Btrfs: Prevent root_list corruption

I was seeing root_list corruption on unmount during fs resize in 3.4-rc4; add
correct locking to address this.

Signed-off-by: Daniel J Blueman <daniel@quora.org>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 017281dbb2a7..5a105a086acf 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -1279,7 +1279,9 @@ static int __update_reloc_root(struct btrfs_root *root, int del)
                 if (rb_node)
                         backref_tree_panic(rb_node, -EEXIST, node->bytenr);
         } else {
+                spin_lock(&root->fs_info->trans_lock);
                 list_del_init(&root->root_list);
+                spin_unlock(&root->fs_info->trans_lock);
                 kfree(node);
         }
         return 0;