From: Gao Xiang <gaoxiang25@huawei.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Eric Biggers <ebiggers@kernel.org>,
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: Thu, 8 Aug 2019 19:21:39 +0800 [thread overview]
Message-ID: <20190808112139.GG28630@138> (raw)
In-Reply-To: <20190808091632.GF28630@138>
On Thu, Aug 08, 2019 at 05:29:47PM +0800, Gao Xiang wrote:
> On Thu, Aug 08, 2019 at 06:16:47PM +1000, Dave Chinner wrote:
> > On Wed, Aug 07, 2019 at 10:49:36PM -0700, Eric Biggers wrote:
> > > FWIW, the only order that actually makes sense is decrypt->decompress->verity.
> >
> > *nod*
> >
> > Especially once we get the inline encryption support for fscrypt so
> > the storage layer can offload the encrypt/decrypt to hardware via
> > the bio containing plaintext. That pretty much forces fscrypt to be
> > the lowest layer of the filesystem transformation stack. This
> > hardware offload capability also places lots of limits on what you
> > can do with block-based verity layers below the filesystem. e.g.
> > using dm-verity when you don't know if there's hardware encryption
> > below or software encryption on top becomes problematic...
...and I'm not talking of fs-verity, I personally think fs-verity
is great. I am only talking about a generic stuff.
In order to know which level becomes problematic, there even could
be another choice "decrypt->verity1->decompress->verity2" for such
requirement (assuming verity1/2 themselves are absolutely bug-free),
verity1 can be a strong merkle tree and verity2 is a weak form (just
like a simple Adler-32/crc32 in compressed block), thus we can locate
whether it's a decrypt or decompress bug.
Many compression algorithm containers already have such a weak
form such as gzip algorithm, so there is no need to add such
an extra step to postprocess.
and I have no idea which (decrypt->verity1->decompress->verity2 or
decrypt->decompress->verity) is faster since verity2 is rather simple.
However, if we use the only strong form in the end, there could be
a lot of extra IO and expensive multiple-level computations if files
are highly compressible.
On the other hand, such verity2 can be computed offline / avoided
by fuzzer tools for read-only scenerios (for example, after building
these images and do a full image verification with the given kernel)
in order to make sure its stability (In any case, I'm talking about
how to make those algorithms bug-free).
All I want to say is I think "decrypt->verity->decompress" is
reasonable as well.
Thanks,
Gao Xiang
>
> Add a word, I was just talking benefits between "decrypt->decompress->
> verity" and "decrypt->verity->decompress", I think both forms are
> compatible with inline en/decryption. I don't care which level
> "decrypt" is at... But maybe some user cares. Am I missing something?
>
> Thanks,
> Gao Xiang
>
next prev parent reply other threads:[~2019-08-08 11:04 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 [this message]
2019-08-08 13:11 ` Gao Xiang
2019-08-09 20:45 ` Matthew Wilcox
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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