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Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound pages

From "Kirill A. Shutemov" <kirill@shutemov.name>
Newsgroups linux.kernel
Subject Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound pages
Date 2015-09-24 22:30 +0200
Message-ID <qcljs-5he-11@gated-at.bofh.it> (permalink)
References <qbhUB-3qy-7@gated-at.bofh.it> <qcga6-6cP-5@gated-at.bofh.it> <qcga9-6cP-65@gated-at.bofh.it> <qchfQ-7YI-17@gated-at.bofh.it>
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On Thu, Sep 24, 2015 at 11:08:29AM -0500, Christoph Lameter wrote:
> On Thu, 24 Sep 2015, Kirill A. Shutemov wrote:
> 
> > SLUB uses PG_locked as a bit spin locked.  IIUC, tail pages should never
> > appear there.  VM_BUG_ON() is added to make sure that this assumption is
> > correct.
> 
> Correct. However, VM_BUG_ON is superfluous. If there is a tail page there
> then the information in the page will be not as expected (free list
> parameter f.e.) and things will fall apart rapidly with segfaults.

Right. But would it provide any clues on what is going on?

-- 
 Kirill A. Shutemov
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Thread

[PATCH 00/16] Refreshed page-flags patchset "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
  [PATCH 12/16] page-flags: define PG_mlocked behavior on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
  [PATCH 03/16] page-flags: introduce page flags policies wrt compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
    Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2015-09-25 14:30 +0200
      Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-25 21:20 +0200
        Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-28 13:10 +0200
          Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2015-09-28 13:50 +0200
            Re: [PATCH 03/16] page-flags: introduce page flags policies wrt  compound pages "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-28 20:00 +0200
  [PATCH 04/16] page-flags: define PG_locked behavior on compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-09-24 17:00 +0200
    Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound  pages Christoph Lameter <cl@linux.com> - 2015-09-24 18:10 +0200
      Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound  pages "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-24 22:30 +0200
  Re: [PATCH 00/16] Refreshed page-flags patchset Christoph Lameter <cl@linux.com> - 2015-09-24 18:20 +0200
    Re: [PATCH 00/16] Refreshed page-flags patchset "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-24 22:30 +0200

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