Remove unnecessary "head" arguments from some dlist/slist functions.

dlist_delete, dlist_insert_after, dlist_insert_before, slist_insert_after
do not need access to the list header, and indeed insisting on that negates
one of the main advantages of a doubly-linked list.

In consequence, revert addition of "cache_bucket" field to CatCTup.

src/backend/postmaster/autovacuum.c

@@ -580,7 +580,6 @@ AutoVacLauncherMain(int argc, char *argv[])
 		struct timeval nap;
 		TimestampTz current_time = 0;
 		bool		can_launch;
-		avl_dbase  *avdb;
 		int			rc;
 
 		/*
@@ -725,7 +724,8 @@ AutoVacLauncherMain(int argc, char *argv[])
 					worker->wi_tableoid = InvalidOid;
 					worker->wi_proc = NULL;
 					worker->wi_launchtime = 0;
-					dlist_push_head(&AutoVacuumShmem->av_freeWorkers, &worker->wi_links);
+					dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
+									&worker->wi_links);
 					AutoVacuumShmem->av_startingWorker = NULL;
 					elog(WARNING, "worker took too long to start; canceled");
 				}
@@ -760,6 +760,8 @@ AutoVacLauncherMain(int argc, char *argv[])
 			 * distant adl_next_worker first, we obtain our database from the
 			 * tail of the list.
 			 */
+			avl_dbase  *avdb;
+
 			avdb = dlist_tail_element(avl_dbase, adl_node, &DatabaseList);
 
 			/*
@@ -790,8 +792,6 @@ AutoVacLauncherMain(int argc, char *argv[])
 static void
 launcher_determine_sleep(bool canlaunch, bool recursing, struct timeval * nap)
 {
-	avl_dbase  *avdb;
-
 	/*
 	 * We sleep until the next scheduled vacuum.  We trust that when the
 	 * database list was built, care was taken so that no entries have times
@@ -807,6 +807,7 @@ launcher_determine_sleep(bool canlaunch, bool recursing, struct timeval * nap)
 	{
 		TimestampTz current_time = GetCurrentTimestamp();
 		TimestampTz next_wakeup;
+		avl_dbase  *avdb;
 		long		secs;
 		int			usecs;
 
@@ -1677,7 +1678,7 @@ FreeWorkerInfo(int code, Datum arg)
 		 */
 		AutovacuumLauncherPid = AutoVacuumShmem->av_launcherpid;
 
-		dlist_delete(&AutoVacuumShmem->av_runningWorkers, &MyWorkerInfo->wi_links);
+		dlist_delete(&MyWorkerInfo->wi_links);
 		MyWorkerInfo->wi_dboid = InvalidOid;
 		MyWorkerInfo->wi_tableoid = InvalidOid;
 		MyWorkerInfo->wi_proc = NULL;
@@ -1685,7 +1686,8 @@ FreeWorkerInfo(int code, Datum arg)
 		MyWorkerInfo->wi_cost_delay = 0;
 		MyWorkerInfo->wi_cost_limit = 0;
 		MyWorkerInfo->wi_cost_limit_base = 0;
-		dlist_push_head(&AutoVacuumShmem->av_freeWorkers, &MyWorkerInfo->wi_links);
+		dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
+						&MyWorkerInfo->wi_links);
 		/* not mine anymore */
 		MyWorkerInfo = NULL;
 
@@ -2863,7 +2865,8 @@ AutoVacuumShmemInit(void)
 
 		/* initialize the WorkerInfo free list */
 		for (i = 0; i < autovacuum_max_workers; i++)
-			dlist_push_head(&AutoVacuumShmem->av_freeWorkers, &worker[i].wi_links);
+			dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
+							&worker[i].wi_links);
 	}
 	else
 		Assert(found);

src/backend/postmaster/postmaster.c

@@ -2696,7 +2696,7 @@ CleanupBackend(int pid,
 				ShmemBackendArrayRemove(bp);
 #endif
 			}
-			dlist_delete(&BackendList, iter.cur);
+			dlist_delete(iter.cur);
 			free(bp);
 			break;
 		}
@@ -2744,7 +2744,7 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
 				ShmemBackendArrayRemove(bp);
 #endif
 			}
-			dlist_delete(&BackendList, iter.cur);
+			dlist_delete(iter.cur);
 			free(bp);
 			/* Keep looping so we can signal remaining backends */
 		}

src/backend/utils/cache/catcache.c

@@ -370,7 +370,7 @@ CatCacheRemoveCTup(CatCache *cache, CatCTup *ct)
 		return;					/* nothing left to do */
 	}
 
-	dlist_delete(ct->cache_bucket, &ct->cache_elem);
+	dlist_delete(&ct->cache_elem);
 
 	/* free associated tuple data */
 	if (ct->tuple.t_data != NULL)
@@ -413,7 +413,7 @@ CatCacheRemoveCList(CatCache *cache, CatCList *cl)
 	}
 
 	/* delink from linked list */
-	dlist_delete(&cache->cc_lists, &cl->cache_elem);
+	dlist_delete(&cl->cache_elem);
 
 	/* free associated tuple data */
 	if (cl->tuple.t_data != NULL)
@@ -1664,15 +1664,13 @@ CatalogCacheCreateEntry(CatCache *cache, HeapTuple ntp,
 	 */
 	ct->ct_magic = CT_MAGIC;
 	ct->my_cache = cache;
-	ct->cache_bucket = &cache->cc_bucket[hashIndex];
-
 	ct->c_list = NULL;
 	ct->refcount = 0;			/* for the moment */
 	ct->dead = false;
 	ct->negative = negative;
 	ct->hash_value = hashValue;
 
