1 /* $NetBSD: vfs_bio.c,v 1.68 2000/06/27 17:41:47 mrg Exp $ */ 2 3 /*- 4 * Copyright (c) 1994 Christopher G. Demetriou 5 * Copyright (c) 1982, 1986, 1989, 1993 6 * The Regents of the University of California. All rights reserved. 7 * (c) UNIX System Laboratories, Inc. 8 * All or some portions of this file are derived from material licensed 9 * to the University of California by American Telephone and Telegraph 10 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 11 * the permission of UNIX System Laboratories, Inc. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * @(#)vfs_bio.c 8.6 (Berkeley) 1/11/94 42 */ 43 44 /* 45 * Some references: 46 * Bach: The Design of the UNIX Operating System (Prentice Hall, 1986) 47 * Leffler, et al.: The Design and Implementation of the 4.3BSD 48 * UNIX Operating System (Addison Welley, 1989) 49 */ 50 51 #include <sys/param.h> 52 #include <sys/systm.h> 53 #include <sys/proc.h> 54 #include <sys/buf.h> 55 #include <sys/vnode.h> 56 #include <sys/mount.h> 57 #include <sys/trace.h> 58 #include <sys/malloc.h> 59 #include <sys/resourcevar.h> 60 #include <sys/conf.h> 61 62 #include <miscfs/specfs/specdev.h> 63 64 /* Macros to clear/set/test flags. */ 65 #define SET(t, f) (t) |= (f) 66 #define CLR(t, f) (t) &= ~(f) 67 #define ISSET(t, f) ((t) & (f)) 68 69 /* 70 * Definitions for the buffer hash lists. 71 */ 72 #define BUFHASH(dvp, lbn) \ 73 (&bufhashtbl[((long)(dvp) / sizeof(*(dvp)) + (int)(lbn)) & bufhash]) 74 LIST_HEAD(bufhashhdr, buf) *bufhashtbl, invalhash; 75 u_long bufhash; 76 struct bio_ops bioops; /* I/O operation notification */ 77 78 /* 79 * Insq/Remq for the buffer hash lists. 80 */ 81 #define binshash(bp, dp) LIST_INSERT_HEAD(dp, bp, b_hash) 82 #define bremhash(bp) LIST_REMOVE(bp, b_hash) 83 84 /* 85 * Definitions for the buffer free lists. 86 */ 87 #define BQUEUES 4 /* number of free buffer queues */ 88 89 #define BQ_LOCKED 0 /* super-blocks &c */ 90 #define BQ_LRU 1 /* lru, useful buffers */ 91 #define BQ_AGE 2 /* rubbish */ 92 #define BQ_EMPTY 3 /* buffer headers with no memory */ 93 94 TAILQ_HEAD(bqueues, buf) bufqueues[BQUEUES]; 95 int needbuffer; 96 97 /* 98 * Buffer pool for I/O buffers. 99 */ 100 struct pool bufpool; 101 102 /* 103 * Insq/Remq for the buffer free lists. 104 */ 105 #define binsheadfree(bp, dp) TAILQ_INSERT_HEAD(dp, bp, b_freelist) 106 #define binstailfree(bp, dp) TAILQ_INSERT_TAIL(dp, bp, b_freelist) 107 108 static __inline struct buf *bio_doread __P((struct vnode *, daddr_t, int, 109 struct ucred *, int)); 110 int count_lock_queue __P((void)); 111 112 void 113 bremfree(bp) 114 struct buf *bp; 115 { 116 int s = splbio(); 117 118 struct bqueues *dp = NULL; 119 120 /* 121 * We only calculate the head of the freelist when removing 122 * the last element of the list as that is the only time that 123 * it is needed (e.g. to reset the tail pointer). 124 * 125 * NB: This makes an assumption about how tailq's are implemented. 126 */ 127 if (bp->b_freelist.tqe_next == NULL) { 128 for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++) 129 if (dp->tqh_last == &bp->b_freelist.tqe_next) 130 break; 131 if (dp == &bufqueues[BQUEUES]) 132 panic("bremfree: lost tail"); 133 } 134 TAILQ_REMOVE(dp, bp, b_freelist); 135 136 splx(s); 137 } 138 139 /* 140 * Initialize buffers and hash links for buffers. 