1 /* $NetBSD: uvm_loan.c,v 1.87 2018/05/25 20:11:03 jdolecek 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 * from: Id: uvm_loan.c,v 1.1.6.4 1998/02/06 05:08:43 chs Exp 28 */ 29 30 /* 31 * uvm_loan.c: page loanout handler 32 */ 33 34 #include <sys/cdefs.h> 35 __KERNEL_RCSID(0, "$NetBSD: uvm_loan.c,v 1.87 2018/05/25 20:11:03 jdolecek Exp $"); 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/kernel.h> 40 #include <sys/mman.h> 41 42 #include <uvm/uvm.h> 43 44 #ifdef UVMHIST 45 UVMHIST_DEFINE(loanhist); 46 #endif 47 48 /* 49 * "loaned" pages are pages which are (read-only, copy-on-write) loaned 50 * from the VM system to other parts of the kernel. this allows page 51 * copying to be avoided (e.g. you can loan pages from objs/anons to 52 * the mbuf system). 53 * 54 * there are 3 types of loans possible: 55 * O->K uvm_object page to wired kernel page (e.g. mbuf data area) 56 * A->K anon page to wired kernel page (e.g. mbuf data area) 57 * O->A uvm_object to anon loan (e.g. vnode page to an anon) 58 * note that it possible to have an O page loaned to both an A and K 59 * at the same time. 60 * 61 * loans are tracked by pg->loan_count. an O->A page will have both 62 * a uvm_object and a vm_anon, but PQ_ANON will not be set. this sort 63 * of page is considered "owned" by the uvm_object (not the anon). 64 * 65 * each loan of a page to the kernel bumps the pg->wire_count. the 66 * kernel mappings for these pages will be read-only and wired. since 67 * the page will also be wired, it will not be a candidate for pageout, 68 * and thus will never be pmap_page_protect()'d with VM_PROT_NONE. a 69 * write fault in the kernel to one of these pages will not cause 70 * copy-on-write. instead, the page fault is considered fatal. this 71 * is because the kernel mapping will have no way to look up the 72 * object/anon which the page is owned by. this is a good side-effect, 73 * since a kernel write to a loaned page is an error. 74 * 75 * owners that want to free their pages and discover that they are 76 * loaned out simply "disown" them (the page becomes an orphan). these 77 * pages should be freed when the last loan is dropped. in some cases 78 * an anon may "adopt" an orphaned page. 79 * 80 * locking: to read pg->loan_count either the owner or the page queues 81 * must be locked. to modify pg->loan_count, both the owner of the page 82 * and the PQs must be locked. pg->flags is (as always) locked by 83 * the owner of the page. 84 * 85 * note that locking from the "loaned" side is tricky since the object 86 * getting the loaned page has no reference to the page's owner and thus 87 * the owner could "die" at any time. in order to prevent the owner 88 * from dying the page queues should be locked. this forces us to sometimes 89 * use "try" locking. 90 * 91 * loans are typically broken by the following events: 92 * 1. user-level xwrite fault to a loaned page 93 * 2. pageout of clean+inactive O->A loaned page 94 * 3. owner frees page (e.g. pager flush) 95 * 96 * note that loaning a page causes all mappings of the page to become 97 * read-only (via pmap_page_protect). this could have an unexpected 98 * effect on normal "wired" pages if one is not careful (XXX). 99 */ 100 101 /* 102 * local prototypes 103 */ 104 105 static int uvm_loananon(struct uvm_faultinfo *, void ***, 106 int, struct vm_anon *); 107 static int uvm_loanuobj(struct uvm_faultinfo *, void ***, 108 int, vaddr_t); 109 static int uvm_loanzero(struct uvm_faultinfo *, void ***, int); 110 static void uvm_unloananon(struct vm_anon **, int); 111 static void uvm_unloanpage(struct vm_page **, int); 112 static int uvm_loanpage(struct vm_page **, int); 113 114 115 /* 116 * inlines 117 */ 118 119 /* 120 * uvm_loanentry: loan out pages in a map entry (helper fn for uvm_loan()) 121 * 122 * => "ufi" is the result of a successful map lookup (meaning that 123 * on entry the map is locked by the caller) 124 * => we may unlock and then relock the map if needed (for I/O) 125 * => we put our output result in "output" 126 * => we always return with the map unlocked 127 * => possible return values: 128 * -1 == error, map is unlocked 129 * 0 == map relock error (try again!), map is unlocked 130 * >0 == number of pages we loaned, map is unlocked 131 * 132 * NOTE: We can live with this being an inline, because it is only called 133 * from one place. 