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>
diff --git a/block/elevator.c b/block/elevator.c
index 88318c3..e8a90fe 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -1070,7 +1070,7 @@
*/
spin_lock_irq(q->queue_lock);
- set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+ queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
elv_drain_elevator(q);
@@ -1104,7 +1104,10 @@
* finally exit old elevator and turn off BYPASS.
*/
elevator_exit(old_elevator);
- clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+ spin_lock_irq(q->queue_lock);
+ queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
+ spin_unlock_irq(q->queue_lock);
+
return 1;
fail_register:
@@ -1115,7 +1118,11 @@
elevator_exit(e);
q->elevator = old_elevator;
elv_register_queue(q);
- clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+
+ spin_lock_irq(q->queue_lock);
+ queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
+ spin_unlock_irq(q->queue_lock);
+
return 0;
}