linux-kernel - Re: [PATCH resend] mm/page_alloc: fix comment is __get_free

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Message-ID: <20180406100236.GK8286@dhcp22.suse.cz>
Date:   Fri, 6 Apr 2018 12:02:36 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     akpm@...ux-foundation.org
Cc:     JianKang Chen <chenjiankang1@...wei.com>,
        mgorman@...hsingularity.net, hannes@...xchg.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        xieyisheng1@...wei.com, guohanjun@...wei.com,
        wangkefeng.wang@...wei.com
Subject: Re: [PATCH resend] mm/page_alloc: fix comment is __get_free_pages

On Wed 29-11-17 17:04:46, Michal Hocko wrote:
[...]
> From 000bb422fe07adbfa8cd8ed953b18f48647a45d6 Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@...e.com>
> Date: Wed, 29 Nov 2017 17:02:33 +0100
> Subject: [PATCH] mm: drop VM_BUG_ON from __get_free_pages
> 
> There is no real reason to blow up just because the caller doesn't know
> that __get_free_pages cannot return highmem pages. Simply fix that up
> silently. Even if we have some confused users such a fixup will not be
> harmful.
> 
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Andrew, have we reached any conclusion for this? Should I repost or drop
it on the floor?

> ---
>  mm/page_alloc.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 0d518e9b2ee8..3dd960ea8c13 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4284,9 +4284,7 @@ unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
>  	 * __get_free_pages() returns a virtual address, which cannot represent
>  	 * a highmem page
>  	 */
> -	VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
> -
> -	page = alloc_pages(gfp_mask, order);
> +	page = alloc_pages(gfp_mask & ~__GFP_HIGHMEM, order);
>  	if (!page)
>  		return 0;
>  	return (unsigned long) page_address(page);
> -- 
> 2.15.0
> 
> -- 
> Michal Hocko
> SUSE Labs

-- 
Michal Hocko
SUSE Labs