134 */ 135 136 static inline int 137 uvm_loanentry(struct uvm_faultinfo *ufi, void ***output, int flags) 138 { 139 vaddr_t curaddr = ufi->orig_rvaddr; 140 vsize_t togo = ufi->size; 141 struct vm_aref *aref = &ufi->entry->aref; 142 struct uvm_object *uobj = ufi->entry->object.uvm_obj; 143 struct vm_anon *anon; 144 int rv, result = 0; 145 146 UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist); 147 148 /* 149 * lock us the rest of the way down (we unlock before return) 150 */ 151 if (aref->ar_amap) { 152 amap_lock(aref->ar_amap); 153 } 154 155 /* 156 * loop until done 157 */ 158 while (togo) { 159 160 /* 161 * find the page we want. check the anon layer first. 162 */ 163 164 if (aref->ar_amap) { 165 anon = amap_lookup(aref, curaddr - ufi->entry->start); 166 } else { 167 anon = NULL; 168 } 169 170 /* locked: map, amap, uobj */ 171 if (anon) { 172 rv = uvm_loananon(ufi, output, flags, anon); 173 } else if (uobj) { 174 rv = uvm_loanuobj(ufi, output, flags, curaddr); 175 } else if (UVM_ET_ISCOPYONWRITE(ufi->entry)) { 176 rv = uvm_loanzero(ufi, output, flags); 177 } else { 178 uvmfault_unlockall(ufi, aref->ar_amap, uobj); 179 rv = -1; 180 } 181 /* locked: if (rv > 0) => map, amap, uobj [o.w. unlocked] */ 182 KASSERT(rv > 0 || aref->ar_amap == NULL || 183 !mutex_owned(aref->ar_amap->am_lock)); 184 KASSERT(rv > 0 || uobj == NULL || 185 !mutex_owned(uobj->vmobjlock)); 186 187 /* total failure */ 188 if (rv < 0) { 189 UVMHIST_LOG(loanhist, "failure %jd", rv, 0,0,0); 190 return (-1); 191 } 192 193 /* relock failed, need to do another lookup */ 194 if (rv == 0) { 195 UVMHIST_LOG(loanhist, "relock failure %jd", result 196 ,0,0,0); 197 return (result); 198 } 199 200 /* 201 * got it... advance to next page 202 */ 203 204 result++; 205 togo -= PAGE_SIZE; 206 curaddr += PAGE_SIZE; 207 } 208 209 /* 210 * unlock what we locked, unlock the maps and return 211 */ 212 213 if (aref->ar_amap) { 214 amap_unlock(aref->ar_amap); 215 } 216 uvmfault_unlockmaps(ufi, false); 217 UVMHIST_LOG(loanhist, "done %jd", result, 0,0,0); 218 return (result); 219 } 220 221 /* 222 * normal functions 223 */ 224 225 /* 226 * uvm_loan: loan pages in a map out to anons or to the kernel 227 * 228 * => map should be unlocked 229 * => start and len should be multiples of PAGE_SIZE 230 * => result is either an array of anon's or vm_pages (depending on flags) 231 * => flag values: UVM_LOAN_TOANON - loan to anons 232 * UVM_LOAN_TOPAGE - loan to wired kernel page 233 * one and only one of these flags must be set! 234 * => returns 0 (success), or an appropriate error number 235 */ 236 237 int 238 uvm_loan(struct vm_map *map, vaddr_t start, vsize_t len, void *v, int flags) 239 { 240 struct uvm_faultinfo ufi; 241 void **result, **output; 242 int rv, error; 243 244 UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist); 245 246 /* 247 * ensure that one and only one of the flags is set 248 */ 249 250 KASSERT(((flags & UVM_LOAN_TOANON) == 0) ^ 251 ((flags & UVM_LOAN_TOPAGE) == 0)); 252 253 /* 254 * "output" is a pointer to the current place to put the loaned page. 255 */ 256 257 result = v; 258 output = &result[0]; /* start at the beginning ... */ 259 260 /* 261 * while we've got pages to do 262 */ 263 264 while (len > 0) { 265 266 /* 267 * fill in params for a call to uvmfault_lookup 268 */ 269 270 ufi.orig_map = map; 271 ufi.orig_rvaddr = start; 272 ufi.orig_size = len; 273 274 /* 275 * do the lookup, the only time this will fail is if we hit on 276 * an unmapped region (an error) 277 */ 278 279 if (!uvmfault_lookup(&ufi, false)) { 280 error = ENOENT; 281 goto fail; 282 } 283 284 /* 285 * map now locked. now do the loanout... 