From: Howard Chu <hyc@symas.com>
Date: Wed, 21 Sep 2011 21:14:11 +0000 (-0700)
Subject: Track changes to all cursors.
X-Git-Tag: OPENLDAP_REL_ENG_2_4_27~148^2~18
X-Git-Url: https://git.sur5r.net/?a=commitdiff_plain;h=b9d13a29e6c4c2742277c82bdc646c32d364a619;p=openldap

Track changes to all cursors.

For any change to a page or node, update all other cursors pointing
at the same page (or node). Cursors are now stored in a linked list
off their owning transaction. Cursors are all closed when the transaction
ends. Cursors in parent transactions are updated when their child
transaction commits.
---

diff --git a/libraries/libmdb/mdb.c b/libraries/libmdb/mdb.c
index 143b5a1636..28d5001c48 100644
--- a/libraries/libmdb/mdb.c
+++ b/libraries/libmdb/mdb.c
@@ -731,6 +731,8 @@ struct MDB_txn {
 #define DB_DIRTY	0x01		/**< DB was written in this txn */
 #define DB_STALE	0x02		/**< DB record is older than txnID */
 /** @} */
+	/** Array of cursors for each DB */
+	MDB_cursor	**mt_cursors;
 	/** Array of flags for each DB */
 	unsigned char	*mt_dbflags;
 	/**	Number of DB records in use. This number only ever increments;
@@ -762,6 +764,10 @@ struct MDB_xcursor;
 
 	/** Cursors are used for all DB operations */
 struct MDB_cursor {
+	/** Next cursor on this DB in this txn */
+	MDB_cursor	*mc_next;
+	/** Original cursor if this is a shadow */
+	MDB_cursor	*mc_orig;
 	/** Context used for databases with #MDB_DUPSORT, otherwise NULL */
 	struct MDB_xcursor	*mc_xcursor;
 	/** The transaction that owns this cursor */
@@ -783,6 +789,8 @@ struct MDB_cursor {
  */
 #define C_INITIALIZED	0x01	/**< cursor has been initialized and is valid */
 #define C_EOF	0x02			/**< No more data */
+#define C_SUB	0x04			/**< Cursor is a sub-cursor */
+#define C_SHADOW	0x08			/**< Cursor is a dup from a parent txn */
 /** @} */
 	unsigned int	mc_flags;	/**< @ref mdb_cursor */
 	MDB_page	*mc_pg[CURSOR_STACK];	/**< stack of pushed pages */
@@ -1160,6 +1168,26 @@ mdb_page_touch(MDB_cursor *mc)
 		mp->mp_flags |= P_DIRTY;
 
 finish:
+		/* Adjust other cursors pointing to mp */
+		if (mc->mc_flags & C_SUB) {
+			MDB_cursor *m2, *m3;
+			MDB_dbi dbi = mc->mc_dbi-1;
+
+			for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+				m3 = &m2->mc_xcursor->mx_cursor;
+				if (m3->mc_pg[mc->mc_top] == mc->mc_pg[mc->mc_top]) {
+					m3->mc_pg[mc->mc_top] = mp;
+				}
+			}
+		} else {
+			MDB_cursor *m2;
+
+			for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
+				if (m2->mc_pg[mc->mc_top] == mc->mc_pg[mc->mc_top]) {
+					m2->mc_pg[mc->mc_top] = mp;
+				}
+			}
+		}
 		mc->mc_pg[mc->mc_top] = mp;
 		/** If this page has a parent, update the parent to point to
 		 * this new page.
@@ -1208,6 +1236,92 @@ mdb_env_sync(MDB_env *env, int force)
 	return rc;
 }
 
