Re: [PATCH v2 0/9] mm/huge_memory: refactor zap_huge_pmd()

Andrew Morton
2026-03-20T03:09:22Z

On Thu, 19 Mar 2026 13:00:06 +0000 "Lorenzo Stoakes (Oracle)" <ljs@kernel.org> wrote:

> The zap_huge_pmd() function is overly complicated, clean it up and also add
> an assert in the case that we encounter a buggy PMD entry that doesn't
> match expectations.
>
> This is motivated by a bug discovered [0] where the PMD entry was none of:
>
> * A non-DAX, PFN or mixed map.
> * The huge zero folio
> * A present PMD entry
> * A softleaf entry
>
> In zap_huge_pmd(), but due to the bug we manged to reach this code.
>
> It is useful to explicitly call this out rather than have an arbitrary NULL
> pointer dereference happen, which also improves understanding of what's
> going on.
>
> [0]:https://lore.kernel.org/all/6b3d7ad7-49e1-407a-903d-3103704160d8@lucifer.local/

AI review has questions, which I assume you've seen
https://sashiko.dev/#/patchset/cover.1773924928.git.ljs%40kernel.org

This isn't going well from a workflow POV. I merge stuff (this was v2)
then half a day later a bunch of potential issues are identified.

If these reviews are useful (they seem to be, enough) then I guess I'll
need to further increase the lag between seeing-it and merging-it. But
if there's a 2-day lag before I get onto a series and I'm the first to
look at Sashiko then that won't help.

So it needs to be something like

- series is posted
- 24 hours pass
- submitter takes a look at the AI review, maybe prepares a new
series.
- 24 hours pass
- rinse, repeat
- it gets merged, hopefully with some Reviewed-by"s.

Not unreasonable, but it requires that submitter be made aware of
Sashiko's comments. At present that's via me being tiresome.

Anyway, early days. I'm thinking that an emailed reply-to-all from
Sashiko will help. Much hinges on how useful submitters find these
questions to be - something which I'm paying close attention to...