1 /* $NetBSD: uvm_anon.c,v 1.58 2011/07/05 13:47:24 yamt 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 1.58 2011/07/05 13:47:24 yamt 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_page = NULL; 66 #if defined(VMSWAP) 67 anon->an_swslot = 0; 68 #endif 69 return 0; 70 } 71 72 /* 73 * uvm_analloc: allocate a new anon. 74 * 75 * => anon will have no lock associated. 76 */ 77 struct vm_anon * 78 uvm_analloc(void) 79 { 80 struct vm_anon *anon; 81 82 anon = pool_cache_get(&uvm_anon_cache, PR_NOWAIT); 83 if (anon) { 84 KASSERT(anon->an_ref == 0); 85 KASSERT(anon->an_page == NULL); 86 #if defined(VMSWAP) 87 KASSERT(anon->an_swslot == 0); 88 #endif 89 anon->an_ref = 1; 90 anon->an_lock = NULL; 91 } 92 return anon; 93 } 94 95 /* 96 * uvm_anfree1: free a single anon. 97 * 98 * => anon must be removed from the amap (if anon was in an amap). 99 * => amap must be locked or anon must not be associated. 100 * => amap lock may be dropped and re-acquired here. 101 */ 102 103 static void 104 uvm_anfree1(struct vm_anon *anon) 105 { 106 struct vm_page *pg = anon->an_page; 107 108 UVMHIST_FUNC("uvm_anfree"); UVMHIST_CALLED(maphist); 109 UVMHIST_LOG(maphist,"(anon=0x%x)", anon, 0,0,0); 110 111 KASSERT(anon->an_lock == NULL || mutex_owned(anon->an_lock)); 112 113 /* 114 * If there is a resident page and it is loaned, then anon may not 115 * own it. Call out to uvm_anon_lockloanpg() to identify and lock 116 * the real owner of the page. 117 */ 118 119 if (pg && pg->loan_count) { 120 KASSERT(anon->an_lock != NULL); 121 pg = uvm_anon_lockloanpg(anon); 122 } 123 124 /* 125 * Dispose the page, if it is resident. 126 */ 127 128 if (pg) { 129 KASSERT(anon->an_lock != NULL); 130 131 /* 132 * If the page is owned by a UVM object (now locked), 133 * then kill the loan on the page rather than free it, 134 * and release the object lock. 135 */ 136 137 if (pg->uobject) { 138 mutex_enter(&uvm_pageqlock); 139 KASSERT(pg->loan_count > 0); 140 pg->loan_count--; 141 pg->uanon = NULL; 142 mutex_exit(&uvm_pageqlock); 143 mutex_exit(pg->uobject->vmobjlock); 144 } else { 145 146 /* 147 * If page has no UVM object, then anon is the owner, 148 * and it is already locked. 149 */ 150 151 KASSERT((pg->flags & PG_RELEASED) == 0); 152 pmap_page_protect(pg, VM_PROT_NONE); 153 154 /* 155 * If the page is busy, mark it as PG_RELEASED, so 156 * that uvm_anon_release(9) would release it later. 157 */ 158 159 if (pg->flags & PG_BUSY) { 160 pg->flags |= PG_RELEASED; 161 mutex_obj_hold(anon->an_lock); 162 return; 163 } 164 mutex_enter(&uvm_pageqlock); 165 uvm_pagefree(pg); 166 mutex_exit(&uvm_pageqlock); 167 UVMHIST_LOG(maphist, "anon 0x%x, page 0x%x: " 168 "freed now!", anon, pg, 0, 0); 169 } 170 } 171 172 #if defined(VMSWAP) 173 if (pg == NULL && anon->an_swslot > 0) { 174 /* This page is no longer only in swap. */ 175 mutex_enter(&uvm_swap_data_lock); 176 KASSERT(uvmexp.swpgonly > 0); 177 uvmexp.swpgonly--; 178 mutex_exit(&uvm_swap_data_lock); 179 } 180 #endif 181 182 /* 183 * Free any swap resources, leave a page replacement hint, drop 184 * the reference on lock and finally destroy the anon itself. 185 */ 186 187 uvm_anon_dropswap(anon); 188 uvmpdpol_anfree(anon); 189 190 KASSERT(anon->an_page == NULL); 191 #if defined(VMSWAP) 192 KASSERT(anon->an_swslot == 0); 193 #endif 194 195 pool_cache_put(&uvm_anon_cache, anon); 196 UVMHIST_LOG(maphist,"<- done!",0,0,0,0); 197 } 198 199 /* 200 * uvm_anfree: free a linked list of anon structures. 201 */ 202 void 203 uvm_anfree(struct vm_anon *anon) 204 { 205 struct vm_anon *next; 206 207 for (; anon != NULL; anon = next) { 208 /* Note: clearing an_link also clears a reference count. */ 209 next = anon->an_link; 210 anon->an_link = NULL; 211 uvm_anfree1(anon); 212 } 213 } 214 215 /* 216 * uvm_anon_lockloanpg: given a locked anon, lock its resident page owner. 217 * 218 * => anon is locked by caller 219 * => on return: anon is locked 220 * if there is a resident page: 221 * if it has a uobject, it is locked by us 222 * if it is ownerless, we take over as owner 223 * we return the resident page (it can change during 224 * this function) 225 * => note that the only time an anon has an ownerless resident page 226 * is if the page was loaned from a uvm_object and the uvm_object 227 * disowned it 228 * => this only needs to be called when you want to do an operation 229 * on an anon's resident page and that page has a non-zero loan 230 * count. 