diff options
Diffstat (limited to 'drivers/md/dm-pcache/cache_segment.c')
| -rw-r--r-- | drivers/md/dm-pcache/cache_segment.c | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/drivers/md/dm-pcache/cache_segment.c b/drivers/md/dm-pcache/cache_segment.c index 8f9534ae04c3..f0b58980806e 100644 --- a/drivers/md/dm-pcache/cache_segment.c +++ b/drivers/md/dm-pcache/cache_segment.c @@ -72,7 +72,6 @@ static int cache_seg_ctrl_load(struct pcache_cache_segment *cache_seg) struct pcache_cache_seg_gen cache_seg_gen, *cache_seg_gen_addr; int ret = 0; - mutex_lock(&cache_seg->ctrl_lock); cache_seg_gen_addr = pcache_meta_find_latest(&cache_seg_ctrl->gen->header, sizeof(struct pcache_cache_seg_gen), sizeof(struct pcache_cache_seg_gen), @@ -93,7 +92,6 @@ static int cache_seg_ctrl_load(struct pcache_cache_segment *cache_seg) cache_seg->gen_seq = cache_seg_gen.header.seq; cache_seg->gen_index = (cache_seg_gen_addr - cache_seg_ctrl->gen); out: - mutex_unlock(&cache_seg->ctrl_lock); return ret; } @@ -105,11 +103,27 @@ static inline struct pcache_cache_seg_gen *get_cache_seg_gen_addr(struct pcache_ return (cache_seg_ctrl->gen + cache_seg->gen_index); } +/* + * cache_seg_ctrl_write - write cache segment control information + * @seg: the cache segment to update + * + * This function writes the control information of a cache segment to media. + * + * Although this updates shared control data, we intentionally do not use + * any locking here. All accesses to control information are single-threaded: + * + * - All reads occur during the init phase, where no concurrent writes + * can happen. + * - Writes happen once during init and once when the last reference + * to the segment is dropped in cache_seg_put(). + * + * Both cases are guaranteed to be single-threaded, so there is no risk + * of concurrent read/write races. + */ static void cache_seg_ctrl_write(struct pcache_cache_segment *cache_seg) { struct pcache_cache_seg_gen cache_seg_gen; - mutex_lock(&cache_seg->ctrl_lock); cache_seg_gen.gen = cache_seg->gen; cache_seg_gen.header.seq = ++cache_seg->gen_seq; cache_seg_gen.header.crc = pcache_meta_crc(&cache_seg_gen.header, @@ -119,7 +133,6 @@ static void cache_seg_ctrl_write(struct pcache_cache_segment *cache_seg) pmem_wmb(); cache_seg->gen_index = (cache_seg->gen_index + 1) % PCACHE_META_INDEX_MAX; - mutex_unlock(&cache_seg->ctrl_lock); } static void cache_seg_ctrl_init(struct pcache_cache_segment *cache_seg) @@ -177,7 +190,6 @@ int cache_seg_init(struct pcache_cache *cache, u32 seg_id, u32 cache_seg_id, spin_lock_init(&cache_seg->gen_lock); atomic_set(&cache_seg->refs, 0); mutex_init(&cache_seg->info_lock); - mutex_init(&cache_seg->ctrl_lock); /* init pcache_segment */ seg_options.type = PCACHE_SEGMENT_TYPE_CACHE_DATA; |