From: Christoph Hellwig <hch@lst.de>
To: Jeff King <peff@peff.net>
Cc: Christoph Hellwig <hch@lst.de>,
git@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] enable core.fsyncObjectFiles by default
Date: Wed, 17 Jan 2018 22:10:11 +0100 [thread overview]
Message-ID: <20180117211011.GA355@lst.de> (raw)
In-Reply-To: <20180117205509.GA14828@sigill.intra.peff.net>
On Wed, Jan 17, 2018 at 03:55:09PM -0500, Jeff King wrote:
> I'm definitely sympathetic, and I've contemplated a patch like this a
> few times. But I'm not sure we're "safe by default" here after this
> patch. In particular:
>
> 1. This covers only loose objects. We generally sync pack writes
> already, so we're covered there. But we do not sync ref updates at
> all, which we'd probably want to in a default-safe setup (a common
> post-crash symptom I've seen is zero-length ref files).
I've not seen them myself yet, but yes, they need an fsync.
> 2. Is it sufficient to fsync() the individual file's descriptors?
> We often do other filesystem operations (like hardlinking or
> renaming) that also need to be committed to disk before an
> operation can be considered saved.
No, for metadata operations we need to fsync the directory as well.
> 3. Related to (2), we often care about the order of metadata commits.
> E.g., a common sequence is:
>
> a. Write object contents to tempfile.
>
> b. rename() or hardlink tempfile to final name.
>
> c. Write object name into ref.lock file.
>
> d. rename() ref.lock to ref
>
> If we see (d) but not (b), then the result is a corrupted
> repository. Is this guaranteed by ext4 journaling with
> data=ordered?
It is not generally guranteed by Linux file system semantics. Various
file system will actually start writeback of file data before rename,
but not actually wait on it.
next prev parent reply other threads:[~2018-01-17 21:10 UTC|newest]
Thread overview: 60+ 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
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 [this message]
-- strict thread matches above, loose matches on Subject: below --
2015-06-23 21:57 [PATCH] Enable " Stefan Beller
2015-06-23 22:21 ` Junio C Hamano
2015-06-23 23:29 ` Theodore Ts'o
2015-06-24 5:32 ` Junio C Hamano
2015-06-24 14:30 ` Theodore Ts'o
2015-06-24 1:07 ` Duy Nguyen
2015-06-24 3:37 ` Jeff King
2015-06-24 5:20 ` Junio C Hamano
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