1 /* 2 * Copyright (c) 1994,1997 John S. Dyson 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice immediately at the beginning of the file, without modification, 10 * this list of conditions, and the following disclaimer. 11 * 2. Absolutely no warranty of function or purpose is made by the author 12 * John S. Dyson. 13 * 14 * $FreeBSD: src/sys/kern/vfs_bio.c,v 1.242.2.20 2003/05/28 18:38:10 alc Exp $ 15 */ 16 17 /* 18 * this file contains a new buffer I/O scheme implementing a coherent 19 * VM object and buffer cache scheme. Pains have been taken to make 20 * sure that the performance degradation associated with schemes such 21 * as this is not realized. 22 * 23 * Author: John S. Dyson 24 * Significant help during the development and debugging phases 25 * had been provided by David Greenman, also of the FreeBSD core team. 26 * 27 * see man buf(9) for more info. Note that man buf(9) doesn't reflect 28 * the actual buf/bio implementation in DragonFly. 29 */ 30 31 #include <sys/param.h> 32 #include <sys/systm.h> 33 #include <sys/buf.h> 34 #include <sys/conf.h> 35 #include <sys/devicestat.h> 36 #include <sys/eventhandler.h> 37 #include <sys/lock.h> 38 #include <sys/malloc.h> 39 #include <sys/mount.h> 40 #include <sys/kernel.h> 41 #include <sys/kthread.h> 42 #include <sys/proc.h> 43 #include <sys/reboot.h> 44 #include <sys/resourcevar.h> 45 #include <sys/sysctl.h> 46 #include <sys/vmmeter.h> 47 #include <sys/vnode.h> 48 #include <sys/dsched.h> 49 #include <vm/vm.h> 50 #include <vm/vm_param.h> 51 #include <vm/vm_kern.h> 52 #include <vm/vm_pageout.h> 53 #include <vm/vm_page.h> 54 #include <vm/vm_object.h> 55 #include <vm/vm_extern.h> 56 #include <vm/vm_map.h> 57 #include <vm/vm_pager.h> 58 #include <vm/swap_pager.h> 59 60 #include <sys/buf2.h> 61 #include <sys/thread2.h> 62 #include <sys/spinlock2.h> 63 #include <sys/mplock2.h> 64 #include <vm/vm_page2.h> 65 66 #include "opt_ddb.h" 67 #ifdef DDB 68 #include <ddb/ddb.h> 69 #endif 70 71 /* 72 * Buffer queues. 73 */ 74 enum bufq_type { 75 BQUEUE_NONE, /* not on any queue */ 76 BQUEUE_LOCKED, /* locked buffers */ 77 BQUEUE_CLEAN, /* non-B_DELWRI buffers */ 78 BQUEUE_DIRTY, /* B_DELWRI buffers */ 79 BQUEUE_DIRTY_HW, /* B_DELWRI buffers - heavy weight */ 80 BQUEUE_EMPTY, /* empty buffer headers */ 81 82 BUFFER_QUEUES /* number of buffer queues */ 83 }; 84 85 typedef enum bufq_type bufq_type_t; 86 87 #define BD_WAKE_SIZE 16384 88 #define BD_WAKE_MASK (BD_WAKE_SIZE - 1) 89 90 TAILQ_HEAD(bqueues, buf); 91 92 struct bufpcpu { 93 struct spinlock spin; 94 struct bqueues bufqueues[BUFFER_QUEUES]; 95 } __cachealign; 96 97 struct bufpcpu bufpcpu[MAXCPU]; 98 99 static MALLOC_DEFINE(M_BIOBUF, "BIO buffer", "BIO buffer"); 100 101 struct buf *buf; /* buffer header pool */ 102 103 static void vfs_clean_pages(struct buf *bp); 104 static void vfs_clean_one_page(struct buf *bp, int pageno, vm_page_t m); 105 #if 0 106 static void vfs_dirty_one_page(struct buf *bp, int pageno, vm_page_t m); 107 #endif 108 static void vfs_vmio_release(struct buf *bp); 109 static int flushbufqueues(struct buf *marker, bufq_type_t q); 110 static void repurposebuf(struct buf *bp, int size); 111 static vm_page_t bio_page_alloc(struct buf *bp, vm_object_t obj, 112 vm_pindex_t pg, int deficit); 113 114 static void bd_signal(long totalspace); 115 static void buf_daemon(void); 116 static void buf_daemon_hw(void); 117 118 /* 119 * bogus page -- for I/O to/from partially complete buffers 120 * this is a temporary solution to the problem, but it is not 121 * really that bad. it would be better to split the buffer 122 * for input in the case of buffers partially already in memory, 123 * but the code is intricate enough already. 124 */ 125 vm_page_t bogus_page; 126 127 /* 128 * These are all static, but make the ones we export globals so we do 129 * not need to use compiler magic. 130 */ 131 long bufspace; /* atomic ops */ 132 long maxbufspace; 133 static long bufmallocspace; /* atomic ops */ 134 long maxbufmallocspace, lobufspace, hibufspace; 135 static long lorunningspace; 136 static long hirunningspace; 137 static long dirtykvaspace; /* atomic */ 138 long dirtybufspace; /* atomic (global for systat) */ 139 static long dirtybufcount; /* atomic */ 140 static long dirtybufspacehw; /* atomic */ 141 static long dirtybufcounthw; /* atomic */ 142 static long runningbufspace; /* atomic */ 143 static long runningbufcount; /* atomic */ 144 static long repurposedspace; 145 long lodirtybufspace; 146 long hidirtybufspace; 147 static int getnewbufcalls; 148 static int recoverbufcalls; 149 static int needsbuffer; /* atomic */ 150 static int runningbufreq; /* atomic */ 151 static int bd_request; /* atomic */ 152 static int bd_request_hw; /* atomic */ 153 static u_int bd_wake_ary[BD_WAKE_SIZE]; 154 static u_int bd_wake_index; 155 static u_int vm_cycle_point = 40; /* 23-36 will migrate more act->inact */ 156 static int debug_commit; 157 static int debug_bufbio; 158 static long bufcache_bw = 200 * 1024 * 1024; 159 static long bufcache_bw_accum; 160 static int bufcache_bw_ticks; 161 162 static struct thread *bufdaemon_td; 163 static struct thread *bufdaemonhw_td; 164 static u_int lowmempgallocs; 165 static u_int lowmempgfails; 166 static u_int flushperqueue = 1024; 167 static int repurpose_enable; 168 169 /* 170 * Sysctls for operational control of the buffer cache. 171 */ 172 SYSCTL_UINT(_vfs, OID_AUTO, flushperqueue, CTLFLAG_RW, &flushperqueue, 0, 173 "Number of buffers to flush from each per-cpu queue"); 174 SYSCTL_LONG(_vfs, OID_AUTO, lodirtybufspace, CTLFLAG_RW, &lodirtybufspace, 0, 175 "Number of dirty buffers to flush before bufdaemon becomes inactive"); 176 SYSCTL_LONG(_vfs, OID_AUTO, hidirtybufspace, CTLFLAG_RW, &hidirtybufspace, 0, 177 "High watermark used to trigger explicit flushing of dirty buffers"); 178 SYSCTL_LONG(_vfs, OID_AUTO, lorunningspace, CTLFLAG_RW, &lorunningspace, 0, 179 "Minimum amount of buffer space required for active I/O"); 180 SYSCTL_LONG(_vfs, OID_AUTO, hirunningspace, CTLFLAG_RW, &hirunningspace, 0, 181 "Maximum amount of buffer space to usable for active I/O"); 182 SYSCTL_LONG(_vfs, OID_AUTO, bufcache_bw, CTLFLAG_RW, &bufcache_bw, 0, 183 "Buffer-cache -> VM page cache transfer bandwidth"); 184 SYSCTL_UINT(_vfs, OID_AUTO, lowmempgallocs, CTLFLAG_RW, &lowmempgallocs, 0, 185 "Page allocations done during periods of very low free memory"); 186 SYSCTL_UINT(_vfs, OID_AUTO, lowmempgfails, CTLFLAG_RW, &lowmempgfails, 0, 187 "Page allocations which failed during periods of very low free memory"); 188 SYSCTL_UINT(_vfs, OID_AUTO, vm_cycle_point, CTLFLAG_RW, &vm_cycle_point, 0, 189 "Recycle pages to active or inactive queue transition pt 0-64"); 190 SYSCTL_UINT(_vfs, OID_AUTO, repurpose_enable, CTLFLAG_RW, &repurpose_enable, 0, 191 "Enable buffer cache VM repurposing for high-I/O"); 192 /* 193 * Sysctls determining current state of the buffer cache. 194 */ 195 SYSCTL_LONG(_vfs, OID_AUTO, nbuf, CTLFLAG_RD, &nbuf, 0, 196 "Total number of buffers in buffer cache"); 197 SYSCTL_LONG(_vfs, OID_AUTO, dirtykvaspace, CTLFLAG_RD, &dirtykvaspace, 0, 198 "KVA reserved by dirty buffers (all)"); 199 SYSCTL_LONG(_vfs, OID_AUTO, dirtybufspace, CTLFLAG_RD, &dirtybufspace, 0, 200 "Pending bytes of dirty buffers (all)"); 201 SYSCTL_LONG(_vfs, OID_AUTO, dirtybufspacehw, CTLFLAG_RD, &dirtybufspacehw, 0, 202 "Pending bytes of dirty buffers (heavy weight)"); 203 SYSCTL_LONG(_vfs, OID_AUTO, dirtybufcount, CTLFLAG_RD, &dirtybufcount, 0, 204 "Pending number of dirty buffers"); 205 SYSCTL_LONG(_vfs, OID_AUTO, dirtybufcounthw, CTLFLAG_RD, &dirtybufcounthw, 0, 206 "Pending number of dirty buffers (heavy weight)"); 207 SYSCTL_LONG(_vfs, OID_AUTO, runningbufspace, CTLFLAG_RD, &runningbufspace, 0, 208 "I/O bytes currently in progress due to asynchronous writes"); 209 SYSCTL_LONG(_vfs, OID_AUTO, runningbufcount, CTLFLAG_RD, &runningbufcount, 0, 210 "I/O buffers currently in progress due to asynchronous writes"); 211 SYSCTL_LONG(_vfs, OID_AUTO, repurposedspace, CTLFLAG_RD, &repurposedspace, 0, 212 "Buffer-cache memory repurposed in-place"); 213 SYSCTL_LONG(_vfs, OID_AUTO, maxbufspace, CTLFLAG_RD, &maxbufspace, 0, 214 "Hard limit on maximum amount of memory usable for buffer space"); 215 SYSCTL_LONG(_vfs, OID_AUTO, hibufspace, CTLFLAG_RD, &hibufspace, 0, 216 "Soft limit on maximum amount of memory usable for buffer space"); 217 SYSCTL_LONG(_vfs, OID_AUTO, lobufspace, CTLFLAG_RD, &lobufspace, 0, 218 "Minimum amount of memory to reserve for system buffer space"); 219 SYSCTL_LONG(_vfs, OID_AUTO, bufspace, CTLFLAG_RD, &bufspace, 0, 220 "Amount of memory available for buffers"); 221 SYSCTL_LONG(_vfs, OID_AUTO, maxmallocbufspace, CTLFLAG_RD, &maxbufmallocspace, 222 0, "Maximum amount of memory reserved for buffers using malloc"); 223 SYSCTL_LONG(_vfs, OID_AUTO, bufmallocspace, CTLFLAG_RD, &bufmallocspace, 0, 224 "Amount of memory left for buffers using malloc-scheme"); 225 SYSCTL_INT(_vfs, OID_AUTO, getnewbufcalls, CTLFLAG_RD, &getnewbufcalls, 0, 226 "New buffer header acquisition requests"); 227 SYSCTL_INT(_vfs, OID_AUTO, recoverbufcalls, CTLFLAG_RD, &recoverbufcalls, 0, 228 "Recover VM space in an emergency"); 229 SYSCTL_INT(_vfs, OID_AUTO, debug_commit, CTLFLAG_RW, &debug_commit, 0, ""); 230 SYSCTL_INT(_vfs, OID_AUTO, debug_bufbio, CTLFLAG_RW, &debug_bufbio, 0, ""); 231 SYSCTL_INT(_debug_sizeof, OID_AUTO, buf, CTLFLAG_RD, 0, sizeof(struct buf), 232 "sizeof(struct buf)"); 233 234 char *buf_wmesg = BUF_WMESG; 235 236 #define VFS_BIO_NEED_ANY 0x01 /* any freeable buffer */ 237 #define VFS_BIO_NEED_UNUSED02 0x02 238 #define VFS_BIO_NEED_UNUSED04 0x04 239 #define VFS_BIO_NEED_BUFSPACE 0x08 /* wait for buf space, lo hysteresis */ 240 241 /* 242 * Called when buffer space is potentially available for recovery. 243 * getnewbuf() will block on this flag when it is unable to free 244 * sufficient buffer space. Buffer space becomes recoverable when 245 * bp's get placed back in the queues. 246 */ 247 static __inline void 248 bufspacewakeup(void) 249 { 250 /* 251 * If someone is waiting for BUF space, wake them up. Even 252 * though we haven't freed the kva space yet, the waiting 253 * process will be able to now. 254 */ 255 for (;;) { 256 int flags = needsbuffer; 257 cpu_ccfence(); 258 if ((flags & VFS_BIO_NEED_BUFSPACE) == 0) 259 break; 260 if (atomic_cmpset_int(&needsbuffer, flags, 261 flags & ~VFS_BIO_NEED_BUFSPACE)) { 262 wakeup(&needsbuffer); 263 break; 264 } 265 /* retry */ 266 } 267 } 268 269 /* 270 * runningbufwakeup: 271 * 272 * Accounting for I/O in progress. 273 * 274 */ 275 static __inline void 276 runningbufwakeup(struct buf *bp) 277 { 278 long totalspace; 279 long flags; 280 281 if ((totalspace = bp->b_runningbufspace) != 0) { 282 atomic_add_long(&runningbufspace, -totalspace); 283 atomic_add_long(&runningbufcount, -1); 284 bp->b_runningbufspace = 0; 285 286 /* 287 * see waitrunningbufspace() for limit test. 288 */ 289 for (;;) { 290 flags = runningbufreq; 291 cpu_ccfence(); 292 if (flags == 0) 293 break; 294 if (atomic_cmpset_int(&runningbufreq, flags, 0)) { 295 wakeup(&runningbufreq); 296 break; 297 } 298 /* retry */ 299 } 300 bd_signal(totalspace); 301 } 302 } 303 304 /* 305 * bufcountwakeup: 306 * 307 * Called when a buffer has been added to one of the free queues to 308 * account for the buffer and to wakeup anyone waiting for free buffers. 309 * This typically occurs when large amounts of metadata are being handled 310 * by the buffer cache ( else buffer space runs out first, usually ). 311 */ 312 static __inline void 313 bufcountwakeup(void) 314 { 315 long flags; 316 317 for (;;) { 318 flags = needsbuffer; 319 if (flags == 0) 320 break; 321 if (atomic_cmpset_int(&needsbuffer, flags, 322 (flags & ~VFS_BIO_NEED_ANY))) { 323 wakeup(&needsbuffer); 324 break; 325 } 326 /* retry */ 327 } 328 } 329 330 /* 331 * waitrunningbufspace() 332 * 333 * If runningbufspace exceeds 4/6 hirunningspace we block until 334 * runningbufspace drops to 3/6 hirunningspace. We also block if another 335 * thread blocked here in order to be fair, even if runningbufspace 336 * is now lower than the limit. 337 * 338 * The caller may be using this function to block in a tight loop, we 339 * must block while runningbufspace is greater than at least 340 * hirunningspace * 3 / 6. 341 */ 342 void 343 waitrunningbufspace(void) 344 { 345 long limit = hirunningspace * 4 / 6; 346 long flags; 347 348 while (runningbufspace > limit || runningbufreq) { 349 tsleep_interlock(&runningbufreq, 0); 350 flags = atomic_fetchadd_int(&runningbufreq, 1); 351 if (runningbufspace > limit || flags) 352 tsleep(&runningbufreq, PINTERLOCKED, "wdrn1", hz); 353 } 354 } 355 356 /* 357 * buf_dirty_count_severe: 358 * 359 * Return true if we have too many dirty buffers. 360 */ 361 int 362 buf_dirty_count_severe(void) 363 { 364 return (runningbufspace + dirtykvaspace >= hidirtybufspace || 365 dirtybufcount >= nbuf / 2); 366 } 367 368 /* 369 * Return true if the amount of running I/O is severe and BIOQ should 370 * start bursting. 371 */ 372 int 373 buf_runningbufspace_severe(void) 374 { 375 return (runningbufspace >= hirunningspace * 4 / 6); 376 } 377 378 /* 379 * vfs_buf_test_cache: 380 * 381 * Called when a buffer is extended. This function clears the B_CACHE 382 * bit if the newly extended portion of the buffer does not contain 383 * valid data. 384 * 385 * NOTE! Dirty VM pages are not processed into dirty (B_DELWRI) buffer 386 * cache buffers. The VM pages remain dirty, as someone had mmap()'d 387 * them while a clean buffer was present. 388 */ 389 static __inline__ 390 void 391 vfs_buf_test_cache(struct buf *bp, 392 vm_ooffset_t foff, vm_offset_t off, vm_offset_t size, 393 vm_page_t m) 394 { 395 if (bp->b_flags & B_CACHE) { 396 int base = (foff + off) & PAGE_MASK; 397 if (vm_page_is_valid(m, base, size) == 0) 398 bp->b_flags &= ~B_CACHE; 399 } 400 } 401 402 /* 403 * bd_speedup() 404 * 405 * Spank the buf_daemon[_hw] if the total dirty buffer space exceeds the 406 * low water mark. 407 */ 408 static __inline__ 409 void 410 bd_speedup(void) 411 { 412 if (dirtykvaspace < lodirtybufspace && dirtybufcount < nbuf / 2) 413 return; 414 415 if (bd_request == 0 && 416 (dirtykvaspace > lodirtybufspace / 2 || 417 dirtybufcount - dirtybufcounthw >= nbuf / 2)) { 418 if (atomic_fetchadd_int(&bd_request, 1) == 0) 419 wakeup(&bd_request); 420 } 421 if (bd_request_hw == 0 && 422 (dirtykvaspace > lodirtybufspace / 2 || 423 dirtybufcounthw >= nbuf / 2)) { 424 if (atomic_fetchadd_int(&bd_request_hw, 1) == 0) 425 wakeup(&bd_request_hw); 426 } 427 } 428 429 /* 430 * bd_heatup() 431 * 432 * Get the buf_daemon heated up when the number of running and dirty 433 * buffers exceeds the mid-point. 434 * 435 * Return the total number of dirty bytes past the second mid point 436 * as a measure of how much excess dirty data there is in the system. 437 */ 438 long 439 bd_heatup(void) 440 { 441 long mid1; 442 long mid2; 443 long totalspace; 444 445 mid1 = lodirtybufspace + (hidirtybufspace - lodirtybufspace) / 2; 446 447 totalspace = runningbufspace + dirtykvaspace; 448 if (totalspace >= mid1 || dirtybufcount >= nbuf / 2) { 449 bd_speedup(); 450 mid2 = mid1 + (hidirtybufspace - mid1) / 2; 451 if (totalspace >= mid2) 452 return(totalspace - mid2); 453 } 454 return(0); 455 } 456 457 /* 458 * bd_wait() 459 * 460 * Wait for the buffer cache to flush (totalspace) bytes worth of 461 * buffers, then return. 462 * 463 * Regardless this function blocks while the number of dirty buffers 464 * exceeds hidirtybufspace. 465 */ 466 void 467 bd_wait(long totalspace) 468 { 469 u_int i; 470 u_int j; 471 u_int mi; 472 int count; 473 474 if (curthread == bufdaemonhw_td || curthread == bufdaemon_td) 475 return; 476 477 while (totalspace > 0) { 478 bd_heatup(); 479 480 /* 481 * Order is important. Suppliers adjust bd_wake_index after 482 * updating runningbufspace/dirtykvaspace. We want to fetch 483 * bd_wake_index before accessing. Any error should thus 484 * be in our favor. 485 */ 486 i = atomic_fetchadd_int(&bd_wake_index, 0); 487 if (totalspace > runningbufspace + dirtykvaspace) 488 totalspace = runningbufspace + dirtykvaspace; 489 count = totalspace / MAXBSIZE; 490 if (count >= BD_WAKE_SIZE / 2) 491 count = BD_WAKE_SIZE / 2; 492 i = i + count; 493 mi = i & BD_WAKE_MASK; 494 495 /* 496 * This is not a strict interlock, so we play a bit loose 497 * with locking access to dirtybufspace*. We have to re-check 498 * bd_wake_index to ensure that it hasn't passed us. 499 */ 500 tsleep_interlock(&bd_wake_ary[mi], 0); 501 atomic_add_int(&bd_wake_ary[mi], 1); 502 j = atomic_fetchadd_int(&bd_wake_index, 0); 503 if ((int)(i - j) >= 0) 504 tsleep(&bd_wake_ary[mi], PINTERLOCKED, "flstik", hz); 505 506 totalspace = runningbufspace + dirtykvaspace - hidirtybufspace; 507 } 508 } 509 510 /* 511 * bd_signal() 512 * 513 * This function is called whenever runningbufspace or dirtykvaspace 514 * is reduced. Track threads waiting for run+dirty buffer I/O 515 * complete. 516 */ 517 static void 518 bd_signal(long totalspace) 519 { 520 u_int i; 521 522 if (totalspace > 0) { 523 if (totalspace > MAXBSIZE * BD_WAKE_SIZE) 524 totalspace = MAXBSIZE * BD_WAKE_SIZE; 525 while (totalspace > 0) { 526 i = atomic_fetchadd_int(&bd_wake_index, 1); 527 i &= BD_WAKE_MASK; 528 if (atomic_readandclear_int(&bd_wake_ary[i])) 529 wakeup(&bd_wake_ary[i]); 530 totalspace -= MAXBSIZE; 531 } 532 } 533 } 534 535 /* 536 * BIO tracking support routines. 537 * 538 * Release a ref on a bio_track. Wakeup requests are atomically released 539 * along with the last reference so bk_active will never wind up set to 540 * only 0x80000000. 541 */ 542 static 543 void 544 bio_track_rel(struct bio_track *track) 545 { 546 int active; 547 int desired; 548 549 /* 550 * Shortcut 551 */ 552 active = track->bk_active; 553 if (active == 1 && atomic_cmpset_int(&track->bk_active, 1, 0)) 554 return; 555 556 /* 557 * Full-on. Note that the wait flag is only atomically released on 558 * the 1->0 count transition. 559 * 560 * We check for a negative count transition using bit 30 since bit 31 561 * has a different meaning. 562 */ 563 for (;;) { 564 desired = (active & 0x7FFFFFFF) - 1; 565 if (desired) 566 desired |= active & 0x80000000; 567 if (atomic_cmpset_int(&track->bk_active, active, desired)) { 568 if (desired & 0x40000000) 569 panic("bio_track_rel: bad count: %p", track); 570 if (active & 0x80000000) 571 wakeup(track); 572 break; 573 } 574 active = track->bk_active; 575 } 576 } 577 578 /* 579 * Wait for the tracking count to reach 0. 580 * 581 * Use atomic ops such that the wait flag is only set atomically when 582 * bk_active is non-zero. 583 */ 584 int 585 bio_track_wait(struct bio_track *track, int slp_flags, int slp_timo) 586 { 587 int active; 588 int desired; 589 int error; 590 591 /* 592 * Shortcut 593 */ 594 if (track->bk_active == 0) 595 return(0); 596 597 /* 598 * Full-on. Note that the wait flag may only be atomically set if 599 * the active count is non-zero. 600 * 601 * NOTE: We cannot optimize active == desired since a wakeup could 602 * clear active prior to our tsleep_interlock(). 