linux-kernel - Re: [PATCH v4 2/4] mm/migrate_device.c: Add missing flush_cache

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Message-ID: <YxJp6GiGjHZ+ehyf@xz-m1.local>
Date:   Fri, 2 Sep 2022 16:39:04 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Alistair Popple <apopple@...dia.com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        Nadav Amit <nadav.amit@...il.com>,
        huang ying <huang.ying.caritas@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "Sierra Guiza, Alejandro (Alex)" <alex.sierra@....com>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Jason Gunthorpe <jgg@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        David Hildenbrand <david@...hat.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Matthew Wilcox <willy@...radead.org>,
        Karol Herbst <kherbst@...hat.com>,
        Lyude Paul <lyude@...hat.com>, Ben Skeggs <bskeggs@...hat.com>,
        Logan Gunthorpe <logang@...tatee.com>, paulus@...abs.org,
        linuxppc-dev@...ts.ozlabs.org, stable@...r.kernel.org
Subject: Re: [PATCH v4 2/4] mm/migrate_device.c: Add missing
 flush_cache_page()

On Fri, Sep 02, 2022 at 10:35:52AM +1000, Alistair Popple wrote:
> Currently we only call flush_cache_page() for the anon_exclusive case,
> however in both cases we clear the pte so should flush the cache.
> 
> Signed-off-by: Alistair Popple <apopple@...dia.com>
> Fixes: 8c3328f1f36a ("mm/migrate: migrate_vma() unmap page from vma while collecting pages")
> Cc: stable@...r.kernel.org

This is the patch to start collide with David's.

David's patch has also unified both paths with ptep_get_and_clear(), but
this patch itself is also correct to me.

It'll probably just become no-diff after rebase, though.. I'm not sure how
the ordering would be at last, but anyway I think this patch stands as its
own too..

Acked-by: Peter Xu <peterx@...hat.com>

Thanks for tolerant with my nitpickings,

> 
> ---
> 
> New for v4
> ---
>  mm/migrate_device.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index 6a5ef9f..4cc849c 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -193,9 +193,9 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
>  			bool anon_exclusive;
>  			pte_t swp_pte;
>  
> +			flush_cache_page(vma, addr, pte_pfn(*ptep));
>  			anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
>  			if (anon_exclusive) {
> -				flush_cache_page(vma, addr, pte_pfn(*ptep));
>  				ptep_clear_flush(vma, addr, ptep);
>  
>  				if (page_try_share_anon_rmap(page)) {
> -- 
> git-series 0.9.1
> 

-- 
Peter Xu