Re: [PATCH RESEND 6/8] parisc: Use mmap_base, not mmap_legacy_base, as low_limit for bottom-up mmap

[Helge Deller]

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@xxxxxxxx>

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

Acked-by: Helge Deller <deller@xxxxxx>

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;
>  	}
>  }
>