603 */ 604 error = 0; 605 while ((active = track->bk_active) != 0) { 606 cpu_ccfence(); 607 desired = active | 0x80000000; 608 tsleep_interlock(track, slp_flags); 609 if (atomic_cmpset_int(&track->bk_active, active, desired)) { 610 error = tsleep(track, slp_flags | PINTERLOCKED, 611 "trwait", slp_timo); 612 if (error) 613 break; 614 } 615 } 616 return (error); 617 } 618 619 /* 620 * bufinit: 621 * 622 * Load time initialisation of the buffer cache, called from machine 623 * dependant initialization code. 624 */ 625 static 626 void 627 bufinit(void *dummy __unused) 628 { 629 struct bufpcpu *pcpu; 630 struct buf *bp; 631 vm_offset_t bogus_offset; 632 int i; 633 int j; 634 long n; 635 636 /* next, make a null set of free lists */ 637 for (i = 0; i < ncpus; ++i) { 638 pcpu = &bufpcpu[i]; 639 spin_init(&pcpu->spin, "bufinit"); 640 for (j = 0; j < BUFFER_QUEUES; j++) 641 TAILQ_INIT(&pcpu->bufqueues[j]); 642 } 643 644 /* 645 * Finally, initialize each buffer header and stick on empty q. 646 * Each buffer gets its own KVA reservation. 647 */ 648 i = 0; 649 pcpu = &bufpcpu[i]; 650 651 for (n = 0; n < nbuf; n++) { 652 bp = &buf[n]; 653 bzero(bp, sizeof *bp); 654 bp->b_flags = B_INVAL; /* we're just an empty header */ 655 bp->b_cmd = BUF_CMD_DONE; 656 bp->b_qindex = BQUEUE_EMPTY; 657 bp->b_qcpu = i; 658 bp->b_kvabase = (void *)(vm_map_min(&buffer_map) + 659 MAXBSIZE * n); 660 bp->b_kvasize = MAXBSIZE; 661 initbufbio(bp); 662 xio_init(&bp->b_xio); 663 buf_dep_init(bp); 664 TAILQ_INSERT_TAIL(&pcpu->bufqueues[bp->b_qindex], 665 bp, b_freelist); 666 667 i = (i + 1) % ncpus; 668 pcpu = &bufpcpu[i]; 669 } 670 671 /* 672 * maxbufspace is the absolute maximum amount of buffer space we are 673 * allowed to reserve in KVM and in real terms. The absolute maximum 674 * is nominally used by buf_daemon. hibufspace is the nominal maximum 675 * used by most other processes. The differential is required to 676 * ensure that buf_daemon is able to run when other processes might 677 * be blocked waiting for buffer space. 678 * 679 * Calculate hysteresis (lobufspace, hibufspace). Don't make it 680 * too large or we might lockup a cpu for too long a period of 681 * time in our tight loop. 682 */ 683 maxbufspace = nbuf * NBUFCALCSIZE; 684 hibufspace = lmax(3 * maxbufspace / 4, maxbufspace - MAXBSIZE * 10); 685 lobufspace = hibufspace * 7 / 8; 686 if (hibufspace - lobufspace > 64 * 1024 * 1024) 687 lobufspace = hibufspace - 64 * 1024 * 1024; 688 if (lobufspace > hibufspace - MAXBSIZE) 689 lobufspace = hibufspace - MAXBSIZE; 690 691 lorunningspace = 512 * 1024; 692 /* hirunningspace -- see below */ 693 694 /* 695 * Limit the amount of malloc memory since it is wired permanently 696 * into the kernel space. Even though this is accounted for in 697 * the buffer allocation, we don't want the malloced region to grow 698 * uncontrolled. The malloc scheme improves memory utilization 699 * significantly on average (small) directories. 700 */ 701 maxbufmallocspace = hibufspace / 20; 702 703 /* 704 * Reduce the chance of a deadlock occuring by limiting the number 705 * of delayed-write dirty buffers we allow to stack up. 706 * 707 * We don't want too much actually queued to the device at once 708 * (XXX this needs to be per-mount!), because the buffers will 709 * wind up locked for a very long period of time while the I/O 710 * drains. 711 */ 712 hidirtybufspace = hibufspace / 2; /* dirty + running */ 713 hirunningspace = hibufspace / 16; /* locked & queued to device */ 714 if (hirunningspace < 1024 * 1024) 715 hirunningspace = 1024 * 1024; 716 717 dirtykvaspace = 0; 718 dirtybufspace = 0; 719 dirtybufspacehw = 0; 720 721 lodirtybufspace = hidirtybufspace / 2; 722 723 /* 724 * Maximum number of async ops initiated per buf_daemon loop. This is 725 * somewhat of a hack at the moment, we really need to limit ourselves 726 * based on the number of bytes of I/O in-transit that were initiated 727 * from buf_daemon. 728 */ 729 730 bogus_offset = kmem_alloc_pageable(&kernel_map, PAGE_SIZE, 731 VM_SUBSYS_BOGUS); 732 vm_object_hold(&kernel_object); 733 bogus_page = vm_page_alloc(&kernel_object, 734 (bogus_offset >> PAGE_SHIFT), 735 VM_ALLOC_NORMAL); 736 vm_object_drop(&kernel_object); 737 vmstats.v_wire_count++; 738 739 } 740 741 SYSINIT(do_bufinit, SI_BOOT2_MACHDEP, SI_ORDER_FIRST, bufinit, NULL); 742 743 /* 744 * Initialize the embedded bio structures, typically used by 745 * deprecated code which tries to allocate its own struct bufs. 746 */ 747 void 748 initbufbio(struct buf *bp) 749 { 750 bp->b_bio1.bio_buf = bp; 751 bp->b_bio1.bio_prev = NULL; 752 bp->b_bio1.bio_offset = NOOFFSET; 753 bp->b_bio1.bio_next = &bp->b_bio2; 754 bp->b_bio1.bio_done = NULL; 755 bp->b_bio1.bio_flags = 0; 756 757 bp->b_bio2.bio_buf = bp; 758 bp->b_bio2.bio_prev = &bp->b_bio1; 759 bp->b_bio2.bio_offset = NOOFFSET; 760 bp->b_bio2.bio_next = NULL; 761 bp->b_bio2.bio_done = NULL; 762 bp->b_bio2.bio_flags = 0; 763 764 BUF_LOCKINIT(bp); 765 } 766 767 /* 768 * Reinitialize the embedded bio structures as well as any additional 769 * translation cache layers. 770 */ 771 void 772 reinitbufbio(struct buf *bp) 773 { 774 struct bio *bio; 775 776 for (bio = &bp->b_bio1; bio; bio = bio->bio_next) { 777 bio->bio_done = NULL; 778 bio->bio_offset = NOOFFSET; 779 } 780 } 781 782 /* 783 * Undo the effects of an initbufbio(). 784 */ 785 void 786 uninitbufbio(struct buf *bp) 787 { 788 dsched_buf_exit(bp); 789 BUF_LOCKFREE(bp); 790 } 791 792 /* 793 * Push another BIO layer onto an existing BIO and return it. The new 794 * BIO layer may already exist, holding cached translation data. 795 */ 796 struct bio * 797 push_bio(struct bio *bio) 798 { 799 struct bio *nbio; 800 801 if ((nbio = bio->bio_next) == NULL) { 802 int index = bio - &bio->bio_buf->b_bio_array[0]; 803 if (index >= NBUF_BIO - 1) { 804 panic("push_bio: too many layers %d for bp %p", 805 index, bio->bio_buf); 806 } 807 nbio = &bio->bio_buf->b_bio_array[index + 1]; 808 bio->bio_next = nbio; 809 nbio->bio_prev = bio; 810 nbio->bio_buf = bio->bio_buf; 811 nbio->bio_offset = NOOFFSET; 812 nbio->bio_done = NULL; 813 nbio->bio_next = NULL; 814 } 815 KKASSERT(nbio->bio_done == NULL); 816 return(nbio); 817 } 818 819 /* 820 * Pop a BIO translation layer, returning the previous layer. The 821 * must have been previously pushed. 822 */ 823 struct bio * 824 pop_bio(struct bio *bio) 825 { 826 return(bio->bio_prev); 827 } 828 829 void 830 clearbiocache(struct bio *bio) 831 { 832 while (bio) { 833 bio->bio_offset = NOOFFSET; 834 bio = bio->bio_next; 835 } 836 } 837 838 /* 839 * Remove the buffer from the appropriate free list. 840 * (caller must be locked) 841 */ 842 static __inline void 843 _bremfree(struct buf *bp) 844 { 845 struct bufpcpu *pcpu = &bufpcpu[bp->b_qcpu]; 846 847 if (bp->b_qindex != BQUEUE_NONE) { 848 KASSERT(BUF_REFCNTNB(bp) == 1, 849 ("bremfree: bp %p not locked",bp)); 850 TAILQ_REMOVE(&pcpu->bufqueues[bp->b_qindex], bp, b_freelist); 851 bp->b_qindex = BQUEUE_NONE; 852 } else { 853 if (BUF_REFCNTNB(bp) <= 1) 854 panic("bremfree: removing a buffer not on a queue"); 855 } 856 } 857 858 /* 859 * bremfree() - must be called with a locked buffer 860 */ 861 void 862 bremfree(struct buf *bp) 863 { 864 struct bufpcpu *pcpu = &bufpcpu[bp->b_qcpu]; 865 866 spin_lock(&pcpu->spin); 867 _bremfree(bp); 868 spin_unlock(&pcpu->spin); 869 } 870 871 /* 872 * bremfree_locked - must be called with pcpu->spin locked 873 */ 874 static void 875 bremfree_locked(struct buf *bp) 876 { 877 _bremfree(bp); 878 } 879 880 /* 881 * This version of bread issues any required I/O asyncnronously and 882 * makes a callback on completion. 883 * 884 * The callback must check whether BIO_DONE is set in the bio and issue 885 * the bpdone(bp, 0) if it isn't. The callback is responsible for clearing 886 * BIO_DONE and disposing of the I/O (bqrelse()ing it). 887 */ 888 void 889 breadcb(struct vnode *vp, off_t loffset, int size, 890 void (*func)(struct bio *), void *arg) 891 { 892 struct buf *bp; 893 894 bp = getblk(vp, loffset, size, 0, 0); 895 896 /* if not found in cache, do some I/O */ 897 if ((bp->b_flags & B_CACHE) == 0) { 898 bp->b_flags &= ~(B_ERROR | B_EINTR | B_INVAL); 899 bp->b_cmd = BUF_CMD_READ; 900 bp->b_bio1.bio_done = func; 901 bp->b_bio1.bio_caller_info1.ptr = arg; 902 vfs_busy_pages(vp, bp); 903 BUF_KERNPROC(bp); 904 vn_strategy(vp, &bp->b_bio1); 905 } else if (func) { 906 /* 907 * Since we are issuing the callback synchronously it cannot 908 * race the BIO_DONE, so no need for atomic ops here. 909 */ 910 /*bp->b_bio1.bio_done = func;*/ 911 bp->b_bio1.bio_caller_info1.ptr = arg; 912 bp->b_bio1.bio_flags |= BIO_DONE; 913 func(&bp->b_bio1); 914 } else { 915 bqrelse(bp); 916 } 917 } 918 919 /* 920 * breadnx() - Terminal function for bread() and breadn(). 921 * 922 * This function will start asynchronous I/O on read-ahead blocks as well 923 * as satisfy the primary request. 924 * 925 * We must clear B_ERROR and B_INVAL prior to initiating I/O. If B_CACHE is 926 * set, the buffer is valid and we do not have to do anything. 927 */ 928 int 929 breadnx(struct vnode *vp, off_t loffset, int size, off_t *raoffset, 930 int *rabsize, int cnt, struct buf **bpp) 931 { 932 struct buf *bp, *rabp; 933 int i; 934 int rv = 0, readwait = 0; 935 936 if (*bpp) 937 bp = *bpp; 938 else 939 *bpp = bp = getblk(vp, loffset, size, 0, 0); 940 941 /* if not found in cache, do some I/O */ 942 if ((bp->b_flags & B_CACHE) == 0) { 943 bp->b_flags &= ~(B_ERROR | B_EINTR | B_INVAL); 944 bp->b_cmd = BUF_CMD_READ; 945 bp->b_bio1.bio_done = biodone_sync; 946 bp->b_bio1.bio_flags |= BIO_SYNC; 947 vfs_busy_pages(vp, bp); 948 vn_strategy(vp, &bp->b_bio1); 949 ++readwait; 950 } 951 952 for (i = 0; i < cnt; i++, raoffset++, rabsize++) { 953 if (inmem(vp, *raoffset)) 954 continue; 955 rabp = getblk(vp, *raoffset, *rabsize, 0, 0); 956 957 if ((rabp->b_flags & B_CACHE) == 0) { 958 rabp->b_flags &= ~(B_ERROR | B_EINTR | B_INVAL); 959 rabp->b_cmd = BUF_CMD_READ; 960 vfs_busy_pages(vp, rabp); 961 BUF_KERNPROC(rabp); 962 vn_strategy(vp, &rabp->b_bio1); 963 } else { 964 brelse(rabp); 965 } 966 } 967 if (readwait) 968 rv = biowait(&bp->b_bio1, "biord"); 969 return (rv); 970 } 971 972 /* 973 * bwrite: 974 * 975 * Synchronous write, waits for completion. 976 * 977 * Write, release buffer on completion. (Done by iodone 978 * if async). Do not bother writing anything if the buffer 979 * is invalid. 980 * 981 * Note that we set B_CACHE here, indicating that buffer is 982 * fully valid and thus cacheable. This is true even of NFS 983 * now so we set it generally. This could be set either here 984 * or in biodone() since the I/O is synchronous. We put it 985 * here. 986 */ 987 int 988 bwrite(struct buf *bp) 989 { 990 int error; 991 992 if (bp->b_flags & B_INVAL) { 993 brelse(bp); 994 return (0); 995 } 996 if (BUF_REFCNTNB(bp) == 0) 997 panic("bwrite: buffer is not busy???"); 998 999 /* 1000 * NOTE: We no longer mark the buffer clear prior to the vn_strategy() 1001 * call because it will remove the buffer from the vnode's 1002 * dirty buffer list prematurely and possibly cause filesystem 1003 * checks to race buffer flushes. This is now handled in 1004 * bpdone(). 1005 * 1006 * bundirty(bp); REMOVED 1007 */ 1008 1009 bp->b_flags &= ~(B_ERROR | B_EINTR); 1010 bp->b_flags |= B_CACHE; 1011 bp->b_cmd = BUF_CMD_WRITE; 1012 bp->b_bio1.bio_done = biodone_sync; 1013 bp->b_bio1.bio_flags |= BIO_SYNC; 1014 vfs_busy_pages(bp->b_vp, bp); 1015 1016 /* 1017 * Normal bwrites pipeline writes. NOTE: b_bufsize is only 1018 * valid for vnode-backed buffers. 1019 */ 1020 bsetrunningbufspace(bp, bp->b_bufsize); 1021 vn_strategy(bp->b_vp, &bp->b_bio1); 1022 error = biowait(&bp->b_bio1, "biows"); 1023 brelse(bp); 1024 1025 return (error); 1026 } 1027 1028 /* 1029 * bawrite: 1030 * 1031 * Asynchronous write. Start output on a buffer, but do not wait for 1032 * it to complete. The buffer is released when the output completes. 1033 * 1034 * bwrite() ( or the VOP routine anyway ) is responsible for handling 1035 * B_INVAL buffers. Not us. 1036 */ 1037 void 1038 bawrite(struct buf *bp) 1039 { 1040 if (bp->b_flags & B_INVAL) { 1041 brelse(bp); 1042 return; 1043 } 1044 if (BUF_REFCNTNB(bp) == 0) 1045 panic("bawrite: buffer is not busy???"); 1046 1047 /* 1048 * NOTE: We no longer mark the buffer clear prior to the vn_strategy() 1049 * call because it will remove the buffer from the vnode's 1050 * dirty buffer list prematurely and possibly cause filesystem 1051 * checks to race buffer flushes. This is now handled in 1052 * bpdone(). 1053 * 1054 * bundirty(bp); REMOVED 1055 */ 1056 bp->b_flags &= ~(B_ERROR | B_EINTR); 1057 bp->b_flags |= B_CACHE; 1058 bp->b_cmd = BUF_CMD_WRITE; 1059 KKASSERT(bp->b_bio1.bio_done == NULL); 1060 vfs_busy_pages(bp->b_vp, bp); 1061 1062 /* 1063 * Normal bwrites pipeline writes. NOTE: b_bufsize is only 1064 * valid for vnode-backed buffers. 1065 */ 1066 bsetrunningbufspace(bp, bp->b_bufsize); 1067 BUF_KERNPROC(bp); 1068 vn_strategy(bp->b_vp, &bp->b_bio1); 1069 } 1070 1071 /* 1072 * bowrite: 1073 * 1074 * Ordered write. Start output on a buffer, and flag it so that the 1075 * device will write it in the order it was queued. The buffer is 1076 * released when the output completes. bwrite() ( or the VOP routine 1077 * anyway ) is responsible for handling B_INVAL buffers. 1078 */ 1079 int 1080 bowrite(struct buf *bp) 1081 { 1082 bp->b_flags |= B_ORDERED; 1083 bawrite(bp); 1084 return (0); 1085 } 1086 1087 /* 1088 * bdwrite: 1089 * 1090 * Delayed write. (Buffer is marked dirty). Do not bother writing 1091 * anything if the buffer is marked invalid. 1092 * 1093 * Note that since the buffer must be completely valid, we can safely 1094 * set B_CACHE. In fact, we have to set B_CACHE here rather then in 1095 * biodone() in order to prevent getblk from writing the buffer 1096 * out synchronously. 1097 */ 1098 void 1099 bdwrite(struct buf *bp) 1100 { 1101 if (BUF_REFCNTNB(bp) == 0) 1102 panic("bdwrite: buffer is not busy"); 1103 1104 if (bp->b_flags & B_INVAL) { 1105 brelse(bp); 1106 return; 1107 } 1108 bdirty(bp); 1109 1110 dsched_buf_enter(bp); /* might stack */ 1111 1112 /* 1113 * Set B_CACHE, indicating that the buffer is fully valid. This is 1114 * true even of NFS now. 1115 */ 1116 bp->b_flags |= B_CACHE; 1117 1118 /* 1119 * This bmap keeps the system from needing to do the bmap later, 1120 * perhaps when the system is attempting to do a sync. Since it 1121 * is likely that the indirect block -- or whatever other datastructure 1122 * that the filesystem needs is still in memory now, it is a good 1123 * thing to do this. Note also, that if the pageout daemon is 1124 * requesting a sync -- there might not be enough memory to do 1125 * the bmap then... So, this is important to do. 1126 */ 1127 if (bp->b_bio2.bio_offset == NOOFFSET) { 1128 VOP_BMAP(bp->b_vp, bp->b_loffset, &bp->b_bio2.bio_offset, 1129 NULL, NULL, BUF_CMD_WRITE); 1130 } 1131 1132 /* 1133 * Because the underlying pages may still be mapped and 1134 * writable trying to set the dirty buffer (b_dirtyoff/end) 1135 * range here will be inaccurate. 1136 * 1137 * However, we must still clean the pages to satisfy the 1138 * vnode_pager and pageout daemon, so they think the pages 1139 * have been "cleaned". What has really occured is that 1140 * they've been earmarked for later writing by the buffer 1141 * cache. 1142 * 1143 * So we get the b_dirtyoff/end update but will not actually 1144 * depend on it (NFS that is) until the pages are busied for 1145 * writing later on. 1146 */ 1147 vfs_clean_pages(bp); 1148 bqrelse(bp); 1149 1150 /* 1151 * note: we cannot initiate I/O from a bdwrite even if we wanted to, 1152 * due to the softdep code. 1153 */ 1154 } 1155 1156 /* 1157 * Fake write - return pages to VM system as dirty, leave the buffer clean. 1158 * This is used by tmpfs. 1159 * 1160 * It is important for any VFS using this routine to NOT use it for 1161 * IO_SYNC or IO_ASYNC operations which occur when the system really 1162 * wants to flush VM pages to backing store. 1163 */ 1164 void 1165 buwrite(struct buf *bp) 1166 { 1167 vm_page_t m; 1168 int i; 1169 1170 /* 1171 * Only works for VMIO buffers. If the buffer is already 1172 * marked for delayed-write we can't avoid the bdwrite(). 1173 */ 1174 if ((bp->b_flags & B_VMIO) == 0 || (bp->b_flags & B_DELWRI)) { 1175 bdwrite(bp); 1176 return; 1177 } 1178 1179 /* 1180 * Mark as needing a commit. 1181 */ 1182 for (i = 0; i < bp->b_xio.xio_npages; i++) { 1183 m = bp->b_xio.xio_pages[i]; 1184 vm_page_need_commit(m); 1185 } 1186 bqrelse(bp); 1187 } 1188 1189 /* 1190 * bdirty: 1191 * 1192 * Turn buffer into delayed write request by marking it B_DELWRI. 1193 * B_RELBUF and B_NOCACHE must be cleared. 1194 * 1195 * We reassign the buffer to itself to properly update it in the 1196 * dirty/clean lists. 1197 * 1198 * Must be called from a critical section. 1199 * The buffer must be on BQUEUE_NONE. 1200 */ 1201 void 1202 bdirty(struct buf *bp) 1203 { 1204 KASSERT(bp->b_qindex == BQUEUE_NONE, 1205 ("bdirty: buffer %p still on queue %d", bp, bp->b_qindex)); 1206 if (bp->b_flags & B_NOCACHE) { 1207 kprintf("bdirty: clearing B_NOCACHE on buf %p\n", bp); 1208 bp->b_flags &= ~B_NOCACHE; 1209 } 1210 if (bp->b_flags & B_INVAL) { 1211 kprintf("bdirty: warning, dirtying invalid buffer %p\n", bp); 1212 } 1213 bp->b_flags &= ~B_RELBUF; 1214 1215 if ((bp->b_flags & B_DELWRI) == 0) { 1216 lwkt_gettoken(&bp->b_vp->v_token); 1217 bp->b_flags |= B_DELWRI; 1218 reassignbuf(bp); 1219 lwkt_reltoken(&bp->b_vp->v_token); 1220 1221 atomic_add_long(&dirtybufcount, 1); 1222 atomic_add_long(&dirtykvaspace, bp->b_kvasize); 1223 atomic_add_long(&dirtybufspace, bp->b_bufsize); 1224 if (bp->b_flags & B_HEAVY) { 1225 atomic_add_long(&dirtybufcounthw, 1); 1226 atomic_add_long(&dirtybufspacehw, bp->b_bufsize); 1227 } 1228 bd_heatup(); 1229 } 1230 } 1231 1232 /* 1233 * Set B_HEAVY, indicating that this is a heavy-weight buffer that 1234 * needs to be flushed with a different buf_daemon thread to avoid 1235 * deadlocks. B_HEAVY also imposes restrictions in getnewbuf(). 1236 */ 1237 void 1238 bheavy(struct buf *bp) 1239 { 1240 if ((bp->b_flags & B_HEAVY) == 0) { 1241 bp->b_flags |= B_HEAVY; 1242 if (bp->b_flags & B_DELWRI) { 1243 atomic_add_long(&dirtybufcounthw, 1); 1244 atomic_add_long(&dirtybufspacehw, bp->b_bufsize); 1245 } 1246 } 1247 } 1248 1249 /* 1250 * bundirty: 1251 * 1252 * Clear B_DELWRI for buffer. 1253 * 1254 * Must be called from a critical section. 1255 * 1256 * The buffer is typically on BQUEUE_NONE but there is one case in 1257 * brelse() that calls this function after placing the buffer on 1258 * a different queue. 1259 */ 1260 void 1261 bundirty(struct buf *bp) 1262 { 1263 if (bp->b_flags & B_DELWRI) { 1264 lwkt_gettoken(&bp->b_vp->v_token); 1265 bp->b_flags &= ~B_DELWRI; 1266 reassignbuf(bp); 1267 lwkt_reltoken(&bp->b_vp->v_token); 1268 1269 atomic_add_long(&dirtybufcount, -1); 1270 atomic_add_long(&dirtykvaspace, -bp->b_kvasize); 1271 atomic_add_long(&dirtybufspace, -bp->b_bufsize); 1272 if (bp->b_flags & B_HEAVY) { 1273 atomic_add_long(&dirtybufcounthw, -1); 1274 atomic_add_long(&dirtybufspacehw, -bp->b_bufsize); 1275 } 1276 bd_signal(bp->b_bufsize); 1277 } 1278 /* 1279 * Since it is now being written, we can clear its deferred write flag. 1280 */ 1281 bp->b_flags &= ~B_DEFERRED; 1282 } 1283 1284 /* 1285 * Set the b_runningbufspace field, used to track how much I/O is 1286 * in progress at any given moment. 