286 */ 287 288 rv = uvm_loanentry(&ufi, &output, flags); 289 if (rv < 0) { 290 /* all unlocked due to error */ 291 error = EINVAL; 292 goto fail; 293 } 294 295 /* 296 * done! the map is unlocked. advance, if possible. 297 * 298 * XXXCDC: could be recoded to hold the map lock with 299 * smarter code (but it only happens on map entry 300 * boundaries, so it isn't that bad). 301 */ 302 303 if (rv) { 304 rv <<= PAGE_SHIFT; 305 len -= rv; 306 start += rv; 307 } 308 } 309 UVMHIST_LOG(loanhist, "success", 0,0,0,0); 310 return 0; 311 312 fail: 313 /* 314 * failed to complete loans. drop any loans and return failure code. 315 * map is already unlocked. 316 */ 317 318 if (output - result) { 319 if (flags & UVM_LOAN_TOANON) { 320 uvm_unloananon((struct vm_anon **)result, 321 output - result); 322 } else { 323 uvm_unloanpage((struct vm_page **)result, 324 output - result); 325 } 326 } 327 UVMHIST_LOG(loanhist, "error %jd", error,0,0,0); 328 return (error); 329 } 330 331 /* 332 * uvm_loananon: loan a page from an anon out 333 * 334 * => called with map, amap, uobj locked 335 * => return value: 336 * -1 = fatal error, everything is unlocked, abort. 337 * 0 = lookup in ufi went stale, everything unlocked, relookup and 338 * try again 339 * 1 = got it, everything still locked 340 */ 341 342 int 343 uvm_loananon(struct uvm_faultinfo *ufi, void ***output, int flags, 344 struct vm_anon *anon) 345 { 346 struct vm_page *pg; 347 int error; 348 349 UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist); 350 351 /* 352 * if we are loaning to "another" anon then it is easy, we just 353 * bump the reference count on the current anon and return a 354 * pointer to it (it becomes copy-on-write shared). 355 */ 356 357 if (flags & UVM_LOAN_TOANON) { 358 KASSERT(mutex_owned(anon->an_lock)); 359 pg = anon->an_page; 360 if (pg && (pg->pqflags & PQ_ANON) != 0 && anon->an_ref == 1) { 361 if (pg->wire_count > 0) { 362 UVMHIST_LOG(loanhist, "->A wired %#jx", 363 (uintptr_t)pg, 0, 0, 0); 364 uvmfault_unlockall(ufi, 365 ufi->entry->aref.ar_amap, 366 ufi->entry->object.uvm_obj); 367 return (-1); 368 } 369 pmap_page_protect(pg, VM_PROT_READ); 370 } 371 anon->an_ref++; 372 **output = anon; 373 (*output)++; 374 UVMHIST_LOG(loanhist, "->A done", 0,0,0,0); 375 return (1); 376 } 377 378 /* 379 * we are loaning to a kernel-page. we need to get the page 380 * resident so we can wire it. uvmfault_anonget will handle 381 * this for us. 382 */ 383 384 KASSERT(mutex_owned(anon->an_lock)); 385 error = uvmfault_anonget(ufi, ufi->entry->aref.ar_amap, anon); 386 387 /* 388 * if we were unable to get the anon, then uvmfault_anonget has 389 * unlocked everything and returned an error code. 390 */ 391 392 if (error) { 393 UVMHIST_LOG(loanhist, "error %jd", error,0,0,0); 394 395 /* need to refault (i.e. refresh our lookup) ? */ 396 if (error == ERESTART) { 397 return (0); 398 } 399 400 /* "try again"? sleep a bit and retry ... */ 401 if (error == EAGAIN) { 402 kpause("loanagain", false, hz/2, NULL); 403 return (0); 404 } 405 406 /* otherwise flag it as an error */ 407 return (-1); 408 } 409 410 /* 411 * we have the page and its owner locked: do the loan now. 412 */ 413 414 pg = anon->an_page; 415 mutex_enter(&uvm_pageqlock); 416 if (pg->wire_count > 0) { 417 mutex_exit(&uvm_pageqlock); 418 UVMHIST_LOG(loanhist, "->K wired %#jx", (uintptr_t)pg, 0, 0, 0); 419 KASSERT(pg->uobject == NULL); 420 uvmfault_unlockall(ufi, ufi->entry->aref.ar_amap, NULL); 421 return (-1); 422 } 423 if (pg->loan_count == 0) { 424 pmap_page_protect(pg, VM_PROT_READ); 425 } 426 pg->loan_count++; 427 KASSERT(pg->loan_count > 0); /* detect wrap-around */ 428 uvm_pageactivate(pg); 429 mutex_exit(&uvm_pageqlock); 430 **output = pg; 431 (*output)++; 432 433 /* unlock and return success */ 434 if (pg->uobject) 435 mutex_exit(pg->uobject->vmobjlock); 436 UVMHIST_LOG(loanhist, "->K done", 0,0,0,0); 437 return (1); 438 } 439 440 /* 441 * uvm_loanpage: loan out pages to kernel (->K) 442 * 443 * => pages should be object-owned and the object should be locked. 