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 --- block/blk-mq.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c index 58be2eaa5aaa..e0ed7317e98c 100644 --- 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);