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LU-9412 lfs: A invalid memory write in llapi_layout_to_lum
[fs/lustre-release.git] / lustre / utils / liblustreapi_layout.c
index eff35e2..557765d 100644 (file)
@@ -23,6 +23,8 @@
  * Lustre files while hiding details of the internal data structures
  * from the user.
  *
+ * Copyright (c) 2016, Intel Corporation.
+ *
  * Author: Ned Bass <bass6@llnl.gov>
  */
 
 #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;
-       /** Indicates if llot_objects array has been initialized. */
-       bool            llot_objects_are_valid;
-       /* Add 1 so user always gets back a null terminated string. */
-       char            llot_pool_name[LOV_MAXPOOLNAME + 1];
-       struct          lov_user_ost_data_v1 llot_objects[0];
+       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
@@ -66,178 +115,523 @@ 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;
+       }
+
+       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 (j = 0; j < obj_count; j++)
+                       __swab32s(&lod[j].l_ost_idx);
+       }
+}
 
-       if (lum->lmm_magic != LOV_MAGIC_V1)
-               lod = lumv3->lmm_objects;
-       else
-               lod = lum->lmm_objects;
+/**
+ * (Re-)allocate llc_objects[] to \a num_stripes stripes.
+ *
+ * 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
+ *
+ * \retval     0 if the objects are re-allocated successfully
+ * \retval     -1 on error with errno set
+ */
+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;
+
+       if (new_stripes > LOV_MAX_STRIPE_COUNT) {
+               errno = EINVAL;
+               return -1;
+       }
+
+       if (new_stripes == comp->llc_objects_count)
+               return 0;
+
+       if (new_stripes != 0 && new_stripes <= comp->llc_objects_count)
+               return 0;
+
+       new_objects = realloc(comp->llc_objects,
+                             sizeof(*new_objects) * new_stripes);
+       if (new_objects == NULL && new_stripes != 0) {
+               errno = ENOMEM;
+               return -1;
+       }
+
+       for (i = comp->llc_objects_count; i < new_stripes; i++)
+               new_objects[i].l_ost_idx = LLAPI_LAYOUT_IDX_MAX;
+
+       comp->llc_objects = new_objects;
+       comp->llc_objects_count = new_stripes;
 
-       for (i = 0; i < object_count; i++)
-               __swab32s(&lod[i].l_ost_idx);
+       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 = NULL;
-       size_t size = sizeof(*layout) +
-               (num_stripes * sizeof(layout->llot_objects[0]));
+       struct llapi_layout_comp *comp;
 
-       if (num_stripes > LOV_MAX_STRIPE_COUNT)
+       if (num_stripes > LOV_MAX_STRIPE_COUNT) {
                errno = EINVAL;
-       else
-               layout = calloc(1, size);
+               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;
+       }
+
+       /* 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;
 }
 
 /**
- * Copy the data from a lov_user_md to a newly allocated llapi_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;
+
+       comp = __llapi_comp_alloc(0);
+       if (comp == NULL) {
+               free(layout);
+               return NULL;
+       }
+
+       list_add_tail(&comp->llc_list, &layout->llot_comp_list);
+       layout->llot_cur_comp = comp;
+
+       return 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;
-
-       objects_sz = object_count * sizeof(lum->lmm_objects[0]);
+       struct llapi_layout_comp *comp;
+       int i, ent_count = 0, obj_count;
 
-       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 (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]));
+               }
 
-       /* Don't copy lmm_stripe_offset: it is always zero
-        * when reading attributes. */
+               if (obj_count != 0)
+                       comp->llc_stripe_offset =
+                               comp->llc_objects[0].l_ost_idx;
 
-       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);
+               list_add_tail(&comp->llc_list, &layout->llot_comp_list);
+               layout->llot_cur_comp = comp;
        }
-       if (object_count > 0)
-               layout->llot_objects_are_valid = true;
 
        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
- * \retval     NULL if memory allocation fails
+ * \retval     NULL if memory allocation fails or the layout is invalid
  */
 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;
-
-       if (strlen(layout->llot_pool_name) != 0)
-               magic = LOV_USER_MAGIC_V3;
-
-       /* The lum->lmm_objects array won't be
-        * sent to the kernel when we write the lum, so
-        * we don't allocate storage for it.
-        */
-       lum_size = lov_user_md_size(0, magic);
-       lum = malloc(lum_size);
-       if (lum == NULL)
+       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;
+       }
 
