linux-kernel - Re: [PATCH 3/3] mm: don't remap clean subpages when splitting isolated thp

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Message-ID: <20210804142729.iqtslnn3utvqgec3@box.shutemov.name>
Date:   Wed, 4 Aug 2021 17:27:29 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Yu Zhao <yuzhao@...gle.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Yang Shi <shy828301@...il.com>, Zi Yan <ziy@...dia.com>,
        linux-kernel@...r.kernel.org, Shuang Zhai <zhais@...gle.com>
Subject: Re: [PATCH 3/3] mm: don't remap clean subpages when splitting
 isolated thp

On Sat, Jul 31, 2021 at 12:39:38AM -0600, Yu Zhao wrote:
> @@ -267,13 +308,19 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
>   * Get rid of all migration entries and replace them by
>   * references to the indicated page.
>   */
> -void remove_migration_ptes(struct page *old, struct page *new, bool locked)
> +void remove_migration_ptes(struct page *old, struct page *new, bool locked, bool unmap_clean)
>  {
> +	struct rmap_walk_arg rmap_walk_arg = {
> +		.page = old,
> +		.unmap_clean = unmap_clean,
> +	};
>  	struct rmap_walk_control rwc = {
>  		.rmap_one = remove_migration_pte,
> -		.arg = old,
> +		.arg = &rmap_walk_arg,
>  	};

'old' pointer has few low always-zero bit :P

-- 
 Kirill A. Shutemov