From: Kurt Zeilenga <kurt@openldap.org>
Date: Thu, 11 Feb 1999 17:46:56 +0000 (+0000)
Subject: Update LDBM cache so that it manages it's own state.
X-Git-Tag: OPENLDAP_SLAPD_BACK_LDAP~597
X-Git-Url: https://git.sur5r.net/?a=commitdiff_plain;h=745a10f080251e46808535dcdd9ad80d9c76146e;p=openldap

Update LDBM cache so that it manages it's own state.
cache_set_state() and state args are no history.
Move cache_entry_cmp() and friends to slapd/entry.c to allow sharing
of functions between backends..  Renamed to entry_cmp().
---

diff --git a/servers/slapd/back-bdb2/cache.c b/servers/slapd/back-bdb2/cache.c
index e7ec725721..8c95392d28 100644
--- a/servers/slapd/back-bdb2/cache.c
+++ b/servers/slapd/back-bdb2/cache.c
@@ -27,25 +27,9 @@ static void	lru_print(struct cache *cache);
  *
  * these correspond to three different avl trees that are maintained.
  */
-
-static int
-cache_entry_cmp( Entry *e1, Entry *e2 )
-{
-	return( e1 < e2 ? -1 : (e1 > e2 ? 1 : 0) );
-}
-
-static int
-cache_entrydn_cmp( Entry *e1, Entry *e2 )
-{
-	/* compare their normalized UPPERCASED dn's */
-	return( strcmp( e1->e_ndn, e2->e_ndn ) );
-}
-
-static int
-cache_entryid_cmp( Entry *e1, Entry *e2 )
-{
-	return( e1->e_id < e2->e_id ? -1 : (e1->e_id > e2->e_id ? 1 : 0) );
-}
+#define cache_entry_cmp entry_cmp
+#define cache_entrydn_cmp entry_dn_cmp
+#define cache_entryid_cmp entry_id_cmp
 
 void
 bdb2i_cache_set_state( struct cache *cache, Entry *e, int state )
diff --git a/servers/slapd/back-ldbm/add.c b/servers/slapd/back-ldbm/add.c
index b99ade9cf5..4b929987ae 100644
--- a/servers/slapd/back-ldbm/add.c
+++ b/servers/slapd/back-ldbm/add.c
@@ -126,7 +126,7 @@ ldbm_back_add(
 	/*
 	 * Try to add the entry to the cache, assign it a new dnid.
 	 */
-	rc = cache_add_entry_rw(&li->li_cache, e, ENTRY_STATE_CREATING, 1);
+	rc = cache_add_entry_rw(&li->li_cache, e, CACHE_WRITE_LOCK);
 
 	if ( rc != 0 ) {
 		if( p != NULL) {
@@ -218,8 +218,6 @@ return_results:;
 		ldap_pvt_thread_mutex_unlock(&li->li_root_mutex);
 	}
 
-	cache_set_state( &li->li_cache, e, 0 );
-
 	/* free entry and writer lock */
 	cache_return_entry_w( &li->li_cache, e ); 
 
diff --git a/servers/slapd/back-ldbm/back-ldbm.h b/servers/slapd/back-ldbm/back-ldbm.h
index 9b98c02cb0..417027f3cc 100644
--- a/servers/slapd/back-ldbm/back-ldbm.h
+++ b/servers/slapd/back-ldbm/back-ldbm.h
@@ -79,8 +79,8 @@ struct cache {
 	ldap_pvt_thread_mutex_t	c_mutex;
 };
 
-#define ENTRY_STATE_DELETED		1
-#define ENTRY_STATE_CREATING	2
+#define CACHE_READ_LOCK		0
+#define CACHE_WRITE_LOCK	1
 
