linux-kernel - Re: [PATCH v2] mm, page_alloc: Fix has_unmovable

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Message-ID: <20181220130857.yrzv5wzmiw7jbycb@master>
Date:   Thu, 20 Dec 2018 13:08:57 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Wei Yang <richard.weiyang@...il.com>,
        akpm@...ux-foundation.org, vbabka@...e.cz,
        pavel.tatashin@...rosoft.com, rppt@...ux.vnet.ibm.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm, page_alloc: Fix has_unmovable_pages for HugePages

On Thu, Dec 20, 2018 at 01:49:28PM +0100, Oscar Salvador wrote:
>On Thu, Dec 20, 2018 at 10:12:28AM +0100, Michal Hocko wrote:
>> > <--
>> > skip_pages = (1 << compound_order(head)) - (page - head);
>> > iter = skip_pages - 1;
>> > --
>> > 
>> > which looks more simple IMHO.
>> 
>> Agreed!
>
>Andrew, can you please apply the next diff chunk on top of the patch:
>
>diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>index 4812287e56a0..978576d93783 100644
>--- a/mm/page_alloc.c
>+++ b/mm/page_alloc.c
>@@ -8094,7 +8094,7 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
> 				goto unmovable;
> 
> 			skip_pages = (1 << compound_order(head)) - (page - head);
>-			iter = round_up(iter + 1, skip_pages) - 1;
>+			iter = skip_pages - 1;

This complicated the calculation. 

The original code is correct.

iter = round_up(iter + 1, 1<<compound_order(head)) - 1;

> 			continue;
> 		}
>
>Thanks!
>-- 
>Oscar Salvador
>SUSE L3

-- 
Wei Yang
Help you, Help me