444 * => in the case of error, the object might be unlocked and relocked. 445 * => caller should busy the pages beforehand. 446 * => pages will be unbusied. 447 * => fail with EBUSY if meet a wired page. 448 */ 449 static int 450 uvm_loanpage(struct vm_page **pgpp, int npages) 451 { 452 int i; 453 int error = 0; 454 455 UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist); 456 457 for (i = 0; i < npages; i++) { 458 struct vm_page *pg = pgpp[i]; 459 460 KASSERT(pg->uobject != NULL); 461 KASSERT(pg->uobject == pgpp[0]->uobject); 462 KASSERT(!(pg->flags & (PG_RELEASED|PG_PAGEOUT))); 463 KASSERT(mutex_owned(pg->uobject->vmobjlock)); 464 KASSERT(pg->flags & PG_BUSY); 465 466 mutex_enter(&uvm_pageqlock); 467 if (pg->wire_count > 0) { 468 mutex_exit(&uvm_pageqlock); 469 UVMHIST_LOG(loanhist, "wired %#jx", (uintptr_t)pg, 470 0, 0, 0); 471 error = EBUSY; 472 break; 473 } 474 if (pg->loan_count == 0) { 475 pmap_page_protect(pg, VM_PROT_READ); 476 } 477 pg->loan_count++; 478 KASSERT(pg->loan_count > 0); /* detect wrap-around */ 479 uvm_pageactivate(pg); 480 mutex_exit(&uvm_pageqlock); 481 } 482 483 uvm_page_unbusy(pgpp, npages); 484 485 if (error) { 486 /* 487 * backout what we've done 488 */ 489 kmutex_t *slock = pgpp[0]->uobject->vmobjlock; 490 491 mutex_exit(slock); 492 uvm_unloan(pgpp, i, UVM_LOAN_TOPAGE); 493 mutex_enter(slock); 494 } 495 496 UVMHIST_LOG(loanhist, "done %jd", error, 0, 0, 0); 497 return error; 498 } 499 500 /* 501 * XXX UBC temp limit 502 * number of pages to get at once. 503 * should be <= MAX_READ_AHEAD in genfs_vnops.c 504 */ 505 #define UVM_LOAN_GET_CHUNK 16 506 507 /* 508 * uvm_loanuobjpages: loan pages from a uobj out (O->K) 509 * 510 * => uobj shouldn't be locked. (we'll lock it) 511 * => fail with EBUSY if we meet a wired page. 512 */ 513 int 514 uvm_loanuobjpages(struct uvm_object *uobj, voff_t pgoff, int orignpages, 515 struct vm_page **origpgpp) 516 { 517 int ndone; /* # of pages loaned out */ 518 struct vm_page **pgpp; 519 int error; 520 int i; 521 kmutex_t *slock; 522 523 pgpp = origpgpp; 524 for (ndone = 0; ndone < orignpages; ) { 525 int npages; 526 /* npendloan: # of pages busied but not loand out yet. */ 527 int npendloan = 0xdead; /* XXX gcc */ 528 reget: 529 npages = MIN(UVM_LOAN_GET_CHUNK, orignpages - ndone); 530 mutex_enter(uobj->vmobjlock); 531 error = (*uobj->pgops->pgo_get)(uobj, 532 pgoff + (ndone << PAGE_SHIFT), pgpp, &npages, 0, 533 VM_PROT_READ, 0, PGO_SYNCIO); 534 if (error == EAGAIN) { 535 kpause("loanuopg", false, hz/2, NULL); 536 continue; 537 } 538 if (error) 539 goto fail; 540 541 KASSERT(npages > 0); 542 543 /* loan and unbusy pages */ 544 slock = NULL; 545 for (i = 0; i < npages; i++) { 546 kmutex_t *nextslock; /* slock for next page */ 547 struct vm_page *pg = *pgpp; 548 549 /* XXX assuming that the page is owned by uobj */ 550 KASSERT(pg->uobject != NULL); 551 nextslock = pg->uobject->vmobjlock; 552 553 if (slock != nextslock) { 554 if (slock) { 555 KASSERT(npendloan > 0); 556 error = uvm_loanpage(pgpp - npendloan, 557 npendloan); 558 mutex_exit(slock); 559 if (error) 560 goto fail; 561 ndone += npendloan; 562 KASSERT(origpgpp + ndone == pgpp); 563 } 564 slock = nextslock; 565 npendloan = 0; 566 mutex_enter(slock); 567 } 568 569 if ((pg->flags & PG_RELEASED) != 0) { 570 /* 571 * release pages and try again. 572 */ 573 mutex_exit(slock); 574 for (; i < npages; i++) { 575 pg = pgpp[i]; 576 slock = pg->uobject->vmobjlock; 577 578 mutex_enter(slock); 579 mutex_enter(&uvm_pageqlock); 580 uvm_page_unbusy(&pg, 1); 581 mutex_exit(&uvm_pageqlock); 582 mutex_exit(slock); 583 } 584 goto reget; 585 } 586 587 npendloan++; 588 pgpp++; 589 KASSERT(origpgpp + ndone + npendloan == pgpp); 590 } 591 KASSERT(slock != NULL); 592 KASSERT(npendloan > 0); 593 error = uvm_loanpage(pgpp - npendloan, npendloan); 594 mutex_exit(slock); 595 if (error) 596 goto fail; 597 ndone += npendloan; 598 KASSERT(origpgpp + ndone == pgpp); 599 } 600 601 return 0; 602 603 fail: 604 uvm_unloan(origpgpp, ndone, UVM_LOAN_TOPAGE); 605 606 return error; 607 } 608 609 /* 610 * uvm_loanuobj: loan a page from a uobj out 611 * 612 * => called with map, amap, uobj locked 613 * => return value: 614 * -1 = fatal error, everything is unlocked, abort. 