 /* for the cache of open index files */
 struct dbcache {
diff --git a/servers/slapd/back-ldbm/cache.c b/servers/slapd/back-ldbm/cache.c
index 0a2b3c97b1..a1877e0738 100644
--- a/servers/slapd/back-ldbm/cache.c
+++ b/servers/slapd/back-ldbm/cache.c
@@ -22,6 +22,10 @@ struct ldbm_entry_info {
 	 * be hidden.
 	 */
 	int		lei_state;	/* for the cache */
+#define	CACHE_ENTRY_UNDEFINED	0
+#define CACHE_ENTRY_CREATING	1
+#define CACHE_ENTRY_READY		2
+#define CACHE_ENTRY_DELETED		3
 
 	int		lei_refcnt;	/* # threads ref'ing this entry */
 	struct entry	*lei_lrunext;	/* for cache lru list */
@@ -44,42 +48,14 @@ static void	lru_print(struct cache *cache);
  *
  * these correspond to three different avl trees that are maintained.
  */
-
-static int
-cache_entry_cmp( Entry *e1, Entry *e2 )
-{
-	return( e1 < e2 ? -1 : (e1 > e2 ? 1 : 0) );
-}
-
-static int
-cache_entrydn_cmp( Entry *e1, Entry *e2 )
-{
-	/* compare their normalized UPPERCASED dn's */
-	return( strcmp( e1->e_ndn, e2->e_ndn ) );
-}
-
-static int
-cache_entryid_cmp( Entry *e1, Entry *e2 )
-{
-	return( e1->e_id < e2->e_id ? -1 : (e1->e_id > e2->e_id ? 1 : 0) );
-}
-
-void
-cache_set_state( struct cache *cache, Entry *e, int state )
-{
-	/* set cache mutex */
-	ldap_pvt_thread_mutex_lock( &cache->c_mutex );
-
-	LEI(e)->lei_state = state;
-
-	/* free cache mutex */
-	ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
-}
+#define cache_entry_cmp entry_cmp
+#define cache_entrydn_cmp entry_dn_cmp
+#define cache_entryid_cmp entry_id_cmp
 
 static int
 cache_entry_rdwr_lock(Entry *e, int rw)
 {
-	Debug( LDAP_DEBUG_ARGS, "entry_rdwr_%slock: ID: %ld\n",
+	Debug( LDAP_DEBUG_ARGS, "entry_rdwr_%slock: ID: %lu\n",
 		rw ? "w" : "r", e->e_id, 0);
 
 	if (rw)
@@ -91,7 +67,7 @@ cache_entry_rdwr_lock(Entry *e, int rw)
 static int
 cache_entry_rdwr_trylock(Entry *e, int rw)
 {
-	Debug( LDAP_DEBUG_ARGS, "entry_rdwr_%strylock: ID: %ld\n",
+	Debug( LDAP_DEBUG_ARGS, "entry_rdwr_%strylock: ID: %lu\n",
 		rw ? "w" : "r", e->e_id, 0);
 
 	if (rw)
@@ -103,7 +79,7 @@ cache_entry_rdwr_trylock(Entry *e, int rw)
 static int
 cache_entry_rdwr_unlock(Entry *e, int rw)
 {
-	Debug( LDAP_DEBUG_ARGS, "entry_rdwr_%sunlock: ID: %ld\n",
+	Debug( LDAP_DEBUG_ARGS, "entry_rdwr_%sunlock: ID: %lu\n",
 		rw ? "w" : "r", e->e_id, 0);
 
 	if (rw)
@@ -129,7 +105,12 @@ cache_entry_private_init( Entry*e )
 {
 	struct ldbm_entry_info *lei;
 
+#ifdef LDAP_DEBUG
+	assert( e->e_private == NULL );
+#endif
+
 	if( e->e_private != NULL ) {
+		/* this should never happen */
 		return 1;
 	}
 
@@ -137,6 +118,7 @@ cache_entry_private_init( Entry*e )
 
 	if( cache_entry_rdwr_init( e ) != 0 ) {
 		free( LEI(e) );
+		e->e_private = NULL;
 		return 1;
 	} 
 
@@ -148,9 +130,9 @@ cache_entry_private_destroy( Entry*e )
 {
 	struct ldbm_entry_info *lei;
 
-	if( e->e_private == NULL ) {
-		return 1;
-	}
+#ifdef LDAP_DEBUG
+	assert( e->e_private );
+#endif
 
 	cache_entry_rdwr_destroy( e );
 
