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authorMel Gorman <mgorman@suse.de>2014-06-04 16:06:30 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-04 16:53:55 -0700
commitc46a7c817e662a820373bb76b88d0ad67d6abe5d (patch)
tree41a7d24c818c9cfe71f335f7fdae162896aa3b23 /mm/memory.c
parent4468dd76f51f8be75d4f04f1d721e379596e7262 (diff)
x86: define _PAGE_NUMA by reusing software bits on the PMD and PTE levels
_PAGE_NUMA is currently an alias of _PROT_PROTNONE to trap NUMA hinting faults on x86. Care is taken such that _PAGE_NUMA is used only in situations where the VMA flags distinguish between NUMA hinting faults and prot_none faults. This decision was x86-specific and conceptually it is difficult requiring special casing to distinguish between PROTNONE and NUMA ptes based on context. Fundamentally, we only need the _PAGE_NUMA bit to tell the difference between an entry that is really unmapped and a page that is protected for NUMA hinting faults as if the PTE is not present then a fault will be trapped. Swap PTEs on x86-64 use the bits after _PAGE_GLOBAL for the offset. This patch shrinks the maximum possible swap size and uses the bit to uniquely distinguish between NUMA hinting ptes and swap ptes. Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Anvin <hpa@zytor.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Steven Noonan <steven@uplinklabs.net> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memory.c')
-rw-r--r--mm/memory.c17
1 files changed, 7 insertions, 10 deletions
diff --git a/mm/memory.c b/mm/memory.c
index e302ae1dcce0..0897830011f3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -756,7 +756,7 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn = pte_pfn(pte);
if (HAVE_PTE_SPECIAL) {
- if (likely(!pte_special(pte)))
+ if (likely(!pte_special(pte) || pte_numa(pte)))
goto check_pfn;
if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
return NULL;
@@ -782,14 +782,15 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
}
}
- if (is_zero_pfn(pfn))
- return NULL;
check_pfn:
if (unlikely(pfn > highest_memmap_pfn)) {
print_bad_pte(vma, addr, pte, NULL);
return NULL;
}
+ if (is_zero_pfn(pfn))
+ return NULL;
+
/*
* NOTE! We still have PageReserved() pages in the page tables.
* eg. VDSO mappings can cause them to exist.
@@ -1722,13 +1723,9 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
/*
- * If FOLL_FORCE and FOLL_NUMA are both set, handle_mm_fault
- * would be called on PROT_NONE ranges. We must never invoke
- * handle_mm_fault on PROT_NONE ranges or the NUMA hinting
- * page faults would unprotect the PROT_NONE ranges if
- * _PAGE_NUMA and _PAGE_PROTNONE are sharing the same pte/pmd
- * bitflag. So to avoid that, don't set FOLL_NUMA if
- * FOLL_FORCE is set.
+ * If FOLL_FORCE is set then do not force a full fault as the hinting
+ * fault information is unrelated to the reference behaviour of a task
+ * using the address space
*/
if (!(gup_flags & FOLL_FORCE))
gup_flags |= FOLL_NUMA;