Subject: Re: [PATCH 2/5] powerpc/64s/hash: Allow MAP_FIXED allocations to cross 128TB boundary

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Mon, 06 Nov 2017 16:14:10 +0530

Nicholas Piggin <[email-masked]> writes:

> While mapping hints with a length that cross 128TB are disallowed,
> MAP_FIXED allocations that cross 128TB are allowed. These are failing
> on hash (on radix they succeed). Add an additional case for fixed
> mappings to expand the addr_limit when crossing 128TB.

Shouldn't that be fixed in radix. But i see x86 also doing this?

	if (flags & MAP_FIXED)
		return addr;

Kiril,

Is that expected?

>
> Cc: "Aneesh Kumar K.V" <[email-masked]>
> Fixes: f4ea6dcb08 ("powerpc/mm: Enable mappings above 128TB")
> Signed-off-by: Nicholas Piggin <[email-masked]>
> ---
>  arch/powerpc/mm/slice.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
> index 567db541c0a1..f980397b449d 100644
> --- a/arch/powerpc/mm/slice.c
> +++ b/arch/powerpc/mm/slice.c
> @@ -419,7 +419,8 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
>  	/*
>  	 * Check if we need to expland slice area.
>  	 */
> -	if (unlikely(addr > mm->context.addr_limit &&
> +	if (unlikely(((addr > mm->context.addr_limit) ||
> +			(fixed && addr + len > mm->context.addr_limit)) &&
>  		     mm->context.addr_limit != TASK_SIZE)) {
>  		mm->context.addr_limit = TASK_SIZE;
>  		on_each_cpu(slice_flush_segments, mm, 1);
> -- 
> 2.15.0

-aneesh