linux-kernel - PG_reserved and compound pages

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Message-ID: <4482994.u2S3pScRyb@noys2>
Date:	Wed, 06 Apr 2016 13:28:37 +0200
From:	Frank Mehnert <frank.mehnert@...cle.com>
To:	linux-kernel@...r.kernel.org
Subject: PG_reserved and compound pages

Hi,

Linux 4.5 introduced additional checks to ensure that compound pages are
never marked as reserved. In our code we use PG_reserved to ensure that
the kernel does never swap out such pages, e.g.

  int i;
  struct page *pages = alloc_pages(GFP_HIGHUSER | __GFP_COMP, 4);
  for (i = 0; i < 16; i++)
    SetPageReserved(&pages[i]);

The purpose of setting PG_reserved is to prevent the kernel from swapping
this memory out. This worked with older kernel but not with Linux 4.5 as
setting PG_reserved to compound pages is not allowed any more.

Can somebody explain how we can achieve the same result in accordance to
the new Linux 4.5 rules?

Thanks,

Frank
-- 
Dr.-Ing. Frank Mehnert | Software Development Director, VirtualBox
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