1 /* $NetBSD: vfs_bio.c,v 1.52 1997/07/08 22:03:30 pk 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 <vm/vm.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 77 /* 78 * Insq/Remq for the buffer hash lists. 79 */ 80 #define binshash(bp, dp) LIST_INSERT_HEAD(dp, bp, b_hash) 81 #define bremhash(bp) LIST_REMOVE(bp, b_hash) 82 83 /* 84 * Definitions for the buffer free lists. 85 */ 86 #define BQUEUES 4 /* number of free buffer queues */ 87 88 #define BQ_LOCKED 0 /* super-blocks &c */ 89 #define BQ_LRU 1 /* lru, useful buffers */ 90 #define BQ_AGE 2 /* rubbish */ 91 #define BQ_EMPTY 3 /* buffer headers with no memory */ 92 93 TAILQ_HEAD(bqueues, buf) bufqueues[BQUEUES]; 94 int needbuffer; 95 96 /* 97 * Insq/Remq for the buffer free lists. 98 */ 99 #define binsheadfree(bp, dp) TAILQ_INSERT_HEAD(dp, bp, b_freelist) 100 #define binstailfree(bp, dp) TAILQ_INSERT_TAIL(dp, bp, b_freelist) 101 102 static __inline struct buf *bio_doread __P((struct vnode *, daddr_t, int, 103 struct ucred *, int)); 104 int count_lock_queue __P((void)); 105 106 void 107 bremfree(bp) 108 struct buf *bp; 109 { 110 struct bqueues *dp = NULL; 111 112 /* 113 * We only calculate the head of the freelist when removing 114 * the last element of the list as that is the only time that 115 * it is needed (e.g. to reset the tail pointer). 116 * 117 * NB: This makes an assumption about how tailq's are implemented. 118 */ 119 if (bp->b_freelist.tqe_next == NULL) { 120 for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++) 121 if (dp->tqh_last == &bp->b_freelist.tqe_next) 122 break; 123 if (dp == &bufqueues[BQUEUES]) 124 panic("bremfree: lost tail"); 125 } 126 TAILQ_REMOVE(dp, bp, b_freelist); 127 } 128 129 /* 130 * Initialize buffers and hash links for buffers. 131 */ 132 void 133 bufinit() 134 { 135 register struct buf *bp; 136 struct bqueues *dp; 137 register int i; 138 int base, residual; 139 140 for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++) 141 TAILQ_INIT(dp); 142 bufhashtbl = hashinit(nbuf, M_CACHE, &bufhash); 143 base = bufpages / nbuf; 144 residual = bufpages % nbuf; 145 for (i = 0; i < nbuf; i++) { 146 bp = &buf[i]; 147 bzero((char *)bp, sizeof *bp); 148 bp->b_dev = NODEV; 149 bp->b_rcred = NOCRED; 150 bp->b_wcred = NOCRED; 151 bp->b_vnbufs.le_next = NOLIST; 152 bp->b_data = buffers + i * MAXBSIZE; 153 if (i < residual) 154 bp->b_bufsize = (base + 1) * CLBYTES; 155 else 156 bp->b_bufsize = base * CLBYTES; 157 bp->b_flags = B_INVAL; 158 dp = bp->b_bufsize ? &bufqueues[BQ_AGE] : &bufqueues[BQ_EMPTY]; 159 binsheadfree(bp, dp); 160 binshash(bp, &invalhash); 161 } 162 } 163 164 static __inline struct buf * 165 bio_doread(vp, blkno, size, cred, async) 166 struct vnode *vp; 167 daddr_t blkno; 168 int size; 169 struct ucred *cred; 170 int async; 171 { 172 register struct buf *bp; 173 struct proc *p = (curproc != NULL ? curproc : &proc0); /* XXX */ 174 175 bp = getblk(vp, blkno, size, 0, 0); 176 177 /* 178 * If buffer does not have data valid, start a read. 179 * Note that if buffer is B_INVAL, getblk() won't return it. 180 * Therefore, it's valid if it's I/O has completed or been delayed. 