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Date: Wed, 5 Jul 2017 11:01:02 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Artem Blagodarenko <artem.blagodarenko@...il.com>,
Theodore Ts'o <tytso@....edu>
Cc: linux-ext4@...r.kernel.org, alexey.lyashkov@...il.com
Subject: Re: [PATCH 1/4] ext2fs: opening filesystem code refactoring
On Jun 26, 2017, at 10:58 AM, Artem Blagodarenko <artem.blagodarenko@...il.com> wrote:
>
> From: Artem Blagodarenko <artem.blagodarenko@...gate.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@...gate.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
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