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From: Junio C Hamano <gitster@pobox.com>
To: Theodore Ts'o <tytso@mit.edu>
Cc: Stefan Beller <sbeller@google.com>,
	git@vger.kernel.org, peff@peff.net,
	torvalds@linux-foundation.org
Subject: Re: [PATCH] Enable core.fsyncObjectFiles by default
Date: Tue, 23 Jun 2015 22:32:08 -0700
Message-ID: <xmqqegl1brjb.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <20150623232921.GB14324@thunk.org> (Theodore Ts'o's message of "Tue, 23 Jun 2015 19:29:21 -0400")

Theodore Ts'o <tytso@mit.edu> writes:

> The main issue is that non-expert users might not realize that they
> really need to run "git fsck" after a crash; otherwise, what might
> happen is that although git is only appending, that you might have
> some zero-length (or partially written) git object or pack files, and
> while you might not notice at that moment, it might come and bite you
> later.

Regarding loose object files, given that we write to a temporary,
optionally fsync, close and then move to the final name, would we
still see partially written file if we omit the fsync, or would the
corruption be limited to either empty or missing?

The reason I am wondering is because the codepath to create an
object (i.e. "update-index --add", "hash-object -w", or "add") first
checks if a packed or a loose object file _exists_ and if so
bypasses writing the same thing anew, but the existence check for a
loose object is to merely making sure that access(F_OK) (and
optionally utime()) succeeds.  If the potential breakage is limited
to truncation to empty, then we could replace it with stat(2) and
st.st_size check, as no loose object file can be empty.

  reply index

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-06-23 21:57 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 [this message]
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
2018-01-17 18:48 [PATCH] enable " 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 14:14           ` 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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