diff options
| author | Yu Kuai <yukuai3@huawei.com> | 2025-07-29 10:32:29 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2025-07-29 06:26:34 -0600 |
| commit | 5421681bc3ef13476bd9443379cd69381e8760fa (patch) | |
| tree | c93edc86cba65073358ef647a77b8066cb820786 /block/blk-ioc.c | |
| parent | 1da67b5b1754713b8ea0c3dd847e04790cffd91f (diff) | |
blk-ioc: don't hold queue_lock for ioc_lookup_icq()
Currently issue io can grab queue_lock three times from bfq_bio_merge(),
bfq_limit_depth() and bfq_prepare_request(), the queue_lock is not
necessary if icq is already created because both queue and ioc can't be
freed before io issuing is done, hence remove the unnecessary queue_lock
and use rcu to protect radix tree lookup.
Noted this is also a prep patch to support request batch dispatching[1].
[1] https://lore.kernel.org/all/20250722072431.610354-1-yukuai1@huaweicloud.com/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20250729023229.2944898-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-ioc.c')
| -rw-r--r-- | block/blk-ioc.c | 16 |
1 files changed, 6 insertions, 10 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c index ce82770c72ab..9fda3906e5f5 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -308,24 +308,23 @@ int __copy_io(unsigned long clone_flags, struct task_struct *tsk) #ifdef CONFIG_BLK_ICQ /** - * ioc_lookup_icq - lookup io_cq from ioc + * ioc_lookup_icq - lookup io_cq from ioc in io issue path * @q: the associated request_queue * * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called - * with @q->queue_lock held. + * from io issue path, either return NULL if current issue io to @q for the + * first time, or return a valid icq. */ struct io_cq *ioc_lookup_icq(struct request_queue *q) { struct io_context *ioc = current->io_context; struct io_cq *icq; - lockdep_assert_held(&q->queue_lock); - /* * icq's are indexed from @ioc using radix tree and hint pointer, - * both of which are protected with RCU. All removals are done - * holding both q and ioc locks, and we're holding q lock - if we - * find a icq which points to us, it's guaranteed to be valid. + * both of which are protected with RCU, io issue path ensures that + * both request_queue and current task are valid, the found icq + * is guaranteed to be valid until the io is done. */ rcu_read_lock(); icq = rcu_dereference(ioc->icq_hint); @@ -419,10 +418,7 @@ struct io_cq *ioc_find_get_icq(struct request_queue *q) task_unlock(current); } else { get_io_context(ioc); - - spin_lock_irq(&q->queue_lock); icq = ioc_lookup_icq(q); - spin_unlock_irq(&q->queue_lock); } if (!icq) { |