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LU-12535 lov: Move page index to top level
[fs/lustre-release.git] / lustre / lov / lov_io.c
index f40dfa2..464c8f2 100644 (file)
@@ -23,7 +23,7 @@
  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  * Use is subject to license terms.
  *
- * Copyright (c) 2011, 2016, Intel Corporation.
+ * Copyright (c) 2011, 2017, Intel Corporation.
  */
 /*
  * This file is part of Lustre, http://www.lustre.org/
@@ -56,7 +56,7 @@ static inline struct lov_io_sub *lov_sub_alloc(struct lov_io *lio, int index)
                OBD_ALLOC_PTR(sub);
        }
 
-       if (sub != NULL) {
+       if (sub) {
                INIT_LIST_HEAD(&sub->sub_list);
                INIT_LIST_HEAD(&sub->sub_linkage);
                sub->sub_subio_index = index;
@@ -82,13 +82,22 @@ static void lov_io_sub_fini(const struct lu_env *env, struct lov_io *lio,
 
        cl_io_fini(sub->sub_env, &sub->sub_io);
 
-       if (sub->sub_env != NULL && !IS_ERR(sub->sub_env)) {
+       if (sub->sub_env && !IS_ERR(sub->sub_env)) {
                cl_env_put(sub->sub_env, &sub->sub_refcheck);
                sub->sub_env = NULL;
        }
        EXIT;
 }
 
+static inline bool
+is_index_within_mirror(struct lov_object *lov, int index, int mirror_index)
+{
+       struct lov_layout_composite *comp = &lov->u.composite;
+       struct lov_mirror_entry *lre = &comp->lo_mirrors[mirror_index];
+
+       return (index >= lre->lre_start && index <= lre->lre_end);
+}
+
 static int lov_io_sub_init(const struct lu_env *env, struct lov_io *lio,
                           struct lov_io_sub *sub)
 {
@@ -106,10 +115,17 @@ static int lov_io_sub_init(const struct lu_env *env, struct lov_io *lio,
                     !lov_r0(lov, index)->lo_sub[stripe]))
                RETURN(-EIO);
 
+       LASSERTF(is_index_within_mirror(lov, index, lio->lis_mirror_index),
+                DFID "iot = %d, index = %d, mirror = %d\n",
+                PFID(lu_object_fid(lov2lu(lov))), io->ci_type, index,
+                lio->lis_mirror_index);
+
        /* obtain new environment */
        sub->sub_env = cl_env_get(&sub->sub_refcheck);
-       if (IS_ERR(sub->sub_env))
+       if (IS_ERR(sub->sub_env)) {
                result = PTR_ERR(sub->sub_env);
+               RETURN(result);
+       }
 
        sub_obj = lovsub2cl(lov_r0(lov, index)->lo_sub[stripe]);
        sub_io  = &sub->sub_io;
@@ -122,7 +138,10 @@ static int lov_io_sub_init(const struct lu_env *env, struct lov_io *lio,
        sub_io->ci_type    = io->ci_type;
        sub_io->ci_no_srvlock = io->ci_no_srvlock;
        sub_io->ci_noatime = io->ci_noatime;
-       sub_io->ci_pio = io->ci_pio;
+       sub_io->ci_async_readahead = io->ci_async_readahead;
+       sub_io->ci_lock_no_expand = io->ci_lock_no_expand;
+       sub_io->ci_ndelay = io->ci_ndelay;
+       sub_io->ci_layout_version = io->ci_layout_version;
 
        result = cl_io_sub_init(sub->sub_env, sub_io, io->ci_type, sub_obj);
 
@@ -149,7 +168,7 @@ struct lov_io_sub *lov_sub_get(const struct lu_env *env,
 
        if (rc == 0) {
                sub = lov_sub_alloc(lio, index);
-               if (sub == NULL)
+               if (!sub)
                        GOTO(out, rc = -ENOMEM);
 
                rc = lov_io_sub_init(env, lio, sub);
@@ -172,29 +191,263 @@ out:
  * Lov io operations.
  *
  */
+static int lov_io_subio_init(const struct lu_env *env, struct lov_io *lio,
+                             struct cl_io *io)
+{
+       ENTRY;
+
+       LASSERT(lio->lis_object != NULL);
+
+       INIT_LIST_HEAD(&lio->lis_subios);
+       lio->lis_single_subio_index = -1;
+       lio->lis_nr_subios = 0;
+
+       RETURN(0);
+}
 
-int lov_page_index(const struct cl_page *page)
+/**
+ * Decide if it will need write intent RPC
+ */
+static int lov_io_mirror_write_intent(struct lov_io *lio,
+       struct lov_object *obj, struct cl_io *io)
 {
-       const struct cl_page_slice *slice;
+       struct lov_layout_composite *comp = &obj->u.composite;
+       struct lu_extent *ext = &io->ci_write_intent;
+       struct lov_mirror_entry *lre;
+       struct lov_mirror_entry *primary;
+       struct lov_layout_entry *lle;
+       size_t count = 0;
        ENTRY;
 
-       slice = cl_page_at(page, &lov_device_type);
-       LASSERT(slice != NULL);
-       LASSERT(slice->cpl_obj != NULL);
+       *ext = (typeof(*ext)) { lio->lis_pos, lio->lis_endpos };
+       io->ci_need_write_intent = 0;
+
+       if (!(io->ci_type == CIT_WRITE || cl_io_is_trunc(io) ||
+             cl_io_is_mkwrite(io)))
+               RETURN(0);
+
+       /*
+        * FLR: check if it needs to send a write intent RPC to server.
+        * Writing to sync_pending file needs write intent RPC to change
+        * the file state back to write_pending, so that the layout version
+        * can be increased when the state changes to sync_pending at a later
+        * time. Otherwise there exists a chance that an evicted client may
+        * dirty the file data while resync client is working on it.
+        * Designated I/O is allowed for resync workload.
+        */
+       if (lov_flr_state(obj) == LCM_FL_RDONLY ||
+           (lov_flr_state(obj) == LCM_FL_SYNC_PENDING &&
+            io->ci_designated_mirror == 0)) {
+               io->ci_need_write_intent = 1;
+               RETURN(0);
+       }
+
+       LASSERT((lov_flr_state(obj) == LCM_FL_WRITE_PENDING));
+       LASSERT(comp->lo_preferred_mirror >= 0);
+
+       /*
+        * need to iterate all components to see if there are
+        * multiple components covering the writing component
+        */
+       primary = &comp->lo_mirrors[comp->lo_preferred_mirror];
+       LASSERT(!primary->lre_stale);
+       lov_foreach_mirror_layout_entry(obj, lle, primary) {
+               LASSERT(lle->lle_valid);
+               if (!lu_extent_is_overlapped(ext, lle->lle_extent))
+                       continue;
+
+               ext->e_start = MIN(ext->e_start, lle->lle_extent->e_start);
+               ext->e_end = MAX(ext->e_end, lle->lle_extent->e_end);
+               ++count;
+       }
+       if (count == 0) {
+               CERROR(DFID ": cannot find any valid components covering "
+                      "file extent "DEXT", mirror: %d\n",
+                      PFID(lu_object_fid(lov2lu(obj))), PEXT(ext),
+                      primary->lre_mirror_id);
+               RETURN(-EIO);
+       }
+
+       count = 0;
+       lov_foreach_mirror_entry(obj, lre) {
+               if (lre == primary)
+                       continue;
 
