locking/atomics, fs/dcache: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()

For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.

However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.

It's possible to transform the bulk of kernel code using the Coccinelle
script below. However, this doesn't handle comments, leaving references
to ACCESS_ONCE() instances which have been removed. As a preparatory
step, this patch converts the dcache code and comments to use
{READ,WRITE}_ONCE() consistently.

----
virtual patch

@ depends on patch @
expression E1, E2;
@@

- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)

@ depends on patch @
expression E;
@@

- ACCESS_ONCE(E)
+ READ_ONCE(E)
----

Signed-off-by: Mark Rutland <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index ed1a7cf6923a..1d8f5818f647 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -519,7 +519,7 @@ static inline struct inode *d_inode(const struct dentry *dentry)
 }
 
 /**
- * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
+ * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
  * @dentry: The dentry to query
  *
  * This is the helper normal filesystems should use to get at their own inodes
@@ -527,7 +527,7 @@ static inline struct inode *d_inode(const struct dentry *dentry)
  */
 static inline struct inode *d_inode_rcu(const struct dentry *dentry)
 {
-	return ACCESS_ONCE(dentry->d_inode);
+	return READ_ONCE(dentry->d_inode);
 }
 
 /**