181 */ 182 if (!ISSET(bp->b_flags, (B_DONE | B_DELWRI))) { 183 /* Start I/O for the buffer (keeping credentials). */ 184 SET(bp->b_flags, B_READ | async); 185 if (cred != NOCRED && bp->b_rcred == NOCRED) { 186 crhold(cred); 187 bp->b_rcred = cred; 188 } 189 VOP_STRATEGY(bp); 190 191 /* Pay for the read. */ 192 p->p_stats->p_ru.ru_inblock++; 193 } else if (async) { 194 brelse(bp); 195 } 196 197 return (bp); 198 } 199 200 /* 201 * Read a disk block. 202 * This algorithm described in Bach (p.54). 203 */ 204 int 205 bread(vp, blkno, size, cred, bpp) 206 struct vnode *vp; 207 daddr_t blkno; 208 int size; 209 struct ucred *cred; 210 struct buf **bpp; 211 { 212 register struct buf *bp; 213 214 /* Get buffer for block. */ 215 bp = *bpp = bio_doread(vp, blkno, size, cred, 0); 216 217 /* 218 * Delayed write buffers are found in the cache and have 219 * valid contents. Also, B_ERROR is not set, otherwise 220 * getblk() would not have returned them. 221 */ 222 if (ISSET(bp->b_flags, B_DELWRI)) 223 return (0); 224 225 /* 226 * Otherwise, we had to start a read for it; wait until 227 * it's valid and return the result. 228 */ 229 return (biowait(bp)); 230 } 231 232 /* 233 * Read-ahead multiple disk blocks. The first is sync, the rest async. 234 * Trivial modification to the breada algorithm presented in Bach (p.55). 235 */ 236 int 237 breadn(vp, blkno, size, rablks, rasizes, nrablks, cred, bpp) 238 struct vnode *vp; 239 daddr_t blkno; int size; 240 daddr_t rablks[]; int rasizes[]; 241 int nrablks; 242 struct ucred *cred; 243 struct buf **bpp; 244 { 245 register struct buf *bp; 246 int i; 247 248 bp = *bpp = bio_doread(vp, blkno, size, cred, 0); 249 250 /* 251 * For each of the read-ahead blocks, start a read, if necessary. 252 */ 253 for (i = 0; i < nrablks; i++) { 254 /* If it's in the cache, just go on to next one. */ 255 if (incore(vp, rablks[i])) 256 continue; 257 258 /* Get a buffer for the read-ahead block */ 259 (void) bio_doread(vp, rablks[i], rasizes[i], cred, B_ASYNC); 260 } 261 262 /* 263 * Delayed write buffers are found in the cache and have 264 * valid contents. Also, B_ERROR is not set, otherwise 265 * getblk() would not have returned them. 266 */ 267 if (ISSET(bp->b_flags, B_DELWRI)) 268 SET(bp->b_flags, B_DONE); 269 270 /* 271 * Otherwise, we had to start a read for it; wait until 272 * it's valid and return the result. 273 */ 274 return (biowait(bp)); 275 } 276 277 /* 278 * Read with single-block read-ahead. Defined in Bach (p.55), but 279 * implemented as a call to breadn(). 280 * XXX for compatibility with old file systems. 281 */ 282 int 283 breada(vp, blkno, size, rablkno, rabsize, cred, bpp) 284 struct vnode *vp; 285 daddr_t blkno; int size; 286 daddr_t rablkno; int rabsize; 287 struct ucred *cred; 288 struct buf **bpp; 289 { 290 291 return (breadn(vp, blkno, size, &rablkno, &rabsize, 1, cred, bpp)); 292 } 293 294 /* 295 * Block write. Described in Bach (p.56) 296 */ 297 int 298 bwrite(bp) 299 struct buf *bp; 300 { 301 int rv, sync, wasdelayed, s; 302 struct proc *p = (curproc != NULL ? curproc : &proc0); /* XXX */ 303 304 /* 305 * Remember buffer type, to switch on it later. If the write was 306 * synchronous, but the file system was mounted with MNT_ASYNC, 307 * convert it to a delayed write. 