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| author | Mikulas Patocka <mpatocka@redhat.com> | 2012-10-12 16:59:46 +0100 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2012-10-12 16:59:46 +0100 |
| commit | fe5fe90639b62a75349dd1f1c74c4a984397171c (patch) | |
| tree | 50332fca2fb4ff5851c4e1bfd8151d41ba83d781 | |
| parent | 54499afbb80e44ae5511984486b4b33d6229fceb (diff) | |
| download | blackbird-op-linux-fe5fe90639b62a75349dd1f1c74c4a984397171c.tar.gz blackbird-op-linux-fe5fe90639b62a75349dd1f1c74c4a984397171c.zip | |
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>
| -rw-r--r-- | drivers/md/dm-bufio.c | 10 | ||||
| -rw-r--r-- | drivers/md/dm-verity.c | 2 |
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)) |
