locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()

Please do not apply this to mainline directly, instead please re-run the
coccinelle script shown below and apply its output.

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 harmful, and changing them results in
churn.

However, for some features, the read/write distinction is critical to
correct operation. To distinguish these cases, separate read/write
accessors must be used. This patch migrates (most) remaining
ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following
coccinelle script:

----
// Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and
// WRITE_ONCE()

// $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch

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 <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 18 insertions, 18 deletions

diff --git a/drivers/md/dm-stats.c b/drivers/md/dm-stats.c
index 6028d8247f58..a1a5eec783cc 100644
--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -431,7 +431,7 @@ do_sync_free:
 		synchronize_rcu_expedited();
 		dm_stat_free(&s->rcu_head);
 	} else {
-		ACCESS_ONCE(dm_stat_need_rcu_barrier) = 1;
+		WRITE_ONCE(dm_stat_need_rcu_barrier, 1);
 		call_rcu(&s->rcu_head, dm_stat_free);
 	}
 	return 0;
@@ -639,12 +639,12 @@ void dm_stats_account_io(struct dm_stats *stats, unsigned long bi_rw,
 		 */
 		last = raw_cpu_ptr(stats->last);
 		stats_aux->merged =
-			(bi_sector == (ACCESS_ONCE(last->last_sector) &&
+			(bi_sector == (READ_ONCE(last->last_sector) &&
 				       ((bi_rw == WRITE) ==
-					(ACCESS_ONCE(last->last_rw) == WRITE))
+					(READ_ONCE(last->last_rw) == WRITE))
 				       ));
-		ACCESS_ONCE(last->last_sector) = end_sector;
-		ACCESS_ONCE(last->last_rw) = bi_rw;
+		WRITE_ONCE(last->last_sector, end_sector);
+		WRITE_ONCE(last->last_rw, bi_rw);
 	}
 
 	rcu_read_lock();
@@ -693,22 +693,22 @@ static void __dm_stat_init_temporary_percpu_totals(struct dm_stat_shared *shared
 
 	for_each_possible_cpu(cpu) {
 		p = &s->stat_percpu[cpu][x];
-		shared->tmp.sectors[READ] += ACCESS_ONCE(p->sectors[READ]);
-		shared->tmp.sectors[WRITE] += ACCESS_ONCE(p->sectors[WRITE]);
-		shared->tmp.ios[READ] += ACCESS_ONCE(p->ios[READ]);
-		shared->tmp.ios[WRITE] += ACCESS_ONCE(p->ios[WRITE]);
-		shared->tmp.merges[READ] += ACCESS_ONCE(p->merges[READ]);
-		shared->tmp.merges[WRITE] += ACCESS_ONCE(p->merges[WRITE]);
-		shared->tmp.ticks[READ] += ACCESS_ONCE(p->ticks[READ]);
-		shared->tmp.ticks[WRITE] += ACCESS_ONCE(p->ticks[WRITE]);
-		shared->tmp.io_ticks[READ] += ACCESS_ONCE(p->io_ticks[READ]);
-		shared->tmp.io_ticks[WRITE] += ACCESS_ONCE(p->io_ticks[WRITE]);
-		shared->tmp.io_ticks_total += ACCESS_ONCE(p->io_ticks_total);
-		shared->tmp.time_in_queue += ACCESS_ONCE(p->time_in_queue);
+		shared->tmp.sectors[READ] += READ_ONCE(p->sectors[READ]);
+		shared->tmp.sectors[WRITE] += READ_ONCE(p->sectors[WRITE]);
+		shared->tmp.ios[READ] += READ_ONCE(p->ios[READ]);
+		shared->tmp.ios[WRITE] += READ_ONCE(p->ios[WRITE]);
+		shared->tmp.merges[READ] += READ_ONCE(p->merges[READ]);
+		shared->tmp.merges[WRITE] += READ_ONCE(p->merges[WRITE]);
+		shared->tmp.ticks[READ] += READ_ONCE(p->ticks[READ]);
+		shared->tmp.ticks[WRITE] += READ_ONCE(p->ticks[WRITE]);
+		shared->tmp.io_ticks[READ] += READ_ONCE(p->io_ticks[READ]);
+		shared->tmp.io_ticks[WRITE] += READ_ONCE(p->io_ticks[WRITE]);
+		shared->tmp.io_ticks_total += READ_ONCE(p->io_ticks_total);
+		shared->tmp.time_in_queue += READ_ONCE(p->time_in_queue);
 		if (s->n_histogram_entries) {
 			unsigned i;
 			for (i = 0; i < s->n_histogram_entries + 1; i++)
-				shared->tmp.histogram[i] += ACCESS_ONCE(p->histogram[i]);
+				shared->tmp.histogram[i] += READ_ONCE(p->histogram[i]);
 		}
 	}
 }