| 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 | |