+/** Make shadow copies of all of parent txn's cursors */
+static int
+mdb_cursor_shadow(MDB_txn *src, MDB_txn *dst)
+{
+	MDB_cursor *mc, *m2;
+	unsigned int i, j, size;
+
+	for (i=0;i<src->mt_numdbs; i++) {
+		if (src->mt_cursors[i]) {
+			size = sizeof(MDB_cursor);
+			if (src->mt_cursors[i]->mc_xcursor)
+				size += sizeof(MDB_xcursor);
+			for (m2 = src->mt_cursors[i]; m2; m2=m2->mc_next) {
+				mc = malloc(size);
+				if (!mc)
+					return ENOMEM;
+				mc->mc_orig = m2;
+				mc->mc_txn = dst;
+				mc->mc_dbi = i;
+				mc->mc_db = &dst->mt_dbs[i];
+				mc->mc_dbx = m2->mc_dbx;
+				mc->mc_dbflag = &dst->mt_dbflags[i];
+				mc->mc_snum = m2->mc_snum;
+				mc->mc_top = m2->mc_top;
+				mc->mc_flags = m2->mc_flags | C_SHADOW;
+				for (j=0; j<mc->mc_snum; j++) {
+					mc->mc_pg[j] = m2->mc_pg[j];
+					mc->mc_ki[j] = m2->mc_ki[j];
+				}
+				if (m2->mc_xcursor) {
+					MDB_xcursor *mx, *mx2;
+					mx = (MDB_xcursor *)(mc+1);
+					mc->mc_xcursor = mx;
+					mx2 = m2->mc_xcursor;
+					mx->mx_db = mx2->mx_db;
+					mx->mx_dbx = mx2->mx_dbx;
+					mx->mx_dbflag = mx2->mx_dbflag;
+					mx->mx_cursor.mc_txn = dst;
+					mx->mx_cursor.mc_dbi = mx2->mx_cursor.mc_dbi;
+					mx->mx_cursor.mc_db = &mx->mx_db;
+					mx->mx_cursor.mc_dbx = &mx->mx_dbx;
+					mx->mx_cursor.mc_dbflag = &mx->mx_dbflag;
+					mx->mx_cursor.mc_snum = mx2->mx_cursor.mc_snum;
+					mx->mx_cursor.mc_top = mx2->mx_cursor.mc_top;
+					mx->mx_cursor.mc_flags = mx2->mx_cursor.mc_flags | C_SHADOW;
+					for (j=0; j<mx2->mx_cursor.mc_snum; j++) {
+						mx->mx_cursor.mc_pg[j] = mx2->mx_cursor.mc_pg[j];
+						mx->mx_cursor.mc_ki[j] = mx2->mx_cursor.mc_ki[j];
+					}
+				} else {
+					mc->mc_xcursor = NULL;
+				}
+				mc->mc_next = dst->mt_cursors[i];
+				dst->mt_cursors[i] = mc;
+			}
+		}
+	}
+	return MDB_SUCCESS;
+}
+
+/** Merge shadow cursors back into parent's */
+static void
+mdb_cursor_merge(MDB_txn *txn)
+{
+	MDB_dbi i;
+	for (i=0; i<txn->mt_numdbs; i++) {
+		if (txn->mt_cursors[i]) {
+			MDB_cursor *mc;
+			while ((mc = txn->mt_cursors[i])) {
+				txn->mt_cursors[i] = mc->mc_next;
+				if (mc->mc_flags & C_SHADOW) {
+					MDB_cursor *m2 = mc->mc_orig;
+					unsigned int j;
+					m2->mc_snum = mc->mc_snum;
+					m2->mc_top = mc->mc_top;
+					for (j=0; j<mc->mc_snum; j++) {
+						m2->mc_pg[j] = mc->mc_pg[j];
+						m2->mc_ki[j] = mc->mc_ki[j];
+					}
+				}
+				free(mc);
+			}
+		}
+	}
+}
+
 static void
 mdb_txn_reset0(MDB_txn *txn);
 
