[PATCH v19 21/40] dept: make dept able to work with an external wgen

[Byungchul Park <byungchul@sk.com>]

There is a case where the total map size of waits of a class is so large.
For instance, PG_locked is the case if every struct page embeds its
regular map for PG_locked.  The total size for the maps will be 'the #
of pages * sizeof(struct dept_map)', which is too big to accept.

Keep the minimum data in the case, timestamp called 'wgen', that dept
uses.  Make dept able to work with the wgen instead of whole regular map.

Signed-off-by: Byungchul Park <byungchul@sk.com>
---
 include/linux/dept.h     | 18 ++++++++++++++----
 include/linux/dept_sdt.h |  6 +++---
 kernel/dependency/dept.c | 30 +++++++++++++++++++++---------
 3 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/include/linux/dept.h b/include/linux/dept.h
index e3e68ef47b9e..827ccc1890d1 100644
--- a/include/linux/dept.h
+++ b/include/linux/dept.h
@@ -129,6 +129,13 @@ struct dept_wait_hist {
 	unsigned int			ctxt_id;
 };
 
+/*
+ * for subsystems that requires compact use of memory e.g. struct page
+ */
+struct dept_ext_wgen {
+	unsigned int wgen;
+};
+
 void dept_on(void);
 void dept_off(void);
 void dept_init(void);
@@ -138,6 +145,7 @@ void dept_free_range(void *start, unsigned int sz);
 
 void dept_map_init(struct dept_map *m, struct dept_key *k, int sub_u, const char *n);
 void dept_map_reinit(struct dept_map *m, struct dept_key *k, int sub_u, const char *n);
+void dept_ext_wgen_init(struct dept_ext_wgen *ewg);
 void dept_map_copy(struct dept_map *to, struct dept_map *from);
 void dept_wait(struct dept_map *m, unsigned long w_f, unsigned long ip, const char *w_fn, int sub_l, long timeout);
 void dept_stage_wait(struct dept_map *m, struct dept_key *k, unsigned long ip, const char *w_fn, long timeout);
@@ -146,8 +154,8 @@ void dept_clean_stage(void);
 void dept_ttwu_stage_wait(struct task_struct *t, unsigned long ip);
 void dept_ecxt_enter(struct dept_map *m, unsigned long e_f, unsigned long ip, const char *c_fn, const char *e_fn, int sub_l);
 bool dept_ecxt_holding(struct dept_map *m, unsigned long e_f);
-void dept_request_event(struct dept_map *m);
-void dept_event(struct dept_map *m, unsigned long e_f, unsigned long ip, const char *e_fn);
+void dept_request_event(struct dept_map *m, struct dept_ext_wgen *ewg);
+void dept_event(struct dept_map *m, unsigned long e_f, unsigned long ip, const char *e_fn, struct dept_ext_wgen *ewg);
 void dept_ecxt_exit(struct dept_map *m, unsigned long e_f, unsigned long ip);
 void dept_sched_enter(void);
 void dept_sched_exit(void);
@@ -174,6 +182,7 @@ void dept_hardirqs_off(void);
 #else /* !CONFIG_DEPT */
 struct dept_key { };
 struct dept_map { };
+struct dept_ext_wgen { };
 
 #define DEPT_MAP_INITIALIZER(n, k) { }
 
@@ -186,6 +195,7 @@ struct dept_map { };
 
 #define dept_map_init(m, k, su, n)			do { (void)(n); (void)(k); } while (0)
 #define dept_map_reinit(m, k, su, n)			do { (void)(n); (void)(k); } while (0)
+#define dept_ext_wgen_init(wg)				do { } while (0)
 #define dept_map_copy(t, f)				do { } while (0)
 #define dept_wait(m, w_f, ip, w_fn, sl, t)		do { (void)(w_fn); } while (0)
 #define dept_stage_wait(m, k, ip, w_fn, t)		do { (void)(k); (void)(w_fn); } while (0)
@@ -194,8 +204,8 @@ struct dept_map { };
 #define dept_ttwu_stage_wait(t, ip)			do { } while (0)
 #define dept_ecxt_enter(m, e_f, ip, c_fn, e_fn, sl)	do { (void)(c_fn); (void)(e_fn); } while (0)
 #define dept_ecxt_holding(m, e_f)			false
-#define dept_request_event(m)				do { } while (0)
-#define dept_event(m, e_f, ip, e_fn)			do { (void)(e_fn); } while (0)
+#define dept_request_event(m, wg)			do { } while (0)
+#define dept_event(m, e_f, ip, e_fn, wg)		do { (void)(e_fn); } while (0)
 #define dept_ecxt_exit(m, e_f, ip)			do { } while (0)
 #define dept_sched_enter()				do { } while (0)
 #define dept_sched_exit()				do { } while (0)
diff --git a/include/linux/dept_sdt.h b/include/linux/dept_sdt.h
index 14917df0cc30..9cd70affaf35 100644
--- a/include/linux/dept_sdt.h
+++ b/include/linux/dept_sdt.h
@@ -25,7 +25,7 @@
 
 #define sdt_wait_timeout(m, t)						\
 	do {								\
-		dept_request_event(m);					\
+		dept_request_event(m, NULL);				\
 		dept_wait(m, 1UL, _THIS_IP_, __func__, 0, t);		\
 	} while (0)
 #define sdt_wait(m) sdt_wait_timeout(m, -1L)
@@ -49,9 +49,9 @@
 #define sdt_might_sleep_end()		dept_clean_stage()
 
