1 /* $NetBSD: uvm_anon.c,v 1.80 2020/10/25 00:05:26 chs Exp $ */
2
3 /*
4 * Copyright (c) 1997 Charles D. Cranor and Washington University.
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 ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 /*
29 * uvm_anon.c: uvm anon ops
30 */
31
32 #include <sys/cdefs.h>
33 __KERNEL_RCSID(0, "$NetBSD: uvm_anon.c,v 1.80 2020/10/25 00:05:26 chs Exp $");
34
35 #include "opt_uvmhist.h"
36
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/pool.h>
40 #include <sys/kernel.h>
41 #include <sys/atomic.h>
42
43 #include <uvm/uvm.h>
44 #include <uvm/uvm_swap.h>
45 #include <uvm/uvm_pdpolicy.h>
46
47 static struct pool_cache uvm_anon_cache;
48
49 static int uvm_anon_ctor(void *, void *, int);
50
51 void
uvm_anon_init(void)52 uvm_anon_init(void)
53 {
54
55 pool_cache_bootstrap(&uvm_anon_cache, sizeof(struct vm_anon), 0, 0,
56 PR_LARGECACHE, "anonpl", NULL, IPL_NONE, uvm_anon_ctor,
57 NULL, NULL);
58 }
59
60 static int
uvm_anon_ctor(void * arg,void * object,int flags)61 uvm_anon_ctor(void *arg, void *object, int flags)
62 {
63 struct vm_anon *anon = object;
64
65 anon->an_ref = 0;
66 anon->an_lock = NULL;
67 anon->an_page = NULL;
68 #if defined(VMSWAP)
69 anon->an_swslot = 0;
70 #endif
71 return 0;
72 }
73
74 /*
75 * uvm_analloc: allocate a new anon.
76 *
77 * => anon will have no lock associated.
78 */
79 struct vm_anon *
uvm_analloc(void)80 uvm_analloc(void)
81 {
82 struct vm_anon *anon;
83
84 anon = pool_cache_get(&uvm_anon_cache, PR_NOWAIT);
85 if (anon) {
86 KASSERT(anon->an_ref == 0);
87 KASSERT(anon->an_lock == NULL);
88 KASSERT(anon->an_page == NULL);
89 #if defined(VMSWAP)
90 KASSERT(anon->an_swslot == 0);
91 #endif
92 anon->an_ref = 1;
93 }
94 return anon;
95 }
96
97 /*
98 * uvm_anfree: free a single anon structure
99 *
100 * => anon must be removed from the amap (if anon was in an amap).
101 * => amap must be locked, if anon was owned by amap.
102 * => we may drop and re-acquire the lock here (to break loans).
103 */
104 void
uvm_anfree(struct vm_anon * anon)105 uvm_anfree(struct vm_anon *anon)
106 {
107 struct vm_page *pg = anon->an_page, *pg2 __diagused;
108
109 UVMHIST_FUNC(__func__);
110 UVMHIST_CALLARGS(maphist,"(anon=%#jx)", (uintptr_t)anon, 0,0,0);
111
112 KASSERT(anon->an_lock == NULL || rw_write_held(anon->an_lock));
113 KASSERT(anon->an_ref == 0);
114
115 /*
116 * Dispose of the page, if it is resident.
117 */
118
119 if (__predict_true(pg != NULL)) {
120 KASSERT(anon->an_lock != NULL);
121
122 /*
123 * If there is a resident page and it is loaned, then anon
124 * may not own it. Call out to uvm_anon_lockloanpg() to
125 * identify and lock the real owner of the page.
126 */
127
128 if (__predict_false(pg->loan_count != 0)) {
129 pg2 = uvm_anon_lockloanpg(anon);
130 KASSERT(pg2 == pg);
131 }
132
133 /*
134 * If the page is owned by a UVM object (now locked),
135 * then kill the loan on the page rather than free it,
136 * and release the object lock.
