Refactor disk disconnection and geom destruction handling sequences.

Do not close/destroy opened consumer directly in case of disconnect. Instead
keep it existing until it will be closed in regular way in response to
upstream provider destruction. Delay geom destruction in the same way.
Previous implementation could destroy consumers still having active
requests and worked only because of global workaround made on GEOM level.

sys/geom/concat/g_concat.c

@@ -117,25 +117,33 @@ g_concat_remove_disk(struct g_concat_disk *disk)
 	struct g_consumer *cp;
 	struct g_concat_softc *sc;
 
+	g_topology_assert();
 	KASSERT(disk->d_consumer != NULL, ("Non-valid disk in %s.", __func__));
 	sc = disk->d_softc;
 	cp = disk->d_consumer;
 
-	G_CONCAT_DEBUG(0, "Disk %s removed from %s.", cp->provider->name,
-	    sc->sc_name);
+	if (!disk->d_removed) {
+		G_CONCAT_DEBUG(0, "Disk %s removed from %s.",
+		    cp->provider->name, sc->sc_name);
+		disk->d_removed = 1;
+	}
 
-	disk->d_consumer = NULL;
 	if (sc->sc_provider != NULL) {
 		sc->sc_provider->flags |= G_PF_WITHER;
+		G_CONCAT_DEBUG(0, "Device %s deactivated.",
+		    sc->sc_provider->name);
 		g_orphan_provider(sc->sc_provider, ENXIO);
 		sc->sc_provider = NULL;
-		G_CONCAT_DEBUG(0, "Device %s removed.", sc->sc_name);
 	}
 
 	if (cp->acr > 0 || cp->acw > 0 || cp->ace > 0)
-		g_access(cp, -cp->acr, -cp->acw, -cp->ace);
+		return;
+	disk->d_consumer = NULL;
 	g_detach(cp);
 	g_destroy_consumer(cp);
+	/* If there are no valid disks anymore, remove device. */
+	if (LIST_EMPTY(&sc->sc_geom->consumer))
+		g_concat_destroy(sc, 1);
 }
 
 static void
@@ -155,37 +163,18 @@ g_concat_orphan(struct g_consumer *cp)
 	if (disk == NULL)	/* Possible? */
 		return;
 	g_concat_remove_disk(disk);
-
-	/* If there are no valid disks anymore, remove device. */
-	if (g_concat_nvalid(sc) == 0)
-		g_concat_destroy(sc, 1);
 }
 
 static int
 g_concat_access(struct g_provider *pp, int dr, int dw, int de)
 {
-	struct g_consumer *cp1, *cp2;
-	struct g_concat_softc *sc;
+	struct g_consumer *cp1, *cp2, *tmp;
+	struct g_concat_disk *disk;
 	struct g_geom *gp;
 	int error;
 
+	g_topology_assert();
 	gp = pp->geom;
-	sc = gp->softc;
-
-	if (sc == NULL) {
-		/*
-		 * It looks like geom is being withered.
-		 * In that case we allow only negative requests.
-		 */
-		KASSERT(dr <= 0 && dw <= 0 && de <= 0,
-		    ("Positive access request (device=%s).", pp->name));
-		if ((pp->acr + dr) == 0 && (pp->acw + dw) == 0 &&
-		    (pp->ace + de) == 0) {
-			G_CONCAT_DEBUG(0, "Device %s definitely destroyed.",
-			    gp->name);
-		}
-		return (0);
-	}
 
 	/* On first open, grab an extra "exclusive" bit */
 	if (pp->acr == 0 && pp->acw == 0 && pp->ace == 0)
@@ -194,22 +183,24 @@ g_concat_access(struct g_provider *pp, int dr, int dw, int de)
 	if ((pp->acr + dr) == 0 && (pp->acw + dw) == 0 && (pp->ace + de) == 0)
 		de--;
 
