swap: do not send discards as barriers

The swap code already uses synchronous discards, no need to add I/O barriers.

tj: superflous newlines removed.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NHugh Dickins <hughd@google.com>
Tested-by: NNigel Cunningham <nigel@tuxonice.net>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

mm/swapfile.c

@@ -141,8 +141,7 @@ static int discard_swap(struct swap_info_struct *si)
 	nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
 	if (nr_blocks) {
 		err = blkdev_issue_discard(si->bdev, start_block,
-				nr_blocks, GFP_KERNEL,
-				BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER);
+				nr_blocks, GFP_KERNEL, BLKDEV_IFL_WAIT);
 		if (err)
 			return err;
 		cond_resched();
@@ -153,8 +152,7 @@ static int discard_swap(struct swap_info_struct *si)
 		nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
 
 		err = blkdev_issue_discard(si->bdev, start_block,
-				nr_blocks, GFP_KERNEL,
-				BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER);
+				nr_blocks, GFP_KERNEL, BLKDEV_IFL_WAIT);
 		if (err)
 			break;
 
@@ -193,8 +191,7 @@ static void discard_swap_cluster(struct swap_info_struct *si,
 			start_block <<= PAGE_SHIFT - 9;
 			nr_blocks <<= PAGE_SHIFT - 9;
 			if (blkdev_issue_discard(si->bdev, start_block,
-				    nr_blocks, GFP_NOIO, BLKDEV_IFL_WAIT |
-							BLKDEV_IFL_BARRIER))
+				    nr_blocks, GFP_NOIO, BLKDEV_IFL_WAIT))
 				break;
 		}