1 /* 2 * Copyright (c) 1998 Matthew Dillon, 3 * Copyright (c) 1994 John S. Dyson 4 * Copyright (c) 1990 University of Utah. 5 * Copyright (c) 1991, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * the Systems Programming Group of the University of Utah Computer 10 * Science Department. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * New Swap System 41 * Matthew Dillon 42 * 43 * Radix Bitmap 'blists'. 44 * 45 * - The new swapper uses the new radix bitmap code. This should scale 46 * to arbitrarily small or arbitrarily large swap spaces and an almost 47 * arbitrary degree of fragmentation. 48 * 49 * Features: 50 * 51 * - on the fly reallocation of swap during putpages. The new system 52 * does not try to keep previously allocated swap blocks for dirty 53 * pages. 54 * 55 * - on the fly deallocation of swap 56 * 57 * - No more garbage collection required. Unnecessarily allocated swap 58 * blocks only exist for dirty vm_page_t's now and these are already 59 * cycled (in a high-load system) by the pager. We also do on-the-fly 60 * removal of invalidated swap blocks when a page is destroyed 61 * or renamed. 62 * 63 * from: Utah $Hdr: swap_pager.c 1.4 91/04/30$ 64 * 65 * @(#)swap_pager.c 8.9 (Berkeley) 3/21/94 66 * 67 * $FreeBSD: src/sys/vm/swap_pager.c,v 1.130.2.12 2002/08/31 21:15:55 dillon Exp $ 68 * $DragonFly: src/sys/vm/swap_pager.c,v 1.11 2004/03/23 22:54:32 dillon Exp $ 69 */ 70 71 #include <sys/param.h> 72 #include <sys/systm.h> 73 #include <sys/conf.h> 74 #include <sys/kernel.h> 75 #include <sys/proc.h> 76 #include <sys/buf.h> 77 #include <sys/vnode.h> 78 #include <sys/malloc.h> 79 #include <sys/vmmeter.h> 80 #include <sys/sysctl.h> 81 #include <sys/blist.h> 82 #include <sys/lock.h> 83 #include <sys/vmmeter.h> 84 85 #ifndef MAX_PAGEOUT_CLUSTER 86 #define MAX_PAGEOUT_CLUSTER 16 87 #endif 88 89 #define SWB_NPAGES MAX_PAGEOUT_CLUSTER 90 91 #include "opt_swap.h" 92 #include <vm/vm.h> 93 #include <vm/vm_object.h> 94 #include <vm/vm_page.h> 95 #include <vm/vm_pager.h> 96 #include <vm/vm_pageout.h> 97 #include <vm/swap_pager.h> 98 #include <vm/vm_extern.h> 99 #include <vm/vm_zone.h> 100 101 #include <sys/buf2.h> 102 #include <vm/vm_page2.h> 103 104 #define SWM_FREE 0x02 /* free, period */ 105 #define SWM_POP 0x04 /* pop out */ 106 107 /* 108 * vm_swap_size is in page-sized chunks now. It was DEV_BSIZE'd chunks 109 * in the old system. 110 */ 111 112 extern int vm_swap_size; /* number of free swap blocks, in pages */ 113 114 int swap_pager_full; /* swap space exhaustion (task killing) */ 115 static int swap_pager_almost_full; /* swap space exhaustion (w/ hysteresis)*/ 116 static int nsw_rcount; /* free read buffers */ 117 static int nsw_wcount_sync; /* limit write buffers / synchronous */ 118 static int nsw_wcount_async; /* limit write buffers / asynchronous */ 119 static int nsw_wcount_async_max;/* assigned maximum */ 120 static int nsw_cluster_max; /* maximum VOP I/O allowed */ 121 static int sw_alloc_interlock; /* swap pager allocation interlock */ 122 123 struct blist *swapblist; 124 static struct swblock **swhash; 125 static int swhash_mask; 126 static int swap_async_max = 4; /* maximum in-progress async I/O's */ 127 128 extern struct vnode *swapdev_vp; /* from vm_swap.c */ 129 130 SYSCTL_INT(_vm, OID_AUTO, swap_async_max, 131 CTLFLAG_RW, &swap_async_max, 0, "Maximum running async swap ops"); 132 133 /* 134 * "named" and "unnamed" anon region objects. Try to reduce the overhead 135 * of searching a named list by hashing it just a little. 136 */ 137 138 #define NOBJLISTS 8 139 140 #define NOBJLIST(handle) \ 141 (&swap_pager_object_list[((int)(intptr_t)handle >> 4) & (NOBJLISTS-1)]) 142 143 static struct pagerlst swap_pager_object_list[NOBJLISTS]; 144 struct pagerlst swap_pager_un_object_list; 145 vm_zone_t swap_zone; 146 147 /* 148 * pagerops for OBJT_SWAP - "swap pager". Some ops are also global procedure 149 * calls hooked from other parts of the VM system and do not appear here. 150 * (see vm/swap_pager.h). 151 */ 152 153 static vm_object_t 154 swap_pager_alloc (void *handle, vm_ooffset_t size, 155 vm_prot_t prot, vm_ooffset_t offset); 156 static void swap_pager_dealloc (vm_object_t object); 157 static int swap_pager_getpages (vm_object_t, vm_page_t *, int, int); 158 static void swap_pager_init (void); 159 static void swap_pager_unswapped (vm_page_t); 160 static void swap_pager_strategy (vm_object_t, struct buf *); 161 162 struct pagerops swappagerops = { 163 swap_pager_init, /* early system initialization of pager */ 164 swap_pager_alloc, /* allocate an OBJT_SWAP object */ 165 swap_pager_dealloc, /* deallocate an OBJT_SWAP object */ 166 swap_pager_getpages, /* pagein */ 167 swap_pager_putpages, /* pageout */ 168 swap_pager_haspage, /* get backing store status for page */ 169 swap_pager_unswapped, /* remove swap related to page */ 170 swap_pager_strategy /* pager strategy call */ 171 }; 172 173 /* 174 * dmmax is in page-sized chunks with the new swap system. It was 175 * dev-bsized chunks in the old. dmmax is always a power of 2. 176 * 177 * swap_*() routines are externally accessible. swp_*() routines are 178 * internal. 179 */ 180 181 int dmmax; 182 static int dmmax_mask; 183 int nswap_lowat = 128; /* in pages, swap_pager_almost_full warn */ 184 int nswap_hiwat = 512; /* in pages, swap_pager_almost_full warn */ 185 186 static __inline void swp_sizecheck (void); 187 static void swp_pager_sync_iodone (struct buf *bp); 188 static void swp_pager_async_iodone (struct buf *bp); 189 190 /* 191 * Swap bitmap functions 192 */ 193 194 static __inline void swp_pager_freeswapspace (daddr_t blk, int npages); 195 static __inline daddr_t swp_pager_getswapspace (int npages); 196 197 /* 198 * Metadata functions 199 */ 200 201 static void swp_pager_meta_build (vm_object_t, vm_pindex_t, daddr_t); 202 static void swp_pager_meta_free (vm_object_t, vm_pindex_t, daddr_t); 203 static void swp_pager_meta_free_all (vm_object_t); 204 static daddr_t swp_pager_meta_ctl (vm_object_t, vm_pindex_t, int); 205 206 /* 207 * SWP_SIZECHECK() - update swap_pager_full indication 208 * 209 * update the swap_pager_almost_full indication and warn when we are 210 * about to run out of swap space, using lowat/hiwat hysteresis. 211 * 212 * Clear swap_pager_full ( task killing ) indication when lowat is met. 213 * 214 * No restrictions on call 215 * This routine may not block. 216 * This routine must be called at splvm() 217 */ 218 219 static __inline void 220 swp_sizecheck(void) 221 { 222 if (vm_swap_size < nswap_lowat) { 223 if (swap_pager_almost_full == 0) { 224 printf("swap_pager: out of swap space\n"); 225 swap_pager_almost_full = 1; 226 } 227 } else { 228 swap_pager_full = 0; 229 if (vm_swap_size > nswap_hiwat) 230 swap_pager_almost_full = 0; 231 } 232 } 233 234 /* 235 * SWAP_PAGER_INIT() - initialize the swap pager! 