thp: mincore transparent hugepage support

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index ae2bf08b1099..37e89a32a0b1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -923,6 +923,31 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
         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,