 #define sdt_ecxt_enter(m)		dept_ecxt_enter(m, 1UL, _THIS_IP_, "start", "event", 0)
-#define sdt_event(m)			dept_event(m, 1UL, _THIS_IP_, __func__)
+#define sdt_event(m)			dept_event(m, 1UL, _THIS_IP_, __func__, NULL)
 #define sdt_ecxt_exit(m)		dept_ecxt_exit(m, 1UL, _THIS_IP_)
-#define sdt_request_event(m)		dept_request_event(m)
+#define sdt_request_event(m)		dept_request_event(m, NULL)
 #else /* !CONFIG_DEPT */
 #define sdt_map_init(m)			do { } while (0)
 #define sdt_map_init_key(m, k)		do { (void)(k); } while (0)
diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c
index 5ef85977e631..e425d3ab05e5 100644
--- a/kernel/dependency/dept.c
+++ b/kernel/dependency/dept.c
@@ -2172,6 +2172,11 @@ void dept_map_reinit(struct dept_map *m, struct dept_key *k, int sub_u,
 }
 EXPORT_SYMBOL_GPL(dept_map_reinit);
 
+void dept_ext_wgen_init(struct dept_ext_wgen *ewg)
+{
+	ewg->wgen = 0U;
+}
+
 void dept_map_copy(struct dept_map *to, struct dept_map *from)
 {
 	if (unlikely(!dept_working())) {
@@ -2355,7 +2360,7 @@ static void __dept_wait(struct dept_map *m, unsigned long w_f,
  */
 static void __dept_event(struct dept_map *m, struct dept_map *real_m,
 		unsigned long e_f, unsigned long ip, const char *e_fn,
-		bool sched_map)
+		bool sched_map, unsigned int wg)
 {
 	struct dept_class *c;
 	struct dept_key *k;
@@ -2377,7 +2382,7 @@ static void __dept_event(struct dept_map *m, struct dept_map *real_m,
 	c = check_new_class(&m->map_key, k, sub_id(m, e), m->name, sched_map);
 
 	if (c)
-		do_event(m, real_m, c, READ_ONCE(m->wgen), ip, e_fn);
+		do_event(m, real_m, c, wg, ip, e_fn);
 }
 
 void dept_wait(struct dept_map *m, unsigned long w_f,
@@ -2602,7 +2607,7 @@ void dept_ttwu_stage_wait(struct task_struct *requestor, unsigned long ip)
 	if (!m.keys)
 		goto exit;
 
-	__dept_event(&m, real_m, 1UL, ip, "try_to_wake_up", sched_map);
+	__dept_event(&m, real_m, 1UL, ip, "try_to_wake_up", sched_map, m.wgen);
 exit:
 	dept_exit(flags);
 }
@@ -2781,10 +2786,11 @@ bool dept_ecxt_holding(struct dept_map *m, unsigned long e_f)
 }
 EXPORT_SYMBOL_GPL(dept_ecxt_holding);
 
-void dept_request_event(struct dept_map *m)
+void dept_request_event(struct dept_map *m, struct dept_ext_wgen *ewg)
 {
 	unsigned long flags;
 	unsigned int wg;
+	unsigned int *wg_p;
 
 	if (unlikely(!dept_working()))
 		return;
@@ -2797,18 +2803,22 @@ void dept_request_event(struct dept_map *m)
 	 */
 	flags = dept_enter_recursive();
 
+	wg_p = ewg ? &ewg->wgen : &m->wgen;
+
 	wg = next_wgen();
-	WRITE_ONCE(m->wgen, wg);
+	WRITE_ONCE(*wg_p, wg);
 
 	dept_exit_recursive(flags);
 }
 EXPORT_SYMBOL_GPL(dept_request_event);
 
 void dept_event(struct dept_map *m, unsigned long e_f,
-		unsigned long ip, const char *e_fn)
+		unsigned long ip, const char *e_fn,
+		struct dept_ext_wgen *ewg)
 {
 	struct dept_task *dt = dept_task();
 	unsigned long flags;
+	unsigned int *wg_p;
 
 	if (unlikely(!dept_working()))
 		return;
@@ -2816,24 +2826,26 @@ void dept_event(struct dept_map *m, unsigned long e_f,
 	if (m->nocheck)
 		return;
 
+	wg_p = ewg ? &ewg->wgen : &m->wgen;
+
 	if (dt->recursive) {
 		/*
 		 * Dept won't work with this even though an event
 		 * context has been asked. Don't make it confused at
 		 * handling the event. Disable it until the next.
 		 */
-		WRITE_ONCE(m->wgen, 0U);
+		WRITE_ONCE(*wg_p, 0U);
 		return;
 	}
 
 	flags = dept_enter();
 
-	__dept_event(m, m, e_f, ip, e_fn, false);
+	__dept_event(m, m, e_f, ip, e_fn, false, READ_ONCE(*wg_p));
 
 	/*
 	 * Keep the map diabled until the next sleep.
 	 */
-	WRITE_ONCE(m->wgen, 0U);
+	WRITE_ONCE(*wg_p, 0U);
 
 	dept_exit(flags);
 }
-- 
2.17.1