idr: Add new function idr_is_empty()

Signed-off-by: Andreas Gruenbacher <[e-mail]>
Signed-off-by: Philipp Reisner <[e-mail]>

include/linux/idr.h

···
 void idr_free(struct idr *idp, int id);
 void idr_destroy(struct idr *idp);
 void idr_init(struct idr *idp);
+bool idr_is_empty(struct idr *idp);
 
 /**
  * idr_preload_end - end preload section started with idr_preload()

lib/idr.c

···
 }
 EXPORT_SYMBOL(idr_init);
 
+static int idr_has_entry(int id, void *p, void *data)
+{
+	return 1;
+}
+
+bool idr_is_empty(struct idr *idp)
+{
+	return !idr_for_each(idp, idr_has_entry, NULL);
+}
+EXPORT_SYMBOL(idr_is_empty);
 
 /**
  * DOC: IDA description