4.4-stable review patch. If anyone has any objections, please let me know.
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From: Mike Snitzer snitzer@redhat.com
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
--- drivers/md/dm-cache-target.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -3391,8 +3391,13 @@ static dm_cblock_t get_cache_dev_size(st
static bool can_resize(struct cache *cache, dm_cblock_t new_size) { - if (from_cblock(new_size) > from_cblock(cache->cache_size)) - return true; + if (from_cblock(new_size) > from_cblock(cache->cache_size)) { + if (cache->sized) { + DMERR("%s: unable to extend cache due to missing cache table reload", + cache_device_name(cache)); + return false; + } + }
/* * We can't drop a dirty block when shrinking the cache.