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btrfs-progs: check: fix wrong @offset used in find_possible_backrefs()

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Function find_possible_backrefs() is used to locate the file extents
referring to an data extent.

For data extent backref, its btrfs_extent_data_ref structure has
the following members:
- root
  Which root refers to this data extent

- objectid
  Which inode refers to this data extent

- offset
  Search *hint*.
  Its value is @file_offset - @extent_offset.

While for @file_offset, it's directly recorded in (INO EXTENT_DATA
FILE_OFFSET) key.

So when searching the file extents refers to this data extent, we can't
use btrfs_extent_data_ref::offset as search key::offset.

We must search from file offset 0, and iterate all file extents until we
hit a file extent matches the data backref.

Thankfully such time consuming behavior is not triggered frequently,
it only gets called for repair, so it shouldn't affect normal check
routine.

Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
[Update commit message]
Signed-off-by: Qu Wenruo <wqu@suse.com>
This commit is contained in:
Su Yanjun 2019-02-27 14:05:48 +08:00 committed by Qu Wenruo
parent b6a0d97cba
commit 3b35deeadd
1 changed files with 92 additions and 18 deletions
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110
check/main.c
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@ -7132,6 +7132,89 @@ out:
return ret ? ret : nr_del;
}
/*
* Based extent backref item, we find all file extent items in the fs tree. By
* the info we can rebuild the extent backref item
*/
static int __find_possible_backrefs(struct btrfs_root *root,
u64 owner, u64 offset, u64 bytenr, u64 *refs_ret,
u64 *bytes_ret)
{
int ret = 0;
struct btrfs_path path;
struct btrfs_key key;
struct btrfs_key found_key;
struct btrfs_file_extent_item *fi;
struct extent_buffer *leaf;
u64 backref_offset, disk_bytenr;
int slot;
btrfs_init_path(&path);
key.objectid = owner;
key.type = BTRFS_INODE_ITEM_KEY;
key.offset = 0;
ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
if (ret > 0)
ret = -ENOENT;
if (ret) {
btrfs_release_path(&path);
return ret;
}
btrfs_release_path(&path);
key.objectid = owner;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = 0;
ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
if (ret < 0) {
btrfs_release_path(&path);
return ret;
}
while (1) {
leaf = path.nodes[0];
slot = path.slots[0];
if (slot >= btrfs_header_nritems(leaf)) {
ret = btrfs_next_leaf(root, &path);
if (ret) {
if (ret > 0)
ret = 0;
break;
}
leaf = path.nodes[0];
slot = path.slots[0];
}
btrfs_item_key_to_cpu(leaf, &found_key, slot);
if ((found_key.objectid != owner) ||
(found_key.type != BTRFS_EXTENT_DATA_KEY))
break;
fi = btrfs_item_ptr(leaf, slot,
struct btrfs_file_extent_item);
backref_offset = found_key.offset -
btrfs_file_extent_offset(leaf, fi);
disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
*bytes_ret = btrfs_file_extent_disk_num_bytes(leaf,
fi);
if ((disk_bytenr == bytenr) &&
(backref_offset == offset)) {
(*refs_ret)++;
}
path.slots[0]++;
}
btrfs_release_path(&path);
return ret;
}
static int find_possible_backrefs(struct btrfs_fs_info *info,
struct btrfs_path *path,
struct cache_tree *extent_cache,
@ -7141,9 +7224,9 @@ static int find_possible_backrefs(struct btrfs_fs_info *info,
struct extent_backref *back, *tmp;
struct data_backref *dback;
struct cache_extent *cache;
struct btrfs_file_extent_item *fi;
struct btrfs_key key;
u64 bytenr, bytes;
u64 refs;
int ret;
rbtree_postorder_for_each_entry_safe(back, tmp,
@ -7171,24 +7254,15 @@ static int find_possible_backrefs(struct btrfs_fs_info *info,
if (IS_ERR(root))
return PTR_ERR(root);
key.objectid = dback->owner;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = dback->offset;
ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
if (ret) {
btrfs_release_path(path);
if (ret < 0)
return ret;
/* Didn't find it, we can carry on */
ret = 0;
refs = 0;
bytes = 0;
ret = __find_possible_backrefs(root, dback->owner,
dback->offset, rec->start, &refs, &bytes);
if (ret)
continue;
}
fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
struct btrfs_file_extent_item);
bytenr = btrfs_file_extent_disk_bytenr(path->nodes[0], fi);
bytes = btrfs_file_extent_disk_num_bytes(path->nodes[0], fi);
btrfs_release_path(path);
bytenr = rec->start;
cache = lookup_cache_extent(extent_cache, bytenr, 1);
if (cache) {
struct extent_record *tmp;
@ -7207,7 +7281,7 @@ static int find_possible_backrefs(struct btrfs_fs_info *info,
continue;
}
dback->found_ref += 1;
dback->found_ref += refs;
dback->disk_bytenr = bytenr;
dback->bytes = bytes;