[PATCH v5 08/11] thp: setup huge zero page on non-write page fault

Kirill A. Shutemov
2012-11-07T15:01:55Z

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

All code paths seems covered. Now we can map huge zero page on read page
fault.

We setup it in do_huge_pmd_anonymous_page() if area around fault address
is suitable for THP and we've got read page fault.

If we fail to setup huge zero page (ENOMEM) we fallback to
handle_pte_fault() as we normally do in THP.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/huge_memory.c | 10 ++++++++++
1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f36bc7d..41f05f1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -726,6 +726,16 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
return VM_FAULT_OOM;
if (unlikely(khugepaged_enter(vma)))
return VM_FAULT_OOM;
+ if (!(flags & FAULT_FLAG_WRITE)) {
+ pgtable_t pgtable;
+ pgtable = pte_alloc_one(mm, haddr);
+ if (unlikely(!pgtable))
+ goto out;
+ spin_lock(&mm->page_table_lock);
+ set_huge_zero_page(pgtable, mm, vma, haddr, pmd);
+ spin_unlock(&mm->page_table_lock);
+ return 0;
+ }
page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
vma, haddr, numa_node_id(), 0);
if (unlikely(!page)) {
--
1.7.7.6