From: David Emett <dave@sp4m.net>
To: git@vger.kernel.org
Subject: Two issues with mark_reachable_objects
Date: Tue, 27 Apr 2021 11:45:01 +0100 [thread overview]
Message-ID: <CAJ-dYSOVx0egnyxJb6ZjgWvEDR=19QPgc70JQ7cXUjUPZ1XDiQ@mail.gmail.com> (raw)
Hi all,
I ran into an issue yesterday with a script that effectively does this:
set -e
git fetch origin refs/blah/blah
git checkout FETCH_HEAD
The checkout failed a few times with a "fatal: unable to read tree" error.
I noticed that this only happened when the fetch triggered an automatic GC at
the end. After a bit of digging I discovered two separate issues:
1) It seems that FETCH_HEAD is not considered a root by mark_reachable_objects.
2) If the bitmap_git branch in mark_reachable_objects is taken, the mark_recent
argument is ignored. This doesn't _completely_ break "git prune"'s --expire
option, as it turns out there is another explicit mtime check in
prune_object (prune.c). If that check passes this is not propagated to
referenced objects though. So even if a dangling commit is recent, a prune
can discard old objects it references.
(1) has been discussed before on this mailing list [1], but it doesn't look
like there was a conclusion.
I assume (2) is not intentional, given that "git gc --help" explicitly says
"Any object with modification time newer than the --prune date is kept, along
with everything reachable from it." Is it safe to just run the mark_recent
block after the bitmap_git block? Could add_unseen_recent_objects_to_traversal
just be called at the start of the bitmap_git block if mark_recent?
[1] https://lore.kernel.org/git/20160708025948.GA3226@x/
next reply other threads:[~2021-04-27 10:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-27 10:45 David Emett [this message]
2021-04-27 14:41 ` Two issues with mark_reachable_objects Jeff King
2021-04-27 15:13 ` Jeff King
2021-04-27 15:43 ` [PATCH] prune: save reachable-from-recent objects with bitmaps Jeff King
2021-04-28 12:20 ` David Emett
2021-04-28 15:13 ` Jeff King
2021-04-28 15:41 ` [PATCH v2 0/2] " Jeff King
2021-04-28 15:42 ` [PATCH v2 1/2] pack-bitmap: clean up include_check after use Jeff King
2021-04-28 15:42 ` [PATCH v2 2/2] prune: save reachable-from-recent objects with bitmaps Jeff King
2021-04-29 1:37 ` Junio C Hamano
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