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.
next prev parent reply other threads:[~2020-09-22 10:42 UTC|newest]
Thread overview: 52+ 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 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
2018-01-23 0:47 ` Jeff King
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
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