[PATCH v2 24/46] mm/writeback: Add __folio_end_writeback()

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

test_clear_page_writeback() is actually an mm-internal function, although
it's named as if it's a pagecache function.  Move it to mm/internal.h,
rename it to __folio_end_writeback() and change the return type to bool.

The conversion from page to folio is mostly about accounting the number
of pages being written back, although it does eliminate a couple of
calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/page-flags.h |  1 -
 mm/filemap.c               |  2 +-
 mm/internal.h              |  1 +
 mm/page-writeback.c        | 29 +++++++++++++++--------------
 4 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 50df34886537..bdf807c98736 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -646,7 +646,6 @@ static __always_inline void SetPageUptodate(struct page *page)
 
 CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)
 
-int test_clear_page_writeback(struct page *page);
 int __test_set_page_writeback(struct page *page, bool keep_write);
 
 #define test_set_page_writeback(page)			\
diff --git a/mm/filemap.c b/mm/filemap.c
index 4b2698e5e8e2..dd360721c72b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1535,7 +1535,7 @@ void folio_end_writeback(struct folio *folio)
 	 * reused before the folio_wake().
 	 */
 	folio_get(folio);
-	if (!test_clear_page_writeback(&folio->page))
+	if (!__folio_end_writeback(folio))
 		BUG();
 
 	smp_mb__after_atomic();
diff --git a/mm/internal.h b/mm/internal.h
index 3e70121c71c7..d7013df5d1f0 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -43,6 +43,7 @@ static inline void *folio_rmapping(struct folio *folio)
 
 vm_fault_t do_swap_page(struct vm_fault *vmf);
 void folio_rotate_reclaimable(struct folio *folio);
+bool __folio_end_writeback(struct folio *folio);
 
 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 		unsigned long floor, unsigned long ceiling);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index dc66ff78f033..9213b8b6d50b 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -588,7 +588,7 @@ static void wb_domain_writeout_add(struct wb_domain *dom,
 
 /*
  * Increment @wb's writeout completion count and the global writeout
- * completion count. Called from test_clear_page_writeback().
+ * completion count. Called from __folio_end_writeback().
  */
 static inline void __wb_writeout_add(struct bdi_writeback *wb, long nr)
 {
@@ -2727,27 +2727,28 @@ int clear_page_dirty_for_io(struct page *page)
 }
 EXPORT_SYMBOL(clear_page_dirty_for_io);
 
-int test_clear_page_writeback(struct page *page)
+bool __folio_end_writeback(struct folio *folio)
 {
-	struct address_space *mapping = page_mapping(page);
-	int ret;
+	long nr = folio_nr_pages(folio);
+	struct address_space *mapping = folio_mapping(folio);
+	bool ret;
 
-	lock_page_memcg(page);
+	lock_folio_memcg(folio);
 	if (mapping && mapping_use_writeback_tags(mapping)) {
 		struct inode *inode = mapping->host;
 		struct backing_dev_info *bdi = inode_to_bdi(inode);
 		unsigned long flags;
 
 		xa_lock_irqsave(&mapping->i_pages, flags);
-		ret = TestClearPageWriteback(page);
+		ret = folio_test_clear_writeback_flag(folio);
 		if (ret) {
-			__xa_clear_mark(&mapping->i_pages, page_index(page),
+			__xa_clear_mark(&mapping->i_pages, folio_index(folio),
 						PAGECACHE_TAG_WRITEBACK);
 			if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
 				struct bdi_writeback *wb = inode_to_wb(inode);
 
-				dec_wb_stat(wb, WB_WRITEBACK);
-				__wb_writeout_add(wb, 1);
+				wb_stat_mod(wb, WB_WRITEBACK, -nr);
+				__wb_writeout_add(wb, nr);
 			}
 		}
 
@@ -2757,14 +2758,14 @@ int test_clear_page_writeback(struct page *page)
 
 		xa_unlock_irqrestore(&mapping->i_pages, flags);
 	} else {
-		ret = TestClearPageWriteback(page);
+		ret = folio_test_clear_writeback_flag(folio);
 	}
 	if (ret) {
-		dec_lruvec_page_state(page, NR_WRITEBACK);
-		dec_zone_page_state(page, NR_ZONE_WRITE_PENDING);
-		inc_node_page_state(page, NR_WRITTEN);
+		lruvec_stat_mod_folio(folio, NR_WRITEBACK, -nr);
+		zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
+		node_stat_mod_folio(folio, NR_WRITTEN, nr);
 	}
-	unlock_page_memcg(page);
+	unlock_folio_memcg(folio);
 	return ret;
 }
 
-- 
2.30.2