[dm-devel] [PATCH] dm-kcopyd: avoid useless atomic operations

[Mikulas Patocka]

The functions set_bit and clear_bit are atomic. We don't need atomicity
when making flags for dm-kcopyd. So, change them to direct manipulation of
the flags.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>

Index: linux-2.6/drivers/md/dm-kcopyd.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-kcopyd.c
+++ linux-2.6/drivers/md/dm-kcopyd.c
@@ -812,7 +812,7 @@ void dm_kcopyd_copy(struct dm_kcopyd_cli
 	if (!test_bit(DM_KCOPYD_WRITE_SEQ, &job->flags)) {
 		for (i = 0; i < job->num_dests; i++) {
 			if (bdev_zoned_model(dests[i].bdev) == BLK_ZONED_HM) {
-				set_bit(DM_KCOPYD_WRITE_SEQ, &job->flags);
+				job->flags |= 1UL << DM_KCOPYD_WRITE_SEQ;
 				break;
 			}
 		}
@@ -823,7 +823,7 @@ void dm_kcopyd_copy(struct dm_kcopyd_cli
 	 */
 	if (test_bit(DM_KCOPYD_WRITE_SEQ, &job->flags) &&
 	    test_bit(DM_KCOPYD_IGNORE_ERROR, &job->flags))
-		clear_bit(DM_KCOPYD_IGNORE_ERROR, &job->flags);
+		job->flags &= ~(1UL << DM_KCOPYD_IGNORE_ERROR);
 
 	if (from) {
 		job->source = *from;
Index: linux-2.6/drivers/md/dm-raid1.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-raid1.c
+++ linux-2.6/drivers/md/dm-raid1.c
@@ -364,7 +364,7 @@ static void recover(struct mirror_set *m
 
 	/* hand to kcopyd */
 	if (!errors_handled(ms))
-		set_bit(DM_KCOPYD_IGNORE_ERROR, &flags);
+		flags |= 1UL << DM_KCOPYD_IGNORE_ERROR;
 
 	dm_kcopyd_copy(ms->kcopyd_client, &from, ms->nr_mirrors - 1, to,
 		       flags, recovery_complete, reg);
Index: linux-2.6/drivers/md/dm-zoned-reclaim.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-zoned-reclaim.c
+++ linux-2.6/drivers/md/dm-zoned-reclaim.c
@@ -134,7 +134,7 @@ static int dmz_reclaim_copy(struct dmz_r
 	dst_zone_block = dmz_start_block(zmd, dst_zone);
 
 	if (dmz_is_seq(dst_zone))
-		set_bit(DM_KCOPYD_WRITE_SEQ, &flags);
+		flags |= 1UL << DM_KCOPYD_WRITE_SEQ;
 
 	while (block < end_block) {
 		if (src_zone->dev->flags & DMZ_BDEV_DYING)