From 1b2cb2b3f048a68ee632bc586642e3bc86e6bbe4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dag-Erling=20Sm=C3=B8rgrav?= <des@FreeBSD.org>
Date: Tue, 24 Sep 2013 20:05:16 +0000
Subject: [PATCH] Introduce a kern.geom.notaste sysctl that can be used to
 temporarily disable GEOM tasting to avoid the "bouncing GEOM" problem where,
 when you shut down the consumer of a provider which can be viewed in multiple
 ways (typically a mirror whose members are labeled partitions), GEOM will
 immediately taste that provider's alter ego and reattach the consumer.

Approved by:	re (glebius)
---
 sys/geom/geom_int.h  | 1 +
 sys/geom/geom_kern.c | 4 ++++
 sys/geom/geom_subr.c | 4 +++-
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/sys/geom/geom_int.h b/sys/geom/geom_int.h
index 0a827affc44..149a283c656 100644
--- a/sys/geom/geom_int.h
+++ b/sys/geom/geom_int.h
@@ -75,6 +75,7 @@ void g_io_schedule_up(struct thread *tp);
 /* geom_kern.c / geom_kernsim.c */
 void g_init(void);
 extern int g_shutdown;
+extern int g_notaste;
 
 /* geom_ctl.c */
 void g_ctl_init(void);
diff --git a/sys/geom/geom_kern.c b/sys/geom/geom_kern.c
index 1744d170160..2e65bfbcd9b 100644
--- a/sys/geom/geom_kern.c
+++ b/sys/geom/geom_kern.c
@@ -66,6 +66,7 @@ static struct thread *g_event_td;
 int g_debugflags;
 int g_collectstats = 1;
 int g_shutdown;
+int g_notaste;
 
 /*
  * G_UP and G_DOWN are the two threads which push I/O through the
@@ -208,6 +209,9 @@ TUNABLE_INT("kern.geom.debugflags", &g_debugflags);
 SYSCTL_INT(_kern_geom, OID_AUTO, debugflags, CTLFLAG_RW,
 	&g_debugflags, 0, "Set various trace levels for GEOM debugging");
 
+SYSCTL_INT(_kern_geom, OID_AUTO, notaste, CTLFLAG_RW,
+	&g_notaste, 0, "Prevent GEOM tasting");
+
 SYSCTL_INT(_kern_geom, OID_AUTO, collectstats, CTLFLAG_RW,
 	&g_collectstats, 0,
 	"Control statistics collection on GEOM providers and consumers");
diff --git a/sys/geom/geom_subr.c b/sys/geom/geom_subr.c
index 316e66635fe..ecbf0b811d9 100644
--- a/sys/geom/geom_subr.c
+++ b/sys/geom/geom_subr.c
@@ -271,7 +271,7 @@ g_retaste_event(void *arg, int flag)
 	g_topology_assert();
 	if (flag == EV_CANCEL)  /* XXX: can't happen ? */
 		return;
-	if (g_shutdown)
+	if (g_shutdown || g_notaste)
 		return;
 
 	hh = arg;
@@ -540,6 +540,8 @@ g_new_provider_event(void *arg, int flag)
 		    cp->geom->attrchanged != NULL)
 			cp->geom->attrchanged(cp, "GEOM::media");
 	}
+	if (g_notaste)
+		return;
 	LIST_FOREACH(mp, &g_classes, class) {
 		if (mp->taste == NULL)
 			continue;