1 | /* $NetBSD: uvm_anon.c,v 1.63 2013/10/25 20:08:11 martin 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 1.63 2013/10/25 20:08:11 martin 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 | |
42 | #include <uvm/uvm.h> |
43 | #include <uvm/uvm_swap.h> |
44 | #include <uvm/uvm_pdpolicy.h> |
45 | |
46 | static struct pool_cache uvm_anon_cache; |
47 | |
48 | static int uvm_anon_ctor(void *, void *, int); |
49 | |
50 | void |
51 | uvm_anon_init(void) |
52 | { |
53 | |
54 | pool_cache_bootstrap(&uvm_anon_cache, sizeof(struct vm_anon), 0, 0, |
55 | PR_LARGECACHE, "anonpl" , NULL, IPL_NONE, uvm_anon_ctor, |
56 | NULL, NULL); |
57 | } |
58 | |
59 | static int |
60 | uvm_anon_ctor(void *arg, void *object, int flags) |
61 | { |
62 | struct vm_anon *anon = object; |
63 | |
64 | anon->an_ref = 0; |
65 | anon->an_lock = NULL; |
66 | anon->an_page = NULL; |
67 | #if defined(VMSWAP) |
68 | anon->an_swslot = 0; |
69 | #endif |
70 | return 0; |
71 | } |
72 | |
73 | /* |
74 | * uvm_analloc: allocate a new anon. |
75 | * |
76 | * => anon will have no lock associated. |
77 | */ |
78 | struct vm_anon * |
79 | uvm_analloc(void) |
80 | { |
81 | struct vm_anon *anon; |
82 | |
83 | anon = pool_cache_get(&uvm_anon_cache, PR_NOWAIT); |
84 | if (anon) { |
85 | KASSERT(anon->an_ref == 0); |
86 | KASSERT(anon->an_lock == NULL); |
87 | KASSERT(anon->an_page == NULL); |
88 | #if defined(VMSWAP) |
89 | KASSERT(anon->an_swslot == 0); |
90 | #endif |
91 | anon->an_ref = 1; |
92 | } |
93 | return anon; |
94 | } |
95 | |
96 | /* |
97 | * uvm_anon_dispose: free any resident page or swap resources of anon. |
98 | * |
99 | * => anon must be removed from the amap (if anon was in an amap). |
100 | * => amap must be locked; we may drop and re-acquire the lock here. |
101 | */ |
102 | static bool |
103 | uvm_anon_dispose(struct vm_anon *anon) |
104 | { |
105 | struct vm_page *pg = anon->an_page; |
106 | |
107 | UVMHIST_FUNC("uvm_anon_dispose" ); UVMHIST_CALLED(maphist); |
108 | UVMHIST_LOG(maphist,"(anon=0x%x)" , anon, 0,0,0); |
109 | |
110 | KASSERT(mutex_owned(anon->an_lock)); |
111 | |
112 | /* |
113 | * If there is a resident page and it is loaned, then anon may not |
114 | * own it. Call out to uvm_anon_lockloanpg() to identify and lock |
115 | * the real owner of the page. |
116 | */ |
117 | |
118 | if (pg && pg->loan_count) { |
119 | KASSERT(anon->an_lock != NULL); |
120 | pg = uvm_anon_lockloanpg(anon); |
121 | } |
122 | |
123 | /* |
124 | * Dispose the page, if it is resident. |
125 | */ |
126 | |
127 | if (pg) { |
128 | KASSERT(anon->an_lock != NULL); |
129 | |
130 | /* |
131 | * If the page is owned by a UVM object (now locked), |
132 | * then kill the loan on the page rather than free it, |
133 | * and release the object lock. |
134 | */ |
135 | |
136 | if (pg->uobject) { |
137 | mutex_enter(&uvm_pageqlock); |
138 | KASSERT(pg->loan_count > 0); |
139 | pg->loan_count--; |
140 | pg->uanon = NULL; |
141 | mutex_exit(&uvm_pageqlock); |
142 | mutex_exit(pg->uobject->vmobjlock); |
143 | } else { |
144 | |
145 | /* |
