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-rw-r--r--fs/btrfs/backref.c776
1 files changed, 776 insertions, 0 deletions
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
new file mode 100644
index 000000000000..2351df0de450
--- /dev/null
+++ b/fs/btrfs/backref.c
@@ -0,0 +1,776 @@
+/*
+ * Copyright (C) 2011 STRATO. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include "ctree.h"
+#include "disk-io.h"
+#include "backref.h"
+
+struct __data_ref {
+ struct list_head list;
+ u64 inum;
+ u64 root;
+ u64 extent_data_item_offset;
+};
+
+struct __shared_ref {
+ struct list_head list;
+ u64 disk_byte;
+};
+
+static int __inode_info(u64 inum, u64 ioff, u8 key_type,
+ struct btrfs_root *fs_root, struct btrfs_path *path,
+ struct btrfs_key *found_key)
+{
+ int ret;
+ struct btrfs_key key;
+ struct extent_buffer *eb;
+
+ key.type = key_type;
+ key.objectid = inum;
+ key.offset = ioff;
+
+ ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
+ if (ret < 0)
+ return ret;
+
+ eb = path->nodes[0];
+ if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
+ ret = btrfs_next_leaf(fs_root, path);
+ if (ret)
+ return ret;
+ eb = path->nodes[0];
+ }
+
+ btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
+ if (found_key->type != key.type || found_key->objectid != key.objectid)
+ return 1;
+
+ return 0;
+}
+
+/*
+ * this makes the path point to (inum INODE_ITEM ioff)
+ */
+int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
+ struct btrfs_path *path)
+{
+ struct btrfs_key key;
+ return __inode_info(inum, ioff, BTRFS_INODE_ITEM_KEY, fs_root, path,
+ &key);
+}
+
+static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
+ struct btrfs_path *path,
+ struct btrfs_key *found_key)
+{
+ return __inode_info(inum, ioff, BTRFS_INODE_REF_KEY, fs_root, path,
+ found_key);
+}
+
+/*
+ * this iterates to turn a btrfs_inode_ref into a full filesystem path. elements
+ * of the path are separated by '/' and the path is guaranteed to be
+ * 0-terminated. the path is only given within the current file system.
+ * Therefore, it never starts with a '/'. the caller is responsible to provide
+ * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
+ * the start point of the resulting string is returned. this pointer is within
+ * dest, normally.
+ * in case the path buffer would overflow, the pointer is decremented further
+ * as if output was written to the buffer, though no more output is actually
+ * generated. that way, the caller can determine how much space would be
+ * required for the path to fit into the buffer. in that case, the returned
+ * value will be smaller than dest. callers must check this!
+ */
+static char *iref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
+ struct btrfs_inode_ref *iref,
+ struct extent_buffer *eb_in, u64 parent,
+ char *dest, u32 size)
+{
+ u32 len;
+ int slot;
+ u64 next_inum;
+ int ret;
+ s64 bytes_left = size - 1;
+ struct extent_buffer *eb = eb_in;
+ struct btrfs_key found_key;
+
+ if (bytes_left >= 0)
+ dest[bytes_left] = '\0';
+
+ while (1) {
+ len = btrfs_inode_ref_name_len(eb, iref);
+ bytes_left -= len;
+ if (bytes_left >= 0)
+ read_extent_buffer(eb, dest + bytes_left,
+ (unsigned long)(iref + 1), len);
+ if (eb != eb_in)
+ free_extent_buffer(eb);
+ ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
+ if (ret)
+ break;
+ next_inum = found_key.offset;
+
+ /* regular exit ahead */
+ if (parent == next_inum)
+ break;
+
+ slot = path->slots[0];
+ eb = path->nodes[0];
+ /* make sure we can use eb after releasing the path */
+ if (eb != eb_in)
+ atomic_inc(&eb->refs);
+ btrfs_release_path(path);
+
+ iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
+ parent = next_inum;
+ --bytes_left;
+ if (bytes_left >= 0)
+ dest[bytes_left] = '/';
+ }
+
+ btrfs_release_path(path);
+
+ if (ret)
+ return ERR_PTR(ret);
+
+ return dest + bytes_left;
+}
+
+/*
+ * this makes the path point to (logical EXTENT_ITEM *)
+ * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
+ * tree blocks and <0 on error.
