linux-kernel - [PATCH v1] nvme: only call synhronize

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Date:   Wed,  1 Sep 2021 11:25:24 +0200
From:   Daniel Wagner <dwagner@...e.de>
To:     linux-nvme@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, Daniel Wagner <dwagner@...e.de>
Subject: [PATCH v1] nvme: only call synhronize_srcu when clearing current path

The function nmve_mpath_clear_current_path returns true if the current
path has changed. In this case we have to wait for all concurrent
submissions to finish. But if we didn't change the current path, there
is no point in waiting for another RCU period to finish.

Signed-off-by: Daniel Wagner <dwagner@...e.de>
---
 drivers/nvme/host/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index d3d5cc947525..5b3c74fa89bd 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3814,8 +3814,8 @@ static void nvme_ns_remove(struct nvme_ns *ns)
 	mutex_unlock(&ns->ctrl->subsys->lock);
 
 	synchronize_rcu(); /* guarantee not available in head->list */
-	nvme_mpath_clear_current_path(ns);
-	synchronize_srcu(&ns->head->srcu); /* wait for concurrent submissions */
+	if (nvme_mpath_clear_current_path(ns))
+		synchronize_srcu(&ns->head->srcu); /* wait for concurrent submissions */
 
 	if (ns->disk->flags & GENHD_FL_UP) {
 		if (!nvme_ns_head_multipath(ns->head))
-- 
2.29.2