Btrfs: avoid deadlock on transaction waiting list

Only let one trans handle to wait for other handles, otherwise we
will get ABBA issues.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index d8fce6fe9cf8..fedede1fe178 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1457,6 +1457,13 @@ static void cleanup_transaction(struct btrfs_trans_handle *trans,
         btrfs_abort_transaction(trans, root, err);
 
         spin_lock(&root->fs_info->trans_lock);
+
+        if (list_empty(&cur_trans->list)) {
+                spin_unlock(&root->fs_info->trans_lock);
+                btrfs_end_transaction(trans, root);
+                return;
+        }
+
         list_del_init(&cur_trans->list);
         if (cur_trans == root->fs_info->running_transaction) {
                 root->fs_info->trans_no_join = 1;