@@ -159,41 +141,53 @@ cache_entry_private_destroy( Entry*e )
 	return 0;
 }
 
-static void
+void
 cache_return_entry_rw( struct cache *cache, Entry *e, int rw )
 {
-	Debug( LDAP_DEBUG_TRACE, "====> cache_return_entry_%s\n",
-		rw ? "w" : "r", 0, 0);
-
 	/* set cache mutex */
 	ldap_pvt_thread_mutex_lock( &cache->c_mutex );
 
+#ifdef LDAP_DEBUG
+	assert( e->e_private );
+#endif
+
 	cache_entry_rdwr_unlock(e, rw);
 
-	if ( --LEI(e)->lei_refcnt == 0 &&
-		LEI(e)->lei_state == ENTRY_STATE_DELETED )
-	{
-		cache_entry_private_destroy( e );
-		entry_free( e );
+	LEI(e)->lei_refcnt--;
+
+	if ( LEI(e)->lei_state == CACHE_ENTRY_CREATING ) {
+		Debug( LDAP_DEBUG_TRACE,
+			"====> cache_return_entry_%s( %lu ): created (%d)\n",
+			rw ? "w" : "r", e->e_id, LEI(e)->lei_refcnt );
+
+		LEI(e)->lei_state = CACHE_ENTRY_READY;
+
+	} else if ( LEI(e)->lei_state == CACHE_ENTRY_DELETED ) {
+		if( LEI(e)->lei_refcnt > 0 ) {
+			Debug( LDAP_DEBUG_TRACE,
+				"====> cache_return_entry_%s( %lu ): delete pending (%d)\n",
+				rw ? "w" : "r", e->e_id, LEI(e)->lei_refcnt );
+
+		} else {
+			Debug( LDAP_DEBUG_TRACE,
+				"====> cache_return_entry_%s( %lu ): deleted (%d)\n",
+				rw ? "w" : "r", e->e_id, LEI(e)->lei_refcnt );
+
+			cache_entry_private_destroy( e );
+			entry_free( e );
+		}
+
+	} else {
+		Debug( LDAP_DEBUG_TRACE,
+			"====> cache_return_entry_%s( %lu ): returned (%d)\n",
+			rw ? "w" : "r", e->e_id, LEI(e)->lei_refcnt);
 	}
 
+
 	/* free cache mutex */
 	ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
 }
 
-void
-cache_return_entry_r( struct cache *cache, Entry *e )
-{
-	cache_return_entry_rw(cache, e, 0);
-}
-
-void
-cache_return_entry_w( struct cache *cache, Entry *e )
-{
-	cache_return_entry_rw(cache, e, 1);
-}
-
-
 #define LRU_DELETE( cache, e ) { \
 	if ( LEI(e)->lei_lruprev != NULL ) { \
 		LEI(LEI(e)->lei_lruprev)->lei_lrunext = LEI(e)->lei_lrunext; \
@@ -229,7 +223,6 @@ int
 cache_add_entry_rw(
     struct cache	*cache,
     Entry		*e,
-    int			state,
 	int		rw
 )
 {
@@ -239,17 +232,14 @@ cache_add_entry_rw(
 	/* set cache mutex */
 	ldap_pvt_thread_mutex_lock( &cache->c_mutex );
 
-	if ( e->e_private != NULL ) {
-		Debug( LDAP_DEBUG_ANY,
-			"====> cache_add_entry: entry %20s id %lu already cached.\n",
-		    e->e_dn, e->e_id, 0 );
-		return( -1 );
-	}
+#ifdef LDAP_DEBUG
+	assert( e->e_private == NULL );
+#endif
 
 	if( cache_entry_private_init(e) != 0 ) {
 		Debug( LDAP_DEBUG_ANY,
-			"====> cache_add_entry: entry %20s id %lu: private init failed!\n",
-		    e->e_dn, e->e_id, 0 );
+			"====> cache_add_entry( %lu ): \"%s\": private init failed!\n",
+		    e->e_id, e->e_dn, 0 );
 		return( -1 );
 	}
 
