This is a rather large commit that encompasses the new swapper,

    changes to the VM system to support the new swapper, VM bug
    fixes, several VM optimizations, and some additional revamping of the
    VM code.  The specific bug fixes will be documented with additional
    forced commits.  This commit is somewhat rough in regards to code
    cleanup issues.

Reviewed by:	"John S. Dyson" <root@dyson.iquest.net>, "David Greenman" <dg@root.com>

1 files changed, 41 insertions, 41 deletions

diff --git a/sys/vm/default_pager.c b/sys/vm/default_pager.c
index ba92894..16b7512 100644
--- a/sys/vm/default_pager.c
+++ b/sys/vm/default_pager.c
@@ -28,7 +28,15 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: default_pager.c,v 1.15 1998/02/06 12:14:20 eivind Exp $
+ * The default pager is responsible for supplying backing store to unbacked
+ * storage.  The backing store is usually swap so we just fall through to
+ * the swap routines.  However, since swap metadata has not been assigned,
+ * the swap routines assign and manage the swap backing store through the
+ * vm_page->swapblk field.  The object is only converted when the page is 
+ * physically freed after having been cleaned and even then vm_page->swapblk
+ * is maintained whenever a resident page also has swap backing store.
+ *
+ *	$Id: default_pager.c,v 1.16 1998/10/13 08:24:42 dg Exp $
  */
 
 #include <sys/param.h>
@@ -78,6 +86,14 @@ default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
 	return vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(round_page(offset + size)));
 }
 
+/*
+ * deallocate resources associated with default objects.   The default objects
+ * have no special resources allocated to them, but the vm_page's being used
+ * in this object might.  Still, we do not have to do anything - we will free
+ * the swapblk in the underlying vm_page's when we free the vm_page or
+ * garbage collect the vm_page cache list.
+ */
+
 static void
 default_pager_dealloc(object)
 	vm_object_t object;
@@ -88,9 +104,11 @@ default_pager_dealloc(object)
 }
 
 /*
- * The default pager has no backing store, so we always return
- * failure.
+ * Load pages from backing store.  Since OBJT_DEFAULT is converted to
+ * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never
+ * see a vm_page with assigned swap here.
  */
+
 static int
 default_pager_getpages(object, m, count, reqpage)
 	vm_object_t object;
@@ -101,6 +119,13 @@ default_pager_getpages(object, m, count, reqpage)
 	return VM_PAGER_FAIL;
 }
 
+/*
+ * Store pages to backing store.  We should assign swap and initiate
+ * I/O.  We do not actually convert the object to OBJT_SWAP here.  The
+ * object will be converted when the written-out vm_page_t is moved from the
+ * cache to the free list.
+ */
+
 static int
 default_pager_putpages(object, m, c, sync, rtvals)
 	vm_object_t object;
@@ -109,26 +134,22 @@ default_pager_putpages(object, m, c, sync, rtvals)
 	boolean_t sync;
 	int *rtvals;
 {
-	int i;
-
-	/*
-	 * Try to convert the object type into a OBJT_SWAP.
-	 * If the swp structure allocation fails, convert it
-	 * back to OBJT_DEFAULT and return failure. Otherwise
-	 * pass this putpages to the swap pager.
-	 */
-	object->type = OBJT_SWAP;
-
-	if (swap_pager_swp_alloc(object, M_KERNEL) != 0) {
-		object->type = OBJT_DEFAULT;
-		for (i = 0; i < c; i++)
-			rtvals[i] = VM_PAGER_FAIL;
-		return VM_PAGER_FAIL;
-	}
-
 	return swap_pager_putpages(object, m, c, sync, rtvals);
 }
 
+/*
+ * Tell us whether the backing store for the requested (object,index) is
+ * synchronized.  i.e. tell us whether we can throw the page away and 
+ * reload it later.  So, for example, if we are in the process of writing
+ * the page to its backing store, or if no backing store has been assigned,
+ * it is not yet synchronized.
+ *
+ * It is possible to have fully-synchronized swap assigned without the
+ * object having been converted.  We just call swap_pager_haspage() to
+ * deal with it since it must already deal with it plus deal with swap
+ * meta-data structures.
+ */
+
 static boolean_t
 default_pager_haspage(object, pindex, before, after)
 	vm_object_t object;
@@ -139,24 +160,3 @@ default_pager_haspage(object, pindex, before, after)
 	return FALSE;
 }
 
-void
-default_pager_convert_to_swap(object)
-	vm_object_t object;
-{
-	object->type = OBJT_SWAP;
-	if (swap_pager_swp_alloc(object, M_KERNEL) != 0) {
-		object->type = OBJT_DEFAULT;
-	}
-}
-
-void
-default_pager_convert_to_swapq(object)
-	vm_object_t object;
-{
-	if (object &&
-		(object->type == OBJT_DEFAULT) &&
-		(object != kernel_object && object != kmem_object) &&
-		(object->size > ((cnt.v_page_count - cnt.v_wire_count) / 4)))
-		default_pager_convert_to_swap(object);
-}
-