Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/kern/vfs_bio.c
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1 /* $NetBSD: vfs_bio.c,v 1.303 2022/03/30 14:54:29 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2007, 2008, 2009, 2019, 2020 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Andrew Doran, and by Wasabi Systems, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /*- 33 * Copyright (c) 1982, 1986, 1989, 1993 34 * The Regents of the University of California. All rights reserved. 35 * (c) UNIX System Laboratories, Inc. 36 * All or some portions of this file are derived from material licensed 37 * to the University of California by American Telephone and Telegraph 38 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 39 * the permission of UNIX System Laboratories, Inc. 40 * 41 * Redistribution and use in source and binary forms, with or without 42 * modification, are permitted provided that the following conditions 43 * are met: 44 * 1. Redistributions of source code must retain the above copyright 45 * notice, this list of conditions and the following disclaimer. 46 * 2. Redistributions in binary form must reproduce the above copyright 47 * notice, this list of conditions and the following disclaimer in the 48 * documentation and/or other materials provided with the distribution. 49 * 3. Neither the name of the University nor the names of its contributors 50 * may be used to endorse or promote products derived from this software 51 * without specific prior written permission. 52 * 53 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 54 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 55 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 56 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 57 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 58 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 59 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 60 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 61 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 62 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 63 * SUCH DAMAGE. 64 * 65 * @(#)vfs_bio.c 8.6 (Berkeley) 1/11/94 66 */ 67 68 /*- 69 * Copyright (c) 1994 Christopher G. Demetriou 70 * 71 * Redistribution and use in source and binary forms, with or without 72 * modification, are permitted provided that the following conditions 73 * are met: 74 * 1. Redistributions of source code must retain the above copyright 75 * notice, this list of conditions and the following disclaimer. 76 * 2. Redistributions in binary form must reproduce the above copyright 77 * notice, this list of conditions and the following disclaimer in the 78 * documentation and/or other materials provided with the distribution. 79 * 3. All advertising materials mentioning features or use of this software 80 * must display the following acknowledgement: 81 * This product includes software developed by the University of 82 * California, Berkeley and its contributors. 83 * 4. Neither the name of the University nor the names of its contributors 84 * may be used to endorse or promote products derived from this software 85 * without specific prior written permission. 86 * 87 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 88 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 89 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 90 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 91 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 92 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 93 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 94 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 95 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 96 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 97 * SUCH DAMAGE. 98 * 99 * @(#)vfs_bio.c 8.6 (Berkeley) 1/11/94 100 */ 101 102 /* 103 * The buffer cache subsystem. 104 * 105 * Some references: 106 * Bach: The Design of the UNIX Operating System (Prentice Hall, 1986) 107 * Leffler, et al.: The Design and Implementation of the 4.3BSD 108 * UNIX Operating System (Addison Welley, 1989) 109 * 110 * Locking 111 * 112 * There are three locks: 113 * - bufcache_lock: protects global buffer cache state. 