308 * XXX note that this relies on delayed tape writes being converted 309 * to async, not sync writes (which is safe, but ugly). 310 */ 311 sync = !ISSET(bp->b_flags, B_ASYNC); 312 if (sync && bp->b_vp && bp->b_vp->v_mount && 313 ISSET(bp->b_vp->v_mount->mnt_flag, MNT_ASYNC)) { 314 bdwrite(bp); 315 return (0); 316 } 317 318 wasdelayed = ISSET(bp->b_flags, B_DELWRI); 319 CLR(bp->b_flags, (B_READ | B_DONE | B_ERROR | B_DELWRI)); 320 321 s = splbio(); 322 323 /* 324 * Pay for the I/O operation and make sure the buf is on the correct 325 * vnode queue. 326 */ 327 if (wasdelayed) 328 reassignbuf(bp, bp->b_vp); 329 else 330 p->p_stats->p_ru.ru_oublock++; 331 332 /* Initiate disk write. Make sure the appropriate party is charged. */ 333 bp->b_vp->v_numoutput++; 334 splx(s); 335 336 SET(bp->b_flags, B_WRITEINPROG); 337 VOP_STRATEGY(bp); 338 339 if (sync) { 340 /* If I/O was synchronous, wait for it to complete. */ 341 rv = biowait(bp); 342 343 /* Release the buffer. */ 344 brelse(bp); 345 346 return (rv); 347 } else { 348 return (0); 349 } 350 } 351 352 int 353 vn_bwrite(v) 354 void *v; 355 { 356 struct vop_bwrite_args *ap = v; 357 358 return (bwrite(ap->a_bp)); 359 } 360 361 /* 362 * Delayed write. 363 * 364 * The buffer is marked dirty, but is not queued for I/O. 365 * This routine should be used when the buffer is expected 366 * to be modified again soon, typically a small write that 367 * partially fills a buffer. 368 * 369 * NB: magnetic tapes cannot be delayed; they must be 370 * written in the order that the writes are requested. 371 * 372 * Described in Leffler, et al. (pp. 208-213). 373 */ 374 void 375 bdwrite(bp) 376 struct buf *bp; 377 { 378 int s; 379 struct proc *p = (curproc != NULL ? curproc : &proc0); /* XXX */ 380 381 /* If this is a tape block, write the block now. */ 382 /* XXX NOTE: the memory filesystem usurpes major device */ 383 /* XXX number 255, which is a bad idea. */ 384 if (bp->b_dev != NODEV && 385 major(bp->b_dev) != 255 && /* XXX - MFS buffers! */ 386 bdevsw[major(bp->b_dev)].d_type == D_TAPE) { 387 bawrite(bp); 388 return; 389 } 390 391 /* 392 * If the block hasn't been seen before: 393 * (1) Mark it as having been seen, 394 * (2) Charge for the write, 395 * (3) Make sure it's on its vnode's correct block list. 396 */ 397 if (!ISSET(bp->b_flags, B_DELWRI)) { 398 SET(bp->b_flags, B_DELWRI); 399 p->p_stats->p_ru.ru_oublock++; 400 s = splbio(); 401 reassignbuf(bp, bp->b_vp); 402 splx(s); 403 } 404 405 /* Otherwise, the "write" is done, so mark and release the buffer. */ 406 CLR(bp->b_flags, B_NEEDCOMMIT); 407 SET(bp->b_flags, B_DONE); 408 brelse(bp); 409 } 410 411 /* 412 * Asynchronous block write; just an asynchronous bwrite(). 413 */ 414 void 415 bawrite(bp) 416 struct buf *bp; 417 { 418 419 SET(bp->b_flags, B_ASYNC); 420 VOP_BWRITE(bp); 421 } 422 423 /* 424 * Release a buffer on to the free lists. 425 * Described in Bach (p. 46). 