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Commit 315fceee authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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block: drop unnecessary blk_get/put_queue() in scsi_cmd_ioctl() and blk_get_tg() 



blk_get/put_queue() in scsi_cmd_ioctl() and throtl_get_tg() are
completely bogus.  The caller must have a reference to the queue on
entry and taking an extra reference doesn't change anything.

For scsi_cmd_ioctl(), the only effect is that it ends up checking
QUEUE_FLAG_DEAD on entry; however, this is bogus as queue can die
right after blk_get_queue().  Dead queue should be and is handled in
request issue path (it's somewhat broken now but that's a separate
problem and doesn't affect this one much).

throtl_get_tg() incorrectly assumes that q is rcu freed.  Also, it
doesn't check return value of blk_get_queue().  If the queue is
already dead, it ends up doing an extra put.

Drop them.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 75eb6c37

block/blk-throttle.c

+1 −7
Original line number Diff line number Diff line
@@ -324,12 +324,8 @@ static struct throtl_grp * throtl_get_tg(struct throtl_data *td) 
	/*

	 * Need to allocate a group. Allocation of group also needs allocation

	 * of per cpu stats which in-turn takes a mutex() and can block. Hence

	 * we need to drop rcu lock and queue_lock before we call alloc

	 *

	 * Take the request queue reference to make sure queue does not

	 * go away once we return from allocation.

	 * we need to drop rcu lock and queue_lock before we call alloc.

	 */

	blk_get_queue(q);

	rcu_read_unlock();

	spin_unlock_irq(q->queue_lock);
@@ -339,13 +335,11 @@ static struct throtl_grp * throtl_get_tg(struct throtl_data *td) 
	 * dead

	 */

	if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {

		blk_put_queue(q);

		if (tg)

			kfree(tg);



		return ERR_PTR(-ENODEV);

	}

	blk_put_queue(q);



	/* Group allocated and queue is still alive. take the lock */

	spin_lock_irq(q->queue_lock);

block/scsi_ioctl.c

+1 −2
Original line number Diff line number Diff line
@@ -565,7 +565,7 @@ int scsi_cmd_ioctl(struct request_queue *q, struct gendisk *bd_disk, fmode_t mod 
{

	int err;



	if (!q || blk_get_queue(q))

	if (!q)

		return -ENXIO;



	switch (cmd) {
@@ -686,7 +686,6 @@ int scsi_cmd_ioctl(struct request_queue *q, struct gendisk *bd_disk, fmode_t mod 
			err = -ENOTTY;

	}



	blk_put_queue(q);

	return err;

}

EXPORT_SYMBOL(scsi_cmd_ioctl);