141 */ 142 void 143 bufinit() 144 { 145 struct buf *bp; 146 struct bqueues *dp; 147 int i; 148 int base, residual; 149 150 /* 151 * Initialize the buffer pool. This pool is used for buffers 152 * which are strictly I/O control blocks, not buffer cache 153 * buffers. 154 */ 155 pool_init(&bufpool, sizeof(struct buf), 0, 0, 0, "bufpl", 0, 156 NULL, NULL, M_DEVBUF); 157 158 for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++) 159 TAILQ_INIT(dp); 160 bufhashtbl = hashinit(nbuf, M_CACHE, M_WAITOK, &bufhash); 161 base = bufpages / nbuf; 162 residual = bufpages % nbuf; 163 for (i = 0; i < nbuf; i++) { 164 bp = &buf[i]; 165 memset((char *)bp, 0, sizeof(*bp)); 166 bp->b_dev = NODEV; 167 bp->b_rcred = NOCRED; 168 bp->b_wcred = NOCRED; 169 bp->b_vnbufs.le_next = NOLIST; 170 LIST_INIT(&bp->b_dep); 171 bp->b_data = buffers + i * MAXBSIZE; 172 if (i < residual) 173 bp->b_bufsize = (base + 1) * NBPG; 174 else 175 bp->b_bufsize = base * NBPG; 176 bp->b_flags = B_INVAL; 177 dp = bp->b_bufsize ? &bufqueues[BQ_AGE] : &bufqueues[BQ_EMPTY]; 178 binsheadfree(bp, dp); 179 binshash(bp, &invalhash); 180 } 181 } 182 183 static __inline struct buf * 184 bio_doread(vp, blkno, size, cred, async) 185 struct vnode *vp; 186 daddr_t blkno; 187 int size; 188 struct ucred *cred; 189 int async; 190 { 191 struct buf *bp; 192 struct proc *p = (curproc != NULL ? curproc : &proc0); /* XXX */ 193 194 bp = getblk(vp, blkno, size, 0, 0); 195 196 /* 197 * If buffer does not have data valid, start a read. 198 * Note that if buffer is B_INVAL, getblk() won't return it. 199 * Therefore, it's valid if it's I/O has completed or been delayed. 200 */ 201 if (!ISSET(bp->b_flags, (B_DONE | B_DELWRI))) { 202 /* Start I/O for the buffer (keeping credentials). */ 203 SET(bp->b_flags, B_READ | async); 204 if (cred != NOCRED && bp->b_rcred == NOCRED) { 205 crhold(cred); 206 bp->b_rcred = cred; 207 } 208 VOP_STRATEGY(bp); 209 210 /* Pay for the read. */ 211 p->p_stats->p_ru.ru_inblock++; 212 } else if (async) { 213 brelse(bp); 214 } 215 216 return (bp); 217 } 218 219 /* 220 * Read a disk block. 221 * This algorithm described in Bach (p.54). 222 */ 223 int 224 bread(vp, blkno, size, cred, bpp) 225 struct vnode *vp; 226 daddr_t blkno; 227 int size; 228 struct ucred *cred; 229 struct buf **bpp; 230 { 231 struct buf *bp; 232 233 /* Get buffer for block. */ 234 bp = *bpp = bio_doread(vp, blkno, size, cred, 0); 235 236 /* 237 * Delayed write buffers are found in the cache and have 238 * valid contents. Also, B_ERROR is not set, otherwise 239 * getblk() would not have returned them. 240 */ 241 if (ISSET(bp->b_flags, B_DONE|B_DELWRI)) 242 return (0); 243 244 /* 245 * Otherwise, we had to start a read for it; wait until 246 * it's valid and return the result. 247 */ 248 return (biowait(bp)); 249 } 250 251 /* 252 * Read-ahead multiple disk blocks. The first is sync, the rest async. 253 * Trivial modification to the breada algorithm presented in Bach (p.55). 254 */ 255 int 256 breadn(vp, blkno, size, rablks, rasizes, nrablks, cred, bpp) 257 struct vnode *vp; 258 daddr_t blkno; int size; 259 daddr_t rablks[]; int rasizes[]; 260 int nrablks; 261 struct ucred *cred; 262 struct buf **bpp; 263 { 264 struct buf *bp; 265 int i; 266 267 bp = *bpp = bio_doread(vp, blkno, size, cred, 0); 268 269 /* 270 * For each of the read-ahead blocks, start a read, if necessary. 