linux-kernel - Re: [PATCH 2/3] mm/hugetlb: take refcount under page table lock in follow_huge

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Message-ID: <20140729011018.GA25865@nhori.redhat.com>
Date:	Mon, 28 Jul 2014 21:10:18 -0400
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH 2/3] mm/hugetlb: take refcount under page table lock in
 follow_huge_pmd()

On Mon, Jul 28, 2014 at 04:02:31PM -0700, David Rientjes wrote:
> On Mon, 28 Jul 2014, Naoya Horiguchi wrote:
> 
> > We have a race condition between move_pages() and freeing hugepages,
> > where move_pages() calls follow_page(FOLL_GET) for hugepages internally
> > and tries to get its refcount without preventing concurrent freeing.
> > This race crashes the kernel, so this patch fixes it by moving FOLL_GET
> > code for hugepages into follow_huge_pmd() with taking the page table lock.
> > 
> 
> What about CONFIG_ARCH_WANT_GENERAL_HUGETLB=n configs?

Ah yes, I need cover them.
So I'll add some wrapper to do this locking in common hugetlb code.

Thanks,
Naoya Horiguchi
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