@@ -257,8 +247,8 @@ cache_add_entry_rw(
 		cache_entrydn_cmp, avl_dup_error ) != 0 )
 	{
 		Debug( LDAP_DEBUG_TRACE,
-			"====> cache_add_entry: entry %20s id %lu already in dn cache\n",
-		    e->e_dn, e->e_id, 0 );
+			"====> cache_add_entry( %lu ): \"%s\": already in dn cache\n",
+		    e->e_id, e->e_dn, 0 );
 
 		cache_entry_private_destroy(e);
 
@@ -272,8 +262,9 @@ cache_add_entry_rw(
 		cache_entryid_cmp, avl_dup_error ) != 0 )
 	{
 		Debug( LDAP_DEBUG_ANY,
-			"====> entry %20s id %lu already in id cache\n",
-		    e->e_dn, e->e_id, 0 );
+			"====> cache_add_entry( %lu ): \"%s\": already in id cache\n",
+		    e->e_id, e->e_dn, 0 );
+
 
 		/* delete from dn tree inserted above */
 		if ( avl_delete( &cache->c_dntree, (caddr_t) e,
@@ -292,7 +283,9 @@ cache_add_entry_rw(
 
 	cache_entry_rdwr_lock( e, rw );
 
-	LEI(e)->lei_state = state;
+	/* put the entry into 'CREATING' state */
+	/* will be marked after when entry is returned */
+	LEI(e)->lei_state = CACHE_ENTRY_CREATING;
 	LEI(e)->lei_refcnt = 1;
 
 	/* lru */
@@ -327,7 +320,7 @@ cache_add_entry_rw(
 
 			/* delete from cache and lru q */
 			rc = cache_delete_entry_internal( cache, e );
-
+			cache_entry_private_destroy( e );
 			entry_free( e );
 		}
 	}
@@ -355,19 +348,16 @@ cache_update_entry(
 	/* set cache mutex */
 	ldap_pvt_thread_mutex_lock( &cache->c_mutex );
 
-	if ( e->e_private == NULL ) {
-		Debug( LDAP_DEBUG_ANY,
-			"====> cache_update_entry: entry %20s id %lu no private data.\n",
-		    e->e_dn, e->e_id, 0 );
-		return( -1 );
-	}
+#ifdef LDAP_DEBUG
+	assert( e->e_private );
+#endif
 
 	if ( avl_insert( &cache->c_dntree, (caddr_t) e,
 		cache_entrydn_cmp, avl_dup_error ) != 0 )
 	{
 		Debug( LDAP_DEBUG_TRACE,
-			"====> cache_add_entry: entry %20s id %lu already in dn cache\n",
-		    e->e_dn, e->e_id, 0 );
+			"====> cache_update_entry( %lu ): \"%s\": already in dn cache\n",
+		    e->e_id, e->e_dn, 0 );
 
 		/* free cache mutex */
 		ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
@@ -379,8 +369,8 @@ cache_update_entry(
 		cache_entryid_cmp, avl_dup_error ) != 0 )
 	{
 		Debug( LDAP_DEBUG_ANY,
-			"====> entry %20s id %lu already in id cache\n",
-		    e->e_dn, e->e_id, 0 );
+			"====> cache_update_entry( %lu ): \"%s\": already in id cache\n",
+		    e->e_id, e->e_dn, 0 );
 
 		/* delete from dn tree inserted above */
 		if ( avl_delete( &cache->c_dntree, (caddr_t) e,
@@ -395,6 +385,11 @@ cache_update_entry(
 		return( -1 );
 	}
 
+
+	/* put the entry into 'CREATING' state */
+	/* will be marked after when entry is returned */
+	LEI(e)->lei_state = CACHE_ENTRY_CREATING;
+
 	/* lru */
 	LRU_ADD( cache, e );
 	if ( ++cache->c_cursize > cache->c_maxsize ) {
@@ -427,7 +422,7 @@ cache_update_entry(
 