137 */
138
139 if (__predict_false(pg->uobject != NULL)) {
140 mutex_enter(&pg->interlock);
141 KASSERT(pg->loan_count > 0);
142 pg->loan_count--;
143 pg->uanon = NULL;
144 mutex_exit(&pg->interlock);
145 rw_exit(pg->uobject->vmobjlock);
146 } else {
147
148 /*
149 * If page has no UVM object, then anon is the owner,
150 * and it is already locked.
151 */
152
153 KASSERT((pg->flags & PG_RELEASED) == 0);
154 pmap_page_protect(pg, VM_PROT_NONE);
155
156 /*
157 * If the page is busy, mark it as PG_RELEASED, so
158 * that uvm_anon_release(9) would release it later.
159 */
160
161 if (__predict_false((pg->flags & PG_BUSY) != 0)) {
162 pg->flags |= PG_RELEASED;
163 rw_obj_hold(anon->an_lock);
164 return;
165 }
166 uvm_pagefree(pg);
167 UVMHIST_LOG(maphist, "anon %#jx, page %#jx: "
168 "freed now!", (uintptr_t)anon, (uintptr_t)pg,
169 0, 0);
170 }
171 } else {
172 #if defined(VMSWAP)
173 if (anon->an_swslot > 0) {
174 /* This page is no longer only in swap. */
175 KASSERT(uvmexp.swpgonly > 0);
176 atomic_dec_uint(&uvmexp.swpgonly);
177 }
178 #endif
179 }
180 anon->an_lock = NULL;
181
182 /*
183 * Free any swap resources, leave a page replacement hint.
184 */
185
186 uvm_anon_dropswap(anon);
187 uvmpdpol_anfree(anon);
188 UVMHIST_LOG(maphist,"<- done!",0,0,0,0);
189 pool_cache_put(&uvm_anon_cache, anon);
190 }
191
192 /*
193 * uvm_anon_lockloanpg: given a locked anon, lock its resident page owner.
194 *
195 * => anon is locked by caller
196 * => on return: anon is locked
197 * if there is a resident page:
198 * if it has a uobject, it is locked by us
199 * if it is ownerless, we take over as owner
200 * we return the resident page (it can change during
201 * this function)
202 * => note that the only time an anon has an ownerless resident page
203 * is if the page was loaned from a uvm_object and the uvm_object
204 * disowned it
205 * => this only needs to be called when you want to do an operation
206 * on an anon's resident page and that page has a non-zero loan
207 * count.
208 */
209 struct vm_page *
uvm_anon_lockloanpg(struct vm_anon * anon)210 uvm_anon_lockloanpg(struct vm_anon *anon)
211 {
212 struct vm_page *pg;
213 krw_t op;
214
215 KASSERT(rw_lock_held(anon->an_lock));
216
217 /*
218 * loop while we have a resident page that has a non-zero loan count.
219 * if we successfully get our lock, we will "break" the loop.
220 * note that the test for pg->loan_count is not protected -- this
221 * may produce false positive results. note that a false positive
222 * result may cause us to do more work than we need to, but it will
223 * not produce an incorrect result.
224 */
225
226 while (((pg = anon->an_page) != NULL) && pg->loan_count != 0) {
227 mutex_enter(&pg->interlock);
228 if (pg->uobject) {
229 /*
230 * if we didn't get a lock (try lock failed), then we
231 * toggle our anon lock and try again
232 */
233
234 if (!rw_tryenter(pg->uobject->vmobjlock, RW_WRITER)) {
235 /*
236 * someone locking the object has a chance to
237 * lock us right now
238 *
239 * XXX Better than yielding but inadequate.
240 */
241 mutex_exit(&pg->interlock);
242 op = rw_lock_op(anon->an_lock);
243 rw_exit(anon->an_lock);
244 kpause("lkloanpg", false, 1, NULL);
245 rw_enter(anon->an_lock, op);
246 continue;
247 }
248 }
249
250 /*
251 * If page is un-owned i.e. the object dropped its ownership,
252 * then we have to take the ownership.
