All of lore.kernel.org
 help / color / mirror / Atom feed
From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: git@vger.kernel.org, tytso@mit.edu,
	Junio C Hamano <gitster@pobox.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC PATCH 1/2] sha1-file: fsync() loose dir entry when core.fsyncObjectFiles
Date: Tue, 22 Sep 2020 12:42:37 +0200	[thread overview]
Message-ID: <877dsmhz36.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <20200917140912.GA27653@lst.de>


On Thu, Sep 17 2020, Christoph Hellwig wrote:

> On Thu, Sep 17, 2020 at 01:28:29PM +0200, Ævar Arnfjörð Bjarmason wrote:
>> Change the behavior of core.fsyncObjectFiles to also sync the
>> directory entry. I don't have a case where this broke, just going by
>> paranoia and the fsync(2) manual page's guarantees about its behavior.
>
> It is not just paranoia, but indeed what is required from the standards
> POV.  At least for many Linux file systems your second fsync will be
> very cheap (basically a NULL syscall) as the log has alredy been forced
> all the way by the first one, but you can't rely on that.
>
> Acked-by: Christoph Hellwig <hch@lst.de>

Thanks a lot for your advice in this thread.

Can you (or someone else) suggest a Linux fs setup that's as unforgiving
as possible vis-a-vis fsync() for testing? I'd like to hack on making
git better at this, but one of the problems of testing it is that modern
filesystems generally do a pretty good job of not losing your data.

So something like ext4's commit=N is an obvious start, but for git's own
test suite it would be ideal to have process A write file X, and then
have process B try to read it and just not see it if X hadn't been
fsynced (or not see its directory if that hadn't been synced).

It would turn our test suite into pretty much a 100% failure, but one
that could then be fixed by fixing the relevant file writing code.

  parent reply	other threads:[~2020-09-22 10:42 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-17 18:48 [PATCH] enable core.fsyncObjectFiles by default Christoph Hellwig
2018-01-17 19:04 ` Junio C Hamano
2018-01-17 19:35   ` Christoph Hellwig
2018-01-17 19:35     ` Christoph Hellwig
2018-01-17 20:05     ` Andreas Schwab
2018-01-17 19:37   ` Matthew Wilcox
2018-01-17 19:42     ` Christoph Hellwig
2018-01-17 21:44   ` Ævar Arnfjörð Bjarmason
2018-01-17 22:07     ` Linus Torvalds
2018-01-17 22:25       ` Linus Torvalds
2018-01-17 23:16       ` Ævar Arnfjörð Bjarmason
2018-01-17 23:42         ` Linus Torvalds
2018-01-17 23:52       ` Theodore Ts'o
2018-01-17 23:57         ` Linus Torvalds
2018-01-18 16:27           ` Christoph Hellwig
2018-01-19 19:08             ` Junio C Hamano
2018-01-20 22:14               ` Theodore Ts'o
2018-01-20 22:27                 ` Junio C Hamano
2018-01-22 15:09                   ` Ævar Arnfjörð Bjarmason
2018-01-22 18:09                     ` Theodore Ts'o
2018-01-22 18:09                       ` Theodore Ts'o
2018-01-23  0:47                       ` Jeff King
2018-01-23  5:45                         ` Theodore Ts'o
2018-01-23  5:45                           ` Theodore Ts'o
2018-01-23 16:17                           ` Jeff King
2018-01-23  0:25                     ` Jeff King
2018-01-21 21:32             ` Chris Mason
2020-09-17 11:06         ` Ævar Arnfjörð Bjarmason
2020-09-17 11:28           ` [RFC PATCH 0/2] should core.fsyncObjectFiles fsync the dir entry + docs Ævar Arnfjörð Bjarmason
2020-09-17 11:28           ` [RFC PATCH 1/2] sha1-file: fsync() loose dir entry when core.fsyncObjectFiles Ævar Arnfjörð Bjarmason
2020-09-17 13:16             ` Jeff King
2020-09-17 15:09               ` Christoph Hellwig
2020-09-17 14:09             ` Christoph Hellwig
2020-09-17 14:55               ` Jeff King
2020-09-17 14:56                 ` Christoph Hellwig
2020-09-17 15:37                   ` Junio C Hamano
2020-09-17 17:12                     ` Jeff King
2020-09-17 20:37                       ` Taylor Blau
2020-09-22 10:42               ` Ævar Arnfjörð Bjarmason [this message]
2020-09-17 20:21             ` Johannes Sixt
2020-09-22  8:24               ` Ævar Arnfjörð Bjarmason
2020-11-19 11:38                 ` Johannes Schindelin
2020-09-17 11:28           ` [RFC PATCH 2/2] core.fsyncObjectFiles: make the docs less flippant Ævar Arnfjörð Bjarmason
2020-09-17 14:12             ` Christoph Hellwig
2020-09-17 15:43             ` Junio C Hamano
2020-09-17 20:15               ` Johannes Sixt
2020-10-08  8:13               ` Johannes Schindelin
2020-10-08 15:57                 ` Ævar Arnfjörð Bjarmason
2020-10-08 18:53                   ` Junio C Hamano
2020-10-09 10:44                   ` Johannes Schindelin
2020-09-17 19:21             ` Marc Branchaud
2020-09-17 14:14           ` [PATCH] enable core.fsyncObjectFiles by default Christoph Hellwig
2020-09-17 15:30           ` Junio C Hamano
2018-01-17 20:55 ` Jeff King
2018-01-17 21:10   ` Christoph Hellwig

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=877dsmhz36.fsf@evledraar.gmail.com \
    --to=avarab@gmail.com \
    --cc=git@vger.kernel.org \
    --cc=gitster@pobox.com \
    --cc=hch@lst.de \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=torvalds@linux-foundation.org \
    --cc=tytso@mit.edu \
    /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.