linux-kernel - Re: [RFC PATCH v2 03/30] mm: thp: use single linked list for THP page table page deposit.

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Date:   Mon, 28 Sep 2020 20:34:28 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Zi Yan <ziy@...dia.com>
Cc:     linux-mm@...ck.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Roman Gushchin <guro@...com>, Rik van Riel <riel@...riel.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Yang Shi <shy828301@...il.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        David Hildenbrand <david@...hat.com>,
        William Kucharski <william.kucharski@...cle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        David Nellans <dnellans@...dia.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 03/30] mm: thp: use single linked list for THP
 page table page deposit.

On Mon, Sep 28, 2020 at 01:54:01PM -0400, Zi Yan wrote:
>  		struct {	/* Page table pages */
> -			unsigned long _pt_pad_1;	/* compound_head */
> -			pgtable_t pmd_huge_pte; /* protected by page->ptl */
> +			struct llist_head deposit_head; /* pgtable deposit list head */
> +			struct llist_node deposit_node; /* pgtable deposit list node */

If you're going to use two pointers anyway, you might as well use a
list_head.  But I don't think you need to; you could either use a union
of these or you could use the page_address() of the page to store as
much information as you like!