block: don't call freeze queue in elevator_switch() and elevator_disable()

Both elevator_switch() and elevator_disable() are only called from the
two code paths, in which queue is guaranteed to be frozen.

So don't call freeze queue in the two functions, also add asserts for
queue freeze.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20250505141805.2751237-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/elevator.c b/block/elevator.c
index b4d0802..5051a98 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -615,12 +615,11 @@ void elevator_init_mq(struct request_queue *q)
  */
 int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 {
-       unsigned int memflags;
        int ret;
 
+       WARN_ON_ONCE(q->mq_freeze_depth == 0);
        lockdep_assert_held(&q->elevator_lock);
 
-       memflags = blk_mq_freeze_queue(q);
        blk_mq_quiesce_queue(q);
 
        if (q->elevator) {
@@ -641,7 +640,6 @@ int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 
 out_unfreeze:
        blk_mq_unquiesce_queue(q);
-       blk_mq_unfreeze_queue(q, memflags);
 
        if (ret) {
                pr_warn("elv: switch to \"%s\" failed, falling back to \"none\"\n",
@@ -653,11 +651,9 @@ out_unfreeze:
 
 void elevator_disable(struct request_queue *q)
 {
-       unsigned int memflags;
-
+       WARN_ON_ONCE(q->mq_freeze_depth == 0);
        lockdep_assert_held(&q->elevator_lock);
 
-       memflags = blk_mq_freeze_queue(q);
        blk_mq_quiesce_queue(q);
 
        elv_unregister_queue(q);
@@ -668,7 +664,6 @@ void elevator_disable(struct request_queue *q)
        blk_add_trace_msg(q, "elv switch: none");
 
        blk_mq_unquiesce_queue(q);
-       blk_mq_unfreeze_queue(q, memflags);
 }
 
 /*