From 60458c53566a6fe188ac08eaaa267d44b21737fc Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@openldap.org>
Date: Wed, 20 May 2026 16:24:35 +0100
Subject: [PATCH] ITS#10511 slapd-mdb: add dbpagesize config option

---
 doc/man/man5/slapd-mdb.5          |  9 +++++++++
 servers/slapd/back-mdb/back-mdb.h |  2 ++
 servers/slapd/back-mdb/config.c   |  8 +++++++-
 servers/slapd/back-mdb/init.c     | 11 +++++++++++
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/doc/man/man5/slapd-mdb.5 b/doc/man/man5/slapd-mdb.5
index d2a88b6152..844f0728ab 100644
--- a/doc/man/man5/slapd-mdb.5
+++ b/doc/man/man5/slapd-mdb.5
@@ -58,6 +58,15 @@ flushed, some number of transactions may be lost.
 By default, a full data flush/sync is performed when each
 transaction is committed.
 .TP
+.B dbpagesize \ <bytes>
+Specify the page size to use for the database, in bytes. The default
+depends on the underlying filesystem's block size (typically 4096 or 8192).
+The value must be a power of two and the maximum is 65536.
+This setting usually should not need to be changed,
+but setting a larger pagesize also increases the maximum length of keys
+so it may be useful to support longer values when \fBmultival\fP is used.
+This setting only takes effect when a database is being newly created.
+.TP
 .BI directory \ <directory>
 Specify the directory where the LMDB files containing this database and
 associated indexes live.
diff --git a/servers/slapd/back-mdb/back-mdb.h b/servers/slapd/back-mdb/back-mdb.h
index 36b5638e42..d27417f356 100644
--- a/servers/slapd/back-mdb/back-mdb.h
+++ b/servers/slapd/back-mdb/back-mdb.h
@@ -121,6 +121,8 @@ struct mdb_info {
 		/* less than this many values in an attr goes
 		 * back into main blob */
 
+	int mi_pagesize;
+
 	MDB_dbi	mi_dbis[MDB_NDB];
 	AttributeDescription *mi_ads[MDB_MAXADS];
 	int mi_adxs[MDB_MAXADS];
diff --git a/servers/slapd/back-mdb/config.c b/servers/slapd/back-mdb/config.c
index 0721d48ed6..80f4d32052 100644
--- a/servers/slapd/back-mdb/config.c
+++ b/servers/slapd/back-mdb/config.c
@@ -71,6 +71,12 @@ static ConfigTable mdbcfg[] = {
 			"DESC 'Disable synchronous database writes' "
 			"EQUALITY booleanMatch "
 			"SYNTAX OMsBoolean SINGLE-VALUE )", NULL, NULL },
+	{ "dbpagesize", "size", 2, 2, 0, ARG_UINT|ARG_OFFSET,
+		(void *)offsetof(struct mdb_info, mi_pagesize),
+			"( OLcfgDbAt:1.15 NAME 'olcDbPageSize' "
+			"DESC 'Page size in bytes, in range 256-65536' "
+			"EQUALITY integerMatch "
+			"SYNTAX OMsInteger 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' "
@@ -153,7 +159,7 @@ static ConfigOCs mdbocs[] = {
 		"MAY ( olcDbCheckpoint $ olcDbEnvFlags "
 		"$ olcDbNoSync $ olcDbIndex $ olcDbMaxReaders $ olcDbMaxSize "
 		"$ olcDbMode $ olcDbSearchStack $ olcDbMaxEntrySize $ olcDbRtxnSize "
-		"$ olcDbMultival "
+		"$ olcDbMultival $ olcDbPageSize "
 #ifdef MDB_ENCRYPT
 		"$ olcDbCryptoModule $ olcDbPassphrase "
 #endif
diff --git a/servers/slapd/back-mdb/init.c b/servers/slapd/back-mdb/init.c
index 0767bdfafe..82dcabbcce 100644
--- a/servers/slapd/back-mdb/init.c
+++ b/servers/slapd/back-mdb/init.c
@@ -126,6 +126,17 @@ mdb_db_open( BackendDB *be, ConfigReply *cr )
 		goto fail;
 	}
 
+	if ( mdb->mi_pagesize ) {
+		rc = mdb_env_set_pagesize( mdb->mi_dbenv, mdb->mi_pagesize );
+		if ( rc ) {
+			Debug( LDAP_DEBUG_ANY,
+				LDAP_XSTRING(mdb_db_open) ": database \"%s\": "
+				"mdb_env_set_pagesize failed: %s (%d).\n",
+				be->be_suffix[0].bv_val, mdb_strerror(rc), rc );
+			goto fail;
+		}
+	}
+
 #ifdef MDB_ENCRYPT
 	if ( mdb->mi_dbenv_encfuncs ) {
 		mdb_modsetup( mdb->mi_dbenv, mdb->mi_dbenv_encfuncs, mdb->mi_dbenv_enckey );