fat: do not send discards as barriers

fat already uses synchronous discards, no need to add I/O barriers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

fs/fat/fatent.c

@@ -579,7 +579,7 @@ int fat_free_clusters(struct inode *inode, int cluster)
 					fat_clus_to_blknr(sbi, first_cl),
 					nr_clus * sbi->sec_per_clus,
 					GFP_NOFS,
-					BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER);
+					BLKDEV_IFL_WAIT);
 
 				first_cl = cluster;
 			}