Add bttest unlink page command

To enable testing of recursive btree traversal, add an unlink page
command to the bttest program (used for debugging the libdb2 btree
back end).  This new bttest command can unlink a specified page
number, or it can search for and unlink a page that has both a left
and a right sibling.  (The user can specify whether to find an
internal page or a leaf page.)

This unlinking makes the page inaccessible to conventional sequential
traversal, simulating some btree corruption that has been seen in the
field.

ticket: 8476

src/plugins/kdb/db2/libdb2/btree/bt_delete.c

@@ -50,7 +50,6 @@ static char sccsid[] = "@(#)bt_delete.c	8.13 (Berkeley) 7/28/94";
 static int __bt_bdelete __P((BTREE *, const DBT *));
 static int __bt_curdel __P((BTREE *, const DBT *, PAGE *, u_int));
 static int __bt_pdelete __P((BTREE *, PAGE *));
-static int __bt_relink __P((BTREE *, PAGE *));
 static int __bt_stkacq __P((BTREE *, PAGE **, CURSOR *));
 
 /*
@@ -634,7 +633,7 @@ dup2:				c->pg.pgno = e.page->pgno;
  *	t:	tree
  *	h:	page to be deleted
  */
-static int
+int
 __bt_relink(t, h)
 	BTREE *t;
 	PAGE *h;

src/plugins/kdb/db2/libdb2/btree/extern.h

@@ -62,6 +62,7 @@
 #define __bt_dpage	__kdb2_bt_dpage
 #define __bt_dump	__kdb2_bt_dump
 #define __bt_stat	__kdb2_bt_stat
+#define __bt_relink	__kdb2_bt_relink
 
 int	 __bt_close __P((DB *));
 int	 __bt_cmp __P((BTREE *, const DBT *, EPG *));
@@ -90,12 +91,11 @@ int	 __ovfl_delete __P((BTREE *, void *));
 int	 __ovfl_get __P((BTREE *, void *, size_t *, void **, size_t *));
 int	 __ovfl_put __P((BTREE *, const DBT *, db_pgno_t *));
 
-#ifdef DEBUG
 int	 __bt_dnpage __P((DB *, db_pgno_t));
 int	 __bt_dpage __P((DB *, PAGE *));
 int	 __bt_dmpage __P((PAGE *));
 int	 __bt_dump __P((DB *));
-#endif
-#ifdef STATISTICS
+
 int	 __bt_stat __P((DB *));
-#endif
+
+int	 __bt_relink __P((BTREE *, PAGE *));

src/plugins/kdb/db2/libdb2/libdb.exports

@@ -24,6 +24,7 @@ __kdb2_bt_open
 __kdb2_bt_pgin
 __kdb2_bt_pgout
 __kdb2_bt_put
+__kdb2_bt_relink
 __kdb2_bt_ret
 __kdb2_bt_search
 __kdb2_bt_seq

src/plugins/kdb/db2/libdb2/test/btree.tests/main.c

@@ -33,6 +33,35 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
+/*
+ * Copyright (C) 2016 by the Massachusetts Institute of Technology.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in
+ *   the documentation and/or other materials provided with the
+ *   distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
 
 #if defined(LIBC_SCCS) && !defined(lint)
 static char sccsid[] = "@(#)main.c	8.1 (Berkeley) 6/4/93";
@@ -98,6 +127,7 @@ void rnext	__P((DB *, char **));
 void rprev	__P((DB *, char **));
 void usage	__P((void));
 void user	__P((DB *));
+void unlinkpg	__P((DB *, char **));
 
 cmd_table commands[] = {
 	"?",	0, 0, help, "help", NULL,
@@ -138,6 +168,8 @@ cmd_table commands[] = {
 #ifdef DEBUG
 	"sh",	1, 0, show, "show page", "dump a page",
 #endif
+	"u",	1, 0, unlinkpg, "unlink pgno|internal|leaf", "unlink a page",
+
 	{ NULL },
 };
 
@@ -883,3 +915,59 @@ usage()
 	    progname);
 	exit (1);
 }
+
+/* Find a candidate page to unlink. */
+static PAGE *
+candidatepg(BTREE *t, char *arg)
+{
+	PAGE *h = NULL;
+	db_pgno_t pg;
+	u_int32_t sflags;
+
+	if (arg[0] == 'i')
+		sflags = P_BINTERNAL | P_RINTERNAL;
+	if (arg[0] == 'l')
+		sflags = P_BLEAF | P_RLEAF;
+	for (pg = P_ROOT; pg < t->bt_mp->npages;
+	     mpool_put(t->bt_mp, h, 0), pg++) {
+		if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
+			return h;
+		/* Look for a nonempty page of the correct
+		 * type that has both left and right siblings. */
+		if (h->prevpg == P_INVALID || h->nextpg == P_INVALID)
+			continue;
+		if ((h->flags & sflags) && NEXTINDEX(h) != 0)
+			break;
+	}
+	if (pg == t->bt_mp->npages)
+		h = NULL;
+	return h;
+}
+
+void
+unlinkpg(DB *db, char **argv)
+{
+	BTREE *t = db->internal;
+	PAGE *h = NULL;
+	db_pgno_t pg;
+
+	pg = atoi(argv[1]);
+	if (pg == 0)
+		h = candidatepg(t, argv[1]);
+	else
+		h = mpool_get(t->bt_mp, pg, 0);
+
+	if (h == NULL) {
+		fprintf(stderr, "unable to find appropriate page to unlink\n");
+		return;
+	}
+	printf("chain %d <- %d -> %d\n", h->prevpg, h->pgno, h->nextpg);
+	if (__bt_relink(t, h) != 0) {
+		perror("unlinkpg");
+		goto cleanup;
+	}
+	h->prevpg = P_INVALID;
+	h->nextpg = P_INVALID;
+cleanup:
+	mpool_put(t->bt_mp, h, MPOOL_DIRTY);
+}