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authorYan Zheng <zheng.yan@oracle.com>2009-07-22 09:59:00 -0400
committerChris Mason <chris.mason@oracle.com>2009-07-22 09:59:00 -0400
commit33c66f430bfa3a033e70470e4c93f967156b696d (patch)
tree5af7edc4564aa3f32033b364495828eb32b690a7 /fs/btrfs/ctree.c
parente457afec60fdbd86b963d36f4a8a9285088c6043 (diff)
downloadlinux-33c66f430bfa3a033e70470e4c93f967156b696d.tar.bz2
Btrfs: fix locking issue in btrfs_find_next_key
When walking up the tree, btrfs_find_next_key assumes the upper level tree block is properly locked. This isn't always true even path->keep_locks is 1. This is because btrfs_find_next_key may advance path->slots[] several times instead of only once. When 'path->slots[level] >= btrfs_header_nritems(path->nodes[level])' is found, we can't guarantee the original value of 'path->slots[level]' is 'btrfs_header_nritems(path->nodes[level]) - 1'. If it's not, the tree block at 'level + 1' isn't locked. This patch fixes the issue by explicitly checking the locking state, re-searching the tree if it's not locked. Signed-off-by: Yan Zheng <zheng.yan@oracle.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/ctree.c')
-rw-r--r--fs/btrfs/ctree.c95
1 files changed, 62 insertions, 33 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 7bb66c65ddfd..fdd423a550d6 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1701,6 +1701,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
struct extent_buffer *b;
int slot;
int ret;
+ int err;
int level;
int lowest_unlock = 1;
u8 lowest_level = 0;
@@ -1737,8 +1738,6 @@ again:
p->locks[level] = 1;
if (cow) {
- int wret;
-
/*
* if we don't really need to cow this block
* then we don't want to set the path blocking,
@@ -1749,12 +1748,12 @@ again:
btrfs_set_path_blocking(p);
- wret = btrfs_cow_block(trans, root, b,
- p->nodes[level + 1],
- p->slots[level + 1], &b);
- if (wret) {
+ err = btrfs_cow_block(trans, root, b,
+ p->nodes[level + 1],
+ p->slots[level + 1], &b);
+ if (err) {
free_extent_buffer(b);
- ret = wret;
+ ret = err;
goto done;
}
}
@@ -1793,41 +1792,45 @@ cow_done:
ret = bin_search(b, key, level, &slot);
if (level != 0) {
- if (ret && slot > 0)
+ int dec = 0;
+ if (ret && slot > 0) {
+ dec = 1;
slot -= 1;
+ }
p->slots[level] = slot;
- ret = setup_nodes_for_search(trans, root, p, b, level,
+ err = setup_nodes_for_search(trans, root, p, b, level,
ins_len);
- if (ret == -EAGAIN)
+ if (err == -EAGAIN)
goto again;
- else if (ret)
+ if (err) {
+ ret = err;
goto done;
+ }
b = p->nodes[level];
slot = p->slots[level];
unlock_up(p, level, lowest_unlock);
- /* this is only true while dropping a snapshot */
if (level == lowest_level) {
- ret = 0;
+ if (dec)
+ p->slots[level]++;
goto done;
}
- ret = read_block_for_search(trans, root, p,
+ err = read_block_for_search(trans, root, p,
&b, level, slot, key);
- if (ret == -EAGAIN)
+ if (err == -EAGAIN)
goto again;
-
- if (ret == -EIO)
+ if (err) {
+ ret = err;
goto done;
+ }
if (!p->skip_locking) {
- int lret;
-
btrfs_clear_path_blocking(p, NULL);
- lret = btrfs_try_spin_lock(b);
+ err = btrfs_try_spin_lock(b);
- if (!lret) {
+ if (!err) {
btrfs_set_path_blocking(p);
btrfs_tree_lock(b);
btrfs_clear_path_blocking(p, b);
@@ -1837,16 +1840,14 @@ cow_done:
p->slots[level] = slot;
if (ins_len > 0 &&
btrfs_leaf_free_space(root, b) < ins_len) {
- int sret;
-
btrfs_set_path_blocking(p);
- sret = split_leaf(trans, root, key,
- p, ins_len, ret == 0);
+ err = split_leaf(trans, root, key,
+ p, ins_len, ret == 0);
btrfs_clear_path_blocking(p, NULL);
- BUG_ON(sret > 0);
- if (sret) {
- ret = sret;
+ BUG_ON(err > 0);
+ if (err) {
+ ret = err;
goto done;
}
}
@@ -4042,10 +4043,9 @@ out:
* calling this function.
*/
int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
- struct btrfs_key *key, int lowest_level,
+ struct btrfs_key *key, int level,
int cache_only, u64 min_trans)
{
- int level = lowest_level;
int slot;
struct extent_buffer *c;
@@ -4058,11 +4058,40 @@ int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
c = path->nodes[level];
next:
if (slot >= btrfs_header_nritems(c)) {
- level++;
- if (level == BTRFS_MAX_LEVEL)
+ int ret;
+ int orig_lowest;
+ struct btrfs_key cur_key;
+ if (level + 1 >= BTRFS_MAX_LEVEL ||
+ !path->nodes[level + 1])
return 1;
- continue;
+
+ if (path->locks[level + 1]) {
+ level++;
+ continue;
+ }
+
+ slot = btrfs_header_nritems(c) - 1;
+ if (level == 0)
+ btrfs_item_key_to_cpu(c, &cur_key, slot);
+ else
+ btrfs_node_key_to_cpu(c, &cur_key, slot);
+
+ orig_lowest = path->lowest_level;
+ btrfs_release_path(root, path);
+ path->lowest_level = level;
+ ret = btrfs_search_slot(NULL, root, &cur_key, path,
+ 0, 0);
+ path->lowest_level = orig_lowest;
+ if (ret < 0)
+ return ret;
+
+ c = path->nodes[level];
+ slot = path->slots[level];
+ if (ret == 0)
+ slot++;
+ goto next;
}
+
if (level == 0)
btrfs_item_key_to_cpu(c, key, slot);
else {