271 */ 272 for (i = 0; i < nrablks; i++) { 273 /* If it's in the cache, just go on to next one. */ 274 if (incore(vp, rablks[i])) 275 continue; 276 277 /* Get a buffer for the read-ahead block */ 278 (void) bio_doread(vp, rablks[i], rasizes[i], cred, B_ASYNC); 279 } 280 281 /* 282 * Delayed write buffers are found in the cache and have 283 * valid contents. Also, B_ERROR is not set, otherwise 284 * getblk() would not have returned them. 285 */ 286 if (ISSET(bp->b_flags, B_DONE|B_DELWRI)) 287 return (0); 288 289 /* 290 * Otherwise, we had to start a read for it; wait until 291 * it's valid and return the result. 292 */ 293 return (biowait(bp)); 294 } 295 296 /* 297 * Read with single-block read-ahead. Defined in Bach (p.55), but 298 * implemented as a call to breadn(). 299 * XXX for compatibility with old file systems. 300 */ 301 int 302 breada(vp, blkno, size, rablkno, rabsize, cred, bpp) 303 struct vnode *vp; 304 daddr_t blkno; int size; 305 daddr_t rablkno; int rabsize; 306 struct ucred *cred; 307 struct buf **bpp; 308 { 309 310 return (breadn(vp, blkno, size, &rablkno, &rabsize, 1, cred, bpp)); 311 } 312 313 /* 314 * Block write. Described in Bach (p.56) 315 */ 316 int 317 bwrite(bp) 318 struct buf *bp; 319 { 320 int rv, sync, wasdelayed, s; 321 struct proc *p = (curproc != NULL ? curproc : &proc0); /* XXX */ 322 struct vnode *vp; 323 struct mount *mp; 324 325 /* 326 * Remember buffer type, to switch on it later. If the write was 327 * synchronous, but the file system was mounted with MNT_ASYNC, 328 * convert it to a delayed write. 329 * XXX note that this relies on delayed tape writes being converted 330 * to async, not sync writes (which is safe, but ugly). 331 */ 332 sync = !ISSET(bp->b_flags, B_ASYNC); 333 if (sync && bp->b_vp && bp->b_vp->v_mount && 334 ISSET(bp->b_vp->v_mount->mnt_flag, MNT_ASYNC)) { 335 bdwrite(bp); 336 return (0); 337 } 338 339 /* 340 * Collect statistics on synchronous and asynchronous writes. 341 * Writes to block devices are charged to their associated 342 * filesystem (if any). 343 */ 344 if ((vp = bp->b_vp) != NULL) { 345 if (vp->v_type == VBLK) 346 mp = vp->v_specmountpoint; 347 else 348 mp = vp->v_mount; 349 if (mp != NULL) { 350 if (sync) 351 mp->mnt_stat.f_syncwrites++; 352 else 353 mp->mnt_stat.f_asyncwrites++; 354 } 355 } 356 357 wasdelayed = ISSET(bp->b_flags, B_DELWRI); 358 359 s = splbio(); 360 361 CLR(bp->b_flags, (B_READ | B_DONE | B_ERROR | B_DELWRI)); 362 363 /* 364 * Pay for the I/O operation and make sure the buf is on the correct 365 * vnode queue. 366 */ 367 if (wasdelayed) 368 reassignbuf(bp, bp->b_vp); 369 else 370 p->p_stats->p_ru.ru_oublock++; 371 372 /* Initiate disk write. Make sure the appropriate party is charged. */ 373 bp->b_vp->v_numoutput++; 374 splx(s); 375 376 SET(bp->b_flags, B_WRITEINPROG); 377 VOP_STRATEGY(bp); 378 379 if (sync) { 380 /* If I/O was synchronous, wait for it to complete. */ 381 rv = biowait(bp); 382 383 /* Release the buffer. */ 384 brelse(bp); 385 386 return (rv); 387 } else { 388 return (0); 389 } 390 } 391 392 int 393 vn_bwrite(v) 394 void *v; 395 { 396 struct vop_bwrite_args *ap = v; 397 398 return (bwrite(ap->a_bp)); 399 } 400 401 /* 402 * Delayed write. 