staging/lustre: Generic helpers for sysfs

Add generic helpers to allow displaying oof lustre-specific values
in /sys/fs/lustre
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/include/lprocfs_status.h

@@ -742,6 +742,27 @@ static struct file_operations name##_fops = {				\
 		.release = lprocfs_single_release,			\
 	}
 
+struct lustre_attr {
+	struct attribute attr;
+	ssize_t (*show)(struct kobject *kobj, struct attribute *attr,
+			char *buf);
+	ssize_t (*store)(struct kobject *kobj, struct attribute *attr,
+			 const char *buf, size_t len);
+};
+
+#define LUSTRE_ATTR(name, mode, show, store) \
+static struct lustre_attr lustre_attr_##name = __ATTR(name, mode, show, store)
+
+#define LUSTRE_RO_ATTR(name) LUSTRE_ATTR(name, 0444, name##_show, NULL)
+#define LUSTRE_RW_ATTR(name) LUSTRE_ATTR(name, 0644, name##_show, name##_store)
+
+ssize_t lustre_attr_show(struct kobject *kobj, struct attribute *attr,
+			 char *buf);
+ssize_t lustre_attr_store(struct kobject *kobj, struct attribute *attr,
+			  const char *buf, size_t len);
+
+extern const struct sysfs_ops lustre_sysfs_ops;
+
 /* lproc_ptlrpc.c */
 struct ptlrpc_request;
 extern void target_print_req(void *seq_file, struct ptlrpc_request *req);

drivers/staging/lustre/lustre/obdclass/lprocfs_status.c

@@ -2056,3 +2056,27 @@ int lprocfs_obd_rd_max_pages_per_rpc(struct seq_file *m, void *data)
 EXPORT_SYMBOL(lprocfs_obd_rd_max_pages_per_rpc);
 
 #endif
+
+ssize_t lustre_attr_show(struct kobject *kobj,
+			 struct attribute *attr, char *buf)
+{
+	struct lustre_attr *a = container_of(attr, struct lustre_attr, attr);
+
+	return a->show ? a->show(kobj, attr, buf) : 0;
+}
+EXPORT_SYMBOL_GPL(lustre_attr_show);
+
+ssize_t lustre_attr_store(struct kobject *kobj, struct attribute *attr,
+			  const char *buf, size_t len)
+{
+	struct lustre_attr *a = container_of(attr, struct lustre_attr, attr);
+
+	return a->store ? a->store(kobj, attr, buf, len) : len;
+}
+EXPORT_SYMBOL_GPL(lustre_attr_store);
+
+const struct sysfs_ops lustre_sysfs_ops = {
+	.show  = lustre_attr_show,
+	.store = lustre_attr_store,
+};
+EXPORT_SYMBOL_GPL(lustre_sysfs_ops);