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authorMikulas Patocka <mpatocka@redhat.com>2012-10-12 16:59:46 +0100
committerAlasdair G Kergon <agk@redhat.com>2012-10-12 16:59:46 +0100
commitfe5fe90639b62a75349dd1f1c74c4a984397171c (patch)
tree50332fca2fb4ff5851c4e1bfd8151d41ba83d781 /drivers/md
parent54499afbb80e44ae5511984486b4b33d6229fceb (diff)
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: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-bufio.c10
-rw-r--r--drivers/md/dm-verity.c2
2 files changed, 4 insertions, 8 deletions
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index b9e006aa6062..651ca79881dd 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -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;
diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
index 892ae2766aa6..9e7328bb4030 100644
--- a/drivers/md/dm-verity.c
+++ b/drivers/md/dm-verity.c
@@ -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))