-       RETURN(cl2lov_page(slice)->lps_index);
+               lov_foreach_mirror_layout_entry(obj, lle, lre) {
+                       if (!lle->lle_valid)
+                               continue;
+
+                       if (lu_extent_is_overlapped(ext, lle->lle_extent)) {
+                               ++count;
+                               break;
+                       }
+               }
+       }
+
+       CDEBUG(D_VFSTRACE, DFID "there are %zd components to be staled to "
+              "modify file extent "DEXT", iot: %d\n",
+              PFID(lu_object_fid(lov2lu(obj))), count, PEXT(ext), io->ci_type);
+
+       io->ci_need_write_intent = count > 0;
+
+       RETURN(0);
 }
 
-static int lov_io_subio_init(const struct lu_env *env, struct lov_io *lio,
-                             struct cl_io *io)
+static int lov_io_mirror_init(struct lov_io *lio, struct lov_object *obj,
+                              struct cl_io *io)
 {
+       struct lov_layout_composite *comp = &obj->u.composite;
+       int index;
+       int i;
+       int result;
        ENTRY;
 
-       LASSERT(lio->lis_object != NULL);
+       if (!lov_is_flr(obj)) {
+               LASSERT(comp->lo_preferred_mirror == 0);
+               lio->lis_mirror_index = comp->lo_preferred_mirror;
+               io->ci_ndelay = 0;
+               RETURN(0);
+       }
 
-       INIT_LIST_HEAD(&lio->lis_subios);
-       lio->lis_single_subio_index = -1;
-       lio->lis_nr_subios = 0;
+       /* transfer the layout version for verification */
+       if (io->ci_layout_version == 0)
+               io->ci_layout_version = obj->lo_lsm->lsm_layout_gen;
+
+       /* find the corresponding mirror for designated mirror IO */
+       if (io->ci_designated_mirror > 0) {
+               struct lov_mirror_entry *entry;
+
+               LASSERT(!io->ci_ndelay);
+
+               CDEBUG(D_LAYOUT, "designated I/O mirror state: %d\n",
+                     lov_flr_state(obj));
+
+               if ((cl_io_is_trunc(io) || io->ci_type == CIT_WRITE) &&
+                   (io->ci_layout_version != obj->lo_lsm->lsm_layout_gen)) {
+                       /*
+                        * For resync I/O, the ci_layout_version was the layout
+                        * version when resync starts. If it doesn't match the
+                        * current object layout version, it means the layout
+                        * has been changed
+                        */
+                       RETURN(-ESTALE);
+               }
+
+               io->ci_layout_version |= LU_LAYOUT_RESYNC;
+
+               index = 0;
+               lio->lis_mirror_index = -1;
+               lov_foreach_mirror_entry(obj, entry) {
+                       if (entry->lre_mirror_id ==
+                           io->ci_designated_mirror) {
+                               lio->lis_mirror_index = index;
+                               break;
+                       }
+
+                       index++;
+               }
+
+               RETURN(lio->lis_mirror_index < 0 ? -EINVAL : 0);
+       }
+
+       result = lov_io_mirror_write_intent(lio, obj, io);
+       if (result)
+               RETURN(result);
+
+       if (io->ci_need_write_intent) {
+               CDEBUG(D_VFSTRACE, DFID " need write intent for [%llu, %llu)\n",
+                      PFID(lu_object_fid(lov2lu(obj))),
+                      lio->lis_pos, lio->lis_endpos);
+
+               if (cl_io_is_trunc(io)) {
+                       /**
+                        * for truncate, we uses [size, EOF) to judge whether
+                        * a write intent needs to be send, but we need to
+                        * restore the write extent to [0, size).
+                        */
+                       io->ci_write_intent.e_start = 0;
+                       io->ci_write_intent.e_end =
+                                       io->u.ci_setattr.sa_attr.lvb_size;
+               }
+               /* stop cl_io_init() loop */
+               RETURN(1);
+       }
+
+       if (io->ci_ndelay_tried == 0 || /* first time to try */
+           /* reset the mirror index if layout has changed */
+           lio->lis_mirror_layout_gen != obj->lo_lsm->lsm_layout_gen) {
+               lio->lis_mirror_layout_gen = obj->lo_lsm->lsm_layout_gen;
+               index = lio->lis_mirror_index = comp->lo_preferred_mirror;
+       } else {
+               index = lio->lis_mirror_index;
+               LASSERT(index >= 0);
+
+               /* move mirror index to the next one */
+               index = (index + 1) % comp->lo_mirror_count;
+       }
+
+       for (i = 0; i < comp->lo_mirror_count; i++) {
+               struct lu_extent ext = { .e_start = lio->lis_pos,
+                                        .e_end   = lio->lis_pos + 1 };
+               struct lov_mirror_entry *lre;
+               struct lov_layout_entry *lle;
+               bool found = false;
+
+               lre = &comp->lo_mirrors[(index + i) % comp->lo_mirror_count];
+               if (!lre->lre_valid)
+                       continue;
+
+               lov_foreach_mirror_layout_entry(obj, lle, lre) {
+                       if (!lle->lle_valid)
+                               continue;
+
+                       if (lu_extent_is_overlapped(&ext, lle->lle_extent)) {
+                               found = true;
+                               break;
+                       }
+               }
+
+               if (found) {
+                       index = (index + i) % comp->lo_mirror_count;
+                       break;
+               }
+       }
+       if (i == comp->lo_mirror_count) {
+               CERROR(DFID": failed to find a component covering "
+                      "I/O region at %llu\n",
+                      PFID(lu_object_fid(lov2lu(obj))), lio->lis_pos);
+
+               dump_lsm(D_ERROR, obj->lo_lsm);
+
+               RETURN(-EIO);
+       }
+
+       CDEBUG(D_VFSTRACE, DFID ": flr state: %d, move mirror from %d to %d, "
+              "have retried: %d, mirror count: %d\n",
+              PFID(lu_object_fid(lov2lu(obj))), lov_flr_state(obj),
+              lio->lis_mirror_index, index, io->ci_ndelay_tried,
+              comp->lo_mirror_count);
+
+       lio->lis_mirror_index = index;
+
+       /*
+        * FLR: if all mirrors have been tried once, most likely the network
+        * of this client has been partitioned. We should relinquish CPU for
+        * a while before trying again.
+        */
+       ++io->ci_ndelay_tried;
+       if (io->ci_ndelay && io->ci_ndelay_tried >= comp->lo_mirror_count) {
+               set_current_state(TASK_INTERRUPTIBLE);
+               schedule_timeout(cfs_time_seconds(1)); /* 10ms */
+               if (signal_pending(current))
+                       RETURN(-EINTR);
+
+               /* reset retry counter */
+               io->ci_ndelay_tried = 1;
+       }
+
+       CDEBUG(D_VFSTRACE, "use %sdelayed RPC state for this IO\n",
+              io->ci_ndelay ? "non-" : "");
 
