Purge cache command

Purge invalidates all cache lines. It is very usefull feature for tests.

Calling purge is possbile with casadm `--script` swtich.

Signed-off-by: Michal Mielewczyk <michal.mielewczyk@intel.com>

modules/cas_cache/layer_cache_management.h

@@ -82,6 +82,8 @@ int cache_mngt_flush_object(const char *cache_name, size_t cache_name_len,
 
 int cache_mngt_flush_device(const char *cache_name, size_t name_len);
 
+int cache_mngt_purge_device(const char *cache_name, size_t name_len);
+
 int cache_mngt_list_caches(struct kcas_cache_list *list);
 
 int cache_mngt_interrupt_flushing(const char *cache_name, size_t name_len);