ftrace: Have set_graph_function handle multiple functions in one write

Currently, only one function can be written to set_graph_function and
set_graph_notrace. The last function in the list will have saved, even
though other functions will be added then removed.

Change the behavior to be the same as set_ftrace_function as to allow
multiple functions to be written. If any one fails, none of them will be
added. The addition of the functions are done at the end when the file is
closed.
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -4570,6 +4570,7 @@ struct ftrace_graph_data {
 	enum graph_filter_type		type;
 	struct ftrace_hash		*new_hash;
 	const struct seq_operations	*seq_ops;
+	struct trace_parser		parser;
 };
 
 static void *
@@ -4676,6 +4677,9 @@ __ftrace_graph_open(struct inode *inode, struct file *file,
 	if (file->f_mode & FMODE_WRITE) {
 		const int size_bits = FTRACE_HASH_DEFAULT_BITS;
 
+		if (trace_parser_get_init(&fgd->parser, FTRACE_BUFF_MAX))
+			return -ENOMEM;
+
 		if (file->f_flags & O_TRUNC)
 			new_hash = alloc_ftrace_hash(size_bits);
 		else
@@ -4701,6 +4705,9 @@ __ftrace_graph_open(struct inode *inode, struct file *file,
 		file->private_data = fgd;
 
 out:
+	if (ret < 0 && file->f_mode & FMODE_WRITE)
+		trace_parser_put(&fgd->parser);
+
 	fgd->new_hash = new_hash;
 
 	/*
@@ -4773,6 +4780,9 @@ static int
 ftrace_graph_release(struct inode *inode, struct file *file)
 {
 	struct ftrace_graph_data *fgd;
+	struct ftrace_hash *old_hash, *new_hash;
+	struct trace_parser *parser;
+	int ret = 0;
 
 	if (file->f_mode & FMODE_READ) {
 		struct seq_file *m = file->private_data;
@@ -4783,10 +4793,50 @@ ftrace_graph_release(struct inode *inode, struct file *file)
 		fgd = file->private_data;
 	}
 
+
+	if (file->f_mode & FMODE_WRITE) {
+
+		parser = &fgd->parser;
+
+		if (trace_parser_loaded((parser))) {
+			parser->buffer[parser->idx] = 0;
+			ret = ftrace_graph_set_hash(fgd->new_hash,
+						    parser->buffer);
+		}
+
+		trace_parser_put(parser);
+
+		new_hash = __ftrace_hash_move(fgd->new_hash);
+		if (!new_hash) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		mutex_lock(&graph_lock);
+
+		if (fgd->type == GRAPH_FILTER_FUNCTION) {
+			old_hash = rcu_dereference_protected(ftrace_graph_hash,
+					lockdep_is_held(&graph_lock));
+			rcu_assign_pointer(ftrace_graph_hash, new_hash);
+		} else {
+			old_hash = rcu_dereference_protected(ftrace_graph_notrace_hash,
+					lockdep_is_held(&graph_lock));
+			rcu_assign_pointer(ftrace_graph_notrace_hash, new_hash);
+		}
+
+		mutex_unlock(&graph_lock);
+
+		/* Wait till all users are no longer using the old hash */
+		synchronize_sched();
+
+		free_ftrace_hash(old_hash);
+	}
+
+ out:
 	kfree(fgd->new_hash);
 	kfree(fgd);
 
-	return 0;
+	return ret;
 }
 
 static int
@@ -4848,61 +4898,34 @@ static ssize_t
 ftrace_graph_write(struct file *file, const char __user *ubuf,
 		   size_t cnt, loff_t *ppos)
 {
-	struct trace_parser parser;
 	ssize_t read, ret = 0;
 	struct ftrace_graph_data *fgd = file->private_data;
-	struct ftrace_hash *old_hash, *new_hash;
+	struct trace_parser *parser;
 
 	if (!cnt)
 		return 0;
 
-	if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX))
-		return -ENOMEM;
-
 	/* Read mode uses seq functions */
 	if (file->f_mode & FMODE_READ) {
 		struct seq_file *m = file->private_data;
 		fgd = m->private;
 	}
 
-	read = trace_get_user(&parser, ubuf, cnt, ppos);
+	parser = &fgd->parser;
 
-	if (read >= 0 && trace_parser_loaded((&parser))) {
-		parser.buffer[parser.idx] = 0;
+	read = trace_get_user(parser, ubuf, cnt, ppos);
 
-		mutex_lock(&graph_lock);
+	if (read >= 0 && trace_parser_loaded(parser) &&
+	    !trace_parser_cont(parser)) {
 
-		/* we allow only one expression at a time */
 		ret = ftrace_graph_set_hash(fgd->new_hash,
-					    parser.buffer);
-
-		new_hash = __ftrace_hash_move(fgd->new_hash);
-		if (!new_hash)
-			ret = -ENOMEM;
-
-		if (fgd->type == GRAPH_FILTER_FUNCTION) {
-			old_hash = rcu_dereference_protected(ftrace_graph_hash,
-					lockdep_is_held(&graph_lock));
-			rcu_assign_pointer(ftrace_graph_hash, new_hash);
-		} else {
-			old_hash = rcu_dereference_protected(ftrace_graph_notrace_hash,
-					lockdep_is_held(&graph_lock));
-			rcu_assign_pointer(ftrace_graph_notrace_hash, new_hash);
-		}
-
-		mutex_unlock(&graph_lock);
-
-		/* Wait till all users are no longer using the old hash */
-		synchronize_sched();
-
-		free_ftrace_hash(old_hash);
+					    parser->buffer);
+		trace_parser_clear(parser);
 	}
 
 	if (!ret)
 		ret = read;
 
-	trace_parser_put(&parser);
-
 	return ret;
 }