From e562f53e10b07ed439d3dae934198d3e9cdb9834 Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@symas.com>
Date: Sun, 8 Jul 2012 18:24:11 -0700
Subject: [PATCH] Drop me_toggle, unused

---
 libraries/libmdb/mdb.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/libraries/libmdb/mdb.c b/libraries/libmdb/mdb.c
index 38825e9..983c75c 100644
--- a/libraries/libmdb/mdb.c
+++ b/libraries/libmdb/mdb.c
@@ -521,11 +521,6 @@ typedef struct MDB_txbody {
 		 *	when readers release their slots.
 		 */
 	unsigned	mtb_numreaders;
-		/**	The ID of the most recent meta page in the database.
-		 *	This is recorded here only for convenience; the value can always
-		 *	be determined by reading the main database meta pages.
-		 */
-	uint32_t	mtb_me_toggle;
 } MDB_txbody;
 
 	/** The actual reader table definition. */
@@ -538,7 +533,6 @@ typedef struct MDB_txninfo {
 #define mti_rmname	mt1.mtb.mtb_rmname
 #define mti_txnid	mt1.mtb.mtb_txnid
 #define mti_numreaders	mt1.mtb.mtb_numreaders
-#define mti_me_toggle	mt1.mtb.mtb_me_toggle
 		char pad[(sizeof(MDB_txbody)+CACHELINE-1) & ~(CACHELINE-1)];
 	} mt1;
 	union {
@@ -1575,8 +1569,9 @@ mdb_txn_renew0(MDB_txn *txn)
 			r = &env->me_txns->mti_readers[i];
 			pthread_setspecific(env->me_txkey, r);
 		}
-		txn->mt_toggle = env->me_txns->mti_me_toggle;
 		txn->mt_txnid = env->me_txns->mti_txnid;
+		txn->mt_toggle = txn->mt_txnid & 1;
+		txn->mt_next_pgno = env->me_metas[txn->mt_toggle]->mm_last_pg+1;
 		/* This happens if a different process was the
 		 * last writer to the DB.
 		 */
@@ -1588,6 +1583,8 @@ mdb_txn_renew0(MDB_txn *txn)
 		LOCK_MUTEX_W(env);
 
 		txn->mt_txnid = env->me_txns->mti_txnid;
+		txn->mt_toggle = txn->mt_txnid & 1;
+		txn->mt_next_pgno = env->me_metas[txn->mt_toggle]->mm_last_pg+1;
 		if (env->me_wtxnid < txn->mt_txnid)
 			mt_dbflag = DB_STALE;
 		txn->mt_txnid++;
@@ -1595,14 +1592,12 @@ mdb_txn_renew0(MDB_txn *txn)
 		if (txn->mt_txnid == mdb_debug_start)
 			mdb_debug = 1;
 #endif
-		txn->mt_toggle = env->me_txns->mti_me_toggle;
 		txn->mt_u.dirty_list = env->me_dirty_list;
 		txn->mt_u.dirty_list[0].mid = 0;
 		txn->mt_free_pgs = env->me_free_pgs;
 		txn->mt_free_pgs[0] = 0;
 		env->me_txn = txn;
 	}
-	txn->mt_next_pgno = env->me_metas[txn->mt_toggle]->mm_last_pg+1;
 
 	/* Copy the DB arrays */
 	LAZY_RWLOCK_RDLOCK(&env->me_dblock);
@@ -2394,7 +2389,6 @@ mdb_env_write_meta(MDB_txn *txn)
 	 * how stale their view of these values is.
 	 */
 	LAZY_MUTEX_LOCK(&env->me_txns->mti_mutex);
-	txn->mt_env->me_txns->mti_me_toggle = toggle;
 	txn->mt_env->me_txns->mti_txnid = txn->mt_txnid;
 	LAZY_MUTEX_UNLOCK(&env->me_txns->mti_mutex);
 
@@ -2598,7 +2592,6 @@ mdb_env_share_locks(MDB_env *env)
 {
 	int toggle = mdb_env_pick_meta(env);
 
-	env->me_txns->mti_me_toggle = toggle;
 	env->me_txns->mti_txnid = env->me_metas[toggle]->mm_txnid;
 
 #ifdef _WIN32
@@ -2916,7 +2909,6 @@ mdb_env_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
 		env->me_txns->mti_magic = MDB_MAGIC;
 		env->me_txns->mti_txnid = 0;
 		env->me_txns->mti_numreaders = 0;
-		env->me_txns->mti_me_toggle = 0;
 
 	} else {
 		if (env->me_txns->mti_magic != MDB_MAGIC) {