[RFC PATCH v2 1/5] mm: Refactor folio_clear_dirty_for_io()

[Ojaswin Mujoo <ojaswin@linux.ibm.com>]

Add a new __folio_clear_dirty_for_io() helper which takes an extra
parameter to indicate folio_mkclean() is needed. This is in preparation
of buffered writethrough support where we already do folio_mkclean()
before calling into this function.

Co-developed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
---
 mm/page-writeback.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 601a5e048d12..2f0c6916213d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2847,8 +2847,11 @@ EXPORT_SYMBOL(__folio_cancel_dirty);
  *
  * This incoherency between the folio's dirty flag and xarray tag is
  * unfortunate, but it only exists while the folio is locked.
+ *
+ * For some cases we might not want to do mkclean, eg, if we've already taken
+ * care of it, hence pass the should_mkclean flag to indicate if its needed.
  */
-bool folio_clear_dirty_for_io(struct folio *folio)
+static bool __folio_clear_dirty_for_io(struct folio *folio, bool should_mkclean)
 {
 	struct address_space *mapping = folio_mapping(folio);
 	bool ret = false;
@@ -2885,7 +2888,7 @@ bool folio_clear_dirty_for_io(struct folio *folio)
 		 * as a serialization point for all the different
 		 * threads doing their things.
 		 */
-		if (folio_mkclean(folio))
+		if (should_mkclean && folio_mkclean(folio))
 			folio_mark_dirty(folio);
 		/*
 		 * We carefully synchronise fault handlers against
@@ -2908,6 +2911,11 @@ bool folio_clear_dirty_for_io(struct folio *folio)
 	}
 	return folio_test_clear_dirty(folio);
 }
+
+bool folio_clear_dirty_for_io(struct folio *folio)
+{
+	return __folio_clear_dirty_for_io(folio, true);
+}
 EXPORT_SYMBOL(folio_clear_dirty_for_io);
 
 static void wb_inode_writeback_start(struct bdi_writeback *wb)
-- 
2.53.0