1287 */ 1288 void 1289 bsetrunningbufspace(struct buf *bp, int bytes) 1290 { 1291 bp->b_runningbufspace = bytes; 1292 if (bytes) { 1293 atomic_add_long(&runningbufspace, bytes); 1294 atomic_add_long(&runningbufcount, 1); 1295 } 1296 } 1297 1298 /* 1299 * brelse: 1300 * 1301 * Release a busy buffer and, if requested, free its resources. The 1302 * buffer will be stashed in the appropriate bufqueue[] allowing it 1303 * to be accessed later as a cache entity or reused for other purposes. 1304 */ 1305 void 1306 brelse(struct buf *bp) 1307 { 1308 struct bufpcpu *pcpu; 1309 #ifdef INVARIANTS 1310 int saved_flags = bp->b_flags; 1311 #endif 1312 1313 KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)), 1314 ("brelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp)); 1315 1316 /* 1317 * If B_NOCACHE is set we are being asked to destroy the buffer and 1318 * its backing store. Clear B_DELWRI. 1319 * 1320 * B_NOCACHE is set in two cases: (1) when the caller really wants 1321 * to destroy the buffer and backing store and (2) when the caller 1322 * wants to destroy the buffer and backing store after a write 1323 * completes. 1324 */ 1325 if ((bp->b_flags & (B_NOCACHE|B_DELWRI)) == (B_NOCACHE|B_DELWRI)) { 1326 bundirty(bp); 1327 } 1328 1329 if ((bp->b_flags & (B_INVAL | B_DELWRI)) == B_DELWRI) { 1330 /* 1331 * A re-dirtied buffer is only subject to destruction 1332 * by B_INVAL. B_ERROR and B_NOCACHE are ignored. 1333 */ 1334 /* leave buffer intact */ 1335 } else if ((bp->b_flags & (B_NOCACHE | B_INVAL | B_ERROR)) || 1336 (bp->b_bufsize <= 0)) { 1337 /* 1338 * Either a failed read or we were asked to free or not 1339 * cache the buffer. This path is reached with B_DELWRI 1340 * set only if B_INVAL is already set. B_NOCACHE governs 1341 * backing store destruction. 1342 * 1343 * NOTE: HAMMER will set B_LOCKED in buf_deallocate if the 1344 * buffer cannot be immediately freed. 1345 */ 1346 bp->b_flags |= B_INVAL; 1347 if (LIST_FIRST(&bp->b_dep) != NULL) 1348 buf_deallocate(bp); 1349 if (bp->b_flags & B_DELWRI) { 1350 atomic_add_long(&dirtybufcount, -1); 1351 atomic_add_long(&dirtykvaspace, -bp->b_kvasize); 1352 atomic_add_long(&dirtybufspace, -bp->b_bufsize); 1353 if (bp->b_flags & B_HEAVY) { 1354 atomic_add_long(&dirtybufcounthw, -1); 1355 atomic_add_long(&dirtybufspacehw, 1356 -bp->b_bufsize); 1357 } 1358 bd_signal(bp->b_bufsize); 1359 } 1360 bp->b_flags &= ~(B_DELWRI | B_CACHE); 1361 } 1362 1363 /* 1364 * We must clear B_RELBUF if B_DELWRI or B_LOCKED is set, 1365 * or if b_refs is non-zero. 1366 * 1367 * If vfs_vmio_release() is called with either bit set, the 1368 * underlying pages may wind up getting freed causing a previous 1369 * write (bdwrite()) to get 'lost' because pages associated with 1370 * a B_DELWRI bp are marked clean. Pages associated with a 1371 * B_LOCKED buffer may be mapped by the filesystem. 1372 * 1373 * If we want to release the buffer ourselves (rather then the 1374 * originator asking us to release it), give the originator a 1375 * chance to countermand the release by setting B_LOCKED. 1376 * 1377 * We still allow the B_INVAL case to call vfs_vmio_release(), even 1378 * if B_DELWRI is set. 1379 * 1380 * If B_DELWRI is not set we may have to set B_RELBUF if we are low 1381 * on pages to return pages to the VM page queues. 1382 */ 1383 if ((bp->b_flags & (B_DELWRI | B_LOCKED)) || bp->b_refs) { 1384 bp->b_flags &= ~B_RELBUF; 1385 } else if (vm_page_count_min(0)) { 1386 if (LIST_FIRST(&bp->b_dep) != NULL) 1387 buf_deallocate(bp); /* can set B_LOCKED */ 1388 if (bp->b_flags & (B_DELWRI | B_LOCKED)) 1389 bp->b_flags &= ~B_RELBUF; 1390 else 1391 bp->b_flags |= B_RELBUF; 1392 } 1393 1394 /* 1395 * Make sure b_cmd is clear. It may have already been cleared by 1396 * biodone(). 1397 * 1398 * At this point destroying the buffer is governed by the B_INVAL 1399 * or B_RELBUF flags. 1400 */ 1401 bp->b_cmd = BUF_CMD_DONE; 1402 dsched_buf_exit(bp); 1403 1404 /* 1405 * VMIO buffer rundown. Make sure the VM page array is restored 1406 * after an I/O may have replaces some of the pages with bogus pages 1407 * in order to not destroy dirty pages in a fill-in read. 1408 * 1409 * Note that due to the code above, if a buffer is marked B_DELWRI 1410 * then the B_RELBUF and B_NOCACHE bits will always be clear. 1411 * B_INVAL may still be set, however. 1412 * 1413 * For clean buffers, B_INVAL or B_RELBUF will destroy the buffer 1414 * but not the backing store. B_NOCACHE will destroy the backing 1415 * store. 1416 * 1417 * Note that dirty NFS buffers contain byte-granular write ranges 1418 * and should not be destroyed w/ B_INVAL even if the backing store 1419 * is left intact. 1420 */ 1421 if (bp->b_flags & B_VMIO) { 1422 /* 1423 * Rundown for VMIO buffers which are not dirty NFS buffers. 1424 */ 1425 int i, j, resid; 1426 vm_page_t m; 1427 off_t foff; 1428 vm_pindex_t poff; 1429 vm_object_t obj; 1430 struct vnode *vp; 1431 1432 vp = bp->b_vp; 1433 1434 /* 1435 * Get the base offset and length of the buffer. Note that 1436 * in the VMIO case if the buffer block size is not 1437 * page-aligned then b_data pointer may not be page-aligned. 1438 * But our b_xio.xio_pages array *IS* page aligned. 1439 * 1440 * block sizes less then DEV_BSIZE (usually 512) are not 1441 * supported due to the page granularity bits (m->valid, 1442 * m->dirty, etc...). 1443 * 1444 * See man buf(9) for more information 1445 */ 1446 1447 resid = bp->b_bufsize; 1448 foff = bp->b_loffset; 1449 1450 for (i = 0; i < bp->b_xio.xio_npages; i++) { 1451 m = bp->b_xio.xio_pages[i]; 1452 1453 /* 1454 * If we hit a bogus page, fixup *all* of them 1455 * now. Note that we left these pages wired 1456 * when we removed them so they had better exist, 1457 * and they cannot be ripped out from under us so 1458 * no critical section protection is necessary. 1459 */ 1460 if (m == bogus_page) { 1461 obj = vp->v_object; 1462 poff = OFF_TO_IDX(bp->b_loffset); 1463 1464 vm_object_hold(obj); 1465 for (j = i; j < bp->b_xio.xio_npages; j++) { 1466 vm_page_t mtmp; 1467 1468 mtmp = bp->b_xio.xio_pages[j]; 1469 if (mtmp == bogus_page) { 1470 if ((bp->b_flags & B_HASBOGUS) == 0) 1471 panic("brelse: bp %p corrupt bogus", bp); 1472 mtmp = vm_page_lookup(obj, poff + j); 1473 if (!mtmp) 1474 panic("brelse: bp %p page %d missing", bp, j); 1475 bp->b_xio.xio_pages[j] = mtmp; 1476 } 1477 } 1478 vm_object_drop(obj); 1479 1480 if ((bp->b_flags & B_HASBOGUS) || (bp->b_flags & B_INVAL) == 0) { 1481 pmap_qenter(trunc_page((vm_offset_t)bp->b_data), 1482 bp->b_xio.xio_pages, bp->b_xio.xio_npages); 1483 bp->b_flags &= ~B_HASBOGUS; 1484 } 1485 m = bp->b_xio.xio_pages[i]; 1486 } 1487 1488 /* 1489 * Invalidate the backing store if B_NOCACHE is set 1490 * (e.g. used with vinvalbuf()). If this is NFS 1491 * we impose a requirement that the block size be 1492 * a multiple of PAGE_SIZE and create a temporary 1493 * hack to basically invalidate the whole page. The 1494 * problem is that NFS uses really odd buffer sizes 1495 * especially when tracking piecemeal writes and 1496 * it also vinvalbuf()'s a lot, which would result 1497 * in only partial page validation and invalidation 1498 * here. If the file page is mmap()'d, however, 1499 * all the valid bits get set so after we invalidate 1500 * here we would end up with weird m->valid values 1501 * like 0xfc. nfs_getpages() can't handle this so 1502 * we clear all the valid bits for the NFS case 1503 * instead of just some of them. 1504 * 1505 * The real bug is the VM system having to set m->valid 1506 * to VM_PAGE_BITS_ALL for faulted-in pages, which 1507 * itself is an artifact of the whole 512-byte 1508 * granular mess that exists to support odd block 1509 * sizes and UFS meta-data block sizes (e.g. 6144). 1510 * A complete rewrite is required. 1511 * 1512 * XXX 1513 */ 1514 if (bp->b_flags & (B_NOCACHE|B_ERROR)) { 1515 int poffset = foff & PAGE_MASK; 1516 int presid; 1517 1518 presid = PAGE_SIZE - poffset; 1519 if (bp->b_vp->v_tag == VT_NFS && 1520 bp->b_vp->v_type == VREG) { 1521 ; /* entire page */ 1522 } else if (presid > resid) { 1523 presid = resid; 1524 } 1525 KASSERT(presid >= 0, ("brelse: extra page")); 1526 vm_page_set_invalid(m, poffset, presid); 1527 1528 /* 1529 * Also make sure any swap cache is removed 1530 * as it is now stale (HAMMER in particular 1531 * uses B_NOCACHE to deal with buffer 1532 * aliasing). 1533 */ 1534 swap_pager_unswapped(m); 1535 } 1536 resid -= PAGE_SIZE - (foff & PAGE_MASK); 1537 foff = (foff + PAGE_SIZE) & ~(off_t)PAGE_MASK; 1538 } 1539 if (bp->b_flags & (B_INVAL | B_RELBUF)) 1540 vfs_vmio_release(bp); 1541 } else { 1542 /* 1543 * Rundown for non-VMIO buffers. 1544 */ 1545 if (bp->b_flags & (B_INVAL | B_RELBUF)) { 1546 if (bp->b_bufsize) 1547 allocbuf(bp, 0); 1548 KKASSERT (LIST_FIRST(&bp->b_dep) == NULL); 1549 if (bp->b_vp) 1550 brelvp(bp); 1551 } 1552 } 1553 1554 if (bp->b_qindex != BQUEUE_NONE) 1555 panic("brelse: free buffer onto another queue???"); 1556 if (BUF_REFCNTNB(bp) > 1) { 1557 /* Temporary panic to verify exclusive locking */ 1558 /* This panic goes away when we allow shared refs */ 1559 panic("brelse: multiple refs"); 1560 /* NOT REACHED */ 1561 return; 1562 } 1563 1564 /* 1565 * Figure out the correct queue to place the cleaned up buffer on. 1566 * Buffers placed in the EMPTY or EMPTYKVA had better already be 1567 * disassociated from their vnode. 1568 * 1569 * Return the buffer to its original pcpu area 1570 */ 1571 pcpu = &bufpcpu[bp->b_qcpu]; 1572 spin_lock(&pcpu->spin); 1573 1574 if (bp->b_flags & B_LOCKED) { 1575 /* 1576 * Buffers that are locked are placed in the locked queue 1577 * immediately, regardless of their state. 1578 */ 1579 bp->b_qindex = BQUEUE_LOCKED; 1580 TAILQ_INSERT_TAIL(&pcpu->bufqueues[bp->b_qindex], 1581 bp, b_freelist); 1582 } else if (bp->b_bufsize == 0) { 1583 /* 1584 * Buffers with no memory. Due to conditionals near the top 1585 * of brelse() such buffers should probably already be 1586 * marked B_INVAL and disassociated from their vnode. 1587 */ 1588 bp->b_flags |= B_INVAL; 1589 KASSERT(bp->b_vp == NULL, 1590 ("bp1 %p flags %08x/%08x vnode %p " 1591 "unexpectededly still associated!", 1592 bp, saved_flags, bp->b_flags, bp->b_vp)); 1593 KKASSERT((bp->b_flags & B_HASHED) == 0); 1594 bp->b_qindex = BQUEUE_EMPTY; 1595 TAILQ_INSERT_HEAD(&pcpu->bufqueues[bp->b_qindex], 1596 bp, b_freelist); 1597 } else if (bp->b_flags & (B_INVAL | B_NOCACHE | B_RELBUF)) { 1598 /* 1599 * Buffers with junk contents. Again these buffers had better 1600 * already be disassociated from their vnode. 1601 */ 1602 KASSERT(bp->b_vp == NULL, 1603 ("bp2 %p flags %08x/%08x vnode %p unexpectededly " 1604 "still associated!", 1605 bp, saved_flags, bp->b_flags, bp->b_vp)); 1606 KKASSERT((bp->b_flags & B_HASHED) == 0); 1607 bp->b_flags |= B_INVAL; 1608 bp->b_qindex = BQUEUE_CLEAN; 1609 TAILQ_INSERT_HEAD(&pcpu->bufqueues[bp->b_qindex], 1610 bp, b_freelist); 1611 } else { 1612 /* 1613 * Remaining buffers. These buffers are still associated with 1614 * their vnode. 1615 */ 1616 switch(bp->b_flags & (B_DELWRI|B_HEAVY)) { 1617 case B_DELWRI: 1618 bp->b_qindex = BQUEUE_DIRTY; 1619 TAILQ_INSERT_TAIL(&pcpu->bufqueues[bp->b_qindex], 1620 bp, b_freelist); 1621 break; 1622 case B_DELWRI | B_HEAVY: 1623 bp->b_qindex = BQUEUE_DIRTY_HW; 1624 TAILQ_INSERT_TAIL(&pcpu->bufqueues[bp->b_qindex], 1625 bp, b_freelist); 1626 break; 1627 default: 1628 /* 1629 * NOTE: Buffers are always placed at the end of the 1630 * queue. If B_AGE is not set the buffer will cycle 1631 * through the queue twice. 1632 */ 1633 bp->b_qindex = BQUEUE_CLEAN; 1634 TAILQ_INSERT_TAIL(&pcpu->bufqueues[bp->b_qindex], 1635 bp, b_freelist); 1636 break; 1637 } 1638 } 1639 spin_unlock(&pcpu->spin); 1640 1641 /* 1642 * If B_INVAL, clear B_DELWRI. We've already placed the buffer 1643 * on the correct queue but we have not yet unlocked it. 1644 */ 1645 if ((bp->b_flags & (B_INVAL|B_DELWRI)) == (B_INVAL|B_DELWRI)) 1646 bundirty(bp); 1647 1648 /* 1649 * The bp is on an appropriate queue unless locked. If it is not 1650 * locked or dirty we can wakeup threads waiting for buffer space. 1651 * 1652 * We've already handled the B_INVAL case ( B_DELWRI will be clear 1653 * if B_INVAL is set ). 1654 */ 1655 if ((bp->b_flags & (B_LOCKED|B_DELWRI)) == 0) 1656 bufcountwakeup(); 1657 1658 /* 1659 * Something we can maybe free or reuse 1660 */ 1661 if (bp->b_bufsize || bp->b_kvasize) 1662 bufspacewakeup(); 1663 1664 /* 1665 * Clean up temporary flags and unlock the buffer. 1666 */ 1667 bp->b_flags &= ~(B_ORDERED | B_NOCACHE | B_RELBUF | B_DIRECT); 1668 BUF_UNLOCK(bp); 1669 } 1670 1671 /* 1672 * bqrelse: 1673 * 1674 * Release a buffer back to the appropriate queue but do not try to free 1675 * it. The buffer is expected to be used again soon. 1676 * 1677 * bqrelse() is used by bdwrite() to requeue a delayed write, and used by 1678 * biodone() to requeue an async I/O on completion. It is also used when 1679 * known good buffers need to be requeued but we think we may need the data 1680 * again soon. 1681 * 1682 * XXX we should be able to leave the B_RELBUF hint set on completion. 1683 */ 1684 void 1685 bqrelse(struct buf *bp) 1686 { 1687 struct bufpcpu *pcpu; 1688 1689 KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)), 1690 ("bqrelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp)); 1691 1692 if (bp->b_qindex != BQUEUE_NONE) 1693 panic("bqrelse: free buffer onto another queue???"); 1694 if (BUF_REFCNTNB(bp) > 1) { 1695 /* do not release to free list */ 1696 panic("bqrelse: multiple refs"); 1697 return; 1698 } 1699 1700 buf_act_advance(bp); 1701 1702 pcpu = &bufpcpu[bp->b_qcpu]; 1703 spin_lock(&pcpu->spin); 1704 1705 if (bp->b_flags & B_LOCKED) { 1706 /* 1707 * Locked buffers are released to the locked queue. However, 1708 * if the buffer is dirty it will first go into the dirty 1709 * queue and later on after the I/O completes successfully it 1710 * will be released to the locked queue. 1711 */ 1712 bp->b_qindex = BQUEUE_LOCKED; 1713 TAILQ_INSERT_TAIL(&pcpu->bufqueues[bp->b_qindex], 1714 bp, b_freelist); 1715 } else if (bp->b_flags & B_DELWRI) { 1716 bp->b_qindex = (bp->b_flags & B_HEAVY) ? 1717 BQUEUE_DIRTY_HW : BQUEUE_DIRTY; 1718 TAILQ_INSERT_TAIL(&pcpu->bufqueues[bp->b_qindex], 1719 bp, b_freelist); 1720 } else if (vm_page_count_min(0)) { 1721 /* 1722 * We are too low on memory, we have to try to free the 1723 * buffer (most importantly: the wired pages making up its 1724 * backing store) *now*. 1725 */ 1726 spin_unlock(&pcpu->spin); 1727 brelse(bp); 1728 return; 1729 } else { 1730 bp->b_qindex = BQUEUE_CLEAN; 1731 TAILQ_INSERT_TAIL(&pcpu->bufqueues[bp->b_qindex], 1732 bp, b_freelist); 1733 } 1734 spin_unlock(&pcpu->spin); 1735 1736 /* 1737 * We have now placed the buffer on the proper queue, but have yet 1738 * to unlock it. 1739 */ 1740 if ((bp->b_flags & B_LOCKED) == 0 && 1741 ((bp->b_flags & B_INVAL) || (bp->b_flags & B_DELWRI) == 0)) { 1742 bufcountwakeup(); 1743 } 1744 1745 /* 1746 * Something we can maybe free or reuse. 1747 */ 1748 if (bp->b_bufsize && !(bp->b_flags & B_DELWRI)) 1749 bufspacewakeup(); 1750 1751 /* 1752 * Final cleanup and unlock. Clear bits that are only used while a 1753 * buffer is actively locked. 1754 */ 1755 bp->b_flags &= ~(B_ORDERED | B_NOCACHE | B_RELBUF); 1756 dsched_buf_exit(bp); 1757 BUF_UNLOCK(bp); 1758 } 1759 1760 /* 1761 * Hold a buffer, preventing it from being reused. This will prevent 1762 * normal B_RELBUF operations on the buffer but will not prevent B_INVAL 1763 * operations. If a B_INVAL operation occurs the buffer will remain held 1764 * but the underlying pages may get ripped out. 1765 * 1766 * These functions are typically used in VOP_READ/VOP_WRITE functions 1767 * to hold a buffer during a copyin or copyout, preventing deadlocks 1768 * or recursive lock panics when read()/write() is used over mmap()'d 1769 * space. 1770 * 1771 * NOTE: bqhold() requires that the buffer be locked at the time of the 1772 * hold. bqdrop() has no requirements other than the buffer having 1773 * previously been held. 1774 */ 1775 void 1776 bqhold(struct buf *bp) 1777 { 1778 atomic_add_int(&bp->b_refs, 1); 1779 } 1780 1781 void 1782 bqdrop(struct buf *bp) 1783 { 1784 KKASSERT(bp->b_refs > 0); 1785 atomic_add_int(&bp->b_refs, -1); 1786 } 1787 1788 /* 1789 * Return backing pages held by the buffer 'bp' back to the VM system. 1790 * This routine is called when the bp is invalidated, released, or 1791 * reused. 1792 * 1793 * The KVA mapping (b_data) for the underlying pages is removed by 1794 * this function. 1795 * 1796 * WARNING! This routine is integral to the low memory critical path 1797 * when a buffer is B_RELBUF'd. If the system has a severe page 1798 * deficit we need to get the page(s) onto the PQ_FREE or PQ_CACHE 1799 * queues so they can be reused in the current pageout daemon 1800 * pass. 1801 */ 1802 static void 1803 vfs_vmio_release(struct buf *bp) 1804 { 1805 int i; 1806 vm_page_t m; 1807 1808 for (i = 0; i < bp->b_xio.xio_npages; i++) { 1809 m = bp->b_xio.xio_pages[i]; 1810 bp->b_xio.xio_pages[i] = NULL; 1811 1812 /* 1813 * We need to own the page in order to safely unwire it. 1814 */ 1815 vm_page_busy_wait(m, FALSE, "vmiopg"); 1816 1817 /* 1818 * The VFS is telling us this is not a meta-data buffer 1819 * even if it is backed by a block device. 1820 */ 1821 if (bp->b_flags & B_NOTMETA) 1822 vm_page_flag_set(m, PG_NOTMETA); 1823 1824 /* 1825 * This is a very important bit of code. We try to track 1826 * VM page use whether the pages are wired into the buffer 1827 * cache or not. While wired into the buffer cache the 1828 * bp tracks the act_count. 1829 * 1830 * We can choose to place unwired pages on the inactive 1831 * queue (0) or active queue (1). If we place too many 1832 * on the active queue the queue will cycle the act_count 1833 * on pages we'd like to keep, just from single-use pages 1834 * (such as when doing a tar-up or file scan). 1835 */ 1836 if (bp->b_act_count < vm_cycle_point) 1837 vm_page_unwire(m, 0); 1838 else 1839 vm_page_unwire(m, 1); 1840 1841 /* 1842 * If the wire_count has dropped to 0 we may need to take 1843 * further action before unbusying the page. 1844 * 1845 * WARNING: vm_page_try_*() also checks PG_NEED_COMMIT for us. 1846 */ 1847 if (m->wire_count == 0) { 1848 if (bp->b_flags & B_DIRECT) { 1849 /* 1850 * Attempt to free the page if B_DIRECT is 1851 * set, the caller does not desire the page 1852 * to be cached. 1853 */ 1854 vm_page_wakeup(m); 1855 vm_page_try_to_free(m); 1856 } else if ((bp->b_flags & B_NOTMETA) || 1857 vm_page_count_min(0)) { 1858 /* 1859 * Attempt to move the page to PQ_CACHE 1860 * if B_NOTMETA is set. This flag is set 1861 * by HAMMER to remove one of the two pages 1862 * present when double buffering is enabled. 1863 * 1864 * Attempt to move the page to PQ_CACHE 1865 * If we have a severe page deficit. This 1866 * will cause buffer cache operations related 1867 * to pageouts to recycle the related pages 1868 * in order to avoid a low memory deadlock. 1869 */ 1870 m->act_count = bp->b_act_count; 1871 vm_page_wakeup(m); 1872 vm_page_try_to_cache(m); 1873 } else { 1874 /* 1875 * Nominal case, leave the page on the 1876 * queue the original unwiring placed it on 1877 * (active or inactive). 1878 */ 1879 m->act_count = bp->b_act_count; 1880 vm_page_wakeup(m); 1881 } 1882 } else { 1883 vm_page_wakeup(m); 1884 } 1885 } 1886 1887 /* 1888 * Zero out the pmap pte's for the mapping, but don't bother 1889 * invalidating the TLB. The range will be properly invalidating 1890 * when new pages are entered into the mapping. 