-       lum->lmm_magic = magic;
+       /* Allocate header of lov_comp_md_v1 if necessary */
+       if (layout->llot_is_composite) {
+               int comp_cnt = 0;
 
-       if (layout->llot_pattern == LLAPI_LAYOUT_DEFAULT)
-               lum->lmm_pattern = 0;
-       else if (layout->llot_pattern == LLAPI_LAYOUT_RAID0)
-               lum->lmm_pattern = 1;
-       else
-               lum->lmm_pattern = layout->llot_pattern;
+               list_for_each_entry(comp, &layout->llot_comp_list, llc_list)
+                       comp_cnt++;
 
-       if (layout->llot_stripe_size == LLAPI_LAYOUT_DEFAULT)
-               lum->lmm_stripe_size = 0;
-       else
-               lum->lmm_stripe_size = layout->llot_stripe_size;
+               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;
+       }
 
-       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 = -1;
-       else
-               lum->lmm_stripe_count = layout->llot_stripe_count;
+       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 (layout->llot_stripe_offset == LLAPI_LAYOUT_DEFAULT)
-               lum->lmm_stripe_offset = -1;
-       else
-               lum->lmm_stripe_offset = layout->llot_stripe_offset;
+               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;
+                       comp_v1 = (struct lov_comp_md_v1 *)lum;
+                       blob = (struct lov_user_md *)((char *)lum + lum_size);
+                       lum_size += blob_size;
+               }
 
-       if (lum->lmm_magic != LOV_USER_MAGIC_V1) {
-               struct lov_user_md_v3 *lumv3 = (struct lov_user_md_v3 *)lum;
+               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 (comp->llc_stripe_size == LLAPI_LAYOUT_DEFAULT)
+                       blob->lmm_stripe_size = 0;
+               else
+                       blob->lmm_stripe_size = comp->llc_stripe_size;
+
+               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 (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;
+               }
 
-               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 (layout->llot_is_composite) {
+                       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 {
+                       break;
+               }
        }
 
        return lum;
+error:
+       free(lum);
+       return NULL;
 }
 
 /**
@@ -254,71 +648,98 @@ static void get_parent_dir(const char *path, char *buf, size_t size)
        strncpy(buf, path, size);
        p = strrchr(buf, '/');
 
-       if (p != NULL)
+       if (p != NULL) {
                *p = '\0';
-       else if (size >= 2)
+       } else if (size >= 2) {
                strncpy(buf, ".", 2);
+               buf[size - 1] = '\0';
+       }
 }
 
 /**
- * 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;
+       struct llapi_layout_comp *comp;
+       unsigned int ssize, scount, soffset;
+       int rc;
 
-       if (dest->llot_stripe_count == LLAPI_LAYOUT_DEFAULT)
-               dest->llot_stripe_count = src->llot_stripe_count;
+       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_objects_are_valid = false;
-       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);
 }
 
 /**
@@ -335,47 +756,61 @@ 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;
-
-       base_size = lov_user_md_size(0, 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;
+       }
 
-       if (lum_size <= base_size)
-               return 0;
-       else
-               return (lum_size - base_size) / sizeof(lum->lmm_objects[0]);
+       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 (comp_v1) {
+                       if (!(comp_v1->lcm_entries[i].lcme_flags &
+                                LCME_FL_INIT) && obj_count != 0)
+                               return false;
+               } else if (obj_count != lum->lmm_stripe_count) {
+                       return false;
+               }
+       }
+       return true;
 }
 
 /**
@@ -401,7 +836,6 @@ 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;
        struct stat st;
 
        lum_len = XATTR_SIZE_MAX;
@@ -424,7 +858,7 @@ 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);
+       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
@@ -433,17 +867,12 @@ 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->lmm_stripe_count) {
+       if (!S_ISDIR(st.st_mode) && !llapi_layout_lum_valid(lum, bytes_read)) {
                errno = EINTR;
                goto out;
        }
 
-       if (lum->lmm_magic == __swab32(LOV_MAGIC_V1) ||
-           lum->lmm_magic == __swab32(LOV_MAGIC_V3))
-               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;
@@ -473,7 +902,6 @@ 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;
@@ -501,44 +929,41 @@ 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;
 }
 
@@ -612,12 +1037,6 @@ struct llapi_layout *llapi_layout_get_by_fid(const char *lustre_dir,
        return layout;
 }
 
