mm/gup: cleanup next_page handling

The only path that doesn't use generic "**pages" handling is the gate vma.
Make it use the same path, meanwhile tune the next_page label upper to
cover "**pages" handling.  This prepares for THP handling for "**pages".

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Peter Xu <[email protected]>
Reviewed-by: Lorenzo Stoakes <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: James Houghton <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Kirill A . Shutemov <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport (IBM) <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Yang Shi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: xzpeter

mm/gup.c

@@ -1207,7 +1207,7 @@ static long __get_user_pages(struct mm_struct *mm,
 			if (!vma && in_gate_area(mm, start)) {
 				ret = get_gate_page(mm, start & PAGE_MASK,
 						gup_flags, &vma,
-						pages ? &pages[i] : NULL);
+						pages ? &page : NULL);
 				if (ret)
 					goto out;
 				ctx.page_mask = 0;
@@ -1277,19 +1277,18 @@ static long __get_user_pages(struct mm_struct *mm,
 				ret = PTR_ERR(page);
 				goto out;
 			}
-
-			goto next_page;
 		} else if (IS_ERR(page)) {
 			ret = PTR_ERR(page);
 			goto out;
 		}
+next_page:
 		if (pages) {
 			pages[i] = page;
 			flush_anon_page(vma, page, start);
 			flush_dcache_page(page);
 			ctx.page_mask = 0;
 		}
-next_page:
+
 		page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
 		if (page_increm > nr_pages)
 			page_increm = nr_pages;