linux-kernel - Re: [PATCH RESEND 6/8] parisc: Use mmap_base, not mmap_legacy_base, as low

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Message-ID: <438124ff-6838-7ced-044c-ca57a6b9cc91@gmx.de>
Date:   Tue, 25 Jun 2019 16:09:06 +0200
From:   Helge Deller <deller@....de>
To:     Alexandre Ghiti <alex@...ti.fr>,
        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 6/8] parisc: Use mmap_base, not mmap_legacy_base,
 as low_limit for bottom-up mmap

On 20.06.19 07:03, Alexandre Ghiti wrote:
> Bottom-up mmap scheme is used twice:
>
> - for legacy mode, in which mmap_legacy_base and mmap_base are equal.
>
> - in case of mmap failure in top-down mode, where there is no need to go
> through the whole address space again for the bottom-up fallback: the goal
> of this fallback is to find, as a last resort, space between the top-down
> mmap base and the stack, which is the only place not covered by the
> top-down mmap.
>
> Then this commit removes the usage of mmap_legacy_base field from parisc
> code.
>
> Signed-off-by: Alexandre Ghiti <alex@...ti.fr>

Boot-tested on parisc and seems to work nicely, thus:

Acked-by: Helge Deller <deller@....de>

Helge



> ---
>  arch/parisc/kernel/sys_parisc.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c
> index 5d458a44b09c..e987f3a8eb0b 100644
> --- a/arch/parisc/kernel/sys_parisc.c
> +++ b/arch/parisc/kernel/sys_parisc.c
> @@ -119,7 +119,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
>
>  	info.flags = 0;
>  	info.length = len;
> -	info.low_limit = mm->mmap_legacy_base;
> +	info.low_limit = mm->mmap_base;
>  	info.high_limit = mmap_upper_limit(NULL);
>  	info.align_mask = last_mmap ? (PAGE_MASK & (SHM_COLOUR - 1)) : 0;
>  	info.align_offset = shared_align_offset(last_mmap, pgoff);
> @@ -240,13 +240,11 @@ static unsigned long mmap_legacy_base(void)
>   */
>  void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
>  {
> -	mm->mmap_legacy_base = mmap_legacy_base();
> -	mm->mmap_base = mmap_upper_limit(rlim_stack);
> -
>  	if (mmap_is_legacy()) {
> -		mm->mmap_base = mm->mmap_legacy_base;
> +		mm->mmap_base = mmap_legacy_base();
>  		mm->get_unmapped_area = arch_get_unmapped_area;
>  	} else {
> +		mm->mmap_base = mmap_upper_limit(rlim_stack);
>  		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
>  	}
>  }
>