ubifs: Remove obsolete TODO from dfs_file_write()

AFAICT this kind of problems are no longer possible since
debugfs gained file removal protection via
e9117a5a ("debugfs: implement per-file removal protection").

Cc: Christoph Hellwig <hch@lst.de>
Cc: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

fs/ubifs/debug.c

@@ -2737,18 +2737,6 @@ static ssize_t dfs_file_write(struct file *file, const char __user *u,
 	struct dentry *dent = file->f_path.dentry;
 	int val;
 
-	/*
-	 * TODO: this is racy - the file-system might have already been
-	 * unmounted and we'd oops in this case. The plan is to fix it with
-	 * help of 'iterate_supers_type()' which we should have in v3.0: when
-	 * a debugfs opened, we rember FS's UUID in file->private_data. Then
-	 * whenever we access the FS via a debugfs file, we iterate all UBIFS
-	 * superblocks and fine the one with the same UUID, and take the
-	 * locking right.
-	 *
-	 * The other way to go suggested by Al Viro is to create a separate
-	 * 'ubifs-debug' file-system instead.
-	 */
 	if (file->f_path.dentry == d->dfs_dump_lprops) {
 		ubifs_dump_lprops(c);
 		return count;