btrfs: clear defrag status of a root if starting transaction fails

stable inclusion
from stable-5.10.50
commit 80d05ce58a0b22595b1bb80ed8d0cd03e7d924c4
bugzilla: 174522 https://gitee.com/openeuler/kernel/issues/I4DNFY

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=80d05ce58a0b22595b1bb80ed8d0cd03e7d924c4

--------------------------------

commit 6819703f upstream.

The defrag loop processes leaves in batches and starting transaction for
each. The whole defragmentation on a given root is protected by a bit
but in case the transaction fails, the bit is not cleared

In case the transaction fails the bit would prevent starting
defragmentation again, so make sure it's cleared.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/btrfs/transaction.c

@@ -1382,8 +1382,10 @@ int btrfs_defrag_root(struct btrfs_root *root)
 
 	while (1) {
 		trans = btrfs_start_transaction(root, 0);
-		if (IS_ERR(trans))
-			return PTR_ERR(trans);
+		if (IS_ERR(trans)) {
+			ret = PTR_ERR(trans);
+			break;
+		}
 
 		ret = btrfs_defrag_leaves(trans, root);