btrfsprogs/0004-Add-btrfs-map-logical-program-to-map-and-read-logica.patch

From ab8fb4c99516c186641bda1dbc0e788f68b4dc77 Mon Sep 17 00:00:00 2001
From: Chris Mason <chris.mason@oracle.com>
Date: Thu, 12 Nov 2009 14:34:09 -0500
Subject: [PATCH 4/4] Add btrfs-map-logical program to map and read logical block numbers

This allows us to figure out which physical byte offset on which device
is the real location for a given logical block number.  It can
optionally read the block in and save it to a file for debugging
analysis.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
---
 Makefile            |    6 +-
 btrfs-map-logical.c |  221 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 226 insertions(+), 1 deletions(-)
 create mode 100644 btrfs-map-logical.c

diff --git a/Makefile b/Makefile
index 8097b5a..02f881e 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,8 @@ prefix ?= /usr/local
 bindir = $(prefix)/bin
 LIBS=-luuid
 
-progs = btrfsctl mkfs.btrfs btrfs-debug-tree btrfs-show btrfs-vol btrfsck
+progs = btrfsctl mkfs.btrfs btrfs-debug-tree btrfs-show btrfs-vol btrfsck \
+	btrfs-map-logical
 
 # make C=1 to enable sparse
 ifdef C
@@ -56,6 +57,9 @@ btrfs-debug-tree: $(objects) debug-tree.o
 btrfstune: $(objects) btrfstune.o
 	gcc $(CFLAGS) -o btrfstune $(objects) btrfstune.o $(LDFLAGS) $(LIBS)
 
+btrfs-map-logical: $(objects) btrfs-map-logical.o
+	gcc $(CFLAGS) -o btrfs-map-logical $(objects) btrfs-map-logical.o $(LDFLAGS) $(LIBS)
+
 btrfs-image: $(objects) btrfs-image.o
 	gcc $(CFLAGS) -o btrfs-image $(objects) btrfs-image.o -lpthread -lz $(LDFLAGS) $(LIBS)
 