-/** * Free memory allocated for \a layout. */
-void llapi_layout_free(struct llapi_layout *layout)
-{
-       free(layout);
-}
-
 /**
  * Get the stripe count of \a layout.
  *
@@ -630,12 +1049,19 @@ 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;
 }
 
@@ -680,13 +1106,18 @@ 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;
 }
@@ -703,13 +1134,18 @@ 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;
 }
@@ -726,13 +1162,18 @@ 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;
 }
@@ -749,13 +1190,18 @@ 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;
 }
@@ -772,26 +1218,38 @@ 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 ||
+       if (pattern != LLAPI_LAYOUT_DEFAULT &&
            pattern != LLAPI_LAYOUT_RAID0) {
                errno = EOPNOTSUPP;
                return -1;
        }
 
-       layout->llot_pattern = pattern;
+       comp->llc_pattern = pattern |
+                           (comp->llc_pattern & LLAPI_LAYOUT_SPECIFIC);
 
        return 0;
 }
 
+static inline int stripe_number_roundup(int stripe_number)
+{
+       unsigned int round_up = (stripe_number + 8) & ~7;
+       return round_up > LOV_MAX_STRIPE_COUNT ?
+               LOV_MAX_STRIPE_COUNT : round_up;
+}
+
 /**
  * Set the OST index of stripe number \a stripe_number to \a ost_index.
  *
- * The index may only be set for stripe number 0 for now.
+ * If only the starting stripe's OST index is specified, then this can use
+ * the normal LOV_MAGIC_{V1,V3} layout type.  If multiple OST indices are
+ * given, then allocate an array to hold the list of indices and ensure that
+ * the LOV_USER_MAGIC_SPECIFIC layout is used when creating the file.
  *
  * \param[in] layout           layout to set OST index in
  * \param[in] stripe_number    stripe number to set index for
@@ -799,24 +1257,53 @@ int llapi_layout_pattern_set(struct llapi_layout *layout, uint64_t pattern)
  *
  * \retval     0 on success
  * \retval     -1 if arguments are invalid or an unsupported stripe number
- *             was specified
+ *             was specified, error returned in errno
  */
 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 ||
-           !llapi_layout_stripe_index_is_valid(ost_index)) {
+       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) {
-               errno = EOPNOTSUPP;
+       if (stripe_number == 0 && ost_index == LLAPI_LAYOUT_DEFAULT) {
+               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) {
+                       errno = EINVAL;
+                       return -1;
+               }
+
+               /* Preallocate a few more stripes to avoid realloc() overhead.*/
+               if (__llapi_comp_objects_realloc(comp,
+                               stripe_number_roundup(stripe_number)) < 0)
+                       return -1;
+
+               comp->llc_objects[stripe_number].l_ost_idx = ost_index;
+
+               if (stripe_number == 0)
+                       comp->llc_stripe_offset = ost_index;
+               else
+                       comp->llc_pattern |= LLAPI_LAYOUT_SPECIFIC;
+
+               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;
        }
 
-       layout->llot_stripe_offset = ost_index;
-
        return 0;
 }
 
@@ -835,17 +1322,27 @@ 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 ||
-           index == NULL  || layout->llot_objects_are_valid == 0) {
+       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_objects[stripe_number].l_ost_idx == -1)
+       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;
 }
@@ -864,13 +1361,18 @@ 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;
 }
@@ -887,10 +1389,14 @@ 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;
        }
@@ -905,8 +1411,7 @@ 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;
 }
@@ -960,7 +1465,13 @@ int llapi_layout_file_open(const char *path, int open_flags, mode_t mode,
                return -1;
        }
 
-       lum_size = lov_user_md_size(0, lum->lmm_magic);
+       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
+               lum_size = lov_user_md_size(0, lum->lmm_magic);
 
