From ab0b0ec7ce94b1e6421b520611229ffc456704dc Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@openldap.org>
Date: Mon, 9 Nov 2015 20:09:10 +0000
Subject: [PATCH] mdbx: backport - ITS#8304 fix page_merge (mdb_del cursor
 tracking).

Was using the pre-touch dst page pointer instead of the touched page

Change-Id: Ib41af356dcf883b923dbfbbc7591a02483ee54dd
---
 CHANGES | 1 +
 mdb.c   | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/CHANGES b/CHANGES
index 0b63a13d..3880ee12 100644
--- a/CHANGES
+++ b/CHANGES
@@ -10,6 +10,7 @@ LMDB 0.9.17 Release Engineering
 	Fix ITS#8264 cursor_del cursor tracking
 	Fix ITS#8299 mdb_del cursor tracking
 	Fix ITS#8300 mdb_del cursor tracking
+	Fix ITS#8304 mdb_del cursor tracking
 	Fix ITS#7771 fakepage cursor tracking
 	Fix ITS#7789 ensure mapsize >= pages in use
 	Fix ITS#7971 mdb_txn_renew0() new reader slots
diff --git a/mdb.c b/mdb.c
index 7840d16e..064d3d0e 100644
--- a/mdb.c
+++ b/mdb.c
@@ -7875,6 +7875,9 @@ mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst)
 	if (unlikely(rc = mdb_page_touch(cdst)))
 		return rc;
 
+	/* get dst page again now that we've touched it. */
+	pdst = cdst->mc_pg[cdst->mc_top];
+
 	/* Move all nodes from src to dst.
 	 */
 	j = nkeys = NUMKEYS(pdst);