linux-kernel - Re: [PATCH v2 3/6] mm: page_vma_mapped: support checking if a pfn is mapped into a vma

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Date:   Wed, 2 Feb 2022 18:28:26 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     dan.j.williams@...el.com, jack@...e.cz, viro@...iv.linux.org.uk,
        akpm@...ux-foundation.org, apopple@...dia.com, shy828301@...il.com,
        rcampbell@...dia.com, hughd@...gle.com, xiyuyang19@...an.edu.cn,
        kirill.shutemov@...ux.intel.com, zwisler@...nel.org,
        hch@...radead.org, linux-fsdevel@...r.kernel.org,
        nvdimm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, duanxiongchun@...edance.com
Subject: Re: [PATCH v2 3/6] mm: page_vma_mapped: support checking if a pfn is
 mapped into a vma

On Wed, Feb 02, 2022 at 10:33:04PM +0800, Muchun Song wrote:
> page_vma_mapped_walk() is supposed to check if a page is mapped into a vma.
> However, not all page frames (e.g. PFN_DEV) have a associated struct page
> with it. There is going to be some duplicate codes similar with this function
> if someone want to check if a pfn (without a struct page) is mapped into a
> vma. So add support for checking if a pfn is mapped into a vma. In the next
> patch, the dax will use this new feature.

I'm coming to more or less the same solution for fixing the bug in
page_mapped_in_vma().  If you call it with a head page, it will look
for any page in the THP instead of the precise page.  I think we can do
a fairly significant simplification though, so I'm going to go off
and work on that next ...