linux-kernel - [PATCH] lightnvm: pblk: avoid ref warning on cache creation

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Message-Id: <1542894410-14047-2-git-send-email-javier@cnexlabs.com>
Date:   Thu, 22 Nov 2018 14:46:50 +0100
From:   "Javier González" <javier@...igon.com>
To:     mb@...htnvm.io
Cc:     hans.holmberg@...xlabs.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Javier González <javier@...xlabs.com>
Subject: [PATCH] lightnvm: pblk: avoid ref warning on cache creation

The current kref implementation around pblk global caches triggers a
false positive on refcount_inc_checked() (when called) as the kref is
initialized to 0. Instead of usint kref_inc() on a 0 reference, which is
in principle correct, use kref_init() to avoid the check. This is also
more explicit about what actually happens on cache creation.

In the process, do a small refactoring to use kref helpers.

Signed-off-by: Javier González <javier@...xlabs.com>
---
 drivers/lightnvm/pblk-init.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
index 13822594647c..e225bd60cbb4 100644
--- a/drivers/lightnvm/pblk-init.c
+++ b/drivers/lightnvm/pblk-init.c
@@ -350,23 +350,19 @@ static int pblk_create_global_caches(void)
 
 static int pblk_get_global_caches(void)
 {
-	int ret;
+	int ret = 0;
 
 	mutex_lock(&pblk_caches.mutex);
 
-	if (kref_read(&pblk_caches.kref) > 0) {
-		kref_get(&pblk_caches.kref);
-		mutex_unlock(&pblk_caches.mutex);
-		return 0;
-	}
+	if (kref_get_unless_zero(&pblk_caches.kref))
+		goto out;
 
 	ret = pblk_create_global_caches();
-
 	if (!ret)
-		kref_get(&pblk_caches.kref);
+		kref_init(&pblk_caches.kref);
 
+out:
 	mutex_unlock(&pblk_caches.mutex);
-
 	return ret;
 }
 
-- 
2.7.4