block: use trylock to avoid lockdep circular dependency in sysfs

block: use trylock to avoid lockdep circular dependency in sysfs

Use trylock instead of blocking lock acquisition for update_nr_hwq_lock
in queue_requests_store() and elv_iosched_store() to avoid circular lock
dependency with kernfs active reference during concurrent disk deletion:

  update_nr_hwq_lock -> kn->active (via del_gendisk -> kobject_del)
  kn->active -> update_nr_hwq_lock (via sysfs write path)

Return -EBUSY when the lock is not immediately available.

Reported-and-tested-by: Yi Zhang <yi.zhang@redhat.com>
Closes: https://lore.kernel.org/linux-block/CAHj4cs-em-4acsHabMdT=jJhXkCzjnprD-aQH1OgrZo4nTnmMw@mail.gmail.com/
Fixes: 626ff4f8ebcb ("blk-mq: convert to serialize updating nr_requests with update_nr_hwq_lock")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>