btrfs: handle empty list of NOCOW ordered extents with checksum list

Currently we BUG_ON() in btrfs_finish_one_ordered() if we are finishing
an ordered extent that is flagged as NOCOW, but it's checksum list is
not empty.

This is clearly a logic error which we can recover from by aborting the
transaction.

For developer builds which enable CONFIG_BTRFS_ASSERT, also ASSERT()
that the list is empty.

Suggested-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -3088,7 +3088,12 @@ int btrfs_finish_one_ordered(struct btrfs_ordered_extent *ordered_extent)
 
 	if (test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags)) {
 		/* Logic error */
-		BUG_ON(!list_empty(&ordered_extent->list));
+		ASSERT(list_empty(&ordered_extent->list));
+		if (!list_empty(&ordered_extent->list)) {
+			ret = -EINVAL;
+			btrfs_abort_transaction(trans, ret);
+			goto out;
+		}
 
 		btrfs_inode_safe_disk_i_size_write(inode, 0);
 		ret = btrfs_update_inode_fallback(trans, inode);