        RETURN(0);
 }
@@ -202,6 +455,8 @@ static int lov_io_subio_init(const struct lu_env *env, struct lov_io *lio,
 static int lov_io_slice_init(struct lov_io *lio,
                             struct lov_object *obj, struct cl_io *io)
 {
+       int index;
+       int result = 0;
        ENTRY;
 
        io->ci_result = 0;
@@ -212,42 +467,45 @@ static int lov_io_slice_init(struct lov_io *lio,
        switch (io->ci_type) {
        case CIT_READ:
        case CIT_WRITE:
-               lio->lis_pos = io->u.ci_rw.rw_range.cir_pos;
-               lio->lis_endpos = lio->lis_pos + io->u.ci_rw.rw_range.cir_count;
+               lio->lis_pos = io->u.ci_rw.crw_pos;
+               lio->lis_endpos = io->u.ci_rw.crw_pos + io->u.ci_rw.crw_count;
                lio->lis_io_endpos = lio->lis_endpos;
                if (cl_io_is_append(io)) {
                        LASSERT(io->ci_type == CIT_WRITE);
 
-                       /* If there is LOV EA hole, then we may cannot locate
-                        * the current file-tail exactly. */
+                       /*
+                        * If there is LOV EA hole, then we may cannot locate
+                        * the current file-tail exactly.
+                        */
                        if (unlikely(obj->lo_lsm->lsm_entries[0]->lsme_pattern &
                                     LOV_PATTERN_F_HOLE))
-                               RETURN(-EIO);
+                               GOTO(out, result = -EIO);
 
                        lio->lis_pos = 0;
                        lio->lis_endpos = OBD_OBJECT_EOF;
                }
                break;
 
-        case CIT_SETATTR:
-                if (cl_io_is_trunc(io))
-                        lio->lis_pos = io->u.ci_setattr.sa_attr.lvb_size;
-                else
-                        lio->lis_pos = 0;
-                lio->lis_endpos = OBD_OBJECT_EOF;
-                break;
+       case CIT_SETATTR:
+               if (cl_io_is_trunc(io))
+                       lio->lis_pos = io->u.ci_setattr.sa_attr.lvb_size;
+               else
+                       lio->lis_pos = 0;
+               lio->lis_endpos = OBD_OBJECT_EOF;
+               break;
 
        case CIT_DATA_VERSION:
                lio->lis_pos = 0;
                lio->lis_endpos = OBD_OBJECT_EOF;
                break;
 
-        case CIT_FAULT: {
-                pgoff_t index = io->u.ci_fault.ft_index;
-                lio->lis_pos = cl_offset(io->ci_obj, index);
-                lio->lis_endpos = cl_offset(io->ci_obj, index + 1);
-                break;
-        }
+       case CIT_FAULT: {
+               pgoff_t index = io->u.ci_fault.ft_index;
+
+               lio->lis_pos = cl_offset(io->ci_obj, index);
+               lio->lis_endpos = cl_offset(io->ci_obj, index + 1);
+               break;
+       }
 
        case CIT_FSYNC: {
                lio->lis_pos = io->u.ci_fsync.fi_start;
@@ -261,16 +519,84 @@ static int lov_io_slice_init(struct lov_io *lio,
                break;
        }
 
-        case CIT_MISC:
-                lio->lis_pos = 0;
-                lio->lis_endpos = OBD_OBJECT_EOF;
-                break;
+       case CIT_GLIMPSE:
+               lio->lis_pos = 0;
+               lio->lis_endpos = OBD_OBJECT_EOF;
+
+               if (lov_flr_state(obj) == LCM_FL_RDONLY &&
+                   !OBD_FAIL_CHECK(OBD_FAIL_FLR_GLIMPSE_IMMUTABLE))
+                       /* SoM is accurate, no need glimpse */
+                       GOTO(out, result = 1);
+               break;
+
+       case CIT_MISC:
+               lio->lis_pos = 0;
+               lio->lis_endpos = OBD_OBJECT_EOF;
+               break;
+
+       default:
+               LBUG();
+       }
+
+       result = lov_io_mirror_init(lio, obj, io);
+       if (result)
+               GOTO(out, result);
 
-        default:
-                LBUG();
-        }
+       /* check if it needs to instantiate layout */
+       if (!(io->ci_type == CIT_WRITE || cl_io_is_mkwrite(io) ||
+             (cl_io_is_trunc(io) && io->u.ci_setattr.sa_attr.lvb_size > 0)))
+               GOTO(out, result = 0);
 
-       RETURN(0);
+       /*
+        * for truncate, it only needs to instantiate the components
+        * before the truncated size.
+        */
+       if (cl_io_is_trunc(io)) {
+               io->ci_write_intent.e_start = 0;
+               /* for writes, e_end is endpos, the location of the file
+                * pointer after the write is completed, so it is not accessed.
+                * For truncate, 'end' is the size, and *is* acccessed.
+                * In other words, writes are [start, end), but truncate is
+                * [start, size], where both are included.  So add 1 to the
+                * size when creating the write intent to account for this.
+                */
+               io->ci_write_intent.e_end =
+                       io->u.ci_setattr.sa_attr.lvb_size + 1;
+       } else {
+               io->ci_write_intent.e_start = lio->lis_pos;
+               io->ci_write_intent.e_end = lio->lis_endpos;
+       }
+
+       index = 0;
+       lov_foreach_io_layout(index, lio, &io->ci_write_intent) {
+               if (!lsm_entry_inited(obj->lo_lsm, index)) {
+                       io->ci_need_write_intent = 1;
+                       break;
+               }
+       }
+
+       if (io->ci_need_write_intent && io->ci_designated_mirror > 0) {
+               /*
+                * REINT_SYNC RPC has already tried to instantiate all of the
+                * components involved, obviously it didn't succeed. Skip this
+                * mirror for now. The server won't be able to figure out
+                * which mirror it should instantiate components
+                */
+               CERROR(DFID": trying to instantiate components for designated "
+                      "I/O, file state: %d\n",
+                      PFID(lu_object_fid(lov2lu(obj))), lov_flr_state(obj));
+
+               io->ci_need_write_intent = 0;
+               GOTO(out, result = -EIO);
+       }
+
+       if (io->ci_need_write_intent)
+               GOTO(out, result = 1);
+
+       EXIT;
+
+out:
+       return result;
 }
 
 static void lov_io_fini(const struct lu_env *env, const struct cl_io_slice *ios)
@@ -310,13 +636,13 @@ static void lov_io_sub_inherit(struct lov_io_sub *sub, struct lov_io *lio,
        int index = lov_comp_entry(sub->sub_subio_index);
        int stripe = lov_comp_stripe(sub->sub_subio_index);
 
