linux-kernel - [PATCH 2/2] vfs: stop counting on gcc not messing with mnt_expiry

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Message-Id: <20231004111916.728135-3-mjguzik@gmail.com>
Date:   Wed,  4 Oct 2023 13:19:16 +0200
From:   Mateusz Guzik <mjguzik@...il.com>
To:     brauner@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH 2/2] vfs: stop counting on gcc not messing with mnt_expiry_mark if not asked

So happens it already was not doing it, but there is no need to "hope"
as indicated in the comment.

No changes in generated assembly.

Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
---
 fs/namespace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index e157efc54023..d785bcb75111 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1344,9 +1344,9 @@ void mntput(struct vfsmount *mnt)
 {
 	if (mnt) {
 		struct mount *m = real_mount(mnt);
-		/* avoid cacheline pingpong, hope gcc doesn't get "smart" */
+		/* avoid cacheline pingpong */
 		if (unlikely(m->mnt_expiry_mark))
-			m->mnt_expiry_mark = 0;
+			WRITE_ONCE(m->mnt_expiry_mark, 0);
 		mntput_no_expire(m);
 	}
 }
-- 
2.39.2