From: Niu Yawei <yawei.niu@intel.com>
Date: Thu, 28 Jan 2016 07:04:02 +0000 (-0500)
Subject: LU-8998 lustreapi: composite llapi_layout
X-Git-Url: https://git.whamcloud.com/gitweb?a=commitdiff_plain;h=c2b3dba3930dcc65a4c85fcd6a9d295843d5030c;p=fs%2Flustre-release.git

LU-8998 lustreapi: composite llapi_layout

Extend the llapi_layout API to support composite layout.

- llapi_layout_comp_add():
  Add one component to an existing layout, the layout will
  be turned into composite if it was plain before adding.

- llapi_layout_comp_del():
  Delete current layout component from a composite layout,
  the component to be deleted must be the tail of layout
  component list, and it can't be the last one.

- llapi_layout_comp_extent_get/set():
  Get/Set current component extent of a layout. When set
  component extent, the layout will be turned into composite
  if it was plain.

- llapi_layout_comp_flags_get/set/clear():
  Get/Set/Clear current component flags of a composite layout.

- llapi_layout_comp_id_get():
  Get current component ID of a composite layout.

- llapi_layout_comp_move_at():
  Move the current component to a component with specified ID.

- llapi_layout_comp_move():
  Move the current component to a specified position: FIRST,
  NEXT, or LAST.

- llapi_layout_file_comp_add():
  Add component(s) to an existing composite file.

- llapi_layout_file_comp_del():
  Delete component(s) from an existing composite file.

- llapi_layout_file_comp_set():
  Set certain attribute of the specified layout component(s). Not
  implemented in PFL phase 2.

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Change-Id: I44094149636be3162fc7f8b75a90c64abf2c3c02
Reviewed-on: https://review.whamcloud.com/24866
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
---

diff --git a/lustre/include/lustre/lustreapi.h b/lustre/include/lustre/lustreapi.h
index 73a76a1..eed3a8b 100644
--- a/lustre/include/lustre/lustreapi.h
+++ b/lustre/include/lustre/lustreapi.h
@@ -692,6 +692,77 @@ int llapi_layout_file_open(const char *path, int open_flags, mode_t mode,
 int llapi_layout_file_create(const char *path, int open_flags, int mode,
 			     const struct llapi_layout *layout);
 
+/**
+ * Fetch the start and end offset of the current layout component.
+ */
+int llapi_layout_comp_extent_get(const struct llapi_layout *layout,
+				 uint64_t *start, uint64_t *end);
+/**
+ * Set the extent of current layout component.
+ */
+int llapi_layout_comp_extent_set(struct llapi_layout *layout,
+				 uint64_t start, uint64_t end);
+/**
+ * Gets the attribute flags of the current component.
+ */
+int llapi_layout_comp_flags_get(const struct llapi_layout *layout,
+				uint32_t *flags);
+/**
+ * Sets the specified flags of the current component leaving other flags as-is.
+ */
+int llapi_layout_comp_flags_set(struct llapi_layout *layout, uint32_t flags);
+/**
+ * Clears the flags specified in the flags leaving other flags as-is.
+ */
+int llapi_layout_comp_flags_clear(struct llapi_layout *layout, uint32_t flags);
+/**
+ * Fetches the file-unique component ID of the current layout component.
+ */
+int llapi_layout_comp_id_get(const struct llapi_layout *layout, uint32_t *id);
+/**
+ * Adds one component to the existing composite or plain layout.
+ */
+int llapi_layout_comp_add(struct llapi_layout *layout);
+/**
+ * Deletes the current layout component from the composite layout.
+ */
+int llapi_layout_comp_del(struct llapi_layout *layout);
+
+enum {
+	LLAPI_LAYOUT_COMP_POS_NEXT = 0,
+	LLAPI_LAYOUT_COMP_POS_FIRST = 1,
+	LLAPI_LAYOUT_COMP_POS_LAST = 2
+};
+
+/**
+ * Move the current component pointer by specified component ID.
+ */
+int llapi_layout_comp_move_at(struct llapi_layout *layout, uint32_t id);
+/**
+ * Move the current component pointer to a specified position.
+ */
+int llapi_layout_comp_move(struct llapi_layout *layout, uint32_t pos);
+/**
+ * Add layout components to an existing file.
+ */
+int llapi_layout_file_comp_add(const char *path,
+			       const struct llapi_layout *layout);
+/**
+ * Delete component(s) by the specified component id (accepting lcme_id
+ * wildcards also) from an existing file.
+ */
+int llapi_layout_file_comp_del(const char *path, uint32_t id);
+/**
+ * Change flags or other parameters of the component(s) by component ID of an
+ * existing file. The component to be modified is specified by the
+ * comp->lcme_id value, which must be an unique component ID. The new
+ * attributes are passed in by @comp and @valid is used to specify which
+ * attributes in the component are going to be changed.
+ */
+int llapi_layout_file_comp_set(const char *path,
+			       const struct llapi_layout *comp,
+			       uint32_t valid);
+
 /** @} llapi */
 
 #endif
diff --git a/lustre/tests/llapi_layout_test.c b/lustre/tests/llapi_layout_test.c
index 3d6311e..8e8405d 100644
--- a/lustre/tests/llapi_layout_test.c
+++ b/lustre/tests/llapi_layout_test.c
@@ -1309,6 +1309,203 @@ void test29(void)
 	llapi_layout_free(layout);
 }
 
+#define T30FILE		"f30"
+#define T30_DESC	"create composite file, traverse components"
+void test30(void)
+{
+	int rc, fd;
+	uint64_t start[3], end[3];
+	uint64_t s, e;
+	struct llapi_layout *layout;
+	char path[PATH_MAX];
+
+	start[0] = 0;
+	end[0] = 64 * 1024 * 1024; /* 64m */
+	start[1] = end[0];
+	end[1] = 1 * 1024 * 1024 * 1024; /* 1G */
+	start[2] = end[1];
+	end[2] = LUSTRE_EOF;
+
+	if (num_osts < 2)
+		return;
+
+	snprintf(path, sizeof(path), "%s/%s", lustre_dir, T30FILE);
+
+	rc = unlink(path);
+	ASSERTF(rc >= 0 || errno == ENOENT, "errno = %d", errno);
+
+	layout = llapi_layout_alloc();
+	ASSERTF(layout != NULL, "errno %d", errno);
+
+	rc = llapi_layout_stripe_count_set(layout, 1);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	/* add component without adjusting previous component's extent
+	 * end will fail. */
+	rc = llapi_layout_comp_add(layout);
+	ASSERTF(rc == -1 && errno == EINVAL, "rc %d, errno %d", rc, errno);
+
+	rc = llapi_layout_comp_extent_set(layout, start[0], end[0]);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	rc = llapi_layout_comp_add(layout);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	/* set non-contiguous extent will fail */
+	rc = llapi_layout_comp_extent_set(layout, end[0] * 2, end[1]);
+	ASSERTF(rc == -1 && errno == EINVAL, "rc %d, errno %d", rc, errno);
+
+	rc = llapi_layout_comp_extent_set(layout, start[1], end[1]);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	rc = llapi_layout_comp_add(layout);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	rc = llapi_layout_comp_extent_set(layout, start[2], end[2]);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	/* create composite file */
+	fd = llapi_layout_file_create(path, 0, 0660, layout);
+	ASSERTF(fd >= 0, "path = %s, fd = %d, errno = %d", path, fd, errno);
+
+	llapi_layout_free(layout);
+
+	/* traverse & verify all components */
+	layout = llapi_layout_get_by_path(path, 0);
+	ASSERTF(layout != NULL, "errno = %d", errno);
+
+	/* current component should be the tail component */
+	rc = llapi_layout_comp_extent_get(layout, &s, &e);
+	ASSERTF(rc == 0, "errno %d", errno);
+	ASSERTF(s == start[2] && e == end[2],
+		"s: %"PRIu64", e: %"PRIu64"", s, e);
+
+	rc = llapi_layout_comp_move(layout, LLAPI_LAYOUT_COMP_POS_FIRST);
+	ASSERTF(rc == 0, "rc %d, errno %d", rc, errno);
+
+	/* delete non-tail component will fail */
+	rc = llapi_layout_comp_del(layout);
+	ASSERTF(rc == -1 && errno == EINVAL, "rc %d, errno %d", rc, errno);
+
+	rc = llapi_layout_comp_extent_get(layout, &s, &e);
+	ASSERTF(rc == 0, "errno %d", errno);
+	ASSERTF(s == start[0] && e == end[0],
+		"s: %"PRIu64", e: %"PRIu64"", s, e);
+
+	rc = llapi_layout_comp_move(layout, LLAPI_LAYOUT_COMP_POS_NEXT);
+	ASSERTF(rc == 0, "rc %d, errno %d", rc,  errno);
+
+	rc = llapi_layout_comp_extent_get(layout, &s, &e);
+	ASSERTF(rc == 0, "errno %d", errno);
+	ASSERTF(s == start[1] && e == end[1],
+		"s: %"PRIu64", e: %"PRIu64"", s, e);
+
+	rc = llapi_layout_comp_move(layout, LLAPI_LAYOUT_COMP_POS_NEXT);
+	ASSERTF(rc == 0, "rc %d, errno %d", rc,  errno);
+
+	rc = llapi_layout_comp_del(layout);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	llapi_layout_free(layout);
+}
+
+#define T31FILE		"f31"
+#define T31_DESC	"add/delete component to/from existing file"
+void test31(void)
+{
+	int rc, fd, i;
+	uint64_t start[2], end[2];
+	uint64_t s, e;
+	uint32_t id[2];
+	struct llapi_layout *layout;
+	char path[PATH_MAX];
+
+	start[0] = 0;
+	end[0] = 64 * 1024 * 1024; /* 64m */
+	start[1] = end[0];
+	end[1] = LUSTRE_EOF;
+
+	if (num_osts < 2)
+		return;
+
+	snprintf(path, sizeof(path), "%s/%s", lustre_dir, T31FILE);
+
+	rc = unlink(path);
+	ASSERTF(rc >= 0 || errno == ENOENT, "errno = %d", errno);
+
+	layout = llapi_layout_alloc();
+	ASSERTF(layout != NULL, "errno %d", errno);
+
+	rc = llapi_layout_stripe_count_set(layout, 1);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	rc = llapi_layout_comp_extent_set(layout, start[0], end[0]);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	/* create composite file */
+	fd = llapi_layout_file_create(path, 0, 0660, layout);
+	ASSERTF(fd >= 0, "path = %s, fd = %d, errno = %d", path, fd, errno);
+	llapi_layout_free(layout);
+
+	layout = llapi_layout_alloc();
+	ASSERTF(layout != NULL, "errno %d", errno);
+
+	rc = llapi_layout_stripe_count_set(layout, 2);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	rc = llapi_layout_comp_extent_set(layout, start[1], end[1]);
+	ASSERTF(rc == 0, "errno %d", errno);
+
+	/* add comopnent to existing file */
+	rc = llapi_layout_file_comp_add(path, layout);
+	ASSERTF(rc == 0, "errno %d", errno);
+	llapi_layout_free(layout);
+
+	/* verify the composite layout after adding */
+	layout = llapi_layout_get_by_path(path, 0);
+	ASSERTF(layout != NULL, "errno = %d", errno);
+
+	rc = llapi_layout_comp_move(layout, LLAPI_LAYOUT_COMP_POS_FIRST);
+	ASSERTF(rc == 0, "rc %d, errno %d", rc, errno);
+	i = 0;
+	do {
+		rc = llapi_layout_comp_extent_get(layout, &s, &e);
+		ASSERTF(rc == 0 && i < 2, "i %d, errno %d", i, errno);
+		ASSERTF(s == start[i] && e == end[i],
+			"i: %d s: %"PRIu64", e: %"PRIu64"", i, s, e);
+
+		rc = llapi_layout_comp_id_get(layout, &id[i]);
+		ASSERTF(rc == 0 && id[i] != 0, "i %d, errno %d, id %d",
+			i, errno, id[i]);
+
+		rc = llapi_layout_comp_move(layout, LLAPI_LAYOUT_COMP_POS_NEXT);
+		ASSERTF(rc >= 0, "i %d, rc %d, errno %d", i, rc, errno);
+
+		i++;
+	} while (rc == 0);
+
+	llapi_layout_free(layout);
+
+	/* delete non-tail component will fail */
+	rc = llapi_layout_file_comp_del(path, id[0]);
+	ASSERTF(rc < 0 && errno == EINVAL, "rc %d, errno %d", rc, errno);
+
+	rc = llapi_layout_file_comp_del(path, id[1]);
+	ASSERTF(rc == 0, "rc %d, errno %d", rc, errno);
+
+	/* verify the composite layout after deleting */
+	layout = llapi_layout_get_by_path(path, 0);
+	ASSERTF(layout != NULL, "errno = %d", errno);
+
+	rc = llapi_layout_comp_move(layout, LLAPI_LAYOUT_COMP_POS_FIRST);
+	ASSERTF(rc == 0, "rc %d, errno %d", rc, errno);
+
+	rc = llapi_layout_comp_extent_get(layout, &s, &e);
+	ASSERTF(rc == 0, "errno %d", errno);
+	ASSERTF(s == start[0] && e == end[0],
+		"s: %"PRIu64", e: %"PRIu64"", s, e);
+}
+
 #define TEST_DESC_LEN	50
 struct test_tbl_entry {
 	void (*tte_fn)(void);
@@ -1346,8 +1543,11 @@ static struct test_tbl_entry test_tbl[] = {
 	{ .tte_fn = &test26, .tte_desc = T26_DESC, .tte_skip = false },
 	{ .tte_fn = &test27, .tte_desc = T27_DESC, .tte_skip = false },
 	{ .tte_fn = &test28, .tte_desc = T28_DESC, .tte_skip = false },
-	{ .tte_fn = &test29, .tte_desc = T29_DESC, .tte_skip = false }
+	{ .tte_fn = &test29, .tte_desc = T29_DESC, .tte_skip = false },
+	{ .tte_fn = &test30, .tte_desc = T30_DESC, .tte_skip = false },
+	{ .tte_fn = &test31, .tte_desc = T31_DESC, .tte_skip = false },
 };
+
 #define NUM_TESTS	(sizeof(test_tbl) / sizeof(struct test_tbl_entry))
 
