From 64dbba36794422aaed5177203edd0dd7aee77de7 Mon Sep 17 00:00:00 2001
From: Adam Leventhal <adam.leventhal@delphix.com>
Date: Wed, 17 Sep 2014 08:53:02 +0200
Subject: [PATCH] Illumos 5174 - add sdt probe for blocked read in dbuf_read()

5174 add sdt probe for blocked read in dbuf_read()
Reviewed by: Basil Crow <basil.crow@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Steven Hartland <killing@multiplay.co.uk>
Reviewed by: Richard Elling <richard.elling@gmail.com>
Reviewed by: Boris Protopopov <bprotopopov@hotmail.com>
Reviewed by: Steven Hartland <killing@multiplay.co.uk>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Approved by: Robert Mustacchi <rm@joyent.com>

References:
  https://www.illumos.org/issues/5174
  https://github.com/illumos/illumos-gate/commit/f6164ad

Ported by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2710
---
 module/zfs/dbuf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index 7f75e131f..76a8a99ab 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -726,6 +726,8 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
 			    db->db_state == DB_FILL) {
 				ASSERT(db->db_state == DB_READ ||
 				    (flags & DB_RF_HAVESTRUCT) == 0);
+				DTRACE_PROBE2(blocked__read, dmu_buf_impl_t *,
+				    db, zio_t *, zio);
 				cv_wait(&db->db_changed, &db->db_mtx);
 			}
 			if (db->db_state == DB_UNCACHED)