146 | * If page has no UVM object, then anon is the owner, |
147 | * and it is already locked. |
148 | */ |
149 | |
150 | KASSERT((pg->flags & PG_RELEASED) == 0); |
151 | pmap_page_protect(pg, VM_PROT_NONE); |
152 | |
153 | /* |
154 | * If the page is busy, mark it as PG_RELEASED, so |
155 | * that uvm_anon_release(9) would release it later. |
156 | */ |
157 | |
158 | if (pg->flags & PG_BUSY) { |
159 | pg->flags |= PG_RELEASED; |
160 | mutex_obj_hold(anon->an_lock); |
161 | return false; |
162 | } |
163 | mutex_enter(&uvm_pageqlock); |
164 | uvm_pagefree(pg); |
165 | mutex_exit(&uvm_pageqlock); |
166 | UVMHIST_LOG(maphist, "anon 0x%x, page 0x%x: " |
167 | "freed now!" , anon, pg, 0, 0); |
168 | } |
169 | } |
170 | |
171 | #if defined(VMSWAP) |
172 | if (pg == NULL && anon->an_swslot > 0) { |
173 | /* This page is no longer only in swap. */ |
174 | mutex_enter(&uvm_swap_data_lock); |
175 | KASSERT(uvmexp.swpgonly > 0); |
176 | uvmexp.swpgonly--; |
177 | mutex_exit(&uvm_swap_data_lock); |
178 | } |
179 | #endif |
180 | |
181 | /* |
182 | * Free any swap resources, leave a page replacement hint. |
183 | */ |
184 | |
185 | uvm_anon_dropswap(anon); |
186 | uvmpdpol_anfree(anon); |
187 | UVMHIST_LOG(maphist,"<- done!" ,0,0,0,0); |
188 | return true; |
189 | } |
190 | |
191 | /* |
192 | * uvm_anon_free: free a single anon. |
193 | * |
194 | * => anon must be already disposed. |
195 | */ |
196 | void |
197 | uvm_anon_free(struct vm_anon *anon) |
198 | { |
199 | |
200 | KASSERT(anon->an_ref == 0); |
201 | KASSERT(anon->an_lock == NULL); |
202 | KASSERT(anon->an_page == NULL); |
203 | #if defined(VMSWAP) |
204 | KASSERT(anon->an_swslot == 0); |
205 | #endif |
206 | pool_cache_put(&uvm_anon_cache, anon); |
207 | } |
208 | |
209 | /* |
210 | * uvm_anon_freelst: free a linked list of anon structures. |
211 | * |
212 | * => anon must be locked, we will unlock it. |
213 | */ |
214 | void |
215 | uvm_anon_freelst(struct vm_amap *amap, struct vm_anon *anonlst) |
216 | { |
217 | struct vm_anon *anon; |
218 | struct vm_anon **anonp = &anonlst; |
219 | |
220 | KASSERT(mutex_owned(amap->am_lock)); |
221 | while ((anon = *anonp) != NULL) { |
222 | if (!uvm_anon_dispose(anon)) { |
223 | /* Do not free this anon. */ |
224 | *anonp = anon->an_link; |
225 | /* Note: clears an_ref as well. */ |
226 | anon->an_link = NULL; |
227 | } else { |
228 | anonp = &anon->an_link; |
229 | } |
230 | } |
231 | amap_unlock(amap); |
232 | |
233 | while (anonlst) { |
234 | anon = anonlst->an_link; |
235 | /* Note: clears an_ref as well. */ |
236 | anonlst->an_link = NULL; |
237 | anonlst->an_lock = NULL; |
238 | uvm_anon_free(anonlst); |
239 | anonlst = anon; |
240 | } |
241 | } |
242 | |
243 | /* |
244 | * uvm_anon_lockloanpg: given a locked anon, lock its resident page owner. |
245 | * |
246 | * => anon is locked by caller |
247 | * => on return: anon is locked |
248 | * if there is a resident page: |
249 | * if it has a uobject, it is locked by us |
250 | * if it is ownerless, we take over as owner |
