[dm-devel] [PATCH 2/5] dm-mpath: return DM_MAPIO_REQUEUE in case of rq allocation failure

[Bart Van Assche]

On Sat, 2017-09-16 at 00:44 +0800, Ming Lei wrote:
> blk-mq will rerun queue via RESTART after one request is completion,
> so not necessary to wait random time for requeuing, it should trust
> blk-mq to do it.
> 
> Signed-off-by: Ming Lei <ming.lei at redhat.com>
> ---
>  drivers/md/dm-mpath.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
> index 96aedaac2c64..f5a1088a6e79 100644
> --- a/drivers/md/dm-mpath.c
> +++ b/drivers/md/dm-mpath.c
> @@ -505,7 +505,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
>  			atomic_inc(&m->pg_init_in_progress);
>  			activate_or_offline_path(pgpath);
>  		}
> -		return DM_MAPIO_DELAY_REQUEUE;
> +		return DM_MAPIO_REQUEUE;
>  	}
>  	clone->bio = clone->biotail = NULL;
>  	clone->rq_disk = bdev->bd_disk;

So you are reverting the patch below? Thank you very much.

commit 1c23484c355ec360ca2f37914f8a4802c6baeead
Author: Bart Van Assche <bart.vanassche at wdc.com>
Date:   Wed Aug 9 11:32:12 2017 -0700

    dm mpath: do not lock up a CPU with requeuing activity
    
    When using the block layer in single queue mode, get_request()
    returns ERR_PTR(-EAGAIN) if the queue is dying and the REQ_NOWAIT
    flag has been passed to get_request(). Avoid that the kernel
    reports soft lockup complaints in this case due to continuous
    requeuing activity.
    
    Fixes: 7083abbbf ("dm mpath: avoid that path removal can trigger an infinite loop")
    Cc: stable at vger.kernel.org
    Signed-off-by: Bart Van Assche <bart.vanassche at wdc.com>
    Tested-by: Laurence Oberman <loberman at redhat.com>
    Reviewed-by: Christoph Hellwig <hch at lst.de>
    Signed-off-by: Mike Snitzer <snitzer at redhat.com>