1891 * 1892 * This in particular reduces tmpfs tear-down overhead and reduces 1893 * buffer cache re-use overhead (one invalidation sequence instead 1894 * of two per re-use). 1895 */ 1896 pmap_qremove_noinval(trunc_page((vm_offset_t) bp->b_data), 1897 bp->b_xio.xio_npages); 1898 if (bp->b_bufsize) { 1899 atomic_add_long(&bufspace, -bp->b_bufsize); 1900 bp->b_bufsize = 0; 1901 bufspacewakeup(); 1902 } 1903 bp->b_xio.xio_npages = 0; 1904 bp->b_flags &= ~B_VMIO; 1905 KKASSERT (LIST_FIRST(&bp->b_dep) == NULL); 1906 if (bp->b_vp) 1907 brelvp(bp); 1908 } 1909 1910 /* 1911 * Find and initialize a new buffer header, freeing up existing buffers 1912 * in the bufqueues as necessary. The new buffer is returned locked. 1913 * 1914 * If repurpose is non-NULL getnewbuf() is allowed to re-purpose an existing 1915 * buffer. The buffer will be disassociated, its page and page mappings 1916 * left intact, and returned with *repurpose set to 1. Else *repurpose is set 1917 * to 0. If 1, the caller must repurpose the underlying VM pages. 1918 * 1919 * If repurpose is NULL getnewbuf() is not allowed to re-purpose an 1920 * existing buffer. That is, it must completely initialize the returned 1921 * buffer. 1922 * 1923 * Important: B_INVAL is not set. If the caller wishes to throw the 1924 * buffer away, the caller must set B_INVAL prior to calling brelse(). 1925 * 1926 * We block if: 1927 * We have insufficient buffer headers 1928 * We have insufficient buffer space 1929 * 1930 * To avoid VFS layer recursion we do not flush dirty buffers ourselves. 1931 * Instead we ask the buf daemon to do it for us. We attempt to 1932 * avoid piecemeal wakeups of the pageout daemon. 1933 */ 1934 struct buf * 1935 getnewbuf(int blkflags, int slptimeo, int size, int maxsize, 1936 struct vm_object **repurposep) 1937 { 1938 struct bufpcpu *pcpu; 1939 struct buf *bp; 1940 struct buf *nbp; 1941 int nqindex; 1942 int nqcpu; 1943 int slpflags = (blkflags & GETBLK_PCATCH) ? PCATCH : 0; 1944 int maxloops = 200000; 1945 int restart_reason = 0; 1946 struct buf *restart_bp = NULL; 1947 static char flushingbufs[MAXCPU]; 1948 char *flushingp; 1949 1950 /* 1951 * We can't afford to block since we might be holding a vnode lock, 1952 * which may prevent system daemons from running. We deal with 1953 * low-memory situations by proactively returning memory and running 1954 * async I/O rather then sync I/O. 1955 */ 1956 1957 ++getnewbufcalls; 1958 nqcpu = mycpu->gd_cpuid; 1959 flushingp = &flushingbufs[nqcpu]; 1960 restart: 1961 if (bufspace < lobufspace) 1962 *flushingp = 0; 1963 1964 if (debug_bufbio && --maxloops == 0) 1965 panic("getnewbuf, excessive loops on cpu %d restart %d (%p)", 1966 mycpu->gd_cpuid, restart_reason, restart_bp); 1967 1968 /* 1969 * Setup for scan. If we do not have enough free buffers, 1970 * we setup a degenerate case that immediately fails. Note 1971 * that if we are specially marked process, we are allowed to 1972 * dip into our reserves. 1973 * 1974 * The scanning sequence is nominally: EMPTY->CLEAN 1975 */ 1976 pcpu = &bufpcpu[nqcpu]; 1977 spin_lock(&pcpu->spin); 1978 1979 /* 1980 * Determine if repurposing should be disallowed. Generally speaking 1981 * do not repurpose buffers if the buffer cache hasn't capped. Also 1982 * control repurposing based on buffer-cache -> main-memory bandwidth. 1983 * That is, we want to recycle buffers normally up until the buffer 1984 * cache bandwidth (new-buffer bw) exceeds bufcache_bw. 1985 * 1986 * (This is heuristical, SMP collisions are ok) 1987 */ 1988 if (repurposep) { 1989 int delta = ticks - bufcache_bw_ticks; 1990 if (delta < 0 || delta >= hz) { 1991 atomic_swap_long(&bufcache_bw_accum, 0); 1992 atomic_swap_int(&bufcache_bw_ticks, ticks); 1993 } 1994 atomic_add_long(&bufcache_bw_accum, size); 1995 if (bufspace < lobufspace) { 1996 repurposep = NULL; 1997 } else if (bufcache_bw_accum < bufcache_bw) { 1998 repurposep = NULL; 1999 } 2000 } 2001 2002 /* 2003 * Prime the scan for this cpu. Locate the first buffer to 2004 * check. If we are flushing buffers we must skip the 2005 * EMPTY queue. 2006 */ 2007 nqindex = BQUEUE_EMPTY; 2008 nbp = TAILQ_FIRST(&pcpu->bufqueues[BQUEUE_EMPTY]); 2009 if (nbp == NULL || *flushingp || repurposep) { 2010 nqindex = BQUEUE_CLEAN; 2011 nbp = TAILQ_FIRST(&pcpu->bufqueues[BQUEUE_CLEAN]); 2012 } 2013 2014 /* 2015 * Run scan, possibly freeing data and/or kva mappings on the fly, 2016 * depending. 2017 * 2018 * WARNING! spin is held! 2019 */ 2020 while ((bp = nbp) != NULL) { 2021 int qindex = nqindex; 2022 2023 nbp = TAILQ_NEXT(bp, b_freelist); 2024 2025 /* 2026 * BQUEUE_CLEAN - B_AGE special case. If not set the bp 2027 * cycles through the queue twice before being selected. 2028 */ 2029 if (qindex == BQUEUE_CLEAN && 2030 (bp->b_flags & B_AGE) == 0 && nbp) { 2031 bp->b_flags |= B_AGE; 2032 TAILQ_REMOVE(&pcpu->bufqueues[qindex], 2033 bp, b_freelist); 2034 TAILQ_INSERT_TAIL(&pcpu->bufqueues[qindex], 2035 bp, b_freelist); 2036 continue; 2037 } 2038 2039 /* 2040 * Calculate next bp ( we can only use it if we do not block 2041 * or do other fancy things ). 2042 */ 2043 if (nbp == NULL) { 2044 switch(qindex) { 2045 case BQUEUE_EMPTY: 2046 nqindex = BQUEUE_CLEAN; 2047 if ((nbp = TAILQ_FIRST(&pcpu->bufqueues[BQUEUE_CLEAN]))) 2048 break; 2049 /* fall through */ 2050 case BQUEUE_CLEAN: 2051 /* 2052 * nbp is NULL. 2053 */ 2054 break; 2055 } 2056 } 2057 2058 /* 2059 * Sanity Checks 2060 */ 2061 KASSERT(bp->b_qindex == qindex, 2062 ("getnewbuf: inconsistent queue %d bp %p", qindex, bp)); 2063 2064 /* 2065 * Note: we no longer distinguish between VMIO and non-VMIO 2066 * buffers. 2067 */ 2068 KASSERT((bp->b_flags & B_DELWRI) == 0, 2069 ("delwri buffer %p found in queue %d", bp, qindex)); 2070 2071 /* 2072 * Do not try to reuse a buffer with a non-zero b_refs. 2073 * This is an unsynchronized test. A synchronized test 2074 * is also performed after we lock the buffer. 2075 */ 2076 if (bp->b_refs) 2077 continue; 2078 2079 /* 2080 * Start freeing the bp. This is somewhat involved. nbp 2081 * remains valid only for BQUEUE_EMPTY bp's. Buffers 2082 * on the clean list must be disassociated from their 2083 * current vnode. Buffers on the empty lists have 2084 * already been disassociated. 2085 * 2086 * b_refs is checked after locking along with queue changes. 2087 * We must check here to deal with zero->nonzero transitions 2088 * made by the owner of the buffer lock, which is used by 2089 * VFS's to hold the buffer while issuing an unlocked 2090 * uiomove()s. We cannot invalidate the buffer's pages 2091 * for this case. Once we successfully lock a buffer the 2092 * only 0->1 transitions of b_refs will occur via findblk(). 2093 * 2094 * We must also check for queue changes after successful 2095 * locking as the current lock holder may dispose of the 2096 * buffer and change its queue. 2097 */ 2098 if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0) { 2099 spin_unlock(&pcpu->spin); 2100 tsleep(&bd_request, 0, "gnbxxx", (hz + 99) / 100); 2101 restart_reason = 1; 2102 restart_bp = bp; 2103 goto restart; 2104 } 2105 if (bp->b_qindex != qindex || bp->b_refs) { 2106 spin_unlock(&pcpu->spin); 2107 BUF_UNLOCK(bp); 2108 restart_reason = 2; 2109 restart_bp = bp; 2110 goto restart; 2111 } 2112 bremfree_locked(bp); 2113 spin_unlock(&pcpu->spin); 2114 2115 /* 2116 * Dependancies must be handled before we disassociate the 2117 * vnode. 2118 * 2119 * NOTE: HAMMER will set B_LOCKED if the buffer cannot 2120 * be immediately disassociated. HAMMER then becomes 2121 * responsible for releasing the buffer. 2122 * 2123 * NOTE: spin is UNLOCKED now. 2124 */ 2125 if (LIST_FIRST(&bp->b_dep) != NULL) { 2126 buf_deallocate(bp); 2127 if (bp->b_flags & B_LOCKED) { 2128 bqrelse(bp); 2129 restart_reason = 3; 2130 restart_bp = bp; 2131 goto restart; 2132 } 2133 KKASSERT(LIST_FIRST(&bp->b_dep) == NULL); 2134 } 2135 2136 /* 2137 * CLEAN buffers have content or associations that must be 2138 * cleaned out if not repurposing. 2139 */ 2140 if (qindex == BQUEUE_CLEAN) { 2141 if (bp->b_flags & B_VMIO) { 2142 if (repurpose_enable && 2143 repurposep && bp->b_bufsize && 2144 (bp->b_flags & (B_DELWRI | B_MALLOC)) == 0) { 2145 *repurposep = bp->b_vp->v_object; 2146 vm_object_hold(*repurposep); 2147 } else { 2148 vfs_vmio_release(bp); 2149 } 2150 } 2151 if (bp->b_vp) 2152 brelvp(bp); 2153 } 2154 2155 /* 2156 * NOTE: nbp is now entirely invalid. We can only restart 2157 * the scan from this point on. 2158 * 2159 * Get the rest of the buffer freed up. b_kva* is still 2160 * valid after this operation. 2161 */ 2162 KASSERT(bp->b_vp == NULL, 2163 ("bp3 %p flags %08x vnode %p qindex %d " 2164 "unexpectededly still associated!", 2165 bp, bp->b_flags, bp->b_vp, qindex)); 2166 KKASSERT((bp->b_flags & B_HASHED) == 0); 2167 2168 if (repurposep == NULL || *repurposep == NULL) { 2169 if (bp->b_bufsize) 2170 allocbuf(bp, 0); 2171 } 2172 2173 if (bp->b_flags & (B_VNDIRTY | B_VNCLEAN | B_HASHED)) { 2174 kprintf("getnewbuf: caught bug vp queue " 2175 "%p/%08x qidx %d\n", 2176 bp, bp->b_flags, qindex); 2177 brelvp(bp); 2178 } 2179 bp->b_flags = B_BNOCLIP; 2180 bp->b_cmd = BUF_CMD_DONE; 2181 bp->b_vp = NULL; 2182 bp->b_error = 0; 2183 bp->b_resid = 0; 2184 bp->b_bcount = 0; 2185 if (repurposep == NULL || *repurposep == NULL) 2186 bp->b_xio.xio_npages = 0; 2187 bp->b_dirtyoff = bp->b_dirtyend = 0; 2188 bp->b_act_count = ACT_INIT; 2189 reinitbufbio(bp); 2190 KKASSERT(LIST_FIRST(&bp->b_dep) == NULL); 2191 buf_dep_init(bp); 2192 if (blkflags & GETBLK_BHEAVY) 2193 bp->b_flags |= B_HEAVY; 2194 2195 if (bufspace >= hibufspace) 2196 *flushingp = 1; 2197 if (bufspace < lobufspace) 2198 *flushingp = 0; 2199 if (*flushingp) { 2200 if (repurposep && *repurposep != NULL) { 2201 bp->b_flags |= B_VMIO; 2202 vfs_vmio_release(bp); 2203 if (bp->b_bufsize) 2204 allocbuf(bp, 0); 2205 vm_object_drop(*repurposep); 2206 *repurposep = NULL; 2207 } 2208 bp->b_flags |= B_INVAL; 2209 brelse(bp); 2210 restart_reason = 5; 2211 restart_bp = bp; 2212 goto restart; 2213 } 2214 2215 /* 2216 * b_refs can transition to a non-zero value while we hold 2217 * the buffer locked due to a findblk(). Our brelvp() above 2218 * interlocked any future possible transitions due to 2219 * findblk()s. 2220 * 2221 * If we find b_refs to be non-zero we can destroy the 2222 * buffer's contents but we cannot yet reuse the buffer. 2223 */ 2224 if (bp->b_refs) { 2225 if (repurposep && *repurposep != NULL) { 2226 bp->b_flags |= B_VMIO; 2227 vfs_vmio_release(bp); 2228 if (bp->b_bufsize) 2229 allocbuf(bp, 0); 2230 vm_object_drop(*repurposep); 2231 *repurposep = NULL; 2232 } 2233 bp->b_flags |= B_INVAL; 2234 brelse(bp); 2235 restart_reason = 6; 2236 restart_bp = bp; 2237 2238 goto restart; 2239 } 2240 2241 /* 2242 * We found our buffer! 2243 */ 2244 break; 2245 } 2246 2247 /* 2248 * If we exhausted our list, iterate other cpus. If that fails, 2249 * sleep as appropriate. We may have to wakeup various daemons 2250 * and write out some dirty buffers. 2251 * 2252 * Generally we are sleeping due to insufficient buffer space. 2253 * 2254 * NOTE: spin is held if bp is NULL, else it is not held. 2255 */ 2256 if (bp == NULL) { 2257 int flags; 2258 char *waitmsg; 2259 2260 spin_unlock(&pcpu->spin); 2261 2262 nqcpu = (nqcpu + 1) % ncpus; 2263 if (nqcpu != mycpu->gd_cpuid) { 2264 restart_reason = 7; 2265 restart_bp = bp; 2266 goto restart; 2267 } 2268 2269 if (bufspace >= hibufspace) { 2270 waitmsg = "bufspc"; 2271 flags = VFS_BIO_NEED_BUFSPACE; 2272 } else { 2273 waitmsg = "newbuf"; 2274 flags = VFS_BIO_NEED_ANY; 2275 } 2276 2277 bd_speedup(); /* heeeelp */ 2278 atomic_set_int(&needsbuffer, flags); 2279 while (needsbuffer & flags) { 2280 int value; 2281 2282 tsleep_interlock(&needsbuffer, 0); 2283 value = atomic_fetchadd_int(&needsbuffer, 0); 2284 if (value & flags) { 2285 if (tsleep(&needsbuffer, PINTERLOCKED|slpflags, 2286 waitmsg, slptimeo)) { 2287 return (NULL); 2288 } 2289 } 2290 } 2291 } else { 2292 /* 2293 * We finally have a valid bp. Reset b_data. 2294 * 2295 * (spin is not held) 2296 */ 2297 bp->b_data = bp->b_kvabase; 2298 } 2299 return(bp); 2300 } 2301 2302 /* 2303 * buf_daemon: 2304 * 2305 * Buffer flushing daemon. Buffers are normally flushed by the 2306 * update daemon but if it cannot keep up this process starts to 2307 * take the load in an attempt to prevent getnewbuf() from blocking. 2308 * 2309 * Once a flush is initiated it does not stop until the number 2310 * of buffers falls below lodirtybuffers, but we will wake up anyone 2311 * waiting at the mid-point. 2312 */ 2313 static struct kproc_desc buf_kp = { 2314 "bufdaemon", 2315 buf_daemon, 2316 &bufdaemon_td 2317 }; 2318 SYSINIT(bufdaemon, SI_SUB_KTHREAD_BUF, SI_ORDER_FIRST, 2319 kproc_start, &buf_kp); 2320 2321 static struct kproc_desc bufhw_kp = { 2322 "bufdaemon_hw", 2323 buf_daemon_hw, 2324 &bufdaemonhw_td 2325 }; 2326 SYSINIT(bufdaemon_hw, SI_SUB_KTHREAD_BUF, SI_ORDER_FIRST, 2327 kproc_start, &bufhw_kp); 2328 2329 static void 2330 buf_daemon1(struct thread *td, int queue, int (*buf_limit_fn)(long), 2331 int *bd_req) 2332 { 2333 long limit; 2334 struct buf *marker; 2335 2336 marker = kmalloc(sizeof(*marker), M_BIOBUF, M_WAITOK | M_ZERO); 2337 marker->b_flags |= B_MARKER; 2338 marker->b_qindex = BQUEUE_NONE; 2339 marker->b_qcpu = 0; 2340 2341 /* 2342 * This process needs to be suspended prior to shutdown sync. 2343 */ 2344 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc, 2345 td, SHUTDOWN_PRI_LAST); 2346 curthread->td_flags |= TDF_SYSTHREAD; 2347 2348 /* 2349 * This process is allowed to take the buffer cache to the limit 2350 */ 2351 for (;;) { 2352 kproc_suspend_loop(); 2353 2354 /* 2355 * Do the flush as long as the number of dirty buffers 2356 * (including those running) exceeds lodirtybufspace. 2357 * 2358 * When flushing limit running I/O to hirunningspace 2359 * Do the flush. Limit the amount of in-transit I/O we 2360 * allow to build up, otherwise we would completely saturate 2361 * the I/O system. Wakeup any waiting processes before we 2362 * normally would so they can run in parallel with our drain. 2363 * 2364 * Our aggregate normal+HW lo water mark is lodirtybufspace, 2365 * but because we split the operation into two threads we 2366 * have to cut it in half for each thread. 2367 */ 2368 waitrunningbufspace(); 2369 limit = lodirtybufspace / 2; 2370 while (buf_limit_fn(limit)) { 2371 if (flushbufqueues(marker, queue) == 0) 2372 break; 2373 if (runningbufspace < hirunningspace) 2374 continue; 2375 waitrunningbufspace(); 2376 } 2377 2378 /* 2379 * We reached our low water mark, reset the 2380 * request and sleep until we are needed again. 2381 * The sleep is just so the suspend code works. 2382 */ 2383 tsleep_interlock(bd_req, 0); 2384 if (atomic_swap_int(bd_req, 0) == 0) 2385 tsleep(bd_req, PINTERLOCKED, "psleep", hz); 2386 } 2387 /* NOT REACHED */ 2388 /*kfree(marker, M_BIOBUF);*/ 2389 } 2390 2391 static int 2392 buf_daemon_limit(long limit) 2393 { 2394 return (runningbufspace + dirtykvaspace > limit || 2395 dirtybufcount - dirtybufcounthw >= nbuf / 2); 2396 } 2397 2398 static int 2399 buf_daemon_hw_limit(long limit) 2400 { 2401 return (runningbufspace + dirtykvaspace > limit || 2402 dirtybufcounthw >= nbuf / 2); 2403 } 2404 2405 static void 2406 buf_daemon(void) 2407 { 2408 buf_daemon1(bufdaemon_td, BQUEUE_DIRTY, buf_daemon_limit, 2409 &bd_request); 2410 } 2411 2412 static void 2413 buf_daemon_hw(void) 2414 { 2415 buf_daemon1(bufdaemonhw_td, BQUEUE_DIRTY_HW, buf_daemon_hw_limit, 2416 &bd_request_hw); 2417 } 2418 2419 /* 2420 * Flush up to (flushperqueue) buffers in the dirty queue. Each cpu has a 2421 * localized version of the queue. Each call made to this function iterates 2422 * to another cpu. It is desireable to flush several buffers from the same 2423 * cpu's queue at once, as these are likely going to be linear. 2424 * 2425 * We must be careful to free up B_INVAL buffers instead of write them, which 2426 * NFS is particularly sensitive to. 2427 * 2428 * B_RELBUF may only be set by VFSs. We do set B_AGE to indicate that we 2429 * really want to try to get the buffer out and reuse it due to the write 2430 * load on the machine. 2431 * 2432 * We must lock the buffer in order to check its validity before we can mess 2433 * with its contents. spin isn't enough. 2434 */ 2435 static int 2436 flushbufqueues(struct buf *marker, bufq_type_t q) 2437 { 2438 struct bufpcpu *pcpu; 2439 struct buf *bp; 2440 int r = 0; 2441 u_int loops = flushperqueue; 2442 int lcpu = marker->b_qcpu; 2443 2444 KKASSERT(marker->b_qindex == BQUEUE_NONE); 2445 KKASSERT(marker->b_flags & B_MARKER); 2446 2447 again: 2448 /* 2449 * Spinlock needed to perform operations on the queue and may be 2450 * held through a non-blocking BUF_LOCK(), but cannot be held when 2451 * BUF_UNLOCK()ing or through any other major operation. 2452 */ 2453 pcpu = &bufpcpu[marker->b_qcpu]; 2454 spin_lock(&pcpu->spin); 2455 marker->b_qindex = q; 2456 TAILQ_INSERT_HEAD(&pcpu->bufqueues[q], marker, b_freelist); 2457 bp = marker; 2458 2459 while ((bp = TAILQ_NEXT(bp, b_freelist)) != NULL) { 2460 /* 2461 * NOTE: spinlock is always held at the top of the loop 2462 */ 2463 if (bp->b_flags & B_MARKER) 2464 continue; 2465 if ((bp->b_flags & B_DELWRI) == 0) { 2466 kprintf("Unexpected clean buffer %p\n", bp); 2467 continue; 2468 } 2469 if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) 2470 continue; 2471 KKASSERT(bp->b_qcpu == marker->b_qcpu && bp->b_qindex == q); 2472 2473 /* 2474 * Once the buffer is locked we will have no choice but to 2475 * unlock the spinlock around a later BUF_UNLOCK and re-set 2476 * bp = marker when looping. Move the marker now to make 2477 * things easier. 2478 */ 2479 TAILQ_REMOVE(&pcpu->bufqueues[q], marker, b_freelist); 2480 TAILQ_INSERT_AFTER(&pcpu->bufqueues[q], bp, marker, b_freelist); 2481 2482 /* 2483 * Must recheck B_DELWRI after successfully locking 2484 * the buffer. 2485 */ 2486 if ((bp->b_flags & B_DELWRI) == 0) { 2487 spin_unlock(&pcpu->spin); 2488 BUF_UNLOCK(bp); 2489 spin_lock(&pcpu->spin); 2490 bp = marker; 2491 continue; 2492 } 2493 2494 /* 2495 * Remove the buffer from its queue. We still own the 2496 * spinlock here. 2497 */ 2498 _bremfree(bp); 2499 2500 /* 2501 * Disposing of an invalid buffer counts as a flush op 2502 */ 2503 if (bp->b_flags & B_INVAL) { 2504 spin_unlock(&pcpu->spin); 2505 brelse(bp); 2506 goto doloop; 2507 } 2508 2509 /* 2510 * Release the spinlock for the more complex ops we 2511 * are now going to do. 2512 */ 2513 spin_unlock(&pcpu->spin); 2514 lwkt_yield(); 2515 2516 /* 2517 * This is a bit messy 2518 */ 2519 if (LIST_FIRST(&bp->b_dep) != NULL && 2520 (bp->b_flags & B_DEFERRED) == 0 && 2521 buf_countdeps(bp, 0)) { 2522 spin_lock(&pcpu->spin); 2523 TAILQ_INSERT_TAIL(&pcpu->bufqueues[q], bp, b_freelist); 2524 bp->b_qindex = q; 2525 bp->b_flags |= B_DEFERRED; 2526 spin_unlock(&pcpu->spin); 2527 BUF_UNLOCK(bp); 2528 spin_lock(&pcpu->spin); 2529 bp = marker; 2530 continue; 2531 } 2532 2533 /* 2534 * spinlock not held here. 2535 * 2536 * If the buffer has a dependancy, buf_checkwrite() must 2537 * also return 0 for us to be able to initate the write. 