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From: Duy Nguyen <pclouds@gmail.com>
To: Jeff King <peff@peff.net>
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Luc Van Oostenryck" <luc.vanoostenryck@gmail.com>,
	git@vger.kernel.org, "Kevin Willford" <kewillf@microsoft.com>
Subject: Re: [BUG] index corruption with git commit -p
Date: Sun, 2 Sep 2018 09:12:04 +0200	[thread overview]
Message-ID: <20180902071204.GA2868@duynguyen.home> (raw)
In-Reply-To: <20180902050803.GA21324@sigill.intra.peff.net>

On Sun, Sep 02, 2018 at 01:08:03AM -0400, Jeff King wrote:
> On Sun, Sep 02, 2018 at 12:17:53AM +0200, Ævar Arnfjörð Bjarmason wrote:
> 
> > > Here are the steps to reproduce it:
> > >   $ git clone git://github.com/lucvoo/sparse-dev.git <somedir>
> > >   $ cd <somedir>
> > >   $ git co index-corruption
> > >   $ git rm -r validation/ Documentation/
> > >   $ git commit -m <some message> -p
> > >   $ git status
> > > error: index uses $?+? extension, which we do not understand
> > > fatal: index file corrupt
> > >
> > > The 'extension' pattern '$?+?', can vary a bit, sometimes
> > > it's just '????', but always seems 4 chars.
> > > If the commit command doesn't use the '-p' flag, there is no
> > > problem. The repository itself is not corrupted, it's only
> > > the index. It happends with git 2.18.0 and 2.17.0
> > 
> > Yeah this is a bug, I didn't dig much but testing with this script down
> > to 2.8.0:
> > [...]
> > I found that the first bad commit was: 680ee550d7 ("commit: skip
> > discarding the index if there is no pre-commit hook", 2017-08-14)
> 
> I think it's much older than that. I set up my test repo like this:
> 
>   git clone git://github.com/lucvoo/sparse-dev.git
>   cd sparse-dev
>   git checkout --detach
> 
> and then bisected with this script:
> 
>   cd /path/to/sparse-dev
>   rm .git/index
>   git reset --hard index-corruption &&
>   git rm -q -r validation/ Documentation/ &&
>   git commit -qm foo -p &&
>   git status
> 
> Since a33fc72fe9 (read-cache: force_verify_index_checksum, 2017-04-14),
> that produces the corrupt extension error. But before that, I
> consistently get:
> 
>   error: bad index file sha1 signature
>   fatal: index file corrupt
> 
> from git-commit. And that bisects back to 9c4d6c0297 (cache-tree: Write
> updated cache-tree after commit, 2014-07-13).
> 
> If I revert that commit (which takes some untangling, see below), then
> the problem seems to go away. Here's the patch I tried on top of the
> current master, though I think it is actually the first hunk that is
> making the difference.
> 
> ---
> diff --git a/builtin/commit.c b/builtin/commit.c
> index 0d9828e29e..779c5e2cb5 100644
> --- a/builtin/commit.c
> +++ b/builtin/commit.c
> @@ -359,13 +359,6 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
>  
>  		discard_cache();
>  		read_cache_from(get_lock_file_path(&index_lock));
> -		if (update_main_cache_tree(WRITE_TREE_SILENT) == 0) {
> -			if (reopen_lock_file(&index_lock) < 0)
> -				die(_("unable to write index file"));
> -			if (write_locked_index(&the_index, &index_lock, 0))
> -				die(_("unable to update temporary index"));
> -		} else
> -			warning(_("Failed to update main cache tree"));
>

Narrowing down to this does help. This patch seems to fix it to me. I
guess we have some leftover from the interactive add that should not
be there after we have written the new index.

diff --git a/builtin/commit.c b/builtin/commit.c
index 2be7bdb331..60f30b3780 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -432,6 +432,7 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
 		if (update_main_cache_tree(WRITE_TREE_SILENT) == 0) {
 			if (reopen_lock_file(&index_lock) < 0)
 				die(_("unable to write index file"));
+			ftruncate(index_lock.tempfile->fd, 0);
 			if (write_locked_index(&the_index, &index_lock, 0))
 				die(_("unable to update temporary index"));
 		} else


--
Duy

  reply	other threads:[~2018-09-02  7:18 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-01 21:41 [BUG] index corruption with git commit -p Luc Van Oostenryck
2018-09-01 22:17 ` Ævar Arnfjörð Bjarmason
2018-09-02  5:08   ` Jeff King
2018-09-02  7:12     ` Duy Nguyen [this message]
2018-09-02  7:24       ` Jeff King
2018-09-02  7:53         ` Luc Van Oostenryck
2018-09-02  8:02           ` Jeff King
2018-09-04 15:57         ` Junio C Hamano
2018-09-04 16:13           ` Duy Nguyen
2018-09-04 16:38             ` Jeff King
2018-09-04 23:36               ` [PATCH] reopen_tempfile(): truncate opened file Jeff King
2018-09-05 15:27                 ` Duy Nguyen
2018-09-05 15:35                   ` Jeff King
2018-09-05 15:39                     ` Duy Nguyen
2018-09-05 15:48                       ` Jeff King
2018-09-05 16:54                         ` Junio C Hamano
2018-09-05 16:56                           ` Jeff King
2018-09-05 17:01                             ` Junio C Hamano
2018-09-05 18:48                 ` Luc Van Oostenryck

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