 			/* delete from cache and lru q */
 			rc = cache_delete_entry_internal( cache, e );
-
+			cache_entry_private_destroy( e );
 			entry_free( e );
 		}
 	}
@@ -468,20 +463,29 @@ cache_find_entry_dn2id(
 		 */
 		free(e.e_ndn);
 
-		Debug(LDAP_DEBUG_TRACE, "====> cache_find_entry_dn2id: found dn: %s\n",
-			dn, 0, 0);
-
+#ifdef LDAP_DEBUG
+		assert( ep->e_private );
+#endif
 		/*
 		 * entry is deleted or not fully created yet
 		 */
-		if ( LEI(ep)->lei_state == ENTRY_STATE_DELETED ||
-			LEI(ep)->lei_state == ENTRY_STATE_CREATING )
-		{
+		if ( LEI(ep)->lei_state != CACHE_ENTRY_READY ) {
+#ifdef LDAP_DEBUG
+			assert(LEI(ep)->lei_state != CACHE_ENTRY_UNDEFINED);
+#endif
+			Debug(LDAP_DEBUG_TRACE,
+				"====> cache_find_entry_dn2id(\"%s\"): %lu (not ready) %d\n",
+				dn, ep->e_id, LEI(ep)->lei_state);
+
 			/* free cache mutex */
 			ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
 			return( NOID );
 		}
 
+		Debug(LDAP_DEBUG_TRACE,
+			"====> cache_find_entry_dn2id(\"%s\"): %lu\n",
+			dn, ep->e_id, 0);
+
 		/* lru */
 		LRU_DELETE( cache, ep );
 		LRU_ADD( cache, ep );
@@ -526,21 +530,29 @@ try_again:
 	if ( (ep = (Entry *) avl_find( cache->c_idtree, (caddr_t) &e,
 		cache_entryid_cmp )) != NULL )
 	{
-		Debug(LDAP_DEBUG_TRACE,
-			"====> cache_find_entry_dn2id: found id: %ld rw: %d\n",
-			id, rw, 0);
-
+#ifdef LDAP_DEBUG
+		assert( ep->e_private );
+#endif
 		/*
 		 * entry is deleted or not fully created yet
 		 */
-		if ( LEI(ep)->lei_state == ENTRY_STATE_DELETED ||
-			LEI(ep)->lei_state == ENTRY_STATE_CREATING )
-		{
+		if ( LEI(ep)->lei_state != CACHE_ENTRY_READY ) {
+#ifdef LDAP_DEBUG
+			assert(LEI(ep)->lei_state != CACHE_ENTRY_UNDEFINED);
+#endif
+			Debug(LDAP_DEBUG_TRACE,
+				"====> cache_find_entry_id( %lu ): %lu (not ready) %d\n",
+				id, ep->e_id, LEI(ep)->lei_state);
+
 			/* free cache mutex */
 			ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
 			return( NULL );
 		}
 
+		Debug(LDAP_DEBUG_TRACE,
+			"====> cache_find_entry_id( %lu, %s ) \"%s\" (found)\n",
+			id, rw ? "w" : "r", ep->e_dn);
+
 		/* acquire reader lock */
 		if ( cache_entry_rdwr_trylock(ep, rw) == LDAP_PVT_THREAD_EBUSY ) {
 			/* could not acquire entry lock...
@@ -591,11 +603,16 @@ cache_delete_entry(
 {
 	int	rc;
 
-	Debug( LDAP_DEBUG_TRACE, "====> cache_delete_entry:\n", 0, 0, 0 );
-
 	/* set cache mutex */
 	ldap_pvt_thread_mutex_lock( &cache->c_mutex );
 
+#ifdef LDAP_DEBUG
+	assert( e->e_private );
+#endif
+
+	Debug( LDAP_DEBUG_TRACE, "====> cache_delete_entry( %lu )\n",
+		e->e_id, 0, 0 );
+
 	rc = cache_delete_entry_internal( cache, e );
 
