linux-kernel - Re: [PATCH v5 24/26] mm/pagemap: Recognize uffd-wp bit for shmem/hugetlbfs

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Message-ID: <A83FCF8F-193E-4584-9442-C95B2635FD03@nutanix.com>
Date:   Mon, 19 Jul 2021 09:53:36 +0000
From:   Tiberiu Georgescu <tiberiu.georgescu@...anix.com>
To:     Peter Xu <peterx@...hat.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Jerome Glisse <jglisse@...hat.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Alistair Popple <apopple@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Hugh Dickins <hughd@...gle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>
Subject: Re: [PATCH v5 24/26] mm/pagemap: Recognize uffd-wp bit for
 shmem/hugetlbfs


Hello Peter,

> On 15 Jul 2021, at 21:16, Peter Xu <peterx@...hat.com> wrote:
> 
> This requires the pagemap code to be able to recognize the newly introduced
> swap special pte for uffd-wp, meanwhile the general case for hugetlb that we
> recently start to support.  It should make pagemap uffd-wp support complete.
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
> fs/proc/task_mmu.c | 7 +++++++
> 1 file changed, 7 insertions(+)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 9c5af77b5290..988e29fa1f00 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -1389,6 +1389,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
> 		flags |= PM_SWAP;
> 		if (is_pfn_swap_entry(entry))
> 			page = pfn_swap_entry_to_page(entry);
> +	} else if (pte_swp_uffd_wp_special(pte)) {
> +		flags |= PM_UFFD_WP;
> 	}

^ Would it not be important to also add PM_SWAP to flags?

Kind regards,
Tibi