Index: sys/kern/vfs_subr.c
===================================================================
--- sys/kern/vfs_subr.c
+++ sys/kern/vfs_subr.c
@@ -1746,8 +1746,6 @@
 		    ((flags & V_ALT) && (bp->b_xflags & BX_ALTDATA) == 0)) {
 			continue;
 		}
-		lblkno = 0;
-		xflags = 0;
 		if (nbp != NULL) {
 			lblkno = nbp->b_lblkno;
 			xflags = nbp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN);
@@ -1782,10 +1780,9 @@
 		bp->b_flags &= ~B_ASYNC;
 		brelse(bp);
 		BO_LOCK(bo);
-		nbp = gbincore(bo, lblkno);
-		if (nbp == NULL || (nbp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN))
-		    != xflags)
-			break;			/* nbp invalid */
+		if (nbp == NULL || (nbp = gbincore(bo, lblkno)) == NULL ||
+		    (nbp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN)) != xflags)
+			break;	/* loop is finished or nbp is invalid */
 	}
 	return (retval);
 }