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

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Message-Id: <e4a21bc607c39935cb98d4825cd63ba349820550.1635974637.git.christophe.jaillet@wanadoo.fr>
Date:   Wed,  3 Nov 2021 22:24:46 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     martin.petersen@...cle.com
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] 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>
---
 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 44bb380e7390..bfd5d5606522 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 = rcu_dereference(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 = rcu_dereference(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;
 		}
-- 
2.30.2