linux-kernel - Re: [PATCH 09/10] mm/mremap: permit mremap() move of multiple VMAs

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Message-ID: <50906a91-5417-4d44-85ea-d114c4cec3a5@lucifer.local>
Date: Fri, 11 Jul 2025 09:31:34 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Mark Brown <broonie@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Peter Xu <peterx@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Pedro Falcato <pfalcato@...e.de>, Rik van Riel <riel@...riel.com>,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 09/10] mm/mremap: permit mremap() move of multiple VMAs

Thanks, yeah, I'm going to send a respin today. I accidentally enabled for the
MREMAP_DONTUNMAP case, so this should resolve it among other things.

Note there's a v2 at
https://lore.kernel.org/linux-mm/cover.1752162066.git.lorenzo.stoakes@oracle.com/

On Fri, Jul 11, 2025 at 09:22:13AM +0100, Mark Brown wrote:
> On Fri, Jul 11, 2025 at 09:17:27AM +0100, Mark Brown wrote:
> > On Mon, Jul 07, 2025 at 06:27:52AM +0100, Lorenzo Stoakes wrote:
> > > Historically we've made it a uAPI requirement that mremap() may only
> > > operate on a single VMA at a time.
> > >
> > > For instances where VMAs need to be resized, this makes sense, as it
> > > becomes very difficult to determine what a user actually wants should they
> > > indicate a desire to expand or shrink the size of multiple VMAs (truncate?
> > > Adjust sizes individually? Some other strategy?).
> >
> > I'm seeing failures in the mremap_dontunmap test in -next on Rasperry Pi
> > 4 which bisect down to this patch.  The test logging isn't super helpful
> > here sadly:
>
> Same thing on Orion O6 (a more modern ARM v9 system with more RAM than
> my Pi):
>
>     https://lava.sirena.org.uk/scheduler/job/1556807
>
> and Avenger 96 (which is 32 bit arm):
>
>     https://lava.sirena.org.uk/scheduler/job/1556479