Re: [PATCH 1/3] Revert"thp: make MADV_HUGEPAGE check for mm->def_flags"

[Andrew Morton]

On Fri, 31 Jan 2014 12:23:43 -0600 Alex Thorlton <athorlton@xxxxxxx> wrote:

> This reverts commit 8e72033f2a489b6c98c4e3c7cc281b1afd6cb85cm, and adds

'm' is not a hex digit ;)

> in code to fix up any issues caused by the revert.
> 
> The revert is necessary because hugepage_madvise would return -EINVAL
> when VM_NOHUGEPAGE is set, which will break subsequent chunks of this
> patch set.

This is a bit skimpy.  Why doesn't the patch re-break kvm-on-s390?

it would be nice to have a lot more detail here, please.  What was the
intent of 8e72033f2a48, how this patch retains 8e72033f2a48's behavior,
etc.

> --- a/arch/s390/mm/pgtable.c
> +++ b/arch/s390/mm/pgtable.c
> @@ -504,6 +504,9 @@ static int gmap_connect_pgtable(unsigned long address, unsigned long segment,
>  	if (!pmd_present(*pmd) &&
>  	    __pte_alloc(mm, vma, pmd, vmaddr))
>  		return -ENOMEM;
> +	/* large pmds cannot yet be handled */
> +	if (pmd_large(*pmd))
> +		return -EFAULT;

This bit wasn't in 8e72033f2a48.


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