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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.

  parent reply	other threads:[~2019-08-09 20:45 UTC|newest]

Thread overview: 45+ 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  4:52           ` Gao Xiang
2019-08-08  5:49           ` Eric Biggers
2019-08-08  6:28             ` Gao Xiang
2019-08-08  8:16             ` Dave Chinner
2019-08-08  8:57               ` Gao Xiang
2019-08-08  9:29               ` Gao Xiang
2019-08-08 11:21                 ` Gao Xiang
2019-08-08 13:11                   ` Gao Xiang
2019-08-09 20:45             ` Matthew Wilcox [this message]
2019-08-09 23:45               ` Gao Xiang
2019-08-10  0:31                 ` Eric Biggers
2019-08-10  0:50                   ` Eric Biggers
2019-08-10  1:34                     ` Gao Xiang
2019-08-10  1:13                   ` Gao Xiang
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

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