On Mon, 2017-04-10 at 18:04 +0200, Greg KH wrote:
> On Mon, Apr 10, 2017 at 04:48:17PM +0100, Ben Hutchings wrote:
> > > > On Mon, 2017-04-10 at 17:09 +0200, gregkh@linuxfoundation.org wrote:
> > > This is a note to let you know that I've just added the patch titled
> > > 
> > >     mm/huge_memory.c: respect FOLL_FORCE/FOLL_COW for thp
> > > 
> > > to the 4.4-stable tree which can be found at:
> > >     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> > > 
> > > The filename of the patch is:
> > >      mm-huge_memory.c-respect-foll_force-foll_cow-for-thp.patch
> > > and it can be found in the queue-4.4 subdirectory.
> > > 
> > > If you, or anyone else, feels it should not be added to the stable tree,
> > > please let <stable@vger.kernel.org> know about it.
> > > 
> > > 
> > > From 303681d5d538d81b5e23754515202b5b9febd2e9 Mon Sep 17 00:00:00 2001
> > > From: Keno Fischer <keno@juliacomputing.com>
> > > Date: Tue, 24 Jan 2017 15:17:48 -0800
> > > Subject: mm/huge_memory.c: respect FOLL_FORCE/FOLL_COW for thp
> > > 
> > > From: Keno Fischer <keno@juliacomputing.com>
> > > 
> > > commit 8310d48b125d19fcd9521d83b8293e63eb1646aa upstream.
> > 
> > [...]
> > >  - Drop change to follow_devmap_pmd()
> > >  - pmd_dirty() is not available; check the page flags as in older
> > >    backports of can_follow_write_pte()
> > >  - Adjust context]
> > 
> > [...]
> > 
> > Aside from the fact that I got this backport wrong, I don't think you
> > need the main change here.  In 4.4, all arches that define
> > CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE also define pmd_dirty().
> 
> Hm, ok, but Keno said people are still hitting this issue on 4.4-stable.
> 
> So, what should I do?  I'll go drop this from my queue for now, but as I
> don't know what to do to test this, I'm at a loss...

I don't mean the fix isn't needed; I mean that I don't think you should
use this backport.  You should only need to drop the change to
follow_devmap_pmd().

Ben.

-- 
Ben Hutchings
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