linux-kernel - Re: [PATCHv3 0/5] Fix compound

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Message-Id: <20150820163836.b3b69f2bf36dba7020bdc893@linux-foundation.org>
Date:	Thu, 20 Aug 2015 16:38:36 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv3 0/5] Fix compound_head() race

On Thu, 20 Aug 2015 15:31:07 +0300 "Kirill A. Shutemov" <kirill@...temov.name> wrote:

> On Wed, Aug 19, 2015 at 12:21:41PM +0300, Kirill A. Shutemov wrote:
> > Here's my attempt on fixing recently discovered race in compound_head().
> > It should make compound_head() reliable in all contexts.
> > 
> > The patchset is against Linus' tree. Let me know if it need to be rebased
> > onto different baseline.
> > 
> > It's expected to have conflicts with my page-flags patchset and probably
> > should be applied before it.
> > 
> > v3:
> >    - Fix build without hugetlb;
> >    - Drop page->first_page;
> >    - Update comment for free_compound_page();
> >    - Use 'unsigned int' for page order;
> > 
> > v2: Per Hugh's suggestion page->compound_head is moved into third double
> >     word. This way we can avoid memory overhead which v1 had in some
> >     cases.
> > 
> >     This place in struct page is rather overloaded. More testing is
> >     required to make sure we don't collide with anyone.
> 
> Andrew, can we have the patchset applied, if nobody has objections?

I've been hoping to hear from Hugh and I wasn't planning on processing
these before the 4.2 release.


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