 void print_test_desc(int test_num, const char *test_desc, const char *status)
diff --git a/lustre/tests/sanity.sh b/lustre/tests/sanity.sh
index 50573b0..8fa6fc4 100755
--- a/lustre/tests/sanity.sh
+++ b/lustre/tests/sanity.sh
@@ -2053,7 +2053,7 @@ test_27D() {
 
 	local skip27D
 	[ $(lustre_version_code $SINGLEMDS) -lt $(version_code 2.7.64) ] &&
-		skip27D = "-s 29"
+		skip27D = "-s 29,30,31"
 	llapi_layout_test -d$DIR/$tdir -p$POOL -o$OSTCOUNT $skip27D ||
 		error "llapi_layout_test failed"
 
diff --git a/lustre/utils/liblustreapi.c b/lustre/utils/liblustreapi.c
index 8db34b3..a08537f 100644
--- a/lustre/utils/liblustreapi.c
+++ b/lustre/utils/liblustreapi.c
@@ -2050,11 +2050,9 @@ static int sattr_get_defaults(const char *const fsname,
  * next time they are needed. Only a single filesystem's attributes are
  * cached at a time.
  */
-static int sattr_cache_get_defaults(const char *const fsname,
-                                    const char *const pathname,
-                                    unsigned int *scount,
-                                    unsigned int *ssize,
-                                    unsigned int *soffset)
+int sattr_cache_get_defaults(const char *const fsname,
+			     const char *const pathname, unsigned int *scount,
+			     unsigned int *ssize, unsigned int *soffset)
 {
         static struct {
                 char fsname[PATH_MAX + 1];
diff --git a/lustre/utils/liblustreapi_layout.c b/lustre/utils/liblustreapi_layout.c
index c3d9ea6..813e400 100644
--- a/lustre/utils/liblustreapi_layout.c
+++ b/lustre/utils/liblustreapi_layout.c
@@ -36,31 +36,78 @@
 #include <limits.h>
 #include <sys/xattr.h>
 
+#include <libcfs/util/list.h>
 #include <lustre/lustreapi.h>
 #include <lustre/lustre_idl.h>
 #include "lustreapi_internal.h"
 
 /**
+ * Layout component, which contains all attributes of a plain
+ * V1/V3 layout.
+ */
+struct llapi_layout_comp {
+	uint64_t	llc_pattern;
+	uint64_t	llc_stripe_size;
+	uint64_t	llc_stripe_count;
+	uint64_t	llc_stripe_offset;
+	/* Add 1 so user always gets back a null terminated string. */
+	char		llc_pool_name[LOV_MAXPOOLNAME + 1];
+	/** Number of objects in llc_objects array if was initialized. */
+	uint32_t	llc_objects_count;
+	struct		lov_user_ost_data_v1 *llc_objects;
+	/* fields used only for composite layouts */
+	struct lu_extent	llc_extent;	/* [start, end) of component */
+	uint32_t		llc_id;		/* unique ID of component */
+	uint32_t		llc_flags;	/* LCME_FL_* flags */
+	struct list_head	llc_list;	/* linked to the llapi_layout
+						   components list */
+};
+
+/**
  * An Opaque data type abstracting the layout of a Lustre file.
- *
- * Duplicate the fields we care about from struct lov_user_md_v3.
- * Deal with v1 versus v3 format issues only when we read or write
- * files.
  */
 struct llapi_layout {
-	uint32_t	llot_magic;
-	uint64_t	llot_pattern;
-	uint64_t	llot_stripe_size;
-	uint64_t	llot_stripe_count;
-	uint64_t	llot_stripe_offset;
-	/* Add 1 so user always gets back a null terminated string. */
-	char		llot_pool_name[LOV_MAXPOOLNAME + 1];
-	/** Number of objects in llot_objects array if was initialized. */
-	uint32_t	llot_objects_count;
-	struct		lov_user_ost_data_v1 *llot_objects;
+	uint32_t	llot_magic; /* LLAPI_LAYOUT_MAGIC */
+	uint32_t	llot_gen;
+	uint32_t	llot_flags;
+	bool		llot_is_composite;
+	/* Cursor pointing to one of the components in llot_comp_list */
+	struct llapi_layout_comp *llot_cur_comp;
+	struct list_head	  llot_comp_list;
 };
 
 /**
+ * Compute the number of elements in the lmm_objects array of \a lum
+ * with size \a lum_size.
+ *
+ * \param[in] lum	the struct lov_user_md to check
+ * \param[in] lum_size	the number of bytes in \a lum
+ *
+ * \retval		number of elements in array lum->lmm_objects
+ */
+static int llapi_layout_objects_in_lum(struct lov_user_md *lum, size_t lum_size)
+{
+	uint32_t magic;
+	size_t base_size;
+
+	if (lum_size < lov_user_md_size(0, LOV_MAGIC_V1))
+		return 0;
+
+	if (lum->lmm_magic == __swab32(LOV_MAGIC_V1) ||
+	    lum->lmm_magic == __swab32(LOV_MAGIC_V3))
+		magic = __swab32(lum->lmm_magic);
+	else
+		magic = lum->lmm_magic;
+
+	base_size = lov_user_md_size(0, magic);
+
+	if (lum_size <= base_size)
+		return 0;
+	else
+		return (lum_size - base_size) / sizeof(lum->lmm_objects[0]);
+}
+
+/**
  * Byte-swap the fields of struct lov_user_md.
  *
  * XXX Rather than duplicating swabbing code here, we should eventually
@@ -68,31 +115,71 @@ struct llapi_layout {
  * into a library that can be shared between kernel and user code.
  */
 static void
-llapi_layout_swab_lov_user_md(struct lov_user_md *lum, int object_count)
+llapi_layout_swab_lov_user_md(struct lov_user_md *lum, int lum_size)
 {
-	int i;
-	struct lov_user_md_v3 *lumv3 = (struct lov_user_md_v3 *)lum;
+	int i, j, ent_count, obj_count;
+	struct lov_comp_md_v1 *comp_v1 = NULL;
+	struct lov_comp_md_entry_v1 *ent;
 	struct lov_user_ost_data *lod;
 