+ */
+int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
+ struct btrfs_path *path, struct btrfs_key *found_key)
+{
+ int ret;
+ u64 flags;
+ u32 item_size;
+ struct extent_buffer *eb;
+ struct btrfs_extent_item *ei;
+ struct btrfs_key key;
+
+ key.type = BTRFS_EXTENT_ITEM_KEY;
+ key.objectid = logical;
+ key.offset = (u64)-1;
+
+ ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
+ if (ret < 0)
+ return ret;
+ ret = btrfs_previous_item(fs_info->extent_root, path,
+ 0, BTRFS_EXTENT_ITEM_KEY);
+ if (ret < 0)
+ return ret;
+
+ btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
+ if (found_key->type != BTRFS_EXTENT_ITEM_KEY ||
+ found_key->objectid > logical ||
+ found_key->objectid + found_key->offset <= logical)
+ return -ENOENT;
+
+ eb = path->nodes[0];
+ item_size = btrfs_item_size_nr(eb, path->slots[0]);
+ BUG_ON(item_size < sizeof(*ei));
+
+ ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
+ flags = btrfs_extent_flags(eb, ei);
+
+ if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
+ return BTRFS_EXTENT_FLAG_TREE_BLOCK;
+ if (flags & BTRFS_EXTENT_FLAG_DATA)
+ return BTRFS_EXTENT_FLAG_DATA;
+
+ return -EIO;
+}
+
+/*
+ * helper function to iterate extent inline refs. ptr must point to a 0 value
+ * for the first call and may be modified. it is used to track state.
+ * if more refs exist, 0 is returned and the next call to
+ * __get_extent_inline_ref must pass the modified ptr parameter to get the
+ * next ref. after the last ref was processed, 1 is returned.
+ * returns <0 on error
+ */
+static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
+ struct btrfs_extent_item *ei, u32 item_size,
+ struct btrfs_extent_inline_ref **out_eiref,
+ int *out_type)
+{
+ unsigned long end;
+ u64 flags;
+ struct btrfs_tree_block_info *info;
+
+ if (!*ptr) {
+ /* first call */
+ flags = btrfs_extent_flags(eb, ei);
+ if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
+ info = (struct btrfs_tree_block_info *)(ei + 1);
+ *out_eiref =
+ (struct btrfs_extent_inline_ref *)(info + 1);
+ } else {
+ *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
+ }
+ *ptr = (unsigned long)*out_eiref;
+ if ((void *)*ptr >= (void *)ei + item_size)
+ return -ENOENT;
+ }
+
+ end = (unsigned long)ei + item_size;
+ *out_eiref = (struct btrfs_extent_inline_ref *)*ptr;
+ *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
+
+ *ptr += btrfs_extent_inline_ref_size(*out_type);
+ WARN_ON(*ptr > end);
+ if (*ptr == end)
+ return 1; /* last */
+
+ return 0;
+}
+
+/*
+ * reads the tree block backref for an extent. tree level and root are returned
+ * through out_level and out_root. ptr must point to a 0 value for the first
+ * call and may be modified (see __get_extent_inline_ref comment).
+ * returns 0 if data was provided, 1 if there was no more data to provide or
+ * <0 on error.