@@ -1312,7 +1426,7 @@ int
 mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 {
 	MDB_txn *txn;
-	int rc;
+	int rc, size;
 
 	if (env->me_flags & MDB_FATAL_ERROR) {
 		DPUTS("environment had fatal error, must shutdown!");
@@ -1324,16 +1438,22 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 			return EINVAL;
 		}
 	}
-	if ((txn = calloc(1, sizeof(MDB_txn) +
-		env->me_maxdbs * (sizeof(MDB_db)+1))) == NULL) {
+	size = sizeof(MDB_txn) + env->me_maxdbs * (sizeof(MDB_db)+1);
+	if (!(flags & MDB_RDONLY))
+		size += env->me_maxdbs * sizeof(MDB_cursor *);
+
+	if ((txn = calloc(1, size)) == NULL) {
 		DPRINTF("calloc: %s", strerror(ErrCode()));
 		return ENOMEM;
 	}
 	txn->mt_dbs = (MDB_db *)(txn+1);
 	if (flags & MDB_RDONLY) {
 		txn->mt_flags |= MDB_TXN_RDONLY;
+		txn->mt_dbflags = (unsigned char *)(txn->mt_dbs + env->me_maxdbs);
+	} else {
+		txn->mt_cursors = (MDB_cursor **)(txn->mt_dbs + env->me_maxdbs);
+		txn->mt_dbflags = (unsigned char *)(txn->mt_cursors + env->me_maxdbs);
 	}
-	txn->mt_dbflags = (unsigned char *)(txn->mt_dbs + env->me_maxdbs);
 	txn->mt_env = env;
 
 	if (parent) {
@@ -1359,6 +1479,7 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 		txn->mt_dbxs = parent->mt_dbxs;
 		memcpy(txn->mt_dbs, parent->mt_dbs, txn->mt_numdbs * sizeof(MDB_db));
 		memcpy(txn->mt_dbflags, parent->mt_dbflags, txn->mt_numdbs);
+		mdb_cursor_shadow(parent, txn);
 		rc = 0;
 	} else {
 		rc = mdb_txn_renew0(txn);
@@ -1390,6 +1511,17 @@ mdb_txn_reset0(MDB_txn *txn)
 		MDB_page *dp;
 		unsigned int i;
 
+		/* close(free) all cursors */
+		for (i=0; i<txn->mt_numdbs; i++) {
+			if (txn->mt_cursors[i]) {
+				MDB_cursor *mc;
+				while ((mc = txn->mt_cursors[i])) {
+					txn->mt_cursors[i] = mc->mc_next;
+					free(mc);
+				}
+			}
+		}
+
 		/* return all dirty pages to dpage list */
 		for (i=1; i<=txn->mt_u.dirty_list[0].mid; i++) {
 			dp = txn->mt_u.dirty_list[i].mptr;
@@ -1497,7 +1629,6 @@ mdb_txn_commit(MDB_txn *txn)
 		return MDB_SUCCESS;
 	}
 
-
 	if (F_ISSET(txn->mt_flags, MDB_TXN_ERROR)) {
 		DPUTS("error flag is set, can't commit");
 		if (txn->mt_parent)
@@ -1506,6 +1637,9 @@ mdb_txn_commit(MDB_txn *txn)
 		return EINVAL;
 	}
 
+	/* Merge (and close) our cursors with parent's */
+	mdb_cursor_merge(txn);
+
 	if (txn->mt_parent) {
 		MDB_db *ip, *jp;
 		MDB_dbi i;
@@ -1532,21 +1666,11 @@ mdb_txn_commit(MDB_txn *txn)
 		src = txn->mt_u.dirty_list;
 		x = mdb_mid2l_search(dst, src[1].mid);
 		for (y=1; y<=src[0].mid; y++) {
-			MDB_page *mp;
 			while (x <= dst[0].mid && dst[x].mid != src[y].mid) x++;
 			if (x > dst[0].mid)
 				break;
-			mp = dst[x].mptr;
-			dp = src[y].mptr;
-			mp->mp_lower = dp->mp_lower;
-			mp->mp_upper = dp->mp_upper;
-			if (IS_LEAF2(mp)) {
-				memcpy(METADATA(mp), METADATA(dp), NUMKEYS(mp) * mp->mp_pad);
-			} else {
-				memcpy((char *)mp+mp->mp_upper, (char *)dp+dp->mp_upper,
-					txn->mt_env->me_psize - mp->mp_upper);
-			}
-			free(src[y].mptr);
+			free(dst[x].mptr);
+			dst[x].mptr = src[y].mptr;
 		}
 		x = dst[0].mid;
 		for (; y<=src[0].mid; y++) {
@@ -2838,6 +2962,20 @@ mdb_node_search(MDB_cursor *mc, MDB_val *key, int *exactp)
 	return node;
 }
 
