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

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Date:   Tue, 30 Jul 2019 08:12:20 +0200
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     "James E . J . Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        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 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(-)
>

Hi everyone,

This is just a preparatory series for the merging of x86 mmap top-down 
functions with
the generic ones (those should get into v5.3), if you could take some 
time to take a look,
that would be great :)

Thanks,

Alex