Add gmountver, disk mount verification GEOM class.

Note that due to e.g. write throttling ('wdrain'), it can stall all the disk
I/O instead of just the device it's configured for.  Using it for removable
media is therefore not a good idea.

Reviewed by:	pjd (earlier version)

2 files changed, 717 insertions, 0 deletions

diff --git a/sys/geom/mountver/g_mountver.c b/sys/geom/mountver/g_mountver.c
new file mode 100644
index 0000000..8640712
--- /dev/null
+++ b/sys/geom/mountver/g_mountver.c
@@ -0,0 +1,646 @@
+/*-
+ * Copyright (c) 2010 Edward Tomasz Napierala <trasz@FreeBSD.org>
+ * Copyright (c) 2004-2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/bio.h>
+#include <sys/disk.h>
+#include <sys/sysctl.h>
+#include <sys/malloc.h>
+#include <sys/eventhandler.h>
+#include <geom/geom.h>
+#include <geom/mountver/g_mountver.h>
+
+
+SYSCTL_DECL(_kern_geom);
+SYSCTL_NODE(_kern_geom, OID_AUTO, mountver, CTLFLAG_RW,
+    0, "GEOM_MOUNTVER stuff");
+static u_int g_mountver_debug = 0;
+static u_int g_mountver_check_ident = 1;
+SYSCTL_UINT(_kern_geom_mountver, OID_AUTO, debug, CTLFLAG_RW,
+    &g_mountver_debug, 0, "Debug level");
+SYSCTL_UINT(_kern_geom_mountver, OID_AUTO, check_ident, CTLFLAG_RW,
+    &g_mountver_check_ident, 0, "Check disk ident when reattaching");
+
+static eventhandler_tag g_mountver_pre_sync = NULL;
+
+static void g_mountver_queue(struct bio *bp);
+static void g_mountver_orphan(struct g_consumer *cp);
+static int g_mountver_destroy(struct g_geom *gp, boolean_t force);
+static g_taste_t g_mountver_taste;
+static int g_mountver_destroy_geom(struct gctl_req *req, struct g_class *mp,
+    struct g_geom *gp);
+static void g_mountver_config(struct gctl_req *req, struct g_class *mp,
+    const char *verb);
+static void g_mountver_dumpconf(struct sbuf *sb, const char *indent,
+    struct g_geom *gp, struct g_consumer *cp, struct g_provider *pp);
+static void g_mountver_init(struct g_class *mp);
+static void g_mountver_fini(struct g_class *mp);
+
+struct g_class g_mountver_class = {
+	.name = G_MOUNTVER_CLASS_NAME,
+	.version = G_VERSION,
+	.ctlreq = g_mountver_config,
+	.taste = g_mountver_taste,
+	.destroy_geom = g_mountver_destroy_geom,
+	.init = g_mountver_init,
+	.fini = g_mountver_fini
+};
+
+static void
+g_mountver_done(struct bio *bp)
+{
+	struct g_mountver_softc *sc;
+	struct g_geom *gp;
+	struct bio *pbp;
+
+	if (bp->bio_error != ENXIO) {
+		g_std_done(bp);
+		return;
+	}
+
+	/*
+	 * When the device goes away, it's possible that few requests
+	 * will be completed with ENXIO before g_mountver_orphan()
+	 * gets called.  To work around that, we have to queue requests
+	 * that failed with ENXIO, in order to send them later.