+#if 0
+static void
+mdb_cursor_adjust(MDB_cursor *mc, func)
+{
+	MDB_cursor *m2;
+
+	for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
+		if (m2->mc_pg[m2->mc_top] == mc->mc_pg[mc->mc_top]) {
+			func(mc, m2);
+		}
+	}
+}
+#endif
+
 /** Pop a page off the top of the cursor's stack. */
 static void
 mdb_cursor_pop(MDB_cursor *mc)
@@ -3790,12 +3928,13 @@ top:
 				if (flags == MDB_CURRENT)
 					goto current;
 
-				/* create a fake page for the dup items */
 				dkey.mv_size = NODEDSZ(leaf);
 				dkey.mv_data = NODEDATA(leaf);
 				/* data matches, ignore it */
 				if (!mc->mc_dbx->md_dcmp(data, &dkey))
 					return (flags == MDB_NODUPDATA) ? MDB_KEYEXIST : MDB_SUCCESS;
+
+				/* create a fake page for the dup items */
 				memcpy(dbuf, dkey.mv_data, dkey.mv_size);
 				dkey.mv_data = dbuf;
 				fp = (MDB_page *)pbuf;
@@ -3913,6 +4052,26 @@ new_sub:
 	} else {
 		/* There is room already in this leaf page. */
 		rc = mdb_node_add(mc, mc->mc_ki[mc->mc_top], key, rdata, 0, 0);
+		if (rc == 0 && !do_sub) {
+			/* Adjust other cursors pointing to mp */
+			MDB_cursor *m2, *m3;
+			MDB_dbi dbi = mc->mc_dbi;
+			unsigned i = mc->mc_top;
+			MDB_page *mp = mc->mc_pg[i];
+
+			if (mc->mc_flags & C_SUB)
+				dbi--;
+
+			for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+				if (mc->mc_flags & C_SUB)
+					m3 = &m2->mc_xcursor->mx_cursor;
+				else
+					m3 = m2;
+				if (m3->mc_pg[i] == mp && m3->mc_ki[i] >= mc->mc_ki[i]) {
+					m3->mc_ki[i]++;
+				}
+			}
+		}
 	}
 
