[src/uebayasi-xip]: src/sys Move zero-page into a common place, in the hope t...

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

details:   https://anonhg.NetBSD.org/src/rev/a4d4f68945fa
branches:  uebayasi-xip
changeset: 751857:a4d4f68945fa
user:      uebayasi <uebayasi%NetBSD.org@localhost>
date:      Mon Nov 15 17:32:01 2010 +0000

description:
Move zero-page into a common place, in the hope that it's shared
for other purposes.

According to Chuck Silvers, zero-page mappings don't need to be
explicitly unmapped in putpages().  Follow that advice.

diffstat:

 sys/miscfs/genfs/genfs_io.c |  35 +++++++----------------------------
 sys/uvm/uvm_page.c          |  45 +++++++++++++++++++++++++++++++++++++++++++--
 sys/uvm/uvm_page.h          |   5 ++++-
 3 files changed, 54 insertions(+), 31 deletions(-)

diffs (172 lines):

diff -r 252916ff7bd5 -r a4d4f68945fa sys/miscfs/genfs/genfs_io.c
--- a/sys/miscfs/genfs/genfs_io.c       Mon Nov 15 15:11:52 2010 +0000
+++ b/sys/miscfs/genfs/genfs_io.c       Mon Nov 15 17:32:01 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: genfs_io.c,v 1.36.2.30 2010/11/06 08:08:44 uebayasi Exp $      */
+/*     $NetBSD: genfs_io.c,v 1.36.2.31 2010/11/15 17:32:01 uebayasi Exp $      */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: genfs_io.c,v 1.36.2.30 2010/11/06 08:08:44 uebayasi Exp $");
+__KERNEL_RCSID(0, "$NetBSD: genfs_io.c,v 1.36.2.31 2010/11/15 17:32:01 uebayasi Exp $");
 
 #include "opt_xip.h"
 
@@ -873,18 +873,8 @@
                 *   allocated and linearly ordered by physical address.
                 */
                if (blkno < 0) {
-                       zero_page = uvm_pagelookup(uobj, 0);
-
-                       if (zero_page == NULL) {
-                               mutex_enter(&uobj->vmobjlock);
-                               zero_page = uvm_pagealloc(uobj, 0, NULL,
-                                   UVM_PGA_ZERO);
-                               mutex_exit(&uobj->vmobjlock);
-                               KASSERT(zero_page != NULL);
-                               mutex_enter(&uvm_pageqlock);
-                               uvm_pagewire(zero_page);
-                               mutex_exit(&uvm_pageqlock);
-                       }
+                       zero_page = uvm_page_zeropage_alloc();
+                       KASSERT(zero_page != NULL);
                        pps[i] = zero_page;
                } else {
                        struct vm_physseg *seg;
@@ -918,10 +908,10 @@
        for (i = 0; i < npages; i++) {
                struct vm_page *pg = pps[i];
 
+               KASSERT((pg->flags & PG_RDONLY) != 0);
                if (pg == zero_page) {
                } else {
                        KASSERT((pg->flags & PG_BUSY) == 0);
-                       KASSERT((pg->flags & PG_RDONLY) != 0);
                        KASSERT((pg->flags & PG_CLEAN) != 0);
                        KASSERT((pg->flags & PG_DEVICE) != 0);
                        pg->flags |= PG_BUSY;
@@ -1544,8 +1534,8 @@
                        pg = pgs[i];
                        if (pg == NULL || pg == PGO_DONTCARE)
                                continue;
-                       if (pg == zero_page) {
-                               put_zero_page = true;
+                       if (pg == uvm_page_zeropage) {
+                               /* Do nothing for holes. */
                        } else {
                                /*
                                 * Freeing normal XIP pages; nothing to do.
@@ -1562,17 +1552,6 @@
                off += npages << PAGE_SHIFT;
        }
 
