linux-kernel - [PATCH] kernfs: fix barrier usage in __kernfs_new

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Message-Id: <1555417031-27356-1-git-send-email-andrea.parri@amarulasolutions.com>
Date:   Tue, 16 Apr 2019 14:17:11 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tejun Heo <tj@...nel.org>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] kernfs: fix barrier usage in __kernfs_new_node()

smp_mb__before_atomic() can not be applied to atomic_set().  Remove the
barrier and rely on RELEASE synchronization.

Fixes: ba16b2846a8c6 ("kernfs: add an API to get kernfs node from inode number")
Cc: stable@...r.kernel.org
Signed-off-by: Andrea Parri <andrea.parri@...rulasolutions.com>
---
 fs/kernfs/dir.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index b84d635567d38..1e7a74b8e0647 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -650,11 +650,10 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 	kn->id.generation = gen;
 
 	/*
-	 * set ino first. This barrier is paired with atomic_inc_not_zero in
+	 * set ino first. This RELEASE is paired with atomic_inc_not_zero in
 	 * kernfs_find_and_get_node_by_ino
 	 */
-	smp_mb__before_atomic();
-	atomic_set(&kn->count, 1);
+	atomic_set_release(&kn->count, 1);
 	atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
 	RB_CLEAR_NODE(&kn->rb);
 
-- 
2.7.4