236 * 237 * Expected to be started from system init. NOTE: This code is run 238 * before much else so be careful what you depend on. Most of the VM 239 * system has yet to be initialized at this point. 240 */ 241 242 static void 243 swap_pager_init(void) 244 { 245 /* 246 * Initialize object lists 247 */ 248 int i; 249 250 for (i = 0; i < NOBJLISTS; ++i) 251 TAILQ_INIT(&swap_pager_object_list[i]); 252 TAILQ_INIT(&swap_pager_un_object_list); 253 254 /* 255 * Device Stripe, in PAGE_SIZE'd blocks 256 */ 257 258 dmmax = SWB_NPAGES * 2; 259 dmmax_mask = ~(dmmax - 1); 260 } 261 262 /* 263 * SWAP_PAGER_SWAP_INIT() - swap pager initialization from pageout process 264 * 265 * Expected to be started from pageout process once, prior to entering 266 * its main loop. 267 */ 268 269 void 270 swap_pager_swap_init(void) 271 { 272 int n, n2; 273 274 /* 275 * Number of in-transit swap bp operations. Don't 276 * exhaust the pbufs completely. Make sure we 277 * initialize workable values (0 will work for hysteresis 278 * but it isn't very efficient). 279 * 280 * The nsw_cluster_max is constrained by the bp->b_pages[] 281 * array (MAXPHYS/PAGE_SIZE) and our locally defined 282 * MAX_PAGEOUT_CLUSTER. Also be aware that swap ops are 283 * constrained by the swap device interleave stripe size. 284 * 285 * Currently we hardwire nsw_wcount_async to 4. This limit is 286 * designed to prevent other I/O from having high latencies due to 287 * our pageout I/O. The value 4 works well for one or two active swap 288 * devices but is probably a little low if you have more. Even so, 289 * a higher value would probably generate only a limited improvement 290 * with three or four active swap devices since the system does not 291 * typically have to pageout at extreme bandwidths. We will want 292 * at least 2 per swap devices, and 4 is a pretty good value if you 293 * have one NFS swap device due to the command/ack latency over NFS. 294 * So it all works out pretty well. 295 */ 296 297 nsw_cluster_max = min((MAXPHYS/PAGE_SIZE), MAX_PAGEOUT_CLUSTER); 298 299 nsw_rcount = (nswbuf + 1) / 2; 300 nsw_wcount_sync = (nswbuf + 3) / 4; 301 nsw_wcount_async = 4; 302 nsw_wcount_async_max = nsw_wcount_async; 303 304 /* 305 * Initialize our zone. Right now I'm just guessing on the number 306 * we need based on the number of pages in the system. Each swblock 307 * can hold 16 pages, so this is probably overkill. This reservation 308 * is typically limited to around 32MB by default. 309 */ 310 n = vmstats.v_page_count / 2; 311 if (maxswzone && n > maxswzone / sizeof(struct swblock)) 312 n = maxswzone / sizeof(struct swblock); 313 n2 = n; 314 315 do { 316 swap_zone = zinit( 317 "SWAPMETA", 318 sizeof(struct swblock), 319 n, 320 ZONE_INTERRUPT, 321 1); 322 if (swap_zone != NULL) 323 break; 324 /* 325 * if the allocation failed, try a zone two thirds the 326 * size of the previous attempt. 327 */ 328 n -= ((n + 2) / 3); 329 } while (n > 0); 330 331 if (swap_zone == NULL) 332 panic("swap_pager_swap_init: swap_zone == NULL"); 333 if (n2 != n) 334 printf("Swap zone entries reduced from %d to %d.\n", n2, n); 335 n2 = n; 336 337 /* 338 * Initialize our meta-data hash table. The swapper does not need to 339 * be quite as efficient as the VM system, so we do not use an 340 * oversized hash table. 341 * 342 * n: size of hash table, must be power of 2 343 * swhash_mask: hash table index mask 344 */ 345 346 for (n = 1; n < n2 / 8; n *= 2) 347 ; 348 349 swhash = malloc(sizeof(struct swblock *) * n, M_VMPGDATA, M_WAITOK); 350 bzero(swhash, sizeof(struct swblock *) * n); 351 352 swhash_mask = n - 1; 353 } 354 355 /* 356 * SWAP_PAGER_ALLOC() - allocate a new OBJT_SWAP VM object and instantiate 357 * its metadata structures. 358 * 359 * This routine is called from the mmap and fork code to create a new 360 * OBJT_SWAP object. We do this by creating an OBJT_DEFAULT object 361 * and then converting it with swp_pager_meta_build(). 362 * 363 * This routine may block in vm_object_allocate() and create a named 364 * object lookup race, so we must interlock. We must also run at 365 * splvm() for the object lookup to handle races with interrupts, but 366 * we do not have to maintain splvm() in between the lookup and the 367 * add because (I believe) it is not possible to attempt to create 368 * a new swap object w/handle when a default object with that handle 369 * already exists. 370 */ 371 372 static vm_object_t 373 swap_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot, 374 vm_ooffset_t offset) 375 { 376 vm_object_t object; 377 378 if (handle) { 379 /* 380 * Reference existing named region or allocate new one. There 381 * should not be a race here against swp_pager_meta_build() 382 * as called from vm_page_remove() in regards to the lookup 383 * of the handle. 384 */ 385 386 while (sw_alloc_interlock) { 387 sw_alloc_interlock = -1; 388 tsleep(&sw_alloc_interlock, 0, "swpalc", 0); 389 } 390 sw_alloc_interlock = 1; 391 392 object = vm_pager_object_lookup(NOBJLIST(handle), handle); 393 394 if (object != NULL) { 395 vm_object_reference(object); 396 } else { 397 object = vm_object_allocate(OBJT_DEFAULT, 398 OFF_TO_IDX(offset + PAGE_MASK + size)); 399 object->handle = handle; 400 401 swp_pager_meta_build(object, 0, SWAPBLK_NONE); 402 } 403 404 if (sw_alloc_interlock < 0) 405 wakeup(&sw_alloc_interlock); 406 407 sw_alloc_interlock = 0; 408 } else { 409 object = vm_object_allocate(OBJT_DEFAULT, 410 OFF_TO_IDX(offset + PAGE_MASK + size)); 411 412 swp_pager_meta_build(object, 0, SWAPBLK_NONE); 413 } 414 415 return (object); 416 } 417 418 /* 419 * SWAP_PAGER_DEALLOC() - remove swap metadata from object 420 * 421 * The swap backing for the object is destroyed. The code is 422 * designed such that we can reinstantiate it later, but this 423 * routine is typically called only when the entire object is 424 * about to be destroyed. 425 * 426 * This routine may block, but no longer does. 427 * 428 * The object must be locked or unreferenceable. 429 */ 430 431 static void 432 swap_pager_dealloc(vm_object_t object) 433 { 434 int s; 435 436 /* 437 * Remove from list right away so lookups will fail if we block for 438 * pageout completion. 439 */ 440 441 if (object->handle == NULL) { 442 TAILQ_REMOVE(&swap_pager_un_object_list, object, pager_object_list); 443 } else { 444 TAILQ_REMOVE(NOBJLIST(object->handle), object, pager_object_list); 445 } 446 447 vm_object_pip_wait(object, "swpdea"); 448 449 /* 450 * Free all remaining metadata. We only bother to free it from 451 * the swap meta data. We do not attempt to free swapblk's still 452 * associated with vm_page_t's for this object. We do not care 453 * if paging is still in progress on some objects. 