-	__swab32s(&lum->lmm_magic);
-	__swab32s(&lum->lmm_pattern);
-	__swab32s(&lum->lmm_stripe_size);
-	__swab16s(&lum->lmm_stripe_count);
-	__swab16s(&lum->lmm_stripe_offset);
+	if (lum->lmm_magic != __swab32(LOV_MAGIC_V1) &&
+	    lum->lmm_magic != __swab32(LOV_MAGIC_V3) &&
+	    lum->lmm_magic != __swab32(LOV_MAGIC_COMP_V1))
+		return;
+
+	if (lum->lmm_magic == __swab32(LOV_MAGIC_COMP_V1))
+		comp_v1 = (struct lov_comp_md_v1 *)lum;
+
+	if (comp_v1 != NULL) {
+		__swab32s(&comp_v1->lcm_magic);
+		__swab32s(&comp_v1->lcm_size);
+		__swab32s(&comp_v1->lcm_layout_gen);
+		__swab16s(&comp_v1->lcm_flags);
+		__swab16s(&comp_v1->lcm_entry_count);
+		ent_count = comp_v1->lcm_entry_count;
+	} else {
+		ent_count = 1;
+	}
 
-	if (lum->lmm_magic != LOV_MAGIC_V1)
-		lod = lumv3->lmm_objects;
-	else
-		lod = lum->lmm_objects;
+	for (i = 0; i < ent_count; i++) {
+		if (comp_v1 != NULL) {
+			ent = &comp_v1->lcm_entries[i];
+			__swab32s(&ent->lcme_id);
+			__swab32s(&ent->lcme_flags);
+			__swab64s(&ent->lcme_extent.e_start);
+			__swab64s(&ent->lcme_extent.e_end);
+			__swab32s(&ent->lcme_offset);
+			__swab32s(&ent->lcme_size);
+
+			lum = (struct lov_user_md *)((char *)comp_v1 +
+					ent->lcme_offset);
+			lum_size = ent->lcme_size;
+		}
+		obj_count = llapi_layout_objects_in_lum(lum, lum_size);
+
+		__swab32s(&lum->lmm_magic);
+		__swab32s(&lum->lmm_pattern);
+		__swab32s(&lum->lmm_stripe_size);
+		__swab16s(&lum->lmm_stripe_count);
+		__swab16s(&lum->lmm_stripe_offset);
+
+		if (lum->lmm_magic != LOV_MAGIC_V1) {
+			struct lov_user_md_v3 *v3;
+			v3 = (struct lov_user_md_v3 *)lum;
+			lod = v3->lmm_objects;
+		} else {
+			lod = lum->lmm_objects;
+		}
 
-	for (i = 0; i < object_count; i++)
-		__swab32s(&lod[i].l_ost_idx);
+		for (j = 0; j < obj_count; j++)
+			__swab32s(&lod[j].l_ost_idx);
+	}
 }
 
 /**
- * (Re-)allocate llot_objects[] to \a num_stripes stripes.
+ * (Re-)allocate llc_objects[] to \a num_stripes stripes.
  *
- * Copy over existing llot_objects[], if any, to the new llot_objects[].
+ * Copy over existing llc_objects[], if any, to the new llc_objects[].
  *
  * \param[in] layout		existing layout to be modified
  * \param[in] num_stripes	number of stripes in new layout
@@ -100,8 +187,8 @@ llapi_layout_swab_lov_user_md(struct lov_user_md *lum, int object_count)
  * \retval	0 if the objects are re-allocated successfully
  * \retval	-1 on error with errno set
  */
-static int __llapi_layout_objects_realloc(struct llapi_layout *layout,
-					  unsigned int new_stripes)
+static int __llapi_comp_objects_realloc(struct llapi_layout_comp *comp,
+					unsigned int new_stripes)
 {
 	struct lov_user_ost_data_v1 *new_objects;
 	unsigned int i;
@@ -111,139 +198,285 @@ static int __llapi_layout_objects_realloc(struct llapi_layout *layout,
 		return -1;
 	}
 
-	if (new_stripes == 0 && layout->llot_objects_count == 0)
+	if (new_stripes == comp->llc_objects_count)
 		return 0;
 
-	if (new_stripes != 0 && new_stripes <= layout->llot_objects_count)
+	if (new_stripes != 0 && new_stripes <= comp->llc_objects_count)
 		return 0;
 
-	new_objects = realloc(layout->llot_objects,
+	new_objects = realloc(comp->llc_objects,
 			      sizeof(*new_objects) * new_stripes);
 	if (new_objects == NULL && new_stripes != 0) {
 		errno = ENOMEM;
 		return -1;
 	}
 
-	for (i = layout->llot_objects_count; i < new_stripes; i++)
+	for (i = comp->llc_objects_count; i < new_stripes; i++)
 		new_objects[i].l_ost_idx = LLAPI_LAYOUT_IDX_MAX;
 
-	if (new_stripes == 0)
-		layout->llot_objects = NULL;
-	else
-		layout->llot_objects = new_objects;
-	layout->llot_objects_count = new_stripes;
+	comp->llc_objects = new_objects;
+	comp->llc_objects_count = new_stripes;
 
 	return 0;
 }
 
 /**
- * Allocate storage for a llapi_layout with \a num_stripes stripes.
+ * Allocate storage for a llapi_layout_comp with \a num_stripes stripes.
  *
  * \param[in] num_stripes	number of stripes in new layout
  *
  * \retval	valid pointer if allocation succeeds
  * \retval	NULL if allocation fails
  */
-static struct llapi_layout *__llapi_layout_alloc(unsigned int num_stripes)
+static struct llapi_layout_comp *__llapi_comp_alloc(unsigned int num_stripes)
 {
-	struct llapi_layout *layout;
+	struct llapi_layout_comp *comp;
 
 	if (num_stripes > LOV_MAX_STRIPE_COUNT) {
 		errno = EINVAL;
 		return NULL;
 	}
 
+	comp = calloc(1, sizeof(*comp));
+	if (comp == NULL) {
+		errno = ENOMEM;
+		return NULL;
+	}
+
+	comp->llc_objects = NULL;
+	comp->llc_objects_count = 0;
+
+	if (__llapi_comp_objects_realloc(comp, num_stripes) < 0) {
+		free(comp);
+		return NULL;
+	}
+
+	/* Set defaults. */
+	comp->llc_pattern = LLAPI_LAYOUT_DEFAULT;
+	comp->llc_stripe_size = LLAPI_LAYOUT_DEFAULT;
+	comp->llc_stripe_count = LLAPI_LAYOUT_DEFAULT;
+	comp->llc_stripe_offset = LLAPI_LAYOUT_DEFAULT;
+	comp->llc_pool_name[0] = '\0';
+	comp->llc_extent.e_start = 0;
+	comp->llc_extent.e_end = LUSTRE_EOF;
+	comp->llc_flags = 0;
+	comp->llc_id = 0;
+	INIT_LIST_HEAD(&comp->llc_list);
+
+	return comp;
+}
+
+/**
+ * Free memory allocated for \a comp
+ *
+ * \param[in] comp	previously allocated by __llapi_comp_alloc()
+ */
+static void __llapi_comp_free(struct llapi_layout_comp *comp)
+{
+	if (comp->llc_objects != NULL)
+		free(comp->llc_objects);
+	free(comp);
+}
+
+/**
+ * Free memory allocated for \a layout.
+ *
+ * \param[in] layout	previously allocated by llapi_layout_alloc()
+ */
+void llapi_layout_free(struct llapi_layout *layout)
+{
+	struct llapi_layout_comp *comp, *n;
+
+	if (layout == NULL)
+		return;
+
+	list_for_each_entry_safe(comp, n, &layout->llot_comp_list, llc_list) {
+		list_del_init(&comp->llc_list);
+		__llapi_comp_free(comp);
+	}
+	free(layout);
+}
+
+/**
+ * Allocate and initialize a llapi_layout structure.
+ *
+ * \retval	valid llapi_layout pointer on success
+ * \retval	NULL if memory allocation fails
+ */
+static struct llapi_layout *__llapi_layout_alloc(void)
+{
+	struct llapi_layout *layout;
+
 	layout = calloc(1, sizeof(*layout));
 	if (layout == NULL) {
 		errno = ENOMEM;
 		return NULL;
 	}
 
-	layout->llot_objects = NULL;
-	layout->llot_objects_count = 0;
+	/* Set defaults. */
+	layout->llot_magic = LLAPI_LAYOUT_MAGIC;
+	layout->llot_gen = 0;
+	layout->llot_flags = 0;
+	layout->llot_is_composite = false;
+	layout->llot_cur_comp = NULL;
+	INIT_LIST_HEAD(&layout->llot_comp_list);
+
+	return layout;
+}
+
+/**
+ * Allocate and initialize a new plain layout.
+ *
+ * \retval	valid llapi_layout pointer on success
+ * \retval	NULL if memory allocation fails
+ */
+struct llapi_layout *llapi_layout_alloc(void)
+{
+	struct llapi_layout_comp *comp;
+	struct llapi_layout *layout;
+
+	layout = __llapi_layout_alloc();
+	if (layout == NULL)
+		return NULL;
 
-	if (__llapi_layout_objects_realloc(layout, num_stripes) < 0) {
+	comp = __llapi_comp_alloc(0);
+	if (comp == NULL) {
 		free(layout);
-		layout = NULL;
+		return NULL;
 	}
 
+	list_add_tail(&comp->llc_list, &layout->llot_comp_list);
+	layout->llot_cur_comp = comp;
+
 	return layout;
 }
 
 /**
- * Copy the data from a lov_user_md to a newly allocated llapi_layout.
- *
+ * Convert the data from a lov_user_md to a newly allocated llapi_layout.
  * The caller is responsible for freeing the returned pointer.
  *
  * \param[in] lum	LOV user metadata structure to copy data from
+ * \param[in] lum_size	size the the lum passed in
  *
  * \retval		valid llapi_layout pointer on success
  * \retval		NULL if memory allocation fails
  */
 static struct llapi_layout *
-llapi_layout_from_lum(const struct lov_user_md *lum, size_t object_count)
+llapi_layout_from_lum(const struct lov_user_md *lum, int lum_size)
 {
+	struct lov_comp_md_v1 *comp_v1 = NULL;
+	struct lov_comp_md_entry_v1 *ent;
+	struct lov_user_md *v1;
 	struct llapi_layout *layout;
-	size_t objects_sz;
+	struct llapi_layout_comp *comp;
+	int i, ent_count = 0, obj_count;
 
