PAGES LOST IN VM SYSTEM

	The bug is that the call to vm_page_deactivate() at line 531 of
vm_fault.c does not put the (now no longer needed) page back on the
inactive list, because vm_page_deactivate() only does anything with
active pages.  Consequently, the page is then not on the active,
inactive or free lists and is effectively not available for use.  (It is
not lost forever, though, because it is still on its object's page
queue.)

AUTHOR:		Paul Mackerras (paulus@cs.anu.edu.au)
386BSD-Patchkit: patch00074

diff --git a/usr/src/sys.386bsd/vm/vm_page.c b/usr/src/sys.386bsd/vm/vm_page.c
index 0e794db..b8bab15 100644 (file)
--- a/usr/src/sys.386bsd/vm/vm_page.c
+++ b/usr/src/sys.386bsd/vm/vm_page.c
@@ -60,6 +60,14 @@
  *
  * any improvements or extensions that they make and grant Carnegie the
  * rights to redistribute these changes.
  *
  * any improvements or extensions that they make and grant Carnegie the
  * rights to redistribute these changes.

+ *
+ * PATCHES MAGIC                LEVEL   PATCH THAT GOT US HERE
+ * --------------------         -----   ----------------------
+ * CURRENT PATCH LEVEL:         1       00074
+ * --------------------         -----   ----------------------
+ *
+ * 22 Jan 93   Paul Mackerras          Fixed bug where pages got lost
+ *

  */
 
 /*
  */
 
 /*


@@ -687,15 +695,22 @@ void vm_page_deactivate(m)
        /*
         *      Only move active pages -- ignore locked or already
         *      inactive ones.
        /*
         *      Only move active pages -- ignore locked or already
         *      inactive ones.

+        *
+        *      XXX: sometimes we get pages which aren't wired down
+        *      or on any queue - we need to put them on the inactive
+        *      queue also, otherwise we lose track of them.
+        *      Paul Mackerras (paulus@cs.anu.edu.au) 9-Jan-93.

         */
 
         */
 

-       if (m->active) {
+       if (!m->inactive && m->wire_count == 0) {

                pmap_clear_reference(VM_PAGE_TO_PHYS(m));
                pmap_clear_reference(VM_PAGE_TO_PHYS(m));

-               queue_remove(&vm_page_queue_active, m, vm_page_t, pageq);
+               if (m->active) {
+                       queue_remove(&vm_page_queue_active, m, vm_page_t, pageq);
+                       m->active = FALSE;
+                       vm_page_active_count--;
+               }

                queue_enter(&vm_page_queue_inactive, m, vm_page_t, pageq);
                queue_enter(&vm_page_queue_inactive, m, vm_page_t, pageq);

-               m->active = FALSE;

                m->inactive = TRUE;
                m->inactive = TRUE;

-               vm_page_active_count--;

                vm_page_inactive_count++;
                if (pmap_is_modified(VM_PAGE_TO_PHYS(m)))
                        m->clean = FALSE;
                vm_page_inactive_count++;
                if (pmap_is_modified(VM_PAGE_TO_PHYS(m)))
                        m->clean = FALSE;