linux-kernel - Re: [PATCH RESEND 0/8] Fix mmap base in bottom-up mmap

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Date:   Wed, 28 Aug 2019 00:53:12 -0400
From:   Alex Ghiti <alex@...ti.fr>
To:     Helge Deller <deller@....de>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     "James E . J . Bottomley" <James.Bottomley@...senPartnership.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S . Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH RESEND 0/8] Fix mmap base in bottom-up mmap

On 8/26/19 6:37 PM, Helge Deller wrote:
> On 26.08.19 09:34, Alexandre Ghiti wrote:
>> On 6/20/19 7:03 AM, Alexandre Ghiti wrote:
>>> This series fixes the fallback of the top-down mmap: in case of
>>> failure, a bottom-up scheme can be tried as a last resort between
>>> the top-down mmap base and the stack, hoping for a large unused stack
>>> limit.
>>>
>>> Lots of architectures and even mm code start this fallback
>>> at TASK_UNMAPPED_BASE, which is useless since the top-down scheme
>>> already failed on the whole address space: instead, simply use
>>> mmap_base.
>>>
>>> Along the way, it allows to get rid of of mmap_legacy_base and
>>> mmap_compat_legacy_base from mm_struct.
>>>
>>> Note that arm and mips already implement this behaviour.
>>>
>>> Alexandre Ghiti (8):
>>>    s390: Start fallback of top-down mmap at mm->mmap_base
>>>    sh: Start fallback of top-down mmap at mm->mmap_base
>>>    sparc: Start fallback of top-down mmap at mm->mmap_base
>>>    x86, hugetlbpage: Start fallback of top-down mmap at mm->mmap_base
>>>    mm: Start fallback top-down mmap at mm->mmap_base
>>>    parisc: Use mmap_base, not mmap_legacy_base, as low_limit for
>>>      bottom-up mmap
>>>    x86: Use mmap_*base, not mmap_*legacy_base, as low_limit for 
>>> bottom-up
>>>      mmap
>>>    mm: Remove mmap_legacy_base and mmap_compat_legacy_code fields from
>>>      mm_struct
>>>
>>>   arch/parisc/kernel/sys_parisc.c  |  8 +++-----
>>>   arch/s390/mm/mmap.c              |  2 +-
>>>   arch/sh/mm/mmap.c                |  2 +-
>>>   arch/sparc/kernel/sys_sparc_64.c |  2 +-
>>>   arch/sparc/mm/hugetlbpage.c      |  2 +-
>>>   arch/x86/include/asm/elf.h       |  2 +-
>>>   arch/x86/kernel/sys_x86_64.c     |  4 ++--
>>>   arch/x86/mm/hugetlbpage.c        |  7 ++++---
>>>   arch/x86/mm/mmap.c               | 20 +++++++++-----------
>>>   include/linux/mm_types.h         |  2 --
>>>   mm/debug.c                       |  4 ++--
>>>   mm/mmap.c                        |  2 +-
>>>   12 files changed, 26 insertions(+), 31 deletions(-)
>>>
>>
>> Any thoughts about that series ? As said before, this is just a 
>> preparatory patchset in order to
>> merge x86 mmap top down code with the generic version.
>
> I just tested your patch series successfully on the parisc
> architeture. You may add:
>
> Tested-by: Helge Deller <deller@....de> # parisc

Thanks again Helge !

Alex


>
> Thanks!
> Helge