 	if (rc != MDB_SUCCESS)
@@ -3946,6 +4105,18 @@ put_sub:
 				rc = mdb_cursor_put(&mc->mc_xcursor->mx_cursor, &dkey, &xdata, xflags);
 				if (rc)
 					return rc;
+				{
+					/* Adjust other cursors pointing to mp */
+					MDB_cursor *m2;
+					unsigned i = mc->mc_top;
+					MDB_page *mp = mc->mc_pg[i];
+
+					for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
+						if (m2->mc_pg[i] == mp && m2->mc_ki[i] == mc->mc_ki[i]) {
+							mdb_xcursor_init1(m2, leaf);
+						}
+					}
+				}
 			}
 			rc = mdb_cursor_put(&mc->mc_xcursor->mx_cursor, data, &xdata, xflags);
 			if (flags & F_SUBDATA) {
@@ -4373,7 +4544,7 @@ mdb_xcursor_init1(MDB_cursor *mc, MDB_node *node)
 		MDB_db *db = NODEDATA(node);
 		mx->mx_db = *db;
 		mx->mx_cursor.mc_snum = 0;
-		mx->mx_cursor.mc_flags = 0;
+		mx->mx_cursor.mc_flags = C_SUB;
 	} else {
 		MDB_page *fp = NODEDATA(node);
 		mx->mx_db.md_pad = mc->mc_pg[mc->mc_top]->mp_pad;
@@ -4385,7 +4556,7 @@ mdb_xcursor_init1(MDB_cursor *mc, MDB_node *node)
 		mx->mx_db.md_entries = NUMKEYS(fp);
 		mx->mx_db.md_root = fp->mp_pgno;
 		mx->mx_cursor.mc_snum = 1;
-		mx->mx_cursor.mc_flags = C_INITIALIZED;
+		mx->mx_cursor.mc_flags = C_INITIALIZED|C_SUB;
 		mx->mx_cursor.mc_top = 0;
 		mx->mx_cursor.mc_pg[0] = fp;
 		mx->mx_cursor.mc_ki[0] = 0;
@@ -4410,6 +4581,7 @@ mdb_xcursor_init1(MDB_cursor *mc, MDB_node *node)
 static void
 mdb_cursor_init(MDB_cursor *mc, MDB_txn *txn, MDB_dbi dbi, MDB_xcursor *mx)
 {
+	mc->mc_orig = NULL;
 	mc->mc_dbi = dbi;
 	mc->mc_txn = txn;
 	mc->mc_db = &txn->mt_dbs[dbi];
@@ -4444,6 +4616,10 @@ mdb_cursor_open(MDB_txn *txn, MDB_dbi dbi, MDB_cursor **ret)
 			mx = (MDB_xcursor *)(mc + 1);
 		}
 		mdb_cursor_init(mc, txn, dbi, mx);
+		if (txn->mt_cursors) {
+			mc->mc_next = txn->mt_cursors[dbi];
+			txn->mt_cursors[dbi] = mc;
+		}
 	} else {
 		return ENOMEM;
 	}
@@ -4481,6 +4657,13 @@ void
 mdb_cursor_close(MDB_cursor *mc)
 {
 	if (mc != NULL) {
+		/* remove from txn, if tracked */
+		if (mc->mc_txn->mt_cursors) {
+			MDB_cursor **prev = &mc->mc_txn->mt_cursors[mc->mc_dbi];
+			while (*prev && *prev != mc) prev = &(*prev)->mc_next;
+			if (*prev == mc)
+				*prev = mc->mc_next;
+		}
 		free(mc);
 	}
 }
@@ -4594,6 +4777,28 @@ mdb_node_move(MDB_cursor *csrc, MDB_cursor *cdst)
 	 */
 	mdb_node_del(csrc->mc_pg[csrc->mc_top], csrc->mc_ki[csrc->mc_top], key.mv_size);
 
+	{
+		/* Adjust other cursors pointing to mp */
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = csrc->mc_dbi;
+		MDB_page *mp = csrc->mc_pg[csrc->mc_top];
+
+		if (csrc->mc_flags & C_SUB)
+			dbi--;
+
+		for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			if (csrc->mc_flags & C_SUB)
+				m3 = &m2->mc_xcursor->mx_cursor;
+			else
+				m3 = m2;
+			if (m3->mc_pg[csrc->mc_top] == mp && m3->mc_ki[csrc->mc_top] ==
+				csrc->mc_ki[csrc->mc_top]) {
+				m3->mc_pg[csrc->mc_top] = cdst->mc_pg[cdst->mc_top];
+				m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
+			}
+		}
+	}
+
 	/* Update the parent separators.
 	 */
 	if (csrc->mc_ki[csrc->mc_top] == 0) {
@@ -4657,6 +4862,7 @@ mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst)
 	indx_t			 i, j;
 	MDB_node		*srcnode;
 	MDB_val		 key, data;
+	unsigned	nkeys;
 
 	DPRINTF("merging page %zu into %zu", csrc->mc_pg[csrc->mc_top]->mp_pgno,
 		cdst->mc_pg[cdst->mc_top]->mp_pgno);
@@ -4670,7 +4876,7 @@ mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst)
 
