Subject: Re: [PATCH] fsck: do not loop infinitely when processing packs

From: Patrick Steinhardt <[email-masked]>
Date: Mon, 23 Feb 2026 10:36:25 +0100

On Mon, Feb 23, 2026 at 04:25:23AM -0500, Jeff King wrote:
> On Mon, Feb 23, 2026 at 09:46:00AM +0100, Patrick Steinhardt wrote:
> 
> > As pointed out in [1] the root cause is actually something different,
> > and we merely expose this now with the MRU-based iteration. But I
> > wouldn't mind if we eventually switched back to maintaining two lists,
> > or finding a different way for how to maintain the iteration order.
> 
> Maybe I don't understand what you're saying, but isn't the root cause
> the same?
> 
> Code is iterating the list, and then during that iteration calls
> find_pack_entry(). The fact that fsck only calls find_pack_entry() in
> some subset of cases is immaterial, I'd think. The risk is always there
> when iterating now.

It is, true. All I'm saying is that the problem runs a bit deeper, and
that fixing the actual root cause would also fix the issue reported by
brian.

So we might want to have another look at hardening packfile iteration
either by reinstating the second list for iteration or by extending
`repo_for_each_pack()` to also set the `skip_updating_mru` bit. Over
time though I'd rather get rid of `repo_for_each_pack()`, and once that
is the case and packed object iteration is neatly encapsulated in the
backend the risk of only having the MRU will be significantly reduced.

Thanks!

Patrick