-       io->ci_pio = parent->ci_pio;
        switch (io->ci_type) {
        case CIT_SETATTR: {
                io->u.ci_setattr.sa_attr = parent->u.ci_setattr.sa_attr;
                io->u.ci_setattr.sa_attr_flags =
                        parent->u.ci_setattr.sa_attr_flags;
-               io->u.ci_setattr.sa_valid = parent->u.ci_setattr.sa_valid;
+               io->u.ci_setattr.sa_avalid = parent->u.ci_setattr.sa_avalid;
+               io->u.ci_setattr.sa_xvalid = parent->u.ci_setattr.sa_xvalid;
                io->u.ci_setattr.sa_stripe_index = stripe;
                io->u.ci_setattr.sa_parent_fid =
                                        parent->u.ci_setattr.sa_parent_fid;
@@ -355,16 +681,12 @@ static void lov_io_sub_inherit(struct lov_io_sub *sub, struct lov_io *lio,
        }
        case CIT_READ:
        case CIT_WRITE: {
-               io->u.ci_rw.rw_ptask = parent->u.ci_rw.rw_ptask;
-               io->u.ci_rw.rw_iter = parent->u.ci_rw.rw_iter;
-               io->u.ci_rw.rw_iocb = parent->u.ci_rw.rw_iocb;
-               io->u.ci_rw.rw_file = parent->u.ci_rw.rw_file;
-               io->u.ci_rw.rw_sync = parent->u.ci_rw.rw_sync;
+               io->u.ci_wr.wr_sync = cl_io_is_sync_write(parent);
                if (cl_io_is_append(parent)) {
-                       io->u.ci_rw.rw_append = 1;
+                       io->u.ci_wr.wr_append = 1;
                } else {
-                       io->u.ci_rw.rw_range.cir_pos = start;
-                       io->u.ci_rw.rw_range.cir_count = end - start;
+                       io->u.ci_rw.crw_pos = start;
+                       io->u.ci_rw.crw_count = end - start;
                }
                break;
        }
@@ -376,6 +698,8 @@ static void lov_io_sub_inherit(struct lov_io_sub *sub, struct lov_io *lio,
                io->u.ci_ladvise.li_flags = parent->u.ci_ladvise.li_flags;
                break;
        }
+       case CIT_GLIMPSE:
+       case CIT_MISC:
        default:
                break;
        }
@@ -383,63 +707,55 @@ static void lov_io_sub_inherit(struct lov_io_sub *sub, struct lov_io *lio,
 
 static loff_t lov_offset_mod(loff_t val, int delta)
 {
-        if (val != OBD_OBJECT_EOF)
-                val += delta;
-        return val;
+       if (val != OBD_OBJECT_EOF)
+               val += delta;
+       return val;
 }
 
 static int lov_io_iter_init(const struct lu_env *env,
                            const struct cl_io_slice *ios)
 {
-       struct cl_io         *io = ios->cis_io;
-       struct lov_io        *lio = cl2lov_io(env, ios);
+       struct lov_io *lio = cl2lov_io(env, ios);
        struct lov_stripe_md *lsm = lio->lis_object->lo_lsm;
-       struct lov_io_sub    *sub;
-       struct lov_layout_entry *le;
+       struct lov_io_sub *sub;
        struct lu_extent ext;
        int index;
        int rc = 0;
 
-        ENTRY;
+       ENTRY;
 
        ext.e_start = lio->lis_pos;
        ext.e_end = lio->lis_endpos;
 
-       index = 0;
-       lov_foreach_layout_entry(lio->lis_object, le) {
+       lov_foreach_io_layout(index, lio, &ext) {
+               struct lov_layout_entry *le = lov_entry(lio->lis_object, index);
                struct lov_layout_raid0 *r0 = &le->lle_raid0;
                u64 start;
                u64 end;
                int stripe;
 
-               index++;
-               if (!lu_extent_is_overlapped(&ext, &le->lle_extent))
-                       continue;
-
                CDEBUG(D_VFSTRACE, "component[%d] flags %#x\n",
-                      index - 1, lsm->lsm_entries[index - 1]->lsme_flags);
-               if (!lsm_entry_inited(lsm, index - 1)) {
-                       /* truncate IO will trigger write intent as well, and
-                        * it's handled in lov_io_setattr_iter_init() */
-                       if (io->ci_type == CIT_WRITE || cl_io_is_mkwrite(io)) {
-                               io->ci_need_write_intent = 1;
-                               /* execute it in main thread */
-                               io->ci_pio = 0;
-                               rc = -ENODATA;
-                               break;
-                       }
-
-                       /* Read from uninitialized components should return
-                        * zero filled pages. */
+                      index, lsm->lsm_entries[index]->lsme_flags);
+               if (!lsm_entry_inited(lsm, index)) {
+                       /*
+                        * Read from uninitialized components should return
+                        * zero filled pages.
+                        */
                        continue;
                }
 
+               if (!le->lle_valid && !ios->cis_io->ci_designated_mirror) {
+                       CERROR("I/O to invalid component: %d, mirror: %d\n",
+                              index, lio->lis_mirror_index);
+                       RETURN(-EIO);
+               }
+
                for (stripe = 0; stripe < r0->lo_nr; stripe++) {
-                       if (!lov_stripe_intersects(lsm, index - 1, stripe,
+                       if (!lov_stripe_intersects(lsm, index, stripe,
                                                   &ext, &start, &end))
                                continue;
 
-                       if (unlikely(r0->lo_sub[stripe] == NULL)) {
+                       if (unlikely(!r0->lo_sub[stripe])) {
                                if (ios->cis_io->ci_type == CIT_READ ||
                                    ios->cis_io->ci_type == CIT_WRITE ||
                                    ios->cis_io->ci_type == CIT_FAULT)
@@ -450,7 +766,7 @@ static int lov_io_iter_init(const struct lu_env *env,
 
                        end = lov_offset_mod(end, 1);
                        sub = lov_sub_get(env, lio,
-                                         lov_comp_index(index - 1, stripe));
+                                         lov_comp_index(index, stripe));
                        if (IS_ERR(sub)) {
                                rc = PTR_ERR(sub);
                                break;
@@ -463,9 +779,8 @@ static int lov_io_iter_init(const struct lu_env *env,
                        if (rc != 0)
                                break;
 
-                       CDEBUG(D_VFSTRACE,
-                               "shrink stripe: {%d, %d} range: [%llu, %llu)\n",
-                               index, stripe, start, end);
+                       CDEBUG(D_VFSTRACE, "shrink: %d [%llu, %llu)\n",
+                              stripe, start, end);
 
