mm/hugetlb: add page_mask for hugetlb_follow_page_mask()

follow_page() doesn't need it, but we'll start to need it when unifying
gup for hugetlb.

Link: https://lkml.kernel.org/r/20230628215310.73782-4-peterx@redhat.comSigned-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A . Shutemov <kirill@shutemov.name>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/hugetlb.h

@@ -131,7 +131,8 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma,
 int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *,
 			    struct vm_area_struct *, struct vm_area_struct *);
 struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
-				unsigned long address, unsigned int flags);
+				      unsigned long address, unsigned int flags,
+				      unsigned int *page_mask);
 long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
 			 struct page **, unsigned long *, unsigned long *,
 			 long, unsigned int, int *);
@@ -297,8 +298,9 @@ static inline void adjust_range_if_pmd_sharing_possible(
 {
 }
 
-static inline struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
-				unsigned long address, unsigned int flags)
+static inline struct page *hugetlb_follow_page_mask(
+    struct vm_area_struct *vma, unsigned long address, unsigned int flags,
+    unsigned int *page_mask)
 {
 	BUILD_BUG(); /* should never be compiled in if !CONFIG_HUGETLB_PAGE*/
 }

mm/gup.c

@@ -824,7 +824,8 @@ static struct page *follow_page_mask(struct vm_area_struct *vma,
 	 * Ordinary GUP uses follow_hugetlb_page for hugetlb processing.
 	 */
 	if (is_vm_hugetlb_page(vma))
-		return hugetlb_follow_page_mask(vma, address, flags);
+		return hugetlb_follow_page_mask(vma, address, flags,
+						&ctx->page_mask);
 
 	pgd = pgd_offset(mm, address);
 

mm/hugetlb.c

@@ -6454,7 +6454,8 @@ static inline bool __follow_hugetlb_must_fault(struct vm_area_struct *vma,
 }
 
 struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
-				unsigned long address, unsigned int flags)
+				      unsigned long address, unsigned int flags,
+				      unsigned int *page_mask)
 {
 	struct hstate *h = hstate_vma(vma);
 	struct mm_struct *mm = vma->vm_mm;
@@ -6504,6 +6505,8 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
 			page = ERR_PTR(ret);
 			goto out;
 		}
+
+		*page_mask = (1U << huge_page_order(h)) - 1;
 	}
 out:
 	spin_unlock(ptl);