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Revert "fs: btrfs: fix false negatives in ROOT_ITEM search"

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Per Pierre this change shouldn't have been applied as it was superseded
by "fs: btrfs: fix btrfs_search_tree invalid results" which is also
applied now as 1627e5e598.

This reverts commit 633967f981.

Signed-off-by: Tom Rini <trini@konsulko.com>
This commit is contained in:
Tom Rini 2019-04-27 11:34:55 -04:00
parent 6b8e57338f
commit 6aebc0d11a
1 changed files with 6 additions and 38 deletions
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44
fs/btrfs/ctree.h
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@ -292,52 +292,20 @@ btrfs_search_tree_key_type(const struct btrfs_root *root, u64 objectid,
{ {
struct btrfs_key key, *res; struct btrfs_key key, *res;
/*
* In some cases (e.g. tree roots), we need to look for a given
* objectid and type without knowing the offset value (3rd element of a
* btrfs tree node key). We can rely on the fact that btrfs_search_tree
* returns the first element with key >= search_key, and then perform
* our own comparison between the returned element and the search key.
*
* It is tempting to use a search key with offset 0 to perform this
* "fuzzy search". This would return the first item with the (objectid,
* type) we're looking for. However, using offset 0 has the wrong
* behavior when the wanted item is the first in a leaf: since our
* search key will be lower than the wanted item, the recursive search
* will explore the wrong branch of the tree.
*
* Instead, use the largest possible offset (-1). The result of this
* search will either be:
* 1. An element with the (objectid, type) we're looking for, if it
* has offset -1 or if it is the last element in its leaf.
* 2. The first element *after* an element with the (objectid, type)
*/
key.objectid = objectid; key.objectid = objectid;
key.type = type; key.type = type;
key.offset = -1; key.offset = 0;
if (btrfs_search_tree(root, &key, path)) if (btrfs_search_tree(root, &key, path))
return NULL; return NULL;
/* res = btrfs_path_leaf_key(path);
* Compare with the previous element first -- this is the likely case if (btrfs_comp_keys_type(&key, res)) {
* since the result of the search is only what we want if it had offset btrfs_free_path(path);
* == -1 or if it was last in its leaf. return NULL;
*/
if (path->slots[0] > 0) {
path->slots[0]--;
res = btrfs_path_leaf_key(path);
if (!btrfs_comp_keys_type(&key, res))
return res;
path->slots[0]++;
} }
res = btrfs_path_leaf_key(path); return res;
if (!btrfs_comp_keys_type(&key, res))
return res;
btrfs_free_path(path);
return NULL;
} }
static inline u32 btrfs_path_item_size(struct btrfs_path *p) static inline u32 btrfs_path_item_size(struct btrfs_path *p)