb_lock);
+       it->loi_com = com;
+       com = NULL;
+
+       GOTO(out, rc = 0);
+
+out:
+       if (com != NULL)
+               lfsck_component_put(env, com);
+       lfsck_instance_put(env, lfsck);
+       if (rc != 0) {
+               if (it != NULL)
+                       OBD_FREE_PTR(it);
+
+               it = (struct lfsck_orphan_it *)ERR_PTR(rc);
+       }
+
+       return (struct dt_it *)it;
+}
+
+static void lfsck_orphan_it_fini(const struct lu_env *env,
+                                struct dt_it *di)
+{
+       struct lfsck_orphan_it           *it    = (struct lfsck_orphan_it *)di;
+       struct lfsck_component           *com   = it->loi_com;
+       struct lfsck_layout_slave_data   *llsd;
+       struct lfsck_layout_slave_target *llst;
+
+       if (com != NULL) {
+               llsd = com->lc_data;
+               read_unlock(&llsd->llsd_rb_lock);
+               llst = it->loi_llst;
+               LASSERT(llst != NULL);
+
+               /* Save the key and hash for iterate next. */
+               llst->llst_fid = it->loi_key;
+               llst->llst_hash = it->loi_hash;
+               lfsck_layout_llst_put(llst);
+               lfsck_component_put(env, com);
+       }
+       OBD_FREE_PTR(it);
+}
+
+/**
+ * \retval      +1: the iteration finished
+ * \retval       0: on success, not finished
+ * \retval     -ve: on error
+ */
+static int lfsck_orphan_it_next(const struct lu_env *env,
+                               struct dt_it *di)
+{
+       struct lfsck_thread_info        *info   = lfsck_env_info(env);
+       struct filter_fid_old           *pfid   = &info->lti_old_pfid;
+       struct lu_attr                  *la     = &info->lti_la;
+       struct lfsck_orphan_it          *it     = (struct lfsck_orphan_it *)di;
+       struct lu_fid                   *key    = &it->loi_key;
+       struct lu_orphan_rec            *rec    = &it->loi_rec;
+       struct lfsck_component          *com    = it->loi_com;
+       struct lfsck_instance           *lfsck  = com->lc_lfsck;
+       struct lfsck_layout_slave_data  *llsd   = com->lc_data;
+       struct dt_object                *obj;
+       struct lfsck_rbtree_node        *lrn;
+       int                              pos;
+       int                              rc;
+       __u32                            save;
+       __u32                            idx    = it->loi_llst->llst_index;
+       bool                             exact  = false;
+       ENTRY;
+
+       if (it->loi_over)
+               RETURN(1);
+
+again0:
+       lrn = it->loi_lrn;
+       if (lrn == NULL) {
+               lrn = lfsck_rbtree_search(llsd, key, &exact);
+               if (lrn == NULL) {
+                       it->loi_over = 1;
+                       RETURN(1);
+               }
+
+               it->loi_lrn = lrn;
+               if (!exact) {
+                       key->f_seq = lrn->lrn_seq;
+                       key->f_oid = lrn->lrn_first_oid;
+                       key->f_ver = 0;
+               }
+       } else {
+               key->f_oid++;
+               if (unlikely(key->f_oid == 0)) {
+                       key->f_seq++;
+                       it->loi_lrn = NULL;
+                       goto again0;
+               }
+
+               if (key->f_oid >=
+                   lrn->lrn_first_oid + LFSCK_RBTREE_BITMAP_WIDTH) {
+                       it->loi_lrn = NULL;
+                       goto again0;
+               }
+       }
+
+       if (unlikely(atomic_read(&lrn->lrn_known_count) <=
+                    atomic_read(&lrn->lrn_accessed_count))) {
+               struct rb_node *next = rb_next(&lrn->lrn_node);
+
+               while (next != NULL) {
+                       lrn = rb_entry(next, struct lfsck_rbtree_node,
+                                      lrn_node);
+                       if (atomic_read(&lrn->lrn_known_count) >
+                           atomic_read(&lrn->lrn_accessed_count))
+                               break;
+                       next = rb_next(next);
+               }
+
+               if (next == NULL) {
+                       it->loi_over = 1;
+                       RETURN(1);
+               }
+
+               it->loi_lrn = lrn;
+               key->f_seq = lrn->lrn_seq;
+               key->f_oid = lrn->lrn_first_oid;
+               key->f_ver = 0;
+       }
+
+       pos = key->f_oid - lrn->lrn_first_oid;
+
+again1:
+       pos = find_next_bit(lrn->lrn_known_bitmap,
+                           LFSCK_RBTREE_BITMAP_WIDTH, pos);
