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From: Matthew Wilcox <willy@infradead.org>
To: "Theodore Y. Ts'o" <tytso@mit.edu>,
	Christoph Hellwig <hch@infradead.org>,
	Dave Chinner <david@fromorbit.com>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Eric Biggers <ebiggers@kernel.org>,
	linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-ext4@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jaegeuk Kim <jaegeuk@kernel.org>,
	Victor Hsieh <victorhsieh@google.com>,
	Chandan Rajendra <chandan@linux.vnet.ibm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v2 01/12] fs-verity: add a documentation file
Date: Fri, 21 Dec 2018 08:34:38 -0800	[thread overview]
Message-ID: <20181221163438.GE10600@bombadil.infradead.org> (raw)
In-Reply-To: <20181221162813.GB26547@mit.edu>

On Fri, Dec 21, 2018 at 11:28:13AM -0500, Theodore Y. Ts'o wrote:
> On Fri, Dec 21, 2018 at 07:53:54AM -0800, Matthew Wilcox wrote:
> > In contrast to "we'll just fix it up later" (which usually applies
> > to in-kernel interfaces), we have a policy of not breaking userspace,
> > so accepting this interface means setting it in stone.  We should get
> > it right.
> 
> I'm not convinced it's a "fix", but my point is that if later on you
> want to add extra complexity transforming
> 
>      ioctl(fd, FS_IOC_ENABLE_VERITY);
> 
> so it does the equivalent of
> 
>      ioctl(fd, FS_IOC_ENABLE_VERITY_NOW_WITH_EXTRA_USELESS_COMPLEXITY,
> 	   fd, sizeof_data, sizeof_verity_data);

I disagree with your EXTRA_USELESS_COMPLEXITY appendage.  The interface
you designed reflects the implementation you did in ext4, so I understand
why it seems simple from your point of view.  From the user point of view,
it looks completely weird.  You write a file, being a series of bytes,
then all of a sudden have to know that it's composed of blocks, seek
to the next block, write a header, then this Merkle data structure,
then write a footer which isn't allowed to cross a block boundary
for some unknowable reason.  It seems much more logical to have the
header+Merkle+footer as a separate data stream which the filesystem can
then layout according to its own rules.

  reply	other threads:[~2018-12-21 16:34 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01 22:52 [PATCH v2 00/12] fs-verity: read-only file-based authenticity protection Eric Biggers
2018-11-01 22:52 ` [PATCH v2 01/12] fs-verity: add a documentation file Eric Biggers
2018-12-12  9:14   ` Christoph Hellwig
2018-12-12 20:26     ` Eric Biggers
2018-12-13 20:22       ` Christoph Hellwig
2018-12-14  4:48         ` Eric Biggers
2018-12-17 16:49           ` Christoph Hellwig
2018-12-17 18:32             ` Eric Biggers
2018-12-19  7:09               ` Christoph Hellwig
2018-12-17 20:00           ` Darrick J. Wong
2018-12-19  0:16             ` Theodore Y. Ts'o
2018-12-19  2:19               ` Dave Chinner
2018-12-19 19:30                 ` Theodore Y. Ts'o
2018-12-19 21:35                   ` Dave Chinner
2018-12-20 22:01                     ` Theodore Y. Ts'o
2018-12-21  7:04                       ` Christoph Hellwig
2018-12-21 10:06                         ` Richard Weinberger
2018-12-21 15:47                         ` Theodore Y. Ts'o
2018-12-21 15:53                           ` Matthew Wilcox
2018-12-21 16:28                             ` Theodore Y. Ts'o
2018-12-21 16:34                               ` Matthew Wilcox [this message]
2018-12-21 19:13                           ` Linus Torvalds
2018-12-22  4:17                             ` Theodore Y. Ts'o
2018-12-22 22:47                               ` Linus Torvalds
2018-12-23  4:34                                 ` Theodore Y. Ts'o
2018-12-23  4:10                               ` Matthew Wilcox
2018-12-23  4:45                                 ` Theodore Y. Ts'o
2019-01-04 20:41                                   ` Daniel Colascione
2018-12-19  7:14               ` Christoph Hellwig
2018-12-19  7:11             ` Christoph Hellwig
     [not found]               ` <CAHk-=wiB8vGbje+NgNkMZupHsZ_cqg6YEBV+ZXSF4wnywFLRHQ@mail.gmail.com>
2018-12-19  7:19                 ` Christoph Hellwig
2018-12-14  5:17         ` Theodore Y. Ts'o
2018-12-14  5:39           ` Eric Biggers
2018-12-17 16:52           ` Christoph Hellwig
2018-12-17 19:15             ` Eric Biggers
2018-12-21 16:11   ` Matthew Wilcox
2018-11-01 22:52 ` [PATCH v2 02/12] fs-verity: add setup code, UAPI, and Kconfig Eric Biggers
2018-11-01 22:52 ` [PATCH v2 03/12] fs-verity: add MAINTAINERS file entry Eric Biggers
2018-11-01 22:52 ` [PATCH v2 04/12] fs-verity: add data verification hooks for ->readpages() Eric Biggers
2018-11-01 22:52 ` [PATCH v2 05/12] fs-verity: implement FS_IOC_ENABLE_VERITY ioctl Eric Biggers
2018-11-01 22:52 ` [PATCH v2 06/12] fs-verity: implement FS_IOC_MEASURE_VERITY ioctl Eric Biggers
2018-11-01 22:52 ` [PATCH v2 07/12] fs-verity: add SHA-512 support Eric Biggers
2018-11-01 22:52 ` [PATCH v2 08/12] fs-verity: add CRC-32C support Eric Biggers
2018-11-01 22:52 ` [PATCH v2 09/12] fs-verity: support builtin file signatures Eric Biggers
2018-11-01 22:52 ` [PATCH v2 10/12] ext4: add basic fs-verity support Eric Biggers
2018-11-02  9:43   ` Chandan Rajendra
2018-11-06  1:25     ` Eric Biggers
2018-11-06  6:52       ` Chandan Rajendra
2018-11-05 21:05   ` Andreas Dilger
2018-11-06  1:11     ` Eric Biggers
2018-11-01 22:52 ` [PATCH v2 11/12] ext4: add fs-verity read support Eric Biggers
2018-11-01 22:52 ` [PATCH v2 12/12] f2fs: fs-verity support Eric Biggers

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