xfs: always use unwritten extents for direct I/O writes

To allow aio writes beyond i_size we need to create unwritten extents for
newly allocated blocks, similar to how we already do inside i_size.

Instead of adding another special case we now use unwritten extents
unconditionally.  This also marks the end of directly allocation data
extents in all of XFS - we now always use either delalloc or unwritten
extents.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>

fs/xfs/xfs_iomap.c

@@ -128,7 +128,6 @@ xfs_iomap_write_direct(
 	xfs_fsblock_t	firstfsb;
 	xfs_extlen_t	extsz, temp;
 	int		nimaps;
-	int		bmapi_flag;
 	int		quota_flag;
 	int		rt;
 	xfs_trans_t	*tp;
@@ -200,18 +199,15 @@ xfs_iomap_write_direct(
 
 	xfs_trans_ijoin(tp, ip, 0);
 
-	bmapi_flag = 0;
-	if (offset < XFS_ISIZE(ip) || extsz)
-		bmapi_flag |= XFS_BMAPI_PREALLOC;
-
 	/*
 	 * From this point onwards we overwrite the imap pointer that the
 	 * caller gave to us.
 	 */
 	xfs_bmap_init(&free_list, &firstfsb);
 	nimaps = 1;
-	error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb, bmapi_flag,
-				&firstfsb, 0, imap, &nimaps, &free_list);
+	error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
+				XFS_BMAPI_PREALLOC, &firstfsb, 0,
+				imap, &nimaps, &free_list);
 	if (error)
 		goto out_bmap_cancel;