+       if (pos >= LFSCK_RBTREE_BITMAP_WIDTH) {
+               key->f_oid = lrn->lrn_first_oid + pos;
+               if (unlikely(key->f_oid < lrn->lrn_first_oid)) {
+                       key->f_seq++;
+                       key->f_oid = 0;
+               }
+               it->loi_lrn = NULL;
+               goto again0;
+       }
+
+       if (test_bit(pos, lrn->lrn_accessed_bitmap)) {
+               pos++;
+               goto again1;
+       }
+
+       key->f_oid = lrn->lrn_first_oid + pos;
+       obj = lfsck_object_find(env, lfsck, key);
+       if (IS_ERR(obj)) {
+               rc = PTR_ERR(obj);
+               if (rc == -ENOENT) {
+                       pos++;
+                       goto again1;
+               }
+               RETURN(rc);
+       }
+
+       dt_read_lock(env, obj, 0);
+       if (!dt_object_exists(obj)) {
+               dt_read_unlock(env, obj);
+               lfsck_object_put(env, obj);
+               pos++;
+               goto again1;
+       }
+
+       rc = dt_attr_get(env, obj, la, BYPASS_CAPA);
+       if (rc != 0)
+               GOTO(out, rc);
+
+       rc = dt_xattr_get(env, obj, lfsck_buf_get(env, pfid, sizeof(*pfid)),
+                         XATTR_NAME_FID, BYPASS_CAPA);
+       if (rc == -ENODATA) {
+               /* For the pre-created OST-object, update the bitmap to avoid
+                * others LFSCK (second phase) iteration to touch it again. */
+               if (la->la_ctime == 0) {
+                       if (!test_and_set_bit(pos, lrn->lrn_accessed_bitmap))
+                               atomic_inc(&lrn->lrn_accessed_count);
+
+                       /* For the race between repairing dangling referenced
+                        * MDT-object and unlink the file, it may left orphan
+                        * OST-object there. Destroy it now! */
+                       if (unlikely(!(la->la_mode & S_ISUID))) {
+                               dt_read_unlock(env, obj);
+                               lfsck_layout_destroy_orphan(env,
+                                                           lfsck->li_bottom,
+                                                           obj);
+                               lfsck_object_put(env, obj);
+                               pos++;
+                               goto again1;
+                       }
+               } else if (idx == 0) {
+                       /* If the orphan OST-object has no parent information,
+                        * regard it as referenced by the MDT-object on MDT0. */
+                       fid_zero(&rec->lor_fid);
+                       rec->lor_uid = la->la_uid;
+                       rec->lor_gid = la->la_gid;
+                       GOTO(out, rc = 0);
+               }
+
+               dt_read_unlock(env, obj);
+               lfsck_object_put(env, obj);
+               pos++;
+               goto again1;
+       }
+
+       if (rc < 0)
+               GOTO(out, rc);
+
+       if (rc != sizeof(struct filter_fid) &&
+           rc != sizeof(struct filter_fid_old))
+               GOTO(out, rc = -EINVAL);
+
+       fid_le_to_cpu(&rec->lor_fid, &pfid->ff_parent);
+       /* Currently, the filter_fid::ff_parent::f_ver is not the real parent
+        * MDT-object's FID::f_ver, instead it is the OST-object index in its
+        * parent MDT-object's layout EA. */
+       save = rec->lor_fid.f_stripe_idx;
+       rec->lor_fid.f_ver = 0;
+       rc = lfsck_fid_match_idx(env, lfsck, &rec->lor_fid, idx);
+       /* If the orphan OST-object does not claim the MDT, then next.
+        *
+        * If we do not know whether it matches or not, then return it
+        * to the MDT for further check. */
+       if (rc == 0) {
+               dt_read_unlock(env, obj);
+               lfsck_object_put(env, obj);
+               pos++;
+               goto again1;
+       }
+
+       rec->lor_fid.f_stripe_idx = save;
+       rec->lor_uid = la->la_uid;
+       rec->lor_gid = la->la_gid;
+
+       CDEBUG(D_LFSCK, "%s: return orphan "DFID", PFID "DFID", owner %u:%u\n",
+              lfsck_lfsck2name(com->lc_lfsck), PFID(key), PFID(&rec->lor_fid),
+              rec->lor_uid, rec->lor_gid);
+
+       GOTO(out, rc = 0);
+
+out:
+       dt_read_unlock(env, obj);
+       lfsck_object_put(env, obj);
+       if (rc == 0)
+               it->loi_hash++;
+
+       return rc;
+}
+
+/**
+ * \retval      +1: locate to the exactly position
+ * \retval       0: cannot locate to the exactly position,
+ *                  call next() to move to a valid position.