251 | * we return the resident page (it can change during |
252 | * this function) |
253 | * => note that the only time an anon has an ownerless resident page |
254 | * is if the page was loaned from a uvm_object and the uvm_object |
255 | * disowned it |
256 | * => this only needs to be called when you want to do an operation |
257 | * on an anon's resident page and that page has a non-zero loan |
258 | * count. |
259 | */ |
260 | struct vm_page * |
261 | uvm_anon_lockloanpg(struct vm_anon *anon) |
262 | { |
263 | struct vm_page *pg; |
264 | bool locked = false; |
265 | |
266 | KASSERT(mutex_owned(anon->an_lock)); |
267 | |
268 | /* |
269 | * loop while we have a resident page that has a non-zero loan count. |
270 | * if we successfully get our lock, we will "break" the loop. |
271 | * note that the test for pg->loan_count is not protected -- this |
272 | * may produce false positive results. note that a false positive |
273 | * result may cause us to do more work than we need to, but it will |
274 | * not produce an incorrect result. |
275 | */ |
276 | |
277 | while (((pg = anon->an_page) != NULL) && pg->loan_count != 0) { |
278 | |
279 | /* |
280 | * quickly check to see if the page has an object before |
281 | * bothering to lock the page queues. this may also produce |
282 | * a false positive result, but that's ok because we do a real |
283 | * check after that. |
284 | */ |
285 | |
286 | if (pg->uobject) { |
287 | mutex_enter(&uvm_pageqlock); |
288 | if (pg->uobject) { |
289 | locked = |
290 | mutex_tryenter(pg->uobject->vmobjlock); |
291 | } else { |
292 | /* object disowned before we got PQ lock */ |
293 | locked = true; |
294 | } |
295 | mutex_exit(&uvm_pageqlock); |
296 | |
297 | /* |
298 | * if we didn't get a lock (try lock failed), then we |
299 | * toggle our anon lock and try again |
300 | */ |
301 | |
302 | if (!locked) { |
303 | /* |
304 | * someone locking the object has a chance to |
305 | * lock us right now |
306 | * |
307 | * XXX Better than yielding but inadequate. |
308 | */ |
309 | kpause("livelock" , false, 1, anon->an_lock); |
310 | continue; |
311 | } |
312 | } |
313 | |
314 | /* |
315 | * If page is un-owned i.e. the object dropped its ownership, |
316 | * then we have to take the ownership. |
317 | */ |
318 | |
319 | if (pg->uobject == NULL && (pg->pqflags & PQ_ANON) == 0) { |
320 | mutex_enter(&uvm_pageqlock); |
321 | pg->pqflags |= PQ_ANON; |
322 | pg->loan_count--; |
323 | mutex_exit(&uvm_pageqlock); |
324 | } |
325 | break; |
326 | } |
327 | return pg; |
328 | } |
329 | |
330 | #if defined(VMSWAP) |
331 | |
332 | /* |
333 | * uvm_anon_pagein: fetch an anon's page. |
334 | * |
335 | * => anon must be locked, and is unlocked upon return. |
336 | * => returns true if pagein was aborted due to lack of memory. |
337 | */ |
338 | |
339 | bool |
340 | uvm_anon_pagein(struct vm_amap *amap, struct vm_anon *anon) |
341 | { |
342 | struct vm_page *pg; |
343 | struct uvm_object *uobj; |
344 | |
345 | KASSERT(mutex_owned(anon->an_lock)); |
346 | KASSERT(anon->an_lock == amap->am_lock); |
347 | |
