Re: repository corruption when pushing commits to a repository running 'git gc --prune='

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 14, 2015, 20:05 UTC
Message-ID: <xmqq7fmp8bcf.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <vpqbnc18ezo.fsf@grenoble-inp.fr>

Matthieu Moy <Matthieu.Moy@grenoble-inp.fr> writes:

Show 8 quoted lines

> This looks like a race between deleting objects/05/ and creating
> objects/05/cdb51bb0ea3e229734a4b1bddd5ec70fbc65ed.
>
> I don't understand how this is possible, since the temporary file and
> the final one are in the same directory, so deleting the directory
> should fail.
>
> What am I missing?

 1. tmp_obj_* gets created in objects/05/ by "git unpack-objects";

 2. prune_cruft() comes, notices tmp_obj_* that is sufficiently old,
    decides to remove in "git prune".

 3. prune_subdir() comes, notices objects/05/ is now empty, does
    rmdir().

 4. "git unpack-objects" closes the file whose inode was originally
    associated with the path objects/05/tmp_obj_*;

 5. "git unpack-objects" calls finalize_object_file() and tries to
    link(2) or rename(2) it to its final name.  It does not find the
    source of the link or rename and says "oops, no such file".