linux-kernel - Re: [PATCH] testing/radix-tree/maple: hack around kfree

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Message-ID: <97e3a596-ca5c-41ec-b6b2-8b7afafca88f@lucifer.local>
Date: Fri, 15 Aug 2025 05:28:02 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pedro Falcato <pfalcato@...e.de>, Matthew Wilcox <willy@...radead.org>,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, maple-tree@...ts.infradead.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] testing/radix-tree/maple: hack around kfree_rcu not
 existing

On Thu, Aug 14, 2025 at 10:09:15PM -0400, Liam R. Howlett wrote:
> * Andrew Morton <akpm@...ux-foundation.org> [250814 21:02]:
> > Well, can we have this as a standalone thing, rather than as a
> > modification to a patch whose future is uncertain?
> >
> > Then we can just drop "testing/radix-tree/maple: hack around kfree_rcu
> > not existing", yes?
> >
> > Some expansion of "fixes the build for the VMA userland tests" would be
> > helpful.
>
> Ah, this is somewhat messy.
>
> Pedro removed unnecessary rcu calls with the newer slab reality as you
> can directly call kfree instead of specifying the kmem_cache.
>
> But the patch is partially already in Vlastimil's sheaves work and we'd
> like his work to go through his branch, so the future of this particular
> patch is a bit messy.
>
> Maybe we should just drop the related patches that caused the issue from
> the mm-new branch?  That way we don't need a fix at all.
>
> And when Vlastimil is around, we can get him to pick up the set
> including the fix.
>
> Doing things this way will allow Vlastimil the avoid conflicts on
> rebase, and restore the userspace testing in mm-new.
>
> Does that make sense to everyone?

Sounds good to me, I didn't realise that both the original series at [0])
(which introduced the test fail) and the follow up at [1] were intended to
be dropped, I thought only [1] but dropping [0] obviously also fixes it!

And it looks like Andrew's done so and tests now fully working in mm-new
again so I'm happy :)

Cheers, Lorenzo

[0]:https://lore.kernel.org/all/20250718172138.103116-1-pfalcato@suse.de/
[1]:https://lore.kernel.org/all/20250812162124.59417-1-pfalcato@suse.de/