[PATCH] mm/memory: use folio lock/ref helpers in do_swap_page

[Hongfu Li <hongfu.li@linux.dev>]

From: Hongfu Li <lihongfu@kylinos.cn>

Replace page-level lock/ref operations with their folio equivalents
in the device_private migration path of do_swap_page().

Introduce a local fault_folio to hold page_folio(vmf->page) to avoid
repeated page_folio() invocations.

Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
---
 mm/memory.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index d5e87624f692..bd27372a1052 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4852,6 +4852,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			vmf->page = softleaf_to_page(entry);
 			ret = remove_device_exclusive_entry(vmf);
 		} else if (softleaf_is_device_private(entry)) {
+			struct folio *fault_folio;
+
 			if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
 				/*
 				 * migrate_to_ram is not yet ready to operate
@@ -4863,6 +4865,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			}
 
 			vmf->page = softleaf_to_page(entry);
+			fault_folio = page_folio(vmf->page);
 			vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
 					vmf->address, &vmf->ptl);
 			if (unlikely(!vmf->pte ||
@@ -4874,15 +4877,15 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			 * Get a page reference while we know the page can't be
 			 * freed.
 			 */
-			if (trylock_page(vmf->page)) {
+			if (folio_trylock(fault_folio)) {
 				struct dev_pagemap *pgmap;
 
-				get_page(vmf->page);
+				folio_get(fault_folio);
 				pte_unmap_unlock(vmf->pte, vmf->ptl);
 				pgmap = page_pgmap(vmf->page);
 				ret = pgmap->ops->migrate_to_ram(vmf);
-				unlock_page(vmf->page);
-				put_page(vmf->page);
+				folio_unlock(fault_folio);
+				folio_put(fault_folio);
 			} else {
 				pte_unmap(vmf->pte);
 				softleaf_entry_wait_on_locked(entry, vmf->ptl);
-- 
2.54.0