454 */ 455 s = splvm(); 456 swp_pager_meta_free_all(object); 457 splx(s); 458 } 459 460 /************************************************************************ 461 * SWAP PAGER BITMAP ROUTINES * 462 ************************************************************************/ 463 464 /* 465 * SWP_PAGER_GETSWAPSPACE() - allocate raw swap space 466 * 467 * Allocate swap for the requested number of pages. The starting 468 * swap block number (a page index) is returned or SWAPBLK_NONE 469 * if the allocation failed. 470 * 471 * Also has the side effect of advising that somebody made a mistake 472 * when they configured swap and didn't configure enough. 473 * 474 * Must be called at splvm() to avoid races with bitmap frees from 475 * vm_page_remove() aka swap_pager_page_removed(). 476 * 477 * This routine may not block 478 * This routine must be called at splvm(). 479 */ 480 481 static __inline daddr_t 482 swp_pager_getswapspace(int npages) 483 { 484 daddr_t blk; 485 486 if ((blk = blist_alloc(swapblist, npages)) == SWAPBLK_NONE) { 487 if (swap_pager_full != 2) { 488 printf("swap_pager_getswapspace: failed\n"); 489 swap_pager_full = 2; 490 swap_pager_almost_full = 1; 491 } 492 } else { 493 vm_swap_size -= npages; 494 swp_sizecheck(); 495 } 496 return(blk); 497 } 498 499 /* 500 * SWP_PAGER_FREESWAPSPACE() - free raw swap space 501 * 502 * This routine returns the specified swap blocks back to the bitmap. 503 * 504 * Note: This routine may not block (it could in the old swap code), 505 * and through the use of the new blist routines it does not block. 506 * 507 * We must be called at splvm() to avoid races with bitmap frees from 508 * vm_page_remove() aka swap_pager_page_removed(). 509 * 510 * This routine may not block 511 * This routine must be called at splvm(). 512 */ 513 514 static __inline void 515 swp_pager_freeswapspace(daddr_t blk, int npages) 516 { 517 blist_free(swapblist, blk, npages); 518 vm_swap_size += npages; 519 swp_sizecheck(); 520 } 521 522 /* 523 * SWAP_PAGER_FREESPACE() - frees swap blocks associated with a page 524 * range within an object. 525 * 526 * This is a globally accessible routine. 527 * 528 * This routine removes swapblk assignments from swap metadata. 529 * 530 * The external callers of this routine typically have already destroyed 531 * or renamed vm_page_t's associated with this range in the object so 532 * we should be ok. 533 * 534 * This routine may be called at any spl. We up our spl to splvm temporarily 535 * in order to perform the metadata removal. 536 */ 537 538 void 539 swap_pager_freespace(vm_object_t object, vm_pindex_t start, vm_size_t size) 540 { 541 int s = splvm(); 542 swp_pager_meta_free(object, start, size); 543 splx(s); 544 } 545 546 /* 547 * SWAP_PAGER_RESERVE() - reserve swap blocks in object 548 * 549 * Assigns swap blocks to the specified range within the object. The 550 * swap blocks are not zerod. Any previous swap assignment is destroyed. 551 * 552 * Returns 0 on success, -1 on failure. 553 */ 554 555 int 556 swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_size_t size) 557 { 558 int s; 559 int n = 0; 560 daddr_t blk = SWAPBLK_NONE; 561 vm_pindex_t beg = start; /* save start index */ 562 563 s = splvm(); 564 while (size) { 565 if (n == 0) { 566 n = BLIST_MAX_ALLOC; 567 while ((blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE) { 568 n >>= 1; 569 if (n == 0) { 570 swp_pager_meta_free(object, beg, start - beg); 571 splx(s); 572 return(-1); 573 } 574 } 575 } 576 swp_pager_meta_build(object, start, blk); 577 --size; 578 ++start; 579 ++blk; 580 --n; 581 } 582 swp_pager_meta_free(object, start, n); 583 splx(s); 584 return(0); 585 } 586 587 /* 588 * SWAP_PAGER_COPY() - copy blocks from source pager to destination pager 589 * and destroy the source. 590 * 591 * Copy any valid swapblks from the source to the destination. In 592 * cases where both the source and destination have a valid swapblk, 593 * we keep the destination's. 594 * 595 * This routine is allowed to block. It may block allocating metadata 596 * indirectly through swp_pager_meta_build() or if paging is still in 597 * progress on the source. 598 * 599 * This routine can be called at any spl 600 * 601 * XXX vm_page_collapse() kinda expects us not to block because we 602 * supposedly do not need to allocate memory, but for the moment we 603 * *may* have to get a little memory from the zone allocator, but 604 * it is taken from the interrupt memory. We should be ok. 605 * 606 * The source object contains no vm_page_t's (which is just as well) 607 * 608 * The source object is of type OBJT_SWAP. 609 * 610 * The source and destination objects must be locked or 611 * inaccessible (XXX are they ?) 612 */ 613 614 void 615 swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject, 616 vm_pindex_t offset, int destroysource) 617 { 618 vm_pindex_t i; 619 int s; 620 621 s = splvm(); 622 623 /* 624 * If destroysource is set, we remove the source object from the 625 * swap_pager internal queue now. 626 */ 627 628 if (destroysource) { 629 if (srcobject->handle == NULL) { 630 TAILQ_REMOVE( 631 &swap_pager_un_object_list, 632 srcobject, 633 pager_object_list 634 ); 635 } else { 636 TAILQ_REMOVE( 637 NOBJLIST(srcobject->handle), 638 srcobject, 639 pager_object_list 640 ); 641 } 642 } 643 644 /* 645 * transfer source to destination. 646 */ 647 648 for (i = 0; i < dstobject->size; ++i) { 649 daddr_t dstaddr; 650 651 /* 652 * Locate (without changing) the swapblk on the destination, 653 * unless it is invalid in which case free it silently, or 654 * if the destination is a resident page, in which case the 655 * source is thrown away. 656 */ 657 658 dstaddr = swp_pager_meta_ctl(dstobject, i, 0); 659 660 if (dstaddr == SWAPBLK_NONE) { 661 /* 662 * Destination has no swapblk and is not resident, 663 * copy source. 664 */ 665 daddr_t srcaddr; 666 667 srcaddr = swp_pager_meta_ctl( 668 srcobject, 669 i + offset, 670 SWM_POP 671 ); 672 673 if (srcaddr != SWAPBLK_NONE) 674 swp_pager_meta_build(dstobject, i, srcaddr); 675 } else { 676 /* 677 * Destination has valid swapblk or it is represented 678 * by a resident page. We destroy the sourceblock. 679 */ 680 681 swp_pager_meta_ctl(srcobject, i + offset, SWM_FREE); 682 } 683 } 684 685 /* 686 * Free left over swap blocks in source. 687 * 688 * We have to revert the type to OBJT_DEFAULT so we do not accidently 689 * double-remove the object from the swap queues. 