 	/* Move all nodes from src to dst.
 	 */
-	j = NUMKEYS(cdst->mc_pg[cdst->mc_top]);
+	j = nkeys = NUMKEYS(cdst->mc_pg[cdst->mc_top]);
 	if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
 		key.mv_size = csrc->mc_db->md_pad;
 		key.mv_data = METADATA(csrc->mc_pg[csrc->mc_top]);
@@ -4711,6 +4917,26 @@ mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst)
 		csrc->mc_db->md_leaf_pages--;
 	else
 		csrc->mc_db->md_branch_pages--;
+	{
+		/* Adjust other cursors pointing to mp */
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = csrc->mc_dbi;
+		MDB_page *mp = cdst->mc_pg[cdst->mc_top];
+
+		if (csrc->mc_flags & C_SUB)
+			dbi--;
+
+		for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			if (csrc->mc_flags & C_SUB)
+				m3 = &m2->mc_xcursor->mx_cursor;
+			else
+				m3 = m2;
+			if (m3->mc_pg[csrc->mc_top] == csrc->mc_pg[csrc->mc_top]) {
+				m3->mc_pg[csrc->mc_top] = mp;
+				m3->mc_ki[csrc->mc_top] += nkeys;
+			}
+		}
+	}
 	mdb_cursor_pop(csrc);
 
 	return mdb_rebalance(csrc);
@@ -4763,22 +4989,61 @@ mdb_rebalance(MDB_cursor *mc)
 	}
 
 	if (mc->mc_snum < 2) {
-		if (NUMKEYS(mc->mc_pg[mc->mc_top]) == 0) {
+		MDB_page *mp = mc->mc_pg[0];
+		if (NUMKEYS(mp) == 0) {
 			DPUTS("tree is completely empty");
 			mc->mc_db->md_root = P_INVALID;
 			mc->mc_db->md_depth = 0;
 			mc->mc_db->md_leaf_pages = 0;
-			mdb_midl_append(&mc->mc_txn->mt_free_pgs, mc->mc_pg[mc->mc_top]->mp_pgno);
+			mdb_midl_append(&mc->mc_txn->mt_free_pgs, mp->mp_pgno);
 			mc->mc_snum = 0;
-		} else if (IS_BRANCH(mc->mc_pg[mc->mc_top]) && NUMKEYS(mc->mc_pg[mc->mc_top]) == 1) {
+			mc->mc_top = 0;
+			{
+				/* Adjust other cursors pointing to mp */
+				MDB_cursor *m2, *m3;
+				MDB_dbi dbi = mc->mc_dbi;
+
+				if (mc->mc_flags & C_SUB)
+					dbi--;
+
+				for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+					if (mc->mc_flags & C_SUB)
+						m3 = &m2->mc_xcursor->mx_cursor;
+					else
+						m3 = m2;
+					if (m3->mc_pg[0] == mp) {
+						m3->mc_snum = 0;
+						m3->mc_top = 0;
+					}
+				}
+			}
+		} else if (IS_BRANCH(mp) && NUMKEYS(mp) == 1) {
 			DPUTS("collapsing root page!");
-			mdb_midl_append(&mc->mc_txn->mt_free_pgs, mc->mc_pg[mc->mc_top]->mp_pgno);
-			mc->mc_db->md_root = NODEPGNO(NODEPTR(mc->mc_pg[mc->mc_top], 0));
+			mdb_midl_append(&mc->mc_txn->mt_free_pgs, mp->mp_pgno);
+			mc->mc_db->md_root = NODEPGNO(NODEPTR(mp, 0));
 			if ((rc = mdb_page_get(mc->mc_txn, mc->mc_db->md_root,
-				&mc->mc_pg[mc->mc_top])))
+				&mc->mc_pg[0])))
 				return rc;
 			mc->mc_db->md_depth--;
 			mc->mc_db->md_branch_pages--;
+			{
+				/* Adjust other cursors pointing to mp */
+				MDB_cursor *m2, *m3;
+				MDB_dbi dbi = mc->mc_dbi;
+
+				if (mc->mc_flags & C_SUB)
+					dbi--;
+
+				for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+					if (mc->mc_flags & C_SUB)
+						m3 = &m2->mc_xcursor->mx_cursor;
+					else
+						m3 = m2;
+					if (m3->mc_pg[0] == mp) {
+						m3->mc_pg[0] = mc->mc_pg[0];
+					}
+				}
+			}
 		} else
 			DPUTS("root page doesn't need rebalancing");
 		return MDB_SUCCESS;
@@ -4925,7 +5190,7 @@ static int
 mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno)
 {
 	uint8_t		 flags;
-	int		 rc = MDB_SUCCESS, ins_new = 0;
+	int		 rc = MDB_SUCCESS, ins_new = 0, new_root = 0;
 	indx_t		 newindx;
 	pgno_t		 pgno = 0;
 	unsigned int	 i, j, split_indx, nkeys, pmax;
@@ -4955,6 +5220,7 @@ mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno
 		mc->mc_db->md_root = pp->mp_pgno;
 		DPRINTF("root split! new root = %zu", pp->mp_pgno);
 		mc->mc_db->md_depth++;
+		new_root = 1;
 