        rc = fsetxattr(fd, XATTR_LUSTRE_LOV, lum, lum_size, 0);
        if (rc < 0) {
@@ -996,3 +1507,503 @@ 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_stripe_size = comp->llc_stripe_size;
+       new->llc_stripe_count = comp->llc_stripe_count;
+       if (comp->llc_pool_name[0] != '\0')
+               strncpy(new->llc_pool_name, comp->llc_pool_name,
+                       sizeof(comp->llc_pool_name));
+       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 only 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 (for PFL, can be relaxed
+        * once we get mirrored components) */
+       if (comp->llc_list.next != &layout->llot_comp_list) {
+               errno = EINVAL;
+               return -1;
+       }
+       /* It can't be the only one on the list */
+       if (comp->llc_list.prev == &layout->llot_comp_list) {
+               errno = EINVAL;
+               return -1;
+       }
+
+       layout->llot_cur_comp =
+               list_entry(comp->llc_list.prev, typeof(*comp), llc_list);
+       list_del_init(&comp->llc_list);
+       __llapi_comp_free(comp);
+
+       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_use_id(struct llapi_layout *layout, uint32_t comp_id)
+{
+       struct llapi_layout_comp *comp;
+
+       comp = __llapi_layout_cur_comp(layout);
+       if (comp == NULL)
+               return -1; /* use previously set errno */
+
+       if (!layout->llot_is_composite) {
+               errno = EINVAL;
+               return -1;
+       }
+
+       if (comp_id == LCME_ID_INVAL) {
+               errno = EINVAL;
+               return -1;
+       }
+
+       list_for_each_entry(comp, &layout->llot_comp_list, llc_list) {
+               if (comp->llc_id == comp_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_USE_FIRST: use first component
+ *                     LLAPI_LAYOUT_COMP_USE_LAST: use last component
+ *                     LLAPI_LAYOUT_COMP_USE_NEXT: use component after current
+ *                     LLAPI_LAYOUT_COMP_USE_PREV: use component before current
+ *
+ * \retval     =0 : moved successfully
+ * \retval     =1 : at last component with NEXT, at first component with PREV
+ * \retval     <0 if error occurs
+ */
+int llapi_layout_comp_use(struct llapi_layout *layout,
+                         enum llapi_layout_comp_use 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);
+       switch (pos) {
+       case LLAPI_LAYOUT_COMP_USE_FIRST:
+               layout->llot_cur_comp = head;
+               break;
+       case LLAPI_LAYOUT_COMP_USE_NEXT:
+               if (comp == tail) {
+                       errno = ENOENT;
+                       return 1;
+               }
+               layout->llot_cur_comp = list_entry(comp->llc_list.next,
+                                                  typeof(*comp), llc_list);
+               break;
+       case LLAPI_LAYOUT_COMP_USE_LAST:
+               layout->llot_cur_comp = tail;
+               break;
+       case LLAPI_LAYOUT_COMP_USE_PREV:
+               if (comp == head) {
+                       errno = ENOENT;
+                       return 1;
+               }
+               layout->llot_cur_comp = list_entry(comp->llc_list.prev,
+                                                  typeof(*comp), llc_list);
+               break;
+       default:
+               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 or component flags
+ * from an existing file.
+ *
+ * \param[in] path     path name of the file
+ * \param[in] id       unique component ID
+ * \param[in] flags    flags: LCME_FL_* or;
+ *                     negative flags: (LCME_FL_NEG|LCME_FL_*)
+ */
+int llapi_layout_file_comp_del(const char *path, uint32_t id, uint32_t flags)
+{
+       int rc, fd, lum_size;
+       struct llapi_layout *layout;
+       struct llapi_layout_comp *comp;
+       struct lov_user_md *lum;
+
+       if (path == NULL || id > LCME_ID_MAX || (flags & ~LCME_KNOWN_FLAGS)) {
+               errno = EINVAL;
+               return -1;
+       }
+
+       /* Can only specify ID or flags, not both. */
+       if (id != 0 && flags != 0) {
+               errno = EINVAL;
+               return -1;
+       }
+
+       layout = llapi_layout_alloc();
+       if (layout == NULL)
+               return -1;
+
+       llapi_layout_comp_extent_set(layout, 0, LUSTRE_EOF);
+       comp = __llapi_layout_cur_comp(layout);
+       comp->llc_id = id;
+       comp->llc_flags = flags;
+
+       lum = llapi_layout_to_lum(layout);
+       if (lum == NULL) {
+               llapi_layout_free(layout);
+               return -1;
+       }
+       lum_size = ((struct lov_comp_md_v1 *)lum)->lcm_size;
+
+       fd = open(path, O_RDWR);
+       if (fd < 0) {
+               rc = -1;
+               goto out;
+       }
+
+       rc = fsetxattr(fd, XATTR_LUSTRE_LOV".del", lum, lum_size, 0);
+       if (rc < 0) {
+               int tmp_errno = errno;
+               close(fd);
+               errno = tmp_errno;
+               rc = -1;
+               goto out;
+       }
+       close(fd);
+out:
+       free(lum);
+       llapi_layout_free(layout);
+       return rc;
+}
+
+/**
+ * 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;
+}