--- sys/fs/msdosfs/msdosfs_vfsops.c	2005/11/19 16:40:46
+++ sys/fs/msdosfs/msdosfs_vfsops.c	2006/03/25 19:17:56
@@ -285,7 +285,7 @@
 				return (error);
 			DROP_GIANT();
 			g_topology_lock();
-			g_access(pmp->pm_cp, 0, -1, 0);
+			g_vfs_access(pmp->pm_cp, 0, -1, 0);
 			g_topology_unlock();
 			PICKUP_GIANT();
 		} else if ((pmp->pm_flags & MSDOSFSMNT_RONLY) &&
@@ -307,7 +307,7 @@
 			}
 			DROP_GIANT();
 			g_topology_lock();
-			error = g_access(pmp->pm_cp, 0, 1, 0);
+			error = g_vfs_access(pmp->pm_cp, 0, 1, 0);
 			g_topology_unlock();
 			PICKUP_GIANT();
 			if (error)
--- sys/geom/geom_vfs.c	2006/03/02 05:40:19
+++ sys/geom/geom_vfs.c	2006/03/25 19:17:56
@@ -137,28 +137,43 @@
 	g_topology_assert();
 
 	*cpp = NULL;
-	pp = g_dev_getprovider(vp->v_rdev);
-	if (pp == NULL)
-		return (ENOENT);
-	gp = g_new_geomf(&g_vfs_class, "%s.%s", fsname, pp->name);
-	cp = g_new_consumer(gp);
-	g_attach(cp, pp);
-	error = g_access(cp, 1, wr, 1);
-	if (error) {
-		g_wither_geom(gp, ENXIO);
-		return (error);
+	bo = &vp->v_bufobj;
+	/* Is this first mount? */
+	if (bo->bo_private == vp) {
+		pp = g_dev_getprovider(vp->v_rdev);
+		if (pp == NULL)
+			return (ENOENT);
+		gp = g_new_geomf(&g_vfs_class, "%s.%s", fsname, pp->name);
+		cp = g_new_consumer(gp);
+		g_attach(cp, pp);
+		error = g_access(cp, 1, wr, 1);
+		if (error) {
+			g_wither_geom(gp, ENXIO);
+			return (error);
+		}
+		cp->private = vp;
+		vfslocked = VFS_LOCK_GIANT(vp->v_mount);
+		vnode_create_vobject(vp, pp->mediasize, curthread);
+		VFS_UNLOCK_GIANT(vfslocked);
+		bo = &vp->v_bufobj;
+		bo->bo_ops = g_vfs_bufops;
+		bo->bo_private = cp;
+		bo->bo_bsize = pp->sectorsize;
+		gp->softc = bo;
+	} else {
+		cp = bo->bo_private;
+		/*
+		 * Don't allow for mount when already mounted R/W.
+		 * Don't allow for R/W mount when already mounted.
+		 */
+		if (cp->acw > 0 || wr)
+			return (EPERM);
+		error = g_access(cp, 1, wr, 1);
+		if (error)
+			return (error);
 	}
-	vfslocked = VFS_LOCK_GIANT(vp->v_mount);
-	vnode_create_vobject(vp, pp->mediasize, curthread);
-	VFS_UNLOCK_GIANT(vfslocked);
 	*cpp = cp;
-	bo = &vp->v_bufobj;
-	bo->bo_ops = g_vfs_bufops;
-	bo->bo_private = cp;
-	bo->bo_bsize = pp->sectorsize;
-	gp->softc = bo;
-
-	return (error);
+	return (0);
 }
 
