Re: [PATCH] prune: save reachable-from-recent objects with bitmaps

From: David Emett <dave@sp4m.net>
Date: Apr 28, 2021, 12:20 UTC
Message-ID: <CAJ-dYSOHEfRq3p_MQMJoHf5PjwQtbJOzJ9Dzxrfe+BDkov7Q8w@mail.gmail.com>
In-Reply-To: <YIgxPtDmr9sYj0ft@coredump.intra.peff.net>

> Here's a fix. Thanks very much for reporting.

Thanks for the quick response! I tried the fix out on the repo I was having trouble with. It's hitting a segfault in traverse_commit_list in the mark_recent block. It looks like the issue is that the bitmap code leaves revs->include_check set, with revs->include_check_data pointing at the stack. Setting revs->include_check to NULL after the traverse_commit_list call in find_objects in pack-bitmap.c fixes the segfault for me. And the original issue appears to be resolved as well, so thanks!

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> I was a little surprised you saw this with "git gc", as when I tried
> testing with that, I found that the "git repack" run before "git prune"
> works around the bug (see the discussion of t6501 below). But I think
> perhaps it is just that "gc --auto" is more willing to do a "repack -d"
> sometimes, rather than a full "repack -A". At any rate, I was able to
> easily reproduce it for the tests with just git-prune.

I can't say for sure that this bug is what I was seeing originally, however it does seem quite likely -- the commits that hit issues were minor updates of commits that had been fetched a month or so earlier, and so would certainly fit the bill. Like you though I've just been reproducing with git prune.