linux-kernel - Re: [PATCH v2 01/11] hugetlb: set hugetlb page flag before optimizing vmemmap

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Message-ID: <ZPfMds3PloTLeZPP@casper.infradead.org>
Date:   Wed, 6 Sep 2023 01:48:54 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Rientjes <rientjes@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Michal Hocko <mhocko@...e.com>,
        Xiongchun Duan <duanxiongchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 01/11] hugetlb: set hugetlb page flag before
 optimizing vmemmap

On Tue, Sep 05, 2023 at 02:44:00PM -0700, Mike Kravetz wrote:
> @@ -456,6 +457,7 @@ int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
>  	unsigned long vmemmap_start = (unsigned long)head, vmemmap_end;
>  	unsigned long vmemmap_reuse;
>  
> +	VM_WARN_ON_ONCE(!PageHuge(head));
>  	if (!HPageVmemmapOptimized(head))
>  		return 0;
>  
> @@ -550,6 +552,7 @@ void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
>  	unsigned long vmemmap_start = (unsigned long)head, vmemmap_end;
>  	unsigned long vmemmap_reuse;
>  
> +	VM_WARN_ON_ONCE(!PageHuge(head));
>  	if (!vmemmap_should_optimize(h, head))
>  		return;

Someone who's looking for an easy patch or three should convert both
of these functions to take a folio instead of a page.  All callers
pass &folio->page.  Obviously do that work on top of Mike's patch set
to avoid creating more work for him.