From: Howard Chu <hyc@openldap.org>
Date: Thu, 13 Dec 2012 15:13:39 +0000 (-0800)
Subject: Get MDB txn before acquiring a CSN
X-Git-Url: https://git.sur5r.net/?a=commitdiff_plain;h=d3087229d5c8a617b97a17514c1cf0b1019eaf43;p=openldap

Get MDB txn before acquiring a CSN

Since MDB writes are fully serialized in txn_begin, we can use CSNs as
commit sequence numbers, not just change sequence numbers. This will
prevent most instances of out-of-order writes, so syncprov will almost
never need to transmit a change without a cookieCSN. (Out-of-order is
still possible, if the write was received via syncrepl.)
---

diff --git a/servers/slapd/back-mdb/add.c b/servers/slapd/back-mdb/add.c
index 4192a3cc79..40a9e5c96a 100644
--- a/servers/slapd/back-mdb/add.c
+++ b/servers/slapd/back-mdb/add.c
@@ -101,6 +101,19 @@ txnReturn:
 		goto return_results;
 	}
 
+	/* begin transaction */
+	rs->sr_err = mdb_opinfo_get( op, mdb, 0, &moi );
+	rs->sr_text = NULL;
+	if( rs->sr_err != 0 ) {
+		Debug( LDAP_DEBUG_TRACE,
+			LDAP_XSTRING(mdb_add) ": txn_begin failed: %s (%d)\n",
+			mdb_strerror(rs->sr_err), rs->sr_err, 0 );
+		rs->sr_err = LDAP_OTHER;
+		rs->sr_text = "internal error";
+		goto return_results;
+	}
+	txn = moi->moi_txn;
+
 	/* add opattrs to shadow as well, only missing attrs will actually
 	 * be added; helps compatibility with older OL versions */
 	rs->sr_err = slap_add_opattrs( op, &rs->sr_text, textbuf, textlen, 1 );
@@ -120,20 +133,6 @@ txnReturn:
 
 	subentry = is_entry_subentry( op->ora_e );
 
-	/* begin transaction */
-	rs->sr_err = mdb_opinfo_get( op, mdb, 0, &moi );
-	rs->sr_text = NULL;
-	if( rs->sr_err != 0 ) {
-		Debug( LDAP_DEBUG_TRACE,
-			LDAP_XSTRING(mdb_add) ": txn_begin failed: %s (%d)\n",
-			mdb_strerror(rs->sr_err), rs->sr_err, 0 );
-		rs->sr_err = LDAP_OTHER;
-		rs->sr_text = "internal error";
-		goto return_results;
-	}
-
-	txn = moi->moi_txn;
-
 	/*
 	 * Get the parent dn and see if the corresponding entry exists.
 	 */
diff --git a/servers/slapd/back-mdb/delete.c b/servers/slapd/back-mdb/delete.c
index 49d5e352a9..eb9bd2dd72 100644
--- a/servers/slapd/back-mdb/delete.c
+++ b/servers/slapd/back-mdb/delete.c
@@ -90,16 +90,6 @@ txnReturn:
 
 	ctrls[num_ctrls] = 0;
 
-	/* allocate CSN */
-	if ( BER_BVISNULL( &op->o_csn ) ) {
-		struct berval csn;
-		char csnbuf[LDAP_PVT_CSNSTR_BUFSIZE];
-
-		csn.bv_val = csnbuf;
-		csn.bv_len = sizeof(csnbuf);
-		slap_get_csn( op, &csn, 1 );
-	}
-
 	/* begin transaction */
 	rs->sr_err = mdb_opinfo_get( op, mdb, 0, &moi );
 	rs->sr_text = NULL;
@@ -111,9 +101,18 @@ txnReturn:
 		rs->sr_text = "internal error";
 		goto return_results;
 	}
-
 	txn = moi->moi_txn;
 
+	/* allocate CSN */
+	if ( BER_BVISNULL( &op->o_csn ) ) {
+		struct berval csn;
+		char csnbuf[LDAP_PVT_CSNSTR_BUFSIZE];
+
+		csn.bv_val = csnbuf;
+		csn.bv_len = sizeof(csnbuf);
+		slap_get_csn( op, &csn, 1 );
+	}
+
 	if ( !be_issuffix( op->o_bd, &op->o_req_ndn ) ) {
 		dnParent( &op->o_req_ndn, &pdn );
 	}
diff --git a/servers/slapd/back-mdb/modify.c b/servers/slapd/back-mdb/modify.c
index 5c1dfda0ab..46a8c1449a 100644
--- a/servers/slapd/back-mdb/modify.c
+++ b/servers/slapd/back-mdb/modify.c
@@ -457,14 +457,6 @@ txnReturn:
 
 	ctrls[num_ctrls] = NULL;
 
-	/* Don't touch the opattrs, if this is a contextCSN update
-	 * initiated from updatedn */
-	if ( !be_isupdate(op) || !op->orm_modlist || op->orm_modlist->sml_next ||
-		 op->orm_modlist->sml_desc != slap_schema.si_ad_contextCSN ) {
-
-		slap_mods_opattrs( op, &op->orm_modlist, 1 );
-	}
-
 	/* begin transaction */
 	rs->sr_err = mdb_opinfo_get( op, mdb, 0, &moi );
 	rs->sr_text = NULL;
@@ -476,9 +468,16 @@ txnReturn:
 		rs->sr_text = "internal error";
 		goto return_results;
 	}
-
 	txn = moi->moi_txn;
 
+	/* Don't touch the opattrs, if this is a contextCSN update
+	 * initiated from updatedn */
+	if ( !be_isupdate(op) || !op->orm_modlist || op->orm_modlist->sml_next ||
+		 op->orm_modlist->sml_desc != slap_schema.si_ad_contextCSN ) {
+
+		slap_mods_opattrs( op, &op->orm_modlist, 1 );
+	}
+
 	/* get entry or ancestor */
 	rs->sr_err = mdb_dn2entry( op, txn, NULL, &op->o_req_ndn, &e, 1 );
 
diff --git a/servers/slapd/back-mdb/modrdn.c b/servers/slapd/back-mdb/modrdn.c
index a222554f5b..ec5b82b524 100644
--- a/servers/slapd/back-mdb/modrdn.c
+++ b/servers/slapd/back-mdb/modrdn.c
@@ -103,8 +103,6 @@ txnReturn:
 
 	ctrls[num_ctrls] = NULL;
 
-	slap_mods_opattrs( op, &op->orr_modlist, 1 );
-
 	/* begin transaction */
 	rs->sr_err = mdb_opinfo_get( op, mdb, 0, &moi );
 	rs->sr_text = NULL;
@@ -116,9 +114,10 @@ txnReturn:
 		rs->sr_text = "internal error";
 		goto return_results;
 	}
-
 	txn = moi->moi_txn;
 
+	slap_mods_opattrs( op, &op->orr_modlist, 1 );
+
 	if ( be_issuffix( op->o_bd, &op->o_req_ndn ) ) {
 #ifdef MDB_MULTIPLE_SUFFIXES
 		/* Allow renaming one suffix entry to another */