Re: CVS commit: src/sys/uvm

[Jason R Thorpe <thorpej%wasabisystems.com@localhost>]

On Tue, Mar 04, 2003 at 04:43:37PM +0900, enami tsugutomo wrote:

 > I'm afraid null pointer is dereferenced when accessing something like
 > uobj->pgops->pgo_put (we test if pgo_put is null or not, but doesn't
 > test if pgops is null).

Ok, *this* is the patch I'll check in.  It adds a very minimal pager
for the uvm_loanzero_object.

-- 
        -- Jason R. Thorpe <thorpej%wasabisystems.com@localhost>

Index: uvm_loan.c
===================================================================
RCS file: /cvsroot/src/sys/uvm/uvm_loan.c,v
retrieving revision 1.40
diff -c -r1.40 uvm_loan.c
*** uvm_loan.c  2003/03/04 06:18:54     1.40
--- uvm_loan.c  2003/03/05 01:49:40
***************
*** 842,847 ****
--- 842,899 ----
  }
  
  /*
+  * Minimal pager for uvm_loanzero_object.  We need to provide a "put"
+  * method, because the page can end up on a paging queue, and the
+  * page daemon will want to call pgo_put when it encounters the page
+  * on the inactive list.
+  */
+ 
+ static int
+ ulz_put(struct uvm_object *uobj, voff_t start, voff_t stop, int flags)
+ {
+       struct vm_page *pg;
+ 
+       KDASSERT(uobj == &uvm_loanzero_object);
+ 
+       /*
+        * Don't need to do any work here if we're not freeing pages.
+        */
+ 
+       if ((flags & PGO_FREE) == 0) {
+               simple_unlock(&uobj->vmobjlock);
+               return 0;
+       }
+ 
+       /*
+        * we don't actually want to ever free the uvm_loanzero_page, so
+        * just reactivate or dequeue it.
+        */
+ 
+       pg = TAILQ_FIRST(&uobj->memq);
+       KASSERT(pg != NULL);
+       KASSERT(TAILQ_NEXT(pg, listq) == NULL);
+ 
+       uvm_lock_pageq();
+       if (pg->uanon)
+               uvm_pageactivate(pg);
+       else
+               uvm_pagedequeue(pg);
+       uvm_unlock_pageq();
+ 
+       simple_unlock(&uobj->vmobjlock);
+       return 0;
+ }
+ 
+ static struct uvm_pagerops ulz_pager = {
+       NULL,           /* init */
+       NULL,           /* reference */
+       NULL,           /* detach */
+       NULL,           /* fault */
+       NULL,           /* get */
+       ulz_put,        /* put */
+ };
+ 
+ /*
   * uvm_loan_init(): initialize the uvm_loan() facility.
   */
  
***************
*** 851,854 ****
--- 903,907 ----
  
        simple_lock_init(&uvm_loanzero_object.vmobjlock);
        TAILQ_INIT(&uvm_loanzero_object.memq);
+       uvm_loanzero_object.pgops = &ulz_pager;
  }