                        list_add_tail(&sub->sub_linkage, &lio->lis_active);
                }
@@ -478,12 +793,10 @@ static int lov_io_iter_init(const struct lu_env *env,
 static int lov_io_rw_iter_init(const struct lu_env *env,
                               const struct cl_io_slice *ios)
 {
-       struct cl_io *io = ios->cis_io;
        struct lov_io *lio = cl2lov_io(env, ios);
-       struct lov_stripe_md *lsm = lio->lis_object->lo_lsm;
+       struct cl_io *io = ios->cis_io;
        struct lov_stripe_md_entry *lse;
-       struct cl_io_range *range = &io->u.ci_rw.rw_range;
-       loff_t start = range->cir_pos;
+       loff_t start = io->u.ci_rw.crw_pos;
        loff_t next;
        int index;
 
@@ -493,14 +806,14 @@ static int lov_io_rw_iter_init(const struct lu_env *env,
        if (cl_io_is_append(io))
                RETURN(lov_io_iter_init(env, ios));
 
-       index = lov_lsm_entry(lsm, range->cir_pos);
+       index = lov_io_layout_at(lio, io->u.ci_rw.crw_pos);
        if (index < 0) { /* non-existing layout component */
                if (io->ci_type == CIT_READ) {
-                       /* TODO: it needs to detect the next component and
-                        * then set the next pos */
+                       /*
+                        * TODO: it needs to detect the next component and
+                        * then set the next pos
+                        */
                        io->ci_continue = 0;
-                       /* execute it in main thread */
-                       io->ci_pio = 0;
 
                        RETURN(lov_io_iter_init(env, ios));
                }
@@ -508,6 +821,10 @@ static int lov_io_rw_iter_init(const struct lu_env *env,
                RETURN(-ENODATA);
        }
 
+       if (!lov_entry(lio->lis_object, index)->lle_valid &&
+           !io->ci_designated_mirror)
+               RETURN(io->ci_type == CIT_READ ? -EAGAIN : -EIO);
+
        lse = lov_lse(lio->lis_object, index);
 
        next = MAX_LFS_FILESIZE;
@@ -520,37 +837,20 @@ static int lov_io_rw_iter_init(const struct lu_env *env,
                        next = MAX_LFS_FILESIZE;
        }
 
-       LASSERTF(range->cir_pos >= lse->lsme_extent.e_start,
-                "pos %lld, [%lld, %lld)\n", range->cir_pos,
+       LASSERTF(io->u.ci_rw.crw_pos >= lse->lsme_extent.e_start,
+                "pos %lld, [%lld, %lld)\n", io->u.ci_rw.crw_pos,
                 lse->lsme_extent.e_start, lse->lsme_extent.e_end);
        next = min_t(__u64, next, lse->lsme_extent.e_end);
        next = min_t(loff_t, next, lio->lis_io_endpos);
 
-       io->ci_continue  = next < lio->lis_io_endpos;
-       range->cir_count = next - range->cir_pos;
-       lio->lis_pos     = range->cir_pos;
-       lio->lis_endpos  = range->cir_pos + range->cir_count;
+       io->ci_continue = next < lio->lis_io_endpos;
+       io->u.ci_rw.crw_count = next - io->u.ci_rw.crw_pos;
+       lio->lis_pos    = io->u.ci_rw.crw_pos;
+       lio->lis_endpos = io->u.ci_rw.crw_pos + io->u.ci_rw.crw_count;
        CDEBUG(D_VFSTRACE,
-              "stripe: {%d, %llu} range: [%llu, %llu) end: %llu, count: %zd\n",
-              index, start, lio->lis_pos, lio->lis_endpos,
-              lio->lis_io_endpos, range->cir_count);
-
-       if (!io->ci_continue) {
-               /* the last piece of IO, execute it in main thread */
-               io->ci_pio = 0;
-       }
-
-       if (io->ci_pio) {
-               /* it only splits IO here for parallel IO,
-                * there will be no actual IO going to occur,
-                * so it doesn't need to invoke lov_io_iter_init()
-                * to initialize sub IOs. */
-               if (!lsm_entry_inited(lsm, index)) {
-                       io->ci_need_write_intent = 1;
-                       RETURN(-ENODATA);
-               }
-               RETURN(0);
-       }
+              "stripe: %llu chunk: [%llu, %llu) %llu, %zd\n",
+              (__u64)start, lio->lis_pos, lio->lis_endpos,
+              (__u64)lio->lis_io_endpos, io->u.ci_rw.crw_count);
 
        /*
         * XXX The following call should be optimized: we know, that
@@ -564,16 +864,14 @@ static int lov_io_setattr_iter_init(const struct lu_env *env,
 {
        struct lov_io *lio = cl2lov_io(env, ios);
        struct cl_io *io = ios->cis_io;
-       struct lov_stripe_md *lsm = lio->lis_object->lo_lsm;
        int index;
        ENTRY;
 
        if (cl_io_is_trunc(io) && lio->lis_pos > 0) {
-               index = lov_lsm_entry(lsm, lio->lis_pos - 1);
-               if (index > 0 && !lsm_entry_inited(lsm, index)) {
-                       io->ci_need_write_intent = 1;
+               index = lov_io_layout_at(lio, lio->lis_pos - 1);
+               /* no entry found for such offset */
+               if (index < 0)
                        RETURN(io->ci_result = -ENODATA);
-               }
        }
 
        RETURN(lov_io_iter_init(env, ios));
@@ -600,49 +898,49 @@ static int lov_io_call(const struct lu_env *env, struct lov_io *lio,
 
 static int lov_io_lock(const struct lu_env *env, const struct cl_io_slice *ios)
 {
-        ENTRY;
-        RETURN(lov_io_call(env, cl2lov_io(env, ios), cl_io_lock));
+       ENTRY;
+       RETURN(lov_io_call(env, cl2lov_io(env, ios), cl_io_lock));
 }
 
 static int lov_io_start(const struct lu_env *env, const struct cl_io_slice *ios)
 {
-        ENTRY;
-        RETURN(lov_io_call(env, cl2lov_io(env, ios), cl_io_start));
+       ENTRY;
+       RETURN(lov_io_call(env, cl2lov_io(env, ios), cl_io_start));
 }
 
 static int lov_io_end_wrapper(const struct lu_env *env, struct cl_io *io)
 {
-        ENTRY;
-        /*
-         * It's possible that lov_io_start() wasn't called against this
-         * sub-io, either because previous sub-io failed, or upper layer
-         * completed IO.
-         */
-        if (io->ci_state == CIS_IO_GOING)
-                cl_io_end(env, io);
-        else
-                io->ci_state = CIS_IO_FINISHED;
-        RETURN(0);
+       ENTRY;
+       /*
+        * It's possible that lov_io_start() wasn't called against this
+        * sub-io, either because previous sub-io failed, or upper layer
+        * completed IO.
+        */
+       if (io->ci_state == CIS_IO_GOING)
+               cl_io_end(env, io);
+       else
+               io->ci_state = CIS_IO_FINISHED;
+       RETURN(0);
 }
 
 static int lov_io_iter_fini_wrapper(const struct lu_env *env, struct cl_io *io)
 {
-        cl_io_iter_fini(env, io);
-        RETURN(0);
+       cl_io_iter_fini(env, io);
+       RETURN(0);
 }
 
 static int lov_io_unlock_wrapper(const struct lu_env *env, struct cl_io *io)
 {
-        cl_io_unlock(env, io);
-        RETURN(0);
+       cl_io_unlock(env, io);
+       RETURN(0);
 }
 
 static void lov_io_end(const struct lu_env *env, const struct cl_io_slice *ios)
 {
-        int rc;
+       int rc;
 
