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

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Message-ID: <aHDJtSKEGWJlMnzz@finisterre.sirena.org.uk>
Date: Fri, 11 Jul 2025 09:22:13 +0100
From: Mark Brown <broonie@...nel.org>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
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

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

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