swap: do not send discards as barriers

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

This fixes the worst of the terrible slowdown in swap allocation for
hibernation, reported on 2.6.35 by Nigel Cunningham; but does not entirely
eliminate that regression.

[[email protected]: superflous newlines removed]
Signed-off-by: Christoph Hellwig <[email protected]>
Tested-by: Nigel Cunningham <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>
Signed-off-by: Hugh Dickins <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: "Martin K. Petersen" <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/swapfile.c b/mm/swapfile.c
index ed5151079f59437bf54f540d71336ec18a8d76d0..1894dead0b5802b10cf1d45fb28a765744b792e6 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -139,8 +139,7 @@ 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();
@@ -151,8 +150,7 @@ 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;
 
@@ -191,8 +189,7 @@ 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;
                }