690 */ 691 692 if (destroysource) { 693 swp_pager_meta_free_all(srcobject); 694 /* 695 * Reverting the type is not necessary, the caller is going 696 * to destroy srcobject directly, but I'm doing it here 697 * for consistency since we've removed the object from its 698 * queues. 699 */ 700 srcobject->type = OBJT_DEFAULT; 701 } 702 splx(s); 703 } 704 705 /* 706 * SWAP_PAGER_HASPAGE() - determine if we have good backing store for 707 * the requested page. 708 * 709 * We determine whether good backing store exists for the requested 710 * page and return TRUE if it does, FALSE if it doesn't. 711 * 712 * If TRUE, we also try to determine how much valid, contiguous backing 713 * store exists before and after the requested page within a reasonable 714 * distance. We do not try to restrict it to the swap device stripe 715 * (that is handled in getpages/putpages). It probably isn't worth 716 * doing here. 717 */ 718 719 boolean_t 720 swap_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before, 721 int *after) 722 { 723 daddr_t blk0; 724 int s; 725 726 /* 727 * do we have good backing store at the requested index ? 728 */ 729 730 s = splvm(); 731 blk0 = swp_pager_meta_ctl(object, pindex, 0); 732 733 if (blk0 == SWAPBLK_NONE) { 734 splx(s); 735 if (before) 736 *before = 0; 737 if (after) 738 *after = 0; 739 return (FALSE); 740 } 741 742 /* 743 * find backwards-looking contiguous good backing store 744 */ 745 746 if (before != NULL) { 747 int i; 748 749 for (i = 1; i < (SWB_NPAGES/2); ++i) { 750 daddr_t blk; 751 752 if (i > pindex) 753 break; 754 blk = swp_pager_meta_ctl(object, pindex - i, 0); 755 if (blk != blk0 - i) 756 break; 757 } 758 *before = (i - 1); 759 } 760 761 /* 762 * find forward-looking contiguous good backing store 763 */ 764 765 if (after != NULL) { 766 int i; 767 768 for (i = 1; i < (SWB_NPAGES/2); ++i) { 769 daddr_t blk; 770 771 blk = swp_pager_meta_ctl(object, pindex + i, 0); 772 if (blk != blk0 + i) 773 break; 774 } 775 *after = (i - 1); 776 } 777 splx(s); 778 return (TRUE); 779 } 780 781 /* 782 * SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page 783 * 784 * This removes any associated swap backing store, whether valid or 785 * not, from the page. 786 * 787 * This routine is typically called when a page is made dirty, at 788 * which point any associated swap can be freed. MADV_FREE also 789 * calls us in a special-case situation 790 * 791 * NOTE!!! If the page is clean and the swap was valid, the caller 792 * should make the page dirty before calling this routine. This routine 793 * does NOT change the m->dirty status of the page. Also: MADV_FREE 794 * depends on it. 795 * 796 * This routine may not block 797 * This routine must be called at splvm() 798 */ 799 800 static void 801 swap_pager_unswapped(vm_page_t m) 802 { 803 swp_pager_meta_ctl(m->object, m->pindex, SWM_FREE); 804 } 805 806 /* 807 * SWAP_PAGER_STRATEGY() - read, write, free blocks 808 * 809 * This implements the vm_pager_strategy() interface to swap and allows 810 * other parts of the system to directly access swap as backing store 811 * through vm_objects of type OBJT_SWAP. This is intended to be a 812 * cacheless interface ( i.e. caching occurs at higher levels ). 813 * Therefore we do not maintain any resident pages. All I/O goes 814 * directly to and from the swap device. 815 * 816 * Note that b_blkno is scaled for PAGE_SIZE 817 * 818 * We currently attempt to run I/O synchronously or asynchronously as 819 * the caller requests. This isn't perfect because we loose error 820 * sequencing when we run multiple ops in parallel to satisfy a request. 821 * But this is swap, so we let it all hang out. 822 */ 823 824 static void 825 swap_pager_strategy(vm_object_t object, struct buf *bp) 826 { 827 vm_pindex_t start; 828 int count; 829 int s; 830 char *data; 831 struct buf *nbp = NULL; 832 833 if (bp->b_bcount & PAGE_MASK) { 834 bp->b_error = EINVAL; 835 bp->b_flags |= B_ERROR | B_INVAL; 836 biodone(bp); 837 printf("swap_pager_strategy: bp %p b_vp %p blk %d size %d, not page bounded\n", bp, bp->b_vp, (int)bp->b_pblkno, (int)bp->b_bcount); 838 return; 839 } 840 841 /* 842 * Clear error indication, initialize page index, count, data pointer. 843 */ 844 845 bp->b_error = 0; 846 bp->b_flags &= ~B_ERROR; 847 bp->b_resid = bp->b_bcount; 848 849 start = bp->b_pblkno; 850 count = howmany(bp->b_bcount, PAGE_SIZE); 851 data = bp->b_data; 852 853 s = splvm(); 854 855 /* 856 * Deal with B_FREEBUF 857 */ 858 859 if (bp->b_flags & B_FREEBUF) { 860 /* 861 * FREE PAGE(s) - destroy underlying swap that is no longer 862 * needed. 863 */ 864 swp_pager_meta_free(object, start, count); 865 splx(s); 866 bp->b_resid = 0; 867 biodone(bp); 868 return; 869 } 870 871 /* 872 * Execute read or write 873 */ 874 875 while (count > 0) { 876 daddr_t blk; 877 878 /* 879 * Obtain block. If block not found and writing, allocate a 880 * new block and build it into the object. 881 */ 882 883 blk = swp_pager_meta_ctl(object, start, 0); 884 if ((blk == SWAPBLK_NONE) && (bp->b_flags & B_READ) == 0) { 885 blk = swp_pager_getswapspace(1); 886 if (blk == SWAPBLK_NONE) { 887 bp->b_error = ENOMEM; 888 bp->b_flags |= B_ERROR; 889 break; 890 } 891 swp_pager_meta_build(object, start, blk); 892 } 893 894 /* 895 * Do we have to flush our current collection? Yes if: 896 * 897 * - no swap block at this index 898 * - swap block is not contiguous 899 * - we cross a physical disk boundry in the 900 * stripe. 901 */ 902 903 if ( 904 nbp && (nbp->b_blkno + btoc(nbp->b_bcount) != blk || 905 ((nbp->b_blkno ^ blk) & dmmax_mask) 906 ) 907 ) { 908 splx(s); 909 if (bp->b_flags & B_READ) { 910 ++mycpu->gd_cnt.v_swapin; 911 mycpu->gd_cnt.v_swappgsin += btoc(nbp->b_bcount); 912 } else { 913 ++mycpu->gd_cnt.v_swapout; 914 mycpu->gd_cnt.v_swappgsout += btoc(nbp->b_bcount); 915 nbp->b_dirtyend = nbp->b_bcount; 916 } 917 flushchainbuf(nbp); 918 s = splvm(); 919 nbp = NULL; 920 } 921 922 /* 923 * Add new swapblk to nbp, instantiating nbp if necessary. 924 * Zero-fill reads are able to take a shortcut. 925 */ 926 927 if (blk == SWAPBLK_NONE) { 928 /* 929 * We can only get here if we are reading. Since 930 * we are at splvm() we can safely modify b_resid, 931 * even if chain ops are in progress. 932 */ 933 bzero(data, PAGE_SIZE); 934 bp->b_resid -= PAGE_SIZE; 935 } else { 936 if (nbp == NULL) { 937 nbp = getchainbuf(bp, swapdev_vp, (bp->b_flags & B_READ) | B_ASYNC); 938 nbp->b_blkno = blk; 939 nbp->b_bcount = 0; 940 nbp->b_data = data; 941 } 942 nbp->b_bcount += PAGE_SIZE; 943 } 944 --count; 945 ++start; 946 data += PAGE_SIZE; 947 } 948 949 /* 950 * Flush out last buffer 951 */ 952 953 splx(s); 954 955 if (nbp) { 956 if ((bp->b_flags & B_ASYNC) == 0) 957 nbp->b_flags &= ~B_ASYNC; 958 if (nbp->b_flags & B_READ) { 959 ++mycpu->gd_cnt.v_swapin; 960 mycpu->gd_cnt.v_swappgsin += btoc(nbp->b_bcount); 961 } else { 962 ++mycpu->gd_cnt.v_swapout; 963 mycpu->gd_cnt.v_swappgsout += btoc(nbp->b_bcount); 964 nbp->b_dirtyend = nbp->b_bcount; 965 } 966 flushchainbuf(nbp); 967 /* nbp = NULL; */ 968 } 969 970 /* 971 * Wait for completion. 