426 */ 427 void 428 brelse(bp) 429 struct buf *bp; 430 { 431 struct bqueues *bufq; 432 int s; 433 434 /* Wake up any processes waiting for any buffer to become free. */ 435 if (needbuffer) { 436 needbuffer = 0; 437 wakeup(&needbuffer); 438 } 439 440 /* Wake up any proceeses waiting for _this_ buffer to become free. */ 441 if (ISSET(bp->b_flags, B_WANTED)) { 442 CLR(bp->b_flags, B_WANTED); 443 wakeup(bp); 444 } 445 446 /* Block disk interrupts. */ 447 s = splbio(); 448 449 /* 450 * Determine which queue the buffer should be on, then put it there. 451 */ 452 453 /* If it's locked, don't report an error; try again later. */ 454 if (ISSET(bp->b_flags, (B_LOCKED|B_ERROR)) == (B_LOCKED|B_ERROR)) 455 CLR(bp->b_flags, B_ERROR); 456 457 /* If it's not cacheable, or an error, mark it invalid. */ 458 if (ISSET(bp->b_flags, (B_NOCACHE|B_ERROR))) 459 SET(bp->b_flags, B_INVAL); 460 461 if (ISSET(bp->b_flags, B_VFLUSH)) { 462 /* 463 * This is a delayed write buffer that was just flushed to 464 * disk. It is still on the LRU queue. If it's become 465 * invalid, then we need to move it to a different queue; 466 * otherwise leave it in its current position. 467 */ 468 CLR(bp->b_flags, B_VFLUSH); 469 if (!ISSET(bp->b_flags, B_ERROR|B_INVAL|B_LOCKED|B_AGE)) 470 goto already_queued; 471 else 472 bremfree(bp); 473 } 474 475 if ((bp->b_bufsize <= 0) || ISSET(bp->b_flags, B_INVAL)) { 476 /* 477 * If it's invalid or empty, dissociate it from its vnode 478 * and put on the head of the appropriate queue. 479 */ 480 if (bp->b_vp) 481 brelvp(bp); 482 CLR(bp->b_flags, B_DELWRI); 483 if (bp->b_bufsize <= 0) 484 /* no data */ 485 bufq = &bufqueues[BQ_EMPTY]; 486 else 487 /* invalid data */ 488 bufq = &bufqueues[BQ_AGE]; 489 binsheadfree(bp, bufq); 490 } else { 491 /* 492 * It has valid data. Put it on the end of the appropriate 493 * queue, so that it'll stick around for as long as possible. 494 */ 495 if (ISSET(bp->b_flags, B_LOCKED)) 496 /* locked in core */ 497 bufq = &bufqueues[BQ_LOCKED]; 498 else if (ISSET(bp->b_flags, B_AGE)) 499 /* stale but valid data */ 500 bufq = &bufqueues[BQ_AGE]; 501 else 502 /* valid data */ 503 bufq = &bufqueues[BQ_LRU]; 504 binstailfree(bp, bufq); 505 } 506 507 already_queued: 508 /* Unlock the buffer. */ 509 CLR(bp->b_flags, (B_AGE | B_ASYNC | B_BUSY | B_NOCACHE)); 510 511 /* Allow disk interrupts. */ 512 splx(s); 513 } 514 515 /* 516 * Determine if a block is in the cache. 517 * Just look on what would be its hash chain. If it's there, return 518 * a pointer to it, unless it's marked invalid. If it's marked invalid, 519 * we normally don't return the buffer, unless the caller explicitly 520 * wants us to. 521 */ 522 struct buf * 523 incore(vp, blkno) 524 struct vnode *vp; 525 daddr_t blkno; 526 { 527 struct buf *bp; 528 529 bp = BUFHASH(vp, blkno)->lh_first; 530 531 /* Search hash chain */ 532 for (; bp != NULL; bp = bp->b_hash.le_next) { 533 if (bp->b_lblkno == blkno && bp->b_vp == vp && 534 !ISSET(bp->b_flags, B_INVAL)) 535 return (bp); 536 } 537 538 return (0); 539 } 540 541 /* 542 * Get a block of requested size that is associated with 543 * a given vnode and block offset. If it is found in the 544 * block cache, mark it as having been found, make it busy 545 * and return it. Otherwise, return an empty block of the 546 * correct size. It is up to the caller to insure that the 547 * cached