eventfs: Simplify code using guard()s

Use guard(mutex), scoped_guard(mutex) and guard(src) to simplify the code
and remove a lot of the jumps to "out:" labels.

Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250604151625.250d13e1@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Author: rostedt

fs/tracefs/event_inode.c

@@ -180,29 +180,25 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
 	const char *name;
 	int ret;
 
-	mutex_lock(&eventfs_mutex);
+	guard(mutex)(&eventfs_mutex);
 	ei = dentry->d_fsdata;
-	if (ei->is_freed) {
-		/* Do not allow changes if the event is about to be removed. */
-		mutex_unlock(&eventfs_mutex);
+	/* Do not allow changes if the event is about to be removed. */
+	if (ei->is_freed)
 		return -ENODEV;
-	}
 
 	/* Preallocate the children mode array if necessary */
 	if (!(dentry->d_inode->i_mode & S_IFDIR)) {
 		if (!ei->entry_attrs) {
 			ei->entry_attrs = kzalloc_objs(*ei->entry_attrs,
 						       ei->nr_entries, GFP_NOFS);
-			if (!ei->entry_attrs) {
-				ret = -ENOMEM;
-				goto out;
-			}
+			if (!ei->entry_attrs)
+				return -ENOMEM;
 		}
 	}
 
 	ret = simple_setattr(idmap, dentry, iattr);
 	if (ret < 0)
-		goto out;
+		return ret;
 
 	/*
 	 * If this is a dir, then update the ei cache, only the file
@@ -225,8 +221,6 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
 			}
 		}
 	}
- out:
-	mutex_unlock(&eventfs_mutex);
 	return ret;
 }
 
@@ -528,26 +522,24 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
 	struct tracefs_inode *ti;
 	struct eventfs_inode *ei;
 	const char *name = dentry->d_name.name;
-	struct dentry *result = NULL;
 
 	ti = get_tracefs(dir);
 	if (WARN_ON_ONCE(!(ti->flags & TRACEFS_EVENT_INODE)))
 		return ERR_PTR(-EIO);
 
-	mutex_lock(&eventfs_mutex);
+	guard(mutex)(&eventfs_mutex);
 
 	ei = ti->private;
 	if (!ei || ei->is_freed)
-		goto out;
+		return NULL;
 
 	list_for_each_entry(ei_child, &ei->children, list) {
 		if (strcmp(ei_child->name, name) != 0)
 			continue;
 		/* A child is freed and removed from the list at the same time */
 		if (WARN_ON_ONCE(ei_child->is_freed))
-			goto out;
-		result = lookup_dir_entry(dentry, ei, ei_child);
-		goto out;
+			return NULL;
+		return lookup_dir_entry(dentry, ei, ei_child);
 	}
 
 	for (int i = 0; i < ei->nr_entries; i++) {
@@ -561,14 +553,12 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
 
 		data = ei->data;
 		if (entry->callback(name, &mode, &data, &fops) <= 0)
-			goto out;
+			return NULL;
+
+		return lookup_file_dentry(dentry, ei, i, mode, data, fops);
 
-		result = lookup_file_dentry(dentry, ei, i, mode, data, fops);
-		goto out;
 	}
- out:
-	mutex_unlock(&eventfs_mutex);
-	return result;
+	return NULL;
 }
 
 /*
@@ -584,7 +574,6 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)
 	struct eventfs_inode *ei;
 	const char *name;
 	umode_t mode;
-	int idx;
 	int ret = -EINVAL;
 	int ino;
 	int i, r, c;
@@ -598,16 +587,13 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)
 
 	c = ctx->pos - 2;
 
-	idx = srcu_read_lock(&eventfs_srcu);
+	guard(srcu)(&eventfs_srcu);
 
-	mutex_lock(&eventfs_mutex);
-	ei = READ_ONCE(ti->private);
-	if (ei && ei->is_freed)
-		ei = NULL;
-	mutex_unlock(&eventfs_mutex);
-
-	if (!ei)
-		goto out;
+	scoped_guard(mutex, &eventfs_mutex) {
+		ei = READ_ONCE(ti->private);
+		if (!ei || ei->is_freed)
+			return -EINVAL;
+	}
 
 	/*
 	 * Need to create the dentries and inodes to have a consistent
@@ -622,21 +608,19 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)
 		entry = &ei->entries[i];
 		name = entry->name;
 
-		mutex_lock(&eventfs_mutex);
 		/* If ei->is_freed then just bail here, nothing more to do */
-		if (ei->is_freed) {
-			mutex_unlock(&eventfs_mutex);
-			goto out;
+		scoped_guard(mutex, &eventfs_mutex) {
+			if (ei->is_freed)
+				return -EINVAL;
+			r = entry->callback(name, &mode, &cdata, &fops);
 		}
-		r = entry->callback(name, &mode, &cdata, &fops);
-		mutex_unlock(&eventfs_mutex);
 		if (r <= 0)
 			continue;
 
 		ino = EVENTFS_FILE_INODE_INO;
 
 		if (!dir_emit(ctx, name, strlen(name), ino, DT_REG))
-			goto out;
+			return -EINVAL;
 	}
 
 	/* Subtract the skipped entries above */
@@ -659,19 +643,13 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)
 
 		ino = eventfs_dir_ino(ei_child);
 
-		if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR))
-			goto out_dec;
+		if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR)) {
+			/* Incremented ctx->pos without adding something, reset it */
+			ctx->pos--;
+			return -EINVAL;
+		}
 	}
-	ret = 1;
- out:
-	srcu_read_unlock(&eventfs_srcu, idx);
-
-	return ret;
-
- out_dec:
-	/* Incremented ctx->pos without adding something, reset it */
-	ctx->pos--;
-	goto out;
+	return 1;
 }
 
 /**
@@ -728,11 +706,10 @@ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode
 	INIT_LIST_HEAD(&ei->children);
 	INIT_LIST_HEAD(&ei->list);
 
-	mutex_lock(&eventfs_mutex);
-	if (!parent->is_freed)
-		list_add_tail(&ei->list, &parent->children);
-	mutex_unlock(&eventfs_mutex);
-
+	scoped_guard(mutex, &eventfs_mutex) {
+		if (!parent->is_freed)
+			list_add_tail(&ei->list, &parent->children);
+	}
 	/* Was the parent freed? */
 	if (list_empty(&ei->list)) {
 		cleanup_ei(ei);
@@ -878,9 +855,8 @@ void eventfs_remove_dir(struct eventfs_inode *ei)
 	if (!ei)
 		return;
 
-	mutex_lock(&eventfs_mutex);
+	guard(mutex)(&eventfs_mutex);
 	eventfs_remove_rec(ei, 0);
-	mutex_unlock(&eventfs_mutex);
 }
 
 /**