[1/4] ext2fs: opening filesystem code refactoring

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

There are similar opening filesystem code in different utilities.

The patch moves this code to ext2fs_try_open_fs().
This function make one of the action based on parameters:
1) open filesystem with given superblock, superblock size
2) open filesystem with given superblock, but try to
find right block size
3) open filesystem with default superblock and block size

Signed-off-by: Artem Blagodarenko <artem.blagodarenko@seagate.com>
---
 e2fsck/unix.c       |   28 +++-------------------------
 lib/ext2fs/ext2fs.h |    4 ++++
 lib/ext2fs/openfs.c |   32 ++++++++++++++++++++++++++++++++
 misc/dumpe2fs.c     |   17 +++--------------
 4 files changed, 42 insertions(+), 39 deletions(-)

On Jun 26, 2017, at 10:58 AM, Artem Blagodarenko <artem.blagodarenko@gmail.com> wrote:
> 
> From: Artem Blagodarenko <artem.blagodarenko@seagate.com>
> 
> There are similar opening filesystem code in different utilities.
> 
> The patch moves this code to ext2fs_try_open_fs().
> This function make one of the action based on parameters:
> 1) open filesystem with given superblock, superblock size
> 2) open filesystem with given superblock, but try to
> find right block size
> 3) open filesystem with default superblock and block size

I'm definitely in favour of this, but wonder if this should just become part
of ext2fs_open2(), so that other tools also get the benefit of this change?
That could be done only if the superblock number and blocksize are zero.

Should this also try at least a few backup superblocks (e.g. {1, 3, 5, 7, 9} *
blocksize * 8)?

Also, e2fsck/util.c::get_backup_sb() does something very similar.  In "main()"
this is called just before calling try_open_fs(), which you've updated below.
If ext2fs_try_open() also tried backup superblocks then get_backup_sb() wouldn't
be needed at all.

