[RFC PATCH v3 1/8] mm/gup: break out gup_fill_pages() helper

[Rik van Riel <riel@surriel.com>]

__get_user_pages() fills pages[] and flushes each page's caches in an
open-coded loop.

Move it into a gup_fill_pages() helper, which the follow_page_mask()
call chain can then use to fill its own pages[] slots.

No functional changes intended.

Suggested-by: David Hildenbrand <david@kernel.org>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Rik van Riel <riel@surriel.com>
---
 mm/gup.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 0692119b7904..7bb40be89529 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -633,6 +633,23 @@ static struct page *no_page_table(struct vm_area_struct *vma,
 	return NULL;
 }
 
+static void gup_fill_pages(struct vm_area_struct *vma, unsigned long address,
+		struct page *page, unsigned long nr, struct page **pages)
+{
+	unsigned long i;
+
+	if (!pages)
+		return;
+
+	for (i = 0; i < nr; i++) {
+		struct page *subpage = page + i;
+
+		pages[i] = subpage;
+		flush_anon_page(vma, subpage, address + i * PAGE_SIZE);
+		flush_dcache_page(subpage);
+	}
+}
+
 #ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES
 /* FOLL_FORCE can write to even unwritable PUDs in COW mappings. */
 static inline bool can_follow_write_pud(pud_t pud, struct page *page,
@@ -1461,9 +1478,6 @@ static long __get_user_pages(struct mm_struct *mm,
 			page_increm = nr_pages;
 
 		if (pages) {
-			struct page *subpage;
-			unsigned int j;
-
 			/*
 			 * This must be a large folio (and doesn't need to
 			 * be the whole folio; it can be part of it), do
@@ -1493,12 +1507,7 @@ static long __get_user_pages(struct mm_struct *mm,
 				}
 			}
 
-			for (j = 0; j < page_increm; j++) {
-				subpage = page + j;
-				pages[i + j] = subpage;
-				flush_anon_page(vma, subpage, start + j * PAGE_SIZE);
-				flush_dcache_page(subpage);
-			}
+			gup_fill_pages(vma, start, page, page_increm, pages + i);
 		}
 
 		i += page_increm;
-- 
2.55.0