linux-kernel - [PATCH tip/core/rcu 09/12] fs: Substitute rcu_access_pointer() for rcu_dereference

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Message-Id: <1392672959-6386-9-git-send-email-paulmck@linux.vnet.ibm.com>
Date:	Mon, 17 Feb 2014 13:35:56 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com,
	edumazet@...gle.com, darren@...art.com, fweisbec@...il.com,
	oleg@...hat.com, sbw@....edu,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH tip/core/rcu 09/12] fs: Substitute rcu_access_pointer() for rcu_dereference_raw()

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

(Trivial patch.)

If the code is looking at the RCU-protected pointer itself, but not
dereferencing it, the rcu_dereference() functions can be downgraded to
rcu_access_pointer().  This commit makes this downgrade in __alloc_fd(),
which simply compares the RCU-protected pointer against NULL with no
dereferencing.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: linux-fsdevel@...r.kernel.org
---
 fs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/file.c b/fs/file.c
index db25c2bdfe46..18f7d27855c4 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -497,7 +497,7 @@ repeat:
 	error = fd;
 #if 1
 	/* Sanity check */
-	if (rcu_dereference_raw(fdt->fd[fd]) != NULL) {
+	if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
 		printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
 		rcu_assign_pointer(fdt->fd[fd], NULL);
 	}
-- 
1.8.1.5

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