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Date:   Mon,  4 Dec 2017 22:35:28 +0300
From:   Artem Blagodarenko <artem.blagodarenko@...il.com>
To:     linux-ext4@...r.kernel.org
Cc:     adilger.kernel@...ger.ca,
        Artem Blagodarenko <artem.blagodarenko@...gate.com>
Subject: [PATCH v3 2/4] e2image: add -b option to use supperblock backup

From: Artem Blagodarenko <artem.blagodarenko@...gate.com>

e2image has no ability to use superblock backup to copy metadata.
This feature can be useful if someone wants to make partition
image and fix it using e2fsck utility.

New -b option allows to pass superblock number, like e2fsck utility do.
e2image doesn't change primary superblock and store is as is, so
it can be fixed using e2fsck latter.

Signed-off-by: Artem Blagodarenko <artem.blagodarenko@...il.com>
---
 misc/e2image.8.in | 32 ++++++++++++++++++++++++++++++++
 misc/e2image.c    | 44 ++++++++++++++++++++++++++++++++++++++------
 2 files changed, 70 insertions(+), 6 deletions(-)

diff --git a/misc/e2image.8.in b/misc/e2image.8.in
index f28a76ea..d6125bb4 100644
--- a/misc/e2image.8.in
+++ b/misc/e2image.8.in
@@ -11,6 +11,14 @@ e2image \- Save critical ext2/ext3/ext4 filesystem metadata to a file
 .B \-r|Q
 ]
 [
+.B \-b
+.I superblock
+]
+[
+.B \-B
+.I blocksize
+]
+[
 .B \-fr
 ]
 .I device
@@ -167,6 +175,22 @@ the
 option will prevent analysis of problems related to hash-tree indexed
 directories.
 .PP
+Option
+.B \-b
+.I superblock
+can be used to get image from partition with broken primary superblock.
+The partition is copied as is including broken primary superblock.
+.PP
+Option
+.B \-B
+.I blocksize
+can be used to set superblock block size. Normally,  e2fsck  will  search
+for  the superblock at various different block sizes in an attempt to find
+the appropriate blocksize. This search can be fooled in some cases.  This
+option forces e2fsck to only try locating the superblock at a particular
+blocksize. If the superblock is not found, e2fsck will terminate with a
+fatal error.
+.PP
 Note that this will work even if you substitute "/dev/hda1" for another raw
 disk image, or QCOW2 image previously created by
 .BR e2image .
@@ -217,6 +241,14 @@ This can be useful to write a qcow2 image containing all data to a
 sparse image file where it can be loop mounted, or to a disk partition.
 Note that this may not work with qcow2 images not generated by e2image.
 .PP
+Options
+.B \-b
+.I superblock
+and
+.B \-B
+.I blocksize
+can be used same way as for raw images.
+.PP
 .SH INCLUDING DATA
 Normally
 .B e2image
diff --git a/misc/e2image.c b/misc/e2image.c
index be001f0f..b1b7a17d 100644
--- a/misc/e2image.c
+++ b/misc/e2image.c
@@ -104,7 +104,8 @@ static int get_bits_from_size(size_t size)
 
 static void usage(void)
 {
-	fprintf(stderr, _("Usage: %s [ -r|Q ] [ -fr ] device image-file\n"),
+	fprintf(stderr, _("Usage: %s [ -r|Q ] [ -b superblock ] [ -B blocksize]"
+			  "[ -fr ] device image-file\n"),
 		program_name);
 	fprintf(stderr, _("       %s -I device image-file\n"), program_name);
 	fprintf(stderr, _("       %s -ra  [  -cfnp  ] [ -o src_offset ] "
@@ -1256,7 +1257,8 @@ static void output_qcow2_meta_data_blocks(ext2_filsys fs, int fd)
 	free_qcow2_image(img);
 }
 
-static void write_raw_image_file(ext2_filsys fs, int fd, int type, int flags)
+static void write_raw_image_file(ext2_filsys fs, int fd, int type, int flags,
+				 blk64_t superblock)
 {
 	struct process_block_struct	pb;
 	struct ext2_inode		inode;
@@ -1284,6 +1286,22 @@ static void write_raw_image_file(ext2_filsys fs, int fd, int type, int flags)
 		}
 	}
 
+	if (superblock) {
+		int j;
+
+		ext2fs_mark_block_bitmap2(meta_block_map, superblock);
+		meta_blocks_count++;
+
+		/*
+		 * Mark the backup superblock descriptors
+		 */
+		for (j = 0; j < fs->desc_blocks; j++) {
+			ext2fs_mark_block_bitmap2(meta_block_map,
+			ext2fs_descriptor_block_loc2(fs, superblock, j));
+		}
+		meta_blocks_count += fs->desc_blocks;
+	}
+
 	mark_table_blocks(fs);
 	if (show_progress)
 		fprintf(stderr, "%s", _("Scanning inodes...\n"));
@@ -1463,6 +1481,8 @@ int main (int argc, char ** argv)
 	int ignore_rw_mount = 0;
 	int check = 0;
 	struct stat st;
+	blk64_t superblock = 0;
+	int blocksize = 0;
 
 #ifdef ENABLE_NLS
 	setlocale(LC_MESSAGES, "");
@@ -1476,8 +1496,14 @@ int main (int argc, char ** argv)
 	if (argc && *argv)
 		program_name = *argv;
 	add_error_table(&et_ext2_error_table);
-	while ((c = getopt(argc, argv, "nrsIQafo:O:pc")) != EOF)
+	while ((c = getopt(argc, argv, "b:B:nrsIQafo:O:pc")) != EOF)
 		switch (c) {
+		case 'b':
+			superblock = strtoull(optarg, NULL, 0);
+			break;
+		case 'B':
+			blocksize = strtoul(optarg, NULL, 0);
+			break;
 		case 'I':
 			flags |= E2IMAGE_INSTALL_FLAG;
 			break;
@@ -1529,6 +1555,11 @@ int main (int argc, char ** argv)
 						 "with raw or QCOW2 images."));
 		exit(1);
 	}
+	if (superblock && !img_type) {
+		com_err(program_name, 0, "%s", _("-b option can only be used "
+						 "with raw or QCOW2 images."));
+		exit(1);
+	}
 	if ((source_offset || dest_offset) && img_type != E2IMAGE_RAW) {
 		com_err(program_name, 0, "%s",
 			_("Offsets are only allowed with raw images."));
@@ -1579,8 +1610,9 @@ int main (int argc, char ** argv)
 		}
 	}
 	sprintf(offset_opt, "offset=%llu", source_offset);
-	retval = ext2fs_open2(device_name, offset_opt, open_flag, 0, 0,
-			      unix_io_manager, &fs);
+	retval = ext2fs_open2(device_name, offset_opt, open_flag,
+				    superblock, blocksize, unix_io_manager,
+				    &fs);
         if (retval) {
 		com_err (program_name, retval, _("while trying to open %s"),
 			 device_name);
@@ -1665,7 +1697,7 @@ skip_device:
 		exit(1);
 	}
 	if (img_type)
-		write_raw_image_file(fs, fd, img_type, flags);
+		write_raw_image_file(fs, fd, img_type, flags, superblock);
 	else
 		write_image_file(fs, fd);
 
-- 
2.13.6 (Apple Git-96)

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