Re: [PATCH] ublk_drv: fix request queue leak

[Ming Lei <ming.lei@redhat.com>]

On Thu, Jul 14, 2022 at 09:26:25PM +0800, Ming Lei wrote:
> On Thu, Jul 14, 2022 at 06:23:12AM -0700, Christoph Hellwig wrote:
> > On Thu, Jul 14, 2022 at 09:20:24PM +0800, Ming Lei wrote:
> > > The problem is that you moved part of blk_cleanup_queue() into
> > > del_gendisk().
> > > 
> > > Here, the issue Jens reproduced is that we don't add disk yet, so won't
> > > call del_gendisk(). The queue & disk is allocated & initialized correctly.
> > > 
> > > Then how to do the part done by original blk_cleanup_queue() without calling
> > > blk_mq_destroy_queue()?
> > 
> > What do you need to clean up?  put_disk is supposed to eventually
> > clean up everything allocated by blk_alloc_disk through disk_release.
> > If it fails to cleanup anything that is a bug we need to fix in the core
> > as it will affect all drivers.
> 
> The part to be cleaned up is nothing to do with disk:
> 
>                 if (queue_is_mq(q))
>                         blk_mq_exit_queue(q);
> 
> ->exit_hctx() is called in blk_mq_exit_queue().
> 
> Without calling blk_mq_destroy_queue, I don't see other way to address
> this issue, or suggestions?

It is actually one big problem of 6f8191fdf41d ("block: simplify disk shutdown")
since blk_put_queue() can't do what blk_cleanup_queue() did.

Anywhere using blk_put_queue() to release blk-mq queue before adding
disk has the same issue.


Thanks,
Ming