 	/* free cache mutex */
@@ -636,7 +653,7 @@ cache_delete_entry_internal(
 	/*
 	 * flag entry to be freed later by a call to cache_return_entry()
 	 */
-	LEI(e)->lei_state = ENTRY_STATE_DELETED;
+	LEI(e)->lei_state = CACHE_ENTRY_DELETED;
 
 	return( 0 );
 }
@@ -650,13 +667,13 @@ lru_print( struct cache *cache )
 
 	fprintf( stderr, "LRU queue (head to tail):\n" );
 	for ( e = cache->c_lruhead; e != NULL; e = LEI(e)->lei_lrunext ) {
-		fprintf( stderr, "\tdn %20s id %lu refcnt %d\n", e->e_dn,
-		    e->e_id, LEI(e)->lei_refcnt );
+		fprintf( stderr, "\tdn \"%20s\" id %lu refcnt %d\n",
+			e->e_dn, e->e_id, LEI(e)->lei_refcnt );
 	}
 	fprintf( stderr, "LRU queue (tail to head):\n" );
 	for ( e = cache->c_lrutail; e != NULL; e = LEI(e)->lei_lruprev ) {
-		fprintf( stderr, "\tdn %20s id %lu refcnt %d\n", e->e_dn,
-		    e->e_id, LEI(e)->lei_refcnt );
+		fprintf( stderr, "\tdn \"%20s\" id %lu refcnt %d\n",
+			e->e_dn, e->e_id, LEI(e)->lei_refcnt );
 	}
 }
 
diff --git a/servers/slapd/back-ldbm/dn2id.c b/servers/slapd/back-ldbm/dn2id.c
index 3772b90281..38901c0249 100644
--- a/servers/slapd/back-ldbm/dn2id.c
+++ b/servers/slapd/back-ldbm/dn2id.c
@@ -153,7 +153,7 @@ dn2id_delete(
  * entry.
  */
 
-static Entry *
+Entry *
 dn2entry_rw(
     Backend	*be,
     char	*dn,
@@ -208,25 +208,3 @@ dn2entry_rw(
 	return( NULL );
 }
 
-Entry *
-dn2entry_r(
-	Backend	*be,
-	char	*dn,
-	char	**matched
-)
-{
-	return( dn2entry_rw( be, dn, matched, 0 ) );
-}
-
-Entry *
-dn2entry_w(
-	Backend	*be,
-	char	*dn,
-	char	**matched
-)
-{
-	return( dn2entry_rw( be, dn, matched, 1 ) );
-}
-
-
-
diff --git a/servers/slapd/back-ldbm/id2entry.c b/servers/slapd/back-ldbm/id2entry.c
index dad31af444..1e38d31a22 100644
--- a/servers/slapd/back-ldbm/id2entry.c
+++ b/servers/slapd/back-ldbm/id2entry.c
@@ -51,9 +51,6 @@ id2entry_add( Backend *be, Entry *e )
 
 	ldbm_cache_close( be, db );
 
-	/* XXX entry should have already been added to the cache */
-	/* (void) cache_add_entry_rw( &li->li_cache, e, 0 ); */
-
 	Debug( LDAP_DEBUG_TRACE, "<= id2entry_add %d\n", rc, 0, 0 );
 
 	return( rc );
@@ -102,7 +99,7 @@ id2entry_delete( Backend *be, Entry *e )
 	return( rc );
 }
 
-/* XXX returns entry with reader/writer lock */
+/* returns entry with reader/writer lock */
 Entry *
 id2entry_rw( Backend *be, ID id, int rw )
 {
@@ -118,8 +115,8 @@ id2entry_rw( Backend *be, ID id, int rw )
 		rw ? "w" : "r", id, 0 );
 
 	if ( (e = cache_find_entry_id( &li->li_cache, id, rw )) != NULL ) {
-		Debug( LDAP_DEBUG_TRACE, "<= id2entry_%s 0x%lx (cache)\n",
-			rw ? "w" : "r", (unsigned long)e, 0 );
+		Debug( LDAP_DEBUG_TRACE, "<= id2entry_%s( %ld ) 0x%lx (cache)\n",
+			rw ? "w" : "r", id, (unsigned long) e );
 		return( e );
 	}
 
