On Mon, Dec 19, 2011 at 03:12:03PM +0100, Andreas Dilger wrote:
> On 2011-12-13, at 7:13 PM, Darrick J. Wong wrote:
> > diff --git a/lib/ext2fs/csum.c b/lib/ext2fs/csum.c
> > index 596923e..1f7c641 100644
> > --- a/lib/ext2fs/csum.c
> > +++ b/lib/ext2fs/csum.c
> > @@ -30,6 +30,89 @@
> > #define STATIC static
> > #endif
> >
> > +static errcode_t ext2fs_inode_csum(ext2_filsys fs, ext2_ino_t inum,
> > + struct ext2_inode_large *inode,
> > + __u32 *crc, int has_hi)
> > +{
> > + __u32 ncrc;
>
> Why use "ncrc" in this function instead of just using "*crc" directly?
>
> > + struct ext2_inode_large *desc = inode;
> > + size_t size = fs->super->s_inode_size;
> > + __u16 old_lo;
> > + __u16 old_hi = 0;
> > + errcode_t retval = 0;
>
> Also, it seems "retval" isn't useful, since it is always 0, which can
> be returned directly at the end.
In the old days it wasn't automatic that retval is always 0, therefore I
allocated a temporary ncrc in case the function failed. Since that no longer
happens and ext2fs_inode_csum is a static function now, I will undo all
that.
> > +
> > + old_lo = inode->i_checksum_lo;
> > + inode->i_checksum_lo = 0;
> > + if (has_hi) {
> > + old_hi = inode->i_checksum_hi;
> > + inode->i_checksum_hi = 0;
> > + }
> > +
> > + inum = ext2fs_cpu_to_le32(inum);
> > + ncrc = ext2fs_crc32c_le(~0, fs->super->s_uuid,
> > + sizeof(fs->super->s_uuid));
> > + ncrc = ext2fs_crc32c_le(ncrc, (unsigned char *)&inum, sizeof(inum));
> > + ncrc = ext2fs_crc32c_le(ncrc, (unsigned char *)desc, size);
> > + *crc = ncrc;
> > +
> > + inode->i_checksum_lo = old_lo;
> > + if (has_hi)
> > + inode->i_checksum_hi = old_hi;
> > + return retval;
> > +}
> > +
> > +int ext2fs_inode_csum_verify(ext2_filsys fs, ext2_ino_t inum,
> > + struct ext2_inode_large *inode)
> > +{
> > + errcode_t retval;
> > + __u32 provided, calculated;
> > + int has_hi;
> > +
> > + if (fs->super->s_creator_os != EXT2_OS_LINUX ||
> > + !EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
> > + EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
> > + return 1;
> > +
> > + has_hi = (EXT2_INODE_SIZE(fs->super) > EXT2_GOOD_OLD_INODE_SIZE &&
> > + inode->i_extra_isize >= EXT4_INODE_CSUM_HI_EXTRA_LOCATION);
> > +
> > + provided = ext2fs_le16_to_cpu(inode->i_checksum_lo);
> > + retval = ext2fs_inode_csum(fs, inum, inode, &calculated, has_hi);
> > + if (retval)
> > + return 0;
> > + if (has_hi) {
> > + __u32 hi = ext2fs_le16_to_cpu(inode->i_checksum_hi);
> > + provided |= hi << 16;
>
> It seems a bit odd to get the low bytes of "provided" before calculating
> the checksum, but the high bytes of after calculating the checksum. It
> isn't incorrect since the checksum is preserved over the call to
> ext2fs_inode_csum(), but seems a bit strange.
I think this is a merge error.
> > diff --git a/lib/ext2fs/ext2_fs.h b/lib/ext2fs/ext2_fs.h
> > index ce2fd66..4bcf1de 100644
> > --- a/lib/ext2fs/ext2_fs.h
> > +++ b/lib/ext2fs/ext2_fs.h
> > @@ -459,6 +459,10 @@ struct ext2_inode_large {
> > __u32 i_version_hi; /* high 32 bits for 64-bit version */
> > };
> >
> > +#define EXT4_INODE_CSUM_HI_EXTRA_LOCATION \
> > + (offsetof(struct ext2_inode_large, i_checksum_hi) + sizeof(__u16) - \
> > + EXT2_GOOD_OLD_INODE_SIZE)
>
> It also makes sense to call this EXT4_INODE_CSUM_HI_END or similar, since
> _LOCATION incorrectly implies (to me at least) that this is the offset of
> the i_checksum_hi field, when it is actually the byte beyond the end.
_END it is.
--D
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