From: Andrea Arcangeli <aarcange@redhat.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Alex Williamson <alex.williamson@redhat.com>,
kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [BUG] vfio device assignment regression with THP ref counting redesign
Date: Thu, 5 May 2016 17:24:06 +0200 [thread overview]
Message-ID: <20160505152406.GH28755@redhat.com> (raw)
In-Reply-To: <20160505151110.GA13972@node.shutemov.name>
On Thu, May 05, 2016 at 06:11:10PM +0300, Kirill A. Shutemov wrote:
> Hm. How total_mapcount equal to NULL wouldn't lead to NULL-pointer
> dereference inside page_trans_huge_mapcount()?
Sorry for the confusion, this was still work in progress and then I've
seen the email from Alex and I sent the last version I had committed
right away. An earlier version of course had the proper checks for
NULL but they got wiped as I transitioned from one model to another
and back.
> > + page_move_anon_rmap(old_page, vma, address);
>
> compound_head() is missing, I believe.
Oh yes, fixed that too.
if (total_mapcount == 1) {
/*
* The page is all ours. Move it to
* our anon_vma so the rmap code will
* not search our parent or siblings.
* Protected against the rmap code by
* the page lock.
*/
page_move_anon_rmap(compound_head(old_page),
vma, address);
}
If there's no other issue I can git send-email.
Then we should look into calling page_move_anon_rmap from THP COWs
too, hugetlbfs calls it too. I think we probably need to make
page_move_anon_rmap smarter and optionally let it take the lock for us
after reading page->mapping first to be sure it's really moving it.
The question is then if trylock or lock_page should be used, my
preference would be just trylock.
next prev parent reply other threads:[~2016-05-05 15:24 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-28 16:20 [BUG] vfio device assignment regression with THP ref counting redesign Alex Williamson
2016-04-28 18:17 ` Kirill A. Shutemov
2016-04-28 18:58 ` Alex Williamson
2016-04-28 23:21 ` Andrea Arcangeli
2016-04-29 0:44 ` Alex Williamson
2016-04-29 0:51 ` Kirill A. Shutemov
2016-04-29 2:45 ` Alex Williamson
2016-04-29 7:06 ` Kirill A. Shutemov
2016-04-29 15:12 ` Alex Williamson
2016-04-29 16:34 ` Andrea Arcangeli
2016-04-29 22:34 ` Alex Williamson
2016-05-02 10:41 ` Kirill A. Shutemov
2016-05-02 11:15 ` Jerome Glisse
2016-05-02 12:14 ` GUP guarantees wrt to userspace mappings redesign Kirill A. Shutemov
2016-05-02 13:39 ` Jerome Glisse
2016-05-02 15:00 ` GUP guarantees wrt to userspace mappings Kirill A. Shutemov
2016-05-02 15:22 ` Jerome Glisse
2016-05-02 16:12 ` Kirill A. Shutemov
2016-05-02 19:14 ` Andrea Arcangeli
2016-05-02 19:11 ` Andrea Arcangeli
2016-05-02 19:02 ` Andrea Arcangeli
2016-05-02 14:15 ` GUP guarantees wrt to userspace mappings redesign Oleg Nesterov
2016-05-02 16:21 ` Kirill A. Shutemov
2016-05-02 16:22 ` Oleg Nesterov
2016-05-02 18:03 ` Kirill A. Shutemov
2016-05-02 17:41 ` Oleg Nesterov
2016-05-02 18:56 ` Andrea Arcangeli
2016-05-02 15:23 ` [BUG] vfio device assignment regression with THP ref counting redesign Andrea Arcangeli
2016-05-02 16:00 ` Kirill A. Shutemov
2016-05-02 18:03 ` Andrea Arcangeli
2016-05-05 1:19 ` Alex Williamson
2016-05-05 14:39 ` Andrea Arcangeli
2016-05-05 15:09 ` Andrea Arcangeli
2016-05-05 15:11 ` Kirill A. Shutemov
2016-05-05 15:24 ` Andrea Arcangeli [this message]
2016-05-06 7:29 ` Kirill A. Shutemov
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