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From: Miao Xie <miaox@cn.fujitsu.com>
To: Linux Fsdevel <linux-fsdevel@vger.kernel.org>
Cc: Jan Kara <jack@suse.cz>, Al Viro <viro@ZenIV.linux.org.uk>
Subject: [PATCH] vfs, freeze: use ACCESS_ONCE() to guard access to ->mnt_flags
Date: Fri, 16 Nov 2012 17:23:50 +0800	[thread overview]
Message-ID: <50A60626.4080200@cn.fujitsu.com> (raw)

The compiler may optimize the while loop and make the check just be done once,
so we should use ACCESS_ONCE() to guard access to ->mnt_flags

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
 fs/namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 7bdf790..6eca68e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -311,7 +311,7 @@ int __mnt_want_write(struct vfsmount *m)
 	 * incremented count after it has set MNT_WRITE_HOLD.
 	 */
 	smp_mb();
-	while (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
+	while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
 		cpu_relax();
 	/*
 	 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
-- 
1.7.11.7

             reply	other threads:[~2012-11-16  9:23 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-11-16  9:23 Miao Xie [this message]
2012-11-16 13:25 ` [PATCH] vfs, freeze: use ACCESS_ONCE() to guard access to ->mnt_flags Al Viro

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