Re: [PATCH] ublk_drv: fix request queue leak

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

On Thu, Jul 14, 2022 at 07:00:59AM -0600, Jens Axboe wrote:
> On 7/14/22 4:32 AM, Ming Lei wrote:
> > Call blk_cleanup_queue() in release code path for fixing request
> > queue leak.
> > 
> > Also for-5.20/block has cleaned up blk_cleanup_queue(), which is
> > basically merged to del_gendisk() if blk_mq_alloc_disk() is used
> > for allocating disk and queue.
> > 
> > However, ublk may not add disk in case of starting device failure, then
> > del_gendisk() won't be called when removing ublk device, so blk_mq_exit_queue
> > will not be callsed, and it can be bit hard to deal with this kind of
> > merge conflict.
> > 
> > Turns out ublk's queue/disk use model is very similar with scsi, so switch
> > to scsi's model by allocating disk and queue independently, then it can be
> > quite easy to handle v5.20 merge conflict by replacing blk_cleanup_queue
> > with blk_mq_destroy_queue.
> 
> Tried this with the below incremental added to make it compile with
> the core block changes too, and it still fails for me:
> 
> [   22.488660] WARNING: CPU: 0 PID: 11 at block/blk-mq.c:3880 blk_mq_release+0xa4/0xf0
> [   22.490797] Modules linked in:
> [   22.491762] CPU: 0 PID: 11 Comm: kworker/0:1 Not tainted 5.19.0-rc6-00322-g42ed61fe42f3-dirty #1609
> [   22.494659] Hardware name: linux,dummy-virt (DT)
> [   22.496171] Workqueue: events blkg_free_workfn
> [   22.497652] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   22.499965] pc : blk_mq_release+0xa4/0xf0
> [   22.501386] lr : blk_mq_release+0x44/0xf0
> [   22.502748] sp : ffff80000af73cb0
> [   22.503880] x29: ffff80000af73cb0 x28: 0000000000000000 x27: 0000000000000000
> [   22.506263] x26: 0000000000000000 x25: ffff00001fe47b05 x24: 0000000000000000
> [   22.508655] x23: ffff0000052b6cb8 x22: ffff0000031e1c38 x21: 0000000000000000
> [   22.511035] x20: ffff0000031e1cf0 x19: ffff0000031e1bf0 x18: 0000000000000000
> [   22.513427] x17: 0000000000000000 x16: 0000000000000000 x15: 0000ffffa8000b80
> [   22.515814] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000001
> [   22.518209] x11: ffff80000945b7e8 x10: 0000000000006cb9 x9 : 00000000ffffffff
> [   22.520600] x8 : ffff800008fb5000 x7 : ffff80000860cf28 x6 : 0000000000000000
> [   22.522987] x5 : 0000000000000000 x4 : 0000000000000028 x3 : ffff80000af73c14
> [   22.525363] x2 : ffff0000071ccaa8 x1 : ffff0000071ccaa8 x0 : ffff0000071cc800
> [   22.527624] Call trace:
> [   22.528473]  blk_mq_release+0xa4/0xf0
> [   22.529724]  blk_release_queue+0x58/0xa0
> [   22.530946]  kobject_put+0x84/0xe0
> [   22.531821]  blk_put_queue+0x10/0x18
> [   22.532716]  blkg_free_workfn+0x58/0x84
> [   22.533681]  process_one_work+0x2ac/0x438
> [   22.534872]  worker_thread+0x1cc/0x264
> [   22.535829]  kthread+0xd0/0xe0
> [   22.536598]  ret_from_fork+0x10/0x20
> 
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index eeeac43e1dc1..d818da818c00 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -1078,7 +1078,7 @@ static void ublk_cdev_rel(struct device *dev)
>  {
>  	struct ublk_device *ub = container_of(dev, struct ublk_device, cdev_dev);
>  
> -	blk_cleanup_queue(ub->ub_queue);
> +	blk_put_queue(ub->ub_queue);

I guess you run test on for-next, and it should work by just replacing
two blk_cleanup_queue with blk_mq_destroy_queue().


Thanks,
Ming