+	 */
+	gp = bp->bio_from->geom;
+	sc = gp->softc;
+
+	pbp = bp->bio_parent;
+	KASSERT(pbp->bio_to == LIST_FIRST(&gp->provider),
+	    ("parent request was for someone else"));
+	g_destroy_bio(bp);
+	pbp->bio_inbed++;
+	g_mountver_queue(pbp);
+}
+
+static void
+g_mountver_send(struct bio *bp)
+{
+	struct g_geom *gp;
+	struct bio *cbp;
+
+	gp = bp->bio_to->geom;
+
+	cbp = g_clone_bio(bp);
+	if (cbp == NULL) {
+		g_io_deliver(bp, ENOMEM);
+		return;
+	}
+
+	cbp->bio_done = g_mountver_done;
+	g_io_request(cbp, LIST_FIRST(&gp->consumer));
+}
+
+static void
+g_mountver_queue(struct bio *bp)
+{
+	struct g_mountver_softc *sc;
+	struct g_geom *gp;
+
+	gp = bp->bio_to->geom;
+	sc = gp->softc;
+
+	mtx_lock(&sc->sc_mtx);
+	TAILQ_INSERT_TAIL(&sc->sc_queue, bp, bio_queue);
+	mtx_unlock(&sc->sc_mtx);
+}
+
+static void
+g_mountver_send_queued(struct g_geom *gp)
+{
+	struct g_mountver_softc *sc;
+	struct bio *bp;
+
+	sc = gp->softc;
+
+	mtx_lock(&sc->sc_mtx);
+	while ((bp = TAILQ_FIRST(&sc->sc_queue)) != NULL) {
+		TAILQ_REMOVE(&sc->sc_queue, bp, bio_queue);
+		G_MOUNTVER_LOGREQ(bp, "Sending queued request.");
+		g_mountver_send(bp);
+	}
+	mtx_unlock(&sc->sc_mtx);
+}
+
+static void
+g_mountver_discard_queued(struct g_geom *gp)
+{
+	struct g_mountver_softc *sc;
+	struct bio *bp;
+
+	sc = gp->softc;
+
+	mtx_lock(&sc->sc_mtx);
+	while ((bp = TAILQ_FIRST(&sc->sc_queue)) != NULL) {
+		TAILQ_REMOVE(&sc->sc_queue, bp, bio_queue);
+		G_MOUNTVER_LOGREQ(bp, "Discarding queued request.");
+		g_io_deliver(bp, ENXIO);
+	}
+	mtx_unlock(&sc->sc_mtx);
+}
+
+static void
+g_mountver_start(struct bio *bp)
+{
+	struct g_mountver_softc *sc;
+	struct g_geom *gp;
+
+	gp = bp->bio_to->geom;
+	sc = gp->softc;
+	G_MOUNTVER_LOGREQ(bp, "Request received.");
+
+	/*
+	 * It is possible that some bios were returned with ENXIO, even though
+	 * orphaning didn't happen yet.  In that case, queue all subsequent
+	 * requests in order to maintain ordering.
+	 */
+	if (sc->sc_orphaned || !TAILQ_EMPTY(&sc->sc_queue)) {
+		G_MOUNTVER_LOGREQ(bp, "Queueing request.");
+		g_mountver_queue(bp);
+		if (!sc->sc_orphaned)
+			g_mountver_send_queued(gp);
+	} else {
+		G_MOUNTVER_LOGREQ(bp, "Sending request.");
+		g_mountver_send(bp);
+	}
+}
+
+static int
+g_mountver_access(struct g_provider *pp, int dr, int dw, int de)
+{
+	struct g_mountver_softc *sc;
+	struct g_geom *gp;
+	struct g_consumer *cp;
+
+	g_topology_assert();
+
+	gp = pp->geom;
+	cp = LIST_FIRST(&gp->consumer);
+	sc = gp->softc;
+	if (sc == NULL && dr <= 0 && dw <= 0 && de <= 0)
+		return (0);
+	KASSERT(sc != NULL, ("Trying to access withered provider \"%s\".", pp->name));
+
+	sc->sc_access_r += dr;
+	sc->sc_access_w += dw;
+	sc->sc_access_e += de;
+
+	if (sc->sc_orphaned)
+		return (0);
+
+	return (g_access(cp, dr, dw, de));
+}
+
+static int
+g_mountver_create(struct gctl_req *req, struct g_class *mp, struct g_provider *pp)
+{
+	struct g_mountver_softc *sc;
