linux-kernel - Re: [PATCH v3] mm: thp: fix flags for pmd migration when split

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Message-Id: <6B1C6409-E855-47E4-9D33-3D7C634A47F6@oracle.com>
Date:   Thu, 13 Dec 2018 01:24:27 -0700
From:   William Kucharski <william.kucharski@...cle.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Zi Yan <zi.yan@...rutgers.edu>, linux-mm@...ck.org
Subject: Re: [PATCH v3] mm: thp: fix flags for pmd migration when split



> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index f2d19e4fe854..aebade83cec9 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2145,23 +2145,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
> 	 */
> 	old_pmd = pmdp_invalidate(vma, haddr, pmd);
> 
> -#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
> 	pmd_migration = is_pmd_migration_entry(old_pmd);
> -	if (pmd_migration) {
> +	if (unlikely(pmd_migration)) {
> 		swp_entry_t entry;
> 
> 		entry = pmd_to_swp_entry(old_pmd);
> 		page = pfn_to_page(swp_offset(entry));
> -	} else
> -#endif
> +		write = is_write_migration_entry(entry);
> +		young = false;
> +		soft_dirty = pmd_swp_soft_dirty(old_pmd);
> +	} else {
> 		page = pmd_page(old_pmd);
> +		if (pmd_dirty(old_pmd))
> +			SetPageDirty(page);
> +		write = pmd_write(old_pmd);
> +		young = pmd_young(old_pmd);
> +		soft_dirty = pmd_soft_dirty(old_pmd);
> +	}
> 	VM_BUG_ON_PAGE(!page_count(page), page);
> 	page_ref_add(page, HPAGE_PMD_NR - 1);
> -	if (pmd_dirty(old_pmd))
> -		SetPageDirty(page);
> -	write = pmd_write(old_pmd);
> -	young = pmd_young(old_pmd);
> -	soft_dirty = pmd_soft_dirty(old_pmd);
> 
> 	/*
> 	 * Withdraw the table only after we mark the pmd entry invalid.
> -- 

Looks good.

Reviewed-by: William Kucharski <william.kucharski@...cle.com>