2538 * 2539 * If the buffer is flagged B_ERROR it may be requeued 2540 * over and over again, we try to avoid a live lock. 2541 */ 2542 if (LIST_FIRST(&bp->b_dep) != NULL && buf_checkwrite(bp)) { 2543 brelse(bp); 2544 } else if (bp->b_flags & B_ERROR) { 2545 tsleep(bp, 0, "bioer", 1); 2546 bp->b_flags &= ~B_AGE; 2547 cluster_awrite(bp); 2548 } else { 2549 bp->b_flags |= B_AGE; 2550 cluster_awrite(bp); 2551 } 2552 /* bp invalid but needs to be NULL-tested if we break out */ 2553 doloop: 2554 spin_lock(&pcpu->spin); 2555 ++r; 2556 if (--loops == 0) 2557 break; 2558 bp = marker; 2559 } 2560 /* bp is invalid here but can be NULL-tested to advance */ 2561 2562 TAILQ_REMOVE(&pcpu->bufqueues[q], marker, b_freelist); 2563 marker->b_qindex = BQUEUE_NONE; 2564 spin_unlock(&pcpu->spin); 2565 2566 /* 2567 * Advance the marker to be fair. 2568 */ 2569 marker->b_qcpu = (marker->b_qcpu + 1) % ncpus; 2570 if (bp == NULL) { 2571 if (marker->b_qcpu != lcpu) 2572 goto again; 2573 } 2574 2575 return (r); 2576 } 2577 2578 /* 2579 * inmem: 2580 * 2581 * Returns true if no I/O is needed to access the associated VM object. 2582 * This is like findblk except it also hunts around in the VM system for 2583 * the data. 2584 * 2585 * Note that we ignore vm_page_free() races from interrupts against our 2586 * lookup, since if the caller is not protected our return value will not 2587 * be any more valid then otherwise once we exit the critical section. 2588 */ 2589 int 2590 inmem(struct vnode *vp, off_t loffset) 2591 { 2592 vm_object_t obj; 2593 vm_offset_t toff, tinc, size; 2594 vm_page_t m; 2595 int res = 1; 2596 2597 if (findblk(vp, loffset, FINDBLK_TEST)) 2598 return 1; 2599 if (vp->v_mount == NULL) 2600 return 0; 2601 if ((obj = vp->v_object) == NULL) 2602 return 0; 2603 2604 size = PAGE_SIZE; 2605 if (size > vp->v_mount->mnt_stat.f_iosize) 2606 size = vp->v_mount->mnt_stat.f_iosize; 2607 2608 vm_object_hold(obj); 2609 for (toff = 0; toff < vp->v_mount->mnt_stat.f_iosize; toff += tinc) { 2610 m = vm_page_lookup(obj, OFF_TO_IDX(loffset + toff)); 2611 if (m == NULL) { 2612 res = 0; 2613 break; 2614 } 2615 tinc = size; 2616 if (tinc > PAGE_SIZE - ((toff + loffset) & PAGE_MASK)) 2617 tinc = PAGE_SIZE - ((toff + loffset) & PAGE_MASK); 2618 if (vm_page_is_valid(m, 2619 (vm_offset_t) ((toff + loffset) & PAGE_MASK), tinc) == 0) { 2620 res = 0; 2621 break; 2622 } 2623 } 2624 vm_object_drop(obj); 2625 return (res); 2626 } 2627 2628 /* 2629 * findblk: 2630 * 2631 * Locate and return the specified buffer. Unless flagged otherwise, 2632 * a locked buffer will be returned if it exists or NULL if it does not. 2633 * 2634 * findblk()'d buffers are still on the bufqueues and if you intend 2635 * to use your (locked NON-TEST) buffer you need to bremfree(bp) 2636 * and possibly do other stuff to it. 2637 * 2638 * FINDBLK_TEST - Do not lock the buffer. The caller is responsible 2639 * for locking the buffer and ensuring that it remains 2640 * the desired buffer after locking. 2641 * 2642 * FINDBLK_NBLOCK - Lock the buffer non-blocking. If we are unable 2643 * to acquire the lock we return NULL, even if the 2644 * buffer exists. 2645 * 2646 * FINDBLK_REF - Returns the buffer ref'd, which prevents normal 2647 * reuse by getnewbuf() but does not prevent 2648 * disassociation (B_INVAL). Used to avoid deadlocks 2649 * against random (vp,loffset)s due to reassignment. 2650 * 2651 * (0) - Lock the buffer blocking. 2652 */ 2653 struct buf * 2654 findblk(struct vnode *vp, off_t loffset, int flags) 2655 { 2656 struct buf *bp; 2657 int lkflags; 2658 2659 lkflags = LK_EXCLUSIVE; 2660 if (flags & FINDBLK_NBLOCK) 2661 lkflags |= LK_NOWAIT; 2662 2663 for (;;) { 2664 /* 2665 * Lookup. Ref the buf while holding v_token to prevent 2666 * reuse (but does not prevent diassociation). 2667 */ 2668 lwkt_gettoken_shared(&vp->v_token); 2669 bp = buf_rb_hash_RB_LOOKUP(&vp->v_rbhash_tree, loffset); 2670 if (bp == NULL) { 2671 lwkt_reltoken(&vp->v_token); 2672 return(NULL); 2673 } 2674 bqhold(bp); 2675 lwkt_reltoken(&vp->v_token); 2676 2677 /* 2678 * If testing only break and return bp, do not lock. 2679 */ 2680 if (flags & FINDBLK_TEST) 2681 break; 2682 2683 /* 2684 * Lock the buffer, return an error if the lock fails. 2685 * (only FINDBLK_NBLOCK can cause the lock to fail). 2686 */ 2687 if (BUF_LOCK(bp, lkflags)) { 2688 atomic_subtract_int(&bp->b_refs, 1); 2689 /* bp = NULL; not needed */ 2690 return(NULL); 2691 } 2692 2693 /* 2694 * Revalidate the locked buf before allowing it to be 2695 * returned. 2696 */ 2697 if (bp->b_vp == vp && bp->b_loffset == loffset) 2698 break; 2699 atomic_subtract_int(&bp->b_refs, 1); 2700 BUF_UNLOCK(bp); 2701 } 2702 2703 /* 2704 * Success 2705 */ 2706 if ((flags & FINDBLK_REF) == 0) 2707 atomic_subtract_int(&bp->b_refs, 1); 2708 return(bp); 2709 } 2710 2711 /* 2712 * getcacheblk: 2713 * 2714 * Similar to getblk() except only returns the buffer if it is 2715 * B_CACHE and requires no other manipulation. Otherwise NULL 2716 * is returned. NULL is also returned if GETBLK_NOWAIT is set 2717 * and the getblk() would block. 2718 * 2719 * If B_RAM is set the buffer might be just fine, but we return 2720 * NULL anyway because we want the code to fall through to the 2721 * cluster read to issue more read-aheads. Otherwise read-ahead breaks. 2722 * 2723 * If blksize is 0 the buffer cache buffer must already be fully 2724 * cached. 2725 * 2726 * If blksize is non-zero getblk() will be used, allowing a buffer 2727 * to be reinstantiated from its VM backing store. The buffer must 2728 * still be fully cached after reinstantiation to be returned. 2729 */ 2730 struct buf * 2731 getcacheblk(struct vnode *vp, off_t loffset, int blksize, int blkflags) 2732 { 2733 struct buf *bp; 2734 int fndflags = (blkflags & GETBLK_NOWAIT) ? FINDBLK_NBLOCK : 0; 2735 2736 if (blksize) { 2737 bp = getblk(vp, loffset, blksize, blkflags, 0); 2738 if (bp) { 2739 if ((bp->b_flags & (B_INVAL | B_CACHE)) == B_CACHE) { 2740 bp->b_flags &= ~B_AGE; 2741 if (bp->b_flags & B_RAM) { 2742 bqrelse(bp); 2743 bp = NULL; 2744 } 2745 } else { 2746 brelse(bp); 2747 bp = NULL; 2748 } 2749 } 2750 } else { 2751 bp = findblk(vp, loffset, fndflags); 2752 if (bp) { 2753 if ((bp->b_flags & (B_INVAL | B_CACHE | B_RAM)) == 2754 B_CACHE) { 2755 bp->b_flags &= ~B_AGE; 2756 bremfree(bp); 2757 } else { 2758 BUF_UNLOCK(bp); 2759 bp = NULL; 2760 } 2761 } 2762 } 2763 return (bp); 2764 } 2765 2766 /* 2767 * getblk: 2768 * 2769 * Get a block given a specified block and offset into a file/device. 2770 * B_INVAL may or may not be set on return. The caller should clear 2771 * B_INVAL prior to initiating a READ. 2772 * 2773 * IT IS IMPORTANT TO UNDERSTAND THAT IF YOU CALL GETBLK() AND B_CACHE 2774 * IS NOT SET, YOU MUST INITIALIZE THE RETURNED BUFFER, ISSUE A READ, 2775 * OR SET B_INVAL BEFORE RETIRING IT. If you retire a getblk'd buffer 2776 * without doing any of those things the system will likely believe 2777 * the buffer to be valid (especially if it is not B_VMIO), and the 2778 * next getblk() will return the buffer with B_CACHE set. 2779 * 2780 * For a non-VMIO buffer, B_CACHE is set to the opposite of B_INVAL for 2781 * an existing buffer. 2782 * 2783 * For a VMIO buffer, B_CACHE is modified according to the backing VM. 2784 * If getblk()ing a previously 0-sized invalid buffer, B_CACHE is set 2785 * and then cleared based on the backing VM. If the previous buffer is 2786 * non-0-sized but invalid, B_CACHE will be cleared. 2787 * 2788 * If getblk() must create a new buffer, the new buffer is returned with 2789 * both B_INVAL and B_CACHE clear unless it is a VMIO buffer, in which 2790 * case it is returned with B_INVAL clear and B_CACHE set based on the 2791 * backing VM. 2792 * 2793 * getblk() also forces a bwrite() for any B_DELWRI buffer whos 2794 * B_CACHE bit is clear. 2795 * 2796 * What this means, basically, is that the caller should use B_CACHE to 2797 * determine whether the buffer is fully valid or not and should clear 2798 * B_INVAL prior to issuing a read. If the caller intends to validate 2799 * the buffer by loading its data area with something, the caller needs 2800 * to clear B_INVAL. If the caller does this without issuing an I/O, 2801 * the caller should set B_CACHE ( as an optimization ), else the caller 2802 * should issue the I/O and biodone() will set B_CACHE if the I/O was 2803 * a write attempt or if it was a successfull read. If the caller 2804 * intends to issue a READ, the caller must clear B_INVAL and B_ERROR 2805 * prior to issuing the READ. biodone() will *not* clear B_INVAL. 2806 * 2807 * getblk flags: 2808 * 2809 * GETBLK_PCATCH - catch signal if blocked, can cause NULL return 2810 * GETBLK_BHEAVY - heavy-weight buffer cache buffer 2811 */ 2812 struct buf * 2813 getblk(struct vnode *vp, off_t loffset, int size, int blkflags, int slptimeo) 2814 { 2815 struct buf *bp; 2816 int slpflags = (blkflags & GETBLK_PCATCH) ? PCATCH : 0; 2817 int error; 2818 int lkflags; 2819 2820 if (size > MAXBSIZE) 2821 panic("getblk: size(%d) > MAXBSIZE(%d)", size, MAXBSIZE); 2822 if (vp->v_object == NULL) 2823 panic("getblk: vnode %p has no object!", vp); 2824 2825 loop: 2826 if ((bp = findblk(vp, loffset, FINDBLK_REF | FINDBLK_TEST)) != NULL) { 2827 /* 2828 * The buffer was found in the cache, but we need to lock it. 2829 * We must acquire a ref on the bp to prevent reuse, but 2830 * this will not prevent disassociation (brelvp()) so we 2831 * must recheck (vp,loffset) after acquiring the lock. 2832 * 2833 * Without the ref the buffer could potentially be reused 2834 * before we acquire the lock and create a deadlock 2835 * situation between the thread trying to reuse the buffer 2836 * and us due to the fact that we would wind up blocking 2837 * on a random (vp,loffset). 2838 */ 2839 if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) { 2840 if (blkflags & GETBLK_NOWAIT) { 2841 bqdrop(bp); 2842 return(NULL); 2843 } 2844 lkflags = LK_EXCLUSIVE | LK_SLEEPFAIL; 2845 if (blkflags & GETBLK_PCATCH) 2846 lkflags |= LK_PCATCH; 2847 error = BUF_TIMELOCK(bp, lkflags, "getblk", slptimeo); 2848 if (error) { 2849 bqdrop(bp); 2850 if (error == ENOLCK) 2851 goto loop; 2852 return (NULL); 2853 } 2854 /* buffer may have changed on us */ 2855 } 2856 bqdrop(bp); 2857 2858 /* 2859 * Once the buffer has been locked, make sure we didn't race 2860 * a buffer recyclement. Buffers that are no longer hashed 2861 * will have b_vp == NULL, so this takes care of that check 2862 * as well. 2863 */ 2864 if (bp->b_vp != vp || bp->b_loffset != loffset) { 2865 #if 0 2866 kprintf("Warning buffer %p (vp %p loffset %lld) " 2867 "was recycled\n", 2868 bp, vp, (long long)loffset); 2869 #endif 2870 BUF_UNLOCK(bp); 2871 goto loop; 2872 } 2873 2874 /* 2875 * If SZMATCH any pre-existing buffer must be of the requested 2876 * size or NULL is returned. The caller absolutely does not 2877 * want getblk() to bwrite() the buffer on a size mismatch. 2878 */ 2879 if ((blkflags & GETBLK_SZMATCH) && size != bp->b_bcount) { 2880 BUF_UNLOCK(bp); 2881 return(NULL); 2882 } 2883 2884 /* 2885 * All vnode-based buffers must be backed by a VM object. 2886 */ 2887 KKASSERT(bp->b_flags & B_VMIO); 2888 KKASSERT(bp->b_cmd == BUF_CMD_DONE); 2889 bp->b_flags &= ~B_AGE; 2890 2891 /* 2892 * Make sure that B_INVAL buffers do not have a cached 2893 * block number translation. 2894 */ 2895 if ((bp->b_flags & B_INVAL) && (bp->b_bio2.bio_offset != NOOFFSET)) { 2896 kprintf("Warning invalid buffer %p (vp %p loffset %lld)" 2897 " did not have cleared bio_offset cache\n", 2898 bp, vp, (long long)loffset); 2899 clearbiocache(&bp->b_bio2); 2900 } 2901 2902 /* 2903 * The buffer is locked. B_CACHE is cleared if the buffer is 2904 * invalid. 2905 */ 2906 if (bp->b_flags & B_INVAL) 2907 bp->b_flags &= ~B_CACHE; 2908 bremfree(bp); 2909 2910 /* 2911 * Any size inconsistancy with a dirty buffer or a buffer 2912 * with a softupdates dependancy must be resolved. Resizing 2913 * the buffer in such circumstances can lead to problems. 2914 * 2915 * Dirty or dependant buffers are written synchronously. 2916 * Other types of buffers are simply released and 2917 * reconstituted as they may be backed by valid, dirty VM 2918 * pages (but not marked B_DELWRI). 2919 * 2920 * NFS NOTE: NFS buffers which straddle EOF are oddly-sized 2921 * and may be left over from a prior truncation (and thus 2922 * no longer represent the actual EOF point), so we 2923 * definitely do not want to B_NOCACHE the backing store. 2924 */ 2925 if (size != bp->b_bcount) { 2926 if (bp->b_flags & B_DELWRI) { 2927 bp->b_flags |= B_RELBUF; 2928 bwrite(bp); 2929 } else if (LIST_FIRST(&bp->b_dep)) { 2930 bp->b_flags |= B_RELBUF; 2931 bwrite(bp); 2932 } else { 2933 bp->b_flags |= B_RELBUF; 2934 brelse(bp); 2935 } 2936 goto loop; 2937 } 2938 KKASSERT(size <= bp->b_kvasize); 2939 KASSERT(bp->b_loffset != NOOFFSET, 2940 ("getblk: no buffer offset")); 2941 2942 /* 2943 * A buffer with B_DELWRI set and B_CACHE clear must 2944 * be committed before we can return the buffer in 2945 * order to prevent the caller from issuing a read 2946 * ( due to B_CACHE not being set ) and overwriting 2947 * it. 2948 * 2949 * Most callers, including NFS and FFS, need this to 2950 * operate properly either because they assume they 2951 * can issue a read if B_CACHE is not set, or because 2952 * ( for example ) an uncached B_DELWRI might loop due 2953 * to softupdates re-dirtying the buffer. In the latter 2954 * case, B_CACHE is set after the first write completes, 2955 * preventing further loops. 2956 * 2957 * NOTE! b*write() sets B_CACHE. If we cleared B_CACHE 2958 * above while extending the buffer, we cannot allow the 2959 * buffer to remain with B_CACHE set after the write 2960 * completes or it will represent a corrupt state. To 2961 * deal with this we set B_NOCACHE to scrap the buffer 2962 * after the write. 2963 * 2964 * XXX Should this be B_RELBUF instead of B_NOCACHE? 2965 * I'm not even sure this state is still possible 2966 * now that getblk() writes out any dirty buffers 2967 * on size changes. 2968 * 2969 * We might be able to do something fancy, like setting 2970 * B_CACHE in bwrite() except if B_DELWRI is already set, 2971 * so the below call doesn't set B_CACHE, but that gets real 2972 * confusing. This is much easier. 2973 */ 2974 2975 if ((bp->b_flags & (B_CACHE|B_DELWRI)) == B_DELWRI) { 2976 kprintf("getblk: Warning, bp %p loff=%jx DELWRI set " 2977 "and CACHE clear, b_flags %08x\n", 2978 bp, (uintmax_t)bp->b_loffset, bp->b_flags); 2979 bp->b_flags |= B_NOCACHE; 2980 bwrite(bp); 2981 goto loop; 2982 } 2983 } else { 2984 /* 2985 * Buffer is not in-core, create new buffer. The buffer 2986 * returned by getnewbuf() is locked. Note that the returned 2987 * buffer is also considered valid (not marked B_INVAL). 2988 * 2989 * Calculating the offset for the I/O requires figuring out 2990 * the block size. We use DEV_BSIZE for VBLK or VCHR and 2991 * the mount's f_iosize otherwise. If the vnode does not 2992 * have an associated mount we assume that the passed size is 2993 * the block size. 2994 * 2995 * Note that vn_isdisk() cannot be used here since it may 2996 * return a failure for numerous reasons. Note that the 2997 * buffer size may be larger then the block size (the caller 2998 * will use block numbers with the proper multiple). Beware 2999 * of using any v_* fields which are part of unions. In 3000 * particular, in DragonFly the mount point overloading 3001 * mechanism uses the namecache only and the underlying 3002 * directory vnode is not a special case. 3003 */ 3004 int bsize, maxsize; 3005 vm_object_t repurpose; 3006 3007 if (vp->v_type == VBLK || vp->v_type == VCHR) 3008 bsize = DEV_BSIZE; 3009 else if (vp->v_mount) 3010 bsize = vp->v_mount->mnt_stat.f_iosize; 3011 else 3012 bsize = size; 3013 3014 maxsize = size + (loffset & PAGE_MASK); 3015 maxsize = imax(maxsize, bsize); 3016 repurpose = NULL; 3017 3018 /* 3019 * Allow repurposing. The returned buffer may contain VM 3020 * pages associated with its previous incarnation. These 3021 * pages must be repurposed for the new buffer (hopefully 3022 * without disturbing the KVM mapping). 3023 * 3024 * WARNING! If repurpose != NULL on return, the buffer will 3025 * still contain some data from its prior 3026 * incarnation. We MUST properly dispose of this 3027 * data. 3028 */ 3029 bp = getnewbuf(blkflags, slptimeo, size, maxsize, &repurpose); 3030 if (bp == NULL) { 3031 if (slpflags || slptimeo) 3032 return NULL; 3033 goto loop; 3034 } 3035 3036 /* 3037 * Atomically insert the buffer into the hash, so that it can 3038 * be found by findblk(). 3039 * 3040 * If bgetvp() returns non-zero a collision occured, and the 3041 * bp will not be associated with the vnode. 3042 * 3043 * Make sure the translation layer has been cleared. 3044 */ 3045 bp->b_loffset = loffset; 3046 bp->b_bio2.bio_offset = NOOFFSET; 3047 /* bp->b_bio2.bio_next = NULL; */ 3048 3049 if (bgetvp(vp, bp, size)) { 3050 if (repurpose) { 3051 bp->b_flags |= B_VMIO; 3052 repurposebuf(bp, 0); 3053 vm_object_drop(repurpose); 3054 } 3055 bp->b_flags |= B_INVAL; 3056 brelse(bp); 3057 goto loop; 3058 } 3059 3060 /* 3061 * All vnode-based buffers must be backed by a VM object. 3062 */ 3063 KKASSERT(vp->v_object != NULL); 3064 bp->b_flags |= B_VMIO; 3065 KKASSERT(bp->b_cmd == BUF_CMD_DONE); 3066 3067 /* 3068 * If we allowed repurposing of the buffer it will contain 3069 * free-but-held vm_page's, already kmapped, that can be 3070 * repurposed. The repurposebuf() code handles reassigning 3071 * those pages to the new (object, offsets) and dealing with 3072 * the case where the pages already exist. 3073 */ 3074 if (repurpose) { 3075 repurposebuf(bp, size); 3076 vm_object_drop(repurpose); 3077 } else { 3078 allocbuf(bp, size); 3079 } 3080 } 3081 return (bp); 3082 } 3083 3084 /* 3085 * regetblk(bp) 3086 * 3087 * Reacquire a buffer that was previously released to the locked queue, 3088 * or reacquire a buffer which is interlocked by having bioops->io_deallocate 3089 * set B_LOCKED (which handles the acquisition race). 3090 * 3091 * To this end, either B_LOCKED must be set or the dependancy list must be 3092 * non-empty. 3093 */ 3094 void 3095 regetblk(struct buf *bp) 3096 { 3097 KKASSERT((bp->b_flags & B_LOCKED) || LIST_FIRST(&bp->b_dep) != NULL); 3098 BUF_LOCK(bp, LK_EXCLUSIVE | LK_RETRY); 3099 bremfree(bp); 3100 } 3101 3102 /* 3103 * geteblk: 3104 * 3105 * Get an empty, disassociated buffer of given size. The buffer is 3106 * initially set to B_INVAL. 3107 * 3108 * critical section protection is not required for the allocbuf() 3109 * call because races are impossible here. 3110 */ 3111 struct buf * 3112 geteblk(int size) 3113 { 3114 struct buf *bp; 3115 3116 while ((bp = getnewbuf(0, 0, size, MAXBSIZE, NULL)) == NULL) 3117 ; 3118 allocbuf(bp, size); 3119 bp->b_flags |= B_INVAL; /* b_dep cleared by getnewbuf() */ 3120 3121 return (bp); 3122 } 3123 3124 /* 3125 * allocbuf: 3126 * 3127 * This code constitutes the buffer memory from either anonymous system 3128 * memory (in the case of non-VMIO operations) or from an associated 3129 * VM object (in the case of VMIO operations). This code is able to 3130 * resize a buffer up or down. 3131 * 3132 * Note that this code is tricky, and has many complications to resolve 3133 * deadlock or inconsistant data situations. Tread lightly!!! 