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Index: head/sys/vm/vm_fault.c
===================================================================
--- head/sys/vm/vm_fault.c
+++ head/sys/vm/vm_fault.c
@@ -121,6 +121,7 @@
struct faultstate {
vm_page_t m;
+ vm_page_t m_cow;
vm_object_t object;
vm_pindex_t pindex;
vm_page_t first_m;
@@ -208,6 +209,7 @@
fault_deallocate(struct faultstate *fs)
{
+ fault_page_release(&fs->m_cow);
fault_page_release(&fs->m);
vm_object_pip_wakeup(fs->object);
if (fs->object != fs->first_object) {
@@ -818,7 +820,7 @@
fs.lookup_still_valid = true;
- fs.m = fs.first_m = NULL;
+ fs.m_cow = fs.m = fs.first_m = NULL;
/*
* Search for the page at object/offset.
@@ -1254,9 +1256,11 @@
vm_page_unwire(fs.m, PQ_INACTIVE);
}
/*
- * We no longer need the old page or object.
+ * Save the cow page to be released after
+ * pmap_enter is complete.
*/
- fault_page_release(&fs.m);
+ fs.m_cow = fs.m;
+ fs.m = NULL;
}
/*
* fs.object != fs.first_object due to above
Index: head/sys/vm/vm_object.c
===================================================================
--- head/sys/vm/vm_object.c
+++ head/sys/vm/vm_object.c
@@ -1605,6 +1605,14 @@
break;
/*
+ * If the backing object page is busy a grandparent or older
+ * page may still be undergoing CoW. It is not safe to
+ * collapse the backing object until it is quiesced.
+ */
+ if (p != NULL && vm_page_busied(p))
+ return (false);
+
+ /*
* See if the parent has the page or if the parent's object
* pager has the page. If the parent has the page but the page
* is not valid, the parent's object pager must have the page.
@@ -1907,8 +1915,7 @@
* If we do not entirely shadow the backing object,
* there is nothing we can do so we give up.
*/
- if (object->resident_page_count != object->size &&
- !vm_object_scan_all_shadowed(object)) {
+ if (!vm_object_scan_all_shadowed(object)) {
VM_OBJECT_WUNLOCK(backing_object);
break;
}

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