mm/swap: Add folio_rotate_reclaimable()

Convert rotate_reclaimable_page() to folio_rotate_reclaimable().  This
eliminates all five of the calls to compound_head() in this function,
saving 75 bytes at the cost of adding 15 bytes to its one caller,
end_page_writeback().  We also save 36 bytes from pagevec_move_tail_fn()
due to using folios there.  Net 96 bytes savings.

Also move its declaration to mm/internal.h as it's only used by filemap.c.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: David Howells <dhowells@redhat.com>

include/linux/swap.h

@@ -371,7 +371,6 @@ extern void lru_add_drain(void);
 extern void lru_add_drain_cpu(int cpu);
 extern void lru_add_drain_cpu_zone(struct zone *zone);
 extern void lru_add_drain_all(void);
-extern void rotate_reclaimable_page(struct page *page);
 extern void deactivate_file_page(struct page *page);
 extern void deactivate_page(struct page *page);
 extern void mark_page_lazyfree(struct page *page);

mm/filemap.c

@@ -1584,8 +1584,9 @@ void end_page_writeback(struct page *page)
 	 * ever page writeback.
 	 */
 	if (PageReclaim(page)) {
+		struct folio *folio = page_folio(page);
 		ClearPageReclaim(page);
-		rotate_reclaimable_page(page);
+		folio_rotate_reclaimable(folio);
 	}
 
 	/*

mm/internal.h

@@ -35,6 +35,7 @@
 void page_writeback_init(void);
 
 vm_fault_t do_swap_page(struct vm_fault *vmf);
+void folio_rotate_reclaimable(struct folio *folio);
 
 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 		unsigned long floor, unsigned long ceiling);

mm/page_io.c

@@ -38,7 +38,7 @@ void end_swap_bio_write(struct bio *bio)
 		 * Also print a dire warning that things will go BAD (tm)
 		 * very quickly.
 		 *
-		 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
+		 * Also clear PG_reclaim to avoid folio_rotate_reclaimable()
 		 */
 		set_page_dirty(page);
 		pr_alert_ratelimited("Write-error on swap-device (%u:%u:%llu)\n",
@@ -317,7 +317,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
 			 * temporary failure if the system has limited
 			 * memory for allocating transmit buffers.
 			 * Mark the page dirty and avoid
-			 * rotate_reclaimable_page but rate-limit the
+			 * folio_rotate_reclaimable but rate-limit the
 			 * messages but do not flag PageError like
 			 * the normal direct-to-bio case as it could
 			 * be temporary.

mm/swap.c

@@ -206,11 +206,13 @@ static void pagevec_lru_move_fn(struct pagevec *pvec,
 
 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec)
 {
-	if (!PageUnevictable(page)) {
-		del_page_from_lru_list(page, lruvec);
-		ClearPageActive(page);
-		add_page_to_lru_list_tail(page, lruvec);
-		__count_vm_events(PGROTATED, thp_nr_pages(page));
+	struct folio *folio = page_folio(page);
+
+	if (!folio_test_unevictable(folio)) {
+		lruvec_del_folio(lruvec, folio);
+		folio_clear_active(folio);
+		lruvec_add_folio_tail(lruvec, folio);
+		__count_vm_events(PGROTATED, folio_nr_pages(folio));
 	}
 }
 
@@ -227,23 +229,23 @@ static bool pagevec_add_and_need_flush(struct pagevec *pvec, struct page *page)
 }
 
 /*
- * Writeback is about to end against a page which has been marked for immediate
- * reclaim.  If it still appears to be reclaimable, move it to the tail of the
- * inactive list.
+ * Writeback is about to end against a folio which has been marked for
+ * immediate reclaim.  If it still appears to be reclaimable, move it
+ * to the tail of the inactive list.
  *
- * rotate_reclaimable_page() must disable IRQs, to prevent nasty races.
+ * folio_rotate_reclaimable() must disable IRQs, to prevent nasty races.
  */
-void rotate_reclaimable_page(struct page *page)
+void folio_rotate_reclaimable(struct folio *folio)
 {
-	if (!PageLocked(page) && !PageDirty(page) &&
-	    !PageUnevictable(page) && PageLRU(page)) {
+	if (!folio_test_locked(folio) && !folio_test_dirty(folio) &&
+	    !folio_test_unevictable(folio) && folio_test_lru(folio)) {
 		struct pagevec *pvec;
 		unsigned long flags;
 
-		get_page(page);
+		folio_get(folio);
 		local_lock_irqsave(&lru_rotate.lock, flags);
 		pvec = this_cpu_ptr(&lru_rotate.pvec);
-		if (pagevec_add_and_need_flush(pvec, page))
+		if (pagevec_add_and_need_flush(pvec, &folio->page))
 			pagevec_lru_move_fn(pvec, pagevec_move_tail_fn);
 		local_unlock_irqrestore(&lru_rotate.lock, flags);
 	}