From 08b184514f65d160ce66381dafca5962e3d8f785 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Thu, 6 Nov 2014 14:38:01 +0000 Subject: [PATCH] dm cache: revert "prevent corruption caused by discard_block_size > cache_block_size" This reverts commit d132cc6d9e92424bb9d4fd35f5bd0e55d583f4be because we actually do want to allow the discard blocksize to be larger than the cache blocksize. Further dm-cache discard changes will make this possible. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer --- drivers/md/dm-cache-target.c | 37 +++++++++++++++++++++++++++++++++--- 1 file changed, 34 insertions(+), 3 deletions(-) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index ced7fd4adddb..c2ca74374944 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -238,7 +238,7 @@ struct cache { */ dm_dblock_t discard_nr_blocks; unsigned long *discard_bitset; - uint32_t discard_block_size; + uint32_t discard_block_size; /* a power of 2 times sectors per block */ /* * Rather than reconstructing the table line for the status we just @@ -2197,6 +2197,35 @@ static int create_cache_policy(struct cache *cache, struct cache_args *ca, return 0; } +/* + * We want the discard block size to be a power of two, at least the size + * of the cache block size, and have no more than 2^14 discard blocks + * across the origin. + */ +#define MAX_DISCARD_BLOCKS (1 << 14) + +static bool too_many_discard_blocks(sector_t discard_block_size, + sector_t origin_size) +{ + (void) sector_div(origin_size, discard_block_size); + + return origin_size > MAX_DISCARD_BLOCKS; +} + +static sector_t calculate_discard_block_size(sector_t cache_block_size, + sector_t origin_size) +{ + sector_t discard_block_size; + + discard_block_size = roundup_pow_of_two(cache_block_size); + + if (origin_size) + while (too_many_discard_blocks(discard_block_size, origin_size)) + discard_block_size *= 2; + + return discard_block_size; +} + #define DEFAULT_MIGRATION_THRESHOLD 2048 static int cache_create(struct cache_args *ca, struct cache **result) @@ -2320,7 +2349,9 @@ static int cache_create(struct cache_args *ca, struct cache **result) } clear_bitset(cache->dirty_bitset, from_cblock(cache->cache_size)); - cache->discard_block_size = cache->sectors_per_block; + cache->discard_block_size = + calculate_discard_block_size(cache->sectors_per_block, + cache->origin_sectors); cache->discard_nr_blocks = oblock_to_dblock(cache, cache->origin_blocks); cache->discard_bitset = alloc_bitset(from_dblock(cache->discard_nr_blocks)); if (!cache->discard_bitset) { @@ -3099,7 +3130,7 @@ static void set_discard_limits(struct cache *cache, struct queue_limits *limits) /* * FIXME: these limits may be incompatible with the cache device */ - limits->max_discard_sectors = cache->discard_block_size; + limits->max_discard_sectors = cache->discard_block_size * 1024; limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT; }