block: drop unnecessary blk_get/put_queue() in scsi_cmd_ioctl() and blk_get_tg() (315fceee) · Commits · 戴 / test

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:

Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

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);

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