userfaultfd: hugetlbfs: add copy_huge_page_from_user for hugetlb userfaultfd support
userfaultfd UFFDIO_COPY allows user level code to copy data to a page at
fault time. The data is copied from user space to a newly allocated
huge page. The new routine copy_huge_page_from_user performs this copy.
Link: http://lkml.kernel.org/r/20161216144821.5183-17-aarcange@redhat.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3787f04..6bc7f2c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2424,6 +2424,9 @@ extern void clear_huge_page(struct page *page,
extern void copy_user_huge_page(struct page *dst, struct page *src,
unsigned long addr, struct vm_area_struct *vma,
unsigned int pages_per_huge_page);
+extern long copy_huge_page_from_user(struct page *dst_page,
+ const void __user *usr_src,
+ unsigned int pages_per_huge_page);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
extern struct page_ext_operations debug_guardpage_ops;