+	struct g_geom *gp;
+	struct g_provider *newpp;
+	struct g_consumer *cp;
+	char name[64];
+	int error;
+	int identsize = DISK_IDENT_SIZE;
+
+	g_topology_assert();
+
+	gp = NULL;
+	newpp = NULL;
+	cp = NULL;
+
+	snprintf(name, sizeof(name), "%s%s", pp->name, G_MOUNTVER_SUFFIX);
+	LIST_FOREACH(gp, &mp->geom, geom) {
+		if (strcmp(gp->name, name) == 0) {
+			gctl_error(req, "Provider %s already exists.", name);
+			return (EEXIST);
+		}
+	}
+	gp = g_new_geomf(mp, name);
+	if (gp == NULL) {
+		gctl_error(req, "Cannot create geom %s.", name);
+		return (ENOMEM);
+	}
+	sc = g_malloc(sizeof(*sc), M_WAITOK | M_ZERO);
+	mtx_init(&sc->sc_mtx, "gmountver", NULL, MTX_DEF);
+	TAILQ_INIT(&sc->sc_queue);
+	sc->sc_provider_name = strdup(pp->name, M_GEOM);
+	gp->softc = sc;
+	gp->start = g_mountver_start;
+	gp->orphan = g_mountver_orphan;
+	gp->access = g_mountver_access;
+	gp->dumpconf = g_mountver_dumpconf;
+
+	newpp = g_new_providerf(gp, gp->name);
+	if (newpp == NULL) {
+		gctl_error(req, "Cannot create provider %s.", name);
+		error = ENOMEM;
+		goto fail;
+	}
+	newpp->mediasize = pp->mediasize;
+	newpp->sectorsize = pp->sectorsize;
+
+	cp = g_new_consumer(gp);
+	if (cp == NULL) {
+		gctl_error(req, "Cannot create consumer for %s.", gp->name);
+		error = ENOMEM;
+		goto fail;
+	}
+	error = g_attach(cp, pp);
+	if (error != 0) {
+		gctl_error(req, "Cannot attach to provider %s.", pp->name);
+		goto fail;
+	}
+	error = g_access(cp, 1, 0, 0);
+	if (error != 0) {
+		gctl_error(req, "Cannot access provider %s.", pp->name);
+		goto fail;
+	}
+	error = g_io_getattr("GEOM::ident", cp, &identsize, sc->sc_ident);
+	g_access(cp, -1, 0, 0);
+	if (error != 0) {
+		if (g_mountver_check_ident) {
+			gctl_error(req, "Cannot get disk ident from %s; error = %d.", pp->name, error);
+			goto fail;
+		}
+
+		G_MOUNTVER_DEBUG(0, "Cannot get disk ident from %s; error = %d.", pp->name, error);
+		sc->sc_ident[0] = '\0';
+	}
+
+	g_error_provider(newpp, 0);
+	G_MOUNTVER_DEBUG(0, "Device %s created.", gp->name);
+	return (0);
+fail:
+	if (sc->sc_provider_name != NULL)
+		g_free(sc->sc_provider_name);
+	if (cp != NULL) {
+		if (cp->provider != NULL)
+			g_detach(cp);
+		g_destroy_consumer(cp);
+	}
+	if (newpp != NULL)
+		g_destroy_provider(newpp);
+	if (gp != NULL) {
+		if (gp->softc != NULL)
+			g_free(gp->softc);
+		g_destroy_geom(gp);
+	}
+	return (error);
+}
+
+static int
+g_mountver_destroy(struct g_geom *gp, boolean_t force)
+{
+	struct g_mountver_softc *sc;
+	struct g_provider *pp;
+
+	g_topology_assert();
+	if (gp->softc == NULL)
+		return (ENXIO);
+	sc = gp->softc;
+	pp = LIST_FIRST(&gp->provider);
+	if (pp != NULL && (pp->acr != 0 || pp->acw != 0 || pp->ace != 0)) {
+		if (force) {
+			G_MOUNTVER_DEBUG(0, "Device %s is still open, so it "
+			    "can't be definitely removed.", pp->name);
+		} else {
+			G_MOUNTVER_DEBUG(1, "Device %s is still open (r%dw%de%d).",
+			    pp->name, pp->acr, pp->acw, pp->ace);