 		/* Add left (implicit) pointer. */
 		if ((rc = mdb_node_add(mc, 0, NULL, NULL, mp->mp_pgno, 0)) != MDB_SUCCESS) {
@@ -5102,12 +5368,12 @@ newsep:
 		rc = mdb_node_add(&mn, mn.mc_ki[ptop], &sepkey, NULL, rp->mp_pgno, 0);
 		mn.mc_top++;
 	}
-	if (IS_LEAF2(rp)) {
-		return rc;
-	}
 	if (rc != MDB_SUCCESS) {
 		return rc;
 	}
+	if (IS_LEAF2(rp)) {
+		goto done;
+	}
 
 	/* Move half of the keys to the right sibling. */
 
@@ -5183,6 +5449,39 @@ newsep:
 	/* return tmp page to freelist */
 	copy->mp_next = mc->mc_txn->mt_env->me_dpages;
 	mc->mc_txn->mt_env->me_dpages = copy;
+done:
+	{
+		/* Adjust other cursors pointing to mp */
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = mc->mc_dbi;
+
+		if (mc->mc_flags & C_SUB)
+			dbi--;
+
+		for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			if (mc->mc_flags & C_SUB)
+				m3 = &m2->mc_xcursor->mx_cursor;
+			else
+				m3 = m2;
+			if (new_root) {
+				/* root split */
+				for (i=m3->mc_top; i>0; i--) {
+					m3->mc_ki[i+1] = m3->mc_ki[i];
+					m3->mc_pg[i+1] = m3->mc_pg[i];
+				}
+				m3->mc_ki[0] = mc->mc_ki[0];
+				m3->mc_pg[0] = mc->mc_pg[0];
+				m3->mc_snum++;
+				m3->mc_top++;
+			}
+			if (m3->mc_pg[mc->mc_top] == mp) {
+				if (m3->mc_ki[m3->mc_top] >= split_indx) {
+					m3->mc_pg[m3->mc_top] = rp;
+					m3->mc_ki[m3->mc_top] -= split_indx;
+				}
+			}
+		}
+	}
 	return rc;
 }
 
diff --git a/libraries/libmdb/mdb.h b/libraries/libmdb/mdb.h
index 1672d81c16..14105b26e4 100644
--- a/libraries/libmdb/mdb.h
+++ b/libraries/libmdb/mdb.h
@@ -843,9 +843,6 @@ void mdb_cursor_close(MDB_cursor *cursor);
 	 * case of the #MDB_SET option, in which the \b key object is unchanged), and
 	 * the address and length of the data are returned in the object to which \b data
 	 * refers.
-	 * @bug Cursors are not coordinated with write operations. If a cursor in a
-	 * write transaction is performing a sequential scan while records are being
-	 * inserted or deleted in the same transaction, the cursor will be corrupted.
 	 * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
 	 * @param[in,out] key The key for a retrieved item
 	 * @param[in,out] data The data of a retrieved item