[src/trunk]: src/sys/uvm In uao_put(), if we wait for the busy page owned by ...

[enami <enami%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9901713fd085
branches:  trunk
changeset: 526716:9901713fd085
user:      enami <enami%NetBSD.org@localhost>
date:      Thu May 09 07:04:23 2002 +0000

description:
In uao_put(), if we wait for the busy page owned by someone else,
we can't simply reuse the pointor to the page.  Instead, we need to
acquire it again.  So, rearrange the loop like genfs_putpages() does.
Reviewed by chuq.

diffstat:

 sys/uvm/uvm_aobj.c |  62 ++++++++++++++++++++++++++++++++++++++++-------------
 1 files changed, 46 insertions(+), 16 deletions(-)

diffs (129 lines):

diff -r 90e9ef82a892 -r 9901713fd085 sys/uvm/uvm_aobj.c
--- a/sys/uvm/uvm_aobj.c        Thu May 09 06:49:15 2002 +0000
+++ b/sys/uvm/uvm_aobj.c        Thu May 09 07:04:23 2002 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_aobj.c,v 1.50 2002/03/08 20:48:47 thorpej Exp $    */
+/*     $NetBSD: uvm_aobj.c,v 1.51 2002/05/09 07:04:23 enami Exp $      */
 
 /*
  * Copyright (c) 1998 Chuck Silvers, Charles D. Cranor and
@@ -43,7 +43,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_aobj.c,v 1.50 2002/03/08 20:48:47 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_aobj.c,v 1.51 2002/05/09 07:04:23 enami Exp $");
 
 #include "opt_uvmhist.h"
 
@@ -766,7 +766,7 @@
        int flags;
 {
        struct uvm_aobj *aobj = (struct uvm_aobj *)uobj;
-       struct vm_page *pg, *nextpg;
+       struct vm_page *pg, *nextpg, curmp, endmp;
        boolean_t by_list;
        voff_t curoff;
        UVMHIST_FUNC("uao_put"); UVMHIST_CALLED(maphist);
@@ -802,32 +802,48 @@
        }
 
        /*
+        * Initialize the marker pages.  See the comment in
+        * genfs_putpages() also.
+        */
+
+       curmp.uobject = uobj;
+       curmp.offset = (voff_t)-1;
+       curmp.flags = PG_BUSY;
+       endmp.uobject = uobj;
+       endmp.offset = (voff_t)-1;
+       endmp.flags = PG_BUSY;
+
+       /*
         * now do it.  note: we must update nextpg in the body of loop or we
-        * will get stuck.  we need to use nextpg because we may free "pg"
-        * before doing the next loop.
+        * will get stuck.  we need to use nextpg if we'll traverse the list
+        * because we may free "pg" before doing the next loop.
         */
 
        if (by_list) {
-               pg = TAILQ_FIRST(&uobj->memq);
+               TAILQ_INSERT_TAIL(&uobj->memq, &endmp, listq);
+               nextpg = TAILQ_FIRST(&uobj->memq);
+               PHOLD(curproc);
        } else {
                curoff = start;
-               pg = uvm_pagelookup(uobj, curoff);
        }
 
-       nextpg = NULL;
        uvm_lock_pageq();
 
        /* locked: both page queues and uobj */
-       for ( ; (by_list && pg != NULL) ||
-           (!by_list && curoff < stop) ; pg = nextpg) {
+       for (;;) {
                if (by_list) {
+                       pg = nextpg;
+                       if (pg == &endmp)
+                               break;
                        nextpg = TAILQ_NEXT(pg, listq);
                        if (pg->offset < start || pg->offset >= stop)
                                continue;
                } else {
-                       curoff += PAGE_SIZE;
-                       if (curoff < stop)
-                               nextpg = uvm_pagelookup(uobj, curoff);
+                       if (curoff < stop) {
+                               pg = uvm_pagelookup(uobj, curoff);
+                               curoff += PAGE_SIZE;
+                       } else
+                               break;
                        if (pg == NULL)
                                continue;
                }
@@ -868,18 +884,28 @@
                                continue;
 
                        /*
-                        * wait if the page is busy, then free the swap slot
-                        * and the page.
+                        * wait and try again if the page is busy.
+                        * otherwise free the swap slot and the page.
                         */
 
                        pmap_page_protect(pg, VM_PROT_NONE);
-                       while (pg->flags & PG_BUSY) {
+                       if (pg->flags & PG_BUSY) {
+                               if (by_list) {
+                                       TAILQ_INSERT_BEFORE(pg, &curmp, listq);
+                               }
                                pg->flags |= PG_WANTED;
                                uvm_unlock_pageq();
                                UVM_UNLOCK_AND_WAIT(pg, &uobj->vmobjlock, 0,
                                    "uao_put", 0);
                                simple_lock(&uobj->vmobjlock);
                                uvm_lock_pageq();
+                               if (by_list) {
+                                       nextpg = TAILQ_NEXT(&curmp, listq);
+                                       TAILQ_REMOVE(&uobj->memq, &curmp,
+                                           listq);
+                               } else
+                                       curoff -= PAGE_SIZE;
+                               continue;
                        }
                        uao_dropswap(uobj, pg->offset >> PAGE_SHIFT);
                        uvm_pagefree(pg);
@@ -888,6 +914,10 @@
        }
        uvm_unlock_pageq();
        simple_unlock(&uobj->vmobjlock);
+       if (by_list) {
+               TAILQ_REMOVE(&uobj->memq, &endmp, listq);
+               PRELE(curproc);
+       }
        return 0;
 }