+ * \retval     -ve: on error
+ */
+static int lfsck_orphan_it_get(const struct lu_env *env,
+                              struct dt_it *di,
+                              const struct dt_key *key)
+{
+       struct lfsck_orphan_it  *it   = (struct lfsck_orphan_it *)di;
+       int                      rc;
+
+       it->loi_key = *(struct lu_fid *)key;
+       rc = lfsck_orphan_it_next(env, di);
+       if (rc == 1)
+               return 0;
+
+       if (rc == 0)
+               return 1;
+
+       return rc;
+}
+
+static void lfsck_orphan_it_put(const struct lu_env *env,
+                               struct dt_it *di)
+{
+}
+
+static struct dt_key *lfsck_orphan_it_key(const struct lu_env *env,
+                                         const struct dt_it *di)
+{
+       struct lfsck_orphan_it *it = (struct lfsck_orphan_it *)di;
+
+       return (struct dt_key *)&it->loi_key;
+}
+
+static int lfsck_orphan_it_key_size(const struct lu_env *env,
+                                   const struct dt_it *di)
+{
+       return sizeof(struct lu_fid);
+}
+
+static int lfsck_orphan_it_rec(const struct lu_env *env,
+                              const struct dt_it *di,
+                              struct dt_rec *rec,
+                              __u32 attr)
+{
+       struct lfsck_orphan_it *it = (struct lfsck_orphan_it *)di;
+
+       *(struct lu_orphan_rec *)rec = it->loi_rec;
+
+       return 0;
+}
+
+static __u64 lfsck_orphan_it_store(const struct lu_env *env,
+                                  const struct dt_it *di)
+{
+       struct lfsck_orphan_it  *it   = (struct lfsck_orphan_it *)di;
+
+       return it->loi_hash;
+}
+
+/**
+ * \retval      +1: locate to the exactly position
+ * \retval       0: cannot locate to the exactly position,
+ *                  call next() to move to a valid position.
+ * \retval     -ve: on error
+ */
+static int lfsck_orphan_it_load(const struct lu_env *env,
+                               const struct dt_it *di,
+                               __u64 hash)
+{
+       struct lfsck_orphan_it           *it   = (struct lfsck_orphan_it *)di;
+       struct lfsck_layout_slave_target *llst = it->loi_llst;
+       int                               rc;
+
+       LASSERT(llst != NULL);
+
+       if (hash != llst->llst_hash) {
+               CWARN("%s: the given hash "LPU64" for orphan iteration does "
+                     "not match the one when fini "LPU64", to be reset.\n",
+                     lfsck_lfsck2name(it->loi_com->lc_lfsck), hash,
+                     llst->llst_hash);
+               fid_zero(&llst->llst_fid);
+               llst->llst_hash = 0;
+       }
+
+       it->loi_key = llst->llst_fid;
+       it->loi_hash = llst->llst_hash;
+       rc = lfsck_orphan_it_next(env, (struct dt_it *)di);
+       if (rc == 1)
+               return 0;
+
+       if (rc == 0)
+               return 1;
+
+       return rc;
+}
+
+static int lfsck_orphan_it_key_rec(const struct lu_env *env,
+                                  const struct dt_it *di,
+                                  void *key_rec)
+{
+       return 0;
+}
+
+const struct dt_index_operations lfsck_orphan_index_ops = {
+       .dio_lookup             = lfsck_orphan_index_lookup,
+       .dio_declare_insert     = lfsck_orphan_index_declare_insert,
+       .dio_insert             = lfsck_orphan_index_insert,
+       .dio_declare_delete     = lfsck_orphan_index_declare_delete,
+       .dio_delete             = lfsck_orphan_index_delete,
+       .dio_it = {
+               .init           = lfsck_orphan_it_init,
+               .fini           = lfsck_orphan_it_fini,
+               .get            = lfsck_orphan_it_get,
+               .put            = lfsck_orphan_it_put,
+               .next           = lfsck_orphan_it_next,
+               .key            = lfsck_orphan_it_key,
+               .key_size       = lfsck_orphan_it_key_size,
+               .rec            = lfsck_orphan_it_rec,
+               .store          = lfsck_orphan_it_store,
+               .load           = lfsck_orphan_it_load,
+               .key_rec        = lfsck_orphan_it_key_rec,
+       }
+};