615 * 0 = lookup in ufi went stale, everything unlocked, relookup and 616 * try again 617 * 1 = got it, everything still locked 618 */ 619 620 static int 621 uvm_loanuobj(struct uvm_faultinfo *ufi, void ***output, int flags, vaddr_t va) 622 { 623 struct vm_amap *amap = ufi->entry->aref.ar_amap; 624 struct uvm_object *uobj = ufi->entry->object.uvm_obj; 625 struct vm_page *pg; 626 int error, npages; 627 bool locked; 628 629 UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist); 630 631 /* 632 * first we must make sure the page is resident. 633 * 634 * XXXCDC: duplicate code with uvm_fault(). 635 */ 636 637 /* locked: maps(read), amap(if there) */ 638 mutex_enter(uobj->vmobjlock); 639 /* locked: maps(read), amap(if there), uobj */ 640 641 if (uobj->pgops->pgo_get) { /* try locked pgo_get */ 642 npages = 1; 643 pg = NULL; 644 error = (*uobj->pgops->pgo_get)(uobj, 645 va - ufi->entry->start + ufi->entry->offset, 646 &pg, &npages, 0, VM_PROT_READ, MADV_NORMAL, PGO_LOCKED); 647 } else { 648 error = EIO; /* must have pgo_get op */ 649 } 650 651 /* 652 * check the result of the locked pgo_get. if there is a problem, 653 * then we fail the loan. 654 */ 655 656 if (error && error != EBUSY) { 657 uvmfault_unlockall(ufi, amap, uobj); 658 return (-1); 659 } 660 661 /* 662 * if we need to unlock for I/O, do so now. 663 */ 664 665 if (error == EBUSY) { 666 uvmfault_unlockall(ufi, amap, NULL); 667 668 /* locked: uobj */ 669 npages = 1; 670 error = (*uobj->pgops->pgo_get)(uobj, 671 va - ufi->entry->start + ufi->entry->offset, 672 &pg, &npages, 0, VM_PROT_READ, MADV_NORMAL, PGO_SYNCIO); 673 /* locked: <nothing> */ 674 675 if (error) { 676 if (error == EAGAIN) { 677 kpause("fltagain2", false, hz/2, NULL); 678 return (0); 679 } 680 return (-1); 681 } 682 683 /* 684 * pgo_get was a success. attempt to relock everything. 685 */ 686 687 locked = uvmfault_relock(ufi); 688 if (locked && amap) 689 amap_lock(amap); 690 uobj = pg->uobject; 691 mutex_enter(uobj->vmobjlock); 692 693 /* 694 * verify that the page has not be released and re-verify 695 * that amap slot is still free. if there is a problem we 696 * drop our lock (thus force a lookup refresh/retry). 697 */ 698 699 if ((pg->flags & PG_RELEASED) != 0 || 700 (locked && amap && amap_lookup(&ufi->entry->aref, 701 ufi->orig_rvaddr - ufi->entry->start))) { 702 if (locked) 703 uvmfault_unlockall(ufi, amap, NULL); 704 locked = false; 705 } 706 707 /* 708 * didn't get the lock? release the page and retry. 709 */ 710 711 if (locked == false) { 712 if (pg->flags & PG_WANTED) { 713 wakeup(pg); 714 } 715 if (pg->flags & PG_RELEASED) { 716 mutex_enter(&uvm_pageqlock); 717 uvm_pagefree(pg); 718 mutex_exit(&uvm_pageqlock); 719 mutex_exit(uobj->vmobjlock); 720 return (0); 721 } 722 mutex_enter(&uvm_pageqlock); 723 uvm_pageactivate(pg); 724 mutex_exit(&uvm_pageqlock); 725 pg->flags &= ~(PG_BUSY|PG_WANTED); 726 UVM_PAGE_OWN(pg, NULL); 727 mutex_exit(uobj->vmobjlock); 728 return (0); 729 } 730 } 731 732 KASSERT(uobj == pg->uobject); 733 734 /* 735 * at this point we have the page we want ("pg") marked PG_BUSY for us 736 * and we have all data structures locked. do the loanout. page can 737 * not be PG_RELEASED (we caught this above). 738 */ 739 740 if ((flags & UVM_LOAN_TOANON) == 0) { 741 if (uvm_loanpage(&pg, 1)) { 742 uvmfault_unlockall(ufi, amap, uobj); 743 return (-1); 744 } 745 mutex_exit(uobj->vmobjlock); 746 **output = pg; 747 (*output)++; 748 return (1); 749 } 750 751 #ifdef notdef 752 /* 753 * must be a loan to an anon. check to see if there is already 754 * an anon associated with this page. if so, then just return 755 * a reference to this object. the page should already be 756 * mapped read-only because it is already on loan. 757 */ 758 759 if (pg->uanon) { 760 /* XXX: locking */ 761 anon = pg->uanon; 762 anon->an_ref++; 763 if (pg->flags & PG_WANTED) { 