From: Matthew Wilcox <willy@infradead.org>
To: Gao Xiang <gaoxiang25@huawei.com>,
Dave Chinner <david@fromorbit.com>,
Goldwyn Rodrigues <RGoldwyn@suse.com>, "hch@lst.de" <hch@lst.de>,
"darrick.wong@oracle.com" <darrick.wong@oracle.com>,
"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
"ruansy.fnst@cn.fujitsu.com" <ruansy.fnst@cn.fujitsu.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
linux-erofs@lists.ozlabs.org, miaoxie@huawei.com
Subject: Re: [PATCH 10/13] iomap: use a function pointer for dio submits
Date: Fri, 9 Aug 2019 13:45:17 -0700 [thread overview]
Message-ID: <20190809204517.GR5482@bombadil.infradead.org> (raw)
In-Reply-To: <20190808054936.GA5319@sol.localdomain>
On Wed, Aug 07, 2019 at 10:49:36PM -0700, Eric Biggers wrote:
> On Thu, Aug 08, 2019 at 12:26:42PM +0800, Gao Xiang wrote:
> > 1. decrypt->verity->decompress
> >
> > 2. verity->decompress->decrypt
> >
> > 3. decompress->decrypt->verity
> >
> > 1. and 2. could cause less computation since it processes
> > compressed data, and the security is good enough since
> > the behavior of decompression algorithm is deterministic.
> > 3 could cause more computation.
> >
> > All I want to say is the post process is so complicated since we have
> > many selection if encryption, decompression, verification are all involved.
> >
> > Maybe introduce a core subset to IOMAP is better for long-term
> > maintainment and better performance. And we should consider it
> > more carefully.
> >
>
> FWIW, the only order that actually makes sense is decrypt->decompress->verity.
That used to be true, but a paper in 2004 suggested it's not true.
Further work in this space in 2009 based on block ciphers:
https://arxiv.org/pdf/1009.1759
It looks like it'd be computationally expensive to do, but feasible.
> Decrypt before decompress, i.e. encrypt after compress, because only the
> plaintext can be compressible; the ciphertext isn't.
WARNING: multiple messages have this Message-ID (diff)
From: willy@infradead.org (Matthew Wilcox)
Subject: [PATCH 10/13] iomap: use a function pointer for dio submits
Date: Fri, 9 Aug 2019 13:45:17 -0700 [thread overview]
Message-ID: <20190809204517.GR5482@bombadil.infradead.org> (raw)
In-Reply-To: <20190808054936.GA5319@sol.localdomain>
On Wed, Aug 07, 2019@10:49:36PM -0700, Eric Biggers wrote:
> On Thu, Aug 08, 2019@12:26:42PM +0800, Gao Xiang wrote:
> > 1. decrypt->verity->decompress
> >
> > 2. verity->decompress->decrypt
> >
> > 3. decompress->decrypt->verity
> >
> > 1. and 2. could cause less computation since it processes
> > compressed data, and the security is good enough since
> > the behavior of decompression algorithm is deterministic.
> > 3 could cause more computation.
> >
> > All I want to say is the post process is so complicated since we have
> > many selection if encryption, decompression, verification are all involved.
> >
> > Maybe introduce a core subset to IOMAP is better for long-term
> > maintainment and better performance. And we should consider it
> > more carefully.
> >
>
> FWIW, the only order that actually makes sense is decrypt->decompress->verity.
That used to be true, but a paper in 2004 suggested it's not true.
Further work in this space in 2009 based on block ciphers:
https://arxiv.org/pdf/1009.1759
It looks like it'd be computationally expensive to do, but feasible.