diff --git a/btrfs-map-logical.c b/btrfs-map-logical.c
new file mode 100644
index 0000000..a109c6a
--- /dev/null
+++ b/btrfs-map-logical.c
@@ -0,0 +1,221 @@
+/*
+ * Copyright (C) 2009 Oracle.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#define _XOPEN_SOURCE 500
+#define _GNU_SOURCE 1
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <getopt.h>
+#include "kerncompat.h"
+#include "ctree.h"
+#include "volumes.h"
+#include "disk-io.h"
+#include "print-tree.h"
+#include "transaction.h"
+#include "list.h"
+#include "version.h"
+
+/* we write the mirror info to stdout unless they are dumping the data
+ * to stdout
+ * */
+static FILE *info_file;
+
+struct extent_buffer *debug_read_block(struct btrfs_root *root, u64 bytenr,
+				     u32 blocksize, int copy)
+{
+	int ret;
+	int dev_nr;
+	struct extent_buffer *eb;
+	u64 length;
+	struct btrfs_multi_bio *multi = NULL;
+	struct btrfs_device *device;
+	int num_copies;
+	int mirror_num = 1;
+
+	eb = btrfs_find_create_tree_block(root, bytenr, blocksize);
+	if (!eb)
+		return NULL;
+
+	dev_nr = 0;
+	length = blocksize;
+	while (1) {
+		ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,
+				      eb->start, &length, &multi, mirror_num);
+		BUG_ON(ret);
+		device = multi->stripes[0].dev;
+		eb->fd = device->fd;
+		device->total_ios++;
+		eb->dev_bytenr = multi->stripes[0].physical;
+
+		fprintf(info_file, "mirror %d logical %Lu physical %Lu "
+			"device %s\n", mirror_num, bytenr, eb->dev_bytenr,
+			device->name);
+		kfree(multi);
+
+		if (!copy || mirror_num == copy)
+			ret = read_extent_from_disk(eb);
+
+		num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
+					      eb->start, eb->len);
+		if (num_copies == 1)
+			break;
+
+		mirror_num++;
+		if (mirror_num > num_copies)
+			break;
+	}
+	return eb;
+}
+
+static void print_usage(void)
+{
+	fprintf(stderr, "usage: btrfs-map-logical [options] mount_point\n");
+	fprintf(stderr, "\t-l Logical extent to map\n");
+	fprintf(stderr, "\t-c Copy of the extent to read (usually 1 or 2)\n");
+	fprintf(stderr, "\t-o Output file to hold the extent\n");
+	fprintf(stderr, "\t-s Number of bytes to read\n");
+	exit(1);
+}
+
+static struct option long_options[] = {
+	/* { "byte-count", 1, NULL, 'b' }, */
+	{ "logical", 1, NULL, 'l' },
+	{ "copy", 1, NULL, 'c' },
+	{ "output", 1, NULL, 'c' },
+	{ "bytes", 1, NULL, 'b' },
+	{ 0, 0, 0, 0}
+};
+
+int main(int ac, char **av)
+{
+	struct cache_tree root_cache;
+	struct btrfs_root *root;
+	struct extent_buffer *eb;
+	char *dev;
+	char *output_file = NULL;
+	u64 logical = 0;
+	int ret = 0;
+	int option_index = 0;
+	int copy = 0;
+	u64 bytes = 0;
+	int out_fd = 0;
+	int err;
+
+	while(1) {
+		int c;
+		c = getopt_long(ac, av, "l:c:o:b:", long_options,
+				&option_index);
+		if (c < 0)
+			break;
+		switch(c) {
+			case 'l':
+				logical = atoll(optarg);
+				if (logical == 0) {
+					fprintf(stderr,
+						"invalid extent number\n");
+					print_usage();
+				}
+				break;
+			case 'c':
+				copy = atoi(optarg);
+				if (copy == 0) {
+					fprintf(stderr,
+						"invalid copy number\n");
+					print_usage();
+				}
+				break;
+			case 'b':
+				bytes = atoll(optarg);
+				if (bytes == 0) {
+					fprintf(stderr,
+						"invalid byte count\n");
+					print_usage();
+				}
+				break;
+			case 'o':
+				output_file = strdup(optarg);
+				break;
+			default:
+				print_usage();
+		}
+	}
+	ac = ac - optind;
+	if (ac == 0)
+		print_usage();
+	if (logical == 0)
+		print_usage();
+	if (copy < 0)
+		print_usage();
+
+	dev = av[optind];
+
+	radix_tree_init();
+	cache_tree_init(&root_cache);
+
+	root = open_ctree(dev, 0, 0);
+	if (!root) {
+		fprintf(stderr, "Open ctree failed\n");
+		exit(1);
+	}
+
+	if (output_file) {
+		if (strcmp(output_file, "-") == 0) {
+			out_fd = 1;
+			info_file = stderr;
+		} else {
+			out_fd = open(output_file, O_RDWR | O_CREAT, 0600);
+			if (out_fd < 0)
+				goto close;
+			err = ftruncate(out_fd, 0);
+			if (err) {
+				close(out_fd);
+				goto close;
+			}
+			info_file = stdout;
+		}
+	}
+
+	if (bytes == 0)
+		bytes = root->sectorsize;
+
+	bytes = (bytes + root->sectorsize - 1) / root->sectorsize;
+	bytes *= root->sectorsize;
+
+	while (bytes > 0) {
+		eb = debug_read_block(root, logical, root->sectorsize, copy);
+		if (eb && output_file) {
+			err = write(out_fd, eb->data, eb->len);
+			if (err < 0 || err != eb->len) {
+				fprintf(stderr, "output file write failed\n");
+				goto out_close_fd;
+			}
+		}
+		free_extent_buffer(eb);
+		logical += root->sectorsize;
+		bytes -= root->sectorsize;
+	}
+
+out_close_fd:
+	if (output_file && out_fd != 1)
+		close(out_fd);
+close:
+	close_ctree(root);
+	return ret;
+}
-- 
1.6.6.1