348 | /* |
349 | * Get the page of the anon. |
350 | */ |
351 | |
352 | switch (uvmfault_anonget(NULL, amap, anon)) { |
353 | case 0: |
354 | /* Success - we have the page. */ |
355 | KASSERT(mutex_owned(anon->an_lock)); |
356 | break; |
357 | case EIO: |
358 | case ERESTART: |
359 | /* |
360 | * Nothing more to do on errors. ERESTART means that the |
361 | * anon was freed. |
362 | */ |
363 | return false; |
364 | default: |
365 | return true; |
366 | } |
367 | |
368 | /* |
369 | * Mark the page as dirty, clear its swslot and un-busy it. |
370 | */ |
371 | |
372 | pg = anon->an_page; |
373 | uobj = pg->uobject; |
374 | if (anon->an_swslot > 0) { |
375 | uvm_swap_free(anon->an_swslot, 1); |
376 | } |
377 | anon->an_swslot = 0; |
378 | pg->flags &= ~PG_CLEAN; |
379 | |
380 | /* |
381 | * Deactivate the page (to put it on a page queue). |
382 | */ |
383 | |
384 | mutex_enter(&uvm_pageqlock); |
385 | if (pg->wire_count == 0) { |
386 | uvm_pagedeactivate(pg); |
387 | } |
388 | mutex_exit(&uvm_pageqlock); |
389 | |
390 | if (pg->flags & PG_WANTED) { |
391 | pg->flags &= ~PG_WANTED; |
392 | wakeup(pg); |
393 | } |
394 | |
395 | mutex_exit(anon->an_lock); |
396 | if (uobj) { |
397 | mutex_exit(uobj->vmobjlock); |
398 | } |
399 | return false; |
400 | } |
401 | |
402 | /* |
403 | * uvm_anon_dropswap: release any swap resources from this anon. |
404 | * |
405 | * => anon must be locked or have a reference count of 0. |
406 | */ |
407 | void |
408 | uvm_anon_dropswap(struct vm_anon *anon) |
409 | { |
410 | UVMHIST_FUNC("uvm_anon_dropswap" ); UVMHIST_CALLED(maphist); |
411 | |
412 | if (anon->an_swslot == 0) |
413 | return; |
414 | |
415 | UVMHIST_LOG(maphist,"freeing swap for anon %p, paged to swslot 0x%x" , |
416 | anon, anon->an_swslot, 0, 0); |
417 | uvm_swap_free(anon->an_swslot, 1); |
418 | anon->an_swslot = 0; |
419 | } |
420 | |
421 | #endif |
422 | |
423 | /* |
424 | * uvm_anon_release: release an anon and its page. |
425 | * |
426 | * => anon should not have any references. |
427 | * => anon must be locked. |
428 | */ |
429 | |
430 | void |
431 | uvm_anon_release(struct vm_anon *anon) |
432 | { |
433 | struct vm_page *pg = anon->an_page; |
434 | bool success __diagused; |
435 | |
436 | KASSERT(mutex_owned(anon->an_lock)); |
437 | KASSERT(pg != NULL); |
438 | KASSERT((pg->flags & PG_RELEASED) != 0); |
439 | KASSERT((pg->flags & PG_BUSY) != 0); |
440 | KASSERT(pg->uobject == NULL); |
441 | KASSERT(pg->uanon == anon); |
442 | KASSERT(pg->loan_count == 0); |
443 | KASSERT(anon->an_ref == 0); |
444 | |
445 | mutex_enter(&uvm_pageqlock); |
446 | uvm_pagefree(pg); |
447 | mutex_exit(&uvm_pageqlock); |
448 | KASSERT(anon->an_page == NULL); |
449 | /* dispose should succeed as no one can reach this anon anymore. */ |
450 | success = uvm_anon_dispose(anon); |
451 | KASSERT(success); |
452 | mutex_exit(anon->an_lock); |
453 | /* Note: extra reference is held for PG_RELEASED case. */ |
454 | mutex_obj_free(anon->an_lock); |
455 | anon->an_lock = NULL; |
456 | uvm_anon_free(anon); |
457 | } |
458 | |