linux-kernel - Re: [PATCH] mm/init-mm.c: use CPU_BITS_NONE to initialize .cpu

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Message-Id: <20190822132602.GF18872@rapoport-lnx>
Date:   Thu, 22 Aug 2019 16:26:03 +0300
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/init-mm.c: use CPU_BITS_NONE to initialize .cpu_bitmap

Hi,

On Thu, Aug 22, 2019 at 09:52:07AM +0200, Rasmus Villemoes wrote:
> init_mm is sizeof(long) larger than it needs to be. Use the
> CPU_BITS_NONE macro meant for this, which will initialize just the
> indices 0...(BITS_TO_LONGS(NR_CPUS)-1) and hence make the array size
> actually BITS_TO_LONGS(NR_CPUS).

I've sent a similar patch [1] a week or so ago, it's in -mm tree.

[1] https://lore.kernel.org/linux-mm/1565703815-8584-1-git-send-email-rppt@linux.ibm.com/
 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
>  mm/init-mm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/init-mm.c b/mm/init-mm.c
> index a787a319211e..fb1e15028ef0 100644
> --- a/mm/init-mm.c
> +++ b/mm/init-mm.c
> @@ -35,6 +35,6 @@ struct mm_struct init_mm = {
>  	.arg_lock	=  __SPIN_LOCK_UNLOCKED(init_mm.arg_lock),
>  	.mmlist		= LIST_HEAD_INIT(init_mm.mmlist),
>  	.user_ns	= &init_user_ns,
> -	.cpu_bitmap	= { [BITS_TO_LONGS(NR_CPUS)] = 0},
> +	.cpu_bitmap	= CPU_BITS_NONE,
>  	INIT_MM_CONTEXT(init_mm)
>  };
> -- 
> 2.20.1
> 
> 

-- 
Sincerely yours,
Mike.