972 */ 973 974 if (bp->b_flags & B_ASYNC) { 975 autochaindone(bp); 976 } else { 977 waitchainbuf(bp, 0, 1); 978 } 979 } 980 981 /* 982 * SWAP_PAGER_GETPAGES() - bring pages in from swap 983 * 984 * Attempt to retrieve (m, count) pages from backing store, but make 985 * sure we retrieve at least m[reqpage]. We try to load in as large 986 * a chunk surrounding m[reqpage] as is contiguous in swap and which 987 * belongs to the same object. 988 * 989 * The code is designed for asynchronous operation and 990 * immediate-notification of 'reqpage' but tends not to be 991 * used that way. Please do not optimize-out this algorithmic 992 * feature, I intend to improve on it in the future. 993 * 994 * The parent has a single vm_object_pip_add() reference prior to 995 * calling us and we should return with the same. 996 * 997 * The parent has BUSY'd the pages. We should return with 'm' 998 * left busy, but the others adjusted. 999 */ 1000 1001 static int 1002 swap_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage) 1003 { 1004 struct buf *bp; 1005 vm_page_t mreq; 1006 int s; 1007 int i; 1008 int j; 1009 daddr_t blk; 1010 vm_offset_t kva; 1011 vm_pindex_t lastpindex; 1012 1013 mreq = m[reqpage]; 1014 1015 if (mreq->object != object) { 1016 panic("swap_pager_getpages: object mismatch %p/%p", 1017 object, 1018 mreq->object 1019 ); 1020 } 1021 /* 1022 * Calculate range to retrieve. The pages have already been assigned 1023 * their swapblks. We require a *contiguous* range that falls entirely 1024 * within a single device stripe. If we do not supply it, bad things 1025 * happen. Note that blk, iblk & jblk can be SWAPBLK_NONE, but the 1026 * loops are set up such that the case(s) are handled implicitly. 1027 * 1028 * The swp_*() calls must be made at splvm(). vm_page_free() does 1029 * not need to be, but it will go a little faster if it is. 1030 */ 1031 1032 s = splvm(); 1033 blk = swp_pager_meta_ctl(mreq->object, mreq->pindex, 0); 1034 1035 for (i = reqpage - 1; i >= 0; --i) { 1036 daddr_t iblk; 1037 1038 iblk = swp_pager_meta_ctl(m[i]->object, m[i]->pindex, 0); 1039 if (blk != iblk + (reqpage - i)) 1040 break; 1041 if ((blk ^ iblk) & dmmax_mask) 1042 break; 1043 } 1044 ++i; 1045 1046 for (j = reqpage + 1; j < count; ++j) { 1047 daddr_t jblk; 1048 1049 jblk = swp_pager_meta_ctl(m[j]->object, m[j]->pindex, 0); 1050 if (blk != jblk - (j - reqpage)) 1051 break; 1052 if ((blk ^ jblk) & dmmax_mask) 1053 break; 1054 } 1055 1056 /* 1057 * free pages outside our collection range. Note: we never free 1058 * mreq, it must remain busy throughout. 1059 */ 1060 1061 { 1062 int k; 1063 1064 for (k = 0; k < i; ++k) 1065 vm_page_free(m[k]); 1066 for (k = j; k < count; ++k) 1067 vm_page_free(m[k]); 1068 } 1069 splx(s); 1070 1071 1072 /* 1073 * Return VM_PAGER_FAIL if we have nothing to do. Return mreq 1074 * still busy, but the others unbusied. 1075 */ 1076 1077 if (blk == SWAPBLK_NONE) 1078 return(VM_PAGER_FAIL); 1079 1080 /* 1081 * Get a swap buffer header to perform the IO 1082 */ 1083 1084 bp = getpbuf(&nsw_rcount); 1085 kva = (vm_offset_t) bp->b_data; 1086 1087 /* 1088 * map our page(s) into kva for input 1089 * 1090 * NOTE: B_PAGING is set by pbgetvp() 1091 */ 1092 1093 pmap_qenter(kva, m + i, j - i); 1094 1095 bp->b_flags = B_READ | B_CALL; 1096 bp->b_iodone = swp_pager_async_iodone; 1097 bp->b_data = (caddr_t) kva; 1098 bp->b_blkno = blk - (reqpage - i); 1099 bp->b_bcount = PAGE_SIZE * (j - i); 1100 bp->b_bufsize = PAGE_SIZE * (j - i); 1101 bp->b_pager.pg_reqpage = reqpage - i; 1102 1103 { 1104 int k; 1105 1106 for (k = i; k < j; ++k) { 1107 bp->b_pages[k - i] = m[k]; 1108 vm_page_flag_set(m[k], PG_SWAPINPROG); 1109 } 1110 } 1111 bp->b_npages = j - i; 1112 1113 pbgetvp(swapdev_vp, bp); 1114 1115 mycpu->gd_cnt.v_swapin++; 1116 mycpu->gd_cnt.v_swappgsin += bp->b_npages; 1117 1118 /* 1119 * We still hold the lock on mreq, and our automatic completion routine 1120 * does not remove it. 1121 */ 1122 1123 vm_object_pip_add(mreq->object, bp->b_npages); 1124 lastpindex = m[j-1]->pindex; 1125 1126 /* 1127 * perform the I/O. NOTE!!! bp cannot be considered valid after 1128 * this point because we automatically release it on completion. 1129 * Instead, we look at the one page we are interested in which we 1130 * still hold a lock on even through the I/O completion. 1131 * 1132 * The other pages in our m[] array are also released on completion, 1133 * so we cannot assume they are valid anymore either. 1134 * 1135 * NOTE: b_blkno is destroyed by the call to VOP_STRATEGY 1136 */ 1137 1138 BUF_KERNPROC(bp); 1139 VOP_STRATEGY(bp->b_vp, bp); 1140 1141 /* 1142 * wait for the page we want to complete. PG_SWAPINPROG is always 1143 * cleared on completion. If an I/O error occurs, SWAPBLK_NONE 1144 * is set in the meta-data. 1145 */ 1146 1147 s = splvm(); 1148 1149 while ((mreq->flags & PG_SWAPINPROG) != 0) { 1150 vm_page_flag_set(mreq, PG_WANTED | PG_REFERENCED); 1151 mycpu->gd_cnt.v_intrans++; 1152 if (tsleep(mreq, 0, "swread", hz*20)) { 1153 printf( 1154 "swap_pager: indefinite wait buffer: device:" 1155 " %s, blkno: %ld, size: %ld\n", 1156 devtoname(bp->b_dev), (long)bp->b_blkno, 1157 bp->b_bcount 1158 ); 1159 } 1160 } 1161 1162 splx(s); 1163 1164 /* 1165 * mreq is left bussied after completion, but all the other pages 1166 * are freed. If we had an unrecoverable read error the page will 1167 * not be valid. 1168 */ 1169 1170 if (mreq->valid != VM_PAGE_BITS_ALL) { 1171 return(VM_PAGER_ERROR); 1172 } else { 1173 return(VM_PAGER_OK); 1174 } 1175 1176 /* 1177 * A final note: in a low swap situation, we cannot deallocate swap 1178 * and mark a page dirty here because the caller is likely to mark 1179 * the page clean when we return, causing the page to possibly revert 1180 * to all-zero's later. 1181 */ 1182 } 1183 1184 /* 1185 * swap_pager_putpages: 1186 * 1187 * Assign swap (if necessary) and initiate I/O on the specified pages. 1188 * 1189 * We support both OBJT_DEFAULT and OBJT_SWAP objects. DEFAULT objects 1190 * are automatically converted to SWAP objects. 1191 * 1192 * In a low memory situation we may block in VOP_STRATEGY(), but the new 1193 * vm_page reservation system coupled with properly written VFS devices 1194 * should ensure that no low-memory deadlock occurs. This is an area 1195 * which needs work. 1196 * 1197 * The parent has N vm_object_pip_add() references prior to 1198 * calling us and will remove references for rtvals[] that are 1199 * not set to VM_PAGER_PEND. We need to remove the rest on I/O 1200 * completion. 