403 * 404 * The buffer is marked dirty, but is not queued for I/O. 405 * This routine should be used when the buffer is expected 406 * to be modified again soon, typically a small write that 407 * partially fills a buffer. 408 * 409 * NB: magnetic tapes cannot be delayed; they must be 410 * written in the order that the writes are requested. 411 * 412 * Described in Leffler, et al. (pp. 208-213). 413 */ 414 void 415 bdwrite(bp) 416 struct buf *bp; 417 { 418 struct proc *p = (curproc != NULL ? curproc : &proc0); /* XXX */ 419 int s; 420 421 /* If this is a tape block, write the block now. */ 422 /* XXX NOTE: the memory filesystem usurpes major device */ 423 /* XXX number 255, which is a bad idea. */ 424 if (bp->b_dev != NODEV && 425 major(bp->b_dev) != 255 && /* XXX - MFS buffers! */ 426 bdevsw[major(bp->b_dev)].d_type == D_TAPE) { 427 bawrite(bp); 428 return; 429 } 430 431 /* 432 * If the block hasn't been seen before: 433 * (1) Mark it as having been seen, 434 * (2) Charge for the write, 435 * (3) Make sure it's on its vnode's correct block list. 436 */ 437 s = splbio(); 438 439 if (!ISSET(bp->b_flags, B_DELWRI)) { 440 SET(bp->b_flags, B_DELWRI); 441 p->p_stats->p_ru.ru_oublock++; 442 reassignbuf(bp, bp->b_vp); 443 } 444 445 /* Otherwise, the "write" is done, so mark and release the buffer. */ 446 CLR(bp->b_flags, B_NEEDCOMMIT|B_DONE); 447 splx(s); 448 449 brelse(bp); 450 } 451 452 /* 453 * Asynchronous block write; just an asynchronous bwrite(). 454 */ 455 void 456 bawrite(bp) 457 struct buf *bp; 458 { 459 460 SET(bp->b_flags, B_ASYNC); 461 VOP_BWRITE(bp); 462 } 463 464 /* 465 * Ordered block write; asynchronous, but I/O will occur in order queued. 466 */ 467 void 468 bowrite(bp) 469 struct buf *bp; 470 { 471 472 SET(bp->b_flags, B_ASYNC | B_ORDERED); 473 VOP_BWRITE(bp); 474 } 475 476 /* 477 * Same as first half of bdwrite, mark buffer dirty, but do not release it. 478 */ 479 void 480 bdirty(bp) 481 struct buf *bp; 482 { 483 struct proc *p = (curproc != NULL ? curproc : &proc0); /* XXX */ 484 int s; 485 486 s = splbio(); 487 488 CLR(bp->b_flags, B_AGE); 489 490 if (!ISSET(bp->b_flags, B_DELWRI)) { 491 SET(bp->b_flags, B_DELWRI); 492 p->p_stats->p_ru.ru_oublock++; 493 reassignbuf(bp, bp->b_vp); 494 } 495 496 splx(s); 497 } 498 499 /* 500 * Release a buffer on to the free lists. 501 * Described in Bach (p. 46). 502 */ 503 void 504 brelse(bp) 505 struct buf *bp; 506 { 507 struct bqueues *bufq; 508 int s; 509 510 /* Wake up any processes waiting for any buffer to become free. */ 511 if (needbuffer) { 512 needbuffer = 0; 513 wakeup(&needbuffer); 514 } 515 516 /* Block disk interrupts. */ 517 s = splbio(); 518 519 /* Wake up any proceeses waiting for _this_ buffer to become free. */ 520 if (ISSET(bp->b_flags, B_WANTED)) { 521 CLR(bp->b_flags, B_WANTED|B_AGE); 522 wakeup(bp); 523 } 524 525 /* 526 * Determine which queue the buffer should be on, then put it there. 