Re: [RFC PATCH 1/7] core/metricfs: Create metricfs, standardized files under debugfs.

debugfs interaction nits:

On Fri, Aug 07, 2020 at 02:29:10PM -0700, Jonathan Adams wrote:

+static struct dentry *metricfs_init_dentry(void)
+{
+	static int once;
+
+	if (d_metricfs)
+		return d_metricfs;
+
+	if (!debugfs_initialized())
+		return NULL;
+
+	d_metricfs = debugfs_create_dir("metricfs", NULL);
+
+	if (!d_metricfs && !once) {

As it is impossible for d_metricfs to ever be NULL, why are you checking
it?

+		once = 1;
+		pr_warn("Could not create debugfs directory 'metricfs'\n");

There is a pr_warn_once I think, but again, how can this ever trigger?

+		return NULL;
+	}
+
+	return d_metricfs;
+}
+
+/* We always cast in and out to struct dentry. */
+struct metricfs_subsys {
+	struct dentry dentry;
+};
+
+static struct dentry *metricfs_create_file(const char *name,
+					   mode_t mode,
+					   struct dentry *parent,
+					   void *data,
+					   const struct file_operations *fops)
+{
+	struct dentry *ret;
+
+	ret = debugfs_create_file(name, mode, parent, data, fops);
+	if (!ret)
+		pr_warn("Could not create debugfs '%s' entry\n", name);

As ret can never be NULL, why check?

There is no need to ever check debugfs return values, just keep on
going, that's the design of it.

thanks,

greg k-h