linux-kernel - Re: [PATCH] vhost/scsi: drop unnecessary smp_mb__after

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Date:   Wed, 17 Apr 2019 13:57:18 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Stefan Hajnoczi <stefanha@...hat.com>, kvm@...r.kernel.org
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Nicholas Bellinger <nab@...ux-iscsi.org>,
        Andrea Parri <andrea.parri@...rulasolutions.com>
Subject: Re: [PATCH] vhost/scsi: drop unnecessary smp_mb__after_atomic()


On 2019/4/16 下午6:47, Stefan Hajnoczi wrote:
> The vhost_scsi.ko code used several atomic variables at one point.
> Later they were dropped or converted to regular ints protected by a
> mutex.
>
> The commit that made these changes left an unused smp_mb__after_atomic()
> in vhost_scsi_set_endpoint().  It was previously used after incrementing
> vhost_scsi->vhost_ref_cnt but this field has been dropped:
>
>    -     atomic_inc(&vs->vhost_ref_cnt);
>          smp_mb__after_atomic_inc();
>
> Reported-by: Andrea Parri <andrea.parri@...rulasolutions.com>
> Fixes: 101998f6fcd680 ("tcm_vhost: Post-merge review changes requested by MST")
> Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
> ---
>   drivers/vhost/scsi.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index 618fb6461017..c090d177bd75 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -1443,7 +1443,6 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
>   			tpg->tv_tpg_vhost_count++;
>   			tpg->vhost_scsi = vs;
>   			vs_tpg[tpg->tport_tpgt] = tpg;
> -			smp_mb__after_atomic();
>   			match = true;
>   		}
>   		mutex_unlock(&tpg->tv_tpg_mutex);


Looks like Paolo has sent an identical patch before this one.

Thanks