-	objects_sz = object_count * sizeof(lum->lmm_objects[0]);
-
-	layout = __llapi_layout_alloc(object_count);
+	layout = __llapi_layout_alloc();
 	if (layout == NULL)
 		return NULL;
 
-	layout->llot_magic = LLAPI_LAYOUT_MAGIC;
+	if (lum->lmm_magic == LOV_MAGIC_COMP_V1) {
+		comp_v1 = (struct lov_comp_md_v1 *)lum;
+		ent_count = comp_v1->lcm_entry_count;
+		layout->llot_is_composite = true;
+		layout->llot_gen = comp_v1->lcm_layout_gen;
+		layout->llot_flags = comp_v1->lcm_flags;
+	} else if (lum->lmm_magic == LOV_MAGIC_V1 ||
+		   lum->lmm_magic == LOV_MAGIC_V3) {
+		ent_count = 1;
+		layout->llot_is_composite = false;
+	}
 
-	if (lum->lmm_pattern == LOV_PATTERN_RAID0)
-		layout->llot_pattern = LLAPI_LAYOUT_RAID0;
-	else
-		/* Lustre only supports RAID0 for now. */
-		layout->llot_pattern = lum->lmm_pattern;
+	if (ent_count == 0) {
+		errno = EINVAL;
+		goto error;
+	}
 
-	if (lum->lmm_stripe_size == 0)
-		layout->llot_stripe_size = LLAPI_LAYOUT_DEFAULT;
-	else
-		layout->llot_stripe_size = lum->lmm_stripe_size;
+	v1 = (struct lov_user_md *)lum;
+	for (i = 0; i < ent_count; i++) {
+		if (comp_v1 != NULL) {
+			ent = &comp_v1->lcm_entries[i];
+			v1 = (struct lov_user_md *)((char *)comp_v1 +
+				ent->lcme_offset);
+			lum_size = ent->lcme_size;
+		} else {
+			ent = NULL;
+		}
 
-	if (lum->lmm_stripe_count == (typeof(lum->lmm_stripe_count))-1)
-		layout->llot_stripe_count = LLAPI_LAYOUT_WIDE;
-	else if (lum->lmm_stripe_count == 0)
-		layout->llot_stripe_count = LLAPI_LAYOUT_DEFAULT;
-	else
-		layout->llot_stripe_count = lum->lmm_stripe_count;
+		obj_count = llapi_layout_objects_in_lum(v1, lum_size);
+		comp = __llapi_comp_alloc(obj_count);
+		if (comp == NULL)
+			goto error;
 
-	if (lum->lmm_stripe_offset == (typeof(lum->lmm_stripe_offset))-1)
-		layout->llot_stripe_offset = LLAPI_LAYOUT_DEFAULT;
-	else
-		layout->llot_stripe_offset = lum->lmm_stripe_offset;
-
-	if (lum->lmm_magic != LOV_USER_MAGIC_V1) {
-		const struct lov_user_md_v3 *lumv3;
-		lumv3 = (struct lov_user_md_v3 *)lum;
-		snprintf(layout->llot_pool_name, sizeof(layout->llot_pool_name),
-			 "%s", lumv3->lmm_pool_name);
-		memcpy(layout->llot_objects, lumv3->lmm_objects, objects_sz);
-	} else {
-		const struct lov_user_md_v1 *lumv1;
-		lumv1 = (struct lov_user_md_v1 *)lum;
-		memcpy(layout->llot_objects, lumv1->lmm_objects, objects_sz);
-	}
+		if (ent != NULL) {
+			comp->llc_extent.e_start = ent->lcme_extent.e_start;
+			comp->llc_extent.e_end = ent->lcme_extent.e_end;
+			comp->llc_id = ent->lcme_id;
+			comp->llc_flags = ent->lcme_flags;
+		} else {
+			comp->llc_extent.e_start = 0;
+			comp->llc_extent.e_end = LUSTRE_EOF;
+			comp->llc_id = 0;
+			comp->llc_flags = 0;
+		}
+
+		if (v1->lmm_pattern == LOV_PATTERN_RAID0)
+			comp->llc_pattern = LLAPI_LAYOUT_RAID0;
+		else
+			/* Lustre only supports RAID0 for now. */
+			comp->llc_pattern = v1->lmm_pattern;
+
+		if (v1->lmm_stripe_size == 0)
+			comp->llc_stripe_size = LLAPI_LAYOUT_DEFAULT;
+		else
+			comp->llc_stripe_size = v1->lmm_stripe_size;
+
+		if (v1->lmm_stripe_count == (typeof(v1->lmm_stripe_count))-1)
+			comp->llc_stripe_count = LLAPI_LAYOUT_WIDE;
+		else if (v1->lmm_stripe_count == 0)
+			comp->llc_stripe_count = LLAPI_LAYOUT_DEFAULT;
+		else
+			comp->llc_stripe_count = v1->lmm_stripe_count;
+
+		if (v1->lmm_stripe_offset ==
+		    (typeof(v1->lmm_stripe_offset))-1)
+			comp->llc_stripe_offset = LLAPI_LAYOUT_DEFAULT;
+		else
+			comp->llc_stripe_offset = v1->lmm_stripe_offset;
+
+		if (v1->lmm_magic != LOV_USER_MAGIC_V1) {
+			const struct lov_user_md_v3 *lumv3;
+			lumv3 = (struct lov_user_md_v3 *)v1;
+			snprintf(comp->llc_pool_name,
+				 sizeof(comp->llc_pool_name),
+				 "%s", lumv3->lmm_pool_name);
+			memcpy(comp->llc_objects, lumv3->lmm_objects,
+			       obj_count * sizeof(lumv3->lmm_objects[0]));
+		} else {
+			const struct lov_user_md_v1 *lumv1;
+			lumv1 = (struct lov_user_md_v1 *)v1;
+			memcpy(comp->llc_objects, lumv1->lmm_objects,
+			       obj_count * sizeof(lumv1->lmm_objects[0]));
+		}
+
+		if (obj_count != 0)
+			comp->llc_stripe_offset =
+				comp->llc_objects[0].l_ost_idx;
 
-	if (object_count != 0)
-		layout->llot_stripe_offset = layout->llot_objects[0].l_ost_idx;
+		list_add_tail(&comp->llc_list, &layout->llot_comp_list);
+		layout->llot_cur_comp = comp;
+	}
 
 	return layout;
+error:
+	llapi_layout_free(layout);
+	return NULL;
 }
 
 /**
- * Copy the data from a llapi_layout to a newly allocated lov_user_md.
- *
+ * Convert the data from a llapi_layout to a newly allocated lov_user_md.
  * The caller is responsible for freeing the returned pointer.
  *
- * The current version of this API doesn't support specifying the OST
- * index of arbitrary stripes, only stripe 0 via lmm_stripe_offset.
- * There is therefore no need to copy the lmm_objects array.
- *
  * \param[in] layout	the layout to copy from
  *
  * \retval	valid lov_user_md pointer on success
@@ -252,86 +485,152 @@ llapi_layout_from_lum(const struct lov_user_md *lum, size_t object_count)
 static struct lov_user_md *
 llapi_layout_to_lum(const struct llapi_layout *layout)
 {
-	struct lov_user_md *lum;
-	size_t lum_size;
-	uint32_t magic = LOV_USER_MAGIC_V1;
-	uint64_t pattern = layout->llot_pattern;
-	struct lov_user_ost_data *lmm_objects;
-	int obj_count = 0, i;
-
-	if ((pattern & LLAPI_LAYOUT_SPECIFIC) != 0) {
-		if (layout->llot_objects_count < layout->llot_stripe_count) {
-			errno = EINVAL;
-			return NULL;
-		}
-		magic = LOV_USER_MAGIC_SPECIFIC;
-		obj_count = layout->llot_stripe_count;
-		pattern &= ~LLAPI_LAYOUT_SPECIFIC;
-	} else if (strlen(layout->llot_pool_name) != 0) {
-		magic = LOV_USER_MAGIC_V3;
+	struct llapi_layout_comp *comp;
+	struct lov_comp_md_v1 *comp_v1 = NULL;
+	struct lov_comp_md_entry_v1 *ent;
+	struct lov_user_md *lum = NULL;
+	size_t lum_size = 0;
+	int ent_idx = 0;
+	uint32_t offset = 0;
+
+	if (layout == NULL ||
+	    list_empty((struct list_head *)&layout->llot_comp_list)) {
+		errno = EINVAL;
+		return NULL;
 	}
 
-	/*
-	 * All stripes must be specified when the pattern contains
-	 * LLAPI_LAYOUT_SPECIFIC
-	 */
-	for (i = 0; i < obj_count; i++) {
-		if (layout->llot_objects[i].l_ost_idx ==
-		    LLAPI_LAYOUT_IDX_MAX) {
-			errno = EINVAL;
+	/* Allocate header of lov_comp_md_v1 if necessary */
+	if (layout->llot_is_composite) {
+		int comp_cnt = 0;
+
+		list_for_each_entry(comp, &layout->llot_comp_list, llc_list)
+			comp_cnt++;
+
+		lum_size = sizeof(*comp_v1) + comp_cnt * sizeof(*ent);
+		lum = malloc(lum_size);
+		if (lum == NULL) {
+			errno = ENOMEM;
 			return NULL;
 		}
+		comp_v1 = (struct lov_comp_md_v1 *)lum;
+		comp_v1->lcm_magic = LOV_USER_MAGIC_COMP_V1;
+		comp_v1->lcm_size = lum_size;
+		comp_v1->lcm_layout_gen = 0;
+		comp_v1->lcm_flags = 0;
+		comp_v1->lcm_entry_count = comp_cnt;
+		offset += lum_size;
 	}
 