blocks be of the correct size. 548 */ 549 struct buf * 550 getblk(vp, blkno, size, slpflag, slptimeo) 551 register struct vnode *vp; 552 daddr_t blkno; 553 int size, slpflag, slptimeo; 554 { 555 struct bufhashhdr *bh; 556 struct buf *bp; 557 int s, err; 558 559 /* 560 * XXX 561 * The following is an inlined version of 'incore()', but with 562 * the 'invalid' test moved to after the 'busy' test. It's 563 * necessary because there are some cases in which the NFS 564 * code sets B_INVAL prior to writing data to the server, but 565 * in which the buffers actually contain valid data. In this 566 * case, we can't allow the system to allocate a new buffer for 567 * the block until the write is finished. 568 */ 569 bh = BUFHASH(vp, blkno); 570 start: 571 bp = bh->lh_first; 572 for (; bp != NULL; bp = bp->b_hash.le_next) { 573 if (bp->b_lblkno != blkno || bp->b_vp != vp) 574 continue; 575 576 s = splbio(); 577 if (ISSET(bp->b_flags, B_BUSY)) { 578 SET(bp->b_flags, B_WANTED); 579 err = tsleep(bp, slpflag | (PRIBIO + 1), "getblk", 580 slptimeo); 581 splx(s); 582 if (err) 583 return (NULL); 584 goto start; 585 } 586 587 if (!ISSET(bp->b_flags, B_INVAL)) { 588 SET(bp->b_flags, (B_BUSY | B_CACHE)); 589 bremfree(bp); 590 splx(s); 591 break; 592 } 593 splx(s); 594 } 595 596 if (bp == NULL) { 597 if ((bp = getnewbuf(slpflag, slptimeo)) == NULL) 598 goto start; 599 binshash(bp, bh); 600 bp->b_blkno = bp->b_lblkno = blkno; 601 s = splbio(); 602 bgetvp(vp, bp); 603 splx(s); 604 } 605 allocbuf(bp, size); 606 return (bp); 607 } 608 609 /* 610 * Get an empty, disassociated buffer of given size. 611 */ 612 struct buf * 613 geteblk(size) 614 int size; 615 { 616 struct buf *bp; 617 618 while ((bp = getnewbuf(0, 0)) == 0) 619 ; 620 SET(bp->b_flags, B_INVAL); 621 binshash(bp, &invalhash); 622 allocbuf(bp, size); 623 624 return (bp); 625 } 626 627 /* 628 * Expand or contract the actual memory allocated to a buffer. 629 * 630 * If the buffer shrinks, data is lost, so it's up to the 631 * caller to have written it out *first*; this routine will not 632 * start a write. If the buffer grows, it's the callers 633 * responsibility to fill out the buffer's additional contents. 634 */ 635 void 636 allocbuf(bp, size) 637 struct buf *bp; 638 int size; 639 { 640 struct buf *nbp; 641 vm_size_t desired_size; 642 int s; 643 644 desired_size = roundup(size, CLBYTES); 645 if (desired_size > MAXBSIZE) 646 panic("allocbuf: buffer larger than MAXBSIZE requested"); 647 648 if (bp->b_bufsize == desired_size) 649 goto out; 650 651 /* 652 * If the buffer is smaller than the desired size, we need to snarf 653 * it from other buffers. Get buffers (via getnewbuf()), and 654 * steal their pages. 655 */ 656 while (bp->b_bufsize < desired_size) { 657 int amt; 658 659 /* find a buffer */ 660 while ((nbp = getnewbuf(0, 0)) == NULL) 661 ; 662 SET(nbp->b_flags, B_INVAL); 663 binshash(nbp, &invalhash); 664 665 /* and steal its pages, up to the amount we need */ 666 amt = min(nbp->b_bufsize, (desired_size - bp->b_bufsize)); 667 pagemove((nbp->b_data + nbp->b_bufsize - amt), 668 bp->b_data + bp->b_bufsize, amt); 669 bp->b_bufsize += amt; 670 nbp->b_bufsize -= amt; 671 672 /* reduce transfer count if we stole some data */ 673 if (nbp->b_bcount > nbp->b_bufsize) 674 nbp->b_bcount = nbp->b_bufsize; 675 676 #ifdef DIAGNOSTIC 677 if (nbp->b_bufsize < 0) 678 panic("allocbuf: negative bufsize"); 679 #endif 680 681 brelse(nbp); 682 } 683 684 /* 685 * If we want a buffer smaller than the current size, 686 * shrink this buffer. Grab a buf head from the EMPTY queue, 687 * move a page onto it, and put it on front of the AGE queue. 