-	error = ENXIO;
-	LIST_FOREACH(cp1, &gp->consumer, consumer) {
+	LIST_FOREACH_SAFE(cp1, &gp->consumer, consumer, tmp) {
 		error = g_access(cp1, dr, dw, de);
-		if (error == 0)
-			continue;
-		/*
-		 * If we fail here, backout all previous changes.
-		 */
-		LIST_FOREACH(cp2, &gp->consumer, consumer) {
-			if (cp1 == cp2)
-				return (error);
-			g_access(cp2, -dr, -dw, -de);
+		if (error != 0)
+			goto fail;
+		disk = cp1->private;
+		if (cp1->acr == 0 && cp1->acw == 0 && cp1->ace == 0 &&
+		    disk->d_removed) {
+			g_concat_remove_disk(disk); /* May destroy geom. */
 		}
-		/* NOTREACHED */
 	}
+	return (0);
 
+fail:
+	LIST_FOREACH(cp2, &gp->consumer, consumer) {
+		if (cp1 == cp2)
+			break;
+		g_access(cp2, -dr, -dw, -de);
+	}
 	return (error);
 }
 
@@ -391,6 +382,7 @@ g_concat_check_and_run(struct g_concat_softc *sc)
 	u_int no, sectorsize = 0;
 	off_t start;
 
+	g_topology_assert();
 	if (g_concat_nvalid(sc) != sc->sc_ndisks)
 		return;
 
@@ -419,7 +411,7 @@ g_concat_check_and_run(struct g_concat_softc *sc)
 	sc->sc_provider = pp;
 	g_error_provider(pp, 0);
 
-	G_CONCAT_DEBUG(0, "Device %s activated.", sc->sc_name);
+	G_CONCAT_DEBUG(0, "Device %s activated.", sc->sc_provider->name);
 }
 
 static int
@@ -461,6 +453,7 @@ g_concat_add_disk(struct g_concat_softc *sc, struct g_provider *pp, u_int no)
 	struct g_geom *gp;
 	int error;
 
+	g_topology_assert();
 	/* Metadata corrupted? */
 	if (no >= sc->sc_ndisks)
 		return (EINVAL);
@@ -509,6 +502,7 @@ g_concat_add_disk(struct g_concat_softc *sc, struct g_provider *pp, u_int no)
 	disk->d_softc = sc;
 	disk->d_start = 0;	/* not yet */
 	disk->d_end = 0;	/* not yet */
+	disk->d_removed = 0;
 
 	G_CONCAT_DEBUG(0, "Disk %s attached to %s.", pp->name, sc->sc_name);
 
@@ -576,8 +570,8 @@ static int
 g_concat_destroy(struct g_concat_softc *sc, boolean_t force)
 {
 	struct g_provider *pp;
+	struct g_consumer *cp, *cp1;
 	struct g_geom *gp;
-	u_int no;
 
 	g_topology_assert();
 
@@ -597,24 +591,23 @@ g_concat_destroy(struct g_concat_softc *sc, boolean_t force)
 		}
 	}
 
-	for (no = 0; no < sc->sc_ndisks; no++) {
-		if (sc->sc_disks[no].d_consumer != NULL)
-			g_concat_remove_disk(&sc->sc_disks[no]);
-	}
-
 	gp = sc->sc_geom;
+	LIST_FOREACH_SAFE(cp, &gp->consumer, consumer, cp1) {
+		g_concat_remove_disk(cp->private);
+		if (cp1 == NULL)
+			return (0);	/* Recursion happened. */
+	}
+	if (!LIST_EMPTY(&gp->consumer))
+		return (EINPROGRESS);
+
 	gp->softc = NULL;
 	KASSERT(sc->sc_provider == NULL, ("Provider still exists? (device=%s)",
 	    gp->name));
 	free(sc->sc_disks, M_CONCAT);
 	free(sc, M_CONCAT);
 
-	pp = LIST_FIRST(&gp->provider);
-	if (pp == NULL || (pp->acr == 0 && pp->acw == 0 && pp->ace == 0))
-		G_CONCAT_DEBUG(0, "Device %s destroyed.", gp->name);
-
+	G_CONCAT_DEBUG(0, "Device %s destroyed.", gp->name);
 	g_wither_geom(gp, ENXIO);
-
 	return (0);
 }
 

sys/geom/concat/g_concat.h

@@ -72,6 +72,7 @@ struct g_concat_disk {
 	struct g_concat_softc	*d_softc;
 	off_t			 d_start;
 	off_t			 d_end;
+	int			 d_removed;
 };
 
 struct g_concat_softc {