linux-kernel - Re: [PATCH 3/5] mm: page_vma_mapped: support checking if a pfn is mapped into a vma

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Message-ID: <CAMZfGtWForYqmrZJFfOVw5pQPq8idQxwT9aFcUuCJMjdE6Tf3Q@mail.gmail.com>
Date:   Mon, 24 Jan 2022 17:01:03 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>, apopple@...dia.com,
        Yang Shi <shy828301@...il.com>, rcampbell@...dia.com,
        Hugh Dickins <hughd@...gle.com>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        zwisler@...nel.org, linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        nvdimm@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH 3/5] mm: page_vma_mapped: support checking if a pfn is
 mapped into a vma

On Mon, Jan 24, 2022 at 3:36 PM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Fri, Jan 21, 2022 at 03:55:13PM +0800, Muchun Song wrote:
> > +     if (pvmw->pte && ((pvmw->flags & PVMW_PFN_WALK) || !PageHuge(pvmw->page)))
>
> Please avoid the overly long line here and in a few other places.

OK.

>
> > +/*
> > + * Then at what user virtual address will none of the page be found in vma?
>
> Doesn't parse, what is this trying to say?

Well, I am also confused.

BTW, this is not introduced by me, it is introduced by:

  commit 37ffe9f4d7ff ("mm/thp: fix vma_address() if virtual address
below file offset")

If it is really confusing, I can replace this line with:

"Return the end user virtual address of a page within a vma"

Thanks.