3134 * There are B_CACHE and B_DELWRI interactions that must be dealt with by 3135 * the caller. Calling this code willy nilly can result in the loss of 3136 * data. 3137 * 3138 * allocbuf() only adjusts B_CACHE for VMIO buffers. getblk() deals with 3139 * B_CACHE for the non-VMIO case. 3140 * 3141 * This routine does not need to be called from a critical section but you 3142 * must own the buffer. 3143 */ 3144 void 3145 allocbuf(struct buf *bp, int size) 3146 { 3147 int newbsize, mbsize; 3148 int i; 3149 3150 if (BUF_REFCNT(bp) == 0) 3151 panic("allocbuf: buffer not busy"); 3152 3153 if (bp->b_kvasize < size) 3154 panic("allocbuf: buffer too small"); 3155 3156 if ((bp->b_flags & B_VMIO) == 0) { 3157 caddr_t origbuf; 3158 int origbufsize; 3159 /* 3160 * Just get anonymous memory from the kernel. Don't 3161 * mess with B_CACHE. 3162 */ 3163 mbsize = roundup2(size, DEV_BSIZE); 3164 if (bp->b_flags & B_MALLOC) 3165 newbsize = mbsize; 3166 else 3167 newbsize = round_page(size); 3168 3169 if (newbsize < bp->b_bufsize) { 3170 /* 3171 * Malloced buffers are not shrunk 3172 */ 3173 if (bp->b_flags & B_MALLOC) { 3174 if (newbsize) { 3175 bp->b_bcount = size; 3176 } else { 3177 kfree(bp->b_data, M_BIOBUF); 3178 if (bp->b_bufsize) { 3179 atomic_subtract_long(&bufmallocspace, bp->b_bufsize); 3180 bp->b_bufsize = 0; 3181 bufspacewakeup(); 3182 } 3183 bp->b_data = bp->b_kvabase; 3184 bp->b_bcount = 0; 3185 bp->b_flags &= ~B_MALLOC; 3186 } 3187 return; 3188 } 3189 vm_hold_free_pages( 3190 bp, 3191 (vm_offset_t) bp->b_data + newbsize, 3192 (vm_offset_t) bp->b_data + bp->b_bufsize); 3193 } else if (newbsize > bp->b_bufsize) { 3194 /* 3195 * We only use malloced memory on the first allocation. 3196 * and revert to page-allocated memory when the buffer 3197 * grows. 3198 */ 3199 if ((bufmallocspace < maxbufmallocspace) && 3200 (bp->b_bufsize == 0) && 3201 (mbsize <= PAGE_SIZE/2)) { 3202 3203 bp->b_data = kmalloc(mbsize, M_BIOBUF, M_WAITOK); 3204 bp->b_bufsize = mbsize; 3205 bp->b_bcount = size; 3206 bp->b_flags |= B_MALLOC; 3207 atomic_add_long(&bufmallocspace, mbsize); 3208 return; 3209 } 3210 origbuf = NULL; 3211 origbufsize = 0; 3212 /* 3213 * If the buffer is growing on its other-than-first 3214 * allocation, then we revert to the page-allocation 3215 * scheme. 3216 */ 3217 if (bp->b_flags & B_MALLOC) { 3218 origbuf = bp->b_data; 3219 origbufsize = bp->b_bufsize; 3220 bp->b_data = bp->b_kvabase; 3221 if (bp->b_bufsize) { 3222 atomic_subtract_long(&bufmallocspace, 3223 bp->b_bufsize); 3224 bp->b_bufsize = 0; 3225 bufspacewakeup(); 3226 } 3227 bp->b_flags &= ~B_MALLOC; 3228 newbsize = round_page(newbsize); 3229 } 3230 vm_hold_load_pages( 3231 bp, 3232 (vm_offset_t) bp->b_data + bp->b_bufsize, 3233 (vm_offset_t) bp->b_data + newbsize); 3234 if (origbuf) { 3235 bcopy(origbuf, bp->b_data, origbufsize); 3236 kfree(origbuf, M_BIOBUF); 3237 } 3238 } 3239 } else { 3240 vm_page_t m; 3241 int desiredpages; 3242 3243 newbsize = roundup2(size, DEV_BSIZE); 3244 desiredpages = ((int)(bp->b_loffset & PAGE_MASK) + 3245 newbsize + PAGE_MASK) >> PAGE_SHIFT; 3246 KKASSERT(desiredpages <= XIO_INTERNAL_PAGES); 3247 3248 if (bp->b_flags & B_MALLOC) 3249 panic("allocbuf: VMIO buffer can't be malloced"); 3250 /* 3251 * Set B_CACHE initially if buffer is 0 length or will become 3252 * 0-length. 3253 */ 3254 if (size == 0 || bp->b_bufsize == 0) 3255 bp->b_flags |= B_CACHE; 3256 3257 if (newbsize < bp->b_bufsize) { 3258 /* 3259 * DEV_BSIZE aligned new buffer size is less then the 3260 * DEV_BSIZE aligned existing buffer size. Figure out 3261 * if we have to remove any pages. 3262 */ 3263 if (desiredpages < bp->b_xio.xio_npages) { 3264 for (i = desiredpages; i < bp->b_xio.xio_npages; i++) { 3265 /* 3266 * the page is not freed here -- it 3267 * is the responsibility of 3268 * vnode_pager_setsize 3269 */ 3270 m = bp->b_xio.xio_pages[i]; 3271 KASSERT(m != bogus_page, 3272 ("allocbuf: bogus page found")); 3273 vm_page_busy_wait(m, TRUE, "biodep"); 3274 bp->b_xio.xio_pages[i] = NULL; 3275 vm_page_unwire(m, 0); 3276 vm_page_wakeup(m); 3277 } 3278 pmap_qremove((vm_offset_t) trunc_page((vm_offset_t)bp->b_data) + 3279 (desiredpages << PAGE_SHIFT), (bp->b_xio.xio_npages - desiredpages)); 3280 bp->b_xio.xio_npages = desiredpages; 3281 } 3282 } else if (size > bp->b_bcount) { 3283 /* 3284 * We are growing the buffer, possibly in a 3285 * byte-granular fashion. 3286 */ 3287 struct vnode *vp; 3288 vm_object_t obj; 3289 vm_offset_t toff; 3290 vm_offset_t tinc; 3291 3292 /* 3293 * Step 1, bring in the VM pages from the object, 3294 * allocating them if necessary. We must clear 3295 * B_CACHE if these pages are not valid for the 3296 * range covered by the buffer. 3297 */ 3298 vp = bp->b_vp; 3299 obj = vp->v_object; 3300 3301 vm_object_hold(obj); 3302 while (bp->b_xio.xio_npages < desiredpages) { 3303 vm_page_t m; 3304 vm_pindex_t pi; 3305 int error; 3306 3307 pi = OFF_TO_IDX(bp->b_loffset) + 3308 bp->b_xio.xio_npages; 3309 3310 /* 3311 * Blocking on m->busy might lead to a 3312 * deadlock: 3313 * 3314 * vm_fault->getpages->cluster_read->allocbuf 3315 */ 3316 m = vm_page_lookup_busy_try(obj, pi, FALSE, 3317 &error); 3318 if (error) { 3319 vm_page_sleep_busy(m, FALSE, "pgtblk"); 3320 continue; 3321 } 3322 if (m == NULL) { 3323 /* 3324 * note: must allocate system pages 3325 * since blocking here could intefere 3326 * with paging I/O, no matter which 3327 * process we are. 3328 */ 3329 m = bio_page_alloc(bp, obj, pi, desiredpages - bp->b_xio.xio_npages); 3330 if (m) { 3331 vm_page_wire(m); 3332 vm_page_wakeup(m); 3333 bp->b_flags &= ~B_CACHE; 3334 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m; 3335 ++bp->b_xio.xio_npages; 3336 } 3337 continue; 3338 } 3339 3340 /* 3341 * We found a page and were able to busy it. 3342 */ 3343 vm_page_wire(m); 3344 vm_page_wakeup(m); 3345 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m; 3346 ++bp->b_xio.xio_npages; 3347 if (bp->b_act_count < m->act_count) 3348 bp->b_act_count = m->act_count; 3349 } 3350 vm_object_drop(obj); 3351 3352 /* 3353 * Step 2. We've loaded the pages into the buffer, 3354 * we have to figure out if we can still have B_CACHE 3355 * set. Note that B_CACHE is set according to the 3356 * byte-granular range ( bcount and size ), not the 3357 * aligned range ( newbsize ). 3358 * 3359 * The VM test is against m->valid, which is DEV_BSIZE 3360 * aligned. Needless to say, the validity of the data 3361 * needs to also be DEV_BSIZE aligned. Note that this 3362 * fails with NFS if the server or some other client 3363 * extends the file's EOF. If our buffer is resized, 3364 * B_CACHE may remain set! XXX 3365 */ 3366 3367 toff = bp->b_bcount; 3368 tinc = PAGE_SIZE - ((bp->b_loffset + toff) & PAGE_MASK); 3369 3370 while ((bp->b_flags & B_CACHE) && toff < size) { 3371 vm_pindex_t pi; 3372 3373 if (tinc > (size - toff)) 3374 tinc = size - toff; 3375 3376 pi = ((bp->b_loffset & PAGE_MASK) + toff) >> 3377 PAGE_SHIFT; 3378 3379 vfs_buf_test_cache( 3380 bp, 3381 bp->b_loffset, 3382 toff, 3383 tinc, 3384 bp->b_xio.xio_pages[pi] 3385 ); 3386 toff += tinc; 3387 tinc = PAGE_SIZE; 3388 } 3389 3390 /* 3391 * Step 3, fixup the KVM pmap. Remember that 3392 * bp->b_data is relative to bp->b_loffset, but 3393 * bp->b_loffset may be offset into the first page. 3394 */ 3395 bp->b_data = (caddr_t) 3396 trunc_page((vm_offset_t)bp->b_data); 3397 pmap_qenter((vm_offset_t)bp->b_data, 3398 bp->b_xio.xio_pages, bp->b_xio.xio_npages); 3399 bp->b_data = (caddr_t)((vm_offset_t)bp->b_data | 3400 (vm_offset_t)(bp->b_loffset & PAGE_MASK)); 3401 } 3402 atomic_add_long(&bufspace, newbsize - bp->b_bufsize); 3403 } 3404 3405 /* adjust space use on already-dirty buffer */ 3406 if (bp->b_flags & B_DELWRI) { 3407 /* dirtykvaspace unchanged */ 3408 atomic_add_long(&dirtybufspace, newbsize - bp->b_bufsize); 3409 if (bp->b_flags & B_HEAVY) { 3410 atomic_add_long(&dirtybufspacehw, 3411 newbsize - bp->b_bufsize); 3412 } 3413 } 3414 bp->b_bufsize = newbsize; /* actual buffer allocation */ 3415 bp->b_bcount = size; /* requested buffer size */ 3416 bufspacewakeup(); 3417 } 3418 3419 /* 3420 * repurposebuf() (VMIO only) 3421 * 3422 * This performs a function similar to allocbuf() but the passed-in buffer 3423 * may contain some detrius from its previous incarnation in the form of 3424 * the page array. We try to repurpose the underlying pages. 3425 * 3426 * This code is nominally called to recycle buffer cache buffers AND (if 3427 * they are clean) to also recycle their underlying pages. We currently 3428 * can only recycle unmapped, clean pages. The code is called when buffer 3429 * cache 'newbuf' bandwidth exceeds (bufrate_cache) bytes per second. 3430 */ 3431 static 3432 void 3433 repurposebuf(struct buf *bp, int size) 3434 { 3435 int newbsize; 3436 int desiredpages; 3437 vm_offset_t toff; 3438 vm_offset_t tinc; 3439 vm_object_t obj; 3440 vm_page_t m; 3441 int i; 3442 int must_reenter = 0; 3443 long deaccumulate = 0; 3444 3445 3446 KKASSERT((bp->b_flags & (B_VMIO | B_DELWRI | B_MALLOC)) == B_VMIO); 3447 if (BUF_REFCNT(bp) == 0) 3448 panic("repurposebuf: buffer not busy"); 3449 3450 if (bp->b_kvasize < size) 3451 panic("repurposebuf: buffer too small"); 3452 3453 newbsize = roundup2(size, DEV_BSIZE); 3454 desiredpages = ((int)(bp->b_loffset & PAGE_MASK) + 3455 newbsize + PAGE_MASK) >> PAGE_SHIFT; 3456 KKASSERT(desiredpages <= XIO_INTERNAL_PAGES); 3457 3458 /* 3459 * Buffer starts out 0-length with B_CACHE set. We will clear 3460 * As we check the backing store we will clear B_CACHE if necessary. 3461 */ 3462 atomic_add_long(&bufspace, newbsize - bp->b_bufsize); 3463 bp->b_bufsize = 0; 3464 bp->b_bcount = 0; 3465 bp->b_flags |= B_CACHE; 3466 3467 if (desiredpages) { 3468 obj = bp->b_vp->v_object; 3469 vm_object_hold(obj); 3470 } else { 3471 obj = NULL; 3472 } 3473 3474 /* 3475 * Step 1, bring in the VM pages from the object, repurposing or 3476 * allocating them if necessary. We must clear B_CACHE if these 3477 * pages are not valid for the range covered by the buffer. 3478 * 3479 * We are growing the buffer, possibly in a byte-granular fashion. 3480 */ 3481 for (i = 0; i < desiredpages; ++i) { 3482 vm_pindex_t pi; 3483 int error; 3484 int iswired; 3485 3486 pi = OFF_TO_IDX(bp->b_loffset) + i; 3487 3488 /* 3489 * Blocking on m->busy might lead to a 3490 * deadlock: 3491 * 3492 * vm_fault->getpages->cluster_read->allocbuf 3493 */ 3494 m = (i < bp->b_xio.xio_npages) ? bp->b_xio.xio_pages[i] : NULL; 3495 bp->b_xio.xio_pages[i] = NULL; 3496 KASSERT(m != bogus_page, ("repurposebuf: bogus page found")); 3497 m = vm_page_repurpose(obj, pi, FALSE, &error, m, 3498 &must_reenter, &iswired); 3499 3500 if (error) { 3501 vm_page_sleep_busy(m, FALSE, "pgtblk"); 3502 --i; /* retry */ 3503 continue; 3504 } 3505 if (m == NULL) { 3506 /* 3507 * note: must allocate system pages 3508 * since blocking here could intefere 3509 * with paging I/O, no matter which 3510 * process we are. 3511 */ 3512 must_reenter = 1; 3513 m = bio_page_alloc(bp, obj, pi, desiredpages - i); 3514 if (m) { 3515 vm_page_wire(m); 3516 vm_page_wakeup(m); 3517 bp->b_flags &= ~B_CACHE; 3518 bp->b_xio.xio_pages[i] = m; 3519 if (m->valid) 3520 deaccumulate += PAGE_SIZE; 3521 } else { 3522 --i; /* retry */ 3523 } 3524 continue; 3525 } 3526 if (m->valid) 3527 deaccumulate += PAGE_SIZE; 3528 3529 /* 3530 * We found a page and were able to busy it. 3531 */ 3532 if (!iswired) 3533 vm_page_wire(m); 3534 vm_page_wakeup(m); 3535 bp->b_xio.xio_pages[i] = m; 3536 if (bp->b_act_count < m->act_count) 3537 bp->b_act_count = m->act_count; 3538 } 3539 if (desiredpages) 3540 vm_object_drop(obj); 3541 3542 /* 3543 * Even though its a new buffer, any pages already in the VM 3544 * page cache should not count towards I/O bandwidth. 3545 */ 3546 if (deaccumulate) 3547 atomic_add_long(&bufcache_bw_accum, -deaccumulate); 3548 3549 /* 3550 * Clean-up any loose pages. 3551 */ 3552 while (i < bp->b_xio.xio_npages) { 3553 m = bp->b_xio.xio_pages[i]; 3554 KASSERT(m != bogus_page, ("repurposebuf: bogus page found")); 3555 vm_page_busy_wait(m, TRUE, "biodep"); 3556 bp->b_xio.xio_pages[i] = NULL; 3557 vm_page_unwire(m, 0); 3558 vm_page_wakeup(m); 3559 ++i; 3560 } 3561 if (desiredpages < bp->b_xio.xio_npages) { 3562 pmap_qremove((vm_offset_t)trunc_page((vm_offset_t)bp->b_data) + 3563 (desiredpages << PAGE_SHIFT), 3564 (bp->b_xio.xio_npages - desiredpages)); 3565 } 3566 bp->b_xio.xio_npages = desiredpages; 3567 3568 /* 3569 * Step 2. We've loaded the pages into the buffer, 3570 * we have to figure out if we can still have B_CACHE 3571 * set. Note that B_CACHE is set according to the 3572 * byte-granular range ( bcount and size ), not the 3573 * aligned range ( newbsize ). 3574 * 3575 * The VM test is against m->valid, which is DEV_BSIZE 3576 * aligned. Needless to say, the validity of the data 3577 * needs to also be DEV_BSIZE aligned. Note that this 3578 * fails with NFS if the server or some other client 3579 * extends the file's EOF. If our buffer is resized, 3580 * B_CACHE may remain set! XXX 3581 */ 3582 toff = bp->b_bcount; 3583 tinc = PAGE_SIZE - ((bp->b_loffset + toff) & PAGE_MASK); 3584 3585 while ((bp->b_flags & B_CACHE) && toff < size) { 3586 vm_pindex_t pi; 3587 3588 if (tinc > (size - toff)) 3589 tinc = size - toff; 3590 3591 pi = ((bp->b_loffset & PAGE_MASK) + toff) >> PAGE_SHIFT; 3592 3593 vfs_buf_test_cache(bp, bp->b_loffset, toff, 3594 tinc, bp->b_xio.xio_pages[pi]); 3595 toff += tinc; 3596 tinc = PAGE_SIZE; 3597 } 3598 3599 /* 3600 * Step 3, fixup the KVM pmap. Remember that 3601 * bp->b_data is relative to bp->b_loffset, but 3602 * bp->b_loffset may be offset into the first page. 3603 */ 3604 bp->b_data = (caddr_t)trunc_page((vm_offset_t)bp->b_data); 3605 if (must_reenter) { 3606 pmap_qenter((vm_offset_t)bp->b_data, 3607 bp->b_xio.xio_pages, bp->b_xio.xio_npages); 3608 } else { 3609 atomic_add_long(&repurposedspace, newbsize); 3610 } 3611 bp->b_data = (caddr_t)((vm_offset_t)bp->b_data | 3612 (vm_offset_t)(bp->b_loffset & PAGE_MASK)); 3613 3614 if (newbsize < bp->b_bufsize) 3615 bufspacewakeup(); 3616 bp->b_bufsize = newbsize; /* actual buffer allocation */ 3617 bp->b_bcount = size; /* requested buffer size */ 3618 } 3619 3620 /* 3621 * biowait: 3622 * 3623 * Wait for buffer I/O completion, returning error status. B_EINTR 3624 * is converted into an EINTR error but not cleared (since a chain 3625 * of biowait() calls may occur). 3626 * 3627 * On return bpdone() will have been called but the buffer will remain 3628 * locked and will not have been brelse()'d. 3629 * 3630 * NOTE! If a timeout is specified and ETIMEDOUT occurs the I/O is 3631 * likely still in progress on return. 3632 * 3633 * NOTE! This operation is on a BIO, not a BUF. 3634 * 3635 * NOTE! BIO_DONE is cleared by vn_strategy() 3636 */ 3637 static __inline int 3638 _biowait(struct bio *bio, const char *wmesg, int to) 3639 { 3640 struct buf *bp = bio->bio_buf; 3641 u_int32_t flags; 3642 u_int32_t nflags; 3643 int error; 3644 3645 KKASSERT(bio == &bp->b_bio1); 3646 for (;;) { 3647 flags = bio->bio_flags; 3648 if (flags & BIO_DONE) 3649 break; 3650 nflags = flags | BIO_WANT; 3651 tsleep_interlock(bio, 0); 3652 if (atomic_cmpset_int(&bio->bio_flags, flags, nflags)) { 3653 if (wmesg) 3654 error = tsleep(bio, PINTERLOCKED, wmesg, to); 3655 else if (bp->b_cmd == BUF_CMD_READ) 3656 error = tsleep(bio, PINTERLOCKED, "biord", to); 3657 else 3658 error = tsleep(bio, PINTERLOCKED, "biowr", to); 3659 if (error) { 3660 kprintf("tsleep error biowait %d\n", error); 3661 return (error); 3662 } 3663 } 3664 } 3665 3666 /* 3667 * Finish up. 3668 */ 3669 KKASSERT(bp->b_cmd == BUF_CMD_DONE); 3670 bio->bio_flags &= ~(BIO_DONE | BIO_SYNC); 3671 if (bp->b_flags & B_EINTR) 3672 return (EINTR); 3673 if (bp->b_flags & B_ERROR) 3674 return (bp->b_error ? bp->b_error : EIO); 3675 return (0); 3676 } 3677 3678 int 3679 biowait(struct bio *bio, const char *wmesg) 3680 { 3681 return(_biowait(bio, wmesg, 0)); 3682 } 3683 3684 int 3685 biowait_timeout(struct bio *bio, const char *wmesg, int to) 3686 { 3687 return(_biowait(bio, wmesg, to)); 3688 } 3689 3690 /* 3691 * This associates a tracking count with an I/O. vn_strategy() and 3692 * dev_dstrategy() do this automatically but there are a few cases 3693 * where a vnode or device layer is bypassed when a block translation 3694 * is cached. In such cases bio_start_transaction() may be called on 3695 * the bypassed layers so the system gets an I/O in progress indication 3696 * for those higher layers. 3697 */ 3698 void 3699 bio_start_transaction(struct bio *bio, struct bio_track *track) 3700 { 3701 bio->bio_track = track; 3702 bio_track_ref(track); 3703 dsched_buf_enter(bio->bio_buf); /* might stack */ 3704 } 3705 3706 /* 3707 * Initiate I/O on a vnode. 3708 * 3709 * SWAPCACHE OPERATION: 3710 * 3711 * Real buffer cache buffers have a non-NULL bp->b_vp. Unfortunately 3712 * devfs also uses b_vp for fake buffers so we also have to check 3713 * that B_PAGING is 0. In this case the passed 'vp' is probably the 3714 * underlying block device. The swap assignments are related to the 3715 * buffer cache buffer's b_vp, not the passed vp. 3716 * 3717 * The passed vp == bp->b_vp only in the case where the strategy call 3718 * is made on the vp itself for its own buffers (a regular file or 3719 * block device vp). The filesystem usually then re-calls vn_strategy() 3720 * after translating the request to an underlying device. 3721 * 3722 * Cluster buffers set B_CLUSTER and the passed vp is the vp of the 3723 * underlying buffer cache buffers. 3724 * 3725 * We can only deal with page-aligned buffers at the moment, because 3726 * we can't tell what the real dirty state for pages straddling a buffer 3727 * are. 3728 * 3729 * In order to call swap_pager_strategy() we must provide the VM object 3730 * and base offset for the underlying buffer cache pages so it can find 3731 * the swap blocks. 3732 */ 3733 void 3734 vn_strategy(struct vnode *vp, struct bio *bio) 3735 { 3736 struct bio_track *track; 3737 struct buf *bp = bio->bio_buf; 3738 3739 KKASSERT(bp->b_cmd != BUF_CMD_DONE); 3740 3741 /* 3742 * Set when an I/O is issued on the bp. Cleared by consumers 3743 * (aka HAMMER), allowing the consumer to determine if I/O had 3744 * actually occurred. 3745 */ 3746 bp->b_flags |= B_IOISSUED; 3747 3748 /* 3749 * Handle the swap cache intercept. 3750 */ 3751 if (vn_cache_strategy(vp, bio)) 3752 return; 3753 3754 /* 3755 * Otherwise do the operation through the filesystem 3756 */ 3757 if (bp->b_cmd == BUF_CMD_READ) 3758 track = &vp->v_track_read; 3759 else 3760 track = &vp->v_track_write; 3761 KKASSERT((bio->bio_flags & BIO_DONE) == 0); 3762 bio->bio_track = track; 3763 bio_track_ref(track); 3764 dsched_buf_enter(bp); /* might stack */ 3765 vop_strategy(*vp->v_ops, vp, bio); 3766 } 3767 3768 static void vn_cache_strategy_callback(struct bio *bio); 3769 3770 int 3771 vn_cache_strategy(struct vnode *vp, struct bio *bio) 3772 { 3773 struct buf *bp = bio->bio_buf; 3774 struct bio *nbio; 3775 vm_object_t object; 3776 vm_page_t m; 3777 int i; 3778 3779 /* 3780 * Stop using swapcache if paniced, dumping, or dumped 3781 */ 3782 if (panicstr || dumping) 3783 return(0); 3784 3785 /* 3786 * Is this buffer cache buffer suitable for reading from 3787 * the swap cache? 