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>

9 files changed, 32 insertions, 32 deletions

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index d216a8f7bc22..33bb074d6941 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -347,7 +347,7 @@ static void __cache_size_refresh(void)
 	BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
 	BUG_ON(dm_bufio_client_count < 0);
 
-	dm_bufio_cache_size_latch = ACCESS_ONCE(dm_bufio_cache_size);
+	dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
 
 	/*
 	 * Use default if set to 0 and report the actual cache size used.
@@ -960,7 +960,7 @@ static void __get_memory_limit(struct dm_bufio_client *c,
 {
 	unsigned long buffers;
 
-	if (unlikely(ACCESS_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch)) {
+	if (unlikely(READ_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch)) {
 		if (mutex_trylock(&dm_bufio_clients_lock)) {
 			__cache_size_refresh();
 			mutex_unlock(&dm_bufio_clients_lock);
@@ -1600,7 +1600,7 @@ static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
 
 static unsigned long get_retain_buffers(struct dm_bufio_client *c)
 {
-        unsigned long retain_bytes = ACCESS_ONCE(dm_bufio_retain_bytes);
+        unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes);
         return retain_bytes >> (c->sectors_per_block_bits + SECTOR_SHIFT);
 }
 
@@ -1647,7 +1647,7 @@ dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
 {
 	struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
 
-	return ACCESS_ONCE(c->n_buffers[LIST_CLEAN]) + ACCESS_ONCE(c->n_buffers[LIST_DIRTY]);
+	return READ_ONCE(c->n_buffers[LIST_CLEAN]) + READ_ONCE(c->n_buffers[LIST_DIRTY]);
 }
 
 /*
@@ -1818,7 +1818,7 @@ EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
 
 static unsigned get_max_age_hz(void)
 {
-	unsigned max_age = ACCESS_ONCE(dm_bufio_max_age);
+	unsigned max_age = READ_ONCE(dm_bufio_max_age);
 
 	if (max_age > UINT_MAX / HZ)
 		max_age = UINT_MAX / HZ;
diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index cf2c67e35eaf..eb45cc3df31d 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -107,7 +107,7 @@ static void io_job_start(struct dm_kcopyd_throttle *t)
 try_again:
 	spin_lock_irq(&throttle_spinlock);
 
-	throttle = ACCESS_ONCE(t->throttle);
+	throttle = READ_ONCE(t->throttle);
 
 	if (likely(throttle >= 100))
 		goto skip_limit;
@@ -157,7 +157,7 @@ static void io_job_finish(struct dm_kcopyd_throttle *t)
 
 	t->num_io_jobs--;
 
-	if (likely(ACCESS_ONCE(t->throttle) >= 100))
+	if (likely(READ_ONCE(t->throttle) >= 100))
 		goto skip_limit;
 
 	if (!t->num_io_jobs) {
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]);
 		}
 	}
 }
diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
index 4c8de1ff78ca..8d0ba879777e 100644
--- a/drivers/md/dm-switch.c
+++ b/drivers/md/dm-switch.c
@@ -144,7 +144,7 @@ static unsigned switch_region_table_read(struct switch_ctx *sctx, unsigned long
 
 	switch_get_position(sctx, region_nr, &region_index, &bit);
 
-	return (ACCESS_ONCE(sctx->region_table[region_index]) >> bit) &
+	return (READ_ONCE(sctx->region_table[region_index]) >> bit) &
 		((1 << sctx->region_table_entry_bits) - 1);
 }
 
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 1e25705209c2..89e5dff9b4cf 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2431,7 +2431,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
 	struct pool_c *pt = pool->ti->private;
 	bool needs_check = dm_pool_metadata_needs_check(pool->pmd);
 	enum pool_mode old_mode = get_pool_mode(pool);
-	unsigned long no_space_timeout = ACCESS_ONCE(no_space_timeout_secs) * HZ;
+	unsigned long no_space_timeout = READ_ONCE(no_space_timeout_secs) * HZ;
 
 	/*
 	 * Never allow the pool to transition to PM_WRITE mode if user
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index bda3caca23ca..fba93237a780 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -589,7 +589,7 @@ static void verity_prefetch_io(struct work_struct *work)
 		verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
 		verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
 		if (!i) {
-			unsigned cluster = ACCESS_ONCE(dm_verity_prefetch_cluster);
+			unsigned cluster = READ_ONCE(dm_verity_prefetch_cluster);
 
 			cluster >>= v->data_dev_block_bits;
 			if (unlikely(!cluster))
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 4be85324f44d..8aaffa19b29a 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -114,7 +114,7 @@ static unsigned reserved_bio_based_ios = RESERVED_BIO_BASED_IOS;
 
 static int __dm_get_module_param_int(int *module_param, int min, int max)
 {
-	int param = ACCESS_ONCE(*module_param);
+	int param = READ_ONCE(*module_param);
 	int modified_param = 0;
 	bool modified = true;
 
@@ -136,7 +136,7 @@ static int __dm_get_module_param_int(int *module_param, int min, int max)
 unsigned __dm_get_module_param(unsigned *module_param,
 			       unsigned def, unsigned max)
 {
-	unsigned param = ACCESS_ONCE(*module_param);
+	unsigned param = READ_ONCE(*module_param);
 	unsigned modified_param = 0;
 
 	if (!param)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 0ff1bbf6c90e..447ddcbc9566 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2651,7 +2651,7 @@ state_show(struct md_rdev *rdev, char *page)
 {
 	char *sep = ",";
 	size_t len = 0;
-	unsigned long flags = ACCESS_ONCE(rdev->flags);
+	unsigned long flags = READ_ONCE(rdev->flags);
 
 	if (test_bit(Faulty, &flags) ||
 	    (!test_bit(ExternalBbl, &flags) &&
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 928e24a07133..7d9a50eed9db 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6072,7 +6072,7 @@ static inline sector_t raid5_sync_request(struct mddev *mddev, sector_t sector_n
 	 */
 	rcu_read_lock();
 	for (i = 0; i < conf->raid_disks; i++) {
-		struct md_rdev *rdev = ACCESS_ONCE(conf->disks[i].rdev);
+		struct md_rdev *rdev = READ_ONCE(conf->disks[i].rdev);
 
 		if (rdev == NULL || test_bit(Faulty, &rdev->flags))
 			still_degraded = 1;