+			return (EBUSY);
+		}
+	} else {
+		G_MOUNTVER_DEBUG(0, "Device %s removed.", gp->name);
+	}
+	g_orphan_provider(pp, ENXIO);
+	g_mountver_discard_queued(gp);
+	g_free(sc->sc_provider_name);
+	g_free(gp->softc);
+	gp->softc = NULL;
+	g_wither_geom(gp, ENXIO);
+
+	return (0);
+}
+
+static int
+g_mountver_destroy_geom(struct gctl_req *req, struct g_class *mp, struct g_geom *gp)
+{
+
+	return (g_mountver_destroy(gp, 0));
+}
+
+static void
+g_mountver_ctl_create(struct gctl_req *req, struct g_class *mp)
+{
+	struct g_provider *pp;
+	const char *name;
+	char param[16];
+	int i, *nargs;
+
+	g_topology_assert();
+
+	nargs = gctl_get_paraml(req, "nargs", sizeof(*nargs));
+	if (nargs == NULL) {
+		gctl_error(req, "No '%s' argument", "nargs");
+		return;
+	}
+	if (*nargs <= 0) {
+		gctl_error(req, "Missing device(s).");
+		return;
+	}
+	for (i = 0; i < *nargs; i++) {
+		snprintf(param, sizeof(param), "arg%d", i);
+		name = gctl_get_asciiparam(req, param);
+		if (name == NULL) {
+			gctl_error(req, "No 'arg%d' argument", i);
+			return;
+		}
+		if (strncmp(name, "/dev/", strlen("/dev/")) == 0)
+			name += strlen("/dev/");
+		pp = g_provider_by_name(name);
+		if (pp == NULL) {
+			G_MOUNTVER_DEBUG(1, "Provider %s is invalid.", name);
+			gctl_error(req, "Provider %s is invalid.", name);
+			return;
+		}
+		if (g_mountver_create(req, mp, pp) != 0)
+			return;
+	}
+}
+
+static struct g_geom *
+g_mountver_find_geom(struct g_class *mp, const char *name)
+{
+	struct g_geom *gp;
+
+	LIST_FOREACH(gp, &mp->geom, geom) {
+		if (strcmp(gp->name, name) == 0)
+			return (gp);
+	}
+	return (NULL);
+}
+
+static void
+g_mountver_ctl_destroy(struct gctl_req *req, struct g_class *mp)
+{
+	int *nargs, *force, error, i;
+	struct g_geom *gp;
+	const char *name;
+	char param[16];
+
+	g_topology_assert();
+
+	nargs = gctl_get_paraml(req, "nargs", sizeof(*nargs));
+	if (nargs == NULL) {
+		gctl_error(req, "No '%s' argument", "nargs");
+		return;
+	}
+	if (*nargs <= 0) {
+		gctl_error(req, "Missing device(s).");
+		return;
+	}
+	force = gctl_get_paraml(req, "force", sizeof(*force));
+	if (force == NULL) {
+		gctl_error(req, "No 'force' argument");
+		return;
+	}
+
+	for (i = 0; i < *nargs; i++) {
+		snprintf(param, sizeof(param), "arg%d", i);
+		name = gctl_get_asciiparam(req, param);
+		if (name == NULL) {
+			gctl_error(req, "No 'arg%d' argument", i);
+			return;
+		}
+		if (strncmp(name, "/dev/", strlen("/dev/")) == 0)
+			name += strlen("/dev/");
+		gp = g_mountver_find_geom(mp, name);
+		if (gp == NULL) {
+			G_MOUNTVER_DEBUG(1, "Device %s is invalid.", name);
+			gctl_error(req, "Device %s is invalid.", name);
+			return;
+		}
+		error = g_mountver_destroy(gp, *force);
+		if (error != 0) {
+			gctl_error(req, "Cannot destroy device %s (error=%d).",
+			    gp->name, error);
+			return;
+		}
+	}
+}
+
+static void
+g_mountver_orphan(struct g_consumer *cp)
+{
+	struct g_mountver_softc *sc;
