FIXME - barriers need removing; current code doesn't use volatile From: Mikulas Patocka X-Patchwork-Id: 50010 Hi This is a simple cleanup patch. Mikulas --- dm-bufio & dm-verity: use ACCESS_ONCE instead of volatile If the variable can be asynchronously modified and we want to prevent compiler optimizations that could assume that the variable is the same, use ACCESS_ONCE macro, as documented in Documentation/atomic_ops.txt. Signed-off-by: Mikulas Patocka --- drivers/md/dm-bufio.c | 6 +++--- drivers/md/dm-verity.c | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel Index: linux-3.5.1-fast/drivers/md/dm-bufio.c =================================================================== --- linux-3.5.1-fast.orig/drivers/md/dm-bufio.c 2012-08-16 00:46:43.000000000 +0200 +++ linux-3.5.1-fast/drivers/md/dm-bufio.c 2012-08-16 00:49:08.000000000 +0200 @@ -280,7 +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 = *(volatile unsigned long *)&dm_bufio_cache_size; + dm_bufio_cache_size_latch = ACCESS_ONCE(dm_bufio_cache_size); /* * Use default if set to 0 and report the actual cache size used. @@ -811,7 +811,7 @@ static void __get_memory_limit(struct dm { unsigned long buffers; - if (*(volatile unsigned long *)&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); @@ -1589,7 +1589,7 @@ EXPORT_SYMBOL_GPL(dm_bufio_client_destro static void cleanup_old_buffers(void) { - unsigned long max_age = *(volatile unsigned *)&dm_bufio_max_age; + unsigned long max_age = ACCESS_ONCE(dm_bufio_max_age); struct dm_bufio_client *c; if (max_age > ULONG_MAX / HZ) Index: linux-3.5.1-fast/drivers/md/dm-verity.c =================================================================== --- linux-3.5.1-fast.orig/drivers/md/dm-verity.c 2012-08-16 00:46:14.000000000 +0200 +++ linux-3.5.1-fast/drivers/md/dm-verity.c 2012-08-16 00:47:11.000000000 +0200 @@ -438,7 +438,7 @@ static void verity_prefetch_io(struct dm 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))