[PATCH 47 of 66] mincore transparent hugepage support

Andrea Arcangeli
2010-11-03T15:37:20Z

From: Johannes Weiner <hannes@cmpxchg.org>

Handle transparent huge page pmd entries natively instead of splitting
them into subpages.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
---

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -19,6 +19,9 @@ extern struct page *follow_trans_huge_pm
extern int zap_huge_pmd(struct mmu_gather *tlb,
struct vm_area_struct *vma,
pmd_t *pmd);
+extern int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+ unsigned long addr, unsigned long end,
+ unsigned char *vec);

enum transparent_hugepage_flag {
TRANSPARENT_HUGEPAGE_FLAG,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -919,6 +919,31 @@ int zap_huge_pmd(struct mmu_gather *tlb,
return ret;
}

+int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+ unsigned long addr, unsigned long end,
+ unsigned char *vec)
+{
+ int ret = 0;
+
+ spin_lock(&vma->vm_mm->page_table_lock);
+ if (likely(pmd_trans_huge(*pmd))) {
+ ret = !pmd_trans_splitting(*pmd);
+ spin_unlock(&vma->vm_mm->page_table_lock);
+ if (unlikely(!ret))
+ wait_split_huge_page(vma->anon_vma, pmd);
+ else {
+ /*
+ * All logical pages in the range are present
+ * if backed by a huge page.
+ */
+ memset(vec, 1, (end - addr) >> PAGE_SHIFT);
+ }
+ } else
+ spin_unlock(&vma->vm_mm->page_table_lock);
+
+ return ret;
+}
+
pmd_t *page_check_address_pmd(struct page *page,
struct mm_struct *mm,
unsigned long address,
diff --git a/mm/mincore.c b/mm/mincore.c
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -154,7 +154,13 @@ static void mincore_pmd_range(struct vm_
pmd = pmd_offset(pud, addr);
do {
next = pmd_addr_end(addr, end);
- split_huge_page_pmd(vma->vm_mm, pmd);
+ if (pmd_trans_huge(*pmd)) {
+ if (mincore_huge_pmd(vma, pmd, addr, next, vec)) {
+ vec += (next - addr) >> PAGE_SHIFT;
+ continue;
+ }
+ /* fall through */
+ }
if (pmd_none_or_clear_bad(pmd))
mincore_unmapped_range(vma, addr, next, vec);
else