linux-kernel - Re: [PATCH v3 01/14] mm/mempolicy: Add comment for missing LOCAL

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Date:   Wed, 10 Mar 2021 14:27:04 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dave Hansen <dave.hansen@...el.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        Andi leen <ak@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v3 01/14] mm/mempolicy: Add comment for missing LOCAL

On Wed, Mar 03, 2021 at 06:20:45PM +0800, Feng Tang wrote:
> From: Ben Widawsky <ben.widawsky@...el.com>
> 
> MPOL_LOCAL is a bit weird because it is simply a different name for an
> existing behavior (preferred policy with no node mask). It has been this
> way since it was added here:
> commit 479e2802d09f ("mm: mempolicy: Make MPOL_LOCAL a real policy")
> 
> It is so similar to MPOL_PREFERRED in fact that when the policy is
> created in mpol_new, the mode is set as PREFERRED, and an internal state
> representing LOCAL doesn't exist.
> 
> To prevent future explorers from scratching their head as to why
> MPOL_LOCAL isn't defined in the mpol_ops table, add a small comment
> explaining the situations.
> 
> v2:
> Change comment to refer to mpol_new (Michal)
> 
> Link: https://lore.kernel.org/r/20200630212517.308045-2-ben.widawsky@intel.com
> #Acked-by: Michal Hocko <mhocko@...e.com>

This shouldn't be masked:

Acked-by: Michal Hocko <mhocko@...e.com>

I did the mask when sending for internal review, and forgot to restore
it, sorry for the noise.

Thanks,
Feng

> Signed-off-by: Ben Widawsky <ben.widawsky@...el.com>
> Signed-off-by: Feng Tang <feng.tang@...el.com>
> ---
>  mm/mempolicy.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 2c3a865..5730fc1 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -427,6 +427,7 @@ static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
>  		.create = mpol_new_bind,
>  		.rebind = mpol_rebind_nodemask,
>  	},
> +	/* [MPOL_LOCAL] - see mpol_new() */
>  };
>  
>  static int migrate_page_add(struct page *page, struct list_head *pagelist,
> -- 
> 2.7.4