Index: sys/vm/swap_pager.c
===================================================================
--- sys/vm/swap_pager.c
+++ sys/vm/swap_pager.c
@@ -424,6 +424,11 @@
 static int	swapoff_one(struct swdevt *sp, struct ucred *cred);
 
 /*
+ * Swap swdevt functions
+ */
+static bool swp_swdevt_available(struct swdevt *sp, int npages);
+
+/*
  * Swap bitmap functions
  */
 static void	swp_pager_freeswapspace(daddr_t blk, daddr_t npages);
@@ -734,6 +739,16 @@
 	object->type = OBJT_DEAD;
 }
 
+static bool
+swp_swdevt_available(struct swdevt *sp, int npages)
+{
+
+	if (sp->sw_flags & SW_CLOSING)
+		return (false);
+	return (sp->sw_nblks - howmany(BBSIZE, PAGE_SIZE) - sp->sw_used >=
+	    npages );
+}
+
 /************************************************************************
  *			SWAP PAGER BITMAP ROUTINES			*
  ************************************************************************/
@@ -768,7 +783,7 @@
 	while (!TAILQ_EMPTY(&swtailq)) {
 		if (sp == NULL)
 			sp = TAILQ_FIRST(&swtailq);
-		if ((sp->sw_flags & SW_CLOSING) == 0)
+		if (swp_swdevt_available(sp, npages))
 			blk = blist_alloc(sp->sw_blist, &npages, mpages);
 		if (blk != SWAPBLK_NONE)
 			break;