Re: [PATCH -V2 3/5] mm: Move change_prot_numa outside CONFIG_ARCH_USES_NUMA_PROT_NONE
From: Benjamin Herrenschmidt <hidden>
Date: 2013-12-04 03:13:15
Also in:
linux-mm
On Mon, 2013-11-18 at 14:58 +0530, Aneesh Kumar K.V wrote:
From: "Aneesh Kumar K.V" <redacted> 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.
quoted hunk ↗ jump to hunk
Signed-off-by: Aneesh Kumar K.V <redacted> --- 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.