+ */
+int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
+ struct btrfs_extent_item *ei, u32 item_size,
+ u64 *out_root, u8 *out_level)
+{
+ int ret;
+ int type;
+ struct btrfs_tree_block_info *info;
+ struct btrfs_extent_inline_ref *eiref;
+
+ if (*ptr == (unsigned long)-1)
+ return 1;
+
+ while (1) {
+ ret = __get_extent_inline_ref(ptr, eb, ei, item_size,
+ &eiref, &type);
+ if (ret < 0)
+ return ret;
+
+ if (type == BTRFS_TREE_BLOCK_REF_KEY ||
+ type == BTRFS_SHARED_BLOCK_REF_KEY)
+ break;
+
+ if (ret == 1)
+ return 1;
+ }
+
+ /* we can treat both ref types equally here */
+ info = (struct btrfs_tree_block_info *)(ei + 1);
+ *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
+ *out_level = btrfs_tree_block_level(eb, info);
+
+ if (ret == 1)
+ *ptr = (unsigned long)-1;
+
+ return 0;
+}
+
+static int __data_list_add(struct list_head *head, u64 inum,
+ u64 extent_data_item_offset, u64 root)
+{
+ struct __data_ref *ref;
+
+ ref = kmalloc(sizeof(*ref), GFP_NOFS);
+ if (!ref)
+ return -ENOMEM;
+
+ ref->inum = inum;
+ ref->extent_data_item_offset = extent_data_item_offset;
+ ref->root = root;
+ list_add_tail(&ref->list, head);
+
+ return 0;
+}
+
+static int __data_list_add_eb(struct list_head *head, struct extent_buffer *eb,
+ struct btrfs_extent_data_ref *dref)
+{
+ return __data_list_add(head, btrfs_extent_data_ref_objectid(eb, dref),
+ btrfs_extent_data_ref_offset(eb, dref),
+ btrfs_extent_data_ref_root(eb, dref));
+}
+
+static int __shared_list_add(struct list_head *head, u64 disk_byte)
+{
+ struct __shared_ref *ref;
+
+ ref = kmalloc(sizeof(*ref), GFP_NOFS);
+ if (!ref)
+ return -ENOMEM;
+
+ ref->disk_byte = disk_byte;
+ list_add_tail(&ref->list, head);
+
+ return 0;
+}
+
+static int __iter_shared_inline_ref_inodes(struct btrfs_fs_info *fs_info,
+ u64 logical, u64 inum,
+ u64 extent_data_item_offset,
+ u64 extent_offset,
+ struct btrfs_path *path,
+ struct list_head *data_refs,
+ iterate_extent_inodes_t *iterate,
+ void *ctx)
+{
+ u64 ref_root;
+ u32 item_size;
+ struct btrfs_key key;
+ struct extent_buffer *eb;
+ struct btrfs_extent_item *ei;
+ struct btrfs_extent_inline_ref *eiref;
+ struct __data_ref *ref;
+ int ret;
+ int type;
+ int last;
+ unsigned long ptr = 0;
+
+ WARN_ON(!list_empty(data_refs));
+ ret = extent_from_logical(fs_info, logical, path, &key);
+ if (ret & BTRFS_EXTENT_FLAG_DATA)
+ ret = -EIO;
+ if (ret < 0)
+ goto out;
+
+ eb = path->nodes[0];
+ ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
+ item_size = btrfs_item_size_nr(eb, path->slots[0]);
+
+ ret = 0;
+ ref_root = 0;
+ /*
+ * as done in iterate_extent_inodes, we first build a list of refs to
+ * iterate, then free the path and then iterate them to avoid deadlocks.