231 */ 232 struct vm_page * 233 uvm_anon_lockloanpg(struct vm_anon *anon) 234 { 235 struct vm_page *pg; 236 bool locked = false; 237 238 KASSERT(mutex_owned(anon->an_lock)); 239 240 /* 241 * loop while we have a resident page that has a non-zero loan count. 242 * if we successfully get our lock, we will "break" the loop. 243 * note that the test for pg->loan_count is not protected -- this 244 * may produce false positive results. note that a false positive 245 * result may cause us to do more work than we need to, but it will 246 * not produce an incorrect result. 247 */ 248 249 while (((pg = anon->an_page) != NULL) && pg->loan_count != 0) { 250 251 /* 252 * quickly check to see if the page has an object before 253 * bothering to lock the page queues. this may also produce 254 * a false positive result, but that's ok because we do a real 255 * check after that. 256 */ 257 258 if (pg->uobject) { 259 mutex_enter(&uvm_pageqlock); 260 if (pg->uobject) { 261 locked = 262 mutex_tryenter(pg->uobject->vmobjlock); 263 } else { 264 /* object disowned before we got PQ lock */ 265 locked = true; 266 } 267 mutex_exit(&uvm_pageqlock); 268 269 /* 270 * if we didn't get a lock (try lock failed), then we 271 * toggle our anon lock and try again 272 */ 273 274 if (!locked) { 275 /* 276 * someone locking the object has a chance to 277 * lock us right now 278 * 279 * XXX Better than yielding but inadequate. 280 */ 281 kpause("livelock", false, 1, anon->an_lock); 282 continue; 283 } 284 } 285 286 /* 287 * If page is un-owned i.e. the object dropped its ownership, 288 * then we have to take the ownership. 289 */ 290 291 if (pg->uobject == NULL && (pg->pqflags & PQ_ANON) == 0) { 292 mutex_enter(&uvm_pageqlock); 293 pg->pqflags |= PQ_ANON; 294 pg->loan_count--; 295 mutex_exit(&uvm_pageqlock); 296 } 297 break; 298 } 299 return pg; 300 } 301 302 #if defined(VMSWAP) 303 304 /* 305 * uvm_anon_pagein: fetch an anon's page. 306 * 307 * => anon must be locked, and is unlocked upon return. 308 * => returns true if pagein was aborted due to lack of memory. 309 */ 310 311 bool 312 uvm_anon_pagein(struct vm_amap *amap, struct vm_anon *anon) 313 { 314 struct vm_page *pg; 315 struct uvm_object *uobj; 316 317 KASSERT(mutex_owned(anon->an_lock)); 318 KASSERT(anon->an_lock == amap->am_lock); 319 320 /* 321 * Get the page of the anon. 322 */ 323 324 switch (uvmfault_anonget(NULL, amap, anon)) { 325 case 0: 326 /* Success - we have the page. */ 327 KASSERT(mutex_owned(anon->an_lock)); 328 break; 329 case EIO: 330 case ERESTART: 331 /* 332 * Nothing more to do on errors. ERESTART means that the 333 * anon was freed. 334 */ 335 return false; 336 default: 337 return true; 338 } 339 340 /* 341 * Mark the page as dirty, clear its swslot and un-busy it. 342 */ 343 344 pg = anon->an_page; 345 uobj = pg->uobject; 346 if (anon->an_swslot > 0) { 347 uvm_swap_free(anon->an_swslot, 1); 348 } 349 anon->an_swslot = 0; 350 pg->flags &= ~PG_CLEAN; 351 352 /* 353 * Deactivate the page (to put it on a page queue). 354 */ 355 356 mutex_enter(&uvm_pageqlock); 357 if (pg->wire_count == 0) { 358 uvm_pagedeactivate(pg); 359 } 360 mutex_exit(&uvm_pageqlock); 361 362 if (pg->flags & PG_WANTED) { 363 pg->flags &= ~PG_WANTED; 364 wakeup(pg); 365 } 366 367 mutex_exit(anon->an_lock); 368 if (uobj) { 369 mutex_exit(uobj->vmobjlock); 370 } 371 return false; 372 } 373 374 /* 375 * uvm_anon_dropswap: release any swap resources from this anon. 376 * 377 * => anon must be locked or have a reference count of 0. 378 */ 379 void 380 uvm_anon_dropswap(struct vm_anon *anon) 381 { 382 UVMHIST_FUNC("uvm_anon_dropswap"); UVMHIST_CALLED(maphist); 383 384 if (anon->an_swslot == 0) 385 return; 386 387 UVMHIST_LOG(maphist,"freeing swap for anon %p, paged to swslot 0x%x", 388 anon, anon->an_swslot, 0, 0); 389 uvm_swap_free(anon->an_swslot, 1); 390 anon->an_swslot = 0; 391 } 392 393 #endif 394 395 /* 396 * uvm_anon_release: release an anon and its page. 397 * 398 * => anon should not have any references. 399 * => anon must be locked. 400 */ 401 402 void 403 uvm_anon_release(struct vm_anon *anon) 404 { 405 struct vm_page *pg = anon->an_page; 406 kmutex_t *lock = anon->an_lock; 407 408 KASSERT(mutex_owned(lock)); 409 KASSERT(pg != NULL); 410 KASSERT((pg->flags & PG_RELEASED) != 0); 411 KASSERT((pg->flags & PG_BUSY) != 0); 412 KASSERT(pg->uobject == NULL); 413 KASSERT(pg->uanon == anon); 414 KASSERT(pg->loan_count == 0); 415 KASSERT(anon->an_ref == 0); 416 417 mutex_enter(&uvm_pageqlock); 418 uvm_pagefree(pg); 419 mutex_exit(&uvm_pageqlock); 420 421 KASSERT(anon->an_page == NULL); 422 423 uvm_anfree(anon); 424 mutex_exit(lock); 425 mutex_obj_free(lock); 426 } 427