688 * If there are no free buffer headers, leave the buffer alone. 689 */ 690 if (bp->b_bufsize > desired_size) { 691 s = splbio(); 692 if ((nbp = bufqueues[BQ_EMPTY].tqh_first) == NULL) { 693 /* No free buffer head */ 694 splx(s); 695 goto out; 696 } 697 bremfree(nbp); 698 SET(nbp->b_flags, B_BUSY); 699 splx(s); 700 701 /* move the page to it and note this change */ 702 pagemove(bp->b_data + desired_size, 703 nbp->b_data, bp->b_bufsize - desired_size); 704 nbp->b_bufsize = bp->b_bufsize - desired_size; 705 bp->b_bufsize = desired_size; 706 nbp->b_bcount = 0; 707 SET(nbp->b_flags, B_INVAL); 708 709 /* release the newly-filled buffer and leave */ 710 brelse(nbp); 711 } 712 713 out: 714 bp->b_bcount = size; 715 } 716 717 /* 718 * Find a buffer which is available for use. 719 * Select something from a free list. 720 * Preference is to AGE list, then LRU list. 721 */ 722 struct buf * 723 getnewbuf(slpflag, slptimeo) 724 int slpflag, slptimeo; 725 { 726 register struct buf *bp; 727 int s; 728 729 start: 730 s = splbio(); 731 if ((bp = bufqueues[BQ_AGE].tqh_first) != NULL || 732 (bp = bufqueues[BQ_LRU].tqh_first) != NULL) { 733 bremfree(bp); 734 } else { 735 /* wait for a free buffer of any kind */ 736 needbuffer = 1; 737 tsleep(&needbuffer, slpflag|(PRIBIO+1), "getnewbuf", slptimeo); 738 splx(s); 739 return (0); 740 } 741 742 if (ISSET(bp->b_flags, B_VFLUSH)) { 743 /* 744 * This is a delayed write buffer being flushed to disk. Make 745 * sure it gets aged out of the queue when it's finished, and 746 * leave it off the LRU queue. 747 */ 748 CLR(bp->b_flags, B_VFLUSH); 749 SET(bp->b_flags, B_AGE); 750 splx(s); 751 goto start; 752 } 753 754 /* Buffer is no longer on free lists. */ 755 SET(bp->b_flags, B_BUSY); 756 757 /* If buffer was a delayed write, start it, and go back to the top. */ 758 if (ISSET(bp->b_flags, B_DELWRI)) { 759 splx(s); 760 /* 761 * This buffer has gone through the LRU, so make sure it gets 762 * reused ASAP. 763 */ 764 SET(bp->b_flags, B_AGE); 765 bawrite(bp); 766 goto start; 767 } 768 769 /* disassociate us from our vnode, if we had one... */ 770 if (bp->b_vp) 771 brelvp(bp); 772 splx(s); 773 774 /* clear out various other fields */ 775 bp->b_flags = B_BUSY; 776 bp->b_dev = NODEV; 777 bp->b_blkno = bp->b_lblkno = 0; 778 bp->b_iodone = 0; 779 bp->b_error = 0; 780 bp->b_resid = 0; 781 bp->b_bcount = 0; 782 bp->b_dirtyoff = bp->b_dirtyend = 0; 783 bp->b_validoff = bp->b_validend = 0; 784 785 /* nuke any credentials we were holding */ 786 if (bp->b_rcred != NOCRED) { 787 crfree(bp->b_rcred); 788 bp->b_rcred = NOCRED; 789 } 790 if (bp->b_wcred != NOCRED) { 791 crfree(bp->b_wcred); 792 bp->b_wcred = NOCRED; 793 } 794 795 bremhash(bp); 796 return (bp); 797 } 798 799 /* 800 * Wait for operations on the buffer to complete. 