dm cache: fix resize crash if user doesn't reload cache table
commit 5d07384a666d4b2f781dc056bfeec2c27fbdf383 upstream. A reload of the cache's DM table is needed during resize because otherwise a crash will occur when attempting to access smq policy entries associated with the portion of the cache that was recently extended. The reason is cache-size based data structures in the policy will not be resized, the only way to safely extend the cache is to allow for a proper cache policy initialization that occurs when the cache table is loaded. For example the smq policy's space_init(), init_allocator(), calc_hotspot_params() must be sized based on the extended cache size. The fix for this is to disallow cache resizes of this pattern: 1) suspend "cache" target's device 2) resize the fast device used for the cache 3) resume "cache" target's device Instead, the last step must be a full reload of the cache's DM table. Fixes: 66a636356 ("dm cache: add stochastic-multi-queue (smq) policy") Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -3097,8 +3097,13 @@ static dm_cblock_t get_cache_dev_size(struct cache *cache)
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static bool can_resize(struct cache *cache, dm_cblock_t new_size)
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{
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if (from_cblock(new_size) > from_cblock(cache->cache_size))
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return true;
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if (from_cblock(new_size) > from_cblock(cache->cache_size)) {
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if (cache->sized) {
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DMERR("%s: unable to extend cache due to missing cache table reload",
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cache_device_name(cache));
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return false;
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}
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}
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/*
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* We can't drop a dirty block when shrinking the cache.
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