527 */ 528 529 /* If it's locked, don't report an error; try again later. */ 530 if (ISSET(bp->b_flags, (B_LOCKED|B_ERROR)) == (B_LOCKED|B_ERROR)) 531 CLR(bp->b_flags, B_ERROR); 532 533 /* If it's not cacheable, or an error, mark it invalid. */ 534 if (ISSET(bp->b_flags, (B_NOCACHE|B_ERROR))) 535 SET(bp->b_flags, B_INVAL); 536 537 if (ISSET(bp->b_flags, B_VFLUSH)) { 538 /* 539 * This is a delayed write buffer that was just flushed to 540 * disk. It is still on the LRU queue. If it's become 541 * invalid, then we need to move it to a different queue; 542 * otherwise leave it in its current position. 543 */ 544 CLR(bp->b_flags, B_VFLUSH); 545 if (!ISSET(bp->b_flags, B_ERROR|B_INVAL|B_LOCKED|B_AGE)) 546 goto already_queued; 547 else 548 bremfree(bp); 549 } 550 551 if ((bp->b_bufsize <= 0) || ISSET(bp->b_flags, B_INVAL)) { 552 /* 553 * If it's invalid or empty, dissociate it from its vnode 554 * and put on the head of the appropriate queue. 555 */ 556 if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_deallocate) 557 (*bioops.io_deallocate)(bp); 558 CLR(bp->b_flags, B_DONE|B_DELWRI); 559 if (bp->b_vp) { 560 reassignbuf(bp, bp->b_vp); 561 brelvp(bp); 562 } 563 if (bp->b_bufsize <= 0) 564 /* no data */ 565 bufq = &bufqueues[BQ_EMPTY]; 566 else 567 /* invalid data */ 568 bufq = &bufqueues[BQ_AGE]; 569 binsheadfree(bp, bufq); 570 } else { 571 /* 572 * It has valid data. Put it on the end of the appropriate 573 * queue, so that it'll stick around for as long as possible. 574 * If buf is AGE, but has dependencies, must put it on last 575 * bufqueue to be scanned, ie LRU. This protects against the 576 * livelock where BQ_AGE only has buffers with dependencies, 577 * and we thus never get to the dependent buffers in BQ_LRU. 578 */ 579 if (ISSET(bp->b_flags, B_LOCKED)) 580 /* locked in core */ 581 bufq = &bufqueues[BQ_LOCKED]; 582 else if (!ISSET(bp->b_flags, B_AGE)) 583 /* valid data */ 584 bufq = &bufqueues[BQ_LRU]; 585 else { 586 /* stale but valid data */ 587 int has_deps; 588 589 if (LIST_FIRST(&bp->b_dep) != NULL && 590 bioops.io_countdeps) 591 has_deps = (*bioops.io_countdeps)(bp, 0); 592 else 593 has_deps = 0; 594 bufq = has_deps ? &bufqueues[BQ_LRU] : 595 &bufqueues[BQ_AGE]; 596 } 597 binstailfree(bp, bufq); 598 } 599 600 already_queued: 601 /* Unlock the buffer. */ 602 CLR(bp->b_flags, B_AGE|B_ASYNC|B_BUSY|B_NOCACHE|B_ORDERED); 603 604 /* Allow disk interrupts. */ 605 splx(s); 606 } 607 608 /* 609 * Determine if a block is in the cache. 610 * Just look on what would be its hash chain. If it's there, return 611 * a pointer to it, unless it's marked invalid. If it's marked invalid, 612 * we normally don't return the buffer, unless the caller explicitly 613 * wants us to. 614 */ 615 struct buf * 616 incore(vp, blkno) 617 struct vnode *vp; 618 daddr_t blkno; 619 { 620 struct buf *bp; 621 622 bp = BUFHASH(vp, blkno)->lh_first; 623 624 /* Search hash chain */ 625 for (; bp != NULL; bp = bp->b_hash.le_next) { 626 if (bp->b_lblkno == blkno && bp->b_vp == vp && 627 !ISSET(bp->b_flags, B_INVAL)) 628 return (bp); 629 } 630 631 return (0); 632 } 633 634 /* 635 * Get a block of requested size that is associated with 636 * a given vnode and block offset. If it is found in the 637 * block cache, mark it as having been found, make it busy 638 * and return it. Otherwise, return an empty block of the 639 * correct size. It is up to the caller to insure that the 640 * cached blocks be of the correct size. 641 */ 642 struct buf * 643 getblk(vp, blkno, size, slpflag, slptimeo) 644 struct