 void
@@ -171,6 +186,32 @@
 
 	gp = cp->geom;
 	bo = gp->softc;
-	bufobj_invalbuf(bo, V_SAVE, td, 0, 0);
-	g_wither_geom_close(gp, ENXIO);
+	/* Is this last close? */
+	if (cp->acr == 1) {
+		/*
+		 * Put device vnode back into bo_private, so we can mount this
+		 * file system later and first mount will be detected properly.
+		 */
+		bo->bo_private = cp->private;
+		bufobj_invalbuf(bo, V_SAVE, td, 0, 0);
+		g_wither_geom_close(gp, ENXIO);
+	} else {
+		/* It could be open only for reading here. */
+		KASSERT(cp->acr > 1 && cp->acw == 0 && cp->ace >= 0,
+		    ("Invalid access for %s (r%dw%de%d).", cp->provider->name,
+		    cp->acr, cp->acw, cp->ace));
+		g_access(cp, -1, 0, -1);
+	}
+}
+
+int
+g_vfs_access(struct g_consumer *cp, int dcr, int dcw, int dce)
+{
+
+	g_topology_assert();
+
+	/* If already mounted read-only multiple times, we cannot upgrade. */
+	if (dcw > 0 && cp->acr > 1)
+		return (EPERM);
+	return (g_access(cp, dcr, dcw, dce));
 }
--- sys/geom/geom_vfs.h	2005/02/10 12:10:50
+++ sys/geom/geom_vfs.h	2006/03/25 19:17:56
@@ -38,5 +38,6 @@
 void g_vfs_strategy(struct bufobj *bo, struct buf *bp);
 int g_vfs_open(struct vnode *vp, struct g_consumer **cpp, const char *fsname, int wr);
 void g_vfs_close(struct g_consumer *cp, struct thread *td);
+int g_vfs_access(struct g_consumer *cp, int dcr, int dcw, int dce);
 
 #endif /* _GEOM_GEOM_VFS_H_ */
--- sys/gnu/fs/ext2fs/ext2_vfsops.c	2006/01/09 20:49:39
+++ sys/gnu/fs/ext2fs/ext2_vfsops.c	2006/03/25 19:17:56
@@ -182,7 +182,7 @@
 			vfs_flagopt(opts, "ro", &mp->mnt_flag, MNT_RDONLY);
 			DROP_GIANT();
 			g_topology_lock();
-			g_access(ump->um_cp, 0, -1, 0);
+			g_vfs_access(ump->um_cp, 0, -1, 0);
 			g_topology_unlock();
 			PICKUP_GIANT();
 		}
@@ -209,7 +209,7 @@
 			}
 			DROP_GIANT();
 			g_topology_lock();
-			error = g_access(ump->um_cp, 0, 1, 0);
+			error = g_vfs_access(ump->um_cp, 0, 1, 0);
 			g_topology_unlock();
 			PICKUP_GIANT();
 			if (error)
--- sys/ufs/ffs/ffs_vfsops.c	2006/03/19 22:20:45
+++ sys/ufs/ffs/ffs_vfsops.c	2006/03/25 19:17:56
@@ -243,7 +243,7 @@
 			vn_finished_write(mp);
 			DROP_GIANT();
 			g_topology_lock();
-			g_access(ump->um_cp, 0, -1, 0);
+			g_vfs_access(ump->um_cp, 0, -1, 0);
 			g_topology_unlock();
 			PICKUP_GIANT();
 			fs->fs_ronly = 1;
@@ -289,9 +289,9 @@
 			 * yet, get it now.
 			 */
 			if (ump->um_cp->ace == 0)
-				error = g_access(ump->um_cp, 0, 1, 1);
+				error = g_vfs_access(ump->um_cp, 0, 1, 1);
 			else
-				error = g_access(ump->um_cp, 0, 1, 0);
+				error = g_vfs_access(ump->um_cp, 0, 1, 0);
 			g_topology_unlock();
 			PICKUP_GIANT();
 			if (error)
@@ -614,7 +614,7 @@
 	 * We will pick it up again when we remount R/W.
 	 */
 	if (error == 0 && ronly && (mp->mnt_flag & MNT_ROOTFS))
-		error = g_access(cp, 0, 0, -1);
+		error = g_vfs_access(cp, 0, 0, -1);
 	g_topology_unlock();
 	PICKUP_GIANT();
 	VOP_UNLOCK(devvp, 0, td);