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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: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
hifive-unleashed-5.1
Joe Thornber 2014-11-11 11:58:32 +00:00 committed by Mike Snitzer
parent 7ae34e7778
commit d1d9220cba
1 changed files with 16 additions and 3 deletions
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19
drivers/md/dm-cache-target.c
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@ -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;
}