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| author | Ming Lei <ming.lei@redhat.com> | 2019-08-27 19:01:45 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-08-27 10:40:20 -0600 |
| commit | c48dac137a62a5d6fa1ef3fa445cbd9c43655a76 (patch) | |
| tree | 0cbc830e7a790655bb0d012ca555f24852765fb3 /block/elevator.c | |
| parent | 9685b2270211628e27ea7880a02b52efd4524099 (diff) | |
| download | linux-c48dac137a62a5d6fa1ef3fa445cbd9c43655a76.tar.gz linux-c48dac137a62a5d6fa1ef3fa445cbd9c43655a76.tar.bz2 linux-c48dac137a62a5d6fa1ef3fa445cbd9c43655a76.zip | |
block: don't hold q->sysfs_lock in elevator_init_mq
The original comment says:
q->sysfs_lock must be held to provide mutual exclusion between
elevator_switch() and here.
Which is simply wrong. elevator_init_mq() is only called from
blk_mq_init_allocated_queue, which is always called before the request
queue is registered via blk_register_queue(), for dm-rq or normal rq
based driver. However, queue's kobject is only exposed and added to sysfs
in blk_register_queue(). So there isn't such race between elevator_switch()
and elevator_init_mq().
So avoid to hold q->sysfs_lock in elevator_init_mq().
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/elevator.c')
| -rw-r--r-- | block/elevator.c | 14 |
1 files changed, 5 insertions, 9 deletions
diff --git a/block/elevator.c b/block/elevator.c index 2f17d66d0e61..33c15fb54ed1 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -607,23 +607,19 @@ int elevator_init_mq(struct request_queue *q) if (q->nr_hw_queues != 1) return 0; - /* - * q->sysfs_lock must be held to provide mutual exclusion between - * elevator_switch() and here. - */ - mutex_lock(&q->sysfs_lock); + WARN_ON_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags)); + if (unlikely(q->elevator)) - goto out_unlock; + goto out; e = elevator_get(q, "mq-deadline", false); if (!e) - goto out_unlock; + goto out; err = blk_mq_init_sched(q, e); if (err) elevator_put(e); -out_unlock: - mutex_unlock(&q->sysfs_lock); +out: return err; } |