+ */
+ do {
+ last = __get_extent_inline_ref(&ptr, eb, ei, item_size,
+ &eiref, &type);
+ if (last < 0) {
+ ret = last;
+ goto out;
+ }
+ if (type == BTRFS_TREE_BLOCK_REF_KEY ||
+ type == BTRFS_SHARED_BLOCK_REF_KEY) {
+ ref_root = btrfs_extent_inline_ref_offset(eb, eiref);
+ ret = __data_list_add(data_refs, inum,
+ extent_data_item_offset,
+ ref_root);
+ }
+ } while (!ret && !last);
+
+ btrfs_release_path(path);
+
+ if (ref_root == 0) {
+ printk(KERN_ERR "btrfs: failed to find tree block ref "
+ "for shared data backref %llu\n", logical);
+ WARN_ON(1);
+ ret = -EIO;
+ }
+
+out:
+ while (!list_empty(data_refs)) {
+ ref = list_first_entry(data_refs, struct __data_ref, list);
+ list_del(&ref->list);
+ if (!ret)
+ ret = iterate(ref->inum, extent_offset +
+ ref->extent_data_item_offset,
+ ref->root, ctx);
+ kfree(ref);
+ }
+
+ return ret;
+}
+
+static int __iter_shared_inline_ref(struct btrfs_fs_info *fs_info,
+ u64 logical, u64 orig_extent_item_objectid,
+ u64 extent_offset, struct btrfs_path *path,
+ struct list_head *data_refs,
+ iterate_extent_inodes_t *iterate,
+ void *ctx)
+{
+ u64 disk_byte;
+ struct btrfs_key key;
+ struct btrfs_file_extent_item *fi;
+ struct extent_buffer *eb;
+ int slot;
+ int nritems;
+ int ret;
+ int found = 0;
+
+ eb = read_tree_block(fs_info->tree_root, logical,
+ fs_info->tree_root->leafsize, 0);
+ if (!eb)
+ return -EIO;
+
+ /*
+ * from the shared data ref, we only have the leaf but we need
+ * the key. thus, we must look into all items and see that we
+ * find one (some) with a reference to our extent item.
+ */
+ nritems = btrfs_header_nritems(eb);
+ for (slot = 0; slot < nritems; ++slot) {
+ btrfs_item_key_to_cpu(eb, &key, slot);
+ if (key.type != BTRFS_EXTENT_DATA_KEY)
+ continue;
+ fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+ if (!fi) {
+ free_extent_buffer(eb);
+ return -EIO;
+ }
+ disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
+ if (disk_byte != orig_extent_item_objectid) {
+ if (found)
+ break;
+ else
+ continue;
+ }
+ ++found;
+ ret = __iter_shared_inline_ref_inodes(fs_info, logical,
+ key.objectid,
+ key.offset,
+ extent_offset, path,
+ data_refs,
+ iterate, ctx);
+ if (ret)
+ break;
+ }
+
+ if (!found) {
+ printk(KERN_ERR "btrfs: failed to follow shared data backref "
+ "to parent %llu\n", logical);
+ WARN_ON(1);
+ ret = -EIO;
+ }
+
+ free_extent_buffer(eb);
+ return ret;
+}
+
+/*
+ * calls iterate() for every inode that references the extent identified by
+ * the given parameters. will use the path given as a parameter and return it
+ * released.
+ * when the iterator function returns a non-zero value, iteration stops.
+ */
+int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
+ struct btrfs_path *path,
+ u64 extent_item_objectid,
+ u64 extent_offset,
+ iterate_extent_inodes_t *iterate, void *ctx)
+{
+ unsigned long ptr = 0;
+ int last;
+ int ret;
+ int type;
+ u64 logical;
+ u32 item_size;
+ struct btrfs_extent_inline_ref *eiref;
+ struct btrfs_extent_data_ref *dref;
+ struct extent_buffer *eb;
+ struct btrfs_extent_item *ei;
+ struct btrfs_key key;
+ struct list_head data_refs = LIST_HEAD_INIT(data_refs);
+ struct list_head shared_refs = LIST_HEAD_INIT(shared_refs);
+ struct __data_ref *ref_d;
+ struct __shared_ref *ref_s;
+
+ eb = path->nodes[0];
+ ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
+ item_size = btrfs_item_size_nr(eb, path->slots[0]);
+
+ /* first we iterate the inline refs, ... */
+ do {
+ last = __get_extent_inline_ref(&ptr, eb, ei, item_size,
+ &eiref, &type);
+ if (last == -ENOENT) {
+ ret = 0;
+ break;
+ }
+ if (last < 0) {
+ ret = last;
+ break;
+ }
+
+ if (type == BTRFS_EXTENT_DATA_REF_KEY) {
+ dref = (struct btrfs_extent_data_ref *)(&eiref->offset);
+ ret = __data_list_add_eb(&data_refs, eb, dref);
+ } else if (type == BTRFS_SHARED_DATA_REF_KEY) {
+ logical = btrfs_extent_inline_ref_offset(eb, eiref);
