Index: sys/vm/vm_page.c
===================================================================
--- sys/vm/vm_page.c
+++ sys/vm/vm_page.c
@@ -1996,10 +1996,8 @@
 }
 
 /*
- * Allocate a page in the specified object with the given page index.  To
- * optimize insertion of the page into the object, the caller must also specify
- * the resident page in the object with largest index smaller than the given
- * page index, or NULL if no such page exists.
+ * Allocate a page in the specified object with the given page index.  If the
+ * object lock is dropped and regained, the pages iter is reset.
  */
 vm_page_t
 vm_page_alloc_iter(vm_object_t object, vm_pindex_t pindex, int req,
@@ -2141,9 +2139,9 @@
 		/*
 		 * Not allocatable, give up.
 		 */
-		pctrie_iter_reset(pages);
-		if (vm_domain_alloc_fail(vmd, object, req))
-			goto again;
+		vm_domain_alloc_fail(vmd, object, req);
+		if (req & VM_ALLOC_WAITFAIL)
+			pctrie_iter_reset(pages);
 		return (NULL);
 	}
 
@@ -2335,26 +2333,23 @@
 	KASSERT(npages > 0, ("vm_page_alloc_contig: npages is zero"));
 
 	vm_page_iter_init(&pages, object);
-	mpred = vm_radix_iter_lookup_lt(&pages, pindex);
-	KASSERT(mpred == NULL || mpred->pindex != pindex,
-	    ("vm_page_alloc_contig: pindex already allocated"));
-	for (;;) {
+	m_ret = NULL;
 #if VM_NRESERVLEVEL > 0
-		/*
-		 * Can we allocate the pages from a reservation?
-		 */
-		if (vm_object_reserv(object) &&
-		    (m_ret = vm_reserv_alloc_contig(object, pindex, domain,
-		    req, npages, low, high, alignment, boundary, &pages)) !=
-		    NULL) {
-			break;
-		}
+	/*
+	 * Can we allocate the pages from a reservation?
+	 */
+	if (vm_object_reserv(object)) {
+		m_ret = vm_reserv_alloc_contig(object, pindex, domain,
+		    req, npages, low, high, alignment, boundary, &pages);
+	}
 #endif
-		if ((m_ret = vm_page_find_contig_domain(domain, req, npages,
-		    low, high, alignment, boundary)) != NULL)
-			break;
-		if (!vm_domain_alloc_fail(VM_DOMAIN(domain), object, req))
-			return (NULL);
+	if (m_ret == NULL) {
+		m_ret = vm_page_find_contig_domain(domain, req, npages,
+		    low, high, alignment, boundary);
+	}
+	if (m_ret == NULL) {
+		(void)vm_domain_alloc_fail(VM_DOMAIN(domain), object, req);
+		return (NULL);
 	}
 
 	/*
@@ -2408,7 +2403,6 @@
 			}
 			return (NULL);
 		}
-		mpred = m;
 		if (memattr != VM_MEMATTR_DEFAULT)
 			pmap_page_set_memattr(m, memattr);
 		pindex++;
@@ -2467,9 +2461,9 @@
 		}
 	}
 	if (m == NULL) {
-		if (vm_domain_alloc_fail(vmd, NULL, req))
-			goto again;
-		return (NULL);
+		if (!vm_domain_alloc_fail(vmd, NULL, req))
+			return (NULL);
+		goto again;
 	}
 
 found:
@@ -5189,6 +5183,7 @@
 				break;
 			m = vm_page_alloc_iter(object, pindex + i,
 			    pflags | VM_ALLOC_COUNT(count - i), &pages);
+			/* pages was reset if alloc_iter lost the lock. */
 			if (m == NULL) {
 				if ((allocflags & (VM_ALLOC_NOWAIT |
 				    VM_ALLOC_WAITFAIL)) != 0)