1 /* $NetBSD: uvm_page_status.c,v 1.6 2020/08/14 09:06:15 chs Exp $ */
2
3 /*-
4 * Copyright (c)2011 YAMAMOTO Takashi,
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <sys/cdefs.h>
30 __KERNEL_RCSID(0, "$NetBSD: uvm_page_status.c,v 1.6 2020/08/14 09:06:15 chs Exp $");
31
32 #include <sys/param.h>
33 #include <sys/systm.h>
34
35 #include <uvm/uvm.h>
36
37 /*
38 * page dirtiness status tracking
39 *
40 * separated from uvm_page.c mainly for rump
41 */
42
43 /*
44 * these constants are chosen to match so that we can convert between
45 * them quickly.
46 */
47
48 __CTASSERT(UVM_PAGE_STATUS_UNKNOWN == 0);
49 __CTASSERT(UVM_PAGE_STATUS_DIRTY == PG_DIRTY);
50 __CTASSERT(UVM_PAGE_STATUS_CLEAN == PG_CLEAN);
51
52 /*
53 * uvm_pagegetdirty: return the dirtiness status (one of UVM_PAGE_STATUS_
54 * values) of the page.
55 *
56 * called with the owner locked.
57 */
58
59 unsigned int
uvm_pagegetdirty(struct vm_page * pg)60 uvm_pagegetdirty(struct vm_page *pg)
61 {
62 struct uvm_object * const uobj __diagused = pg->uobject;
63
64 KASSERT((~pg->flags & (PG_CLEAN|PG_DIRTY)) != 0);
65 KASSERT(uvm_page_owner_locked_p(pg, false));
66 KASSERT(uobj == NULL || ((pg->flags & PG_CLEAN) == 0) ==
67 uvm_obj_page_dirty_p(pg));
68 return pg->flags & (PG_CLEAN|PG_DIRTY);
69 }
70
71 /*
72 * uvm_pagemarkdirty: set the dirtiness status (one of UVM_PAGE_STATUS_ values)
73 * of the page.
74 *
75 * called with the owner locked.
76 *
77 * update the radix tree tag for object-owned page.
78 *
79 * if new status is UVM_PAGE_STATUS_UNKNOWN, clear pmap-level dirty bit
80 * so that later uvm_pagecheckdirty() can notice modifications on the page.
81 */
82
83 void
uvm_pagemarkdirty(struct vm_page * pg,unsigned int newstatus)84 uvm_pagemarkdirty(struct vm_page *pg, unsigned int newstatus)
85 {
86 struct uvm_object * const uobj = pg->uobject;
87 const unsigned int oldstatus = uvm_pagegetdirty(pg);
88 enum cpu_count base;
89
90 KASSERT((~newstatus & (PG_CLEAN|PG_DIRTY)) != 0);
91 KASSERT((newstatus & ~(PG_CLEAN|PG_DIRTY)) == 0);
92 KASSERT(uvm_page_owner_locked_p(pg, true));
93 KASSERT(uobj == NULL || ((pg->flags & PG_CLEAN) == 0) ==
94 uvm_obj_page_dirty_p(pg));
95
96 if (oldstatus == newstatus) {
97 return;
98 }
99
100 /*
101 * set UVM_PAGE_DIRTY_TAG tag unless known CLEAN so that putpages can
102 * find possibly-dirty pages quickly.
103 */
104
105 if (uobj != NULL) {
106 if (newstatus == UVM_PAGE_STATUS_CLEAN) {
107 uvm_obj_page_clear_dirty(pg);
108 } else if (oldstatus == UVM_PAGE_STATUS_CLEAN) {
109 /*
110 * on first dirty page, mark the object dirty.
111 * for vnodes this inserts to the syncer worklist.
112 */
113 if (uvm_obj_clean_p(uobj) &&
114 uobj->pgops->pgo_markdirty != NULL) {
115 (*uobj->pgops->pgo_markdirty)(uobj);
116 }
117 uvm_obj_page_set_dirty(pg);
118 }
119 }
120 if (newstatus == UVM_PAGE_STATUS_UNKNOWN) {
121 /*
122 * start relying on pmap-level dirtiness tracking.
123 */
124 pmap_clear_modify(pg);
125 }
126 pg->flags &= ~(PG_CLEAN|PG_DIRTY);
127 pg->flags |= newstatus;
128 KASSERT(uobj == NULL || ((pg->flags & PG_CLEAN) == 0) ==
129 uvm_obj_page_dirty_p(pg));
130 if ((pg->flags & PG_STAT) != 0) {
131 if ((pg->flags & PG_SWAPBACKED) != 0) {
132 base = CPU_COUNT_ANONUNKNOWN;
133 } else {
134 base = CPU_COUNT_FILEUNKNOWN;
135 }
136 kpreempt_disable();
137 CPU_COUNT(base + oldstatus, -1);
138 CPU_COUNT(base + newstatus, +1);
139 kpreempt_enable();
140 }
141 }
142
143 /*
144 * uvm_pagecheckdirty: check if page is dirty, and remove its dirty bit.
145 *
146 * called with the owner locked.
147 *
148 * returns if the page was dirty.
149 *
150 * if protected is true, mark the page CLEAN. otherwise, mark the page UNKNOWN.
151 * ("mark" in the sense of uvm_pagemarkdirty().)
152 */
153
154 bool
uvm_pagecheckdirty(struct vm_page * pg,bool pgprotected)155 uvm_pagecheckdirty(struct vm_page *pg, bool pgprotected)
156 {
157 const unsigned int oldstatus = uvm_pagegetdirty(pg);
158 bool modified;
159
160 KASSERT(uvm_page_owner_locked_p(pg, true));
161
162 /*
163 * if pgprotected is true, mark the page CLEAN.
164 * otherwise mark the page UNKNOWN unless it's CLEAN.
165 *
166 * possible transitions:
167 *
168 * CLEAN -> CLEAN , modified = false
169 * UNKNOWN -> UNKNOWN, modified = true
170 * UNKNOWN -> UNKNOWN, modified = false
171 * UNKNOWN -> CLEAN , modified = true
172 * UNKNOWN -> CLEAN , modified = false
173 * DIRTY -> UNKNOWN, modified = true
174 * DIRTY -> CLEAN , modified = true
175 *
176 * pmap_clear_modify is necessary if either of
177 * oldstatus or newstatus is UVM_PAGE_STATUS_UNKNOWN.
178 */
179
180 if (oldstatus == UVM_PAGE_STATUS_CLEAN) {
181 modified = false;
182 } else {
183 const unsigned int newstatus = pgprotected ?
184 UVM_PAGE_STATUS_CLEAN : UVM_PAGE_STATUS_UNKNOWN;
185
186 if (oldstatus == UVM_PAGE_STATUS_DIRTY) {
187 modified = true;
188 if (newstatus == UVM_PAGE_STATUS_UNKNOWN) {
189 pmap_clear_modify(pg);
190 }
191 } else {
192 KASSERT(oldstatus == UVM_PAGE_STATUS_UNKNOWN);
193 modified = pmap_clear_modify(pg);
194 }
195 uvm_pagemarkdirty(pg, newstatus);
196 }
197 return modified;
198 }
199