764 wakeup(pg); 765 } 766 pg->flags &= ~(PG_WANTED|PG_BUSY); 767 UVM_PAGE_OWN(pg, NULL); 768 mutex_exit(uobj->vmobjlock); 769 **output = anon; 770 (*output)++; 771 return (1); 772 } 773 774 /* 775 * need to allocate a new anon 776 */ 777 778 anon = uvm_analloc(); 779 if (anon == NULL) { 780 goto fail; 781 } 782 mutex_enter(&uvm_pageqlock); 783 if (pg->wire_count > 0) { 784 mutex_exit(&uvm_pageqlock); 785 UVMHIST_LOG(loanhist, "wired %#jx", (uintptr_t)pg, 0, 0, 0); 786 goto fail; 787 } 788 if (pg->loan_count == 0) { 789 pmap_page_protect(pg, VM_PROT_READ); 790 } 791 pg->loan_count++; 792 KASSERT(pg->loan_count > 0); /* detect wrap-around */ 793 pg->uanon = anon; 794 anon->an_page = pg; 795 anon->an_lock = /* TODO: share amap lock */ 796 uvm_pageactivate(pg); 797 mutex_exit(&uvm_pageqlock); 798 if (pg->flags & PG_WANTED) { 799 wakeup(pg); 800 } 801 pg->flags &= ~(PG_WANTED|PG_BUSY); 802 UVM_PAGE_OWN(pg, NULL); 803 mutex_exit(uobj->vmobjlock); 804 mutex_exit(&anon->an_lock); 805 **output = anon; 806 (*output)++; 807 return (1); 808 809 fail: 810 UVMHIST_LOG(loanhist, "fail", 0,0,0,0); 811 /* 812 * unlock everything and bail out. 813 */ 814 if (pg->flags & PG_WANTED) { 815 wakeup(pg); 816 } 817 pg->flags &= ~(PG_WANTED|PG_BUSY); 818 UVM_PAGE_OWN(pg, NULL); 819 uvmfault_unlockall(ufi, amap, uobj, NULL); 820 if (anon) { 821 anon->an_ref--; 822 uvm_anon_free(anon); 823 } 824 #endif /* notdef */ 825 return (-1); 826 } 827 828 /* 829 * uvm_loanzero: loan a zero-fill page out 830 * 831 * => called with map, amap, uobj locked 832 * => return value: 833 * -1 = fatal error, everything is unlocked, abort. 834 * 0 = lookup in ufi went stale, everything unlocked, relookup and 835 * try again 836 * 1 = got it, everything still locked 837 */ 838 839 static struct uvm_object uvm_loanzero_object; 840 static kmutex_t uvm_loanzero_lock; 841 842 static int 843 uvm_loanzero(struct uvm_faultinfo *ufi, void ***output, int flags) 844 { 845 struct vm_page *pg; 846 struct vm_amap *amap = ufi->entry->aref.ar_amap; 847 848 UVMHIST_FUNC(__func__); UVMHIST_CALLED(loanhist); 849 again: 850 mutex_enter(uvm_loanzero_object.vmobjlock); 851 852 /* 853 * first, get ahold of our single zero page. 854 */ 855 856 if (__predict_false((pg = 857 TAILQ_FIRST(&uvm_loanzero_object.memq)) == NULL)) { 858 while ((pg = uvm_pagealloc(&uvm_loanzero_object, 0, NULL, 859 UVM_PGA_ZERO)) == NULL) { 860 mutex_exit(uvm_loanzero_object.vmobjlock); 861 uvmfault_unlockall(ufi, amap, NULL); 862 uvm_wait("loanzero"); 863 if (!uvmfault_relock(ufi)) { 864 return (0); 865 } 866 if (amap) { 867 amap_lock(amap); 868 } 869 goto again; 870 } 871 872 /* got a zero'd page. */ 873 pg->flags &= ~(PG_WANTED|PG_BUSY|PG_FAKE); 874 pg->flags |= PG_RDONLY; 875 mutex_enter(&uvm_pageqlock); 876 uvm_pageactivate(pg); 877 mutex_exit(&uvm_pageqlock); 878 UVM_PAGE_OWN(pg, NULL); 879 } 880 881 if ((flags & UVM_LOAN_TOANON) == 0) { /* loaning to kernel-page */ 882 mutex_enter(&uvm_pageqlock); 883 pg->loan_count++; 884 KASSERT(pg->loan_count > 0); /* detect wrap-around */ 885 mutex_exit(&uvm_pageqlock); 886 mutex_exit(uvm_loanzero_object.vmobjlock); 887 **output = pg; 888 (*output)++; 889 return (1); 890 } 891 892 #ifdef notdef 893 /* 894 * loaning to an anon. check to see if there is already an anon 895 * associated with this page. if so, then just return a reference 896 * to this object. 897 */ 898 899 if (pg->uanon) { 900 anon = pg->uanon; 901 mutex_enter(&anon->an_lock); 902 anon->an_ref++; 903 mutex_exit(&anon->an_lock); 904 mutex_exit(uvm_loanzero_object.vmobjlock); 905 **output = anon; 906 (*output)++; 907 return (1); 908 } 909 910 /* 911 * need to allocate a new anon 912 */ 913 914 anon = uvm_analloc(); 915 if (anon == NULL) { 916 /* out of swap causes us to fail */ 917 mutex_exit(uvm_loanzero_object.vmobjlock); 918 uvmfault_unlockall(ufi, amap, NULL, NULL); 919 return (-1); 920 } 921 anon->an_page = pg; 922 pg->uanon = anon; 923 mutex_enter(&uvm_pageqlock); 924 pg->loan_count++; 925 KASSERT(pg->loan_count > 0); /* detect