linux-kernel - Re: [PATCH 1/7] mm: allocate mm_cpumask dynamically based on nr_cpu

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Date:   Sun, 15 Jul 2018 19:50:18 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, luto@...nel.org,
        dave.hansen@...el.com, kernel-team@...com, efault@....de,
        tglx@...utronix.de, songliubraving@...com, hpa@...or.com
Subject: Re: [PATCH 1/7] mm: allocate mm_cpumask dynamically based on
 nr_cpu_ids

On Mon, 2018-07-16 at 00:59 +0200, Ingo Molnar wrote:
> * Rik van Riel <riel@...riel.com> wrote:
> 
> > The mm_struct always contains a cpumask bitmap, regardless of
> > CONFIG_CPUMASK_OFFSTACK. That means the first step can be to
> > simplify things, and simply have one bitmask at the end of the
> > mm_struct for the mm_cpumask.
> > 
> > This does necessitate moving everything else in mm_struct into
> > an anonymous sub-structure, which can be randomized when struct
> > randomization is enabled.
> > 
> > The second step is to determine the correct size for the
> > mm_struct slab object from the size of the mm_struct
> > (excluding the cpu bitmap) and the size the cpumask.
> > 
> > For init_mm we can simply allocate the maximum size this
> > kernel is compiled for, since we only have one init_mm
> > in the system, anyway.
> > 
> > Pointer magic by Mike Galbraith, to evade -Wstringop-overflow
> > getting confused by the dynamically sized array.
> > 
> > Signed-off-by: Rik van Riel <riel@...riel.com>
> > Signed-off-by: Mike Galbraith <efault@....de>
> 
> Is this an Acked-by in disguise, or did this patch route via Mike?

Mike found an issue with the patch and sent a
fix, so I added his S-o-b to this patch as
well.

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