-        rc = lov_io_call(env, cl2lov_io(env, ios), lov_io_end_wrapper);
-        LASSERT(rc == 0);
+       rc = lov_io_call(env, cl2lov_io(env, ios), lov_io_end_wrapper);
+       LASSERT(rc == 0);
 }
 
 static void
@@ -650,14 +948,18 @@ lov_io_data_version_end(const struct lu_env *env, const struct cl_io_slice *ios)
 {
        struct lov_io *lio = cl2lov_io(env, ios);
        struct cl_io *parent = lio->lis_cl.cis_io;
+       struct cl_data_version_io *pdv = &parent->u.ci_data_version;
        struct lov_io_sub *sub;
 
        ENTRY;
        list_for_each_entry(sub, &lio->lis_active, sub_linkage) {
-               lov_io_end_wrapper(env, &sub->sub_io);
+               struct cl_data_version_io *sdv = &sub->sub_io.u.ci_data_version;
 
-               parent->u.ci_data_version.dv_data_version +=
-                       sub->sub_io.u.ci_data_version.dv_data_version;
+               lov_io_end_wrapper(sub->sub_env, &sub->sub_io);
+
+               pdv->dv_data_version += sdv->dv_data_version;
+               if (pdv->dv_layout_version > sdv->dv_layout_version)
+                       pdv->dv_layout_version = sdv->dv_layout_version;
 
                if (parent->ci_result == 0)
                        parent->ci_result = sub->sub_io.ci_result;
@@ -669,26 +971,26 @@ lov_io_data_version_end(const struct lu_env *env, const struct cl_io_slice *ios)
 static void lov_io_iter_fini(const struct lu_env *env,
                              const struct cl_io_slice *ios)
 {
-        struct lov_io *lio = cl2lov_io(env, ios);
-        int rc;
+       struct lov_io *lio = cl2lov_io(env, ios);
+       int rc;
 
-        ENTRY;
-        rc = lov_io_call(env, lio, lov_io_iter_fini_wrapper);
-        LASSERT(rc == 0);
+       ENTRY;
+       rc = lov_io_call(env, lio, lov_io_iter_fini_wrapper);
+       LASSERT(rc == 0);
        while (!list_empty(&lio->lis_active))
                list_del_init(lio->lis_active.next);
-        EXIT;
+       EXIT;
 }
 
 static void lov_io_unlock(const struct lu_env *env,
                           const struct cl_io_slice *ios)
 {
-        int rc;
+       int rc;
 
-        ENTRY;
-        rc = lov_io_call(env, cl2lov_io(env, ios), lov_io_unlock_wrapper);
-        LASSERT(rc == 0);
-        EXIT;
+       ENTRY;
+       rc = lov_io_call(env, cl2lov_io(env, ios), lov_io_unlock_wrapper);
+       LASSERT(rc == 0);
+       EXIT;
 }
 
 static int lov_io_read_ahead(const struct lu_env *env,
@@ -710,14 +1012,18 @@ static int lov_io_read_ahead(const struct lu_env *env,
        ENTRY;
 
        offset = cl_offset(obj, start);
-       index = lov_lsm_entry(loo->lo_lsm, offset);
+       index = lov_io_layout_at(lio, offset);
        if (index < 0 || !lsm_entry_inited(loo->lo_lsm, index))
                RETURN(-ENODATA);
 
+       /* avoid readahead to expand to stale components */
+       if (!lov_entry(loo, index)->lle_valid)
+               RETURN(-EIO);
+
        stripe = lov_stripe_number(loo->lo_lsm, index, offset);
 
        r0 = lov_r0(loo, index);
-       if (unlikely(r0->lo_sub[stripe] == NULL))
+       if (unlikely(!r0->lo_sub[stripe]))
                RETURN(-EIO);
 
        sub = lov_sub_get(env, lio, lov_comp_index(index, stripe));
@@ -748,7 +1054,7 @@ static int lov_io_read_ahead(const struct lu_env *env,
                                               ra_end, stripe);
 
        /* boundary of current component */
-       ra_end = cl_index(obj, (loff_t)lov_lse(loo, index)->lsme_extent.e_end);
+       ra_end = cl_index(obj, (loff_t)lov_io_extent(lio, index)->e_end);
        if (ra_end != CL_PAGE_EOF && ra->cra_end >= ra_end)
                ra->cra_end = ra_end - 1;
 
@@ -792,35 +1098,37 @@ static int lov_io_submit(const struct lu_env *env,
        struct lov_io_sub       *sub;
        struct cl_page_list     *plist = &lov_env_info(env)->lti_plist;
        struct cl_page          *page;
+       struct cl_page          *tmp;
        int index;
        int rc = 0;
        ENTRY;
 
-       if (lio->lis_nr_subios == 1) {
-               int idx = lio->lis_single_subio_index;
-
-               sub = lov_sub_get(env, lio, idx);
-               LASSERT(!IS_ERR(sub));
-               LASSERT(sub == &lio->lis_single_subio);
-               rc = cl_io_submit_rw(sub->sub_env, &sub->sub_io,
-                                    crt, queue);
-               RETURN(rc);
-       }
-
        cl_page_list_init(plist);
        while (qin->pl_nr > 0) {
                struct cl_2queue  *cl2q = &lov_env_info(env)->lti_cl2q;
 
-               cl_2queue_init(cl2q);
-
                page = cl_page_list_first(qin);
+               if (lov_page_is_empty(page)) {
+                       cl_page_list_move(&queue->c2_qout, qin, page);
+
+                       /*
+                        * it could only be mirror read to get here therefore
+                        * the pages will be transient. We don't care about
+                        * the return code of cl_page_prep() at all.
+                        */
+                       (void) cl_page_prep(env, ios->cis_io, page, crt);
+                       cl_page_completion(env, page, crt, 0);
+                       continue;
+               }
+
+               cl_2queue_init(cl2q);
                cl_page_list_move(&cl2q->c2_qin, qin, page);
 
-               index = lov_page_index(page);
-               while (qin->pl_nr > 0) {
-                       page = cl_page_list_first(qin);
-                       if (index != lov_page_index(page))
-                               break;
+               index = page->cp_lov_index;
+               cl_page_list_for_each_safe(page, tmp, qin) {
+                       /* this page is not on this stripe */
+                       if (index != page->cp_lov_index)
+                               continue;
 
