From: Jeff King <peff@peff.net>
To: demerphq <demerphq@gmail.com>
Cc: Git <git@vger.kernel.org>, "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: Re: Bug: git branch --unset-upstream command can nuke config when disk is full.
Date: Wed, 13 Sep 2017 08:34:21 -0400 [thread overview]
Message-ID: <20170913123420.die3thfcpaweakce@sigill.intra.peff.net> (raw)
In-Reply-To: <CANgJU+Wj_sN8Px6rweHMw_iAX8UA3mW9x4NVCctpUCs8_3ytLw@mail.gmail.com>
On Wed, Sep 13, 2017 at 01:59:17PM +0200, demerphq wrote:
> After being away for a while I saw the following message in one of my git repos:
>
> $ git status
> On branch yves/xxx
> Your branch is based on 'origin/yves/xxx', but the upstream is gone.
> (use "git branch --unset-upstream" to fixup)
>
> nothing to commit, working tree clean
> $ git branch --unset-upstream
> fatal: could not unset 'branch.yves/simple_projection.merge'
Hrm. I wonder what caused this failure. The error would be in
git_config_set_multivar_in_file_gently(). Most errors there produce
another error message before hitting the die(). In fact, the only case I
see where it would not produce another message is if it found nothing to
unset (but in that case, "branch" would never have called the function
in the first place).
> At this point my .git/config file was empty, and all of my config was lost.
>
> I assume that things that rewrite .git/config do not check for a
> successful write before deleting the old version of the file.
No, it writes the new content to "config.lock" and then renames it into
place. All of the write() calls to the temporary file are checked. The
old data is copied over after having been ready by mmap (which is also
error-checked).
Given that your output is consistent with it failing to find the key,
and that the result is an empty file, it sounds like somehow the mmap'd
input appeared empty (but neither open nor fstat nor mmap returned an
error). You're not on any kind of exotic filesystem, are you?
-Peff
next prev parent reply other threads:[~2017-09-13 12:34 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-13 11:59 Bug: git branch --unset-upstream command can nuke config when disk is full demerphq
2017-09-13 12:34 ` Jeff King [this message]
2017-09-13 13:38 ` demerphq
2017-09-13 14:17 ` Jeff King
2017-09-13 14:49 ` demerphq
2017-09-13 14:51 ` Jeff King
2017-09-13 15:18 ` demerphq
2017-09-13 15:22 ` Jeff King
2017-09-13 15:49 ` demerphq
2017-09-13 17:08 ` [PATCH 0/7] config.c may fail to notice some write() failures Jeff King
2017-09-13 17:11 ` [PATCH 1/7] config: avoid "write_in_full(fd, buf, len) < len" pattern Jeff King
2017-09-13 17:47 ` Jonathan Nieder
2017-09-13 17:53 ` Jeff King
2017-09-13 17:59 ` Jonathan Nieder
2017-09-13 18:11 ` Jeff King
2017-09-13 18:15 ` [PATCH v2] " Jeff King
2017-09-13 18:24 ` Jonathan Nieder
2017-09-13 18:58 ` Jeff King
2017-09-13 19:18 ` Jonathan Nieder
2017-09-13 19:49 ` Jonathan Nieder
2017-09-13 22:43 ` Ramsay Jones
2017-09-13 23:31 ` Ramsay Jones
2017-09-15 0:37 ` Jeff King
2017-09-15 15:15 ` Ramsay Jones
2017-09-13 21:33 ` Junio C Hamano
2017-09-13 17:11 ` [PATCH 2/7] get-tar-commit-id: check write_in_full() return against 0 Jeff King
2017-09-13 17:53 ` Jonathan Nieder
2017-09-13 18:02 ` Jeff King
2017-09-13 18:37 ` Jeff King
2017-09-13 21:09 ` Jonathan Nieder
2017-09-15 0:40 ` Jeff King
2017-09-13 17:16 ` [PATCH 3/7] avoid "write_in_full(fd, buf, len) != len" pattern Jeff King
2017-09-13 21:14 ` Jonathan Nieder
2017-09-15 0:42 ` Jeff King
2017-09-13 17:16 ` [PATCH 4/7] convert less-trivial versions of "write_in_full() != len" Jeff King
2017-09-13 21:16 ` Jonathan Nieder
2017-09-13 17:17 ` [PATCH 5/7] pkt-line: check write_in_full() errors against "< 0" Jeff King
2017-09-13 21:17 ` Jonathan Nieder
2017-09-13 17:17 ` [PATCH 6/7] notes-merge: use ssize_t for write_in_full() return value Jeff King
2017-09-13 21:20 ` Jonathan Nieder
2017-09-15 0:43 ` Jeff King
2017-09-13 17:17 ` [PATCH 7/7] config: flip return value of store_write_*() Jeff King
2017-09-13 21:25 ` Jonathan Nieder
2017-09-15 0:46 ` Jeff King
2017-09-13 18:47 ` [PATCH 8/7] read_pack_header: handle signed/unsigned comparison in read result Jeff King
2017-09-13 19:11 ` Jonathan Nieder
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