New tool for killing btree nodes on a filesystem

To be used by error injection tests.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

bcachefs.c

@@ -235,6 +235,8 @@ int main(int argc, char *argv[])
 		return cmd_list(argc, argv);
 	if (!strcmp(cmd, "list_journal"))
 		return cmd_list_journal(argc, argv);
+	if (!strcmp(cmd, "kill_btree_node"))
+		return cmd_kill_btree_node(argc, argv);
 
 	if (!strcmp(cmd, "setattr"))
 		return cmd_setattr(argc, argv);

cmd_debug.c

@@ -677,3 +677,109 @@ int cmd_list_journal(int argc, char *argv[])
 	bch2_fs_stop(c);
 	return 0;
 }
+
+static void kill_btree_node_usage(void)
+{
+	puts("bcachefs kill_btree_node - make btree nodes unreadable\n"
+	     "Usage: bcachefs kill_btree_node [OPTION]... <devices>\n"
+	     "\n"
+	     "Options:\n"
+	     "  -b (extents|inodes|dirents|xattrs)    Btree to delete from\n"
+	     "  -l level                              Levle to delete from (0 == leaves)\n"
+	     "  -i index                              Index of btree node to kill\n"
+	     "  -h                                    Display this help and exit\n"
+	     "Report bugs to <linux-bcache@vger.kernel.org>");
+}
+
+int cmd_kill_btree_node(int argc, char *argv[])
+{
+	struct bch_opts opts = bch2_opts_empty();
+	enum btree_id btree_id = 0;
+	unsigned level = 0;
+	u64 node_index = 0;
+	int opt;
+
+	opt_set(opts, read_only,	true);
+
+	while ((opt = getopt(argc, argv, "b:l:i:h")) != -1)
+		switch (opt) {
+		case 'b':
+			btree_id = read_string_list_or_die(optarg,
+						bch2_btree_ids, "btree id");
+			break;
+		case 'l':
+			if (kstrtouint(optarg, 10, &level) || level >= BTREE_MAX_DEPTH)
+				die("invalid level");
+			break;
+		case 'i':
+			if (kstrtoull(optarg, 10, &node_index))
+				die("invalid index %s", optarg);
+			break;
+		case 'h':
+			kill_btree_node_usage();
+			exit(EXIT_SUCCESS);
+		}
+	args_shift(optind);
+
+	if (!argc)
+		die("Please supply device(s)");
+
+	struct bch_fs *c = bch2_fs_open(argv, argc, opts);
+	if (IS_ERR(c))
+		die("error opening %s: %s", argv[0], strerror(-PTR_ERR(c)));
+
+	struct btree_trans trans;
+	struct btree_iter iter;
+	struct btree *b;
+	int ret;
+	void *zeroes;
+
+	ret = posix_memalign(&zeroes, c->opts.block_size, c->opts.block_size);
+	if (ret)
+		die("error %s from posix_memalign", strerror(ret));
+
+	bch2_trans_init(&trans, c, 0, 0);
+
+	__for_each_btree_node(&trans, iter, btree_id, POS_MIN, 0, level, 0, b, ret) {
+		if (b->c.level != level)
+			continue;
+
+		if (!node_index) {
+			struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(bkey_i_to_s_c(&b->key));
+			const struct bch_extent_ptr *ptr;
+
+			struct printbuf buf = PRINTBUF;
+
+			bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(&b->key));
+			bch_info(c, "killing btree node %s", buf.buf);
+			printbuf_exit(&buf);
+
+			bkey_for_each_ptr(ptrs, ptr) {
+				struct bch_dev *ca = bch_dev_bkey_exists(c, ptr->dev);
+
+				ret = pwrite(ca->disk_sb.bdev->bd_fd, zeroes,
+					     c->opts.block_size, ptr->offset << 9);
+				if (ret != c->opts.block_size) {
+					bch_err(c, "pwrite error: expected %u got %i %s",
+						c->opts.block_size, ret, strerror(errno));
+					ret = EXIT_FAILURE;
+					goto done;
+				}
+			}
+			goto done;
+		}
+
+		node_index--;
+	}
+	if (ret)
+		bch_err(c, "error %i walking btree nodes", ret);
+	else
+		bch_err(c, "node at specified index not found");
+	ret = EXIT_FAILURE;
+done:
+	bch2_trans_iter_exit(&trans, &iter);
+	bch2_trans_exit(&trans);
+
+	bch2_fs_stop(c);
+	return ret;
+}

cmds.h

@@ -45,6 +45,7 @@ int cmd_fsck(int argc, char *argv[]);
 int cmd_dump(int argc, char *argv[]);
 int cmd_list(int argc, char *argv[]);
 int cmd_list_journal(int argc, char *argv[]);
+int cmd_kill_btree_node(int argc, char *argv[]);
 
 int cmd_migrate(int argc, char *argv[]);
 int cmd_migrate_superblock(int argc, char *argv[]);