linux-kernel - Re: [PATCH] mm/thp: fix call to mmu_notifier in set_pmd_migration

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Message-ID: <DB07F115-B404-4AB0-9D54-BC20C3A3F2B0@cs.rutgers.edu>
Date:   Fri, 12 Oct 2018 12:20:54 -0400
From:   "Zi Yan" <zi.yan@...rutgers.edu>
To:     jglisse@...hat.com
Cc:     linux-mm@...ck.org, "Andrew Morton" <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Anshuman Khandual" <khandual@...ux.vnet.ibm.com>,
        "Dave Hansen" <dave.hansen@...el.com>,
        "David Nellans" <dnellans@...dia.com>,
        "Ingo Molnar" <mingo@...e.hu>,
        "Mel Gorman" <mgorman@...hsingularity.net>,
        "Minchan Kim" <minchan@...nel.org>,
        "Naoya Horiguchi" <n-horiguchi@...jp.nec.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Vlastimil Babka" <vbabka@...e.cz>,
        "Michal Hocko" <mhocko@...nel.org>,
        "Andrea Arcangeli" <aarcange@...hat.com>
Subject: Re: [PATCH] mm/thp: fix call to mmu_notifier in
 set_pmd_migration_entry()

On 12 Oct 2018, at 12:09, jglisse@...hat.com wrote:

> From: Jérôme Glisse <jglisse@...hat.com>
>
> Inside set_pmd_migration_entry() we are holding page table locks and
> thus we can not sleep so we can not call invalidate_range_start/end()
>
> So remove call to mmu_notifier_invalidate_range_start/end() and add
> call to mmu_notifier_invalidate_range(). Note that we are already
> calling mmu_notifier_invalidate_range_start/end() inside the function
> calling set_pmd_migration_entry() (see try_to_unmap_one()).
>
> Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> Reported-by: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Zi Yan <zi.yan@...rutgers.edu>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: David Nellans <dnellans@...dia.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> ---
>  mm/huge_memory.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 533f9b00147d..93cb80fe12cb 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2885,9 +2885,6 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
>  	if (!(pvmw->pmd && !pvmw->pte))
>  		return;
>
> -	mmu_notifier_invalidate_range_start(mm, address,
> -			address + HPAGE_PMD_SIZE);
> -
>  	flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
>  	pmdval = *pvmw->pmd;
>  	pmdp_invalidate(vma, address, pvmw->pmd);
> @@ -2898,11 +2895,9 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
>  	if (pmd_soft_dirty(pmdval))
>  		pmdswp = pmd_swp_mksoft_dirty(pmdswp);
>  	set_pmd_at(mm, address, pvmw->pmd, pmdswp);
> +	mmu_notifier_invalidate_range(mm, address, address + HPAGE_PMD_SIZE);
>  	page_remove_rmap(page, true);
>  	put_page(page);
> -
> -	mmu_notifier_invalidate_range_end(mm, address,
> -			address + HPAGE_PMD_SIZE);
>  }
>
>  void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
> -- 
> 2.17.2

Yes, these are the redundant calls to mmu_notifier_invalidate_range_start/end()
in set_pmd_migration_entry(). Thanks for the patch.

Fixes: 616b8371539a6 (mm: thp: enable thp migration in generic path)

Reviewed-by: Zi Yan <zi.yan@...rutgers.edu>



—
Best Regards,
Yan Zi

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