linux-kernel - Re: [PATCHv9 13/36] mm: drop tail page refcounting

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 31 Jul 2015 16:51:45 +0200
From:	Jerome Marchand <jmarchan@...hat.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>
CC:	Dave Hansen <dave.hansen@...el.com>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...two.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Steve Capper <steve.capper@...aro.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Sasha Levin <sasha.levin@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv9 13/36] mm: drop tail page refcounting

On 07/20/2015 04:20 PM, Kirill A. Shutemov wrote:
> Tail page refcounting is utterly complicated and painful to support.
> 
> It uses ->_mapcount on tail pages to store how many times this page is
> pinned. get_page() bumps ->_mapcount on tail page in addition to
> ->_count on head. This information is required by split_huge_page() to
> be able to distribute pins from head of compound page to tails during
> the split.
> 
> We will need ->_mapcount to account PTE mappings of subpages of the
> compound page. We eliminate need in current meaning of ->_mapcount in
> tail pages by forbidding split entirely if the page is pinned.
> 
> The only user of tail page refcounting is THP which is marked BROKEN for
> now.
> 
> Let's drop all this mess. It makes get_page() and put_page() much
> simpler.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Tested-by: Sasha Levin <sasha.levin@...cle.com>
> Tested-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Acked-by: Jerome Marchand <jmarchan@...hat.com>

> ---
>  arch/mips/mm/gup.c            |   4 -
>  arch/powerpc/mm/hugetlbpage.c |  13 +-
>  arch/s390/mm/gup.c            |  13 +-
>  arch/sparc/mm/gup.c           |  14 +--
>  arch/x86/mm/gup.c             |   4 -
>  include/linux/mm.h            |  47 ++------
>  include/linux/mm_types.h      |  17 +--
>  mm/gup.c                      |  34 +-----
>  mm/huge_memory.c              |  41 +------
>  mm/hugetlb.c                  |   2 +-
>  mm/internal.h                 |  44 -------
>  mm/swap.c                     | 273 +++---------------------------------------
>  12 files changed, 40 insertions(+), 466 deletions(-)
> 



Download attachment "signature.asc" of type "application/pgp-signature" (474 bytes)