@@ -153,27 +150,22 @@ id2entry_rw( Backend *be, ID id, int rw )
 		return( NULL );
 	}
 
-	e->e_id = id;
+	if ( e->e_id != id ) {
+		Debug( LDAP_DEBUG_TRACE, "<= id2entry_%s( %ld ) (wrong id %ld on disk)\n",
+			rw ? "w" : "r", id, e->e_id );
+		entry_free( e );
+		return( NULL );
+	}
 
-	if( cache_add_entry_rw( &li->li_cache, e, 0, rw ) != 0 ) {
+	if( cache_add_entry_rw( &li->li_cache, e, rw ) != 0 ) {
 		Debug( LDAP_DEBUG_TRACE, "<= id2entry_%s( %ld ) (cache add failed)\n",
 			rw ? "w" : "r", id, 0 );
+		entry_free( e );
+		return NULL;
 	}
 
-	Debug( LDAP_DEBUG_TRACE, "<= id2entry_%s( %ld ) (disk)\n",
-		rw ? "w" : "r", id, 0 );
-	return( e );
-}
-
-Entry *
-id2entry_r( Backend *be, ID id )
-{
-	return( id2entry_rw( be, id, 0 ) );
-}
+	Debug( LDAP_DEBUG_TRACE, "<= id2entry_%s( %ld ) 0x%lx (disk)\n",
+		rw ? "w" : "r", id, (unsigned long) e );
 
-Entry *
-id2entry_w( Backend *be, ID id )
-{
-	return( id2entry_rw( be, id, 1 ) );
+	return( e );
 }
-
diff --git a/servers/slapd/back-ldbm/modrdn.c b/servers/slapd/back-ldbm/modrdn.c
index 3c8c2f8511..f6ec2248fd 100644
--- a/servers/slapd/back-ldbm/modrdn.c
+++ b/servers/slapd/back-ldbm/modrdn.c
@@ -145,7 +145,6 @@ ldbm_back_modrdn(
 	free( e->e_ndn );
 	e->e_dn = new_dn;
 	e->e_ndn = new_ndn;
-
 	(void) cache_update_entry( &li->li_cache, e );
 
 	/* 
diff --git a/servers/slapd/back-ldbm/proto-back-ldbm.h b/servers/slapd/back-ldbm/proto-back-ldbm.h
index a0abc0d867..ef7261e76a 100644
--- a/servers/slapd/back-ldbm/proto-back-ldbm.h
+++ b/servers/slapd/back-ldbm/proto-back-ldbm.h
@@ -34,12 +34,12 @@ void attr_index_config LDAP_P(( struct ldbminfo *li, char *fname, int lineno,
  * cache.c
  */
 
-void cache_set_state LDAP_P(( struct cache *cache, Entry *e, int state ));
-void cache_return_entry_r LDAP_P(( struct cache *cache, Entry *e ));
-void cache_return_entry_w LDAP_P(( struct cache *cache, Entry *e ));
-int cache_add_entry_rw LDAP_P(( struct cache *cache, Entry *e,
-	int state, int rw ));
+int cache_add_entry_rw LDAP_P(( struct cache *cache, Entry *e, int rw ));
 int cache_update_entry LDAP_P(( struct cache *cache, Entry *e ));
+void cache_return_entry_rw LDAP_P(( struct cache *cache, Entry *e, int rw ));
+#define cache_return_entry_r(c, e) cache_return_entry_rw((c), (e), 0)
+#define cache_return_entry_w(c, e) cache_return_entry_rw((c), (e), 1)
+
 ID cache_find_entry_dn2id LDAP_P(( Backend *be, struct cache *cache, char *dn ));
 Entry * cache_find_entry_id LDAP_P(( struct cache *cache, ID id, int rw ));
 int cache_delete_entry LDAP_P(( struct cache *cache, Entry *e ));
@@ -64,8 +64,10 @@ int ldbm_cache_delete LDAP_P(( struct dbcache *db, Datum key ));
 int dn2id_add LDAP_P(( Backend *be, char *dn, ID id ));
 ID dn2id LDAP_P(( Backend *be, char *dn ));
 int dn2id_delete LDAP_P(( Backend *be, char *dn ));
-Entry * dn2entry_r LDAP_P(( Backend *be, char *dn, char **matched ));
-Entry * dn2entry_w LDAP_P(( Backend *be, char *dn, char **matched ));
+
+Entry * dn2entry_rw LDAP_P(( Backend *be, char *dn, char **matched, int rw ));
+#define dn2entry_r(be, dn, m) dn2entry_rw((be), (dn), (m), 0)
+#define dn2entry_w(be, dn, m) dn2entry_rw((be), (dn), (m), 1)
 
