btrfs: abort transaction on btrfs_reloc_cow_block()

When btrfs_reloc_cow_block() failed in __btrfs_cow_block(), current
code just return a err-value to caller, but leave new_created extent
buffer exist and locked.

Then subsequent code (in relocate) try to lock above eb again,
and caused deadlock without any dmesg.
(eb lock use wait_event(), so no lockdep message)

It is hard to do recover work in __btrfs_cow_block() at this error
point, but we can abort transaction to avoid deadlock and operate on
unstable state.a

It also helps developer to find wrong place quickly.
(better than a frozen fs without any dmesg before patch)

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 54114b4887ddd5d1cdb393df3a857dac88cac5ac..5f745eadf77dd07454ccb0c1d201124738cb4edc 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1159,8 +1159,10 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
 
        if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
                ret = btrfs_reloc_cow_block(trans, root, buf, cow);
-               if (ret)
+               if (ret) {
+                       btrfs_abort_transaction(trans, root, ret);
                        return ret;
+               }
        }
 
        if (buf == root->node) {