ITS#8324 fix for WRITEMAP

We called FlushViewOfFile with (map,mapsize) which worked fine
when we had allocated the entire map already. Now we have to make
sure to only flush as much as was actually written. Add a numpgs
argument to tell how much to flush in env_sync0().

libraries/liblmdb/mdb.c

@@ -2643,7 +2643,7 @@ fail:
 }
 
 int
-mdb_env_sync(MDB_env *env, int force)
+mdb_env_sync0(MDB_env *env, int force, pgno_t numpgs)
 {
 	int rc = 0;
 	if (env->me_flags & MDB_RDONLY)
@@ -2652,7 +2652,7 @@ mdb_env_sync(MDB_env *env, int force)
 		if (env->me_flags & MDB_WRITEMAP) {
 			int flags = ((env->me_flags & MDB_MAPASYNC) && !force)
 				? MS_ASYNC : MS_SYNC;
-			if (MDB_MSYNC(env->me_map, env->me_mapsize, flags))
+			if (MDB_MSYNC(env->me_map, env->me_psize * numpgs, flags))
 				rc = ErrCode();
 #ifdef _WIN32
 			else if (flags == MS_SYNC && MDB_FDATASYNC(env->me_fd))
@@ -2672,6 +2672,13 @@ mdb_env_sync(MDB_env *env, int force)
 	return rc;
 }
 
+int
+mdb_env_sync(MDB_env *env, int force)
+{
+	MDB_meta *m = mdb_env_pick_meta(env);
+	return mdb_env_sync0(env, force, m->mm_last_pg+1);
+}
+
 /** Back up parent txn's cursors, then grab the originals for tracking */
 static int
 mdb_cursor_shadow(MDB_txn *src, MDB_txn *dst)
@@ -3813,7 +3820,7 @@ mdb_txn_commit(MDB_txn *txn)
 	if ((rc = mdb_page_flush(txn, 0)))
 		goto fail;
 	if (!F_ISSET(txn->mt_flags, MDB_TXN_NOSYNC) &&
-		(rc = mdb_env_sync(env, 0)))
+		(rc = mdb_env_sync0(env, 0, txn->mt_next_pgno)))
 		goto fail;
 	if ((rc = mdb_env_write_meta(txn)))
 		goto fail;