                        cl_page_list_move(&cl2q->c2_qin, qin, page);
                }
@@ -853,7 +1161,7 @@ static int lov_io_commit_async(const struct lu_env *env,
                               cl_commit_cbt cb)
 {
        struct cl_page_list *plist = &lov_env_info(env)->lti_plist;
-       struct lov_io     *lio = cl2lov_io(env, ios);
+       struct lov_io *lio = cl2lov_io(env, ios);
        struct lov_io_sub *sub;
        struct cl_page *page;
        int rc = 0;
@@ -862,6 +1170,8 @@ static int lov_io_commit_async(const struct lu_env *env,
        if (lio->lis_nr_subios == 1) {
                int idx = lio->lis_single_subio_index;
 
+               LASSERT(!lov_page_is_empty(cl_page_list_first(queue)));
+
                sub = lov_sub_get(env, lio, idx);
                LASSERT(!IS_ERR(sub));
                LASSERT(sub == &lio->lis_single_subio);
@@ -877,12 +1187,14 @@ static int lov_io_commit_async(const struct lu_env *env,
 
                LASSERT(plist->pl_nr == 0);
                page = cl_page_list_first(queue);
+               LASSERT(!lov_page_is_empty(page));
+
                cl_page_list_move(plist, queue, page);
 
-               index = lov_page_index(page);
+               index = page->cp_lov_index;
                while (queue->pl_nr > 0) {
                        page = cl_page_list_first(queue);
-                       if (index != lov_page_index(page))
+                       if (index != page->cp_lov_index)
                                break;
 
                        cl_page_list_move(plist, queue, page);
@@ -928,7 +1240,7 @@ static int lov_io_fault_start(const struct lu_env *env,
 
        fio = &ios->cis_io->u.ci_fault;
        lio = cl2lov_io(env, ios);
-       sub = lov_sub_get(env, lio, lov_page_index(fio->ft_page));
+       sub = lov_sub_get(env, lio, fio->ft_page->cp_lov_index);
        sub->sub_io.u.ci_fault.ft_nob = fio->ft_nob;
 
        RETURN(lov_io_start(env, ios));
@@ -955,25 +1267,25 @@ static void lov_io_fsync_end(const struct lu_env *env,
 }
 
 static const struct cl_io_operations lov_io_ops = {
-        .op = {
-                [CIT_READ] = {
-                        .cio_fini      = lov_io_fini,
-                        .cio_iter_init = lov_io_rw_iter_init,
-                        .cio_iter_fini = lov_io_iter_fini,
-                        .cio_lock      = lov_io_lock,
-                        .cio_unlock    = lov_io_unlock,
-                        .cio_start     = lov_io_start,
-                        .cio_end       = lov_io_end
-                },
-                [CIT_WRITE] = {
-                        .cio_fini      = lov_io_fini,
-                        .cio_iter_init = lov_io_rw_iter_init,
-                        .cio_iter_fini = lov_io_iter_fini,
-                        .cio_lock      = lov_io_lock,
-                        .cio_unlock    = lov_io_unlock,
-                        .cio_start     = lov_io_start,
-                        .cio_end       = lov_io_end
-                },
+       .op = {
+               [CIT_READ] = {
+                       .cio_fini      = lov_io_fini,
+                       .cio_iter_init = lov_io_rw_iter_init,
+                       .cio_iter_fini = lov_io_iter_fini,
+                       .cio_lock      = lov_io_lock,
+                       .cio_unlock    = lov_io_unlock,
+                       .cio_start     = lov_io_start,
+                       .cio_end       = lov_io_end
+               },
+               [CIT_WRITE] = {
+                       .cio_fini      = lov_io_fini,
+                       .cio_iter_init = lov_io_rw_iter_init,
+                       .cio_iter_fini = lov_io_iter_fini,
+                       .cio_lock      = lov_io_lock,
+                       .cio_unlock    = lov_io_unlock,
+                       .cio_start     = lov_io_start,
+                       .cio_end       = lov_io_end
+               },
                [CIT_SETATTR] = {
                        .cio_fini      = lov_io_fini,
                        .cio_iter_init = lov_io_setattr_iter_init,
@@ -984,23 +1296,23 @@ static const struct cl_io_operations lov_io_ops = {
                        .cio_end       = lov_io_end
                },
                [CIT_DATA_VERSION] = {
-                       .cio_fini       = lov_io_fini,
-                       .cio_iter_init  = lov_io_iter_init,
-                       .cio_iter_fini  = lov_io_iter_fini,
-                       .cio_lock       = lov_io_lock,
-                       .cio_unlock     = lov_io_unlock,
-                       .cio_start      = lov_io_start,
-                       .cio_end        = lov_io_data_version_end,
+                       .cio_fini       = lov_io_fini,
+                       .cio_iter_init  = lov_io_iter_init,
+                       .cio_iter_fini  = lov_io_iter_fini,
+                       .cio_lock       = lov_io_lock,
+                       .cio_unlock     = lov_io_unlock,
+                       .cio_start      = lov_io_start,
+                       .cio_end        = lov_io_data_version_end,
+               },
+               [CIT_FAULT] = {
+                       .cio_fini      = lov_io_fini,
+                       .cio_iter_init = lov_io_iter_init,
+                       .cio_iter_fini = lov_io_iter_fini,
+                       .cio_lock      = lov_io_lock,
+                       .cio_unlock    = lov_io_unlock,
+                       .cio_start     = lov_io_fault_start,
+                       .cio_end       = lov_io_end
                },
-                [CIT_FAULT] = {
-                        .cio_fini      = lov_io_fini,
-                        .cio_iter_init = lov_io_iter_init,
-                        .cio_iter_fini = lov_io_iter_fini,
-                        .cio_lock      = lov_io_lock,
-                        .cio_unlock    = lov_io_unlock,
-                        .cio_start     = lov_io_fault_start,
-                        .cio_end       = lov_io_end
-                },
                [CIT_FSYNC] = {
                        .cio_fini      = lov_io_fini,
                        .cio_iter_init = lov_io_iter_init,
@@ -1019,11 +1331,14 @@ static const struct cl_io_operations lov_io_ops = {
                        .cio_start     = lov_io_start,
                        .cio_end       = lov_io_end
                },
+               [CIT_GLIMPSE] = {
+                       .cio_fini      = lov_io_fini,
+               },
                [CIT_MISC] = {
                        .cio_fini      = lov_io_fini
                }
        },
-       .cio_read_ahead                = lov_io_read_ahead,
+       .cio_read_ahead                = lov_io_read_ahead,
        .cio_submit                    = lov_io_submit,
        .cio_commit_async              = lov_io_commit_async,
 };
@@ -1055,7 +1370,7 @@ static int lov_empty_io_submit(const struct lu_env *env,
 static void lov_empty_impossible(const struct lu_env *env,
                                  struct cl_io_slice *ios)
 {
-        LBUG();
+       LBUG();
 }
 
