[PATCH v2 1/3] userfaultfd: convert mcopy_atomic_pte() to use a folio

[Peng Zhang]

From: ZhangPeng <zhangpeng362@xxxxxxxxxx>

Call vma_alloc_folio() directly instead of alloc_page_vma(). Add an
assertion that this is a single-page folio and removes several calls to
compound_head().

Signed-off-by: ZhangPeng <zhangpeng362@xxxxxxxxxx>
---
 mm/userfaultfd.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 53c3d916ff66..263191c37fb5 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -137,15 +137,15 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
 {
 	void *page_kaddr;
 	int ret;
-	struct page *page;
+	struct folio *folio;
 
 	if (!*pagep) {
 		ret = -ENOMEM;
-		page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
-		if (!page)
+		folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, dst_vma, dst_addr, false);
+		if (!folio)
 			goto out;
 
-		page_kaddr = kmap_local_page(page);
+		page_kaddr = kmap_local_folio(folio, 0);
 		/*
 		 * The read mmap_lock is held here.  Despite the
 		 * mmap_lock being read recursive a deadlock is still
@@ -171,36 +171,37 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
 		/* fallback to copy_from_user outside mmap_lock */
 		if (unlikely(ret)) {
 			ret = -ENOENT;
-			*pagep = page;
+			*pagep = &folio->page;
 			/* don't free the page */
 			goto out;
 		}
 
-		flush_dcache_page(page);
+		flush_dcache_folio(folio);
 	} else {
-		page = *pagep;
+		folio = page_folio(*pagep);
+		VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
 		*pagep = NULL;
 	}
 
 	/*
-	 * The memory barrier inside __SetPageUptodate makes sure that
+	 * The memory barrier inside __folio_mark_uptodate makes sure that
 	 * preceding stores to the page contents become visible before
 	 * the set_pte_at() write.
 	 */
-	__SetPageUptodate(page);
+	__folio_mark_uptodate(folio);
 
 	ret = -ENOMEM;
-	if (mem_cgroup_charge(page_folio(page), dst_mm, GFP_KERNEL))
+	if (mem_cgroup_charge(folio, dst_mm, GFP_KERNEL))
 		goto out_release;
 
 	ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
-				       page, true, wp_copy);
+				       &folio->page, true, wp_copy);
 	if (ret)
 		goto out_release;
 out:
 	return ret;
 out_release:
-	put_page(page);
+	folio_put(folio);
 	goto out;
 }
 
-- 
2.25.1