-	lum_size = lov_user_md_size(obj_count, magic);
-	lum = malloc(lum_size);
-	if (lum == NULL)
-		return NULL;
-
-	lum->lmm_magic = magic;
+	list_for_each_entry(comp, &layout->llot_comp_list, llc_list) {
+		struct lov_user_md *blob;
+		size_t blob_size;
+		uint32_t magic;
+		int i, obj_count = 0;
+		struct lov_user_ost_data *lmm_objects;
+		uint64_t pattern = comp->llc_pattern;
+
+		if ((pattern & LLAPI_LAYOUT_SPECIFIC) != 0) {
+			if (comp->llc_objects_count <
+			    comp->llc_stripe_count) {
+				errno = EINVAL;
+				goto error;
+			}
+			magic = LOV_USER_MAGIC_SPECIFIC;
+			obj_count = comp->llc_stripe_count;
+			pattern &= ~LLAPI_LAYOUT_SPECIFIC;
+		} else if (strlen(comp->llc_pool_name) != 0) {
+			magic = LOV_USER_MAGIC_V3;
+		} else {
+			magic = LOV_USER_MAGIC_V1;
+		}
+		/* All stripes must be specified when the pattern contains
+		 * LLAPI_LAYOUT_SPECIFIC */
+		for (i = 0; i < obj_count; i++) {
+			if (comp->llc_objects[i].l_ost_idx ==
+			    LLAPI_LAYOUT_IDX_MAX) {
+				errno = EINVAL;
+				goto error;
+			}
+		}
 
-	if (pattern == LLAPI_LAYOUT_DEFAULT)
-		lum->lmm_pattern = 0;
-	else if (pattern == LLAPI_LAYOUT_RAID0)
-		lum->lmm_pattern = LOV_PATTERN_RAID0;
-	else
-		lum->lmm_pattern = pattern;
+		blob_size = lov_user_md_size(obj_count, magic);
+		blob = realloc(lum, lum_size + blob_size);
+		if (blob == NULL) {
+			errno = ENOMEM;
+			goto error;
+		} else {
+			lum = blob;
+			blob = (struct lov_user_md *)((char *)lum + lum_size);
+			lum_size += blob_size;
+		}
 
-	if (layout->llot_stripe_size == LLAPI_LAYOUT_DEFAULT)
-		lum->lmm_stripe_size = 0;
-	else
-		lum->lmm_stripe_size = layout->llot_stripe_size;
+		blob->lmm_magic = magic;
+		if (pattern == LLAPI_LAYOUT_DEFAULT)
+			blob->lmm_pattern = 0;
+		else if (pattern == LLAPI_LAYOUT_RAID0)
+			blob->lmm_pattern = LOV_PATTERN_RAID0;
+		else
+			blob->lmm_pattern = pattern;
 
-	if (layout->llot_stripe_count == LLAPI_LAYOUT_DEFAULT)
-		lum->lmm_stripe_count = 0;
-	else if (layout->llot_stripe_count == LLAPI_LAYOUT_WIDE)
-		lum->lmm_stripe_count = LOV_ALL_STRIPES;
-	else
-		lum->lmm_stripe_count = layout->llot_stripe_count;
+		if (comp->llc_stripe_size == LLAPI_LAYOUT_DEFAULT)
+			blob->lmm_stripe_size = 0;
+		else
+			blob->lmm_stripe_size = comp->llc_stripe_size;
 
-	if (layout->llot_stripe_offset == LLAPI_LAYOUT_DEFAULT)
-		lum->lmm_stripe_offset = -1;
-	else
-		lum->lmm_stripe_offset = layout->llot_stripe_offset;
+		if (comp->llc_stripe_count == LLAPI_LAYOUT_DEFAULT)
+			blob->lmm_stripe_count = 0;
+		else if (comp->llc_stripe_count == LLAPI_LAYOUT_WIDE)
+			blob->lmm_stripe_count = LOV_ALL_STRIPES;
+		else
+			blob->lmm_stripe_count = comp->llc_stripe_count;
 
-	if (magic == LOV_USER_MAGIC_V3 || magic == LOV_USER_MAGIC_SPECIFIC) {
-		struct lov_user_md_v3 *lumv3 = (struct lov_user_md_v3 *)lum;
+		if (comp->llc_stripe_offset == LLAPI_LAYOUT_DEFAULT)
+			blob->lmm_stripe_offset = -1;
+		else
+			blob->lmm_stripe_offset = comp->llc_stripe_offset;
+
+		if (magic == LOV_USER_MAGIC_V3 ||
+		    magic == LOV_USER_MAGIC_SPECIFIC) {
+			struct lov_user_md_v3 *lumv3 =
+				(struct lov_user_md_v3 *)blob;
+
+			if (comp->llc_pool_name[0] != '\0') {
+				strncpy(lumv3->lmm_pool_name,
+					comp->llc_pool_name,
+					sizeof(lumv3->lmm_pool_name));
+			} else {
+				memset(lumv3->lmm_pool_name, 0,
+				       sizeof(lumv3->lmm_pool_name));
+			}
+			lmm_objects = lumv3->lmm_objects;
+		} else {
+			lmm_objects = blob->lmm_objects;
+		}
 
-		if (strlen(layout->llot_pool_name)) {
-			strncpy(lumv3->lmm_pool_name, layout->llot_pool_name,
-				sizeof(lumv3->lmm_pool_name));
+		for (i = 0; i < obj_count; i++)
+			lmm_objects[i].l_ost_idx =
+				comp->llc_objects[i].l_ost_idx;
+
+		if (comp_v1 != NULL) {
+			ent = &comp_v1->lcm_entries[ent_idx];
+			ent->lcme_id = comp->llc_id;
+			ent->lcme_flags = comp->llc_flags;
+			ent->lcme_extent.e_start = comp->llc_extent.e_start;
+			ent->lcme_extent.e_end = comp->llc_extent.e_end;
+			ent->lcme_size = blob_size;
+			ent->lcme_offset = offset;
+			offset += blob_size;
+			comp_v1->lcm_size += blob_size;
+			ent_idx++;
 		} else {
-			memset(lumv3->lmm_pool_name, 0, LOV_MAXPOOLNAME);
+			break;
 		}
-		lmm_objects = lumv3->lmm_objects;
-	} else {
-		lmm_objects = lum->lmm_objects;
 	}
 
-	for (i = 0; i < obj_count; i++)
-		lmm_objects[i].l_ost_idx = layout->llot_objects[i].l_ost_idx;
-
 	return lum;
+error:
+	free(lum);
+	return NULL;
 }
 
 /**
@@ -355,66 +654,89 @@ static void get_parent_dir(const char *path, char *buf, size_t size)
 }
 
 /**
- * Substitute unspecified attribute values in \a dest with
- * values from \a src.
+ * Substitute unspecified attribute values in \a layout with values
+ * from fs global settings. (lov.stripesize, lov.stripecount,
+ * lov.stripeoffset)
  *
- * \param[in] src	layout to inherit values from
- * \param[in] dest	layout to receive inherited values
+ * \param[in] layout	layout to inherit values from
+ * \param[in] path	file path of the filesystem
  */
-static void inherit_layout_attributes(const struct llapi_layout *src,
-					struct llapi_layout *dest)
+static void inherit_sys_attributes(struct llapi_layout *layout,
+				   const char *path)
 {
-	if (dest->llot_pattern == LLAPI_LAYOUT_DEFAULT)
-		dest->llot_pattern = src->llot_pattern;
-
-	if (dest->llot_stripe_size == LLAPI_LAYOUT_DEFAULT)
-		dest->llot_stripe_size = src->llot_stripe_size;
-
-	if (dest->llot_stripe_count == LLAPI_LAYOUT_DEFAULT)
-		dest->llot_stripe_count = src->llot_stripe_count;
+	struct llapi_layout_comp *comp;
+	unsigned int ssize, scount, soffset;
+	int rc;
 
-	if (dest->llot_stripe_offset == LLAPI_LAYOUT_DEFAULT)
-		dest->llot_stripe_offset = src->llot_stripe_offset;
+	rc = sattr_cache_get_defaults(NULL, path, &scount, &ssize, &soffset);
+	if (rc)
+		return;
+
+	list_for_each_entry(comp, &layout->llot_comp_list, llc_list) {
+		if (comp->llc_pattern == LLAPI_LAYOUT_DEFAULT)
+			comp->llc_pattern = LLAPI_LAYOUT_RAID0;
+		if (comp->llc_stripe_size == LLAPI_LAYOUT_DEFAULT)
+			comp->llc_stripe_size = ssize;
+		if (comp->llc_stripe_count == LLAPI_LAYOUT_DEFAULT)
+			comp->llc_stripe_count = scount;
+		if (comp->llc_stripe_offset == LLAPI_LAYOUT_DEFAULT)
+			comp->llc_stripe_offset = soffset;
+	}
 }
 
 /**
- * Test if all attributes of \a layout are specified.
+ * Get the current component of \a layout.
  *
- * \param[in] layout	the layout to check
+ * \param[in] layout	layout to get current component
  *
- * \retval true		all attributes are specified
- * \retval false	at least one attribute is unspecified
+ * \retval	valid llapi_layout_comp pointer on success
+ * \retval	NULL on error
  */
-static bool is_fully_specified(const struct llapi_layout *layout)
+static struct llapi_layout_comp *
+__llapi_layout_cur_comp(const struct llapi_layout *layout)
 {
-	return  layout->llot_pattern != LLAPI_LAYOUT_DEFAULT &&
-		layout->llot_stripe_size != LLAPI_LAYOUT_DEFAULT &&
-		layout->llot_stripe_count != LLAPI_LAYOUT_DEFAULT;
+	struct llapi_layout_comp *comp;
+
+	if (layout == NULL || layout->llot_magic != LLAPI_LAYOUT_MAGIC) {
+		errno = EINVAL;
+		return NULL;
+	}
+	if (layout->llot_cur_comp == NULL) {
+		errno = EINVAL;
+		return NULL;
+	}
+	/* Verify data consistency */
+	list_for_each_entry(comp, &layout->llot_comp_list, llc_list)
+		if (comp == layout->llot_cur_comp)
+			return comp;
+	errno = EFAULT;
+	return NULL;
 }
 
 /**
- * Allocate and initialize a new layout.
+ * Test if any attributes of \a layout are specified.
  *
- * \retval	valid llapi_layout pointer on success
- * \retval	NULL if memory allocation fails
+ * \param[in] layout	the layout to check
+ *
+ * \retval true		any attributes are specified
+ * \retval false	all attributes are unspecified
  */
-struct llapi_layout *llapi_layout_alloc(void)
+static bool is_any_specified(const struct llapi_layout *layout)
 {
-	struct llapi_layout *layout;
+	struct llapi_layout_comp *comp;
 
-	layout = __llapi_layout_alloc(0);
-	if (layout == NULL)
-		return layout;
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return false;
 
