Re: [PATCH 3/3] dm: don't stop request queue after the dm device is suspended

[Mike Snitzer <snitzer@redhat.com>]

On Thu, Oct 21 2021 at 10:59P -0400,
Ming Lei <ming.lei@redhat.com> wrote:

> For fixing queue quiesce race between driver and block layer(elevator
> switch, update nr_requests, ...), we need to support concurrent quiesce
> and unquiesce, which requires the two call to be balanced.
> 
> __bind() is only called from dm_swap_table() in which dm device has been
> suspended already, so not necessary to stop queue again. With this way,
> request queue quiesce and unquiesce can be balanced.
> 
> Reported-by: Yi Zhang <yi.zhang@redhat.com>
> Fixes: e70feb8b3e68 ("blk-mq: support concurrent queue quiesce/unquiesce")
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/md/dm.c | 10 ----------
>  1 file changed, 10 deletions(-)
> 
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 7870e6460633..727282d79b26 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1927,16 +1927,6 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
>  
>  	dm_table_event_callback(t, event_callback, md);
>  
> -	/*
> -	 * The queue hasn't been stopped yet, if the old table type wasn't
> -	 * for request-based during suspension.  So stop it to prevent
> -	 * I/O mapping before resume.
> -	 * This must be done before setting the queue restrictions,
> -	 * because request-based dm may be run just after the setting.
> -	 */
> -	if (request_based)
> -		dm_stop_queue(q);
> -
>  	if (request_based) {
>  		/*
>  		 * Leverage the fact that request-based DM targets are
> -- 
> 2.31.1
> 

I think this is fine given your previous commit (b4459b11e8f dm rq:
don't queue request to blk-mq during DM suspend).

Acked-by: Mike Snitzer <snitzer@redhat.com>

Jens: given this series fixes a 5.16 regression in srp test, please
pick it up for 5.16-rc

Thanks,
Mike