linux-kernel - [PATCH] dcache.c: Replace smp_read_barrier_depends() with lockless

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Date:	Sat, 26 Mar 2016 09:12:10 +0000
From:	He Kuang <hekuang@...wei.com>
To:	<viro@...iv.linux.org.uk>
CC:	<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<wangnan0@...wei.com>, <hekuang@...wei.com>
Subject: [PATCH] dcache.c: Replace smp_read_barrier_depends() with lockless_dereference()

lockless_dereference() was added which can be used in place of
hard-coding smp_read_barrier_depends(). The following PATCH makes the
change.

Signed-off-by: He Kuang <hekuang@...wei.com>
---
 fs/dcache.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 32ceae3..593264c 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -215,10 +215,9 @@ static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char
 
 static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
 {
-	const unsigned char *cs;
 	/*
 	 * Be careful about RCU walk racing with rename:
-	 * use ACCESS_ONCE to fetch the name pointer.
+	 * use 'lockless_dereference' to fetch the name pointer.
 	 *
 	 * NOTE! Even if a rename will mean that the length
 	 * was not loaded atomically, we don't care. The
@@ -232,8 +231,8 @@ static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *c
 	 * early because the data cannot match (there can
 	 * be no NUL in the ct/tcount data)
 	 */
-	cs = ACCESS_ONCE(dentry->d_name.name);
-	smp_read_barrier_depends();
+	const unsigned char *cs = lockless_dereference(dentry->d_name.name);
+
 	return dentry_string_cmp(cs, ct, tcount);
 }
 
-- 
1.8.5.2