-	/* Set defaults. */
-	layout->llot_magic = LLAPI_LAYOUT_MAGIC;
-	layout->llot_pattern = LLAPI_LAYOUT_DEFAULT;
-	layout->llot_stripe_size = LLAPI_LAYOUT_DEFAULT;
-	layout->llot_stripe_count = LLAPI_LAYOUT_DEFAULT;
-	layout->llot_stripe_offset = LLAPI_LAYOUT_DEFAULT;
-	layout->llot_pool_name[0] = '\0';
+	if (layout->llot_is_composite)
+		return true;
 
-	return layout;
+	return comp->llc_pattern != LLAPI_LAYOUT_DEFAULT ||
+	       comp->llc_stripe_size != LLAPI_LAYOUT_DEFAULT ||
+	       comp->llc_stripe_count != LLAPI_LAYOUT_DEFAULT ||
+	       comp->llc_stripe_offset != LLAPI_LAYOUT_DEFAULT ||
+	       strlen(comp->llc_pool_name);
 }
 
 /**
@@ -431,47 +753,56 @@ static bool llapi_layout_lum_truncated(struct lov_user_md *lum, size_t lum_size)
 {
 	uint32_t magic;
 
-	if (lum_size < lov_user_md_size(0, LOV_MAGIC_V1))
-		return false;
-
-	if (lum->lmm_magic == __swab32(LOV_MAGIC_V1) ||
-	    lum->lmm_magic == __swab32(LOV_MAGIC_V3))
-		magic = __swab32(lum->lmm_magic);
+	if (lum_size < sizeof(lum->lmm_magic))
+		return true;
+
+	if (lum->lmm_magic == LOV_MAGIC_V1 ||
+	    lum->lmm_magic == __swab32(LOV_MAGIC_V1))
+		magic = LOV_MAGIC_V1;
+	else if (lum->lmm_magic == LOV_MAGIC_V3 ||
+		 lum->lmm_magic == __swab32(LOV_MAGIC_V3))
+		magic = LOV_MAGIC_V3;
+	else if (lum->lmm_magic == LOV_MAGIC_COMP_V1 ||
+		 lum->lmm_magic == __swab32(LOV_MAGIC_COMP_V1))
+		magic = LOV_MAGIC_COMP_V1;
 	else
-		magic = lum->lmm_magic;
+		return true;
 
-	return lum_size < lov_user_md_size(0, magic);
+	if (magic == LOV_MAGIC_V1 || magic == LOV_MAGIC_V3)
+		return lum_size < lov_user_md_size(0, magic);
+	else
+		return lum_size < sizeof(struct lov_comp_md_v1);
 }
 
-/**
- * Compute the number of elements in the lmm_objects array of \a lum
- * with size \a lum_size.
- *
- * \param[in] lum	the struct lov_user_md to check
- * \param[in] lum_size	the number of bytes in \a lum
- *
- * \retval		number of elements in array lum->lmm_objects
- */
-static int llapi_layout_objects_in_lum(struct lov_user_md *lum, size_t lum_size)
+/* Verify if the objects count in lum is consistent with the
+ * stripe count in lum. It applies to regular file only. */
+static bool llapi_layout_lum_valid(struct lov_user_md *lum, int lum_size)
 {
-	uint32_t magic;
-	size_t base_size;
-
-	if (lum_size < lov_user_md_size(0, LOV_MAGIC_V1))
-		return 0;
-
-	if (lum->lmm_magic == __swab32(LOV_MAGIC_V1) ||
-	    lum->lmm_magic == __swab32(LOV_MAGIC_V3))
-		magic = __swab32(lum->lmm_magic);
-	else
-		magic = lum->lmm_magic;
+	struct lov_comp_md_v1 *comp_v1 = NULL;
+	int i, ent_count, obj_count;
+
+	if (lum->lmm_magic == LOV_MAGIC_COMP_V1) {
+		comp_v1 = (struct lov_comp_md_v1 *)lum;
+		ent_count = comp_v1->lcm_entry_count;
+	} else if (lum->lmm_magic == LOV_MAGIC_V1 ||
+		   lum->lmm_magic == LOV_MAGIC_V3) {
+		ent_count = 1;
+	} else {
+		return false;
+	}
 
-	base_size = lov_user_md_size(0, magic);
+	for (i = 0; i < ent_count; i++) {
+		if (comp_v1) {
+			lum = (struct lov_user_md *)((char *)comp_v1 +
+				comp_v1->lcm_entries[i].lcme_offset);
+			lum_size = comp_v1->lcm_entries[i].lcme_size;
+		}
+		obj_count = llapi_layout_objects_in_lum(lum, lum_size);
 
-	if (lum_size <= base_size)
-		return 0;
-	else
-		return (lum_size - base_size) / sizeof(lum->lmm_objects[0]);
+		if (obj_count != lum->lmm_stripe_count)
+			return false;
+	}
+	return true;
 }
 
 /**
@@ -497,10 +828,7 @@ struct llapi_layout *llapi_layout_get_by_fd(int fd, uint32_t flags)
 	struct lov_user_md *lum;
 	struct llapi_layout *layout = NULL;
 	ssize_t bytes_read;
-	int object_count;
-	int lum_stripe_count;
 	struct stat st;
-	bool need_swab;
 
 	lum_len = XATTR_SIZE_MAX;
 	lum = malloc(lum_len);
@@ -522,15 +850,7 @@ struct llapi_layout *llapi_layout_get_by_fd(int fd, uint32_t flags)
 		goto out;
 	}
 
-	object_count = llapi_layout_objects_in_lum(lum, bytes_read);
-
-	need_swab = lum->lmm_magic == __swab32(LOV_MAGIC_V1) ||
-		    lum->lmm_magic == __swab32(LOV_MAGIC_V3);
-
-	if (need_swab)
-		lum_stripe_count = __swab16(lum->lmm_stripe_count);
-	else
-		lum_stripe_count = lum->lmm_stripe_count;
+	llapi_layout_swab_lov_user_md(lum, bytes_read);
 
 	/* Directories may have a positive non-zero lum->lmm_stripe_count
 	 * yet have an empty lum->lmm_objects array. For non-directories the
@@ -539,16 +859,12 @@ struct llapi_layout *llapi_layout_get_by_fd(int fd, uint32_t flags)
 	if (fstat(fd, &st) < 0)
 		goto out;
 
-	if (!S_ISDIR(st.st_mode) && object_count != lum_stripe_count) {
+	if (!S_ISDIR(st.st_mode) && !llapi_layout_lum_valid(lum, bytes_read)) {
 		errno = EINTR;
 		goto out;
 	}
 
-	if (need_swab)
-		llapi_layout_swab_lov_user_md(lum, object_count);
-
-	layout = llapi_layout_from_lum(lum, object_count);
-
+	layout = llapi_layout_from_lum(lum, bytes_read);
 out:
 	free(lum);
 	return layout;
@@ -578,7 +894,6 @@ out:
 static struct llapi_layout *llapi_layout_expected(const char *path)
 {
 	struct llapi_layout	*path_layout = NULL;
-	struct llapi_layout	*donor_layout;
 	char			donor_path[PATH_MAX];
 	struct stat st;
 	int fd;
@@ -606,44 +921,41 @@ static struct llapi_layout *llapi_layout_expected(const char *path)
 			return NULL;
 	}
 
-	if (is_fully_specified(path_layout))
+	if (is_any_specified(path_layout)) {
+		inherit_sys_attributes(path_layout, path);
 		return path_layout;
+	}
+
+	llapi_layout_free(path_layout);
 
 	rc = stat(path, &st);
-	if (rc < 0 && errno != ENOENT) {
-		llapi_layout_free(path_layout);
+	if (rc < 0 && errno != ENOENT)
 		return NULL;
-	}
 
-	/* If path is a not a directory or doesn't exist, inherit unspecified
-	 * attributes from parent directory. */
+	/* If path is a not a directory or doesn't exist, inherit layout
+	 * from parent directory. */
 	if ((rc == 0 && !S_ISDIR(st.st_mode)) ||
 	    (rc < 0 && errno == ENOENT)) {
 		get_parent_dir(path, donor_path, sizeof(donor_path));
-		donor_layout = llapi_layout_get_by_path(donor_path, 0);
-		if (donor_layout != NULL) {
-			inherit_layout_attributes(donor_layout, path_layout);
-			llapi_layout_free(donor_layout);
-			if (is_fully_specified(path_layout))
+		path_layout = llapi_layout_get_by_path(donor_path, 0);
+		if (path_layout != NULL) {
+			if (is_any_specified(path_layout)) {
+				inherit_sys_attributes(path_layout, donor_path);
 				return path_layout;
+			}
+			llapi_layout_free(path_layout);
 		}
 	}
 
-	/* Inherit remaining unspecified attributes from the filesystem root. */
+	/* Inherit layout from the filesystem root. */
 	rc = llapi_search_mounts(path, 0, donor_path, NULL);
-	if (rc < 0) {
-		llapi_layout_free(path_layout);
+	if (rc < 0)
 		return NULL;
-	}
-	donor_layout = llapi_layout_get_by_path(donor_path, 0);
-	if (donor_layout == NULL) {
-		llapi_layout_free(path_layout);
+	path_layout = llapi_layout_get_by_path(donor_path, 0);
+	if (path_layout == NULL)
 		return NULL;
-	}
-
-	inherit_layout_attributes(donor_layout, path_layout);
-	llapi_layout_free(donor_layout);
 
+	inherit_sys_attributes(path_layout, donor_path);
 	return path_layout;
 }
 
@@ -718,18 +1030,6 @@ struct llapi_layout *llapi_layout_get_by_fid(const char *lustre_dir,
 }
 
 /**
- * Free memory allocated for \a layout.
- *
- * \param[in] layout	previously allocated by llapi_layout_alloc()
- */
-void llapi_layout_free(struct llapi_layout *layout)
-{
-	if (layout->llot_objects != NULL)
-		free(layout->llot_objects);
-	free(layout);
-}
-
-/**
  * Get the stripe count of \a layout.
  *
  * \param[in] layout	layout to get stripe count from
@@ -741,12 +1041,19 @@ void llapi_layout_free(struct llapi_layout *layout)
 int llapi_layout_stripe_count_get(const struct llapi_layout *layout,
 				  uint64_t *count)
 {
-	if (layout == NULL || count == NULL ||
-	    layout->llot_magic != LLAPI_LAYOUT_MAGIC) {
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (count == NULL) {
 		errno = EINVAL;
 		return -1;
 	}
-	*count = layout->llot_stripe_count;
+
+	*count = comp->llc_stripe_count;
+
 	return 0;
 }
 
