block: make queue flags non-atomic

We can save some atomic ops in the IO path, if we clearly define
the rules of how to modify the queue flags.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 7 insertions, 3 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 51be53344214..73326e7c54bf 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -873,10 +873,13 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q)
         q->max_hw_sectors = t->limits.max_hw_sectors;
         q->seg_boundary_mask = t->limits.seg_boundary_mask;
         q->bounce_pfn = t->limits.bounce_pfn;
+        /* XXX: the below will probably go bug. must ensure there can be no
+         * concurrency on queue_flags, and use the unlocked versions...
+         */
         if (t->limits.no_cluster)
-                q->queue_flags &= ~(1 << QUEUE_FLAG_CLUSTER);
+                queue_flag_clear(QUEUE_FLAG_CLUSTER, q);
         else
-                q->queue_flags |= (1 << QUEUE_FLAG_CLUSTER);
+                queue_flag_set(QUEUE_FLAG_CLUSTER, q);
 
 }
 
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 87620b705bee..acd716b657b8 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -282,7 +282,8 @@ static mddev_t * mddev_find(dev_t unit)
                 kfree(new);
                 return NULL;
         }
-        set_bit(QUEUE_FLAG_CLUSTER, &new->queue->queue_flags);
+        /* Can be unlocked because the queue is new: no concurrency */
+        queue_flag_set_unlocked(QUEUE_FLAG_CLUSTER, new->queue);
 
         blk_queue_make_request(new->queue, md_fail_request);