 /*
  * filterindex.c
@@ -87,9 +89,10 @@ int has_children LDAP_P(( Backend *be, Entry *p ));
 
 int id2entry_add LDAP_P(( Backend *be, Entry *e ));
 int id2entry_delete LDAP_P(( Backend *be, Entry *e ));
+
 Entry * id2entry_rw LDAP_P(( Backend *be, ID id, int rw )); 
-Entry * id2entry_r LDAP_P(( Backend *be, ID id ));
-Entry * id2entry_w LDAP_P(( Backend *be, ID id ));
+#define id2entry_r(be, id)	id2entry_rw((be), (id), 0)
+#define id2entry_w(be, id)	id2entry_rw((be), (id), 1)
 
 /*
  * idl.c
diff --git a/servers/slapd/entry.c b/servers/slapd/entry.c
index 3755272d1f..7099931084 100644
--- a/servers/slapd/entry.c
+++ b/servers/slapd/entry.c
@@ -237,3 +237,35 @@ entry_free( Entry *e )
 	free( e );
 }
 
+/*
+ * These routines are used only by Backend.
+ *
+ * the Entry has three entry points (ways to find things):
+ *
+ * 	by entry	e.g., if you already have an entry from the cache
+ *			and want to delete it. (really by entry ptr)
+ *	by dn		e.g., when looking for the base object of a search
+ *	by id		e.g., for search candidates
+ *
+ * these correspond to three different avl trees that are maintained.
+ */
+
+int
+entry_cmp( Entry *e1, Entry *e2 )
+{
+	return( e1 < e2 ? -1 : (e1 > e2 ? 1 : 0) );
+}
+
+int
+entry_dn_cmp( Entry *e1, Entry *e2 )
+{
+	/* compare their normalized UPPERCASED dn's */
+	return( strcmp( e1->e_ndn, e2->e_ndn ) );
+}
+
+int
+entry_id_cmp( Entry *e1, Entry *e2 )
+{
+	return( e1->e_id < e2->e_id ? -1 : (e1->e_id > e2->e_id ? 1 : 0) );
+}
+
diff --git a/servers/slapd/proto-slap.h b/servers/slapd/proto-slap.h
index a3f8b820c8..8fb59e2139 100644
--- a/servers/slapd/proto-slap.h
+++ b/servers/slapd/proto-slap.h
@@ -132,14 +132,9 @@ Entry * str2entry LDAP_P(( char	*s ));
 char * entry2str LDAP_P(( Entry *e, int *len, int printid ));
 void entry_free LDAP_P(( Entry *e ));
 
-int entry_rdwr_lock LDAP_P(( Entry *e, int rw ));
-int entry_rdwr_rlock LDAP_P(( Entry *e ));
-int entry_rdwr_wlock LDAP_P(( Entry *e ));
-int entry_rdwr_trylock LDAP_P(( Entry *e, int rw ));
-int entry_rdwr_unlock LDAP_P(( Entry *e, int rw ));
-int entry_rdwr_runlock LDAP_P(( Entry *e ));
-int entry_rdwr_wunlock LDAP_P(( Entry *e ));
-int entry_rdwr_init LDAP_P(( Entry *e ));
+int entry_cmp LDAP_P(( Entry *a, Entry *b ));
+int entry_dn_cmp LDAP_P(( Entry *a, Entry *b ));
+int entry_id_cmp LDAP_P(( Entry *a, Entry *b ));
 
 /*
  * filter.c