@@ -791,13 +1098,18 @@ static bool llapi_layout_stripe_index_is_valid(int64_t stripe_index)
 int llapi_layout_stripe_count_set(struct llapi_layout *layout,
 				  uint64_t count)
 {
-	if (layout == NULL || layout->llot_magic != LLAPI_LAYOUT_MAGIC ||
-	    !llapi_layout_stripe_count_is_valid(count)) {
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (!llapi_layout_stripe_count_is_valid(count)) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	layout->llot_stripe_count = count;
+	comp->llc_stripe_count = count;
 
 	return 0;
 }
@@ -814,13 +1126,18 @@ int llapi_layout_stripe_count_set(struct llapi_layout *layout,
 int llapi_layout_stripe_size_get(const struct llapi_layout *layout,
 				 uint64_t *size)
 {
-	if (layout == NULL || size == NULL ||
-	    layout->llot_magic != LLAPI_LAYOUT_MAGIC) {
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (size == NULL) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	*size = layout->llot_stripe_size;
+	*size = comp->llc_stripe_size;
 
 	return 0;
 }
@@ -837,13 +1154,18 @@ int llapi_layout_stripe_size_get(const struct llapi_layout *layout,
 int llapi_layout_stripe_size_set(struct llapi_layout *layout,
 				 uint64_t size)
 {
-	if (layout == NULL || layout->llot_magic != LLAPI_LAYOUT_MAGIC ||
-	    !llapi_layout_stripe_size_is_valid(size)) {
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (!llapi_layout_stripe_size_is_valid(size)) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	layout->llot_stripe_size = size;
+	comp->llc_stripe_size = size;
 
 	return 0;
 }
@@ -860,13 +1182,18 @@ int llapi_layout_stripe_size_set(struct llapi_layout *layout,
 int llapi_layout_pattern_get(const struct llapi_layout *layout,
 			     uint64_t *pattern)
 {
-	if (layout == NULL || pattern == NULL ||
-	    layout->llot_magic != LLAPI_LAYOUT_MAGIC) {
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (pattern == NULL) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	*pattern = layout->llot_pattern;
+	*pattern = comp->llc_pattern;
 
 	return 0;
 }
@@ -883,10 +1210,11 @@ int llapi_layout_pattern_get(const struct llapi_layout *layout,
  */
 int llapi_layout_pattern_set(struct llapi_layout *layout, uint64_t pattern)
 {
-	if (layout == NULL || layout->llot_magic != LLAPI_LAYOUT_MAGIC) {
-		errno = EINVAL;
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
 		return -1;
-	}
 
 	if (pattern != LLAPI_LAYOUT_DEFAULT &&
 	    pattern != LLAPI_LAYOUT_RAID0) {
@@ -894,8 +1222,8 @@ int llapi_layout_pattern_set(struct llapi_layout *layout, uint64_t pattern)
 		return -1;
 	}
 
-	layout->llot_pattern = pattern |
-				(layout->llot_pattern & LLAPI_LAYOUT_SPECIFIC);
+	comp->llc_pattern = pattern |
+			    (comp->llc_pattern & LLAPI_LAYOUT_SPECIFIC);
 
 	return 0;
 }
@@ -926,19 +1254,21 @@ static inline int stripe_number_roundup(int stripe_number)
 int llapi_layout_ost_index_set(struct llapi_layout *layout, int stripe_number,
 			       uint64_t ost_index)
 {
-	if (layout == NULL || layout->llot_magic != LLAPI_LAYOUT_MAGIC) {
-		errno = EINVAL;
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
 		return -1;
-	}
+
 	if (!llapi_layout_stripe_index_is_valid(ost_index)) {
 		errno = EINVAL;
 		return -1;
 	}
 
 	if (stripe_number == 0 && ost_index == LLAPI_LAYOUT_DEFAULT) {
-		layout->llot_stripe_offset = ost_index;
-		layout->llot_pattern &= ~LLAPI_LAYOUT_SPECIFIC;
-		__llapi_layout_objects_realloc(layout, 0);
+		comp->llc_stripe_offset = ost_index;
+		comp->llc_pattern &= ~LLAPI_LAYOUT_SPECIFIC;
+		__llapi_comp_objects_realloc(comp, 0);
 	} else if (stripe_number >= 0 &&
 		   stripe_number < LOV_MAX_STRIPE_COUNT) {
 		if (ost_index >= LLAPI_LAYOUT_IDX_MAX) {
@@ -947,20 +1277,20 @@ int llapi_layout_ost_index_set(struct llapi_layout *layout, int stripe_number,
 		}
 
 		/* Preallocate a few more stripes to avoid realloc() overhead.*/
-		if (__llapi_layout_objects_realloc(layout,
+		if (__llapi_comp_objects_realloc(comp,
 				stripe_number_roundup(stripe_number)) < 0)
 			return -1;
 
-		layout->llot_objects[stripe_number].l_ost_idx = ost_index;
+		comp->llc_objects[stripe_number].l_ost_idx = ost_index;
 
 		if (stripe_number == 0)
-			layout->llot_stripe_offset = ost_index;
+			comp->llc_stripe_offset = ost_index;
 		else
-			layout->llot_pattern |= LLAPI_LAYOUT_SPECIFIC;
+			comp->llc_pattern |= LLAPI_LAYOUT_SPECIFIC;
 
-		if (layout->llot_stripe_count == LLAPI_LAYOUT_DEFAULT ||
-		    layout->llot_stripe_count <= stripe_number)
-			layout->llot_stripe_count = stripe_number + 1;
+		if (comp->llc_stripe_count == LLAPI_LAYOUT_DEFAULT ||
+		    comp->llc_stripe_count <= stripe_number)
+			comp->llc_stripe_count = stripe_number + 1;
 	} else {
 		errno = EINVAL;
 		return -1;
@@ -984,17 +1314,27 @@ int llapi_layout_ost_index_set(struct llapi_layout *layout, int stripe_number,
 int llapi_layout_ost_index_get(const struct llapi_layout *layout,
 			       uint64_t stripe_number, uint64_t *index)
 {
-	if (layout == NULL || layout->llot_magic != LLAPI_LAYOUT_MAGIC ||
-	    stripe_number >= layout->llot_stripe_count ||
-	    stripe_number >= layout->llot_objects_count || index == NULL) {
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (index == NULL) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	if (layout->llot_stripe_offset == LLAPI_LAYOUT_DEFAULT)
+	if (stripe_number >= comp->llc_stripe_count ||
+	    stripe_number >= comp->llc_objects_count) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (comp->llc_stripe_offset == LLAPI_LAYOUT_DEFAULT)
 		*index = LLAPI_LAYOUT_DEFAULT;
 	else
-		*index = layout->llot_objects[stripe_number].l_ost_idx;
+		*index = comp->llc_objects[stripe_number].l_ost_idx;
 
 	return 0;
 }
@@ -1013,13 +1353,18 @@ int llapi_layout_ost_index_get(const struct llapi_layout *layout,
 int llapi_layout_pool_name_get(const struct llapi_layout *layout, char *dest,
 			       size_t n)
 {
-	if (layout == NULL || layout->llot_magic != LLAPI_LAYOUT_MAGIC ||
-	    dest == NULL) {
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (dest == NULL) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	strncpy(dest, layout->llot_pool_name, n);
+	strncpy(dest, comp->llc_pool_name, n);
 
 	return 0;
 }
@@ -1036,10 +1381,14 @@ int llapi_layout_pool_name_get(const struct llapi_layout *layout, char *dest,
 int llapi_layout_pool_name_set(struct llapi_layout *layout,
 			       const char *pool_name)
 {
+	struct llapi_layout_comp *comp;
 	char *ptr;
 
-	if (layout == NULL || layout->llot_magic != LLAPI_LAYOUT_MAGIC ||
-	    pool_name == NULL) {
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (pool_name == NULL) {
 		errno = EINVAL;
 		return -1;
 	}
@@ -1054,8 +1403,7 @@ int llapi_layout_pool_name_set(struct llapi_layout *layout,
 		return -1;
 	}
 
-	strncpy(layout->llot_pool_name, pool_name,
-		sizeof(layout->llot_pool_name));
+	strncpy(comp->llc_pool_name, pool_name, sizeof(comp->llc_pool_name));
 
 	return 0;
 }
@@ -1109,7 +1457,9 @@ int llapi_layout_file_open(const char *path, int open_flags, mode_t mode,
 		return -1;
 	}
 
