Linux Virtualization - Apr 2019 - [PATCH] vhost-scsi: remove incorrect memory barrier

At this point, vs_tpg is not public at all; tv_tpg_vhost_count
is accessed under tpg->tv_tpg_mutex; tpg->vhost_scsi is
accessed under vhost_scsi_mutex.  Therefor there are no atomic
operations involved at all here, just remove the barrier.

Reported-by: Andrea Parri <andrea.parri at amarulasolutions.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.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 @@ static void vhost_scsi_flush(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);
-- 
1.8.3.1

On 2019/4/16 ??4:56, Paolo Bonzini wrote:
> At this point, vs_tpg is not public at all; tv_tpg_vhost_count
> is accessed under tpg->tv_tpg_mutex; tpg->vhost_scsi is
> accessed under vhost_scsi_mutex.  Therefor there are no atomic
> operations involved at all here, just remove the barrier.
>
> Reported-by: Andrea Parri <andrea.parri at amarulasolutions.com>
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.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 @@ static void vhost_scsi_flush(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);

Acked-by: Jason Wang <jasowang at redhat.com>