Fixed LP bug #939866.

The field key_cache_mem_size of the KEY_CACHE structure must be
initialized in the function init_key_cache() and updated in the
function resize_key_cache().

mysys/mf_keycache.c

@@ -5945,6 +5945,10 @@ int init_key_cache(KEY_CACHE *keycache, uint key_cache_block_size,
                         ((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->partitions :
                         0;
   DBUG_ASSERT(partitions <= MAX_KEY_CACHE_PARTITIONS);
+  keycache->key_cache_mem_size=
+    keycache->partitions ?
+    ((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->key_cache_mem_size :
+    ((SIMPLE_KEY_CACHE_CB *) keycache_cb)->key_cache_mem_size;
   if (blocks > 0)
     keycache->can_be_used= 1;
   return blocks;
@@ -6008,6 +6012,11 @@ int resize_key_cache(KEY_CACHE *keycache, uint key_cache_block_size,
           ((PARTITIONED_KEY_CACHE_CB *)(keycache->keycache_cb))->partitions;
     }
 
+    keycache->key_cache_mem_size=
+    keycache->partitions ?
+    ((PARTITIONED_KEY_CACHE_CB *)(keycache->keycache_cb))->key_cache_mem_size :
+    ((SIMPLE_KEY_CACHE_CB *)(keycache->keycache_cb))->key_cache_mem_size;
+
     keycache->can_be_used= (blocks >= 0);
   } 
   return blocks;