Add notification interface to libpager.

* libpager/data-return.c (_pager_seqnos_memory_object_data_return):
Notify pager on data eviction.

* libpager/priv.h (struct pager): New field.

* libpager/pager.h (struct pager_ops): New field.

3 files changed, 43 insertions, 3 deletions

diff --git a/libpager/data-return.c b/libpager/data-return.c
index 08255e3d..b8fb920c 100644
--- a/libpager/data-return.c
+++ b/libpager/data-return.c
@@ -37,6 +37,7 @@ _pager_seqnos_memory_object_data_return (mach_port_t object,
   off_t start;
   int npages;
   int i;
+  char notified;
   struct lock_request *lr;
   struct lock_list {struct lock_request *lr;
     struct lock_list *next;} *lock_list, *ll;
@@ -66,9 +67,6 @@ _pager_seqnos_memory_object_data_return (mach_port_t object,
       goto release_out;
     }
 
-  if (! dirty)
-    goto release_out;
-
   if (p->pager_state != NORMAL)
     {
       printf ("pager in wrong state for write\n");
@@ -85,6 +83,20 @@ _pager_seqnos_memory_object_data_return (mach_port_t object,
 
   pm_entries = &p->pagemap[start];
 
+  /* Prepare notified flag.  */
+  notified = !kcopy && p->ops->notify_evict;
+  if (! dirty && ! kcopy)
+    {
+      _pager_release_seqno (p, seqno);
+      goto notify;
+    }
+
+  if (! dirty)
+    {
+      _pager_allow_termination (p);
+      goto release_out;
+    }
+
   /* Make sure there are no other in-progress writes for any of these
      pages before we begin.  This imposes a little more serialization
      than we really have to require (because *all* future writes on
@@ -151,6 +163,24 @@ _pager_seqnos_memory_object_data_return (mach_port_t object,
   if (wakeup)
     condition_broadcast (&p->wakeup);
 
+ notify:
+
+  if (notified)
+    {
+      for (i = 0; i < npages; i++)
+	{
+	  short *pm_entry = &pm_entries[i];
+
+	  /* Clear any error that is left.  Notification on eviction
+	     is used only to change association of page, so any
+	     error may no longer be valid.  */
+	  *pm_entry = SET_PM_ERROR (SET_PM_NEXTERROR (*pm_entry, 0), 0);
+	}
+
+      /* Do notify user.  */
+      p->ops->notify_evict ((struct user_pager_info *) &p->upi,
+			    start, npages);
+    }
   _pager_allow_termination (p);
   mutex_unlock (&p->interlock);
   ports_port_deref (p);
diff --git a/libpager/pager.h b/libpager/pager.h
index 1f73078a..d8b38978 100644
--- a/libpager/pager.h
+++ b/libpager/pager.h
@@ -76,6 +76,15 @@ struct pager_ops
      If the user doesn't either, then it's OK for this function to do
      nothing or be set to NULL.  */
   void (*dropweak)(struct user_pager_info *upi);
+
+  /* The user may define this function.  If non-NULL, it is called when
+     you want be able to change association of pages to backing store.
+     You can change association of page only when notify_evict has been
+     called and you haven't touched page content after that.  Note there
+     is a possibility that a page is evicted, but user is not notified
+     about that.  The user should be able to handle this case.  */
+  void (*notify_evict) (struct user_pager_info *upi, off_t page,
+			off_t npages);
 };
 
 /* This de-muxer function is for use within libports_demuxer. */
diff --git a/libpager/priv.h b/libpager/priv.h
index e7665d3e..238023e2 100644
--- a/libpager/priv.h
+++ b/libpager/priv.h
@@ -53,6 +53,7 @@ struct pager
 
   boolean_t may_cache;
   memory_object_copy_strategy_t copy_strategy;
+  boolean_t notify_on_evict;
 
   /* Interface ports */
   memory_object_control_t memobjcntl;