 #define LOV_EMPTY_IMPOSSIBLE ((void *)lov_empty_impossible)
@@ -1064,43 +1379,46 @@ static void lov_empty_impossible(const struct lu_env *env,
  * An io operation vector for files without stripes.
  */
 static const struct cl_io_operations lov_empty_io_ops = {
-        .op = {
-                [CIT_READ] = {
-                        .cio_fini       = lov_empty_io_fini,
+       .op = {
+               [CIT_READ] = {
+                       .cio_fini       = lov_empty_io_fini,
 #if 0
-                        .cio_iter_init  = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_lock       = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_start      = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_end        = LOV_EMPTY_IMPOSSIBLE
+                       .cio_iter_init  = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_lock       = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_start      = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_end        = LOV_EMPTY_IMPOSSIBLE
 #endif
-                },
-                [CIT_WRITE] = {
-                        .cio_fini      = lov_empty_io_fini,
-                        .cio_iter_init = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_lock      = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_start     = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_end       = LOV_EMPTY_IMPOSSIBLE
-                },
-                [CIT_SETATTR] = {
-                        .cio_fini      = lov_empty_io_fini,
-                        .cio_iter_init = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_lock      = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_start     = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_end       = LOV_EMPTY_IMPOSSIBLE
-                },
-                [CIT_FAULT] = {
-                        .cio_fini      = lov_empty_io_fini,
-                        .cio_iter_init = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_lock      = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_start     = LOV_EMPTY_IMPOSSIBLE,
-                        .cio_end       = LOV_EMPTY_IMPOSSIBLE
-                },
+               },
+               [CIT_WRITE] = {
+                       .cio_fini      = lov_empty_io_fini,
+                       .cio_iter_init = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_lock      = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_start     = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_end       = LOV_EMPTY_IMPOSSIBLE
+               },
+               [CIT_SETATTR] = {
+                       .cio_fini      = lov_empty_io_fini,
+                       .cio_iter_init = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_lock      = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_start     = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_end       = LOV_EMPTY_IMPOSSIBLE
+               },
+               [CIT_FAULT] = {
+                       .cio_fini      = lov_empty_io_fini,
+                       .cio_iter_init = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_lock      = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_start     = LOV_EMPTY_IMPOSSIBLE,
+                       .cio_end       = LOV_EMPTY_IMPOSSIBLE
+               },
                [CIT_FSYNC] = {
                        .cio_fini      = lov_empty_io_fini
                },
                [CIT_LADVISE] = {
                        .cio_fini   = lov_empty_io_fini
                },
+               [CIT_GLIMPSE] = {
+                       .cio_fini      = lov_empty_io_fini
+               },
                [CIT_MISC] = {
                        .cio_fini      = lov_empty_io_fini
                }
@@ -1112,23 +1430,26 @@ static const struct cl_io_operations lov_empty_io_ops = {
 int lov_io_init_composite(const struct lu_env *env, struct cl_object *obj,
                          struct cl_io *io)
 {
-       struct lov_io       *lio = lov_env_io(env);
-       struct lov_object   *lov = cl2lov(obj);
+       struct lov_io *lio = lov_env_io(env);
+       struct lov_object *lov = cl2lov(obj);
+       int result;
 
        ENTRY;
+
        INIT_LIST_HEAD(&lio->lis_active);
-       io->ci_result = lov_io_slice_init(lio, lov, io);
-       if (io->ci_result != 0)
-               RETURN(io->ci_result);
-
-       if (io->ci_result == 0) {
-               io->ci_result = lov_io_subio_init(env, lio, io);
-               if (io->ci_result == 0) {
-                       cl_io_slice_add(io, &lio->lis_cl, obj, &lov_io_ops);
-                       atomic_inc(&lov->lo_active_ios);
-               }
+       result = lov_io_slice_init(lio, lov, io);
+       if (result)
+               GOTO(out, result);
+
+       result = lov_io_subio_init(env, lio, io);
+       if (!result) {
+               cl_io_slice_add(io, &lio->lis_cl, obj, &lov_io_ops);
+               atomic_inc(&lov->lo_active_ios);
        }
-       RETURN(io->ci_result);
+       EXIT;
+out:
+       io->ci_result = result < 0 ? result : 0;
+       return result;
 }
 
 int lov_io_init_empty(const struct lu_env *env, struct cl_object *obj,
@@ -1144,6 +1465,7 @@ int lov_io_init_empty(const struct lu_env *env, struct cl_object *obj,
        default:
                LBUG();
        case CIT_MISC:
+       case CIT_GLIMPSE:
        case CIT_READ:
                result = 0;
                break;
@@ -1187,6 +1509,7 @@ int lov_io_init_released(const struct lu_env *env, struct cl_object *obj,
                LASSERTF(0, "invalid type %d\n", io->ci_type);
                result = -EOPNOTSUPP;
                break;
+       case CIT_GLIMPSE:
        case CIT_MISC:
        case CIT_FSYNC:
        case CIT_LADVISE:
@@ -1194,7 +1517,8 @@ int lov_io_init_released(const struct lu_env *env, struct cl_object *obj,
                result = 1;
                break;
        case CIT_SETATTR:
-               /* the truncate to 0 is managed by MDT:
+               /*
+                * the truncate to 0 is managed by MDT:
                 * - in open, for open O_TRUNC
                 * - in setattr, for truncate
                 */
@@ -1221,4 +1545,45 @@ int lov_io_init_released(const struct lu_env *env, struct cl_object *obj,
        io->ci_result = result < 0 ? result : 0;
        RETURN(result);
 }
+
+/**
+ * Return the index in composite:lo_entries by the file offset
+ */
+int lov_io_layout_at(struct lov_io *lio, __u64 offset)
+{
+       struct lov_object *lov = lio->lis_object;
+       struct lov_layout_composite *comp = &lov->u.composite;
+       int start_index = 0;
+       int end_index = comp->lo_entry_count - 1;
+       int i;
+
+       LASSERT(lov->lo_type == LLT_COMP);
+
+       /* This is actual file offset so nothing can cover eof. */
+       if (offset == LUSTRE_EOF)
+               return -1;
+
+       if (lov_is_flr(lov)) {
+               struct lov_mirror_entry *lre;
+
+               LASSERT(lio->lis_mirror_index >= 0);
+
+               lre = &comp->lo_mirrors[lio->lis_mirror_index];
+               start_index = lre->lre_start;
+               end_index = lre->lre_end;
+       }
+
+       for (i = start_index; i <= end_index; i++) {
+               struct lov_layout_entry *lle = lov_entry(lov, i);
+
+               if ((offset >= lle->lle_extent->e_start &&
+                    offset < lle->lle_extent->e_end) ||
+                   (offset == OBD_OBJECT_EOF &&
+                    lle->lle_extent->e_end == OBD_OBJECT_EOF))
+                       return i;
+       }
+
+       return -1;
+}
+
 /** @} lov */