-	dlist_push_head(ct->cache_bucket, &ct->cache_elem);
+	dlist_push_head(&cache->cc_bucket[hashIndex], &ct->cache_elem);
 
 	cache->cc_ntup++;
 	CacheHdr->ch_ntup++;

src/include/lib/ilist.h

@@ -89,7 +89,7 @@
  *			continue;		// don't touch this one
  *
  *		// unlink the current table from the linked list
- *		dlist_delete(&db->tables, miter.cur);
+ *		dlist_delete(miter.cur);
  *		// as these lists never manage memory, we can still access the table
  *		// after it's been unlinked
  *		drop_table(db, tbl);
@@ -271,11 +271,9 @@ extern void dlist_init(dlist_head *head);
 extern bool dlist_is_empty(dlist_head *head);
 extern void dlist_push_head(dlist_head *head, dlist_node *node);
 extern void dlist_push_tail(dlist_head *head, dlist_node *node);
-extern void dlist_insert_after(dlist_head *head,
-				   dlist_node *after, dlist_node *node);
-extern void dlist_insert_before(dlist_head *head,
-					dlist_node *before, dlist_node *node);
-extern void dlist_delete(dlist_head *head, dlist_node *node);
+extern void dlist_insert_after(dlist_node *after, dlist_node *node);
+extern void dlist_insert_before(dlist_node *before, dlist_node *node);
+extern void dlist_delete(dlist_node *node);
 extern dlist_node *dlist_pop_head_node(dlist_head *head);
 extern void dlist_move_head(dlist_head *head, dlist_node *node);
 extern bool dlist_has_next(dlist_head *head, dlist_node *node);
@@ -352,50 +350,34 @@ dlist_push_tail(dlist_head *head, dlist_node *node)
  * Insert a node after another *in the same list*
  */
 STATIC_IF_INLINE void
-dlist_insert_after(dlist_head *head, dlist_node *after, dlist_node *node)
+dlist_insert_after(dlist_node *after, dlist_node *node)
 {
-	dlist_check(head);
-	/* XXX: assert 'after' is in 'head'? */
-
 	node->prev = after;
 	node->next = after->next;
 	after->next = node;
 	node->next->prev = node;
-
-	dlist_check(head);
 }
 
 /*
  * Insert a node before another *in the same list*
  */
 STATIC_IF_INLINE void
-dlist_insert_before(dlist_head *head, dlist_node *before, dlist_node *node)
+dlist_insert_before(dlist_node *before, dlist_node *node)
 {
-	dlist_check(head);
-	/* XXX: assert 'before' is in 'head'? */
-
 	node->prev = before->prev;
 	node->next = before;
 	before->prev = node;
 	node->prev->next = node;
-
-	dlist_check(head);
 }
 
 /*
- * Delete 'node' from list.
- *
- * It is not allowed to delete a 'node' which is is not in the list 'head'
+ * Delete 'node' from its list (it must be in one).
  */
 STATIC_IF_INLINE void
-dlist_delete(dlist_head *head, dlist_node *node)
+dlist_delete(dlist_node *node)
 {
-	dlist_check(head);
-
 	node->prev->next = node->next;
 	node->next->prev = node->prev;
-
-	dlist_check(head);
 }
 
 /*
@@ -408,7 +390,7 @@ dlist_pop_head_node(dlist_head *head)
 
 	Assert(!dlist_is_empty(head));
 	node = head->head.next;
-	dlist_delete(head, node);
+	dlist_delete(node);
 	return node;
 }
 
@@ -425,7 +407,7 @@ dlist_move_head(dlist_head *head, dlist_node *node)
 	if (head->head.next == node)
 		return;
 
-	dlist_delete(head, node);
+	dlist_delete(node);
 	dlist_push_head(head, node);
 
 	dlist_check(head);
@@ -591,8 +573,7 @@ dlist_tail_node(dlist_head *head)
 extern void slist_init(slist_head *head);
 extern bool slist_is_empty(slist_head *head);
 extern void slist_push_head(slist_head *head, slist_node *node);
-extern void slist_insert_after(slist_head *head,
-				   slist_node *after, slist_node *node);
+extern void slist_insert_after(slist_node *after, slist_node *node);
 extern slist_node *slist_pop_head_node(slist_head *head);
 extern bool slist_has_next(slist_head *head, slist_node *node);
 extern slist_node *slist_next_node(slist_head *head, slist_node *node);
@@ -640,12 +621,10 @@ slist_push_head(slist_head *head, slist_node *node)
  * Insert a node after another *in the same list*
  */
 STATIC_IF_INLINE void
-slist_insert_after(slist_head *head, slist_node *after, slist_node *node)
+slist_insert_after(slist_node *after, slist_node *node)
 {
 	node->next = after->next;
 	after->next = node;
-
-	slist_check(head);
 }
 
 /*

src/include/utils/catcache.h

@@ -82,7 +82,6 @@ typedef struct catctup
 	 * lookups.
 	 */
 	dlist_node	cache_elem;		/* list member of per-bucket list */
-	dlist_head *cache_bucket;	/* containing bucket dlist */
 
 	/*
 	 * The tuple may also be a member of at most one CatCList.	(If a single