Inject zinject(8) a percentage amount of dev errs

In the original form of device error injection, it was an all or nothing
situation.  To help simulate intermittent error conditions, you can now
specify a real number percentage value. This is also very useful for our
ZFS fault diagnosis testing and for injecting intermittent errors during
load testing.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Don Brady <don.brady@intel.com>
Closes #6227

include/sys/zfs_ioctl.h

@@ -22,6 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
  * Copyright 2016 RackTop Systems.
+ * Copyright (c) 2017, Intel Corporation.
  */
 
 #ifndef	_SYS_ZFS_IOCTL_H
@@ -338,6 +339,10 @@ typedef struct zinject_record {
 #define	ZEVENT_SEEK_START	0
 #define	ZEVENT_SEEK_END		UINT64_MAX
 
+/* scaled frequency ranges */
+#define	ZI_PERCENTAGE_MIN	4294UL
+#define	ZI_PERCENTAGE_MAX	UINT32_MAX
+
 typedef enum zinject_type {
 	ZINJECT_UNINITIALIZED,
 	ZINJECT_DATA_FAULT,