1201 * 1202 * The parent has soft-busy'd the pages it passes us and will unbusy 1203 * those whos rtvals[] entry is not set to VM_PAGER_PEND on return. 1204 * We need to unbusy the rest on I/O completion. 1205 */ 1206 1207 void 1208 swap_pager_putpages(vm_object_t object, vm_page_t *m, int count, boolean_t sync, 1209 int *rtvals) 1210 { 1211 int i; 1212 int n = 0; 1213 1214 if (count && m[0]->object != object) { 1215 panic("swap_pager_getpages: object mismatch %p/%p", 1216 object, 1217 m[0]->object 1218 ); 1219 } 1220 /* 1221 * Step 1 1222 * 1223 * Turn object into OBJT_SWAP 1224 * check for bogus sysops 1225 * force sync if not pageout process 1226 */ 1227 1228 if (object->type != OBJT_SWAP) 1229 swp_pager_meta_build(object, 0, SWAPBLK_NONE); 1230 1231 if (curthread != pagethread) 1232 sync = TRUE; 1233 1234 /* 1235 * Step 2 1236 * 1237 * Update nsw parameters from swap_async_max sysctl values. 1238 * Do not let the sysop crash the machine with bogus numbers. 1239 */ 1240 1241 if (swap_async_max != nsw_wcount_async_max) { 1242 int n; 1243 int s; 1244 1245 /* 1246 * limit range 1247 */ 1248 if ((n = swap_async_max) > nswbuf / 2) 1249 n = nswbuf / 2; 1250 if (n < 1) 1251 n = 1; 1252 swap_async_max = n; 1253 1254 /* 1255 * Adjust difference ( if possible ). If the current async 1256 * count is too low, we may not be able to make the adjustment 1257 * at this time. 1258 */ 1259 s = splvm(); 1260 n -= nsw_wcount_async_max; 1261 if (nsw_wcount_async + n >= 0) { 1262 nsw_wcount_async += n; 1263 nsw_wcount_async_max += n; 1264 wakeup(&nsw_wcount_async); 1265 } 1266 splx(s); 1267 } 1268 1269 /* 1270 * Step 3 1271 * 1272 * Assign swap blocks and issue I/O. We reallocate swap on the fly. 1273 * The page is left dirty until the pageout operation completes 1274 * successfully. 1275 */ 1276 1277 for (i = 0; i < count; i += n) { 1278 int s; 1279 int j; 1280 struct buf *bp; 1281 daddr_t blk; 1282 1283 /* 1284 * Maximum I/O size is limited by a number of factors. 1285 */ 1286 1287 n = min(BLIST_MAX_ALLOC, count - i); 1288 n = min(n, nsw_cluster_max); 1289 1290 s = splvm(); 1291 1292 /* 1293 * Get biggest block of swap we can. If we fail, fall 1294 * back and try to allocate a smaller block. Don't go 1295 * overboard trying to allocate space if it would overly 1296 * fragment swap. 1297 */ 1298 while ( 1299 (blk = swp_pager_getswapspace(n)) == SWAPBLK_NONE && 1300 n > 4 1301 ) { 1302 n >>= 1; 1303 } 1304 if (blk == SWAPBLK_NONE) { 1305 for (j = 0; j < n; ++j) 1306 rtvals[i+j] = VM_PAGER_FAIL; 1307 splx(s); 1308 continue; 1309 } 1310 1311 /* 1312 * The I/O we are constructing cannot cross a physical 1313 * disk boundry in the swap stripe. Note: we are still 1314 * at splvm(). 1315 */ 1316 if ((blk ^ (blk + n)) & dmmax_mask) { 1317 j = ((blk + dmmax) & dmmax_mask) - blk; 1318 swp_pager_freeswapspace(blk + j, n - j); 1319 n = j; 1320 } 1321 1322 /* 1323 * All I/O parameters have been satisfied, build the I/O 1324 * request and assign the swap space. 1325 * 1326 * NOTE: B_PAGING is set by pbgetvp() 1327 */ 1328 1329 if (sync == TRUE) { 1330 bp = getpbuf(&nsw_wcount_sync); 1331 bp->b_flags = B_CALL; 1332 } else { 1333 bp = getpbuf(&nsw_wcount_async); 1334 bp->b_flags = B_CALL | B_ASYNC; 1335 } 1336 bp->b_spc = NULL; /* not used, but NULL-out anyway */ 1337 1338 pmap_qenter((vm_offset_t)bp->b_data, &m[i], n); 1339 1340 bp->b_bcount = PAGE_SIZE * n; 1341 bp->b_bufsize = PAGE_SIZE * n; 1342 bp->b_blkno = blk; 1343 1344 pbgetvp(swapdev_vp, bp); 1345 1346 for (j = 0; j < n; ++j) { 1347 vm_page_t mreq = m[i+j]; 1348 1349 swp_pager_meta_build( 1350 mreq->object, 1351 mreq->pindex, 1352 blk + j 1353 ); 1354 vm_page_dirty(mreq); 1355 rtvals[i+j] = VM_PAGER_OK; 1356 1357 vm_page_flag_set(mreq, PG_SWAPINPROG); 1358 bp->b_pages[j] = mreq; 1359 } 1360 bp->b_npages = n; 1361 /* 1362 * Must set dirty range for NFS to work. 1363 */ 1364 bp->b_dirtyoff = 0; 1365 bp->b_dirtyend = bp->b_bcount; 1366 1367 mycpu->gd_cnt.v_swapout++; 1368 mycpu->gd_cnt.v_swappgsout += bp->b_npages; 1369 swapdev_vp->v_numoutput++; 1370 1371 splx(s); 1372 1373 /* 1374 * asynchronous 1375 * 1376 * NOTE: b_blkno is destroyed by the call to VOP_STRATEGY 1377 */ 1378 1379 if (sync == FALSE) { 1380 bp->b_iodone = swp_pager_async_iodone; 1381 BUF_KERNPROC(bp); 1382 VOP_STRATEGY(bp->b_vp, bp); 1383 1384 for (j = 0; j < n; ++j) 1385 rtvals[i+j] = VM_PAGER_PEND; 1386 continue; 1387 } 1388 1389 /* 1390 * synchronous 1391 * 1392 * NOTE: b_blkno is destroyed by the call to VOP_STRATEGY 1393 */ 1394 1395 bp->b_iodone = swp_pager_sync_iodone; 1396 VOP_STRATEGY(bp->b_vp, bp); 1397 1398 /* 1399 * Wait for the sync I/O to complete, then update rtvals. 1400 * We just set the rtvals[] to VM_PAGER_PEND so we can call 1401 * our async completion routine at the end, thus avoiding a 1402 * double-free. 1403 */ 1404 s = splbio(); 1405 1406 while ((bp->b_flags & B_DONE) == 0) { 1407 tsleep(bp, 0, "swwrt", 0); 1408 } 1409 1410 for (j = 0; j < n; ++j) 1411 rtvals[i+j] = VM_PAGER_PEND; 1412 1413 /* 1414 * Now that we are through with the bp, we can call the 1415 * normal async completion, which frees everything up. 1416 */ 1417 1418 swp_pager_async_iodone(bp); 1419 1420 splx(s); 1421 } 1422 } 1423 1424 /* 1425 * swap_pager_sync_iodone: 1426 * 1427 * Completion routine for synchronous reads and writes from/to swap. 1428 * We just mark the bp is complete and wake up anyone waiting on it. 1429 * 1430 * This routine may not block. This routine is called at splbio() or better. 1431 */ 1432 1433 static void 1434 swp_pager_sync_iodone(struct buf *bp) 1435 { 1436 bp->b_flags |= B_DONE; 1437 bp->b_flags &= ~B_ASYNC; 1438 wakeup(bp); 1439 } 1440 1441 /* 1442 * swp_pager_async_iodone: 1443 * 1444 * Completion routine for asynchronous reads and writes from/to swap. 1445 * Also called manually by synchronous code to finish up a bp. 1446 * 1447 * For READ operations, the pages are PG_BUSY'd. For WRITE operations, 1448 * the pages are vm_page_t->busy'd. For READ operations, we PG_BUSY 1449 * unbusy all pages except the 'main' request page. For WRITE 1450 * operations, we vm_page_t->busy'd unbusy all pages ( we can do this 1451 * because we marked them all VM_PAGER_PEND on return from putpages ). 1452 * 1453 * This routine may not block. 1454 * This routine is called at splbio() or better 1455 * 1456 * We up ourselves to splvm() as required for various vm_page related 1457 * calls. 