[2/4] e2image: add -b option to use supperblock backup

From: Artem Blagodarenko <artem.blagodarenko@seagate.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@seagate.com>
---
 misc/e2image.c |   38 ++++++++++++++++++++++++++++++++------
 1 files changed, 32 insertions(+), 6 deletions(-)

> On Jun 26, 2017, at 10:58 AM, Artem Blagodarenko <artem.blagodarenko@gmail.com> wrote:
> 
> From: Artem Blagodarenko <artem.blagodarenko@seagate.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@seagate.com>

One comment/question below.

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

> ---
> misc/e2image.c |   38 ++++++++++++++++++++++++++++++++------
> 1 files changed, 32 insertions(+), 6 deletions(-)
> 
> diff --git a/misc/e2image.c b/misc/e2image.c
> index e0c3188..acc27d1 100644
> --- a/misc/e2image.c
> +++ b/misc/e2image.c
> @@ -103,7 +103,8 @@ 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 ] "
> +			  "[ -fr ] device image-file\n"),

Does this also need to accept the "-B blocksize" option?  That said, this is
definitely an improvement.

> 		program_name);
> 	fprintf(stderr, _("       %s -I device image-file\n"), program_name);
> 	fprintf(stderr, _("       %s -ra  [  -cfnp  ] [ -o src_offset ] "
> @@ -1255,7 +1256,7 @@ 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;
> @@ -1283,6 +1284,22 @@ 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"));
> @@ -1462,6 +1479,7 @@ int main (int argc, char ** argv)
> 	int ignore_rw_mount = 0;
> 	int check = 0;
> 	struct stat st;
> +	blk64_t superblock = 0;
> 
> #ifdef ENABLE_NLS
> 	setlocale(LC_MESSAGES, "");
> @@ -1475,7 +1493,7 @@ 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, "nrsIQafo:O:pcb:")) != EOF)
> 		switch (c) {
> 		case 'I':
> 			flags |= E2IMAGE_INSTALL_FLAG;
> @@ -1514,6 +1532,9 @@ int main (int argc, char ** argv)
> 		case 'c':
> 			check = 1;
> 			break;
> +		case 'b':
> +			superblock = strtoull(optarg, NULL, 0);
> +			break;
> 		default:
> 			usage();
> 		}
> @@ -1528,6 +1549,11 @@ 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."));
> @@ -1578,8 +1604,8 @@ 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_try_open_fs(device_name, offset_opt, superblock, 0,
> +				    open_flag, unix_io_manager, &fs);
>         if (retval) {
> 		com_err (program_name, retval, _("while trying to open %s"),
> 			 device_name);
> @@ -1664,7 +1690,7 @@ 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);
> 
> --
> 1.7.1
> 


Cheers, Andreas