Index: sys/vm/swap_pager.c
===================================================================
--- sys/vm/swap_pager.c
+++ sys/vm/swap_pager.c
@@ -568,7 +568,6 @@
 static void
 swblk_iter_init_only(struct pctrie_iter *blks, vm_object_t object)
 {
-	VM_OBJECT_ASSERT_LOCKED(object);
 	MPASS((object->flags & OBJ_SWAP) != 0);
 	pctrie_iter_init(blks, &object->un_pager.swp.swp_blks);
 }
@@ -578,6 +577,7 @@
 swblk_iter_init(struct pctrie_iter *blks, vm_object_t object,
     vm_pindex_t pindex)
 {
+	VM_OBJECT_ASSERT_LOCKED(object);
 	swblk_iter_init_only(blks, object);
 	return (swblk_iter_lookup_ge(blks, pindex));
 }
@@ -1117,8 +1117,8 @@
 	int n;
 
 	swp_pager_init_freerange(&range);
-	VM_OBJECT_WLOCK(object);
 	swblk_iter_init_only(&blks, object);
+	VM_OBJECT_WLOCK(object);
 	for (i = 0; i < size; i += n) {
 		n = MIN(size - i, INT_MAX);
 		blk = swp_pager_getswapspace(&n);
@@ -1264,6 +1264,7 @@
 {
 	struct pctrie_iter blks;
 
+	VM_OBJECT_ASSERT_LOCKED(object);
 	swblk_iter_init_only(&blks, object);
 	return (swp_pager_haspage_iter(&blks, pindex, before, after));
 }
@@ -1531,8 +1532,8 @@
 {
 	struct pctrie_iter blks;
 
-	VM_OBJECT_WLOCK(object);
 	swblk_iter_init_only(&blks, object);
+	VM_OBJECT_WLOCK(object);
 	return (swap_pager_getpages_locked(&blks, object, ma, count, rbehind,
 	    rahead));
 }
@@ -1636,8 +1637,8 @@
 				rtvals[i + j] = VM_PAGER_FAIL;
 			continue;
 		}
-		VM_OBJECT_WLOCK(object);
 		swblk_iter_init_only(&blks, object);
+		VM_OBJECT_WLOCK(object);
 		for (j = 0; j < n; ++j) {
 			mreq = ma[i + j];
 			vm_page_aflag_clear(mreq, PGA_SWAP_FREE);
@@ -2214,8 +2215,8 @@
 				pause("swzonxb", 10);
 			} else
 				uma_zwait(swblk_zone);
-			VM_OBJECT_WLOCK(object);
 			sb = swblk_iter_reinit(blks, object, pindex);
+			VM_OBJECT_WLOCK(object);
 			if (sb != NULL)
 				/*
 				 * Somebody swapped out a nearby page,
@@ -2246,8 +2247,8 @@
 				pause("swzonxp", 10);
 			} else
 				uma_zwait(swpctrie_zone);
-			VM_OBJECT_WLOCK(object);
 			sb1 = swblk_iter_reinit(blks, object, pindex);
+			VM_OBJECT_WLOCK(object);
 			if (sb1 != NULL) {
 				uma_zfree(swblk_zone, sb);
 				sb = sb1;