1458 */ 1459 1460 static void 1461 swp_pager_async_iodone(struct buf *bp) 1462 { 1463 int s; 1464 int i; 1465 vm_object_t object = NULL; 1466 1467 bp->b_flags |= B_DONE; 1468 1469 /* 1470 * report error 1471 */ 1472 1473 if (bp->b_flags & B_ERROR) { 1474 printf( 1475 "swap_pager: I/O error - %s failed; blkno %ld," 1476 "size %ld, error %d\n", 1477 ((bp->b_flags & B_READ) ? "pagein" : "pageout"), 1478 (long)bp->b_blkno, 1479 (long)bp->b_bcount, 1480 bp->b_error 1481 ); 1482 } 1483 1484 /* 1485 * set object, raise to splvm(). 1486 */ 1487 1488 if (bp->b_npages) 1489 object = bp->b_pages[0]->object; 1490 s = splvm(); 1491 1492 /* 1493 * remove the mapping for kernel virtual 1494 */ 1495 1496 pmap_qremove((vm_offset_t)bp->b_data, bp->b_npages); 1497 1498 /* 1499 * cleanup pages. If an error occurs writing to swap, we are in 1500 * very serious trouble. If it happens to be a disk error, though, 1501 * we may be able to recover by reassigning the swap later on. So 1502 * in this case we remove the m->swapblk assignment for the page 1503 * but do not free it in the rlist. The errornous block(s) are thus 1504 * never reallocated as swap. Redirty the page and continue. 1505 */ 1506 1507 for (i = 0; i < bp->b_npages; ++i) { 1508 vm_page_t m = bp->b_pages[i]; 1509 1510 vm_page_flag_clear(m, PG_SWAPINPROG); 1511 1512 if (bp->b_flags & B_ERROR) { 1513 /* 1514 * If an error occurs I'd love to throw the swapblk 1515 * away without freeing it back to swapspace, so it 1516 * can never be used again. But I can't from an 1517 * interrupt. 1518 */ 1519 1520 if (bp->b_flags & B_READ) { 1521 /* 1522 * When reading, reqpage needs to stay 1523 * locked for the parent, but all other 1524 * pages can be freed. We still want to 1525 * wakeup the parent waiting on the page, 1526 * though. ( also: pg_reqpage can be -1 and 1527 * not match anything ). 1528 * 1529 * We have to wake specifically requested pages 1530 * up too because we cleared PG_SWAPINPROG and 1531 * someone may be waiting for that. 1532 * 1533 * NOTE: for reads, m->dirty will probably 1534 * be overridden by the original caller of 1535 * getpages so don't play cute tricks here. 1536 * 1537 * XXX IT IS NOT LEGAL TO FREE THE PAGE HERE 1538 * AS THIS MESSES WITH object->memq, and it is 1539 * not legal to mess with object->memq from an 1540 * interrupt. 1541 */ 1542 1543 m->valid = 0; 1544 vm_page_flag_clear(m, PG_ZERO); 1545 1546 if (i != bp->b_pager.pg_reqpage) 1547 vm_page_free(m); 1548 else 1549 vm_page_flash(m); 1550 /* 1551 * If i == bp->b_pager.pg_reqpage, do not wake 1552 * the page up. The caller needs to. 1553 */ 1554 } else { 1555 /* 1556 * If a write error occurs, reactivate page 1557 * so it doesn't clog the inactive list, 1558 * then finish the I/O. 1559 */ 1560 vm_page_dirty(m); 1561 vm_page_activate(m); 1562 vm_page_io_finish(m); 1563 } 1564 } else if (bp->b_flags & B_READ) { 1565 /* 1566 * For read success, clear dirty bits. Nobody should 1567 * have this page mapped but don't take any chances, 1568 * make sure the pmap modify bits are also cleared. 1569 * 1570 * NOTE: for reads, m->dirty will probably be 1571 * overridden by the original caller of getpages so 1572 * we cannot set them in order to free the underlying 1573 * swap in a low-swap situation. I don't think we'd 1574 * want to do that anyway, but it was an optimization 1575 * that existed in the old swapper for a time before 1576 * it got ripped out due to precisely this problem. 1577 * 1578 * clear PG_ZERO in page. 1579 * 1580 * If not the requested page then deactivate it. 1581 * 1582 * Note that the requested page, reqpage, is left 1583 * busied, but we still have to wake it up. The 1584 * other pages are released (unbusied) by 1585 * vm_page_wakeup(). We do not set reqpage's 1586 * valid bits here, it is up to the caller. 1587 */ 1588 1589 pmap_clear_modify(m); 1590 m->valid = VM_PAGE_BITS_ALL; 1591 vm_page_undirty(m); 1592 vm_page_flag_clear(m, PG_ZERO); 1593 1594 /* 1595 * We have to wake specifically requested pages 1596 * up too because we cleared PG_SWAPINPROG and 1597 * could be waiting for it in getpages. However, 1598 * be sure to not unbusy getpages specifically 1599 * requested page - getpages expects it to be 1600 * left busy. 1601 */ 1602 if (i != bp->b_pager.pg_reqpage) { 1603 vm_page_deactivate(m); 1604 vm_page_wakeup(m); 1605 } else { 1606 vm_page_flash(m); 1607 } 1608 } else { 1609 /* 1610 * For write success, clear the modify and dirty 1611 * status, then finish the I/O ( which decrements the 1612 * busy count and possibly wakes waiter's up ). 1613 */ 1614 pmap_clear_modify(m); 1615 vm_page_undirty(m); 1616 vm_page_io_finish(m); 1617 if (!vm_page_count_severe() || !vm_page_try_to_cache(m)) 1618 vm_page_protect(m, VM_PROT_READ); 1619 } 1620 } 1621 1622 /* 1623 * adjust pip. NOTE: the original parent may still have its own 1624 * pip refs on the object. 1625 */ 1626 1627 if (object) 1628 vm_object_pip_wakeupn(object, bp->b_npages); 1629 1630 /* 1631 * release the physical I/O buffer 1632 */ 1633 1634 relpbuf( 1635 bp, 1636 ((bp->b_flags & B_READ) ? &nsw_rcount : 1637 ((bp->b_flags & B_ASYNC) ? 1638 &nsw_wcount_async : 1639 &nsw_wcount_sync 1640 ) 1641 ) 1642 ); 1643 splx(s); 1644 } 1645 1646 /************************************************************************ 1647 * SWAP META DATA * 1648 ************************************************************************ 1649 * 1650 * These routines manipulate the swap metadata stored in the 1651 * OBJT_SWAP object. All swp_*() routines must be called at 1652 * splvm() because swap can be freed up by the low level vm_page 1653 * code which might be called from interrupts beyond what splbio() covers. 1654 * 1655 * Swap metadata is implemented with a global hash and not directly 1656 * linked into the object. Instead the object simply contains 1657 * appropriate tracking counters. 1658 */ 1659 1660 /* 1661 * SWP_PAGER_HASH() - hash swap meta data 1662 * 1663 * This is an inline helper function which hashes the swapblk given 1664 * the object and page index. It returns a pointer to a pointer 1665 * to the object, or a pointer to a NULL pointer if it could not 1666 * find a swapblk. 1667 * 1668 * This routine must be called at splvm(). 1669 */ 1670 1671 static __inline struct swblock ** 1672 swp_pager_hash(vm_object_t object, vm_pindex_t index) 1673 { 1674 struct swblock **pswap; 1675 struct swblock *swap; 1676 1677 index &= ~SWAP_META_MASK; 1678 pswap = &swhash[(index ^ (int)(intptr_t)object) & swhash_mask]; 1679 1680 while ((swap = *pswap) != NULL) { 1681 if (swap->swb_object == object && 1682 swap->swb_index == index 1683 ) { 1684 break; 1685 } 1686 pswap = &swap->swb_hnext; 1687 } 1688 return(pswap); 1689 } 1690 1691 /* 1692 * SWP_PAGER_META_BUILD() - add swap block to swap meta data for object 1693 * 1694 * We first convert the object to a swap object if it is a default 1695 * object. 