X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=blobdiff_plain;f=lustre%2Flov%2Flov_io.c;h=095fdb6bc0ce39cbb7f02706135d1ae84c7d906a;hp=2339ea56c6119a40535d4968a973c5cacec9f23c;hb=a7997c836bbfe2a0674007f1c23b9593e596e0ba;hpb=db59ecb5d1d0284fb918def6348a11e0966d7767;ds=sidebyside

diff --git a/lustre/lov/lov_io.c b/lustre/lov/lov_io.c
index 2339ea5..095fdb6 100644
--- a/lustre/lov/lov_io.c
+++ b/lustre/lov/lov_io.c
@@ -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 +138,9 @@ 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_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 +167,7 @@ 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);
@@ -199,9 +217,258 @@ static int lov_io_subio_init(const struct lu_env *env, struct lov_io *lio,
 	RETURN(0);
 }
 
+/**
+ * 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)
+{
+	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;
+
+	*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;
+
+		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_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;
+
+	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);
+	}
+
+	/* 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(msecs_to_jiffies(MSEC_PER_SEC)); /* 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);
+}
+
 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 +479,45 @@ 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 +531,76 @@ 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;
 
-        default:
-                LBUG();
-        }
+		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;
 
-	RETURN(0);
+	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);
+
+	/* 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);
+
+	/*
+	 * 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;
+		io->ci_write_intent.e_end = io->u.ci_setattr.sa_attr.lvb_size;
+	} 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 +640,13 @@ 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 +685,12 @@ 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 +702,8 @@ 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 +711,55 @@ 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 +770,7 @@ 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 +783,8 @@ 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);
 		}
@@ -478,14 +797,11 @@ 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;
-	unsigned long ssize;
 	int index;
 
 	LASSERT(io->ci_type == CIT_READ || io->ci_type == CIT_WRITE);
@@ -494,14 +810,14 @@ 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));
 		}
@@ -509,45 +825,36 @@ 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);
 
-	ssize = lse->lsme_stripe_size;
-	lov_do_div64(start, ssize);
-	next = (start + 1) * ssize;
-	if (next <= start * ssize)
-		next = ~0ull;
+	next = MAX_LFS_FILESIZE;
+	if (lse->lsme_stripe_count > 1) {
+		unsigned long ssize = lse->lsme_stripe_size;
+
+		lov_do_div64(start, ssize);
+		next = (start + 1) * ssize;
+		if (next <= start * ssize)
+			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
@@ -561,16 +868,14 @@ 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));
@@ -597,49 +902,49 @@ 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
@@ -647,14 +952,18 @@ 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;
+
+		lov_io_end_wrapper(sub->sub_env, &sub->sub_io);
 
-		parent->u.ci_data_version.dv_data_version +=
-			sub->sub_io.u.ci_data_version.dv_data_version;
+		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;
@@ -666,26 +975,26 @@ 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,
@@ -707,14 +1016,18 @@ 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));
@@ -745,7 +1058,7 @@ 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;
 
@@ -793,24 +1106,25 @@ static int lov_io_submit(const struct lu_env *env,
 	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);
@@ -850,7 +1164,7 @@ 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;
@@ -859,6 +1173,8 @@ 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);
@@ -874,6 +1190,8 @@ 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);
@@ -952,25 +1270,25 @@ 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,
@@ -981,23 +1299,23 @@ 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,
@@ -1016,11 +1334,14 @@ 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,
 };
@@ -1052,7 +1373,7 @@ 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)
@@ -1061,43 +1382,46 @@ 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
 		}
@@ -1109,23 +1433,26 @@ 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,
@@ -1141,6 +1468,7 @@ 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;
@@ -1184,6 +1512,7 @@ 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:
@@ -1191,7 +1520,8 @@ 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
 		 */
@@ -1218,4 +1548,45 @@ 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 */