It looks like the subject line for this commit was truncated --- I
could try to make something up, but could you suggest something?
Thanks!!
- Ted
On Tue, Dec 10, 2013 at 05:22:20PM -0800, Darrick J. Wong wrote:
> If ext2fs_descriptor_block_loc2() is called with a meta_bg filesystem
> and group_block is not the normal value, the function will return the
> location of the backup group descriptor block in the next block group.
> Unfortunately, it fails to account for the possibility that the backup
> group contains a backup superblock but the regular superblock does
> not. This is the case with block groups 48-49 on a meta_bg fs with 1k
> blocks; in this case, libext2fs will fail to open the filesystem.
>
> Therefore, teach the function to adjust for superblocks in the backup
> group, if necessary.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> lib/ext2fs/openfs.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
>
> diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
> index b2a8abb..92d9e40 100644
> --- a/lib/ext2fs/openfs.c
> +++ b/lib/ext2fs/openfs.c
> @@ -47,7 +47,7 @@ blk64_t ext2fs_descriptor_block_loc2(ext2_filsys fs, blk64_t group_block,
> bg = EXT2_DESC_PER_BLOCK(fs->super) * i;
> if (ext2fs_bg_has_super(fs, bg))
> has_super = 1;
> - ret_blk = ext2fs_group_first_block2(fs, bg) + has_super;
> + ret_blk = ext2fs_group_first_block2(fs, bg);
> /*
> * If group_block is not the normal value, we're trying to use
> * the backup group descriptors and superblock --- so use the
> @@ -57,10 +57,21 @@ blk64_t ext2fs_descriptor_block_loc2(ext2_filsys fs, blk64_t group_block,
> * have the infrastructure in place to do that.
> */
> if (group_block != fs->super->s_first_data_block &&
> - ((ret_blk + fs->super->s_blocks_per_group) <
> - ext2fs_blocks_count(fs->super)))
> + ((ret_blk + has_super + fs->super->s_blocks_per_group) <
> + ext2fs_blocks_count(fs->super))) {
> ret_blk += fs->super->s_blocks_per_group;
> - return ret_blk;
> +
> + /*
> + * If we're going to jump forward a block group, make sure
> + * that we adjust has_super to account for the next group's
> + * backup superblock (or lack thereof).
> + */
> + if (ext2fs_bg_has_super(fs, bg + 1))
> + has_super = 1;
> + else
> + has_super = 0;
> + }
> + return ret_blk + has_super;
> }
>
> blk_t ext2fs_descriptor_block_loc(ext2_filsys fs, blk_t group_block, dgrp_t i)
>
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