[PATCH v1 2/2] mm: remove BDI_CAP_WRITEBACK_ACCT

[Joanne Koong <joannelkoong@xxxxxxxxx>]

There are no users of BDI_CAP_WRITEBACK_ACCT now that fuse doesn't do
its own writeback accounting. This commit removes
BDI_CAP_WRITEBACK_ACCT.

Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
---
 include/linux/backing-dev.h |  4 +---
 mm/backing-dev.c            |  2 +-
 mm/page-writeback.c         | 43 ++++++++++++++++---------------------
 3 files changed, 20 insertions(+), 29 deletions(-)

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 9a1e895dd5df..3e64f14739dd 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -108,12 +108,10 @@ int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit
  *
  * BDI_CAP_WRITEBACK:		Supports dirty page writeback, and dirty pages
  *				should contribute to accounting
- * BDI_CAP_WRITEBACK_ACCT:	Automatically account writeback pages
  * BDI_CAP_STRICTLIMIT:		Keep number of dirty pages below bdi threshold
  */
 #define BDI_CAP_WRITEBACK		(1 << 0)
-#define BDI_CAP_WRITEBACK_ACCT		(1 << 1)
-#define BDI_CAP_STRICTLIMIT		(1 << 2)
+#define BDI_CAP_STRICTLIMIT		(1 << 1)
 
 extern struct backing_dev_info noop_backing_dev_info;
 
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 783904d8c5ef..35f11e75e30e 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -1026,7 +1026,7 @@ struct backing_dev_info *bdi_alloc(int node_id)
 		kfree(bdi);
 		return NULL;
 	}
-	bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
+	bdi->capabilities = BDI_CAP_WRITEBACK;
 	bdi->ra_pages = VM_READAHEAD_PAGES;
 	bdi->io_pages = VM_READAHEAD_PAGES;
 	timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 72b0ff0d4bae..11f9a909e8de 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -3016,26 +3016,22 @@ bool __folio_end_writeback(struct folio *folio)
 
 	if (mapping && mapping_use_writeback_tags(mapping)) {
 		struct inode *inode = mapping->host;
-		struct backing_dev_info *bdi = inode_to_bdi(inode);
+		struct bdi_writeback *wb = inode_to_wb(inode);
 		unsigned long flags;
 
 		xa_lock_irqsave(&mapping->i_pages, flags);
 		ret = folio_xor_flags_has_waiters(folio, 1 << PG_writeback);
 		__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);
 
-			wb_stat_mod(wb, WB_WRITEBACK, -nr);
-			__wb_writeout_add(wb, nr);
-			if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
-				wb_inode_writeback_end(wb);
+		wb_stat_mod(wb, WB_WRITEBACK, -nr);
+		__wb_writeout_add(wb, nr);
+		if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) {
+			wb_inode_writeback_end(wb);
+			if (mapping->host)
+				sb_clear_inode_writeback(mapping->host);
 		}
 
-		if (mapping->host && !mapping_tagged(mapping,
-						     PAGECACHE_TAG_WRITEBACK))
-			sb_clear_inode_writeback(mapping->host);
-
 		xa_unlock_irqrestore(&mapping->i_pages, flags);
 	} else {
 		ret = folio_xor_flags_has_waiters(folio, 1 << PG_writeback);
@@ -3060,7 +3056,7 @@ void __folio_start_writeback(struct folio *folio, bool keep_write)
 	if (mapping && mapping_use_writeback_tags(mapping)) {
 		XA_STATE(xas, &mapping->i_pages, folio_index(folio));
 		struct inode *inode = mapping->host;
-		struct backing_dev_info *bdi = inode_to_bdi(inode);
+		struct bdi_writeback *wb = inode_to_wb(inode);
 		unsigned long flags;
 		bool on_wblist;
 
@@ -3071,21 +3067,18 @@ void __folio_start_writeback(struct folio *folio, bool keep_write)
 		on_wblist = mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK);
 
 		xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK);
-		if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
-			struct bdi_writeback *wb = inode_to_wb(inode);
-
-			wb_stat_mod(wb, WB_WRITEBACK, nr);
-			if (!on_wblist)
-				wb_inode_writeback_start(wb);
+		wb_stat_mod(wb, WB_WRITEBACK, nr);
+		if (!on_wblist) {
+			wb_inode_writeback_start(wb);
+			/*
+			 * We can come through here when swapping anonymous
+			 * folios, so we don't necessarily have an inode to
+			 * track for sync.
+			 */
+			if (mapping->host)
+				sb_mark_inode_writeback(mapping->host);
 		}
 
-		/*
-		 * We can come through here when swapping anonymous
-		 * folios, so we don't necessarily have an inode to
-		 * track for sync.
-		 */
-		if (mapping->host && !on_wblist)
-			sb_mark_inode_writeback(mapping->host);
 		if (!folio_test_dirty(folio))
 			xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY);
 		if (!keep_write)
-- 
2.47.1