+
+	g_topology_assert();
+
+	sc = cp->geom->softc;
+	sc->sc_orphaned = 1;
+	if (cp->acr > 0 || cp->acw > 0 || cp->ace > 0)
+		g_access(cp, -cp->acr, -cp->acw, -cp->ace);
+	g_detach(cp);
+	G_MOUNTVER_DEBUG(0, "%s is offline.  Mount verification in progress.", sc->sc_provider_name);
+}
+
+static int
+g_mountver_ident_matches(struct g_geom *gp)
+{
+	struct g_consumer *cp;
+	struct g_mountver_softc *sc;
+	char ident[DISK_IDENT_SIZE];
+	int error, identsize = DISK_IDENT_SIZE;
+
+	sc = gp->softc;
+	cp = LIST_FIRST(&gp->consumer);
+
+	if (g_mountver_check_ident == 0)
+		return (0);
+
+	error = g_access(cp, 1, 0, 0);
+	if (error != 0) {
+		G_MOUNTVER_DEBUG(0, "Cannot access %s; "
+		    "not attaching; error = %d.", gp->name, error);
+		return (1);
+	}
+	error = g_io_getattr("GEOM::ident", cp, &identsize, ident);
+	g_access(cp, -1, 0, 0);
+	if (error != 0) {
+		G_MOUNTVER_DEBUG(0, "Cannot get disk ident for %s; "
+		    "not attaching; error = %d.", gp->name, error);
+		return (1);
+	}
+	if (strcmp(ident, sc->sc_ident) != 0) {
+		G_MOUNTVER_DEBUG(1, "Disk ident for %s (\"%s\") is different "
+		    "from expected \"%s\", not attaching.", gp->name, ident,
+		    sc->sc_ident);
+		return (1);
+	}
+
+	return (0);
+}
+	
+static struct g_geom *
+g_mountver_taste(struct g_class *mp, struct g_provider *pp, int flags __unused)
+{
+	struct g_mountver_softc *sc;
+	struct g_consumer *cp;
+	struct g_geom *gp;
+	int error;
+
+	g_topology_assert();
+	g_trace(G_T_TOPOLOGY, "%s(%s, %s)", __func__, mp->name, pp->name);
+	G_MOUNTVER_DEBUG(2, "Tasting %s.", pp->name);
+
+	/*
+	 * Let's check if device already exists.
+	 */
+	LIST_FOREACH(gp, &mp->geom, geom) {
+		sc = gp->softc;
+		if (sc == NULL)
+			continue;
+
+		/* Already attached? */
+		if (pp == LIST_FIRST(&gp->provider))
+			return (NULL);
+
+		if (sc->sc_orphaned && strcmp(pp->name, sc->sc_provider_name) == 0)
+			break;
+	}
+	if (gp == NULL)
+		return (NULL);
+
+	cp = LIST_FIRST(&gp->consumer);
+	g_attach(cp, pp);
+	error = g_mountver_ident_matches(gp);
+	if (error != 0) {
+		g_detach(cp);
+		return (NULL);
+	}
+	if (sc->sc_access_r > 0 || sc->sc_access_w > 0 || sc->sc_access_e > 0) {
+		error = g_access(cp, sc->sc_access_r, sc->sc_access_w, sc->sc_access_e);
+		if (error != 0) {
+			G_MOUNTVER_DEBUG(0, "Cannot access %s; error = %d.", pp->name, error);
+			g_detach(cp);
+			return (NULL);
+		}
+	}
+	g_mountver_send_queued(gp);
+	sc->sc_orphaned = 0;
+	G_MOUNTVER_DEBUG(0, "%s has completed mount verification.", sc->sc_provider_name);
+
+	return (gp);
+}
+
+static void
+g_mountver_config(struct gctl_req *req, struct g_class *mp, const char *verb)
+{
+	uint32_t *version;
+
+	g_topology_assert();
+
+	version = gctl_get_paraml(req, "version", sizeof(*version));
+	if (version == NULL) {
+		gctl_error(req, "No '%s' argument.", "version");
+		return;
+	}
+	if (*version != G_MOUNTVER_VERSION) {
+		gctl_error(req, "Userland and kernel parts are out of sync.");
