dentry_cmp(): use lockless_dereference() instead of smp_read_barrier_depends()

lockless_dereference() was added which can be used in place of
hard-coding smp_read_barrier_depends().

Signed-off-by: He Kuang <hekuang@huawei.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/dcache.c b/fs/dcache.c
index e5c8ba7..dc37c02 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -226,10 +226,9 @@ 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)
 {
 
 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:
        /*
         * 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
         *
         * NOTE! Even if a rename will mean that the length
         * was not loaded atomically, we don't care. The


@@ -243,8 +242,8 @@ 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)
         */
         * 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);
 }
 
        return dentry_string_cmp(cs, ct, tcount);
 }