-       if (put_zero_page) {
-               /*
-                * Freeing an XIP zero page.
-                */
-               pmap_page_protect(zero_page, VM_PROT_NONE);
-               mutex_enter(&uvm_pageqlock);
-               uvm_pageunwire(zero_page);
-               mutex_exit(&uvm_pageqlock);
-               uvm_pagefree(zero_page);
-       }
-
        KASSERT(uobj->uo_npages == 0);
 
 done:
diff -r 252916ff7bd5 -r a4d4f68945fa sys/uvm/uvm_page.c
--- a/sys/uvm/uvm_page.c        Mon Nov 15 15:11:52 2010 +0000
+++ b/sys/uvm/uvm_page.c        Mon Nov 15 17:32:01 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_page.c,v 1.153.2.64 2010/11/12 19:02:44 uebayasi Exp $     */
+/*     $NetBSD: uvm_page.c,v 1.153.2.65 2010/11/15 17:32:01 uebayasi Exp $     */
 
 /*
  * Copyright (c) 2010 The NetBSD Foundation, Inc.
@@ -97,7 +97,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_page.c,v 1.153.2.64 2010/11/12 19:02:44 uebayasi Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_page.c,v 1.153.2.65 2010/11/15 17:32:01 uebayasi Exp $");
 
 #include "opt_ddb.h"
 #include "opt_uvmhist.h"
@@ -113,6 +113,7 @@
 #include <sys/proc.h>
 #include <sys/atomic.h>
 #include <sys/cpu.h>
+#include <sys/once.h>
 
 #include <uvm/uvm.h>
 #include <uvm/uvm_ddb.h>
@@ -2234,6 +2235,46 @@
        return (VM_PHYSMEM_PTR(lcv)->free_list);
 }
 
+static int uvm_page_zeropage_init(void);
+
+struct vm_page *uvm_page_zeropage;
+
+struct vm_page *
+uvm_page_zeropage_alloc(void)
+{
+       static ONCE_DECL(inited);
+
+       (void)RUN_ONCE(&inited, uvm_page_zeropage_init);
+       KASSERT(uvm_page_zeropage != NULL);
+       return uvm_page_zeropage;
+}
+
+static int
+uvm_page_zeropage_init(void)
+{
+       struct pglist mlist;
+       struct vm_page *pg;
+       int n;
+
+       n = uvm_pglistalloc(PAGE_SIZE, 0, -1, PAGE_SIZE, PAGE_SIZE,
+           &mlist, 1, 1);
+       KASSERT(n == 1);
+
+       pg = TAILQ_FIRST(&mlist);
+       KASSERT(pg != NULL);
+
+       pmap_zero_page(VM_PAGE_TO_PHYS(pg));
+
+       pg->flags |= PG_RDONLY;
+
+       mutex_enter(&uvm_pageqlock);
+       uvm_pagewire(pg);
+       mutex_exit(&uvm_pageqlock);
+
+       uvm_page_zeropage = pg;
+       return 0;
+}
+
 #if defined(DDB) || defined(DEBUGPRINT)
 
 /*
diff -r 252916ff7bd5 -r a4d4f68945fa sys/uvm/uvm_page.h
--- a/sys/uvm/uvm_page.h        Mon Nov 15 15:11:52 2010 +0000
+++ b/sys/uvm/uvm_page.h        Mon Nov 15 17:32:01 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_page.h,v 1.59.2.35 2010/11/12 08:13:40 uebayasi Exp $      */
+/*     $NetBSD: uvm_page.h,v 1.59.2.36 2010/11/15 17:32:01 uebayasi Exp $      */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -311,6 +311,9 @@
 
 int uvm_page_lookup_freelist(struct vm_page *);
 
+extern struct vm_page *uvm_page_zeropage;
+struct vm_page *uvm_page_zeropage_alloc(void);
+
 int vm_physseg_find(paddr_t, int *);
 struct vm_page *uvm_phys_to_vm_page(paddr_t);
 paddr_t uvm_vm_page_to_phys(const struct vm_page *);