Btrfs: fix accessing the root pointer in tree mod log functions
The tree mod log functions were accessing root->node->... directly, without
use of btrfs_root_node() or explicit rcu locking. This could lead to an
extent buffer reference being leaked and another reference being freed too
early when preemtion was enabled.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 1180209..d7e0576 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1069,11 +1069,11 @@
*/
static struct tree_mod_elem *
__tree_mod_log_oldest_root(struct btrfs_fs_info *fs_info,
- struct btrfs_root *root, u64 time_seq)
+ struct extent_buffer *eb_root, u64 time_seq)
{
struct tree_mod_elem *tm;
struct tree_mod_elem *found = NULL;
- u64 root_logical = root->node->start;
+ u64 root_logical = eb_root->start;
int looped = 0;
if (!time_seq)
@@ -1107,7 +1107,6 @@
found = tm;
root_logical = tm->old_root.logical;
- BUG_ON(root_logical == root->node->start);
looped = 1;
}
@@ -1245,30 +1244,31 @@
get_old_root(struct btrfs_root *root, u64 time_seq)
{
struct tree_mod_elem *tm;
- struct extent_buffer *eb;
+ struct extent_buffer *eb = NULL;
+ struct extent_buffer *eb_root;
struct extent_buffer *old;
struct tree_mod_root *old_root = NULL;
u64 old_generation = 0;
u64 logical;
u32 blocksize;
- eb = btrfs_read_lock_root_node(root);
- tm = __tree_mod_log_oldest_root(root->fs_info, root, time_seq);
+ eb_root = btrfs_read_lock_root_node(root);
+ tm = __tree_mod_log_oldest_root(root->fs_info, eb_root, time_seq);
if (!tm)
- return root->node;
+ return eb_root;
if (tm->op == MOD_LOG_ROOT_REPLACE) {
old_root = &tm->old_root;
old_generation = tm->generation;
logical = old_root->logical;
} else {
- logical = root->node->start;
+ logical = eb_root->start;
}
tm = tree_mod_log_search(root->fs_info, logical, time_seq);
if (old_root && tm && tm->op != MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
- btrfs_tree_read_unlock(root->node);
- free_extent_buffer(root->node);
+ btrfs_tree_read_unlock(eb_root);
+ free_extent_buffer(eb_root);
blocksize = btrfs_level_size(root, old_root->level);
old = read_tree_block(root, logical, blocksize, 0);
if (!old) {
@@ -1280,13 +1280,13 @@
free_extent_buffer(old);
}
} else if (old_root) {
- btrfs_tree_read_unlock(root->node);
- free_extent_buffer(root->node);
+ btrfs_tree_read_unlock(eb_root);
+ free_extent_buffer(eb_root);
eb = alloc_dummy_extent_buffer(logical, root->nodesize);
} else {
- eb = btrfs_clone_extent_buffer(root->node);
- btrfs_tree_read_unlock(root->node);
- free_extent_buffer(root->node);
+ eb = btrfs_clone_extent_buffer(eb_root);
+ btrfs_tree_read_unlock(eb_root);
+ free_extent_buffer(eb_root);
}
if (!eb)
@@ -1296,7 +1296,7 @@
if (old_root) {
btrfs_set_header_bytenr(eb, eb->start);
btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV);
- btrfs_set_header_owner(eb, root->root_key.objectid);
+ btrfs_set_header_owner(eb, btrfs_header_owner(eb_root));
btrfs_set_header_level(eb, old_root->level);
btrfs_set_header_generation(eb, old_generation);
}
@@ -1313,15 +1313,15 @@
{
struct tree_mod_elem *tm;
int level;
+ struct extent_buffer *eb_root = btrfs_root_node(root);
- tm = __tree_mod_log_oldest_root(root->fs_info, root, time_seq);
+ tm = __tree_mod_log_oldest_root(root->fs_info, eb_root, time_seq);
if (tm && tm->op == MOD_LOG_ROOT_REPLACE) {
level = tm->old_root.level;
} else {
- rcu_read_lock();
- level = btrfs_header_level(root->node);
- rcu_read_unlock();
+ level = btrfs_header_level(eb_root);
}
+ free_extent_buffer(eb_root);
return level;
}