wrap-around */ 926 uvm_pageactivate(pg); 927 mutex_exit(&uvm_pageqlock); 928 mutex_exit(&anon->an_lock); 929 mutex_exit(uvm_loanzero_object.vmobjlock); 930 **output = anon; 931 (*output)++; 932 return (1); 933 #else 934 return (-1); 935 #endif 936 } 937 938 939 /* 940 * uvm_unloananon: kill loans on anons (basically a normal ref drop) 941 * 942 * => we expect all our resources to be unlocked 943 */ 944 945 static void 946 uvm_unloananon(struct vm_anon **aloans, int nanons) 947 { 948 #ifdef notdef 949 struct vm_anon *anon, *to_free = NULL; 950 951 /* TODO: locking */ 952 amap_lock(amap); 953 while (nanons-- > 0) { 954 anon = *aloans++; 955 if (--anon->an_ref == 0) { 956 anon->an_link = to_free; 957 to_free = anon; 958 } 959 } 960 uvm_anon_freelst(amap, to_free); 961 #endif /* notdef */ 962 } 963 964 /* 965 * uvm_unloanpage: kill loans on pages loaned out to the kernel 966 * 967 * => we expect all our resources to be unlocked 968 */ 969 970 static void 971 uvm_unloanpage(struct vm_page **ploans, int npages) 972 { 973 struct vm_page *pg; 974 kmutex_t *slock; 975 976 mutex_enter(&uvm_pageqlock); 977 while (npages-- > 0) { 978 pg = *ploans++; 979 980 /* 981 * do a little dance to acquire the object or anon lock 982 * as appropriate. we are locking in the wrong order, 983 * so we have to do a try-lock here. 984 */ 985 986 slock = NULL; 987 while (pg->uobject != NULL || pg->uanon != NULL) { 988 if (pg->uobject != NULL) { 989 slock = pg->uobject->vmobjlock; 990 } else { 991 slock = pg->uanon->an_lock; 992 } 993 if (mutex_tryenter(slock)) { 994 break; 995 } 996 /* XXX Better than yielding but inadequate. */ 997 kpause("livelock", false, 1, &uvm_pageqlock); 998 slock = NULL; 999 } 1000 1001 /* 1002 * drop our loan. if page is owned by an anon but 1003 * PQ_ANON is not set, the page was loaned to the anon 1004 * from an object which dropped ownership, so resolve 1005 * this by turning the anon's loan into real ownership 1006 * (ie. decrement loan_count again and set PQ_ANON). 1007 * after all this, if there are no loans left, put the 1008 * page back a paging queue (if the page is owned by 1009 * an anon) or free it (if the page is now unowned). 1010 */ 1011 1012 KASSERT(pg->loan_count > 0); 1013 pg->loan_count--; 1014 if (pg->uobject == NULL && pg->uanon != NULL && 1015 (pg->pqflags & PQ_ANON) == 0) { 1016 KASSERT(pg->loan_count > 0); 1017 pg->loan_count--; 1018 pg->pqflags |= PQ_ANON; 1019 } 1020 if (pg->loan_count == 0 && pg->uobject == NULL && 1021 pg->uanon == NULL) { 1022 KASSERT((pg->flags & PG_BUSY) == 0); 1023 uvm_pagefree(pg); 1024 } 1025 if (slock != NULL) { 1026 mutex_exit(slock); 1027 } 1028 } 1029 mutex_exit(&uvm_pageqlock); 1030 } 1031 1032 /* 1033 * uvm_unloan: kill loans on pages or anons. 1034 */ 1035 1036 void 1037 uvm_unloan(void *v, int npages, int flags) 1038 { 1039 if (flags & UVM_LOAN_TOANON) { 1040 uvm_unloananon(v, npages); 1041 } else { 1042 uvm_unloanpage(v, npages); 1043 } 1044 } 1045 1046 /* 1047 * Minimal pager for uvm_loanzero_object. We need to provide a "put" 1048 * method, because the page can end up on a paging queue, and the 1049 * page daemon will want to call pgo_put when it encounters the page 1050 * on the inactive list. 1051 */ 1052 1053 static int 1054 ulz_put(struct uvm_object *uobj, voff_t start, voff_t stop, int flags) 1055 { 1056 struct vm_page *pg; 1057 1058 KDASSERT(uobj == &uvm_loanzero_object); 1059 1060 /* 1061 * Don't need to do any work here if we're not freeing pages. 1062 */ 1063 1064 if ((flags & PGO_FREE) == 0) { 1065 mutex_exit(uobj->vmobjlock); 1066 return 0; 1067 } 1068 1069 /* 1070 * we don't actually want to ever free the uvm_loanzero_page, so 1071 * just reactivate or dequeue it. 1072 */ 1073 1074 pg = TAILQ_FIRST(&uobj->memq); 1075 KASSERT(pg != NULL); 1076 KASSERT(TAILQ_NEXT(pg, listq.queue) == NULL); 1077 1078 mutex_enter(&uvm_pageqlock); 1079 if (pg->uanon) 1080 uvm_pageactivate(pg); 1081 else 1082 uvm_pagedequeue(pg); 1083 mutex_exit(&uvm_pageqlock); 1084 1085 mutex_exit(uobj->vmobjlock); 1086 return 0; 1087 } 1088 1089 static const struct uvm_pagerops ulz_pager = { 1090 .pgo_put = ulz_put, 1091 }; 1092 1093 /* 1094 * uvm_loan_init(): initialize the uvm_loan() facility. 