vnode *vp; 645 daddr_t blkno; 646 int size, slpflag, slptimeo; 647 { 648 struct bufhashhdr *bh; 649 struct buf *bp; 650 int s, err; 651 652 /* 653 * XXX 654 * The following is an inlined version of 'incore()', but with 655 * the 'invalid' test moved to after the 'busy' test. It's 656 * necessary because there are some cases in which the NFS 657 * code sets B_INVAL prior to writing data to the server, but 658 * in which the buffers actually contain valid data. In this 659 * case, we can't allow the system to allocate a new buffer for 660 * the block until the write is finished. 661 */ 662 bh = BUFHASH(vp, blkno); 663 start: 664 bp = bh->lh_first; 665 for (; bp != NULL; bp = bp->b_hash.le_next) { 666 if (bp->b_lblkno != blkno || bp->b_vp != vp) 667 continue; 668 669 s = splbio(); 670 if (ISSET(bp->b_flags, B_BUSY)) { 671 SET(bp->b_flags, B_WANTED); 672 err = tsleep(bp, slpflag | (PRIBIO + 1), "getblk", 673 slptimeo); 674 splx(s); 675 if (err) 676 return (NULL); 677 goto start; 678 } 679 680 if (!ISSET(bp->b_flags, B_INVAL)) { 681 #ifdef DIAGNOSTIC 682 if (ISSET(bp->b_flags, B_DONE|B_DELWRI) && 683 bp->b_bcount < size) 684 panic("getblk: block size invariant failed"); 685 #endif 686 SET(bp->b_flags, B_BUSY); 687 bremfree(bp); 688 splx(s); 689 break; 690 } 691 splx(s); 692 } 693 694 if (bp == NULL) { 695 if ((bp = getnewbuf(slpflag, slptimeo)) == NULL) 696 goto start; 697 binshash(bp, bh); 698 bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = blkno; 699 s = splbio(); 700 bgetvp(vp, bp); 701 splx(s); 702 } 703 allocbuf(bp, size); 704 return (bp); 705 } 706 707 /* 708 * Get an empty, disassociated buffer of given size. 709 */ 710 struct buf * 711 geteblk(size) 712 int size; 713 { 714 struct buf *bp; 715 716 while ((bp = getnewbuf(0, 0)) == 0) 717 ; 718 SET(bp->b_flags, B_INVAL); 719 binshash(bp, &invalhash); 720 allocbuf(bp, size); 721 722 return (bp); 723 } 724 725 /* 726 * Expand or contract the actual memory allocated to a buffer. 727 * 728 * If the buffer shrinks, data is lost, so it's up to the 729 * caller to have written it out *first*; this routine will not 730 * start a write. If the buffer grows, it's the callers 731 * responsibility to fill out the buffer's additional contents. 732 */ 733 void 734 allocbuf(bp, size) 735 struct buf *bp; 736 int size; 737 { 738 struct buf *nbp; 739 vsize_t desired_size; 740 int s; 741 742 desired_size = roundup(size, NBPG); 743 if (desired_size > MAXBSIZE) 744 panic("allocbuf: buffer larger than MAXBSIZE requested"); 745 746 if (bp->b_bufsize == desired_size) 747 goto out; 748 749 /* 750 * If the buffer is smaller than the desired size, we need to snarf 751 * it from other buffers. Get buffers (via getnewbuf()), and 752 * steal their pages. 753 */ 754 while (bp->b_bufsize < desired_size) { 755 int amt; 756 757 /* find a buffer */ 758 while ((nbp = getnewbuf(0, 0)) == NULL) 759 ; 760 SET(nbp->b_flags, B_INVAL); 761 binshash(nbp, &invalhash); 762 763 /* and steal its pages, up to the amount we need */ 764 amt = min(nbp->b_bufsize, (desired_size - bp->b_bufsize)); 765 pagemove((nbp->b_data + nbp->b_bufsize - amt), 766 bp->b_data + bp->b_bufsize, amt); 767 bp->b_bufsize += amt; 768 nbp->b_bufsize -= amt; 769 770 /* reduce transfer count if we stole some data */ 771 if (nbp->b_bcount > nbp->b_bufsize) 772 nbp->b_bcount = nbp->b_bufsize; 773 774 #ifdef DIAGNOSTIC 775 if (nbp->b_bufsize < 0) 776 panic("allocbuf: negative bufsize"); 777 #endif 778 779 brelse(nbp); 780 } 781 782 /* 783 * If we want a buffer smaller than the current size, 784 * shrink this buffer. Grab a buf head from the EMPTY queue, 785 * move a page onto it, and put it on front of the AGE queue. 