blk-mq: move blk_mq_update_nr_hw_queues synchronize_rcu call

This fixes the
4.9 backport commit f530afb974c2e82047bd6220303a2dbe30eff304
which was
upstream commit f5bbbbe4d63577026f908a809f22f5fd5a90ea1f.

The upstream commit added a call to synchronize_rcu to
_blk_mq_update_nr_hw_queues, just after freezing queues.

In the backport this landed (in blk_mq_update_nr_hw_queues instead),
just after unfreezeing queues.

This commit moves the call to its intended place.

Fixes: f530afb974c2 ("blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter")
Signed-off-by: Giuliano Procida <gprocida@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 58be2ea..e0ed731 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2331,6 +2331,10 @@ void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
 
        list_for_each_entry(q, &set->tag_list, tag_set_list)
                blk_mq_freeze_queue(q);
+       /*
+        * Sync with blk_mq_queue_tag_busy_iter.
+        */
+       synchronize_rcu();
 
        set->nr_hw_queues = nr_hw_queues;
        list_for_each_entry(q, &set->tag_list, tag_set_list) {
@@ -2346,10 +2350,6 @@ void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
 
        list_for_each_entry(q, &set->tag_list, tag_set_list)
                blk_mq_unfreeze_queue(q);
-       /*
-        * Sync with blk_mq_queue_tag_busy_iter.
-        */
-       synchronize_rcu();
 }
 EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);