+ ret = __shared_list_add(&shared_refs, logical);
+ }
+ } while (!ret && !last);
+
+ /* ... then we proceed to in-tree references and ... */
+ while (!ret) {
+ ++path->slots[0];
+ if (path->slots[0] > btrfs_header_nritems(eb)) {
+ ret = btrfs_next_leaf(fs_info->extent_root, path);
+ if (ret) {
+ if (ret == 1)
+ ret = 0; /* we're done */
+ break;
+ }
+ eb = path->nodes[0];
+ }
+ btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
+ if (key.objectid != extent_item_objectid)
+ break;
+ if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
+ dref = btrfs_item_ptr(eb, path->slots[0],
+ struct btrfs_extent_data_ref);
+ ret = __data_list_add_eb(&data_refs, eb, dref);
+ } else if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
+ ret = __shared_list_add(&shared_refs, key.offset);
+ }
+ }
+
+ btrfs_release_path(path);
+
+ /*
+ * ... only at the very end we can process the refs we found. this is
+ * because the iterator function we call is allowed to make tree lookups
+ * and we have to avoid deadlocks. additionally, we need more tree
+ * lookups ourselves for shared data refs.
+ */
+ while (!list_empty(&data_refs)) {
+ ref_d = list_first_entry(&data_refs, struct __data_ref, list);
+ list_del(&ref_d->list);
+ if (!ret)
+ ret = iterate(ref_d->inum, extent_offset +
+ ref_d->extent_data_item_offset,
+ ref_d->root, ctx);
+ kfree(ref_d);
+ }
+
+ while (!list_empty(&shared_refs)) {
+ ref_s = list_first_entry(&shared_refs, struct __shared_ref,
+ list);
+ list_del(&ref_s->list);
+ if (!ret)
+ ret = __iter_shared_inline_ref(fs_info,
+ ref_s->disk_byte,
+ extent_item_objectid,
+ extent_offset, path,
+ &data_refs,
+ iterate, ctx);
+ kfree(ref_s);
+ }
+
+ return ret;
+}
+
+int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
+ struct btrfs_path *path,
+ iterate_extent_inodes_t *iterate, void *ctx)
+{
+ int ret;
+ u64 offset;
+ struct btrfs_key found_key;
+
+ ret = extent_from_logical(fs_info, logical, path,
+ &found_key);
+ if (ret & BTRFS_EXTENT_FLAG_TREE_BLOCK)
+ ret = -EINVAL;
+ if (ret < 0)
+ return ret;
+
+ offset = logical - found_key.objectid;
+ ret = iterate_extent_inodes(fs_info, path, found_key.objectid,
+ offset, iterate, ctx);
+
+ return ret;
+}
+
+static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
+ struct btrfs_path *path,
+ iterate_irefs_t *iterate, void *ctx)
+{
+ int ret;
+ int slot;
+ u32 cur;
+ u32 len;
+ u32 name_len;
+ u64 parent = 0;
+ int found = 0;
+ struct extent_buffer *eb;
+ struct btrfs_item *item;
+ struct btrfs_inode_ref *iref;
+ struct btrfs_key found_key;
+
+ while (1) {
+ ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
+ &found_key);
+ if (ret < 0)
+ break;
+ if (ret) {
+ ret = found ? 0 : -ENOENT;
+ break;
+ }
+ ++found;
+
+ parent = found_key.offset;
+ slot = path->slots[0];
+ eb = path->nodes[0];
+ /* make sure we can use eb after releasing the path */
+ atomic_inc(&eb->refs);
+ btrfs_release_path(path);
+
+ item = btrfs_item_nr(eb, slot);
+ iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
+
+ for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
+ name_len = btrfs_inode_ref_name_len(eb, iref);
+ /* path must be released before calling iterate()! */
+ ret = iterate(parent, iref, eb, ctx);
+ if (ret) {
+ free_extent_buffer(eb);
+ break;
+ }
+ len = sizeof(*iref) + name_len;
+ iref = (struct btrfs_inode_ref *)((char *)iref + len);
+ }
+ free_extent_buffer(eb);
+ }
+
+ btrfs_release_path(path);
+
+ return ret;
+}
+
+/*
+ * returns 0 if the path could be dumped (probably truncated)
+ * returns <0 in case of an error
+ */
+static int inode_to_path(u64 inum, struct btrfs_inode_ref *iref,
+ struct extent_buffer *eb, void *ctx)
+{
+ struct inode_fs_paths *ipath = ctx;
+ char *fspath;
+ char *fspath_min;
+ int i = ipath->fspath->elem_cnt;
+ const int s_ptr = sizeof(char *);
+ u32 bytes_left;
+
+ bytes_left = ipath->fspath->bytes_left > s_ptr ?
