Merge tag 'for-4.17-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs fix from David Sterba:
 "A one-liner that prevents leaking an internal error value 1 out of the
  ftruncate syscall.

  This has been observed in practice. The steps to reproduce make a
  common pattern (open/write/fync/ftruncate) but also need the
  application to not check only for negative values and happens only for
  compressed inlined files.

  The conditions are narrow but as this could break userspace I think
  it's better to merge it now and not wait for the merge window"

* tag 'for-4.17-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  Btrfs: fix error handling in btrfs_truncate()

fs/btrfs/inode.c

@@ -9117,7 +9117,8 @@ static int btrfs_truncate(struct inode *inode, bool skip_writeback)
 						 BTRFS_EXTENT_DATA_KEY);
 		trans->block_rsv = &fs_info->trans_block_rsv;
 		if (ret != -ENOSPC && ret != -EAGAIN) {
-			err = ret;
+			if (ret < 0)
+				err = ret;
 			break;
 		}