Index: sys/fs/devfs/devfs_vnops.c
===================================================================
--- sys/fs/devfs/devfs_vnops.c
+++ sys/fs/devfs/devfs_vnops.c
@@ -598,8 +598,26 @@
 		VNPASS(vp->v_usecount == 1, vp);
 		/* Special casing of ttys for deadfs.  Probably redundant. */
 		dsw = dev->si_devsw;
-		if (dsw != NULL && (dsw->d_flags & D_TTY) != 0)
-			vp->v_vflag |= VV_ISTTY;
+		if (dsw != NULL) {
+			switch (dsw->d_flags & D_TYPEMASK) {
+			case D_NOTYPE:
+			case D_TAPE:
+				break;
+			case D_DISK:
+				vp->v_irflag |= VIRF_ISDISK;
+				break;
+			case D_TTY:
+				vp->v_vflag |= VV_ISTTY;
+				break;
+			case D_MEM:
+				break;
+			default:
+#ifdef INVARIANTS
+				panic("%s: unknown type %d\n", __func__, dsw->d_flags & D_TYPEMASK);
+#endif
+				break;
+			}
+		}
 		dev_unlock();
 		VI_UNLOCK(vp);
 		if ((dev->si_flags & SI_ETERNAL) != 0)
Index: sys/kern/vfs_subr.c
===================================================================
--- sys/kern/vfs_subr.c
+++ sys/kern/vfs_subr.c
@@ -3961,7 +3961,9 @@
 		strlcat(buf, "|VIRF_DOOMED", sizeof(buf));
 	if (vp->v_irflag & VIRF_PGREAD)
 		strlcat(buf, "|VIRF_PGREAD", sizeof(buf));
-	flags = vp->v_irflag & ~(VIRF_DOOMED | VIRF_PGREAD);
+	if (vp->v_irflag & VIRF_ISDISK)
+		strlcat(buf, "|VIRF_ISDISK", sizeof(buf));
+	flags = vp->v_irflag & ~(VIRF_DOOMED | VIRF_PGREAD | VIRF_ISDISK);
 	if (flags != 0) {
 		snprintf(buf2, sizeof(buf2), "|VIRF(0x%lx)", flags);
 		strlcat(buf, buf2, sizeof(buf));
@@ -5000,14 +5002,6 @@
 	return (error == 0);
 }
 
-bool
-vn_isdisk(struct vnode *vp)
-{
-	int error;
-
-	return (vn_isdisk_error(vp, &error));
-}
-
 /*
  * VOP_FPLOOKUP_VEXEC routines are subject to special circumstances, see
  * the comment above cache_fplookup for details.
Index: sys/sys/conf.h
===================================================================
--- sys/sys/conf.h
+++ sys/sys/conf.h
@@ -142,6 +142,7 @@
 /*
  * Types for d_flags.
  */
+#define	D_NOTYPE 0x0000
 #define	D_TAPE	0x0001
 #define	D_DISK	0x0002
 #define	D_TTY	0x0004
Index: sys/sys/vnode.h
===================================================================
--- sys/sys/vnode.h
+++ sys/sys/vnode.h
@@ -246,6 +246,7 @@
 #define	VIRF_DOOMED	0x0001	/* This vnode is being recycled */
 #define	VIRF_PGREAD	0x0002	/* Direct reads from the page cache are permitted,
 				   never cleared once set */
+#define	VIRF_ISDISK	0x0004	/* This vnode is a disk device */
 
 #define	VI_TEXT_REF	0x0001	/* Text ref grabbed use ref */
 #define	VI_MOUNT	0x0002	/* Mount in progress */
@@ -719,7 +720,11 @@
 	    struct thread *fsize_td);
 int	vn_need_pageq_flush(struct vnode *vp);
 bool	vn_isdisk_error(struct vnode *vp, int *errp);
-bool	vn_isdisk(struct vnode *vp);
+static inline bool
+vn_isdisk(struct vnode *vp)
+{
+	return ((vp->v_irflag & VIRF_ISDISK) != 0);
+}
 int	_vn_lock(struct vnode *vp, int flags, const char *file, int line);
 #define vn_lock(vp, flags) _vn_lock(vp, flags, __FILE__, __LINE__)
 int	vn_open(struct nameidata *ndp, int *flagp, int cmode, struct file *fp);