+ ipath->fspath->bytes_left - s_ptr : 0;
+
+ fspath_min = (char *)ipath->fspath->str + (i + 1) * s_ptr;
+ fspath = iref_to_path(ipath->fs_root, ipath->btrfs_path, iref, eb,
+ inum, fspath_min, bytes_left);
+ if (IS_ERR(fspath))
+ return PTR_ERR(fspath);
+
+ if (fspath > fspath_min) {
+ ipath->fspath->str[i] = fspath;
+ ++ipath->fspath->elem_cnt;
+ ipath->fspath->bytes_left = fspath - fspath_min;
+ } else {
+ ++ipath->fspath->elem_missed;
+ ipath->fspath->bytes_missing += fspath_min - fspath;
+ ipath->fspath->bytes_left = 0;
+ }
+
+ return 0;
+}
+
+/*
+ * this dumps all file system paths to the inode into the ipath struct, provided
+ * is has been created large enough. each path is zero-terminated and accessed
+ * from ipath->fspath->str[i].
+ * when it returns, there are ipath->fspath->elem_cnt number of paths available
+ * in ipath->fspath->str[]. when the allocated space wasn't sufficient, the
+ * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
+ * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
+ * have been needed to return all paths.
+ */
+int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
+{
+ return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
+ inode_to_path, ipath);
+}
+
+/*
+ * allocates space to return multiple file system paths for an inode.
+ * total_bytes to allocate are passed, note that space usable for actual path
+ * information will be total_bytes - sizeof(struct inode_fs_paths).
+ * the returned pointer must be freed with free_ipath() in the end.
+ */
+struct btrfs_data_container *init_data_container(u32 total_bytes)
+{
+ struct btrfs_data_container *data;
+ size_t alloc_bytes;
+
+ alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
+ data = kmalloc(alloc_bytes, GFP_NOFS);
+ if (!data)
+ return ERR_PTR(-ENOMEM);
+
+ if (total_bytes >= sizeof(*data)) {
+ data->bytes_left = total_bytes - sizeof(*data);
+ data->bytes_missing = 0;
+ } else {
+ data->bytes_missing = sizeof(*data) - total_bytes;
+ data->bytes_left = 0;
+ }
+
+ data->elem_cnt = 0;
+ data->elem_missed = 0;
+
+ return data;
+}
+
+/*
+ * allocates space to return multiple file system paths for an inode.
+ * total_bytes to allocate are passed, note that space usable for actual path
+ * information will be total_bytes - sizeof(struct inode_fs_paths).
+ * the returned pointer must be freed with free_ipath() in the end.
+ */
+struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
+ struct btrfs_path *path)
+{
+ struct inode_fs_paths *ifp;
+ struct btrfs_data_container *fspath;
+
+ fspath = init_data_container(total_bytes);
+ if (IS_ERR(fspath))
+ return (void *)fspath;
+
+ ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
+ if (!ifp) {
+ kfree(fspath);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ ifp->btrfs_path = path;
+ ifp->fspath = fspath;
+ ifp->fs_root = fs_root;
+
+ return ifp;
+}
+
+void free_ipath(struct inode_fs_paths *ipath)
+{
+ kfree(ipath);
+}