linux-kernel - Re: [PATCH RESEND v6 3/9] mm: factor helpers for memory_failure_dev

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Date:   Fri, 20 Aug 2021 09:54:06 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Jane Chu <jane.chu@...cle.com>
Cc:     Shiyang Ruan <ruansy.fnst@...itsu.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        Linux NVDIMM <nvdimm@...ts.linux.dev>,
        Linux MM <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        device-mapper development <dm-devel@...hat.com>,
        "Darrick J. Wong" <djwong@...nel.org>, david <david@...morbit.com>,
        Christoph Hellwig <hch@....de>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: Re: [PATCH RESEND v6 3/9] mm: factor helpers for memory_failure_dev_pagemap

On Thu, Aug 5, 2021 at 6:01 PM Jane Chu <jane.chu@...cle.com> wrote:
>
>
> On 7/30/2021 3:01 AM, Shiyang Ruan wrote:
> > -     /*
> > -      * Prevent the inode from being freed while we are interrogating
> > -      * the address_space, typically this would be handled by
> > -      * lock_page(), but dax pages do not use the page lock. This
> > -      * also prevents changes to the mapping of this pfn until
> > -      * poison signaling is complete.
> > -      */
> > -     cookie = dax_lock_page(page);
> > -     if (!cookie)
> > -             goto out;
> > -
> >       if (hwpoison_filter(page)) {
> >               rc = 0;
> > -             goto unlock;
> > +             goto out;
> >       }
>
> why isn't dax_lock_page() needed for hwpoison_filter() check?

Good catch. hwpoison_filter() is indeed consulting page->mapping->host
which needs to be synchronized against inode lifetime.