linux-kernel - [PATCH v2] scsi: target: Save a few cycles in transport_lookup_[cmd|tmr]

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Message-Id: <03705222390bfa3b48ad7658f693fc0fc030b3ae.1660596679.git.christophe.jaillet@wanadoo.fr>
Date:   Mon, 15 Aug 2022 22:52:24 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     michael.christie@...cle.com,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org
Subject: [PATCH v2] scsi: target: Save a few cycles in transport_lookup_[cmd|tmr]_lun()

Use percpu_ref_tryget_live_rcu() instead of percpu_ref_tryget_live() to
save a few cycles when it is known that the rcu lock is already
taken/released.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
Change in v2:
  * sync with -next

v1:
  * https://lore.kernel.org/all/e4a21bc607c39935cb98d4825cd63ba349820550.1635974637.git.christophe.jaillet@wanadoo.fr/
---
 drivers/target/target_core_device.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index b7f16ee8aa0e..76c6613a1da7 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -77,7 +77,7 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd)
 
 		se_lun = deve->se_lun;
 
-		if (!percpu_ref_tryget_live(&se_lun->lun_ref)) {
+		if (!percpu_ref_tryget_live_rcu(&se_lun->lun_ref)) {
 			se_lun = NULL;
 			goto out_unlock;
 		}
@@ -154,7 +154,7 @@ int transport_lookup_tmr_lun(struct se_cmd *se_cmd)
 	if (deve) {
 		se_lun = deve->se_lun;
 
-		if (!percpu_ref_tryget_live(&se_lun->lun_ref)) {
+		if (!percpu_ref_tryget_live_rcu(&se_lun->lun_ref)) {
 			se_lun = NULL;
 			goto out_unlock;
 		}
-- 
2.34.1