Commit e944fd67 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm: numa: do not trap faults on the huge zero page 



Faults on the huge zero page are pointless and there is a BUG_ON to catch
them during fault time.  This patch reintroduces a check that avoids
marking the zero page PAGE_NONE.

Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 21d9ee3e

include/linux/huge_mm.h

+2 −1
Original line number Diff line number Diff line
@@ -31,7 +31,8 @@ extern int move_huge_pmd(struct vm_area_struct *vma, 
			 unsigned long new_addr, unsigned long old_end,

			 pmd_t *old_pmd, pmd_t *new_pmd);

extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,

			unsigned long addr, pgprot_t newprot);

			unsigned long addr, pgprot_t newprot,

			int prot_numa);



enum transparent_hugepage_flag {

	TRANSPARENT_HUGEPAGE_FLAG,

mm/huge_memory.c

+12 −1
Original line number Diff line number Diff line
@@ -1471,7 +1471,7 @@ out: 
 *  - HPAGE_PMD_NR is protections changed and TLB flush necessary

 */

int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,

		unsigned long addr, pgprot_t newprot)

		unsigned long addr, pgprot_t newprot, int prot_numa)

{

	struct mm_struct *mm = vma->vm_mm;

	spinlock_t *ptl;
@@ -1479,6 +1479,17 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 


	if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {

		pmd_t entry;



		/*

		 * Avoid trapping faults against the zero page. The read-only

		 * data is likely to be read-cached on the local CPU and

		 * local/remote hits to the zero page are not interesting.

		 */

		if (prot_numa && is_huge_zero_pmd(*pmd)) {

			spin_unlock(ptl);

			return 0;

		}



		ret = 1;

		entry = pmdp_get_and_clear_notify(mm, addr, pmd);

		entry = pmd_modify(entry, newprot);

mm/memory.c

+0 −1
Original line number Diff line number Diff line
@@ -3040,7 +3040,6 @@ static int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, 
		pte_unmap_unlock(ptep, ptl);

		return 0;

	}

	BUG_ON(is_zero_pfn(page_to_pfn(page)));



	/*

	 * Avoid grouping on DSO/COW pages in specific and RO pages

mm/mprotect.c

+13 −1
Original line number Diff line number Diff line
@@ -76,6 +76,18 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 
		if (pte_present(oldpte)) {

			pte_t ptent;



			/*

			 * Avoid trapping faults against the zero or KSM

			 * pages. See similar comment in change_huge_pmd.

			 */

			if (prot_numa) {

				struct page *page;



				page = vm_normal_page(vma, addr, oldpte);

				if (!page || PageKsm(page))

					continue;

			}



			ptent = ptep_modify_prot_start(mm, addr, pte);

			ptent = pte_modify(ptent, newprot);
@@ -142,7 +154,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, 
				split_huge_page_pmd(vma, addr, pmd);

			else {

				int nr_ptes = change_huge_pmd(vma, pmd, addr,

						newprot);

						newprot, prot_numa);



				if (nr_ptes) {

					if (nr_ptes == HPAGE_PMD_NR) {

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