786 * If there are no free buffer headers, leave the buffer alone. 787 */ 788 if (bp->b_bufsize > desired_size) { 789 s = splbio(); 790 if ((nbp = bufqueues[BQ_EMPTY].tqh_first) == NULL) { 791 /* No free buffer head */ 792 splx(s); 793 goto out; 794 } 795 bremfree(nbp); 796 SET(nbp->b_flags, B_BUSY); 797 splx(s); 798 799 /* move the page to it and note this change */ 800 pagemove(bp->b_data + desired_size, 801 nbp->b_data, bp->b_bufsize - desired_size); 802 nbp->b_bufsize = bp->b_bufsize - desired_size; 803 bp->b_bufsize = desired_size; 804 nbp->b_bcount = 0; 805 SET(nbp->b_flags, B_INVAL); 806 807 /* release the newly-filled buffer and leave */ 808 brelse(nbp); 809 } 810 811 out: 812 bp->b_bcount = size; 813 } 814 815 /* 816 * Find a buffer which is available for use. 817 * Select something from a free list. 818 * Preference is to AGE list, then LRU list. 819 */ 820 struct buf * 821 getnewbuf(slpflag, slptimeo) 822 int slpflag, slptimeo; 823 { 824 struct buf *bp; 825 int s; 826 827 start: 828 s = splbio(); 829 if ((bp = bufqueues[BQ_AGE].tqh_first) != NULL || 830 (bp = bufqueues[BQ_LRU].tqh_first) != NULL) { 831 bremfree(bp); 832 } else { 833 /* wait for a free buffer of any kind */ 834 needbuffer = 1; 835 tsleep(&needbuffer, slpflag|(PRIBIO+1), "getnewbuf", slptimeo); 836 splx(s); 837 return (0); 838 } 839 840 if (ISSET(bp->b_flags, B_VFLUSH)) { 841 /* 842 * This is a delayed write buffer being flushed to disk. Make 843 * sure it gets aged out of the queue when it's finished, and 844 * leave it off the LRU queue. 845 */ 846 CLR(bp->b_flags, B_VFLUSH); 847 SET(bp->b_flags, B_AGE); 848 splx(s); 849 goto start; 850 } 851 852 /* Buffer is no longer on free lists. */ 853 SET(bp->b_flags, B_BUSY); 854 855 /* If buffer was a delayed write, start it, and go back to the top. */ 856 if (ISSET(bp->b_flags, B_DELWRI)) { 857 splx(s); 858 /* 859 * This buffer has gone through the LRU, so make sure it gets 860 * reused ASAP. 861 */ 862 SET(bp->b_flags, B_AGE); 863 bawrite(bp); 864 goto start; 865 } 866 867 /* disassociate us from our vnode, if we had one... */ 868 if (bp->b_vp) 869 brelvp(bp); 870 splx(s); 871 872 if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_deallocate) 873 (*bioops.io_deallocate)(bp); 874 875 /* clear out various other fields */ 876 bp->b_flags = B_BUSY; 877 bp->b_dev = NODEV; 878 bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = 0; 879 bp->b_iodone = 0; 880 bp->b_error = 0; 881 bp->b_resid = 0; 882 bp->b_bcount = 0; 883 bp->b_dirtyoff = bp->b_dirtyend = 0; 884 bp->b_validoff = bp->b_validend = 0; 885 886 /* nuke any credentials we were holding */ 887 if (bp->b_rcred != NOCRED) { 888 crfree(bp->b_rcred); 889 bp->b_rcred = NOCRED; 890 } 891 if (bp->b_wcred != NOCRED) { 892 crfree(bp->b_wcred); 893 bp->b_wcred = NOCRED; 894 } 895 896 bremhash(bp); 897 return (bp); 898 } 899 900 /* 901 * Wait for operations on the buffer to complete. 