> Decrypt before decompress, i.e. encrypt after compress, because only the
> plaintext can be compressible; the ciphertext isn't.
next prev parent reply other threads:[~2019-08-09 20:45 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-02 22:00 [PATCH v2 0/13] Btrfs iomap Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 01/13] iomap: Use a IOMAP_COW/srcmap for a read-modify-write I/O Goldwyn Rodrigues
2019-08-03 0:39 ` Darrick J. Wong
2019-08-05 0:06 ` Dave Chinner
2019-08-02 22:00 ` [PATCH 02/13] iomap: Read page from srcmap for IOMAP_COW Goldwyn Rodrigues
2019-08-03 0:23 ` Darrick J. Wong
2019-08-04 23:52 ` Dave Chinner
2019-08-02 22:00 ` [PATCH 03/13] btrfs: Eliminate PagePrivate for btrfs data pages Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 04/13] btrfs: Add a simple buffered iomap write Goldwyn Rodrigues
2019-08-05 0:11 ` Dave Chinner
2019-08-22 15:05 ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 05/13] btrfs: Add CoW in iomap based writes Goldwyn Rodrigues
2019-08-05 0:13 ` Dave Chinner
2019-08-22 15:01 ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 06/13] btrfs: remove buffered write code made unnecessary Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 07/13] btrfs: basic direct read operation Goldwyn Rodrigues
2019-08-12 12:32 ` RITESH HARJANI
2019-08-22 15:00 ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 08/13] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 09/13] btrfs: Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 10/13] iomap: use a function pointer for dio submits Goldwyn Rodrigues
2019-08-03 0:21 ` Darrick J. Wong
2019-08-05 16:08 ` Goldwyn Rodrigues
2019-08-04 23:43 ` Dave Chinner
2019-08-05 16:08 ` Goldwyn Rodrigues
2019-08-05 21:54 ` Dave Chinner
2019-08-08 4:26 ` Gao Xiang
2019-08-08 4:26 ` Gao Xiang
2019-08-08 4:52 ` Gao Xiang
2019-08-08 4:52 ` Gao Xiang
2019-08-08 5:49 ` Eric Biggers
2019-08-08 5:49 ` Eric Biggers
2019-08-08 6:28 ` Gao Xiang
2019-08-08 6:28 ` Gao Xiang
2019-08-08 8:16 ` Dave Chinner
2019-08-08 8:16 ` Dave Chinner
2019-08-08 8:57 ` Gao Xiang
2019-08-08 8:57 ` Gao Xiang
2019-08-08 9:29 ` Gao Xiang
2019-08-08 9:29 ` Gao Xiang
2019-08-08 11:21 ` Gao Xiang
2019-08-08 11:21 ` Gao Xiang
2019-08-08 13:11 ` Gao Xiang
2019-08-08 13:11 ` Gao Xiang
2019-08-09 20:45 ` Matthew Wilcox [this message]
2019-08-09 20:45 ` Matthew Wilcox
2019-08-09 23:45 ` Gao Xiang
2019-08-09 23:45 ` Gao Xiang
2019-08-10 0:31 ` Eric Biggers
2019-08-10 0:31 ` Eric Biggers
2019-08-10 0:50 ` Eric Biggers
2019-08-10 0:50 ` Eric Biggers
2019-08-10 1:34 ` Gao Xiang
2019-08-10 1:34 ` Gao Xiang
2019-08-10 1:13 ` Gao Xiang
2019-08-10 1:13 ` Gao Xiang
2019-08-10 0:17 ` Eric Biggers
2019-08-10 0:17 ` Eric Biggers
2019-08-02 22:00 ` [PATCH 11/13] btrfs: Use iomap_dio_rw for performing direct I/O writes Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 12/13] btrfs: Remove btrfs_dio_data and __btrfs_direct_write Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 13/13] btrfs: update inode size during bio completion Goldwyn Rodrigues
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190809204517.GR5482@bombadil.infradead.org \
--to=willy@infradead.org \
--cc=RGoldwyn@suse.com \
--cc=darrick.wong@oracle.com \
--cc=david@fromorbit.com \
--cc=gaoxiang25@huawei.com \
--cc=hch@lst.de \
--cc=linux-btrfs@vger.kernel.org \
--cc=linux-erofs@lists.ozlabs.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=miaoxie@huawei.com \
--cc=ruansy.fnst@cn.fujitsu.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.