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               | 11 +++++++++++
 mm/mm_init.c               |  1 +
 4 files changed, 20 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 8ccbb030500c..bed1a3bc81e1 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -226,6 +226,7 @@ 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 3fd3660ddc6f..b965b16c8cee 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 int dept_set_page_usage(struct page *p,
 		unsigned int new_type)
@@ -279,6 +280,8 @@ static inline void dept_page_set_bit(struct page *p, int bit_nr)
 	dept_update_page_usage(p);
 	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)
@@ -288,6 +291,8 @@ static inline void dept_page_clear_bit(struct page *p, int bit_nr)
 	evt_f = dept_event_flags(p, false);
 	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)
@@ -298,6 +303,8 @@ static inline void dept_page_wait_on_bit(struct page *p, int bit_nr)
 	evt_f = dept_event_flags(p, true);
 	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 edb0710ddb3f..d8f1816dc6c2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1187,6 +1187,13 @@ static void folio_wake_bit(struct folio *folio, int bit_nr)
 	key.bit_nr = bit_nr;
 	key.page_match = 0;
 
+	/*
+	 * 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 || bit_nr == PG_writeback)
+		dept_page_clear_bit(&folio->page, bit_nr);
+
 	spin_lock_irqsave(&q->lock, flags);
 	__wake_up_locked_key(q, TASK_NORMAL, &key);
 
@@ -1241,6 +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)
 {
@@ -1683,6 +1693,7 @@ void folio_end_writeback(struct folio *folio)
 	 * reused before the folio_wake_bit().
 	 */
 	folio_get(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 09e4ac6a73c7..fd2bf6689afa 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