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authorJosef Bacik <jbacik@fb.com>2014-03-29 01:16:01 +0400
committerChris Mason <clm@fb.com>2014-04-07 20:08:39 +0400
commit3f8a18cc53bd1be26eb5b5247e1386ad0e21b623 (patch)
tree266eeb3baf38b968ae2186575ae70ef431cf159f /fs/btrfs/ctree.c
parent9e351cc862b098d8ec8f8022d110932490794925 (diff)
downloadlinux-3f8a18cc53bd1be26eb5b5247e1386ad0e21b623.tar.xz
Btrfs: hold the commit_root_sem when getting the commit root during send
We currently rely too heavily on roots being read-only to save us from just accessing root->commit_root. We can easily balance blocks out from underneath a read only root, so to save us from getting screwed make sure we only access root->commit_root under the commit root sem. Thanks, Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs/btrfs/ctree.c')
-rw-r--r--fs/btrfs/ctree.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 9d89c1648e8e..1bcfcdb23cf4 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2769,9 +2769,13 @@ again:
* the commit roots are read only
* so we always do read locks
*/
+ if (p->need_commit_sem)
+ down_read(&root->fs_info->commit_root_sem);
b = root->commit_root;
extent_buffer_get(b);
level = btrfs_header_level(b);
+ if (p->need_commit_sem)
+ up_read(&root->fs_info->commit_root_sem);
if (!p->skip_locking)
btrfs_tree_read_lock(b);
} else {
@@ -5436,6 +5440,7 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
* the right if possible or go up and right.
*/
+ down_read(&left_root->fs_info->commit_root_sem);
left_level = btrfs_header_level(left_root->commit_root);
left_root_level = left_level;
left_path->nodes[left_level] = left_root->commit_root;
@@ -5445,6 +5450,7 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
right_root_level = right_level;
right_path->nodes[right_level] = right_root->commit_root;
extent_buffer_get(right_path->nodes[right_level]);
+ up_read(&left_root->fs_info->commit_root_sem);
if (left_level == 0)
btrfs_item_key_to_cpu(left_path->nodes[left_level],