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Date:      Sun, 22 Sep 2013 01:47:17 +0200
From:      =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no>
To:        geom@freebsd.org
Subject:   Disable tasting through sysctl
Message-ID:  <86fvsxd9fe.fsf@nine.des.no>
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The patch below is a workaround for the "bouncing geom" problem that
occurs primarily with labels.  Say da0p1 and da1p1 are labeled "mir0"
and "mir1" respectively, so they exist both as /dev/da[01]p1 and as
/dev/gpt/mir[01].  Create a mirror on top of gpt/mir[01], then stop the
mirror.  GEOM won't retaste gpt/root[01], but it will see and taste
da[01]p1, and the mirror will immediately reappear.  The patch adds a
sysctl which can be used to temporarily disable tasting so you can stop
the mirror and safely disconnect the disks.

DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@des.no

Index: sys/geom/geom_int.h
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- sys/geom/geom_int.h	(revision 255780)
+++ sys/geom/geom_int.h	(working copy)
@@ -75,6 +75,7 @@
 /* geom_kern.c / geom_kernsim.c */
 void g_init(void);
 extern int g_shutdown;
+extern int g_notaste;
=20
 /* geom_ctl.c */
 void g_ctl_init(void);
Index: sys/geom/geom_kern.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- sys/geom/geom_kern.c	(revision 255780)
+++ sys/geom/geom_kern.c	(working copy)
@@ -66,6 +66,7 @@
 int g_debugflags;
 int g_collectstats =3D 1;
 int g_shutdown;
+int g_notaste;
=20
 /*
  * G_UP and G_DOWN are the two threads which push I/O through the
@@ -208,6 +209,9 @@
 SYSCTL_INT(_kern_geom, OID_AUTO, debugflags, CTLFLAG_RW,
 	&g_debugflags, 0, "Set various trace levels for GEOM debugging");
=20
+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");
Index: sys/geom/geom_subr.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- sys/geom/geom_subr.c	(revision 255780)
+++ sys/geom/geom_subr.c	(working copy)
@@ -271,7 +271,7 @@
 	g_topology_assert();
 	if (flag =3D=3D EV_CANCEL)  /* XXX: can't happen ? */
 		return;
-	if (g_shutdown)
+	if (g_shutdown || g_notaste)
 		return;
=20
 	hh =3D arg;
@@ -540,6 +540,8 @@
 		    cp->geom->attrchanged !=3D NULL)
 			cp->geom->attrchanged(cp, "GEOM::media");
 	}
+	if (g_notaste)
+		return;
 	LIST_FOREACH(mp, &g_classes, class) {
 		if (mp->taste =3D=3D NULL)
 			continue;

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