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

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Message-Id: <20250814180217.da2ab57d5b940b52aa45b238@linux-foundation.org>
Date: Thu, 14 Aug 2025 18:02:17 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Pedro Falcato <pfalcato@...e.de>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R . Howlett"
 <Liam.Howlett@...cle.com>, 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, 14 Aug 2025 13:40:03 +0100 Pedro Falcato <pfalcato@...e.de> wrote:

> On Thu, Aug 14, 2025 at 07:49:27AM +0100, Lorenzo Stoakes wrote:
> > From: Pedro Falcato <pfalcato@...e.de>
> > 
> > liburcu doesn't have kfree_rcu (or anything similar). Despite that, we can
> > hack around it in a trivial fashion, by adding a wrapper.
> > 
> > This wrapper only works for maple_nodes, and not anything else (due to us
> > not being able to know rcu_head offsets in any way), and thus we take
> > advantage of the type checking to avoid future silent breakage.
> > 
> > This fixes the build for the VMA userland tests.
> > 
> > Additionally remove the existing implementation in maple.c, and have
> > maple.c include the maple-shared.c header.
> > 
> > Reviewed-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>
> > Tested-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> > Signed-off-by: Pedro Falcato <pfalcato@...e.de>
> > Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> > ---
> > 
> > Andrew - please attribute this as Pedro's patch (Pedro - please mail to
> > confirm), as this is simply an updated version of [0], pulled out to fix the
> > VMA tests which remain broken.
> >
> 
> ACK, this is fine. The future of the series is still unclear, so if this fixes
> the build then all good from my end :)

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.