Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1656190 > unrolled thread

Re: [PATCH v2 27/28] ext4: xattr inode deduplication

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: [PATCH v2 27/28] ext4: xattr inode deduplication Tahsin Erdogan <tahsin@google.com> - 2017-06-02 14:50 +0200
    Re: [PATCH v2 27/28] ext4: xattr inode deduplication "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-06-02 20:10 +0200

#1656190 — Re: [PATCH v2 27/28] ext4: xattr inode deduplication

> Hmm... normally we'd supply sbi->s_csum_seed as the second argument so
> that the metadata checksum value also has the fs uuid stamped into it.

I have thought about using sbi->s_csum_seed and was a little hesitant
because it involves adding more complexity to e2fsprogs to handle
cases like changing uuid or turning off metadata_csum. After thinking
more about this, I think it is doable.

> Even if you dismiss that, we usually follow the convention of
> initializing the crc32c calculation with (~0U), not (0U), to strengthen
> crc32c's ability to detect zeroes being injected at the start of the
> stream.

Agreed, using ~0 is definitely better than 0.

[toc] | [next] | [standalone]

#1656439

On Fri, Jun 02, 2017 at 05:46:22AM -0700, Tahsin Erdogan wrote:
> > Hmm... normally we'd supply sbi->s_csum_seed as the second argument so
> > that the metadata checksum value also has the fs uuid stamped into it.
> 
> I have thought about using sbi->s_csum_seed and was a little hesitant
> because it involves adding more complexity to e2fsprogs to handle
> cases like changing uuid or turning off metadata_csum. After thinking
> more about this, I think it is doable.

e2fsprogs already has code to walk the fs to rewrite/remove checksums,
so it shouldn't be too much effort to tap into that to rewrite the
ea_info hash.

> > Even if you dismiss that, we usually follow the convention of
> > initializing the crc32c calculation with (~0U), not (0U), to strengthen
> > crc32c's ability to detect zeroes being injected at the start of the
> > stream.
> 
> Agreed, using ~0 is definitely better than 0.

--D

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web