+		return;
+	}
+
+	if (strcmp(verb, "create") == 0) {
+		g_mountver_ctl_create(req, mp);
+		return;
+	} else if (strcmp(verb, "destroy") == 0) {
+		g_mountver_ctl_destroy(req, mp);
+		return;
+	}
+
+	gctl_error(req, "Unknown verb.");
+}
+
+static void
+g_mountver_dumpconf(struct sbuf *sb, const char *indent, struct g_geom *gp,
+    struct g_consumer *cp, struct g_provider *pp)
+{
+	struct g_mountver_softc *sc;
+
+	if (pp != NULL || cp != NULL)
+		return;
+
+	sc = gp->softc;
+	sbuf_printf(sb, "%s<State>%s</State>\n", indent,
+	    sc->sc_orphaned ? "OFFLINE" : "ONLINE");
+	sbuf_printf(sb, "%s<Provider-Name>%s</Provider-Name>\n", indent, sc->sc_provider_name);
+	sbuf_printf(sb, "%s<Disk-Ident>%s</Disk-Ident>\n", indent, sc->sc_ident);
+}
+
+static void
+g_mountver_shutdown_pre_sync(void *arg, int howto)
+{
+	struct g_class *mp;
+	struct g_geom *gp, *gp2;
+
+	mp = arg;
+	DROP_GIANT();
+	g_topology_lock();
+	LIST_FOREACH_SAFE(gp, &mp->geom, geom, gp2)
+		g_mountver_destroy(gp, 1);
+	g_topology_unlock();
+	PICKUP_GIANT();
+}
+
+static void
+g_mountver_init(struct g_class *mp)
+{
+
+	g_mountver_pre_sync = EVENTHANDLER_REGISTER(shutdown_pre_sync,
+	    g_mountver_shutdown_pre_sync, mp, SHUTDOWN_PRI_FIRST);
+	if (g_mountver_pre_sync == NULL)
+		G_MOUNTVER_DEBUG(0, "Warning! Cannot register shutdown event.");
+}
+
+static void
+g_mountver_fini(struct g_class *mp)
+{
+
+	if (g_mountver_pre_sync != NULL)
+		EVENTHANDLER_DEREGISTER(shutdown_pre_sync, g_mountver_pre_sync);
+}
+
+DECLARE_GEOM_CLASS(g_mountver_class, g_mountver);
diff --git a/sys/geom/mountver/g_mountver.h b/sys/geom/mountver/g_mountver.h
new file mode 100644
index 0000000..1dc8372
--- /dev/null
+++ b/sys/geom/mountver/g_mountver.h
@@ -0,0 +1,71 @@
+/*-
+ * Copyright (c) 2010 Edward Tomasz Napierala <trasz@FreeBSD.org>
+ * Copyright (c) 2004-2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef	_G_MOUNTVER_H_
+#define	_G_MOUNTVER_H_
+
+#define	G_MOUNTVER_CLASS_NAME	"MOUNTVER"
+#define	G_MOUNTVER_VERSION	4
+#define	G_MOUNTVER_SUFFIX	".mountver"
+
+#ifdef _KERNEL
+
+#define	G_MOUNTVER_DEBUG(lvl, ...)	do {				\
+	if (g_mountver_debug >= (lvl)) {				\
+		printf("GEOM_MOUNTVER");				\
+		if (g_mountver_debug > 0)				\
+			printf("[%u]", lvl);				\
+		printf(": ");						\
+		printf(__VA_ARGS__);					\
+		printf("\n");						\
+	}								\
+} while (0)
+#define	G_MOUNTVER_LOGREQ(bp, ...)	do {				\
+	if (g_mountver_debug >= 2) {					\
+		printf("GEOM_MOUNTVER[2]: ");				\
+		printf(__VA_ARGS__);					\
+		printf(" ");						\
+		g_print_bio(bp);					\
+		printf("\n");						\
+	}								\
+} while (0)
+
+struct g_mountver_softc {
+	TAILQ_HEAD(, bio)		sc_queue;
+	struct mtx			sc_mtx;
+	char				*sc_provider_name;
+	char				sc_ident[DISK_IDENT_SIZE];
+	int				sc_orphaned;
+	int				sc_access_r;
+	int				sc_access_w;
+	int				sc_access_e;
+};
+#endif	/* _KERNEL */
+
+#endif	/* _G_MOUNTVER_H_ */