Merge tag 'tracefs-v7.1-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracefs updates from Steven Rostedt:

 - Simplify error handling with guards()

   Use guards() to simplify the handling of releasing locks in exit
   paths.

 - Use dentry name snapshots instead of allocation

   Instead of allocating a temp buffer to store the dentry name to use
   in mkdir() and rmdir() use take_dentry_name_snapshot().

 - Fix default permissions not being applied at boot

   The default permissions for tracefs was 0700 to only allow root
   having access. But after a change to fix other mount options the
   update to permissions ignored the defined default and used the system
   default of 0755. This is a regression and is fixed.

* tag 'tracefs-v7.1-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracefs: Removed unused 'ret' variable in eventfs_iterate()
  tracefs: Fix default permissions not being applied on initial mount
  tracefs: Use dentry name snapshots instead of heap allocation
  eventfs: Simplify code using guard()s

Author: torvalds

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;
 }
 
 /*
@@ -584,8 +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;
 
@@ -598,22 +586,18 @@ 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
 	 * inode number.
 	 */
-	ret = 0;
 
 	/* Start at 'c' to jump over already read entries */
 	for (i = c; i < ei->nr_entries; i++, ctx->pos++) {
@@ -622,21 +606,19 @@ 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 +641,13 @@ 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 +704,10 @@ 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 +853,8 @@ 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);
 }
 
 /**

fs/tracefs/inode.c

@@ -94,33 +94,14 @@ static struct tracefs_dir_ops {
 	int (*rmdir)(const char *name);
 } tracefs_ops __ro_after_init;
 
-static char *get_dname(struct dentry *dentry)
-{
-	const char *dname;
-	char *name;
-	int len = dentry->d_name.len;
-
-	dname = dentry->d_name.name;
-	name = kmalloc(len + 1, GFP_KERNEL);
-	if (!name)
-		return NULL;
-	memcpy(name, dname, len);
-	name[len] = 0;
-	return name;
-}
-
 static struct dentry *tracefs_syscall_mkdir(struct mnt_idmap *idmap,
 					    struct inode *inode, struct dentry *dentry,
 					    umode_t mode)
 {
 	struct tracefs_inode *ti;
-	char *name;
+	struct name_snapshot name;
 	int ret;
 
-	name = get_dname(dentry);
-	if (!name)
-		return ERR_PTR(-ENOMEM);
-
 	/*
 	 * This is a new directory that does not take the default of
 	 * the rootfs. It becomes the default permissions for all the
@@ -135,40 +116,36 @@ static struct dentry *tracefs_syscall_mkdir(struct mnt_idmap *idmap,
 	 * the files within the tracefs system. It is up to the individual
 	 * mkdir routine to handle races.
 	 */
+	take_dentry_name_snapshot(&name, dentry);
 	inode_unlock(inode);
-	ret = tracefs_ops.mkdir(name);
+	ret = tracefs_ops.mkdir(name.name.name);
 	inode_lock(inode);
-
-	kfree(name);
+	release_dentry_name_snapshot(&name);
 
 	return ERR_PTR(ret);
 }
 
 static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
 {
-	char *name;
+	struct name_snapshot name;
 	int ret;
 
-	name = get_dname(dentry);
-	if (!name)
-		return -ENOMEM;
-
 	/*
 	 * The rmdir call can call the generic functions that create
 	 * the files within the tracefs system. It is up to the individual
 	 * rmdir routine to handle races.
 	 * This time we need to unlock not only the parent (inode) but
 	 * also the directory that is being deleted.
 	 */
+	take_dentry_name_snapshot(&name, dentry);
 	inode_unlock(inode);
 	inode_unlock(d_inode(dentry));
 
-	ret = tracefs_ops.rmdir(name);
+	ret = tracefs_ops.rmdir(name.name.name);
 
 	inode_lock_nested(inode, I_MUTEX_PARENT);
 	inode_lock(d_inode(dentry));
-
-	kfree(name);
+	release_dentry_name_snapshot(&name);
 
 	return ret;
 }
@@ -491,6 +468,7 @@ static int tracefs_fill_super(struct super_block *sb, struct fs_context *fc)
 		return err;
 
 	sb->s_op = &tracefs_super_operations;
+	tracefs_apply_options(sb, false);
 	set_default_d_op(sb, &tracefs_dentry_operations);
 
 	return 0;