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Message-Id: <24632860-8D87-466A-A816-19B8C5CDA52F@dilger.ca>
Date: Mon, 4 Jun 2018 11:44:35 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Artem Blagodarenko <artem.blagodarenko@...il.com>
Cc: linux-ext4@...r.kernel.org
Subject: Re: [PATCH v5 2/4] e2image: add -b and -B options to use supperblock
backup
> On May 26, 2018, at 4:45 PM, Artem Blagodarenko <artem.blagodarenko@...il.com> wrote:
>
> 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. Option -B allows to set
> superblock size.
>
> Signed-off-by: Artem Blagodarenko <artem.blagodarenko@...il.com>
Reviewed-by: Andreas Dilger <adilger@...ger.ca>
> ---
> misc/e2image.8.in | 33 +++++++++++++++++++++++++++++++++
> misc/e2image.c | 43 +++++++++++++++++++++++++++++++++++++------
> 2 files changed, 70 insertions(+), 6 deletions(-)
>
> diff --git a/misc/e2image.8.in b/misc/e2image.8.in
> index a7bfdf24..bbbb57ae 100644
> --- a/misc/e2image.8.in
> +++ b/misc/e2image.8.in
> @@ -12,6 +12,15 @@ e2image \- Save critical ext2/ext3/ext4 filesystem metadata to a file
> ]
> [
> .B \-f
> +.B \-b
> +.I superblock
> +]
> +[
> +.B \-B
> +.I blocksize
> +]
> +[
> +.B \-fr
> ]
> .I device
> .I image-file
> @@ -167,6 +176,22 @@ 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 +242,14 @@ 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 83ae6335..727e3876 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 ] [ -f ] device image-file\n"),
> + fprintf(stderr, _("Usage: %s [ -r|Q ] [ -f ] [ -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 +1610,8 @@ 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 +1696,7 @@ 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);
>
> --
> 2.14.3
>
Cheers, Andreas
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