3788 */ 3789 if (vm_swapcache_read_enable == 0 || 3790 bp->b_cmd != BUF_CMD_READ || 3791 ((bp->b_flags & B_CLUSTER) == 0 && 3792 (bp->b_vp == NULL || (bp->b_flags & B_PAGING))) || 3793 ((int)bp->b_loffset & PAGE_MASK) != 0 || 3794 (bp->b_bcount & PAGE_MASK) != 0) { 3795 return(0); 3796 } 3797 3798 /* 3799 * Figure out the original VM object (it will match the underlying 3800 * VM pages). Note that swap cached data uses page indices relative 3801 * to that object, not relative to bio->bio_offset. 3802 */ 3803 if (bp->b_flags & B_CLUSTER) 3804 object = vp->v_object; 3805 else 3806 object = bp->b_vp->v_object; 3807 3808 /* 3809 * In order to be able to use the swap cache all underlying VM 3810 * pages must be marked as such, and we can't have any bogus pages. 3811 */ 3812 for (i = 0; i < bp->b_xio.xio_npages; ++i) { 3813 m = bp->b_xio.xio_pages[i]; 3814 if ((m->flags & PG_SWAPPED) == 0) 3815 break; 3816 if (m == bogus_page) 3817 break; 3818 } 3819 3820 /* 3821 * If we are good then issue the I/O using swap_pager_strategy(). 3822 * 3823 * We can only do this if the buffer actually supports object-backed 3824 * I/O. If it doesn't npages will be 0. 3825 */ 3826 if (i && i == bp->b_xio.xio_npages) { 3827 m = bp->b_xio.xio_pages[0]; 3828 nbio = push_bio(bio); 3829 nbio->bio_done = vn_cache_strategy_callback; 3830 nbio->bio_offset = ptoa(m->pindex); 3831 KKASSERT(m->object == object); 3832 swap_pager_strategy(object, nbio); 3833 return(1); 3834 } 3835 return(0); 3836 } 3837 3838 /* 3839 * This is a bit of a hack but since the vn_cache_strategy() function can 3840 * override a VFS's strategy function we must make sure that the bio, which 3841 * is probably bio2, doesn't leak an unexpected offset value back to the 3842 * filesystem. The filesystem (e.g. UFS) might otherwise assume that the 3843 * bio went through its own file strategy function and the the bio2 offset 3844 * is a cached disk offset when, in fact, it isn't. 3845 */ 3846 static void 3847 vn_cache_strategy_callback(struct bio *bio) 3848 { 3849 bio->bio_offset = NOOFFSET; 3850 biodone(pop_bio(bio)); 3851 } 3852 3853 /* 3854 * bpdone: 3855 * 3856 * Finish I/O on a buffer after all BIOs have been processed. 3857 * Called when the bio chain is exhausted or by biowait. If called 3858 * by biowait, elseit is typically 0. 3859 * 3860 * bpdone is also responsible for setting B_CACHE in a B_VMIO bp. 3861 * In a non-VMIO bp, B_CACHE will be set on the next getblk() 3862 * assuming B_INVAL is clear. 3863 * 3864 * For the VMIO case, we set B_CACHE if the op was a read and no 3865 * read error occured, or if the op was a write. B_CACHE is never 3866 * set if the buffer is invalid or otherwise uncacheable. 3867 * 3868 * bpdone does not mess with B_INVAL, allowing the I/O routine or the 3869 * initiator to leave B_INVAL set to brelse the buffer out of existance 3870 * in the biodone routine. 3871 * 3872 * bpdone is responsible for calling bundirty() on the buffer after a 3873 * successful write. We previously did this prior to initiating the 3874 * write under the assumption that the buffer might be dirtied again 3875 * while the write was in progress, however doing it before-hand creates 3876 * a race condition prior to the call to vn_strategy() where the 3877 * filesystem may not be aware that a dirty buffer is present. 3878 * It should not be possible for the buffer or its underlying pages to 3879 * be redirtied prior to bpdone()'s unbusying of the underlying VM 3880 * pages. 3881 */ 3882 void 3883 bpdone(struct buf *bp, int elseit) 3884 { 3885 buf_cmd_t cmd; 3886 3887 KASSERT(BUF_REFCNTNB(bp) > 0, 3888 ("bpdone: bp %p not busy %d", bp, BUF_REFCNTNB(bp))); 3889 KASSERT(bp->b_cmd != BUF_CMD_DONE, 3890 ("bpdone: bp %p already done!", bp)); 3891 3892 /* 3893 * No more BIOs are left. All completion functions have been dealt 3894 * with, now we clean up the buffer. 3895 */ 3896 cmd = bp->b_cmd; 3897 bp->b_cmd = BUF_CMD_DONE; 3898 3899 /* 3900 * Only reads and writes are processed past this point. 3901 */ 3902 if (cmd != BUF_CMD_READ && cmd != BUF_CMD_WRITE) { 3903 if (cmd == BUF_CMD_FREEBLKS) 3904 bp->b_flags |= B_NOCACHE; 3905 if (elseit) 3906 brelse(bp); 3907 return; 3908 } 3909 3910 /* 3911 * A failed write must re-dirty the buffer unless B_INVAL 3912 * was set. 3913 * 3914 * A successful write must clear the dirty flag. This is done after 3915 * the write to ensure that the buffer remains on the vnode's dirty 3916 * list for filesystem interlocks / checks until the write is actually 3917 * complete. HAMMER2 is sensitive to this issue. 3918 * 3919 * Only applicable to normal buffers (with VPs). vinum buffers may 3920 * not have a vp. 3921 * 3922 * Must be done prior to calling buf_complete() as the callback might 3923 * re-dirty the buffer. 3924 */ 3925 if (cmd == BUF_CMD_WRITE) { 3926 if ((bp->b_flags & (B_ERROR | B_INVAL)) == B_ERROR) { 3927 bp->b_flags &= ~B_NOCACHE; 3928 if (bp->b_vp) 3929 bdirty(bp); 3930 } else { 3931 if (bp->b_vp) 3932 bundirty(bp); 3933 } 3934 } 3935 3936 /* 3937 * Warning: softupdates may re-dirty the buffer, and HAMMER can do 3938 * a lot worse. XXX - move this above the clearing of b_cmd 3939 */ 3940 if (LIST_FIRST(&bp->b_dep) != NULL) 3941 buf_complete(bp); 3942 3943 if (bp->b_flags & B_VMIO) { 3944 int i; 3945 vm_ooffset_t foff; 3946 vm_page_t m; 3947 vm_object_t obj; 3948 int iosize; 3949 struct vnode *vp = bp->b_vp; 3950 3951 obj = vp->v_object; 3952 3953 #if defined(VFS_BIO_DEBUG) 3954 if (vp->v_auxrefs == 0) 3955 panic("bpdone: zero vnode hold count"); 3956 if ((vp->v_flag & VOBJBUF) == 0) 3957 panic("bpdone: vnode is not setup for merged cache"); 3958 #endif 3959 3960 foff = bp->b_loffset; 3961 KASSERT(foff != NOOFFSET, ("bpdone: no buffer offset")); 3962 KASSERT(obj != NULL, ("bpdone: missing VM object")); 3963 3964 #if defined(VFS_BIO_DEBUG) 3965 if (obj->paging_in_progress < bp->b_xio.xio_npages) { 3966 kprintf("bpdone: paging in progress(%d) < " 3967 "bp->b_xio.xio_npages(%d)\n", 3968 obj->paging_in_progress, 3969 bp->b_xio.xio_npages); 3970 } 3971 #endif 3972 3973 /* 3974 * Set B_CACHE if the op was a normal read and no error 3975 * occured. B_CACHE is set for writes in the b*write() 3976 * routines. 3977 */ 3978 iosize = bp->b_bcount - bp->b_resid; 3979 if (cmd == BUF_CMD_READ && 3980 (bp->b_flags & (B_INVAL|B_NOCACHE|B_ERROR)) == 0) { 3981 bp->b_flags |= B_CACHE; 3982 } 3983 3984 vm_object_hold(obj); 3985 for (i = 0; i < bp->b_xio.xio_npages; i++) { 3986 int resid; 3987 int isbogus; 3988 3989 resid = ((foff + PAGE_SIZE) & ~(off_t)PAGE_MASK) - foff; 3990 if (resid > iosize) 3991 resid = iosize; 3992 3993 /* 3994 * cleanup bogus pages, restoring the originals. Since 3995 * the originals should still be wired, we don't have 3996 * to worry about interrupt/freeing races destroying 3997 * the VM object association. 3998 */ 3999 m = bp->b_xio.xio_pages[i]; 4000 if (m == bogus_page) { 4001 if ((bp->b_flags & B_HASBOGUS) == 0) 4002 panic("bpdone: bp %p corrupt bogus", bp); 4003 m = vm_page_lookup(obj, OFF_TO_IDX(foff)); 4004 if (m == NULL) 4005 panic("bpdone: page disappeared"); 4006 bp->b_xio.xio_pages[i] = m; 4007 isbogus = 1; 4008 } else { 4009 isbogus = 0; 4010 } 4011 #if defined(VFS_BIO_DEBUG) 4012 if (OFF_TO_IDX(foff) != m->pindex) { 4013 kprintf("bpdone: foff(%lu)/m->pindex(%ld) " 4014 "mismatch\n", 4015 (unsigned long)foff, (long)m->pindex); 4016 } 4017 #endif 4018 4019 /* 4020 * In the write case, the valid and clean bits are 4021 * already changed correctly (see bdwrite()), so we 4022 * only need to do this here in the read case. 4023 */ 4024 vm_page_busy_wait(m, FALSE, "bpdpgw"); 4025 if (cmd == BUF_CMD_READ && isbogus == 0 && resid > 0) 4026 vfs_clean_one_page(bp, i, m); 4027 4028 /* 4029 * when debugging new filesystems or buffer I/O 4030 * methods, this is the most common error that pops 4031 * up. if you see this, you have not set the page 4032 * busy flag correctly!!! 4033 */ 4034 if (m->busy == 0) { 4035 kprintf("bpdone: page busy < 0, " 4036 "pindex: %d, foff: 0x(%x,%x), " 4037 "resid: %d, index: %d\n", 4038 (int) m->pindex, (int)(foff >> 32), 4039 (int) foff & 0xffffffff, resid, i); 4040 if (!vn_isdisk(vp, NULL)) 4041 kprintf(" iosize: %ld, loffset: %lld, " 4042 "flags: 0x%08x, npages: %d\n", 4043 bp->b_vp->v_mount->mnt_stat.f_iosize, 4044 (long long)bp->b_loffset, 4045 bp->b_flags, bp->b_xio.xio_npages); 4046 else 4047 kprintf(" VDEV, loffset: %lld, flags: 0x%08x, npages: %d\n", 4048 (long long)bp->b_loffset, 4049 bp->b_flags, bp->b_xio.xio_npages); 4050 kprintf(" valid: 0x%x, dirty: 0x%x, " 4051 "wired: %d\n", 4052 m->valid, m->dirty, 4053 m->wire_count); 4054 panic("bpdone: page busy < 0"); 4055 } 4056 vm_page_io_finish(m); 4057 vm_page_wakeup(m); 4058 vm_object_pip_wakeup(obj); 4059 foff = (foff + PAGE_SIZE) & ~(off_t)PAGE_MASK; 4060 iosize -= resid; 4061 } 4062 if (bp->b_flags & B_HASBOGUS) { 4063 pmap_qenter(trunc_page((vm_offset_t)bp->b_data), 4064 bp->b_xio.xio_pages, bp->b_xio.xio_npages); 4065 bp->b_flags &= ~B_HASBOGUS; 4066 } 4067 vm_object_drop(obj); 4068 } 4069 4070 /* 4071 * Finish up by releasing the buffer. There are no more synchronous 4072 * or asynchronous completions, those were handled by bio_done 4073 * callbacks. 4074 */ 4075 if (elseit) { 4076 if (bp->b_flags & (B_NOCACHE|B_INVAL|B_ERROR|B_RELBUF)) 4077 brelse(bp); 4078 else 4079 bqrelse(bp); 4080 } 4081 } 4082 4083 /* 4084 * Normal biodone. 4085 */ 4086 void 4087 biodone(struct bio *bio) 4088 { 4089 struct buf *bp = bio->bio_buf; 4090 4091 runningbufwakeup(bp); 4092 4093 /* 4094 * Run up the chain of BIO's. Leave b_cmd intact for the duration. 4095 */ 4096 while (bio) { 4097 biodone_t *done_func; 4098 struct bio_track *track; 4099 4100 /* 4101 * BIO tracking. Most but not all BIOs are tracked. 4102 */ 4103 if ((track = bio->bio_track) != NULL) { 4104 bio_track_rel(track); 4105 bio->bio_track = NULL; 4106 } 4107 4108 /* 4109 * A bio_done function terminates the loop. The function 4110 * will be responsible for any further chaining and/or 4111 * buffer management. 4112 * 4113 * WARNING! The done function can deallocate the buffer! 4114 */ 4115 if ((done_func = bio->bio_done) != NULL) { 4116 bio->bio_done = NULL; 4117 done_func(bio); 4118 return; 4119 } 4120 bio = bio->bio_prev; 4121 } 4122 4123 /* 4124 * If we've run out of bio's do normal [a]synchronous completion. 4125 */ 4126 bpdone(bp, 1); 4127 } 4128 4129 /* 4130 * Synchronous biodone - this terminates a synchronous BIO. 4131 * 4132 * bpdone() is called with elseit=FALSE, leaving the buffer completed 4133 * but still locked. The caller must brelse() the buffer after waiting 4134 * for completion. 4135 */ 4136 void 4137 biodone_sync(struct bio *bio) 4138 { 4139 struct buf *bp = bio->bio_buf; 4140 int flags; 4141 int nflags; 4142 4143 KKASSERT(bio == &bp->b_bio1); 4144 bpdone(bp, 0); 4145 4146 for (;;) { 4147 flags = bio->bio_flags; 4148 nflags = (flags | BIO_DONE) & ~BIO_WANT; 4149 4150 if (atomic_cmpset_int(&bio->bio_flags, flags, nflags)) { 4151 if (flags & BIO_WANT) 4152 wakeup(bio); 4153 break; 4154 } 4155 } 4156 } 4157 4158 /* 4159 * vfs_unbusy_pages: 4160 * 4161 * This routine is called in lieu of iodone in the case of 4162 * incomplete I/O. This keeps the busy status for pages 4163 * consistant. 4164 */ 4165 void 4166 vfs_unbusy_pages(struct buf *bp) 4167 { 4168 int i; 4169 4170 runningbufwakeup(bp); 4171 4172 if (bp->b_flags & B_VMIO) { 4173 struct vnode *vp = bp->b_vp; 4174 vm_object_t obj; 4175 4176 obj = vp->v_object; 4177 vm_object_hold(obj); 4178 4179 for (i = 0; i < bp->b_xio.xio_npages; i++) { 4180 vm_page_t m = bp->b_xio.xio_pages[i]; 4181 4182 /* 4183 * When restoring bogus changes the original pages 4184 * should still be wired, so we are in no danger of 4185 * losing the object association and do not need 4186 * critical section protection particularly. 4187 */ 4188 if (m == bogus_page) { 4189 m = vm_page_lookup(obj, OFF_TO_IDX(bp->b_loffset) + i); 4190 if (!m) { 4191 panic("vfs_unbusy_pages: page missing"); 4192 } 4193 bp->b_xio.xio_pages[i] = m; 4194 } 4195 vm_page_busy_wait(m, FALSE, "bpdpgw"); 4196 vm_page_io_finish(m); 4197 vm_page_wakeup(m); 4198 vm_object_pip_wakeup(obj); 4199 } 4200 if (bp->b_flags & B_HASBOGUS) { 4201 pmap_qenter(trunc_page((vm_offset_t)bp->b_data), 4202 bp->b_xio.xio_pages, bp->b_xio.xio_npages); 4203 bp->b_flags &= ~B_HASBOGUS; 4204 } 4205 vm_object_drop(obj); 4206 } 4207 } 4208 4209 /* 4210 * vfs_busy_pages: 4211 * 4212 * This routine is called before a device strategy routine. 4213 * It is used to tell the VM system that paging I/O is in 4214 * progress, and treat the pages associated with the buffer 4215 * almost as being PG_BUSY. Also the object 'paging_in_progress' 4216 * flag is handled to make sure that the object doesn't become 4217 * inconsistant. 4218 * 4219 * Since I/O has not been initiated yet, certain buffer flags 4220 * such as B_ERROR or B_INVAL may be in an inconsistant state 4221 * and should be ignored. 4222 */ 4223 void 4224 vfs_busy_pages(struct vnode *vp, struct buf *bp) 4225 { 4226 int i, bogus; 4227 struct lwp *lp = curthread->td_lwp; 4228 4229 /* 4230 * The buffer's I/O command must already be set. If reading, 4231 * B_CACHE must be 0 (double check against callers only doing 4232 * I/O when B_CACHE is 0). 4233 */ 4234 KKASSERT(bp->b_cmd != BUF_CMD_DONE); 4235 KKASSERT(bp->b_cmd == BUF_CMD_WRITE || (bp->b_flags & B_CACHE) == 0); 4236 4237 if (bp->b_flags & B_VMIO) { 4238 vm_object_t obj; 4239 4240 obj = vp->v_object; 4241 KASSERT(bp->b_loffset != NOOFFSET, 4242 ("vfs_busy_pages: no buffer offset")); 4243 4244 /* 4245 * Busy all the pages. We have to busy them all at once 4246 * to avoid deadlocks. 4247 */ 4248 retry: 4249 for (i = 0; i < bp->b_xio.xio_npages; i++) { 4250 vm_page_t m = bp->b_xio.xio_pages[i]; 4251 4252 if (vm_page_busy_try(m, FALSE)) { 4253 vm_page_sleep_busy(m, FALSE, "vbpage"); 4254 while (--i >= 0) 4255 vm_page_wakeup(bp->b_xio.xio_pages[i]); 4256 goto retry; 4257 } 4258 } 4259 4260 /* 4261 * Setup for I/O, soft-busy the page right now because 4262 * the next loop may block. 4263 */ 4264 for (i = 0; i < bp->b_xio.xio_npages; i++) { 4265 vm_page_t m = bp->b_xio.xio_pages[i]; 4266 4267 if ((bp->b_flags & B_CLUSTER) == 0) { 4268 vm_object_pip_add(obj, 1); 4269 vm_page_io_start(m); 4270 } 4271 } 4272 4273 /* 4274 * Adjust protections for I/O and do bogus-page mapping. 4275 * Assume that vm_page_protect() can block (it can block 4276 * if VM_PROT_NONE, don't take any chances regardless). 4277 * 4278 * In particular note that for writes we must incorporate 4279 * page dirtyness from the VM system into the buffer's 4280 * dirty range. 4281 * 4282 * For reads we theoretically must incorporate page dirtyness 4283 * from the VM system to determine if the page needs bogus 4284 * replacement, but we shortcut the test by simply checking 4285 * that all m->valid bits are set, indicating that the page 4286 * is fully valid and does not need to be re-read. For any 4287 * VM system dirtyness the page will also be fully valid 4288 * since it was mapped at one point. 4289 */ 4290 bogus = 0; 4291 for (i = 0; i < bp->b_xio.xio_npages; i++) { 4292 vm_page_t m = bp->b_xio.xio_pages[i]; 4293 4294 if (bp->b_cmd == BUF_CMD_WRITE) { 4295 /* 4296 * When readying a vnode-backed buffer for 4297 * a write we must zero-fill any invalid 4298 * portions of the backing VM pages, mark 4299 * it valid and clear related dirty bits. 4300 * 4301 * vfs_clean_one_page() incorporates any 4302 * VM dirtyness and updates the b_dirtyoff 4303 * range (after we've made the page RO). 4304 * 4305 * It is also expected that the pmap modified 4306 * bit has already been cleared by the 4307 * vm_page_protect(). We may not be able 4308 * to clear all dirty bits for a page if it 4309 * was also memory mapped (NFS). 4310 * 4311 * Finally be sure to unassign any swap-cache 4312 * backing store as it is now stale. 4313 */ 4314 vm_page_protect(m, VM_PROT_READ); 4315 vfs_clean_one_page(bp, i, m); 4316 swap_pager_unswapped(m); 4317 } else if (m->valid == VM_PAGE_BITS_ALL) { 4318 /* 4319 * When readying a vnode-backed buffer for 4320 * read we must replace any dirty pages with 4321 * a bogus page so dirty data is not destroyed 4322 * when filling gaps. 4323 * 4324 * To avoid testing whether the page is 4325 * dirty we instead test that the page was 4326 * at some point mapped (m->valid fully 4327 * valid) with the understanding that 4328 * this also covers the dirty case. 4329 */ 4330 bp->b_xio.xio_pages[i] = bogus_page; 4331 bp->b_flags |= B_HASBOGUS; 4332 bogus++; 4333 } else if (m->valid & m->dirty) { 4334 /* 4335 * This case should not occur as partial 4336 * dirtyment can only happen if the buffer 4337 * is B_CACHE, and this code is not entered 4338 * if the buffer is B_CACHE. 4339 */ 4340 kprintf("Warning: vfs_busy_pages - page not " 4341 "fully valid! loff=%jx bpf=%08x " 4342 "idx=%d val=%02x dir=%02x\n", 4343 (uintmax_t)bp->b_loffset, bp->b_flags, 4344 i, m->valid, m->dirty); 4345 vm_page_protect(m, VM_PROT_NONE); 4346 } else { 4347 /* 4348 * The page is not valid and can be made 4349 * part of the read. 4350 */ 4351 vm_page_protect(m, VM_PROT_NONE); 4352 } 4353 vm_page_wakeup(m); 4354 } 4355 if (bogus) { 4356 pmap_qenter(trunc_page((vm_offset_t)bp->b_data), 4357 bp->b_xio.xio_pages, bp->b_xio.xio_npages); 4358 } 4359 } 4360 4361 /* 4362 * This is the easiest place to put the process accounting for the I/O 4363 * for now. 4364 */ 4365 if (lp != NULL) { 4366 if (bp->b_cmd == BUF_CMD_READ) 4367 lp->lwp_ru.ru_inblock++; 4368 else 4369 lp->lwp_ru.ru_oublock++; 4370 } 4371 } 4372 4373 /* 4374 * Tell the VM system that the pages associated with this buffer 4375 * are clean. This is used for delayed writes where the data is 4376 * going to go to disk eventually without additional VM intevention. 4377 * 4378 * NOTE: While we only really need to clean through to b_bcount, we 4379 * just go ahead and clean through to b_bufsize. 4380 */ 4381 static void 4382 vfs_clean_pages(struct buf *bp) 4383 { 4384 vm_page_t m; 4385 int i; 4386 4387 if ((bp->b_flags & B_VMIO) == 0) 4388 return; 4389 4390 KASSERT(bp->b_loffset != NOOFFSET, 4391 ("vfs_clean_pages: no buffer offset")); 4392 4393 for (i = 0; i < bp->b_xio.xio_npages; i++) { 4394 m = bp->b_xio.xio_pages[i]; 4395 vfs_clean_one_page(bp, i, m); 4396 } 4397 } 4398 4399 /* 4400 * vfs_clean_one_page: 4401 * 4402 * Set the valid bits and clear the dirty bits in a page within a 4403 * buffer. The range is restricted to the buffer's size and the 4404 * buffer's logical offset might index into the first page. 4405 * 4406 * The caller has busied or soft-busied the page and it is not mapped, 4407 * test and incorporate the dirty bits into b_dirtyoff/end before 4408 * clearing them. Note that we need to clear the pmap modified bits 4409 * after determining the the page was dirty, vm_page_set_validclean() 4410 * does not do it for us. 4411 * 4412 * This routine is typically called after a read completes (dirty should 4413 * be zero in that case as we are not called on bogus-replace pages), 4414 * or before a write is initiated. 