Makes dept able to track PG_writeback waits and events, which will be
useful in practice.

Signed-off-by: Byungchul Park <byungchul@sk.com>
---
 include/linux/mm_types.h   | 1 +
 include/linux/page-flags.h | 7 +++++++
 mm/filemap.c               | 6 +++++-
 mm/mm_init.c               | 1 +
 4 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 85d06073d37b..fa6ba4196e0d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -222,6 +222,7 @@ struct page {
 #endif
 	struct dept_page_usage usage;
 	struct dept_ext_wgen pg_locked_wgen;
+	struct dept_ext_wgen pg_writeback_wgen;
 } _struct_page_alignment;
 
 /*
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 0b0655354b08..ec736811a2c6 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -203,6 +203,7 @@ enum pageflags {
 #include <linux/dept.h>
 
 extern struct dept_map pg_locked_map;
+extern struct dept_map pg_writeback_map;
 
 static inline void dept_set_page_usage(struct page *p,
 		unsigned int new_type)
@@ -292,6 +293,8 @@ static inline void dept_page_set_bit(struct page *p, int bit_nr)
 
 	if (bit_nr == PG_locked)
 		dept_request_event(&pg_locked_map, &p->pg_locked_wgen);
+	else if (bit_nr == PG_writeback)
+		dept_request_event(&pg_writeback_map, &p->pg_writeback_wgen);
 }
 
 static inline void dept_page_clear_bit(struct page *p, int bit_nr)
@@ -300,6 +303,8 @@ static inline void dept_page_clear_bit(struct page *p, int bit_nr)
 
 	if (bit_nr == PG_locked)
 		dept_event(&pg_locked_map, evt_f, _RET_IP_, __func__, &p->pg_locked_wgen);
+	else if (bit_nr == PG_writeback)
+		dept_event(&pg_writeback_map, evt_f, _RET_IP_, __func__, &p->pg_writeback_wgen);
 }
 
 static inline void dept_page_wait_on_bit(struct page *p, int bit_nr)
@@ -311,6 +316,8 @@ static inline void dept_page_wait_on_bit(struct page *p, int bit_nr)
 
 	if (bit_nr == PG_locked)
 		dept_wait(&pg_locked_map, evt_f, _RET_IP_, __func__, 0, -1L);
+	else if (bit_nr == PG_writeback)
+		dept_wait(&pg_writeback_map, evt_f, _RET_IP_, __func__, 0, -1L);
 }
 
 static inline void dept_folio_set_bit(struct folio *f, int bit_nr)
diff --git a/mm/filemap.c b/mm/filemap.c
index d7e567af3261..0ce3f9307582 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1191,7 +1191,7 @@ static void folio_wake_bit(struct folio *folio, int bit_nr)
 	 * dept_page_clear_bit() being called multiple times is harmless.
 	 * The worst case is to miss some dependencies but it's okay.
 	 */
-	if (bit_nr == PG_locked)
+	if (bit_nr == PG_locked || bit_nr == PG_writeback)
 		dept_page_clear_bit(&folio->page, bit_nr);
 
 	spin_lock_irqsave(&q->lock, flags);
@@ -1248,6 +1248,9 @@ static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
 struct dept_map __maybe_unused pg_locked_map = DEPT_MAP_INITIALIZER(pg_locked_map, NULL);
 EXPORT_SYMBOL(pg_locked_map);
 
+struct dept_map __maybe_unused pg_writeback_map = DEPT_MAP_INITIALIZER(pg_writeback_map, NULL);
+EXPORT_SYMBOL(pg_writeback_map);
+
 static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
 		int state, enum behavior behavior)
 {
@@ -1686,6 +1689,7 @@ void folio_end_writeback_no_dropbehind(struct folio *folio)
 		folio_rotate_reclaimable(folio);
 	}
 
+	dept_page_clear_bit(&folio->page, PG_writeback);
 	if (__folio_end_writeback(folio))
 		folio_wake_bit(folio, PG_writeback);
 
diff --git a/mm/mm_init.c b/mm/mm_init.c
index f1d3e4afd43b..9f99eeb99ca3 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -589,6 +589,7 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn,
 	page_cpupid_reset_last(page);
 	page_kasan_tag_reset(page);
 	dept_ext_wgen_init(&page->pg_locked_wgen);
+	dept_ext_wgen_init(&page->pg_writeback_wgen);
 
 	INIT_LIST_HEAD(&page->lru);
 #ifdef WANT_PAGE_VIRTUAL
-- 
2.17.1