xfs: fix the extent count when allocating an new indirection array entry

commit bb86d21 upstream.

At xfs_iext_add(), if extent(s) are being appended to the last page in
the indirection array and the new extent(s) don't fit in the page, the
number of extents(erp->er_extcount) in a new allocated entry should be
the minimum value between count and XFS_LINEAR_EXTS, instead of count.

For now, there is no existing test case can demonstrates a problem with
the er_extcount being set incorrectly here, but it obviously like a bug.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

Signed-off-by: Jiri Slaby <jslaby@suse.cz>

fs/xfs/xfs_inode_fork.c

@@ -1031,15 +1031,14 @@ xfs_iext_add(
 		 * the next index needed in the indirection array.
 		 */
 		else {
-			int	count = ext_diff;
+			uint	count = ext_diff;
 
 			while (count) {
 				erp = xfs_iext_irec_new(ifp, erp_idx);
-				erp->er_extcount = count;
-				count -= MIN(count, (int)XFS_LINEAR_EXTS);
-				if (count) {
+				erp->er_extcount = min(count, XFS_LINEAR_EXTS);
+				count -= erp->er_extcount;
+				if (count)
 					erp_idx++;
-				}
 			}
 		}
 	}