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

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Message-Id: <20190416104748.26942-1-stefanha@redhat.com>
Date:   Tue, 16 Apr 2019 11:47:48 +0100
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     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>,
        Jason Wang <jasowang@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>
Subject: [PATCH] vhost/scsi: drop unnecessary smp_mb__after_atomic()

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);
-- 
2.20.1