Btrfs: fix deadlock caused by the race between relocation

We can not do flushable reservation for the relocation when we create snapshot,
because it may make the transaction commit task and the flush task wait for
each other and the deadlock happens.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
(cherry picked from commit 62f30c5462374b991e7e3f42d49ce2265c1b82f1)

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 960835eaf4da7acfd4b9f3f11dd0fb16f811b007..6a0574e923bc6a33b4965976328222dcf0a61cb0 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -882,8 +882,8 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
        btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
 
        if (to_reserve > 0) {
-               ret = btrfs_block_rsv_add(root, &pending->block_rsv,
-                                         to_reserve);
+               ret = btrfs_block_rsv_add_noflush(root, &pending->block_rsv,
+                                                 to_reserve);
                if (ret) {
                        pending->error = ret;
                        goto fail;