[PATCH] FAT: DIO-write fallback to normal buffered

If the DIO write on FAT is expanding the size, it will be fail by -EINVAL,
because FAT can't handle it now.

This patch fallback it to the normal buffered-write and would return
success.
Signed-off-by: NOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Acked-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/fat/inode.c

@@ -173,10 +173,12 @@ static ssize_t fat_direct_IO(int rw, struct kiocb *iocb,
 		 *
 		 * But we must fill the remaining area or hole by nul for
 		 * updating ->mmu_private.
+		 *
+		 * Return 0, and fallback to normal buffered write.
 		 */
 		loff_t size = offset + iov_length(iov, nr_segs);
 		if (MSDOS_I(inode)->mmu_private < size)
-			return -EINVAL;
+			return 0;
 	}
 
 	/*