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Btrfs: don't assume to be on the correct extent in add_all_parents

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add_all_parents did assume that path is already at a correct extent data
item, which may not be true in case of data extents that were partly
rewritten and splitted.

We need to check if we're on a matching extent for every item and only
for the ones after the first. The loop is changed to do this now.

This patch also fixes a bug introduced with commit 3b127fd8 "Btrfs:
remove obsolete btrfs_next_leaf call from __resolve_indirect_ref".
The removal of next_leaf did sometimes result in slot==nritems when
the above described case happens, and thus resulting in invalid values
(e.g. wanted_obejctid) in add_all_parents (leading to missed backrefs
or even crashes).

Signed-off-by: Alexander Block <ablock84@googlemail.com>
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
Alexander Block 2012-06-19 07:42:26 -06:00 committed by Chris Mason
parent 1c8f52a5e9
commit 69bca40d41
1 changed files with 52 additions and 42 deletions
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94
fs/btrfs/backref.c
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@ -179,61 +179,74 @@ static int __add_prelim_ref(struct list_head *head, u64 root_id,
static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
struct ulist *parents, int level,
struct btrfs_key *key, u64 time_seq,
struct btrfs_key *key_for_search, u64 time_seq,
u64 wanted_disk_byte,
const u64 *extent_item_pos)
{
int ret;
int slot = path->slots[level];
struct extent_buffer *eb = path->nodes[level];
int ret = 0;
int slot;
struct extent_buffer *eb;
struct btrfs_key key;
struct btrfs_file_extent_item *fi;
struct extent_inode_elem *eie = NULL;
u64 disk_byte;
u64 wanted_objectid = key->objectid;
add_parent:
if (level == 0 && extent_item_pos) {
fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
ret = check_extent_in_eb(key, eb, fi, *extent_item_pos, &eie);
if (level != 0) {
eb = path->nodes[level];
ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
if (ret < 0)
return ret;
}
ret = ulist_add(parents, eb->start, (unsigned long)eie, GFP_NOFS);
if (ret < 0)
return ret;
if (level != 0)
return 0;
}
/*
* if the current leaf is full with EXTENT_DATA items, we must
* check the next one if that holds a reference as well.
* ref->count cannot be used to skip this check.
* repeat this until we don't find any additional EXTENT_DATA items.
* We normally enter this function with the path already pointing to
* the first item to check. But sometimes, we may enter it with
* slot==nritems. In that case, go to the next leaf before we continue.
*/
while (1) {
eie = NULL;
if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))
ret = btrfs_next_old_leaf(root, path, time_seq);
if (ret < 0)
return ret;
if (ret)
return 0;
while (!ret) {
eb = path->nodes[0];
for (slot = 0; slot < btrfs_header_nritems(eb); ++slot) {
btrfs_item_key_to_cpu(eb, key, slot);
if (key->objectid != wanted_objectid ||
key->type != BTRFS_EXTENT_DATA_KEY)
return 0;
fi = btrfs_item_ptr(eb, slot,
struct btrfs_file_extent_item);
disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
if (disk_byte == wanted_disk_byte)
goto add_parent;
slot = path->slots[0];
btrfs_item_key_to_cpu(eb, &key, slot);
if (key.objectid != key_for_search->objectid ||
key.type != BTRFS_EXTENT_DATA_KEY)
break;
fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
if (disk_byte == wanted_disk_byte) {
eie = NULL;
if (extent_item_pos) {
ret = check_extent_in_eb(&key, eb, fi,
*extent_item_pos,
&eie);
if (ret < 0)
break;
}
if (!ret) {
ret = ulist_add(parents, eb->start,
(unsigned long)eie, GFP_NOFS);
if (ret < 0)
break;
if (!extent_item_pos) {
ret = btrfs_next_old_leaf(root, path,
time_seq);
continue;
}
}
}
ret = btrfs_next_old_item(root, path, time_seq);
}
return 0;
if (ret > 0)
ret = 0;
return ret;
}
/*
@ -250,7 +263,6 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
struct btrfs_path *path;
struct btrfs_root *root;
struct btrfs_key root_key;
struct btrfs_key key = {0};
struct extent_buffer *eb;
int ret = 0;
int root_level;
@ -295,11 +307,9 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
goto out;
}
if (level == 0)
btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
ret = add_all_parents(root, path, parents, level, &key, time_seq,
ref->wanted_disk_byte, extent_item_pos);
ret = add_all_parents(root, path, parents, level, &ref->key_for_search,
time_seq, ref->wanted_disk_byte,
extent_item_pos);
out:
btrfs_free_path(path);
return ret;