253 */
254
255 if (pg->uobject == NULL && (pg->flags & PG_ANON) == 0) {
256 pg->flags |= PG_ANON;
257 pg->loan_count--;
258 }
259 mutex_exit(&pg->interlock);
260 break;
261 }
262 return pg;
263 }
264
265 #if defined(VMSWAP)
266
267 /*
268 * uvm_anon_pagein: fetch an anon's page.
269 *
270 * => anon must be locked, and is unlocked upon return.
271 * => returns true if pagein was aborted due to lack of memory.
272 */
273
274 bool
uvm_anon_pagein(struct vm_amap * amap,struct vm_anon * anon)275 uvm_anon_pagein(struct vm_amap *amap, struct vm_anon *anon)
276 {
277 struct vm_page *pg;
278 struct uvm_object *uobj;
279
280 KASSERT(rw_write_held(anon->an_lock));
281 KASSERT(anon->an_lock == amap->am_lock);
282
283 /*
284 * Get the page of the anon.
285 */
286
287 switch (uvmfault_anonget(NULL, amap, anon)) {
288 case 0:
289 /* Success - we have the page. */
290 KASSERT(rw_write_held(anon->an_lock));
291 break;
292 case EIO:
293 case ERESTART:
294 /*
295 * Nothing more to do on errors. ERESTART means that the
296 * anon was freed.
297 */
298 return false;
299 case ENOLCK:
300 panic("uvm_anon_pagein");
301 default:
302 return true;
303 }
304
305 /*
306 * Mark the page as dirty and clear its swslot.
307 */
308
309 pg = anon->an_page;
310 uobj = pg->uobject;
311 if (anon->an_swslot > 0) {
312 uvm_swap_free(anon->an_swslot, 1);
313 }
314 anon->an_swslot = 0;
315 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY);
316
317 /*
318 * Deactivate the page (to put it on a page queue).
319 */
320
321 uvm_pagelock(pg);
322 uvm_pagedeactivate(pg);
323 uvm_pageunlock(pg);
324 rw_exit(anon->an_lock);
325 if (uobj) {
326 rw_exit(uobj->vmobjlock);
327 }
328 return false;
329 }
330
331 /*
332 * uvm_anon_dropswap: release any swap resources from this anon.
333 *
334 * => anon must be locked or have a reference count of 0.
335 */
336 void
uvm_anon_dropswap(struct vm_anon * anon)337 uvm_anon_dropswap(struct vm_anon *anon)
338 {
339 UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);
340
341 if (anon->an_swslot == 0)
342 return;
343
344 UVMHIST_LOG(maphist,"freeing swap for anon %#jx, paged to swslot %#jx",
345 (uintptr_t)anon, anon->an_swslot, 0, 0);
346 uvm_swap_free(anon->an_swslot, 1);
347 anon->an_swslot = 0;
348 }
349
350 #endif
351
352 /*
353 * uvm_anon_release: release an anon and its page.
354 *
355 * => anon should not have any references.
356 * => anon must be locked.
357 */
358
359 void
uvm_anon_release(struct vm_anon * anon)360 uvm_anon_release(struct vm_anon *anon)
361 {
362 struct vm_page *pg = anon->an_page;
363 krwlock_t *lock;
364
365 KASSERT(rw_write_held(anon->an_lock));
366 KASSERT(pg != NULL);
367 KASSERT((pg->flags & PG_RELEASED) != 0);
368 KASSERT((pg->flags & PG_BUSY) != 0);
369 KASSERT(pg->uobject == NULL);
370 KASSERT(pg->uanon == anon);
371 KASSERT(pg->loan_count == 0);
372 KASSERT(anon->an_ref == 0);
373
374 if ((pg->flags & PG_PAGEOUT) != 0) {
375 pg->flags &= ~PG_PAGEOUT;
376 uvm_pageout_done(1);
377 }
378
379 uvm_pagefree(pg);
380 KASSERT(anon->an_page == NULL);
381 lock = anon->an_lock;
382 uvm_anfree(anon);
383 rw_exit(lock);
384 /* Note: extra reference is held for PG_RELEASED case. */
385 rw_obj_free(lock);
386 }
387