linux-kernel - Re:Re: Re: [PATCH v2] mm/page_alloc: fix alloc_pages_bulk/set_page

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Message-ID: <AIMAoQD-DycrCuBi0i90WqoN.3.1626358372826.Hmail.link@vivo.com>
Date:   Thu, 15 Jul 2021 22:12:52 +0800 (GMT+08:00)
From:   杨欢 <link@...o.com>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Lobakin <alobakin@...me>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, kernel@...o.com,
        syzbot+b07d8440edb5f8988eea@...kaller.appspotmail.com,
        Wang Qing <wangqing@...o.com>
Subject: Re:Re: Re: [PATCH v2] mm/page_alloc: fix alloc_pages_bulk/set_page_owner panic on irq disabled


>> >> Fixes: 0f87d9d30f21 ("mm/page_alloc: add an array-based interface to the bulk page allocator")
>> >> Reported-by: syzbot+b07d8440edb5f8988eea@...kaller.appspotmail.com
>> >> Suggested-by: Wang Qing <wangqing@...o.com>
>> >> Signed-off-by: Yang Huan <link@...o.com>
>> >
>> >https://lore.kernel.org/lkml/20210713152100.10381-2-mgorman@techsingularity.net/
>> >is now part of a series that has being sent to Linus. Hence, the Fixes
>> >part is no longer applicable and the patch will no longer be addresing
>> >an atomic sleep bug.  This patch should be treated as an enhancement
>>
>> Hi Mel Gorman, thanks for your reply.
>> I see the fix patch, it fix this bug by abandon alloc bulk feature when page_owner is set. 
>> But in my opinion, it can't really fix this bug, it's a circumvention plan.
>
>Yes, it's a circumvention plan for reasons as laid out in the changelog.
>
>> >to allow bulk allocations when PAGE_OWNER is set. For that, it should
>> >include a note on the performance if PAGE_OWNER is used with either NFS
>> >or high-speed networking to justify the additional complexity.
>>
>> My patch just split the prep_new_page page_gfp into alloc_gfp(for alloc bulk is GFP_ATOMIC,
>> for other's no change) and trace page gfp.  So, we will not use the error way to get memory. 
>> So, I think this will not affect alloc bulk performance when page_owner is on(compare with origin patch) but
>> can really fix this  bug rather than evade.
>> And this patch can let alloc bulk feature and page_owner feature work togher
>> So, I will send patch again based on the fix patch.
>
>Your fix should revert the workaround. Also your changelog should note
>that in some cases that PAGE_OWNER information will be lost if the
>GFP_ATOMIC allocation from bulk allocation context fails.
Thanks, I will note that. 
>
>-- 
>Mel Gorman
>SUSE Labs