1696 * 1697 * The specified swapblk is added to the object's swap metadata. If 1698 * the swapblk is not valid, it is freed instead. Any previously 1699 * assigned swapblk is freed. 1700 * 1701 * This routine must be called at splvm(), except when used to convert 1702 * an OBJT_DEFAULT object into an OBJT_SWAP object. 1703 1704 */ 1705 1706 static void 1707 swp_pager_meta_build( 1708 vm_object_t object, 1709 vm_pindex_t index, 1710 daddr_t swapblk 1711 ) { 1712 struct swblock *swap; 1713 struct swblock **pswap; 1714 1715 /* 1716 * Convert default object to swap object if necessary 1717 */ 1718 1719 if (object->type != OBJT_SWAP) { 1720 object->type = OBJT_SWAP; 1721 object->un_pager.swp.swp_bcount = 0; 1722 1723 if (object->handle != NULL) { 1724 TAILQ_INSERT_TAIL( 1725 NOBJLIST(object->handle), 1726 object, 1727 pager_object_list 1728 ); 1729 } else { 1730 TAILQ_INSERT_TAIL( 1731 &swap_pager_un_object_list, 1732 object, 1733 pager_object_list 1734 ); 1735 } 1736 } 1737 1738 /* 1739 * Locate hash entry. If not found create, but if we aren't adding 1740 * anything just return. If we run out of space in the map we wait 1741 * and, since the hash table may have changed, retry. 1742 */ 1743 1744 retry: 1745 pswap = swp_pager_hash(object, index); 1746 1747 if ((swap = *pswap) == NULL) { 1748 int i; 1749 1750 if (swapblk == SWAPBLK_NONE) 1751 return; 1752 1753 swap = *pswap = zalloc(swap_zone); 1754 if (swap == NULL) { 1755 VM_WAIT; 1756 goto retry; 1757 } 1758 swap->swb_hnext = NULL; 1759 swap->swb_object = object; 1760 swap->swb_index = index & ~SWAP_META_MASK; 1761 swap->swb_count = 0; 1762 1763 ++object->un_pager.swp.swp_bcount; 1764 1765 for (i = 0; i < SWAP_META_PAGES; ++i) 1766 swap->swb_pages[i] = SWAPBLK_NONE; 1767 } 1768 1769 /* 1770 * Delete prior contents of metadata 1771 */ 1772 1773 index &= SWAP_META_MASK; 1774 1775 if (swap->swb_pages[index] != SWAPBLK_NONE) { 1776 swp_pager_freeswapspace(swap->swb_pages[index], 1); 1777 --swap->swb_count; 1778 } 1779 1780 /* 1781 * Enter block into metadata 1782 */ 1783 1784 swap->swb_pages[index] = swapblk; 1785 if (swapblk != SWAPBLK_NONE) 1786 ++swap->swb_count; 1787 } 1788 1789 /* 1790 * SWP_PAGER_META_FREE() - free a range of blocks in the object's swap metadata 1791 * 1792 * The requested range of blocks is freed, with any associated swap 1793 * returned to the swap bitmap. 1794 * 1795 * This routine will free swap metadata structures as they are cleaned 1796 * out. This routine does *NOT* operate on swap metadata associated 1797 * with resident pages. 1798 * 1799 * This routine must be called at splvm() 1800 */ 1801 1802 static void 1803 swp_pager_meta_free(vm_object_t object, vm_pindex_t index, daddr_t count) 1804 { 1805 if (object->type != OBJT_SWAP) 1806 return; 1807 1808 while (count > 0) { 1809 struct swblock **pswap; 1810 struct swblock *swap; 1811 1812 pswap = swp_pager_hash(object, index); 1813 1814 if ((swap = *pswap) != NULL) { 1815 daddr_t v = swap->swb_pages[index & SWAP_META_MASK]; 1816 1817 if (v != SWAPBLK_NONE) { 1818 swp_pager_freeswapspace(v, 1); 1819 swap->swb_pages[index & SWAP_META_MASK] = 1820 SWAPBLK_NONE; 1821 if (--swap->swb_count == 0) { 1822 *pswap = swap->swb_hnext; 1823 zfree(swap_zone, swap); 1824 --object->un_pager.swp.swp_bcount; 1825 } 1826 } 1827 --count; 1828 ++index; 1829 } else { 1830 int n = SWAP_META_PAGES - (index & SWAP_META_MASK); 1831 count -= n; 1832 index += n; 1833 } 1834 } 1835 } 1836 1837 /* 1838 * SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object 1839 * 1840 * This routine locates and destroys all swap metadata associated with 1841 * an object. 1842 * 1843 * This routine must be called at splvm() 1844 */ 1845 1846 static void 1847 swp_pager_meta_free_all(vm_object_t object) 1848 { 1849 daddr_t index = 0; 1850 1851 if (object->type != OBJT_SWAP) 1852 return; 1853 1854 while (object->un_pager.swp.swp_bcount) { 1855 struct swblock **pswap; 1856 struct swblock *swap; 1857 1858 pswap = swp_pager_hash(object, index); 1859 if ((swap = *pswap) != NULL) { 1860 int i; 1861 1862 for (i = 0; i < SWAP_META_PAGES; ++i) { 1863 daddr_t v = swap->swb_pages[i]; 1864 if (v != SWAPBLK_NONE) { 1865 --swap->swb_count; 1866 swp_pager_freeswapspace(v, 1); 1867 } 1868 } 1869 if (swap->swb_count != 0) 1870 panic("swap_pager_meta_free_all: swb_count != 0"); 1871 *pswap = swap->swb_hnext; 1872 zfree(swap_zone, swap); 1873 --object->un_pager.swp.swp_bcount; 1874 } 1875 index += SWAP_META_PAGES; 1876 if (index > 0x20000000) 1877 panic("swp_pager_meta_free_all: failed to locate all swap meta blocks"); 1878 } 1879 } 1880 1881 /* 1882 * SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data. 1883 * 1884 * This routine is capable of looking up, popping, or freeing 1885 * swapblk assignments in the swap meta data or in the vm_page_t. 1886 * The routine typically returns the swapblk being looked-up, or popped, 1887 * or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block 1888 * was invalid. This routine will automatically free any invalid 1889 * meta-data swapblks. 1890 * 1891 * It is not possible to store invalid swapblks in the swap meta data 1892 * (other then a literal 'SWAPBLK_NONE'), so we don't bother checking. 1893 * 1894 * When acting on a busy resident page and paging is in progress, we 1895 * have to wait until paging is complete but otherwise can act on the 1896 * busy page. 1897 * 1898 * This routine must be called at splvm(). 1899 * 1900 * SWM_FREE remove and free swap block from metadata 1901 * SWM_POP remove from meta data but do not free.. pop it out 1902 */ 1903 1904 static daddr_t 1905 swp_pager_meta_ctl( 1906 vm_object_t object, 1907 vm_pindex_t index, 1908 int flags 1909 ) { 1910 struct swblock **pswap; 1911 struct swblock *swap; 1912 daddr_t r1; 1913 1914 /* 1915 * The meta data only exists of the object is OBJT_SWAP 1916 * and even then might not be allocated yet. 1917 */ 1918 1919 if (object->type != OBJT_SWAP) 1920 return(SWAPBLK_NONE); 1921 1922 r1 = SWAPBLK_NONE; 1923 pswap = swp_pager_hash(object, index); 1924 1925 if ((swap = *pswap) != NULL) { 1926 index &= SWAP_META_MASK; 1927 r1 = swap->swb_pages[index]; 1928 1929 if (r1 != SWAPBLK_NONE) { 1930 if (flags & SWM_FREE) { 1931 swp_pager_freeswapspace(r1, 1); 1932 r1 = SWAPBLK_NONE; 1933 } 1934 if (flags & (SWM_FREE|SWM_POP)) { 1935 swap->swb_pages[index] = SWAPBLK_NONE; 1936 if (--swap->swb_count == 0) { 1937 *pswap = swap->swb_hnext; 1938 zfree(swap_zone, swap); 1939 --object->un_pager.swp.swp_bcount; 1940 } 1941 } 1942 } 1943 } 1944 return(r1); 1945 } 1946