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Commit d1d9220c authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
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dm cache: emit a warning message if there are a lot of cache blocks 



Loading and saving millions of block mappings takes time.  We may as
well explain what's going on, and encourage people to use a larger
cache block size.

Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 7ae34e77

drivers/md/dm-cache-target.c

+16 −3
Original line number Diff line number Diff line
@@ -2301,6 +2301,19 @@ static sector_t calculate_discard_block_size(sector_t cache_block_size, 
	return discard_block_size;

}



static void set_cache_size(struct cache *cache, dm_cblock_t size)

{

	dm_block_t nr_blocks = from_cblock(size);



	if (nr_blocks > (1 << 20) && cache->cache_size != size)

		DMWARN_LIMIT("You have created a cache device with a lot of individual cache blocks (%llu)\n"

			     "All these mappings can consume a lot of kernel memory, and take some time to read/write.\n"

			     "Please consider increasing the cache block size to reduce the overall cache block count.",

			     (unsigned long long) nr_blocks);



	cache->cache_size = size;

}



#define DEFAULT_MIGRATION_THRESHOLD 2048



static int cache_create(struct cache_args *ca, struct cache **result)
@@ -2356,10 +2369,10 @@ static int cache_create(struct cache_args *ca, struct cache **result) 


		cache->sectors_per_block_shift = -1;

		cache_size = block_div(cache_size, ca->block_size);

		cache->cache_size = to_cblock(cache_size);

		set_cache_size(cache, to_cblock(cache_size));

	} else {

		cache->sectors_per_block_shift = __ffs(ca->block_size);

		cache->cache_size = to_cblock(ca->cache_sectors >> cache->sectors_per_block_shift);

		set_cache_size(cache, to_cblock(ca->cache_sectors >> cache->sectors_per_block_shift));

	}



	r = create_cache_policy(cache, ca, error);
@@ -2856,7 +2869,7 @@ static int resize_cache_dev(struct cache *cache, dm_cblock_t new_size) 
		return r;

	}



	cache->cache_size = new_size;

	set_cache_size(cache, new_size);



	return 0;

}