Illumos #3537

3537 want pool io kstats

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Sa?o Kiselkov <skiselkov.ml@gmail.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Reviewed by: Brendan Gregg <brendan.gregg@joyent.com>
Approved by: Gordon Ross <gwr@nexenta.com>

References:
  http://www.illumos.org/issues/3537
  illumos/illumos-gate@c3a6601

Ported by: Cyril Plisko <cyril.plisko@mountall.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

Porting Notes:

1. The patch was restructured to take advantage of the existing
   spa statistics infrastructure.  To accomplish this the kstat
   was moved in to spa->io_stats and the init/destroy code moved
   to spa_stats.c.

2. The I/O kstat was simply named <pool> which conflicted with the
   pool directory we had already created.  Therefore it was renamed
   to <pool>/io

3. An update handler was added to allow the kstat to be zeroed.

lib/libzpool/kernel.c

@@ -224,8 +224,8 @@ zk_thread_join(kt_did_t tid)
  */
 /*ARGSUSED*/
 kstat_t *
-kstat_create(char *module, int instance, char *name, char *class,
-    uchar_t type, ulong_t ndata, uchar_t ks_flag)
+kstat_create(const char *module, int instance, const char *name,
+    const char *class, uchar_t type, ulong_t ndata, uchar_t ks_flag)
 {
 	return (NULL);
 }
@@ -241,6 +241,35 @@ kstat_delete(kstat_t *ksp)
 {}
 
 /*ARGSUSED*/
+void
+kstat_waitq_enter(kstat_io_t *kiop)
+{}
+
+/*ARGSUSED*/
+void
+kstat_waitq_exit(kstat_io_t *kiop)
+{}
+
+/*ARGSUSED*/
+void
+kstat_runq_enter(kstat_io_t *kiop)
+{}
+
+/*ARGSUSED*/
+void
+kstat_runq_exit(kstat_io_t *kiop)
+{}
+
+/*ARGSUSED*/
+void
+kstat_waitq_to_runq(kstat_io_t *kiop)
+{}
+
+/*ARGSUSED*/
+void
+kstat_runq_back_to_waitq(kstat_io_t *kiop)
+{}
+
 void
 kstat_set_raw_ops(kstat_t *ksp,
     int (*headers)(char *buf, size_t size),