1095 */ 1096 1097 void 1098 uvm_loan_init(void) 1099 { 1100 1101 mutex_init(&uvm_loanzero_lock, MUTEX_DEFAULT, IPL_NONE); 1102 uvm_obj_init(&uvm_loanzero_object, &ulz_pager, false, 0); 1103 uvm_obj_setlock(&uvm_loanzero_object, &uvm_loanzero_lock); 1104 1105 UVMHIST_INIT(loanhist, 300); 1106 } 1107 1108 /* 1109 * uvm_loanbreak: break loan on a uobj page 1110 * 1111 * => called with uobj locked 1112 * => the page should be busy 1113 * => return value: 1114 * newly allocated page if succeeded 1115 */ 1116 struct vm_page * 1117 uvm_loanbreak(struct vm_page *uobjpage) 1118 { 1119 struct vm_page *pg; 1120 struct uvm_object *uobj __diagused = uobjpage->uobject; 1121 1122 KASSERT(uobj != NULL); 1123 KASSERT(mutex_owned(uobj->vmobjlock)); 1124 KASSERT(uobjpage->flags & PG_BUSY); 1125 1126 /* alloc new un-owned page */ 1127 pg = uvm_pagealloc(NULL, 0, NULL, 0); 1128 if (pg == NULL) 1129 return NULL; 1130 1131 /* 1132 * copy the data from the old page to the new 1133 * one and clear the fake flags on the new page (keep it busy). 1134 * force a reload of the old page by clearing it from all 1135 * pmaps. 1136 * transfer dirtiness of the old page to the new page. 1137 * then lock the page queues to rename the pages. 1138 */ 1139 1140 uvm_pagecopy(uobjpage, pg); /* old -> new */ 1141 pg->flags &= ~PG_FAKE; 1142 pmap_page_protect(uobjpage, VM_PROT_NONE); 1143 if ((uobjpage->flags & PG_CLEAN) != 0 && !pmap_clear_modify(uobjpage)) { 1144 pmap_clear_modify(pg); 1145 pg->flags |= PG_CLEAN; 1146 } else { 1147 /* uvm_pagecopy marked it dirty */ 1148 KASSERT((pg->flags & PG_CLEAN) == 0); 1149 /* a object with a dirty page should be dirty. */ 1150 KASSERT(!UVM_OBJ_IS_CLEAN(uobj)); 1151 } 1152 if (uobjpage->flags & PG_WANTED) 1153 wakeup(uobjpage); 1154 /* uobj still locked */ 1155 uobjpage->flags &= ~(PG_WANTED|PG_BUSY); 1156 UVM_PAGE_OWN(uobjpage, NULL); 1157 1158 mutex_enter(&uvm_pageqlock); 1159 1160 /* 1161 * replace uobjpage with new page. 1162 */ 1163 1164 uvm_pagereplace(uobjpage, pg); 1165 1166 /* 1167 * if the page is no longer referenced by 1168 * an anon (i.e. we are breaking an O->K 1169 * loan), then remove it from any pageq's. 1170 */ 1171 if (uobjpage->uanon == NULL) 1172 uvm_pagedequeue(uobjpage); 1173 1174 /* 1175 * at this point we have absolutely no 1176 * control over uobjpage 1177 */ 1178 1179 /* install new page */ 1180 uvm_pageactivate(pg); 1181 mutex_exit(&uvm_pageqlock); 1182 1183 /* 1184 * done! loan is broken and "pg" is 1185 * PG_BUSY. it can now replace uobjpage. 1186 */ 1187 1188 return pg; 1189 } 1190 1191 int 1192 uvm_loanbreak_anon(struct vm_anon *anon, struct uvm_object *uobj) 1193 { 1194 struct vm_page *pg; 1195 1196 KASSERT(mutex_owned(anon->an_lock)); 1197 KASSERT(uobj == NULL || mutex_owned(uobj->vmobjlock)); 1198 1199 /* get new un-owned replacement page */ 1200 pg = uvm_pagealloc(NULL, 0, NULL, 0); 1201 if (pg == NULL) { 1202 return ENOMEM; 1203 } 1204 1205 /* copy old -> new */ 1206 uvm_pagecopy(anon->an_page, pg); 1207 1208 /* force reload */ 1209 pmap_page_protect(anon->an_page, VM_PROT_NONE); 1210 mutex_enter(&uvm_pageqlock); /* KILL loan */ 1211 1212 anon->an_page->uanon = NULL; 1213 /* in case we owned */ 1214 anon->an_page->pqflags &= ~PQ_ANON; 1215 1216 if (uobj) { 1217 /* if we were receiver of loan */ 1218 anon->an_page->loan_count--; 1219 } else { 1220 /* 1221 * we were the lender (A->K); need to remove the page from 1222 * pageq's. 1223 */ 1224 uvm_pagedequeue(anon->an_page); 1225 } 1226 1227 if (uobj) { 1228 mutex_exit(uobj->vmobjlock); 1229 } 1230 1231 /* install new page in anon */ 1232 anon->an_page = pg; 1233 pg->uanon = anon; 1234 pg->pqflags |= PQ_ANON; 1235 1236 uvm_pageactivate(pg); 1237 mutex_exit(&uvm_pageqlock); 1238 1239 pg->flags &= ~(PG_BUSY|PG_FAKE); 1240 UVM_PAGE_OWN(pg, NULL); 1241 1242 /* done! */ 1243 1244 return 0; 1245 } 1246