Add envflags for MDB config

allows setting writemap and some other useful flags

doc/man/man5/slapd-mdb.5

@@ -53,6 +53,48 @@ associated indexes live.
 A separate directory must be specified for each database.
 The default is
 .BR LOCALSTATEDIR/openldap\-data .
+.TP
+\fBenvflags \fR{\fBnosync\fR,\fBnometasync\fR,\fBwritemap\fR,\fBmapasync\fR}
+Specify flags for finer-grained control of the MDB library's operation.
+.RS
+.TP
+.B nosync
+This is exactly the same as the
+.I dbnosync
+directive.
+.RE
+.RS
+.TP
+.B nometasync
+Flush the data on a commit, but skip the sync of the meta page. This mode is
+slightly faster than doing a full sync, but can potentially lose the last
+committed transaction if the operating system crashes. If both
+.I nometasync
+and
+.I nosync
+are set, the
+.I nosync
+flag takes precedence.
+.RE
+.RS
+.TP
+.B writemap
+Use a writable memory map instead of just read-only. This speeds up write operations
+but makes the database vulnerable to corruption in case any bugs in slapd
+cause stray writes into the mmap region.
+.RE
+.RS
+.TP
+.B mapasync
+When using a writable memory map and performing flushes on each commit, use an
+asynchronous flush instead of a synchronous flush (the default). This option
+has no effect if
+.I writemap
+has not been set. It also has no effect if
+.I nosync
+is set.
+.RE
+
 .TP
 \fBindex \fR{\fI<attrlist>\fR|\fBdefault\fR} [\fBpres\fR,\fBeq\fR,\fBapprox\fR,\fBsub\fR,\fI<special>\fR]
 Specify the indexes to maintain for the given attribute (or

servers/slapd/back-mdb/config.c

@@ -34,6 +34,7 @@ enum {
 	MDB_CHKPT = 1,
 	MDB_DIRECTORY,
 	MDB_DBNOSYNC,
+	MDB_ENVFLAGS,
 	MDB_INDEX,
 	MDB_MAXREADERS,
 	MDB_MAXSIZE,
@@ -55,6 +56,10 @@ static ConfigTable mdbcfg[] = {
 		mdb_cf_gen, "( OLcfgDbAt:1.4 NAME 'olcDbNoSync' "
 			"DESC 'Disable synchronous database writes' "
 			"SYNTAX OMsBoolean SINGLE-VALUE )", NULL, NULL },
+	{ "envflags", "flags", 2, 0, 0, ARG_MAGIC|MDB_ENVFLAGS,
+		mdb_cf_gen, "( OLcfgDbAt:12.3 NAME 'olcDbEnvFlags' "
+			"DESC 'Database environment flags' "
+			"SYNTAX OMsDirectoryString )", NULL, NULL },
 	{ "index", "attr> <[pres,eq,approx,sub]", 2, 3, 0, ARG_MAGIC|MDB_INDEX,
 		mdb_cf_gen, "( OLcfgDbAt:0.2 NAME 'olcDbIndex' "
 		"DESC 'Attribute index parameters' "
@@ -87,13 +92,21 @@ static ConfigOCs mdbocs[] = {
 		"DESC 'MDB backend configuration' "
 		"SUP olcDatabaseConfig "
 		"MUST olcDbDirectory "
-		"MAY ( olcDbCheckpoint $ "
+		"MAY ( olcDbCheckpoint $ olcDbEnvFlags "
 		"olcDbNoSync $ olcDbIndex $ olcDbMaxReaders $ olcDbMaxsize $ "
 		"olcDbMode $ olcDbSearchStack ) )",
 		 	Cft_Database, mdbcfg },
 	{ NULL, 0, NULL }
 };
 
+static slap_verbmasks mdb_envflags[] = {
+	{ BER_BVC("nosync"),	MDB_NOSYNC },
+	{ BER_BVC("nometasync"),	MDB_NOMETASYNC },
+	{ BER_BVC("writemap"),	MDB_WRITEMAP },
+	{ BER_BVC("mapasync"),	MDB_MAPASYNC },
+	{ BER_BVNULL, 0 }
+};
+
 /* perform periodic syncs */
 static void *
 mdb_checkpoint( void *ctx, void *arg )
@@ -293,6 +306,13 @@ mdb_cf_gen( ConfigArgs *c )
 				c->value_int = 1;
 			break;
 
+		case MDB_ENVFLAGS:
+			if ( mdb->mi_dbenv_flags ) {
+				mask_to_verbs( mdb_envflags, mdb->mi_dbenv_flags, &c->rvalue_vals );
+			}
+			if ( !c->rvalue_vals ) rc = 1;
+			break;
+
 		case MDB_INDEX:
 			mdb_attr_index_unparse( mdb, &c->rvalue_vals );
 			if ( !c->rvalue_vals ) rc = 1;
@@ -349,7 +369,31 @@ mdb_cf_gen( ConfigArgs *c )
 			break;
 		case MDB_DBNOSYNC:
 			mdb_env_set_flags( mdb->mi_dbenv, MDB_NOSYNC, 0 );
+			mdb->mi_dbenv_flags &= ~MDB_NOSYNC;
+			break;
+
+		case MDB_ENVFLAGS:
+			if ( c->valx == -1 ) {
+				int i;
+				for ( i=0; mdb_envflags[i].mask; i++) {
+					if ( mdb->mi_dbenv_flags & mdb_envflags[i].mask ) {
+						/* not all flags are runtime resettable */
+						rc = mdb_env_set_flags( mdb->mi_dbenv, mdb_envflags[i].mask, 0 );
+						if ( rc )
+							break;
+						mdb->mi_dbenv_flags ^= mdb_envflags[i].mask;
+					}
+				}
+			} else {
+				int i = verb_to_mask( c->line, mdb_envflags );
+				if ( mdb_envflags[i].mask & mdb->mi_dbenv_flags ) {
+					rc = mdb_env_set_flags( mdb->mi_dbenv, mdb_envflags[i].mask, 0 );
+					if ( !rc )
+						mdb->mi_dbenv_flags ^= mdb_envflags[i].mask;
+				}
+			}
 			break;
+
 		case MDB_INDEX:
 			if ( c->valx == -1 ) {
 				int i;
@@ -530,6 +574,24 @@ mdb_cf_gen( ConfigArgs *c )
 		}
 		break;
 
+	case MDB_ENVFLAGS: {
+		int i, j;
+		for ( i=1; i<c->argc; i++ ) {
+			j = verb_to_mask( c->argv[i], mdb_envflags );
+			if ( mdb_envflags[j].mask ) {
+				if ( mdb->mi_flags & MDB_IS_OPEN )
+					rc = mdb_env_set_flags( mdb->mi_dbenv, mdb_envflags[j].mask, 1 );
+				else
+					rc = 0;
+				if ( rc )
+					break;
+				else
+					mdb->mi_dbenv_flags |= mdb_envflags[i].mask;
+			}
+		}
+		}
+		break;
+
 	case MDB_INDEX:
 		rc = mdb_attr_index_config( mdb, c->fname, c->lineno,
 			c->argc - 1, &c->argv[1], &c->reply);

servers/slapd/back-mdb/init.c

@@ -166,7 +166,7 @@ mdb_db_open( BackendDB *be, ConfigReply *cr )
 	flags = mdb->mi_dbenv_flags;
 
 	if ( slapMode & SLAP_TOOL_QUICK )
-		flags |= MDB_NOSYNC;
+		flags |= MDB_NOSYNC|MDB_WRITEMAP;
 
 	if ( slapMode & SLAP_TOOL_READONLY)
 		flags |= MDB_RDONLY;