thp: madvise(MADV_HUGEPAGE)

Add madvise MADV_HUGEPAGE to mark regions that are important to be
hugepage backed.  Return -EINVAL if the vma is not of an anonymous type,
or the feature isn't built into the kernel.  Never silently return
success.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-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, 16 insertions, 0 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 763507932898..620891f4e54f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -896,6 +896,22 @@ out:
         return ret;
 }
 
+int hugepage_madvise(unsigned long *vm_flags)
+{
+        /*
+         * Be somewhat over-protective like KSM for now!
+         */
+        if (*vm_flags & (VM_HUGEPAGE | VM_SHARED  | VM_MAYSHARE   |
+                         VM_PFNMAP   | VM_IO      | VM_DONTEXPAND |
+                         VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
+                         VM_MIXEDMAP | VM_SAO))
+                return -EINVAL;
+
+        *vm_flags |= VM_HUGEPAGE;
+
+        return 0;
+}
+
 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
 {
         struct page *page;