Index: head/sys/kern/vfs_bio.c
===================================================================
--- head/sys/kern/vfs_bio.c
+++ head/sys/kern/vfs_bio.c
@@ -2746,7 +2746,7 @@
 		 * deadlocks once allocbuf() is called after
 		 * pages are vfs_busy_pages().
 		 */
-		vm_page_grab_pages(obj,
+		(void)vm_page_grab_pages(obj,
 		    OFF_TO_IDX(bp->b_offset) + bp->b_npages,
 		    VM_ALLOC_SYSTEM | VM_ALLOC_IGN_SBUSY |
 		    VM_ALLOC_NOBUSY | VM_ALLOC_WIRED,
Index: head/sys/sparc64/sparc64/pmap.c
===================================================================
--- head/sys/sparc64/sparc64/pmap.c
+++ head/sys/sparc64/sparc64/pmap.c
@@ -1248,7 +1248,7 @@
 	CPU_ZERO(&pm->pm_active);
 
 	VM_OBJECT_WLOCK(pm->pm_tsb_obj);
-	vm_page_grab_pages(pm->pm_tsb_obj, 0, VM_ALLOC_NORMAL |
+	(void)vm_page_grab_pages(pm->pm_tsb_obj, 0, VM_ALLOC_NORMAL |
 	    VM_ALLOC_NOBUSY | VM_ALLOC_WIRED | VM_ALLOC_ZERO, ma, TSB_PAGES);
 	VM_OBJECT_WUNLOCK(pm->pm_tsb_obj);
 	for (i = 0; i < TSB_PAGES; i++)
Index: head/sys/vm/vm_glue.c
===================================================================
--- head/sys/vm/vm_glue.c
+++ head/sys/vm/vm_glue.c
@@ -391,7 +391,7 @@
 	 * page of stack.
 	 */
 	VM_OBJECT_WLOCK(ksobj);
-	vm_page_grab_pages(ksobj, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY |
+	(void)vm_page_grab_pages(ksobj, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY |
 	    VM_ALLOC_WIRED, ma, pages);
 	for (i = 0; i < pages; i++)
 		ma[i]->valid = VM_PAGE_BITS_ALL;
@@ -568,7 +568,7 @@
 	pages = td->td_kstack_pages;
 	ksobj = td->td_kstack_obj;
 	VM_OBJECT_WLOCK(ksobj);
-	vm_page_grab_pages(ksobj, 0, VM_ALLOC_NORMAL | VM_ALLOC_WIRED, ma,
+	(void)vm_page_grab_pages(ksobj, 0, VM_ALLOC_NORMAL | VM_ALLOC_WIRED, ma,
 	    pages);
 	for (int i = 0; i < pages;) {
 		int j, a, count, rv;
Index: head/sys/vm/vm_page.h
===================================================================
--- head/sys/vm/vm_page.h
+++ head/sys/vm/vm_page.h
@@ -419,7 +419,7 @@
 #define	VM_ALLOC_IGN_SBUSY	0x1000	/* (gp) Ignore shared busy flag */
 #define	VM_ALLOC_NODUMP		0x2000	/* (ag) don't include in dump */
 #define	VM_ALLOC_SBUSY		0x4000	/* (acgp) Shared busy the page */
-#define	VM_ALLOC_NOWAIT		0x8000	/* (g) Do not sleep, return NULL */
+#define	VM_ALLOC_NOWAIT		0x8000	/* (gp) Do not sleep */
 #define	VM_ALLOC_COUNT_SHIFT	16
 #define	VM_ALLOC_COUNT(count)	((count) << VM_ALLOC_COUNT_SHIFT)
 
@@ -470,7 +470,7 @@
     vm_paddr_t boundary, vm_memattr_t memattr);
 vm_page_t vm_page_alloc_freelist(int, int);
 vm_page_t vm_page_grab (vm_object_t, vm_pindex_t, int);
-void vm_page_grab_pages(vm_object_t object, vm_pindex_t pindex, int allocflags,
+int vm_page_grab_pages(vm_object_t object, vm_pindex_t pindex, int allocflags,
     vm_page_t *ma, int count);
 int vm_page_try_to_free (vm_page_t);
 void vm_page_deactivate (vm_page_t);
Index: head/sys/vm/vm_page.c
===================================================================
--- head/sys/vm/vm_page.c
+++ head/sys/vm/vm_page.c
@@ -3173,13 +3173,15 @@
  * optional allocation flags:
  *	VM_ALLOC_IGN_SBUSY	do not sleep on soft busy pages
  *	VM_ALLOC_NOBUSY		do not exclusive busy the page
+ *	VM_ALLOC_NOWAIT		do not sleep
  *	VM_ALLOC_SBUSY		set page to sbusy state
  *	VM_ALLOC_WIRED		wire the pages
  *	VM_ALLOC_ZERO		zero and validate any invalid pages
  *
- * This routine may sleep.
+ * If VM_ALLOC_NOWAIT is not specified, this routine may sleep.  Otherwise, it
+ * may return a partial prefix of the requested range.
  */
-void
+int
 vm_page_grab_pages(vm_object_t object, vm_pindex_t pindex, int allocflags,
     vm_page_t *ma, int count)
 {
@@ -3197,7 +3199,7 @@
 	    (allocflags & VM_ALLOC_IGN_SBUSY) != 0,
 	    ("vm_page_grab_pages: VM_ALLOC_SBUSY/IGN_SBUSY mismatch"));
 	if (count == 0)
-		return;
+		return (0);
 	i = 0;
 retrylookup:
 	m = vm_page_lookup(object, pindex + i);
@@ -3206,6 +3208,8 @@
 			sleep = (allocflags & VM_ALLOC_IGN_SBUSY) != 0 ?
 			    vm_page_xbusied(m) : vm_page_busied(m);
 			if (sleep) {
+				if ((allocflags & VM_ALLOC_NOWAIT) != 0)
+					break;
 				/*
 				 * Reference the page before unlocking and
 				 * sleeping so that the page daemon is less
@@ -3233,6 +3237,8 @@
 			m = vm_page_alloc(object, pindex + i, (allocflags &
 			    ~VM_ALLOC_IGN_SBUSY) | VM_ALLOC_COUNT(count - i));
 			if (m == NULL) {
+				if ((allocflags & VM_ALLOC_NOWAIT) != 0)
+					break;
 				VM_OBJECT_WUNLOCK(object);
 				VM_WAIT;
 				VM_OBJECT_WLOCK(object);
@@ -3247,6 +3253,7 @@
 		ma[i] = m;
 		m = vm_page_next(m);
 	}
+	return (i);
 }
 
 /*