From a2f1945ee3ce8eba02ef54168c72f3be8f2cebdc Mon Sep 17 00:00:00 2001
From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Fri, 22 Nov 2013 11:20:41 -0800
Subject: [PATCH] Add a unique "eid" value to all zevents

Tagging each zevent with a unique monotonically increasing EID
(Event IDentifier) provides the required infrastructure for a user
space daemon to reliably process zevents.  By writing the EID to
persistent storage the daemon can safely resume where it left off
in the event stream when it's restarted.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Issue #2
---
 include/sys/fm/protocol.h |  1 +
 include/sys/fm/util.h     |  1 +
 module/zfs/fm.c           | 16 ++++++++++++++++
 3 files changed, 18 insertions(+)

diff --git a/include/sys/fm/protocol.h b/include/sys/fm/protocol.h
index 1ee221286c..de05bb2967 100644
--- a/include/sys/fm/protocol.h
+++ b/include/sys/fm/protocol.h
@@ -70,6 +70,7 @@ extern "C" {
 #define	FM_EREPORT_DETECTOR		"detector"
 #define	FM_EREPORT_ENA			"ena"
 #define	FM_EREPORT_TIME			"time"
+#define	FM_EREPORT_EID			"eid"
 
 /* list.* event payload member names */
 #define	FM_LIST_EVENT_SIZE		"list-sz"
diff --git a/include/sys/fm/util.h b/include/sys/fm/util.h
index 2f03d1011a..9dfd436c1b 100644
--- a/include/sys/fm/util.h
+++ b/include/sys/fm/util.h
@@ -81,6 +81,7 @@ typedef struct zevent_s {
 	list_t		ev_ze_list;	/* " */
 	list_node_t	ev_node;	/* " */
 	zevent_cb_t	*ev_cb;		/* " */
+	uint64_t	ev_eid;
 } zevent_t;
 
 typedef struct zfs_zevent {
diff --git a/module/zfs/fm.c b/module/zfs/fm.c
index 002827b520..fe9223ff81 100644
--- a/module/zfs/fm.c
+++ b/module/zfs/fm.c
@@ -84,6 +84,14 @@ static int zevent_len_cur = 0;
 static int zevent_waiters = 0;
 static int zevent_flags = 0;
 
+/*
+ * The EID (Event IDentifier) is used to uniquely tag a zevent when it is
+ * posted.  The posted EIDs are monotonically increasing but not persistent.
+ * They will be reset to the initial value (1) each time the kernel module is
+ * loaded.
+ */
+static uint64_t zevent_eid = 0;
+
 static kmutex_t zevent_lock;
 static list_t zevent_list;
 static kcondvar_t zevent_cv;
@@ -498,6 +506,7 @@ zfs_zevent_post(nvlist_t *nvl, nvlist_t *detector, zevent_cb_t *cb)
 {
 	int64_t tv_array[2];
 	timestruc_t tv;
+	uint64_t eid;
 	size_t nvl_size = 0;
 	zevent_t *ev;
 
@@ -509,6 +518,12 @@ zfs_zevent_post(nvlist_t *nvl, nvlist_t *detector, zevent_cb_t *cb)
 		return;
 	}
 
+	eid = atomic_inc_64_nv(&zevent_eid);
+	if (nvlist_add_uint64(nvl, FM_EREPORT_EID, eid)) {
+		atomic_add_64(&erpt_kstat_data.erpt_set_failed.value.ui64, 1);
+		return;
+	}
+
 	(void) nvlist_size(nvl, &nvl_size, NV_ENCODE_NATIVE);
 	if (nvl_size > ERPT_DATA_SZ || nvl_size == 0) {
 		atomic_add_64(&erpt_kstat_data.erpt_dropped.value.ui64, 1);
@@ -527,6 +542,7 @@ zfs_zevent_post(nvlist_t *nvl, nvlist_t *detector, zevent_cb_t *cb)
 	ev->ev_nvl = nvl;
 	ev->ev_detector = detector;
 	ev->ev_cb = cb;
+	ev->ev_eid = eid;
 
 	mutex_enter(&zevent_lock);
 	zfs_zevent_insert(ev);