-	if (lum->lmm_magic == LOV_USER_MAGIC_SPECIFIC)
+	if (lum->lmm_magic == LOV_USER_MAGIC_COMP_V1)
+		lum_size = ((struct lov_comp_md_v1 *)lum)->lcm_size;
+	else if (lum->lmm_magic == LOV_USER_MAGIC_SPECIFIC)
 		lum_size = lov_user_md_size(lum->lmm_stripe_count,
 					    lum->lmm_magic);
 	else
@@ -1149,3 +1499,456 @@ int llapi_layout_file_create(const char *path, int open_flags, int mode,
 	return llapi_layout_file_open(path, open_flags|O_CREAT|O_EXCL, mode,
 				      layout);
 }
+
+/**
+ * Fetch the start and end offset of the current layout component.
+ *
+ * \param[in] layout	the layout component
+ * \param[out] start	extent start, inclusive
+ * \param[out] end	extent end, exclusive
+ *
+ * \retval	0 on success
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_extent_get(const struct llapi_layout *layout,
+				 uint64_t *start, uint64_t *end)
+{
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (start == NULL || end == NULL) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	*start = comp->llc_extent.e_start;
+	*end = comp->llc_extent.e_end;
+
+	return 0;
+}
+
+/**
+ * Set the layout extent of a layout.
+ *
+ * \param[in] layout	the layout to be set
+ * \param[in] start	extent start, inclusive
+ * \param[in] end	extent end, exclusive
+ *
+ * \retval	0 on success
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_extent_set(struct llapi_layout *layout,
+				 uint64_t start, uint64_t end)
+{
+	struct llapi_layout_comp *prev, *next, *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (start >= end) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	/*
+	 * We need to make sure the extent to be set is valid: the new
+	 * extent must be adjacent with the prev & next component.
+	 */
+	if (comp->llc_list.prev != &layout->llot_comp_list) {
+		prev = list_entry(comp->llc_list.prev, typeof(*prev),
+				  llc_list);
+		if (start != prev->llc_extent.e_end) {
+			errno = EINVAL;
+			return -1;
+		}
+	}
+
+	if (comp->llc_list.next != &layout->llot_comp_list) {
+		next = list_entry(comp->llc_list.next, typeof(*next),
+				  llc_list);
+		if (end != next->llc_extent.e_start) {
+			errno = EINVAL;
+			return -1;
+		}
+	}
+
+	comp->llc_extent.e_start = start;
+	comp->llc_extent.e_end = end;
+	layout->llot_is_composite = true;
+
+	return 0;
+}
+
+/**
+ * Gets the attribute flags of the current component.
+ *
+ * \param[in] layout	the layout component
+ * \param[out] flags	stored the returned component flags
+ *
+ * \retval	0 on success
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_flags_get(const struct llapi_layout *layout,
+				uint32_t *flags)
+{
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (flags == NULL) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	*flags = comp->llc_flags;
+
+	return 0;
+}
+
+/**
+ * Sets the specified flags of the current component leaving other flags as-is.
+ *
+ * \param[in] layout	the layout component
+ * \param[in] flags	component flags to be set
+ *
+ * \retval	0 on success
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_flags_set(struct llapi_layout *layout, uint32_t flags)
+{
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	comp->llc_flags |= flags;
+
+	return 0;
+}
+
+/**
+ * Clears the flags specified in the flags leaving other flags as-is.
+ *
+ * \param[in] layout	the layout component
+ * \param[in] flags	component flags to be cleared
+ *
+ * \retval	0 on success
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_flags_clear(struct llapi_layout *layout,
+				  uint32_t flags)
+{
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	comp->llc_flags &= ~flags;
+
+	return 0;
+}
+
+/**
+ * Fetches the file-unique component ID of the current layout component.
+ *
+ * \param[in] layout	the layout component
+ * \param[out] id	stored the returned component ID
+ *
+ * \retval	0 on success
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_id_get(const struct llapi_layout *layout, uint32_t *id)
+{
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (id == NULL) {
+		errno = EINVAL;
+		return -1;
+	}
+	*id = comp->llc_id;
+
+	return 0;
+}
+
+/**
+ * Adds a component to \a layout, the new component will be added to
+ * the tail of components list and it'll inherit attributes of existing
+ * ones. The \a layout will change it's current component pointer to
+ * the newly added component, and it'll be turned into a composite
+ * layout if it was not before the adding.
+ *
+ * \param[in] layout	existing composite or plain layout
+ *
+ * \retval	0 on success
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_add(struct llapi_layout *layout)
+{
+	struct llapi_layout_comp *last, *comp, *new;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	new = __llapi_comp_alloc(0);
+	if (new == NULL)
+		return -1;
+
+	last = list_entry(layout->llot_comp_list.prev, typeof(*last),
+			  llc_list);
+
+	/* Inherit some attributes from existing component */
+	new->llc_pattern = comp->llc_pattern;
+	new->llc_stripe_size = comp->llc_stripe_size;
+	new->llc_stripe_count = comp->llc_stripe_count;
+	if (new->llc_extent.e_end <= last->llc_extent.e_end) {
+		__llapi_comp_free(new);
+		errno = EINVAL;
+		return -1;
+	}
+	new->llc_extent.e_start = last->llc_extent.e_end;
+
+	list_add_tail(&new->llc_list, &layout->llot_comp_list);
+	layout->llot_cur_comp = new;
+	layout->llot_is_composite = true;
+
+	return 0;
+}
+
+/**
+ * Deletes current component from the composite layout. The component
+ * to be deleted must be the tail of components list, and it can't be
+ * the last component in the layout.
+ *
+ * \param[in] layout	composite layout
+ *
+ * \retval	0 on success
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_del(struct llapi_layout *layout)
+{
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (!layout->llot_is_composite) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	/* It must be the tail of the list */
+	if (comp->llc_list.next != &layout->llot_comp_list) {
+		errno = EINVAL;
+		return -1;
+	}
+	/* It can't be the last one on the list */
+	if (comp->llc_list.prev == &layout->llot_comp_list) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	list_del_init(&comp->llc_list);
+	__llapi_comp_free(comp);
+	layout->llot_cur_comp =
+		list_entry(comp->llc_list.prev, typeof(*comp),
+			   llc_list);
+
+	return 0;
+}
+
+/**
+ * Move the current component pointer to the component with
+ * specified component ID.
+ *
+ * \param[in] layout	composite layout
+ * \param[in] id	component ID
+ *
+ * \retval	=0 : moved successfully
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_move_at(struct llapi_layout *layout, uint32_t id)
+{
+	struct llapi_layout_comp *comp;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (!layout->llot_is_composite) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (id == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	list_for_each_entry(comp, &layout->llot_comp_list, llc_list) {
+		if (comp->llc_id == id) {
+			layout->llot_cur_comp = comp;
+			return 0;
+		}
+	}
+	errno = ENOENT;
+	return -1;
+}
+
+/**
+ * Move the current component pointer to a specified position.
+ *
+ * \param[in] layout	composite layout
+ * \param[in] pos	the position to be moved, it can be:
+ *			LLAPI_LAYOUT_COMP_POS_FIRST: move to head
+ *			LLAPI_LAYOUT_COMP_POS_LAST: move to tail
+ *			LLAPI_LAYOUT_COMP_POS_NEXT: move to next
+ *
+ * \retval	=0 : moved successfully
+ * \retval	=1 : already at the tail when move to the next
+ * \retval	<0 if error occurs
+ */
+int llapi_layout_comp_move(struct llapi_layout *layout, uint32_t pos)
+{
+	struct llapi_layout_comp *comp, *head, *tail;
+
+	comp = __llapi_layout_cur_comp(layout);
+	if (comp == NULL)
+		return -1;
+
+	if (!layout->llot_is_composite) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	head = list_entry(layout->llot_comp_list.next, typeof(*head),
+			  llc_list);
+	tail = list_entry(layout->llot_comp_list.prev, typeof(*tail),
+			  llc_list);
+
+	if (pos == LLAPI_LAYOUT_COMP_POS_NEXT) {
+		if (comp == tail)
+			return 1;
+		layout->llot_cur_comp = list_entry(comp->llc_list.next,
+						   typeof(*comp), llc_list);
+	} else if (pos == LLAPI_LAYOUT_COMP_POS_FIRST) {
+		layout->llot_cur_comp = head;
+	} else if (pos == LLAPI_LAYOUT_COMP_POS_LAST) {
+		layout->llot_cur_comp = tail;
+	} else {
+		errno = EINVAL;
+		return -1;
+	}
+
+	return 0;
+}
+
+/**
+ * Add layout component(s) to an existing file.
+ *
+ * \param[in] path	The path name of the file
+ * \param[in] layout	The layout component(s) to be added
+ */
+int llapi_layout_file_comp_add(const char *path,
+			       const struct llapi_layout *layout)
+{
+	int rc, fd, lum_size, tmp_errno = 0;
+	struct lov_user_md *lum;
+
+	if (path == NULL || layout == NULL ||
+	    layout->llot_magic != LLAPI_LAYOUT_MAGIC) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	lum = llapi_layout_to_lum(layout);
+	if (lum == NULL)
+		return -1;
+
+	if (lum->lmm_magic != LOV_USER_MAGIC_COMP_V1) {
+		free(lum);
+		errno = EINVAL;
+		return -1;
+	}
+	lum_size = ((struct lov_comp_md_v1 *)lum)->lcm_size;
+
+	fd = open(path, O_RDWR);
+	if (fd < 0) {
+		tmp_errno = errno;
+		rc = -1;
+		goto out;
+	}
+
+	rc = fsetxattr(fd, XATTR_LUSTRE_LOV".add", lum, lum_size, 0);
+	if (rc < 0) {
+		tmp_errno = errno;
+		close(fd);
+		rc = -1;
+		goto out;
+	}
+	close(fd);
+out:
+	free(lum);
+	errno = tmp_errno;
+	return rc;
+}
+
+/**
+ * Delete component(s) by the specified component id (accepting lcme_id
+ * wildcards also) from an existing file.
+ *
+ * \param[in] path	path name of the file
+ * \param[in] id	unique component ID or an lcme_id
+ *			(LCME_ID_NONE | LCME_FL_* )
+ */
+int llapi_layout_file_comp_del(const char *path, uint32_t id)
+{
+	int rc, fd;
+
+	if (path == NULL || id == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	fd = open(path, O_RDWR);
+	if (fd < 0)
+		return -1;
+
+	rc = fsetxattr(fd, XATTR_LUSTRE_LOV".del", &id, sizeof(id), 0);
+	if (rc < 0) {
+		int tmp_errno = errno;
+		close(fd);
+		errno = tmp_errno;
+		return -1;
+	}
+	close(fd);
+	return 0;
+}
+
+/**
+ * Change flags or other parameters of the component(s) by component ID of an
+ * existing file. The component to be modified is specified by the
+ * comp->lcme_id value, which must be an unique component ID. The new
+ * attributes are passed in by @comp and @valid is used to specify which
+ * attributes in the component are going to be changed.
+ */
+int llapi_layout_file_comp_set(const char *path,
+			       const struct llapi_layout *comp,
+			       uint32_t valid)
+{
+	errno = EOPNOTSUPP;
+	return -1;
+}
diff --git a/lustre/utils/lustreapi_internal.h b/lustre/utils/lustreapi_internal.h
index 5e05c9c..e1deeb9 100644
--- a/lustre/utils/lustreapi_internal.h
+++ b/lustre/utils/lustreapi_internal.h
@@ -53,6 +53,9 @@
 int get_root_path(int want, char *fsname, int *outfd, char *path, int index);
 int root_ioctl(const char *mdtname, int opc, void *data, int *mdtidxp,
 	       int want_error);
+int sattr_cache_get_defaults(const char *const fsname,
+			     const char *const pathname, unsigned int *scount,
+			     unsigned int *ssize, unsigned int *soffset);
 
 /**
  * Often when determining the parameter path in sysfs/procfs we