[v6.6][PATCH 01/57] Revert "eventfs: Do not allow NULL parent to eventfs_start_creating()"

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>

This reverts commit 6abb8c223ce12078a0f2c129656a13338dfe960b.

The eventfs was not designed properly and may have some hidden bugs in it.
Linus rewrote it properly and I trust his version more than this one. Revert
the backported patches for 6.6 and re-apply all the changes to make it
equivalent to Linus's version.

Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
 fs/tracefs/inode.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 0292c6a2bed9..891653ba9cf3 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -509,15 +509,20 @@ struct dentry *eventfs_start_creating(const char *name, struct dentry *parent)
 	struct dentry *dentry;
 	int error;
 
-	/* Must always have a parent. */
-	if (WARN_ON_ONCE(!parent))
-		return ERR_PTR(-EINVAL);
-
 	error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
 			      &tracefs_mount_count);
 	if (error)
 		return ERR_PTR(error);
 
+	/*
+	 * If the parent is not specified, we create it in the root.
+	 * We need the root dentry to do this, which is in the super
+	 * block. A pointer to that is in the struct vfsmount that we
+	 * have around.
+	 */
+	if (!parent)
+		parent = tracefs_mount->mnt_root;
+
 	if (unlikely(IS_DEADDIR(parent->d_inode)))
 		dentry = ERR_PTR(-ENOENT);
 	else
-- 
2.43.0