| Message ID | 20191021224259.209542-2-bvanassche@acm.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Reduce the amount of memory required for request queues | expand |
On Mon, Oct 21, 2019 at 03:42:56PM -0700, Bart Van Assche wrote: > Since the blk_mq_{,un}freeze_queue() calls in __blk_mq_update_nr_hw_queues() > already serialize __blk_mq_update_nr_hw_queues() against > blk_mq_queue_tag_busy_iter(), the synchronize_rcu() call in > __blk_mq_update_nr_hw_queues() is not necessary. Hence remove it. > > Note: the synchronize_rcu() call in __blk_mq_update_nr_hw_queues() was > introduced by commit f5bbbbe4d635 ("blk-mq: sync the update nr_hw_queues with > blk_mq_queue_tag_busy_iter"). Commit 530ca2c9bd69 ("blk-mq: Allow blocking > queue tag iter callbacks") removed the rcu_read_{,un}lock() calls that > correspond to the synchronize_rcu() call in __blk_mq_update_nr_hw_queues(). > > Cc: Christoph Hellwig <hch@infradead.org> > Cc: Ming Lei <ming.lei@redhat.com> > Cc: Hannes Reinecke <hare@suse.com> > Cc: Johannes Thumshirn <jthumshirn@suse.de> > Signed-off-by: Bart Van Assche <bvanassche@acm.org> > --- > block/blk-mq.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 8538dc415499..7528678ef41f 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -3242,10 +3242,6 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, > > 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(); > /* > * Switch IO scheduler to 'none', cleaning up the data associated > * with the previous scheduler. We will switch back once we are done > -- > 2.23.0.866.gb869b98d4c-goog > Reviewed-by: Ming Lei <ming.lei@redhat.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c index 8538dc415499..7528678ef41f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -3242,10 +3242,6 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, 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(); /* * Switch IO scheduler to 'none', cleaning up the data associated * with the previous scheduler. We will switch back once we are done
Since the blk_mq_{,un}freeze_queue() calls in __blk_mq_update_nr_hw_queues() already serialize __blk_mq_update_nr_hw_queues() against blk_mq_queue_tag_busy_iter(), the synchronize_rcu() call in __blk_mq_update_nr_hw_queues() is not necessary. Hence remove it. Note: the synchronize_rcu() call in __blk_mq_update_nr_hw_queues() was introduced by commit f5bbbbe4d635 ("blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter"). Commit 530ca2c9bd69 ("blk-mq: Allow blocking queue tag iter callbacks") removed the rcu_read_{,un}lock() calls that correspond to the synchronize_rcu() call in __blk_mq_update_nr_hw_queues(). Cc: Christoph Hellwig <hch@infradead.org> Cc: Ming Lei <ming.lei@redhat.com> Cc: Hannes Reinecke <hare@suse.com> Cc: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Bart Van Assche <bvanassche@acm.org> --- block/blk-mq.c | 4 ---- 1 file changed, 4 deletions(-)