4415 */ 4416 static void 4417 vfs_clean_one_page(struct buf *bp, int pageno, vm_page_t m) 4418 { 4419 int bcount; 4420 int xoff; 4421 int soff; 4422 int eoff; 4423 4424 /* 4425 * Calculate offset range within the page but relative to buffer's 4426 * loffset. loffset might be offset into the first page. 4427 */ 4428 xoff = (int)bp->b_loffset & PAGE_MASK; /* loffset offset into pg 0 */ 4429 bcount = bp->b_bcount + xoff; /* offset adjusted */ 4430 4431 if (pageno == 0) { 4432 soff = xoff; 4433 eoff = PAGE_SIZE; 4434 } else { 4435 soff = (pageno << PAGE_SHIFT); 4436 eoff = soff + PAGE_SIZE; 4437 } 4438 if (eoff > bcount) 4439 eoff = bcount; 4440 if (soff >= eoff) 4441 return; 4442 4443 /* 4444 * Test dirty bits and adjust b_dirtyoff/end. 4445 * 4446 * If dirty pages are incorporated into the bp any prior 4447 * B_NEEDCOMMIT state (NFS) must be cleared because the 4448 * caller has not taken into account the new dirty data. 4449 * 4450 * If the page was memory mapped the dirty bits might go beyond the 4451 * end of the buffer, but we can't really make the assumption that 4452 * a file EOF straddles the buffer (even though this is the case for 4453 * NFS if B_NEEDCOMMIT is also set). So for the purposes of clearing 4454 * B_NEEDCOMMIT we only test the dirty bits covered by the buffer. 4455 * This also saves some console spam. 4456 * 4457 * When clearing B_NEEDCOMMIT we must also clear B_CLUSTEROK, 4458 * NFS can handle huge commits but not huge writes. 4459 */ 4460 vm_page_test_dirty(m); 4461 if (m->dirty) { 4462 if ((bp->b_flags & B_NEEDCOMMIT) && 4463 (m->dirty & vm_page_bits(soff & PAGE_MASK, eoff - soff))) { 4464 if (debug_commit) 4465 kprintf("Warning: vfs_clean_one_page: bp %p " 4466 "loff=%jx,%d flgs=%08x clr B_NEEDCOMMIT" 4467 " cmd %d vd %02x/%02x x/s/e %d %d %d " 4468 "doff/end %d %d\n", 4469 bp, (uintmax_t)bp->b_loffset, bp->b_bcount, 4470 bp->b_flags, bp->b_cmd, 4471 m->valid, m->dirty, xoff, soff, eoff, 4472 bp->b_dirtyoff, bp->b_dirtyend); 4473 bp->b_flags &= ~(B_NEEDCOMMIT | B_CLUSTEROK); 4474 if (debug_commit) 4475 print_backtrace(-1); 4476 } 4477 /* 4478 * Only clear the pmap modified bits if ALL the dirty bits 4479 * are set, otherwise the system might mis-clear portions 4480 * of a page. 4481 */ 4482 if (m->dirty == VM_PAGE_BITS_ALL && 4483 (bp->b_flags & B_NEEDCOMMIT) == 0) { 4484 pmap_clear_modify(m); 4485 } 4486 if (bp->b_dirtyoff > soff - xoff) 4487 bp->b_dirtyoff = soff - xoff; 4488 if (bp->b_dirtyend < eoff - xoff) 4489 bp->b_dirtyend = eoff - xoff; 4490 } 4491 4492 /* 4493 * Set related valid bits, clear related dirty bits. 4494 * Does not mess with the pmap modified bit. 4495 * 4496 * WARNING! We cannot just clear all of m->dirty here as the 4497 * buffer cache buffers may use a DEV_BSIZE'd aligned 4498 * block size, or have an odd size (e.g. NFS at file EOF). 4499 * The putpages code can clear m->dirty to 0. 4500 * 4501 * If a VOP_WRITE generates a buffer cache buffer which 4502 * covers the same space as mapped writable pages the 4503 * buffer flush might not be able to clear all the dirty 4504 * bits and still require a putpages from the VM system 4505 * to finish it off. 4506 * 4507 * WARNING! vm_page_set_validclean() currently assumes vm_token 4508 * is held. The page might not be busied (bdwrite() case). 4509 * XXX remove this comment once we've validated that this 4510 * is no longer an issue. 4511 */ 4512 vm_page_set_validclean(m, soff & PAGE_MASK, eoff - soff); 4513 } 4514 4515 #if 0 4516 /* 4517 * Similar to vfs_clean_one_page() but sets the bits to valid and dirty. 4518 * The page data is assumed to be valid (there is no zeroing here). 4519 */ 4520 static void 4521 vfs_dirty_one_page(struct buf *bp, int pageno, vm_page_t m) 4522 { 4523 int bcount; 4524 int xoff; 4525 int soff; 4526 int eoff; 4527 4528 /* 4529 * Calculate offset range within the page but relative to buffer's 4530 * loffset. loffset might be offset into the first page. 4531 */ 4532 xoff = (int)bp->b_loffset & PAGE_MASK; /* loffset offset into pg 0 */ 4533 bcount = bp->b_bcount + xoff; /* offset adjusted */ 4534 4535 if (pageno == 0) { 4536 soff = xoff; 4537 eoff = PAGE_SIZE; 4538 } else { 4539 soff = (pageno << PAGE_SHIFT); 4540 eoff = soff + PAGE_SIZE; 4541 } 4542 if (eoff > bcount) 4543 eoff = bcount; 4544 if (soff >= eoff) 4545 return; 4546 vm_page_set_validdirty(m, soff & PAGE_MASK, eoff - soff); 4547 } 4548 #endif 4549 4550 /* 4551 * vfs_bio_clrbuf: 4552 * 4553 * Clear a buffer. This routine essentially fakes an I/O, so we need 4554 * to clear B_ERROR and B_INVAL. 4555 * 4556 * Note that while we only theoretically need to clear through b_bcount, 4557 * we go ahead and clear through b_bufsize. 4558 */ 4559 4560 void 4561 vfs_bio_clrbuf(struct buf *bp) 4562 { 4563 int i, mask = 0; 4564 caddr_t sa, ea; 4565 if ((bp->b_flags & (B_VMIO | B_MALLOC)) == B_VMIO) { 4566 bp->b_flags &= ~(B_INVAL | B_EINTR | B_ERROR); 4567 if ((bp->b_xio.xio_npages == 1) && (bp->b_bufsize < PAGE_SIZE) && 4568 (bp->b_loffset & PAGE_MASK) == 0) { 4569 mask = (1 << (bp->b_bufsize / DEV_BSIZE)) - 1; 4570 if ((bp->b_xio.xio_pages[0]->valid & mask) == mask) { 4571 bp->b_resid = 0; 4572 return; 4573 } 4574 if ((bp->b_xio.xio_pages[0]->valid & mask) == 0) { 4575 bzero(bp->b_data, bp->b_bufsize); 4576 bp->b_xio.xio_pages[0]->valid |= mask; 4577 bp->b_resid = 0; 4578 return; 4579 } 4580 } 4581 sa = bp->b_data; 4582 for(i=0;i<bp->b_xio.xio_npages;i++,sa=ea) { 4583 int j = ((vm_offset_t)sa & PAGE_MASK) / DEV_BSIZE; 4584 ea = (caddr_t)trunc_page((vm_offset_t)sa + PAGE_SIZE); 4585 ea = (caddr_t)(vm_offset_t)ulmin( 4586 (u_long)(vm_offset_t)ea, 4587 (u_long)(vm_offset_t)bp->b_data + bp->b_bufsize); 4588 mask = ((1 << ((ea - sa) / DEV_BSIZE)) - 1) << j; 4589 if ((bp->b_xio.xio_pages[i]->valid & mask) == mask) 4590 continue; 4591 if ((bp->b_xio.xio_pages[i]->valid & mask) == 0) { 4592 bzero(sa, ea - sa); 4593 } else { 4594 for (; sa < ea; sa += DEV_BSIZE, j++) { 4595 if ((bp->b_xio.xio_pages[i]->valid & 4596 (1<<j)) == 0) { 4597 bzero(sa, DEV_BSIZE); 4598 } 4599 } 4600 } 4601 bp->b_xio.xio_pages[i]->valid |= mask; 4602 } 4603 bp->b_resid = 0; 4604 } else { 4605 clrbuf(bp); 4606 } 4607 } 4608 4609 /* 4610 * vm_hold_load_pages: 4611 * 4612 * Load pages into the buffer's address space. The pages are 4613 * allocated from the kernel object in order to reduce interference 4614 * with the any VM paging I/O activity. The range of loaded 4615 * pages will be wired. 4616 * 4617 * If a page cannot be allocated, the 'pagedaemon' is woken up to 4618 * retrieve the full range (to - from) of pages. 4619 */ 4620 void 4621 vm_hold_load_pages(struct buf *bp, vm_offset_t from, vm_offset_t to) 4622 { 4623 vm_offset_t pg; 4624 vm_page_t p; 4625 int index; 4626 4627 to = round_page(to); 4628 from = round_page(from); 4629 index = (from - trunc_page((vm_offset_t)bp->b_data)) >> PAGE_SHIFT; 4630 4631 pg = from; 4632 while (pg < to) { 4633 /* 4634 * Note: must allocate system pages since blocking here 4635 * could intefere with paging I/O, no matter which 4636 * process we are. 4637 */ 4638 vm_object_hold(&kernel_object); 4639 p = bio_page_alloc(bp, &kernel_object, pg >> PAGE_SHIFT, 4640 (vm_pindex_t)((to - pg) >> PAGE_SHIFT)); 4641 vm_object_drop(&kernel_object); 4642 if (p) { 4643 vm_page_wire(p); 4644 p->valid = VM_PAGE_BITS_ALL; 4645 pmap_kenter_noinval(pg, VM_PAGE_TO_PHYS(p)); 4646 bp->b_xio.xio_pages[index] = p; 4647 vm_page_wakeup(p); 4648 4649 pg += PAGE_SIZE; 4650 ++index; 4651 } 4652 } 4653 pmap_invalidate_range(&kernel_pmap, from, to); 4654 bp->b_xio.xio_npages = index; 4655 } 4656 4657 /* 4658 * Allocate a page for a buffer cache buffer. 4659 * 4660 * If NULL is returned the caller is expected to retry (typically check if 4661 * the page already exists on retry before trying to allocate one). 4662 * 4663 * NOTE! Low-memory handling is dealt with in b[q]relse(), not here. This 4664 * function will use the system reserve with the hope that the page 4665 * allocations can be returned to PQ_CACHE/PQ_FREE when the caller 4666 * is done with the buffer. 4667 * 4668 * NOTE! However, TMPFS is a special case because flushing a dirty buffer 4669 * to TMPFS doesn't clean the page. For TMPFS, only the pagedaemon 4670 * is capable of retiring pages (to swap). For TMPFS we don't dig 4671 * into the system reserve because doing so could stall out pretty 4672 * much every process running on the system. 4673 */ 4674 static 4675 vm_page_t 4676 bio_page_alloc(struct buf *bp, vm_object_t obj, vm_pindex_t pg, int deficit) 4677 { 4678 int vmflags = VM_ALLOC_NORMAL | VM_ALLOC_NULL_OK; 4679 vm_page_t p; 4680 4681 ASSERT_LWKT_TOKEN_HELD(vm_object_token(obj)); 4682 4683 /* 4684 * Try a normal allocation first. 4685 */ 4686 p = vm_page_alloc(obj, pg, vmflags); 4687 if (p) 4688 return(p); 4689 if (vm_page_lookup(obj, pg)) 4690 return(NULL); 4691 vm_pageout_deficit += deficit; 4692 4693 /* 4694 * Try again, digging into the system reserve. 4695 * 4696 * Trying to recover pages from the buffer cache here can deadlock 4697 * against other threads trying to busy underlying pages so we 4698 * depend on the code in brelse() and bqrelse() to free/cache the 4699 * underlying buffer cache pages when memory is low. 4700 */ 4701 if (curthread->td_flags & TDF_SYSTHREAD) 4702 vmflags |= VM_ALLOC_SYSTEM | VM_ALLOC_INTERRUPT; 4703 else if (bp->b_vp && bp->b_vp->v_tag == VT_TMPFS) 4704 vmflags |= 0; 4705 else 4706 vmflags |= VM_ALLOC_SYSTEM; 4707 4708 /*recoverbufpages();*/ 4709 p = vm_page_alloc(obj, pg, vmflags); 4710 if (p) 4711 return(p); 4712 if (vm_page_lookup(obj, pg)) 4713 return(NULL); 4714 4715 /* 4716 * Wait for memory to free up and try again 4717 */ 4718 if (vm_page_count_severe()) 4719 ++lowmempgallocs; 4720 vm_wait(hz / 20 + 1); 4721 4722 p = vm_page_alloc(obj, pg, vmflags); 4723 if (p) 4724 return(p); 4725 if (vm_page_lookup(obj, pg)) 4726 return(NULL); 4727 4728 /* 4729 * Ok, now we are really in trouble. 4730 */ 4731 { 4732 static struct krate biokrate = { .freq = 1 }; 4733 krateprintf(&biokrate, 4734 "Warning: bio_page_alloc: memory exhausted " 4735 "during buffer cache page allocation from %s\n", 4736 curthread->td_comm); 4737 } 4738 if (curthread->td_flags & TDF_SYSTHREAD) 4739 vm_wait(hz / 20 + 1); 4740 else 4741 vm_wait(hz / 2 + 1); 4742 return (NULL); 4743 } 4744 4745 /* 4746 * vm_hold_free_pages: 4747 * 4748 * Return pages associated with the buffer back to the VM system. 4749 * 4750 * The range of pages underlying the buffer's address space will 4751 * be unmapped and un-wired. 4752 */ 4753 void 4754 vm_hold_free_pages(struct buf *bp, vm_offset_t from, vm_offset_t to) 4755 { 4756 vm_offset_t pg; 4757 vm_page_t p; 4758 int index, newnpages; 4759 4760 from = round_page(from); 4761 to = round_page(to); 4762 index = (from - trunc_page((vm_offset_t)bp->b_data)) >> PAGE_SHIFT; 4763 newnpages = index; 4764 4765 for (pg = from; pg < to; pg += PAGE_SIZE, index++) { 4766 p = bp->b_xio.xio_pages[index]; 4767 if (p && (index < bp->b_xio.xio_npages)) { 4768 if (p->busy) { 4769 kprintf("vm_hold_free_pages: doffset: %lld, " 4770 "loffset: %lld\n", 4771 (long long)bp->b_bio2.bio_offset, 4772 (long long)bp->b_loffset); 4773 } 4774 bp->b_xio.xio_pages[index] = NULL; 4775 pmap_kremove_noinval(pg); 4776 vm_page_busy_wait(p, FALSE, "vmhldpg"); 4777 vm_page_unwire(p, 0); 4778 vm_page_free(p); 4779 } 4780 } 4781 pmap_invalidate_range(&kernel_pmap, from, to); 4782 bp->b_xio.xio_npages = newnpages; 4783 } 4784 4785 /* 4786 * vmapbuf: 4787 * 4788 * Map a user buffer into KVM via a pbuf. On return the buffer's 4789 * b_data, b_bufsize, and b_bcount will be set, and its XIO page array 4790 * initialized. 4791 */ 4792 int 4793 vmapbuf(struct buf *bp, caddr_t udata, int bytes) 4794 { 4795 caddr_t addr; 4796 vm_offset_t va; 4797 vm_page_t m; 4798 int vmprot; 4799 int error; 4800 int pidx; 4801 int i; 4802 4803 /* 4804 * bp had better have a command and it better be a pbuf. 4805 */ 4806 KKASSERT(bp->b_cmd != BUF_CMD_DONE); 4807 KKASSERT(bp->b_flags & B_PAGING); 4808 KKASSERT(bp->b_kvabase); 4809 4810 if (bytes < 0) 4811 return (-1); 4812 4813 /* 4814 * Map the user data into KVM. Mappings have to be page-aligned. 4815 */ 4816 addr = (caddr_t)trunc_page((vm_offset_t)udata); 4817 pidx = 0; 4818 4819 vmprot = VM_PROT_READ; 4820 if (bp->b_cmd == BUF_CMD_READ) 4821 vmprot |= VM_PROT_WRITE; 4822 4823 while (addr < udata + bytes) { 4824 /* 4825 * Do the vm_fault if needed; do the copy-on-write thing 4826 * when reading stuff off device into memory. 4827 * 4828 * vm_fault_page*() returns a held VM page. 4829 */ 4830 va = (addr >= udata) ? (vm_offset_t)addr : (vm_offset_t)udata; 4831 va = trunc_page(va); 4832 4833 m = vm_fault_page_quick(va, vmprot, &error); 4834 if (m == NULL) { 4835 for (i = 0; i < pidx; ++i) { 4836 vm_page_unhold(bp->b_xio.xio_pages[i]); 4837 bp->b_xio.xio_pages[i] = NULL; 4838 } 4839 return(-1); 4840 } 4841 bp->b_xio.xio_pages[pidx] = m; 4842 addr += PAGE_SIZE; 4843 ++pidx; 4844 } 4845 4846 /* 4847 * Map the page array and set the buffer fields to point to 4848 * the mapped data buffer. 4849 */ 4850 if (pidx > btoc(MAXPHYS)) 4851 panic("vmapbuf: mapped more than MAXPHYS"); 4852 pmap_qenter((vm_offset_t)bp->b_kvabase, bp->b_xio.xio_pages, pidx); 4853 4854 bp->b_xio.xio_npages = pidx; 4855 bp->b_data = bp->b_kvabase + ((int)(intptr_t)udata & PAGE_MASK); 4856 bp->b_bcount = bytes; 4857 bp->b_bufsize = bytes; 4858 4859 return(0); 4860 } 4861 4862 /* 4863 * vunmapbuf: 4864 * 4865 * Free the io map PTEs associated with this IO operation. 4866 * We also invalidate the TLB entries and restore the original b_addr. 4867 */ 4868 void 4869 vunmapbuf(struct buf *bp) 4870 { 4871 int pidx; 4872 int npages; 4873 4874 KKASSERT(bp->b_flags & B_PAGING); 4875 4876 npages = bp->b_xio.xio_npages; 4877 pmap_qremove(trunc_page((vm_offset_t)bp->b_data), npages); 4878 for (pidx = 0; pidx < npages; ++pidx) { 4879 vm_page_unhold(bp->b_xio.xio_pages[pidx]); 4880 bp->b_xio.xio_pages[pidx] = NULL; 4881 } 4882 bp->b_xio.xio_npages = 0; 4883 bp->b_data = bp->b_kvabase; 4884 } 4885 4886 /* 4887 * Scan all buffers in the system and issue the callback. 4888 */ 4889 int 4890 scan_all_buffers(int (*callback)(struct buf *, void *), void *info) 4891 { 4892 int count = 0; 4893 int error; 4894 long n; 4895 4896 for (n = 0; n < nbuf; ++n) { 4897 if ((error = callback(&buf[n], info)) < 0) { 4898 count = error; 4899 break; 4900 } 4901 count += error; 4902 } 4903 return (count); 4904 } 4905 4906 /* 4907 * nestiobuf_iodone: biodone callback for nested buffers and propagate 4908 * completion to the master buffer. 4909 */ 4910 static void 4911 nestiobuf_iodone(struct bio *bio) 4912 { 4913 struct bio *mbio; 4914 struct buf *mbp, *bp; 4915 struct devstat *stats; 4916 int error; 4917 int donebytes; 4918 4919 bp = bio->bio_buf; 4920 mbio = bio->bio_caller_info1.ptr; 4921 stats = bio->bio_caller_info2.ptr; 4922 mbp = mbio->bio_buf; 4923 4924 KKASSERT(bp->b_bcount <= bp->b_bufsize); 4925 KKASSERT(mbp != bp); 4926 4927 error = bp->b_error; 4928 if (bp->b_error == 0 && 4929 (bp->b_bcount < bp->b_bufsize || bp->b_resid > 0)) { 4930 /* 4931 * Not all got transfered, raise an error. We have no way to 4932 * propagate these conditions to mbp. 4933 */ 4934 error = EIO; 4935 } 4936 4937 donebytes = bp->b_bufsize; 4938 4939 relpbuf(bp, NULL); 4940 4941 nestiobuf_done(mbio, donebytes, error, stats); 4942 } 4943 4944 void 4945 nestiobuf_done(struct bio *mbio, int donebytes, int error, struct devstat *stats) 4946 { 4947 struct buf *mbp; 4948 4949 mbp = mbio->bio_buf; 4950 4951 KKASSERT((int)(intptr_t)mbio->bio_driver_info > 0); 4952 4953 /* 4954 * If an error occured, propagate it to the master buffer. 4955 * 4956 * Several biodone()s may wind up running concurrently so 4957 * use an atomic op to adjust b_flags. 4958 */ 4959 if (error) { 4960 mbp->b_error = error; 4961 atomic_set_int(&mbp->b_flags, B_ERROR); 4962 } 4963 4964 /* 4965 * Decrement the operations in progress counter and terminate the 4966 * I/O if this was the last bit. 4967 */ 4968 if (atomic_fetchadd_int((int *)&mbio->bio_driver_info, -1) == 1) { 4969 mbp->b_resid = 0; 4970 if (stats) 4971 devstat_end_transaction_buf(stats, mbp); 4972 biodone(mbio); 4973 } 4974 } 4975 4976 /* 4977 * Initialize a nestiobuf for use. Set an initial count of 1 to prevent 4978 * the mbio from being biodone()'d while we are still adding sub-bios to 4979 * it. 4980 */ 4981 void 4982 nestiobuf_init(struct bio *bio) 4983 { 4984 bio->bio_driver_info = (void *)1; 4985 } 4986 4987 /* 4988 * The BIOs added to the nestedio have already been started, remove the 4989 * count that placeheld our mbio and biodone() it if the count would 4990 * transition to 0. 4991 */ 4992 void 4993 nestiobuf_start(struct bio *mbio) 4994 { 4995 struct buf *mbp = mbio->bio_buf; 4996 4997 /* 4998 * Decrement the operations in progress counter and terminate the 4999 * I/O if this was the last bit. 5000 */ 5001 if (atomic_fetchadd_int((int *)&mbio->bio_driver_info, -1) == 1) { 5002 if (mbp->b_flags & B_ERROR) 5003 mbp->b_resid = mbp->b_bcount; 5004 else 5005 mbp->b_resid = 0; 5006 biodone(mbio); 5007 } 5008 } 5009 5010 /* 5011 * Set an intermediate error prior to calling nestiobuf_start() 5012 */ 5013 void 5014 nestiobuf_error(struct bio *mbio, int error) 5015 { 5016 struct buf *mbp = mbio->bio_buf; 5017 5018 if (error) { 5019 mbp->b_error = error; 5020 atomic_set_int(&mbp->b_flags, B_ERROR); 5021 } 5022 } 5023 5024 /* 5025 * nestiobuf_add: setup a "nested" buffer. 5026 * 5027 * => 'mbp' is a "master" buffer which is being divided into sub pieces. 5028 * => 'bp' should be a buffer allocated by getiobuf. 5029 * => 'offset' is a byte offset in the master buffer. 5030 * => 'size' is a size in bytes of this nested buffer. 5031 */ 5032 void 5033 nestiobuf_add(struct bio *mbio, struct buf *bp, int offset, size_t size, struct devstat *stats) 5034 { 5035 struct buf *mbp = mbio->bio_buf; 5036 struct vnode *vp = mbp->b_vp; 5037 5038 KKASSERT(mbp->b_bcount >= offset + size); 5039 5040 atomic_add_int((int *)&mbio->bio_driver_info, 1); 5041 5042 /* kernel needs to own the lock for it to be released in biodone */ 5043 BUF_KERNPROC(bp); 5044 bp->b_vp = vp; 5045 bp->b_cmd = mbp->b_cmd; 5046 bp->b_bio1.bio_done = nestiobuf_iodone; 5047 bp->b_data = (char *)mbp->b_data + offset; 5048 bp->b_resid = bp->b_bcount = size; 5049 bp->b_bufsize = bp->b_bcount; 5050 5051 bp->b_bio1.bio_track = NULL; 5052 bp->b_bio1.bio_caller_info1.ptr = mbio; 5053 bp->b_bio1.bio_caller_info2.ptr = stats; 5054 } 5055 5056 #ifdef DDB 5057 5058 DB_SHOW_COMMAND(buffer, db_show_buffer) 5059 { 5060 /* get args */ 5061 struct buf *bp = (struct buf *)addr; 5062 5063 if (!have_addr) { 5064 db_printf("usage: show buffer <addr>\n"); 5065 return; 5066 } 5067 5068 db_printf("b_flags = 0x%b\n", (u_int)bp->b_flags, PRINT_BUF_FLAGS); 5069 db_printf("b_cmd = %d\n", bp->b_cmd); 5070 db_printf("b_error = %d, b_bufsize = %d, b_bcount = %d, " 5071 "b_resid = %d\n, b_data = %p, " 5072 "bio_offset(disk) = %lld, bio_offset(phys) = %lld\n", 5073 bp->b_error, bp->b_bufsize, bp->b_bcount, bp->b_resid, 5074 bp->b_data, 5075 (long long)bp->b_bio2.bio_offset, 5076 (long long)(bp->b_bio2.bio_next ? 5077 bp->b_bio2.bio_next->bio_offset : (off_t)-1)); 5078 if (bp->b_xio.xio_npages) { 5079 int i; 5080 db_printf("b_xio.xio_npages = %d, pages(OBJ, IDX, PA): ", 5081 bp->b_xio.xio_npages); 5082 for (i = 0; i < bp->b_xio.xio_npages; i++) { 5083 vm_page_t m; 5084 m = bp->b_xio.xio_pages[i]; 5085 db_printf("(%p, 0x%lx, 0x%lx)", (void *)m->object, 5086 (u_long)m->pindex, (u_long)VM_PAGE_TO_PHYS(m)); 5087 if ((i + 1) < bp->b_xio.xio_npages) 5088 db_printf(","); 5089 } 5090 db_printf("\n"); 5091 } 5092 } 5093 #endif /* DDB */ 5094