> Signed-off-by: Artem Blagodarenko <artem.blagodarenko@seagate.com>
> ---
> e2fsck/unix.c       |   28 +++-------------------------
> lib/ext2fs/ext2fs.h |    4 ++++
> lib/ext2fs/openfs.c |   32 ++++++++++++++++++++++++++++++++
> misc/dumpe2fs.c     |   17 +++--------------
> 4 files changed, 42 insertions(+), 39 deletions(-)
> 
> diff --git a/e2fsck/unix.c b/e2fsck/unix.c
> index ff96148..76f984b 100644
> --- a/e2fsck/unix.c
> +++ b/e2fsck/unix.c
> @@ -1116,31 +1116,9 @@ static errcode_t try_open_fs(e2fsck_t ctx, int flags, io_manager io_ptr,
> 			     ext2_filsys *ret_fs)
> {
> 	errcode_t retval;
> -
> -	*ret_fs = NULL;
> -	if (ctx->superblock && ctx->blocksize) {
> -		retval = ext2fs_open2(ctx->filesystem_name, ctx->io_options,
> -				      flags, ctx->superblock, ctx->blocksize,
> -				      io_ptr, ret_fs);
> -	} else if (ctx->superblock) {
> -		int blocksize;
> -		for (blocksize = EXT2_MIN_BLOCK_SIZE;
> -		     blocksize <= EXT2_MAX_BLOCK_SIZE; blocksize *= 2) {
> -			if (*ret_fs) {
> -				ext2fs_free(*ret_fs);
> -				*ret_fs = NULL;
> -			}
> -			retval = ext2fs_open2(ctx->filesystem_name,
> -					      ctx->io_options, flags,
> -					      ctx->superblock, blocksize,
> -					      io_ptr, ret_fs);
> -			if (!retval)
> -				break;
> -		}
> -	} else
> -		retval = ext2fs_open2(ctx->filesystem_name, ctx->io_options,
> -				      flags, 0, 0, io_ptr, ret_fs);
> -
> +	retval = ext2fs_try_open_fs(ctx->filesystem_name, ctx->io_options,
> +			   ctx->superblock, ctx->blocksize, flags,
> +			   io_ptr, ret_fs);
> 	if (retval == 0) {
> 		(*ret_fs)->priv_data = ctx;
> 		e2fsck_set_bitmap_type(*ret_fs, EXT2FS_BMAP64_RBTREE,
> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> index c18ea5f..1163ab6 100644
> --- a/lib/ext2fs/ext2fs.h
> +++ b/lib/ext2fs/ext2fs.h
> @@ -1577,6 +1577,10 @@ extern errcode_t ext2fs_open2(const char *name, const char *io_options,
> 			      int flags, int superblock,
> 			      unsigned int block_size, io_manager manager,
> 			      ext2_filsys *ret_fs);
> +extern errcode_t ext2fs_try_open_fs(char *filesystem_name, char *io_options,
> +			     blk64_t superblock, int blocksize, int flags,
> +			     io_manager io_ptr, ext2_filsys *ret_fs);
> +
> /*
>  * The dgrp_t argument to these two functions is not actually a group number
>  * but a block number offset within a group table!  Convert with the formula
> diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
> index 93b02ed..a236b40 100644
> --- a/lib/ext2fs/openfs.c
> +++ b/lib/ext2fs/openfs.c
> @@ -487,6 +487,38 @@ cleanup:
> 	return retval;
> }
> 
> +errcode_t ext2fs_try_open_fs(char *filesystem_name, char *io_options,
> +			     blk64_t superblock, int blocksize, int flags,
> +			     io_manager io_ptr, ext2_filsys *ret_fs)
> +{
> +	errcode_t retval;
> +
> +	*ret_fs = NULL;
> +	if (superblock && blocksize) {
> +		retval = ext2fs_open2(filesystem_name, io_options,
> +				      flags, superblock, blocksize,
> +				      io_ptr, ret_fs);
> +	} else if (superblock) {
> +		int blocksize;
> +		for (blocksize = EXT2_MIN_BLOCK_SIZE;
> +		     blocksize <= EXT2_MAX_BLOCK_SIZE; blocksize *= 2) {
> +			if (*ret_fs) {
> +				ext2fs_free(*ret_fs);
> +				*ret_fs = NULL;
> +			}
> +			retval = ext2fs_open2(filesystem_name,
> +					      io_options, flags,
> +					      superblock, blocksize,
> +					      io_ptr, ret_fs);
> +			if (!retval)
> +				break;
> +		}
> +	} else
> +		retval = ext2fs_open2(filesystem_name, io_options,
> +				      flags, 0, 0, io_ptr, ret_fs);
> +	return retval;
> +}
> +
> /*
>  * Set/get the filesystem data I/O channel.
>  *
> diff --git a/misc/dumpe2fs.c b/misc/dumpe2fs.c
> index 395ea9e..0f55cfb 100644
> --- a/misc/dumpe2fs.c
> +++ b/misc/dumpe2fs.c
> @@ -568,20 +568,9 @@ int main (int argc, char ** argv)
> 	if (image_dump)
> 		flags |= EXT2_FLAG_IMAGE_FILE;
> try_open_again:
> -	if (use_superblock && !use_blocksize) {
> -		for (use_blocksize = EXT2_MIN_BLOCK_SIZE;
> -		     use_blocksize <= EXT2_MAX_BLOCK_SIZE;
> -		     use_blocksize *= 2) {
> -			retval = ext2fs_open (device_name, flags,
> -					      use_superblock,
> -					      use_blocksize, unix_io_manager,
> -					      &fs);
> -			if (!retval)
> -				break;
> -		}
> -	} else
> -		retval = ext2fs_open (device_name, flags, use_superblock,
> -				      use_blocksize, unix_io_manager, &fs);
> +	retval = ext2fs_try_open_fs(device_name, 0,
> +				    use_superblock, use_blocksize, flags,
> +				    unix_io_manager, &fs);
> 	if (retval && !(flags & EXT2_FLAG_IGNORE_CSUM_ERRORS)) {
> 		flags |= EXT2_FLAG_IGNORE_CSUM_ERRORS;
> 		goto try_open_again;
> --
> 1.7.1
> 


Cheers, Andreas