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authorMing Lei <ming.lei@redhat.com>2019-08-27 14:01:45 +0300
committerJens Axboe <axboe@kernel.dk>2019-08-27 19:40:20 +0300
commitc48dac137a62a5d6fa1ef3fa445cbd9c43655a76 (patch)
tree0cbc830e7a790655bb0d012ca555f24852765fb3 /block/elevator.c
parent9685b2270211628e27ea7880a02b52efd4524099 (diff)
downloadlinux-c48dac137a62a5d6fa1ef3fa445cbd9c43655a76.tar.xz
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.c14
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;
}