From ffed79e366a08959be9ff47c838d5e42d059c188 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@google.com>
Date: Thu, 7 Sep 2023 10:48:30 +0000
Subject: [PATCH] Revert "sched/psi: use kernfs polling functions for PSI
 trigger polling"

This reverts commit 92cc0153324b6ae8577a39f5bf2cd83c9a34ea6a which is
commit aff037078ecaecf34a7c2afab1341815f90fba5e upstream.

It is part of a patch series that breaks the Android API.  If this
series is needed in Android devices in the future, it can come back in
an ABI-safe manner.

Bug: 161946584
Change-Id: I2c941ec44d5261a914d95591b7918e46f7db825a
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
---
 include/linux/psi.h       |  5 ++---
 include/linux/psi_types.h |  3 ---
 kernel/cgroup/cgroup.c    |  2 +-
 kernel/sched/psi.c        | 29 ++++++++---------------------
 4 files changed, 11 insertions(+), 28 deletions(-)

diff --git a/include/linux/psi.h b/include/linux/psi.h
index e0745873e3f2..ab26200c2803 100644
--- a/include/linux/psi.h
+++ b/include/linux/psi.h
@@ -23,9 +23,8 @@ void psi_memstall_enter(unsigned long *flags);
 void psi_memstall_leave(unsigned long *flags);
 
 int psi_show(struct seq_file *s, struct psi_group *group, enum psi_res res);
-struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,
-				       enum psi_res res, struct file *file,
-				       struct kernfs_open_file *of);
+struct psi_trigger *psi_trigger_create(struct psi_group *group,
+			char *buf, enum psi_res res, struct file *file);
 void psi_trigger_destroy(struct psi_trigger *t);
 
 __poll_t psi_trigger_poll(void **trigger_ptr, struct file *file,
diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
index f1fd3a8044e0..040c089581c6 100644
--- a/include/linux/psi_types.h
+++ b/include/linux/psi_types.h
@@ -137,9 +137,6 @@ struct psi_trigger {
 	/* Wait queue for polling */
 	wait_queue_head_t event_wait;
 
-	/* Kernfs file for cgroup triggers */
-	struct kernfs_open_file *of;
-
 	/* Pending event flag */
 	int event;
 
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 9a9603937e31..556c3eeb64dc 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3777,7 +3777,7 @@ static ssize_t pressure_write(struct kernfs_open_file *of, char *buf,
 	}
 
 	psi = cgroup_psi(cgrp);
-	new = psi_trigger_create(psi, buf, res, of->file, of);
+	new = psi_trigger_create(psi, buf, res, of->file);
 	if (IS_ERR(new)) {
 		cgroup_put(cgrp);
 		return PTR_ERR(new);
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 2507c90b74c1..2183d3431cde 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -494,12 +494,8 @@ static u64 update_triggers(struct psi_group *group, u64 now, bool *update_total,
 			continue;
 
 		/* Generate an event */
-		if (cmpxchg(&t->event, 0, 1) == 0) {
-			if (t->of)
-				kernfs_notify(t->of->kn);
-			else
-				wake_up_interruptible(&t->event_wait);
-		}
+		if (cmpxchg(&t->event, 0, 1) == 0)
+			wake_up_interruptible(&t->event_wait);
 		t->last_event_time = now;
 		/* Reset threshold breach flag once event got generated */
 		t->pending_event = false;
@@ -1276,9 +1272,8 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res)
 	return 0;
 }
 
-struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,
-				       enum psi_res res, struct file *file,
-				       struct kernfs_open_file *of)
+struct psi_trigger *psi_trigger_create(struct psi_group *group,
+			char *buf, enum psi_res res, struct file *file)
 {
 	struct psi_trigger *t;
 	enum psi_states state;
@@ -1337,9 +1332,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,
 
 	t->event = 0;
 	t->last_event_time = 0;
-	t->of = of;
-	if (!of)
-		init_waitqueue_head(&t->event_wait);
+	init_waitqueue_head(&t->event_wait);
 	t->pending_event = false;
 	t->aggregator = privileged ? PSI_POLL : PSI_AVGS;
 
@@ -1396,10 +1389,7 @@ void psi_trigger_destroy(struct psi_trigger *t)
 	 * being accessed later. Can happen if cgroup is deleted from under a
 	 * polling process.
 	 */
-	if (t->of)
-		kernfs_notify(t->of->kn);
-	else
-		wake_up_interruptible(&t->event_wait);
+	wake_up_pollfree(&t->event_wait);
 
 	if (t->aggregator == PSI_AVGS) {
 		mutex_lock(&group->avgs_lock);
@@ -1471,10 +1461,7 @@ __poll_t psi_trigger_poll(void **trigger_ptr,
 	if (!t)
 		return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI;
 
-	if (t->of)
-		kernfs_generic_poll(t->of, wait);
-	else
-		poll_wait(file, &t->event_wait, wait);
+	poll_wait(file, &t->event_wait, wait);
 
 	if (cmpxchg(&t->event, 1, 0) == 1)
 		ret |= EPOLLPRI;
@@ -1544,7 +1531,7 @@ static ssize_t psi_write(struct file *file, const char __user *user_buf,
 		return -EBUSY;
 	}
 
-	new = psi_trigger_create(&psi_system, buf, res, file, NULL);
+	new = psi_trigger_create(&psi_system, buf, res, file);
 	if (IS_ERR(new)) {
 		mutex_unlock(&seq->lock);
 		return PTR_ERR(new);