801 * When they do, extract and return the I/O's error value. 802 */ 803 int 804 biowait(bp) 805 struct buf *bp; 806 { 807 int s; 808 809 s = splbio(); 810 while (!ISSET(bp->b_flags, B_DONE)) 811 tsleep(bp, PRIBIO + 1, "biowait", 0); 812 splx(s); 813 814 /* check for interruption of I/O (e.g. via NFS), then errors. */ 815 if (ISSET(bp->b_flags, B_EINTR)) { 816 CLR(bp->b_flags, B_EINTR); 817 return (EINTR); 818 } else if (ISSET(bp->b_flags, B_ERROR)) 819 return (bp->b_error ? bp->b_error : EIO); 820 else 821 return (0); 822 } 823 824 /* 825 * Mark I/O complete on a buffer. 826 * 827 * If a callback has been requested, e.g. the pageout 828 * daemon, do so. Otherwise, awaken waiting processes. 829 * 830 * [ Leffler, et al., says on p.247: 831 * "This routine wakes up the blocked process, frees the buffer 832 * for an asynchronous write, or, for a request by the pagedaemon 833 * process, invokes a procedure specified in the buffer structure" ] 834 * 835 * In real life, the pagedaemon (or other system processes) wants 836 * to do async stuff to, and doesn't want the buffer brelse()'d. 837 * (for swap pager, that puts swap buffers on the free lists (!!!), 838 * for the vn device, that puts malloc'd buffers on the free lists!) 839 */ 840 void 841 biodone(bp) 842 struct buf *bp; 843 { 844 if (ISSET(bp->b_flags, B_DONE)) 845 panic("biodone already"); 846 SET(bp->b_flags, B_DONE); /* note that it's done */ 847 848 if (!ISSET(bp->b_flags, B_READ)) /* wake up reader */ 849 vwakeup(bp); 850 851 if (ISSET(bp->b_flags, B_CALL)) { /* if necessary, call out */ 852 CLR(bp->b_flags, B_CALL); /* but note callout done */ 853 (*bp->b_iodone)(bp); 854 } else if (ISSET(bp->b_flags, B_ASYNC)) /* if async, release it */ 855 brelse(bp); 856 else { /* or just wakeup the buffer */ 857 CLR(bp->b_flags, B_WANTED); 858 wakeup(bp); 859 } 860 } 861 862 /* 863 * Return a count of buffers on the "locked" queue. 864 */ 865 int 866 count_lock_queue() 867 { 868 register struct buf *bp; 869 register int n = 0; 870 871 for (bp = bufqueues[BQ_LOCKED].tqh_first; bp; 872 bp = bp->b_freelist.tqe_next) 873 n++; 874 return (n); 875 } 876 877 #ifdef DEBUG 878 /* 879 * Print out statistics on the current allocation of the buffer pool. 880 * Can be enabled to print out on every ``sync'' by setting "syncprt" 881 * in vfs_syscalls.c using sysctl. 882 */ 883 void 884 vfs_bufstats() 885 { 886 int s, i, j, count; 887 register struct buf *bp; 888 register struct bqueues *dp; 889 int counts[MAXBSIZE/CLBYTES+1]; 890 static char *bname[BQUEUES] = { "LOCKED", "LRU", "AGE", "EMPTY" }; 891 892 for (dp = bufqueues, i = 0; dp < &bufqueues[BQUEUES]; dp++, i++) { 893 count = 0; 894 for (j = 0; j <= MAXBSIZE/CLBYTES; j++) 895 counts[j] = 0; 896 s = splbio(); 897 for (bp = dp->tqh_first; bp; bp = bp->b_freelist.tqe_next) { 898 counts[bp->b_bufsize/CLBYTES]++; 899 count++; 900 } 901 splx(s); 902 printf("%s: total-%d", bname[i], count); 903 for (j = 0; j <= MAXBSIZE/CLBYTES; j++) 904 if (counts[j] != 0) 905 printf(", %d-%d", j * CLBYTES, counts[j]); 906 printf("\n"); 907 } 908 } 909 #endif /* DEBUG */ 910