New force-delete option on consensus_cache_delete_pending()

If we're out of file space in the storage directory, we'll need to
get rid of old files fast.

src/or/conscache.c

@@ -95,7 +95,7 @@ consensus_cache_register_with_sandbox(consensus_cache_t *cache,
 static void
 consensus_cache_clear(consensus_cache_t *cache)
 {
-  consensus_cache_delete_pending(cache);
+  consensus_cache_delete_pending(cache, 0);
 
   SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
     ent->in_cache = NULL;
@@ -401,17 +401,19 @@ consensus_cache_unmap_lazy(consensus_cache_t *cache, time_t cutoff)
 
 /**
  * Delete every element of <b>cache</b> has been marked with
- * consensus_cache_entry_mark_for_removal, and which is not in use except by
- * the cache.
+ * consensus_cache_entry_mark_for_removal.  If <b>force</b> is false,
+ * retain those entries which are not in use except by the cache.
  */
 void
-consensus_cache_delete_pending(consensus_cache_t *cache)
+consensus_cache_delete_pending(consensus_cache_t *cache, int force)
 {
   SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
     tor_assert_nonfatal(ent->in_cache == cache);
-    if (ent->refcnt > 1 || BUG(ent->in_cache == NULL)) {
-      /* Somebody is using this entry right now */
-      continue;
+    if (! force) {
+      if (ent->refcnt > 1 || BUG(ent->in_cache == NULL)) {
+        /* Somebody is using this entry right now */
+        continue;
+      }
     }
     if (ent->can_remove == 0) {
       /* Don't want to delete this. */

src/or/conscache.h

@@ -17,7 +17,8 @@ struct sandbox_cfg_elem;
 int consensus_cache_register_with_sandbox(consensus_cache_t *cache,
                                           struct sandbox_cfg_elem **cfg);
 void consensus_cache_unmap_lazy(consensus_cache_t *cache, time_t cutoff);
-void consensus_cache_delete_pending(consensus_cache_t *cache);
+void consensus_cache_delete_pending(consensus_cache_t *cache,
+                                    int force);
 consensus_cache_entry_t *consensus_cache_add(consensus_cache_t *cache,
                                              const config_line_t *labels,
                                              const uint8_t *data,

src/or/consdiffmgr.c

@@ -614,7 +614,7 @@ consdiffmgr_cleanup(void)
   smartlist_free(diffs);
 
   // Actually remove files, if they're not used.
-  consensus_cache_delete_pending(cdm_cache_get());
+  consensus_cache_delete_pending(cdm_cache_get(), 0);
   return n_to_delete;
 }
 

src/test/test_conscache.c

@@ -203,7 +203,7 @@ test_conscache_cleanup(void *arg)
   tt_assert(e_tmp == NULL); // not found because pending deletion.
 
   /* Delete the pending-deletion items. */
-  consensus_cache_delete_pending(cache);
+  consensus_cache_delete_pending(cache, 0);
   {
     smartlist_t *entries = smartlist_new();
     consensus_cache_find_all(entries, cache, NULL, NULL);