linux-kernel - [PATCH RFC 0/7] mm: PG_reserved cleanups and documentation

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Date:   Wed,  5 Dec 2018 13:28:44 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-m68k@...ts.linux-m68k.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        David Hildenbrand <david@...hat.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anthony Yznaga <anthony.yznaga@...cle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        David Airlie <airlied@...ux.ie>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        James Morse <james.morse@....com>,
        Kees Cook <keescook@...omium.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Mark Rutland <mark.rutland@....com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Matthew Wilcox <willy@...radead.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Hocko <mhocko@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Miles Chen <miles.chen@...iatek.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Mackerras <paulus@...ba.org>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Tobias Klauser <tklauser@...tanz.ch>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Will Deacon <will.deacon@....com>
Subject: [PATCH RFC 0/7] mm: PG_reserved cleanups and documentation

I was recently going over all users of PG_reserved. Short story: it is
difficult and sometimes not really clear if setting/checking for
PG_reserved is only a relict from the past. Easy to break things.

I had way more cleanups in this series inititally,
but some architectures take PG_reserved as a way to apply a different
caching strategy (for MMIO pages). So I decided to only include the most
obvious changes (that are less likely to break something).

So let's see if the documentation update for PG_reserved I crafted
actually covers most cases or if there is plenty more.

Most notably, for device memory we can hopefully soon stop setting
it PG_reserved

I only briefly tested this on s390x.

David Hildenbrand (7):
  agp: efficeon: no need to set PG_reserved on GATT tables
  s390/vdso: don't clear PG_reserved
  powerpc/vdso: don't clear PG_reserved
  riscv/vdso: don't clear PG_reserved
  m68k/mm: use __ClearPageReserved()
  arm64: kexec: no need to ClearPageReserved()
  mm: better document PG_reserved

 arch/arm64/kernel/machine_kexec.c |  1 -
 arch/m68k/mm/memory.c             |  2 +-
 arch/powerpc/kernel/vdso.c        |  2 --
 arch/riscv/kernel/vdso.c          |  1 -
 arch/s390/kernel/vdso.c           |  2 --
 drivers/char/agp/efficeon-agp.c   |  2 --
 include/linux/page-flags.h        | 18 ++++++++++++++++--
 7 files changed, 17 insertions(+), 11 deletions(-)

-- 
2.17.2