On Mon, 2013-11-18 at 14:58 +0530, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>
> change_prot_numa should work even if _PAGE_NUMA != _PAGE_PROTNONE.
> On archs like ppc64 that don't use _PAGE_PROTNONE and also have
> a separate page table outside linux pagetable, we just need to
> make sure that when calling change_prot_numa we flush the
> hardware page table entry so that next page access result in a numa
> fault.
That patch doesn't look right...
You are essentially making change_prot_numa() do whatever it does (which
I don't completely understand) *for all architectures* now, whether they
have CONFIG_ARCH_USES_NUMA_PROT_NONE or not ... So because you want that
behaviour on powerpc book3s64, you change everybody.
Is that correct ?
Also what exactly is that doing, can you explain ? From what I can see,
it calls back into the core of mprotect to change the protection to
vma->vm_page_prot, which I would have expected is already the protection
there, with the added "prot_numa" flag passed down.
Your changeset comment says "On archs like ppc64 [...] we just need to
make sure that when calling change_prot_numa we flush the
hardware page table entry so that next page access result in a numa
fault."
But change_prot_numa() does a lot more than that ... it does
pte_mknuma(), do we need it ? I assume we do or we wouldn't have added
that PTE bit to begin with...
Now it *might* be allright and it might be that no other architecture
cares anyway etc... but I need at least some mm folks to ack on that
patch before I can take it because it *will* change behaviour of other
architectures.
Cheers,
Ben.
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
> include/linux/mm.h | 3 ---
> mm/mempolicy.c | 9 ---------
> 2 files changed, 12 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 0548eb201e05..51794c1a1d7e 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1851,11 +1851,8 @@ static inline pgprot_t vm_get_page_prot(unsigned long vm_flags)
> }
> #endif
>
> -#ifdef CONFIG_ARCH_USES_NUMA_PROT_NONE
> unsigned long change_prot_numa(struct vm_area_struct *vma,
> unsigned long start, unsigned long end);
> -#endif
> -
> struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
> int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
> unsigned long pfn, unsigned long size, pgprot_t);
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index c4403cdf3433..cae10af4fdc4 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -613,7 +613,6 @@ static inline int queue_pages_pgd_range(struct vm_area_struct *vma,
> return 0;
> }
>
> -#ifdef CONFIG_ARCH_USES_NUMA_PROT_NONE
> /*
> * This is used to mark a range of virtual addresses to be inaccessible.
> * These are later cleared by a NUMA hinting fault. Depending on these
> @@ -627,7 +626,6 @@ unsigned long change_prot_numa(struct vm_area_struct *vma,
> unsigned long addr, unsigned long end)
> {
> int nr_updated;
> - BUILD_BUG_ON(_PAGE_NUMA != _PAGE_PROTNONE);
>
> nr_updated = change_protection(vma, addr, end, vma->vm_page_prot, 0, 1);
> if (nr_updated)
> @@ -635,13 +633,6 @@ unsigned long change_prot_numa(struct vm_area_struct *vma,
>
> return nr_updated;
> }
> -#else
> -static unsigned long change_prot_numa(struct vm_area_struct *vma,
> - unsigned long addr, unsigned long end)
> -{
> - return 0;
> -}
> -#endif /* CONFIG_ARCH_USES_NUMA_PROT_NONE */
>
> /*
> * Walk through page tables and collect pages to be migrated.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>