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Commit fe5fe906 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Alasdair G Kergon
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dm: use ACCESS_ONCE for sysfs values 



Use the ACCESS_ONCE macro in dm-bufio and dm-verity where a variable
can be modified asynchronously (through sysfs) and we want to prevent
compiler optimizations that assume that the variable hasn't changed.
(See Documentation/atomic_ops.txt.)

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 54499afb

drivers/md/dm-bufio.c

+3 −7
Original line number Diff line number Diff line
@@ -280,9 +280,7 @@ 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 = dm_bufio_cache_size;



	barrier();

	dm_bufio_cache_size_latch = ACCESS_ONCE(dm_bufio_cache_size);



	/*

	 * Use default if set to 0 and report the actual cache size used.
@@ -812,7 +810,7 @@ static void __get_memory_limit(struct dm_bufio_client *c, 
{

	unsigned long buffers;



	if (dm_bufio_cache_size != dm_bufio_cache_size_latch) {

	if (ACCESS_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch) {

		mutex_lock(&dm_bufio_clients_lock);

		__cache_size_refresh();

		mutex_unlock(&dm_bufio_clients_lock);
@@ -1590,11 +1588,9 @@ EXPORT_SYMBOL_GPL(dm_bufio_client_destroy); 


static void cleanup_old_buffers(void)

{

	unsigned long max_age = dm_bufio_max_age;

	unsigned long max_age = ACCESS_ONCE(dm_bufio_max_age);

	struct dm_bufio_client *c;



	barrier();



	if (max_age > ULONG_MAX / HZ)

		max_age = ULONG_MAX / HZ;

drivers/md/dm-verity.c

+1 −1
Original line number Diff line number Diff line
@@ -438,7 +438,7 @@ static void verity_prefetch_io(struct dm_verity *v, struct dm_verity_io *io) 
		verity_hash_at_level(v, io->block, i, &hash_block_start, NULL);

		verity_hash_at_level(v, io->block + io->n_blocks - 1, i, &hash_block_end, NULL);

		if (!i) {

			unsigned cluster = *(volatile unsigned *)&dm_verity_prefetch_cluster;

			unsigned cluster = ACCESS_ONCE(dm_verity_prefetch_cluster);



			cluster >>= v->data_dev_block_bits;

			if (unlikely(!cluster))