902 * When they do, extract and return the I/O's error value. 903 */ 904 int 905 biowait(bp) 906 struct buf *bp; 907 { 908 int s; 909 910 s = splbio(); 911 while (!ISSET(bp->b_flags, B_DONE)) 912 tsleep(bp, PRIBIO + 1, "biowait", 0); 913 splx(s); 914 915 /* check for interruption of I/O (e.g. via NFS), then errors. */ 916 if (ISSET(bp->b_flags, B_EINTR)) { 917 CLR(bp->b_flags, B_EINTR); 918 return (EINTR); 919 } else if (ISSET(bp->b_flags, B_ERROR)) 920 return (bp->b_error ? bp->b_error : EIO); 921 else 922 return (0); 923 } 924 925 /* 926 * Mark I/O complete on a buffer. 927 * 928 * If a callback has been requested, e.g. the pageout 929 * daemon, do so. Otherwise, awaken waiting processes. 930 * 931 * [ Leffler, et al., says on p.247: 932 * "This routine wakes up the blocked process, frees the buffer 933 * for an asynchronous write, or, for a request by the pagedaemon 934 * process, invokes a procedure specified in the buffer structure" ] 935 * 936 * In real life, the pagedaemon (or other system processes) wants 937 * to do async stuff to, and doesn't want the buffer brelse()'d. 938 * (for swap pager, that puts swap buffers on the free lists (!!!), 939 * for the vn device, that puts malloc'd buffers on the free lists!) 940 */ 941 void 942 biodone(bp) 943 struct buf *bp; 944 { 945 int s = splbio(); 946 947 if (ISSET(bp->b_flags, B_DONE)) 948 panic("biodone already"); 949 SET(bp->b_flags, B_DONE); /* note that it's done */ 950 951 if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_complete) 952 (*bioops.io_complete)(bp); 953 954 if (!ISSET(bp->b_flags, B_READ)) /* wake up reader */ 955 vwakeup(bp); 956 957 if (ISSET(bp->b_flags, B_CALL)) { /* if necessary, call out */ 958 CLR(bp->b_flags, B_CALL); /* but note callout done */ 959 (*bp->b_iodone)(bp); 960 } else { 961 if (ISSET(bp->b_flags, B_ASYNC)) /* if async, release */ 962 brelse(bp); 963 else { /* or just wakeup the buffer */ 964 CLR(bp->b_flags, B_WANTED); 965 wakeup(bp); 966 } 967 } 968 969 splx(s); 970 } 971 972 /* 973 * Return a count of buffers on the "locked" queue. 974 */ 975 int 976 count_lock_queue() 977 { 978 struct buf *bp; 979 int n = 0; 980 981 for (bp = bufqueues[BQ_LOCKED].tqh_first; bp; 982 bp = bp->b_freelist.tqe_next) 983 n++; 984 return (n); 985 } 986 987 #ifdef DEBUG 988 /* 989 * Print out statistics on the current allocation of the buffer pool. 990 * Can be enabled to print out on every ``sync'' by setting "syncprt" 991 * in vfs_syscalls.c using sysctl. 992 */ 993 void 994 vfs_bufstats() 995 { 996 int s, i, j, count; 997 struct buf *bp; 998 struct bqueues *dp; 999 int counts[MAXBSIZE/NBPG+1]; 1000 static char *bname[BQUEUES] = { "LOCKED", "LRU", "AGE", "EMPTY" }; 1001 1002 for (dp = bufqueues, i = 0; dp < &bufqueues[BQUEUES]; dp++, i++) { 1003 count = 0; 1004 for (j = 0; j <= MAXBSIZE/NBPG; j++) 1005 counts[j] = 0; 1006 s = splbio(); 1007 for (bp = dp->tqh_first; bp; bp = bp->b_freelist.tqe_next) { 1008 counts[bp->b_bufsize/NBPG]++; 1009 count++; 1010 } 1011 splx(s); 1012 printf("%s: total-%d", bname[i], count); 1013 for (j = 0; j <= MAXBSIZE/NBPG; j++) 1014 if (counts[j] != 0) 1015 printf(", %d-%d", j * NBPG, counts[j]); 1016 printf("\n"); 1017 } 1018 } 1019 #endif /* DEBUG */ 1020