input: remove f_version abuse

f_version is removed from struct file. Make input stop abusing f_version
for stashing information for poll. Move the input state counter into
input_seq_state and allocate it via seq_private_open() and free via
seq_release_private().

Link: https://lore.kernel.org/r/20240830-vfs-file-f_version-v1-12-6d3e4816aa7b@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

drivers/input/input.c

@@ -1079,33 +1079,31 @@ static inline void input_wakeup_procfs_readers(void)
 	wake_up(&input_devices_poll_wait);
 }
 
+struct input_seq_state {
+	unsigned short pos;
+	bool mutex_acquired;
+	int input_devices_state;
+};
+
 static __poll_t input_proc_devices_poll(struct file *file, poll_table *wait)
 {
+	struct seq_file *seq = file->private_data;
+	struct input_seq_state *state = seq->private;
+
 	poll_wait(file, &input_devices_poll_wait, wait);
-	if (file->f_version != input_devices_state) {
-		file->f_version = input_devices_state;
+	if (state->input_devices_state != input_devices_state) {
+		state->input_devices_state = input_devices_state;
 		return EPOLLIN | EPOLLRDNORM;
 	}
 
 	return 0;
 }
 
-union input_seq_state {
-	struct {
-		unsigned short pos;
-		bool mutex_acquired;
-	};
-	void *p;
-};
-
 static void *input_devices_seq_start(struct seq_file *seq, loff_t *pos)
 {
-	union input_seq_state *state = (union input_seq_state *)&seq->private;
+	struct input_seq_state *state = seq->private;
 	int error;
 
-	/* We need to fit into seq->private pointer */
-	BUILD_BUG_ON(sizeof(union input_seq_state) != sizeof(seq->private));
-
 	error = mutex_lock_interruptible(&input_mutex);
 	if (error) {
 		state->mutex_acquired = false;
@@ -1124,7 +1122,7 @@ static void *input_devices_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 
 static void input_seq_stop(struct seq_file *seq, void *v)
 {
-	union input_seq_state *state = (union input_seq_state *)&seq->private;
+	struct input_seq_state *state = seq->private;
 
 	if (state->mutex_acquired)
 		mutex_unlock(&input_mutex);
@@ -1210,25 +1208,23 @@ static const struct seq_operations input_devices_seq_ops = {
 
 static int input_proc_devices_open(struct inode *inode, struct file *file)
 {
-	return seq_open(file, &input_devices_seq_ops);
+	return seq_open_private(file, &input_devices_seq_ops,
+				sizeof(struct input_seq_state));
 }
 
 static const struct proc_ops input_devices_proc_ops = {
 	.proc_open	= input_proc_devices_open,
 	.proc_poll	= input_proc_devices_poll,
 	.proc_read	= seq_read,
 	.proc_lseek	= seq_lseek,
-	.proc_release	= seq_release,
+	.proc_release	= seq_release_private,
 };
 
 static void *input_handlers_seq_start(struct seq_file *seq, loff_t *pos)
 {
-	union input_seq_state *state = (union input_seq_state *)&seq->private;
+	struct input_seq_state *state = seq->private;
 	int error;
 
-	/* We need to fit into seq->private pointer */
-	BUILD_BUG_ON(sizeof(union input_seq_state) != sizeof(seq->private));
-
 	error = mutex_lock_interruptible(&input_mutex);
 	if (error) {
 		state->mutex_acquired = false;
@@ -1243,7 +1239,7 @@ static void *input_handlers_seq_start(struct seq_file *seq, loff_t *pos)
 
 static void *input_handlers_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
-	union input_seq_state *state = (union input_seq_state *)&seq->private;
+	struct input_seq_state *state = seq->private;
 
 	state->pos = *pos + 1;
 	return seq_list_next(v, &input_handler_list, pos);
@@ -1252,7 +1248,7 @@ static void *input_handlers_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 static int input_handlers_seq_show(struct seq_file *seq, void *v)
 {
 	struct input_handler *handler = container_of(v, struct input_handler, node);
-	union input_seq_state *state = (union input_seq_state *)&seq->private;
+	struct input_seq_state *state = seq->private;
 
 	seq_printf(seq, "N: Number=%u Name=%s", state->pos, handler->name);
 	if (handler->filter)
@@ -1273,14 +1269,15 @@ static const struct seq_operations input_handlers_seq_ops = {
 
 static int input_proc_handlers_open(struct inode *inode, struct file *file)
 {
-	return seq_open(file, &input_handlers_seq_ops);
+	return seq_open_private(file, &input_handlers_seq_ops,
+				sizeof(struct input_seq_state));
 }
 
 static const struct proc_ops input_handlers_proc_ops = {
 	.proc_open	= input_proc_handlers_open,
 	.proc_read	= seq_read,
 	.proc_lseek	= seq_lseek,
-	.proc_release	= seq_release,
+	.proc_release	= seq_release_private,
 };
 
 static int __init input_proc_init(void)