linux-kernel - Re: [PATCH] mm,hwpoison: unmap poisoned page before invalidation

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Date:   Tue, 29 Mar 2022 11:49:53 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-team@...com, Miaohe Lin <linmiaohe@...wei.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] mm,hwpoison: unmap poisoned page before invalidation

On Mon, 2022-03-28 at 11:00 +0200, Oscar Salvador wrote:
> On Fri, Mar 25, 2022 at 04:14:28PM -0400, Rik van Riel wrote:
> > +                       if (invalidate_inode_page(page))
> > +                               poisonret = VM_FAULT_NOPAGE;
> 
> What is the effect of returning VM_FAULT_NOPAGE?
> I take that we are cool because the pte has been installed and points
> to
> a new page? (I could not find where that is being done).
> 
It results in us returning to userspace as if the page
fault had been handled, resulting in a second fault on
the same address.

However, now the page is no longer in the page cache,
and we can read it in from disk, to a page that is not
hardware poisoned, and we can then use that second page
without issues.

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