114 * - BC_BUSY: a long term per-buffer lock. 115 * - buf_t::b_objlock: lock on completion (biowait vs biodone). 116 * 117 * For buffers associated with vnodes (a most common case) b_objlock points 118 * to the vnode_t::v_interlock. Otherwise, it points to generic buffer_lock. 119 * 120 * Lock order: 121 * bufcache_lock -> 122 * buf_t::b_objlock 123 */ 124 125 #include <sys/cdefs.h> 126 __KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.303 2022/03/30 14:54:29 riastradh Exp $"); 127 128 #ifdef _KERNEL_OPT 129 #include "opt_bufcache.h" 130 #include "opt_dtrace.h" 131 #include "opt_biohist.h" 132 #endif 133 134 #include <sys/param.h> 135 #include <sys/systm.h> 136 #include <sys/kernel.h> 137 #include <sys/proc.h> 138 #include <sys/buf.h> 139 #include <sys/vnode.h> 140 #include <sys/mount.h> 141 #include <sys/resourcevar.h> 142 #include <sys/sysctl.h> 143 #include <sys/conf.h> 144 #include <sys/kauth.h> 145 #include <sys/fstrans.h> 146 #include <sys/intr.h> 147 #include <sys/cpu.h> 148 #include <sys/wapbl.h> 149 #include <sys/bitops.h> 150 #include <sys/cprng.h> 151 #include <sys/sdt.h> 152 153 #include <uvm/uvm.h> /* extern struct uvm uvm */ 154 155 #include <miscfs/specfs/specdev.h> 156 157 SDT_PROVIDER_DEFINE(io); 158 159 SDT_PROBE_DEFINE4(io, kernel, , bbusy__start, 160 "struct buf *"/*bp*/, 161 "bool"/*intr*/, "int"/*timo*/, "kmutex_t *"/*interlock*/); 162 SDT_PROBE_DEFINE5(io, kernel, , bbusy__done, 163 "struct buf *"/*bp*/, 164 "bool"/*intr*/, 165 "int"/*timo*/, 166 "kmutex_t *"/*interlock*/, 167 "int"/*error*/); 168 SDT_PROBE_DEFINE0(io, kernel, , getnewbuf__start); 169 SDT_PROBE_DEFINE1(io, kernel, , getnewbuf__done, "struct buf *"/*bp*/); 170 SDT_PROBE_DEFINE3(io, kernel, , getblk__start, 171 "struct vnode *"/*vp*/, "daddr_t"/*blkno*/, "int"/*size*/); 172 SDT_PROBE_DEFINE4(io, kernel, , getblk__done, 173 "struct vnode *"/*vp*/, "daddr_t"/*blkno*/, "int"/*size*/, 174 "struct buf *"/*bp*/); 175 SDT_PROBE_DEFINE2(io, kernel, , brelse, "struct buf *"/*bp*/, "int"/*set*/); 176 SDT_PROBE_DEFINE1(io, kernel, , wait__start, "struct buf *"/*bp*/); 177 SDT_PROBE_DEFINE1(io, kernel, , wait__done, "struct buf *"/*bp*/); 178 179 #ifndef BUFPAGES 180 # define BUFPAGES 0 181 #endif 182 183 #ifdef BUFCACHE 184 # if (BUFCACHE < 5) || (BUFCACHE > 95) 185 # error BUFCACHE is not between 5 and 95 186 # endif 187 #else 188 # define BUFCACHE 15 189 #endif 190 191 u_int nbuf; /* desired number of buffer headers */ 192 u_int bufpages = BUFPAGES; /* optional hardwired count */ 193 u_int bufcache = BUFCACHE; /* max % of RAM to use for buffer cache */ 194 195 /* 196 * Definitions for the buffer free lists. 197 */ 198 #define BQUEUES 3 /* number of free buffer queues */ 199 200 #define BQ_LOCKED 0 /* super-blocks &c */ 201 #define BQ_LRU 1 /* lru, useful buffers */ 202 #define BQ_AGE 2 /* rubbish */ 203 204 struct bqueue { 205 TAILQ_HEAD(, buf) bq_queue; 206 uint64_t bq_bytes; 207 buf_t *bq_marker; 208 }; 209 static struct bqueue bufqueues[BQUEUES] __cacheline_aligned; 210 211 /* Function prototypes */ 212 static void buf_setwm(void); 213 static int buf_trim(void); 214 static void *bufpool_page_alloc(struct pool *, int); 215 static void bufpool_page_free(struct pool *, void *); 216 static buf_t *bio_doread(struct vnode *, daddr_t, int, int); 217 static buf_t *getnewbuf(int, int, int); 218 static int buf_lotsfree(void); 219 static int buf_canrelease(void); 220 static u_long buf_mempoolidx(u_long); 221 static u_long buf_roundsize(u_long); 222 static void *buf_alloc(size_t); 223 static void buf_mrelease(void *, size_t); 224 static void binsheadfree(buf_t *, struct bqueue *); 225 static void binstailfree(buf_t *, struct bqueue *); 226 #ifdef DEBUG 227 static int checkfreelist(buf_t *, struct bqueue *, int); 228 #endif 229 static void biointr(void *); 230 static void biodone2(buf_t *); 231 static void sysctl_kern_buf_setup(void); 232 static void sysctl_vm_buf_setup(void); 233 234 /* Initialization for biohist */ 235 236 #include <sys/biohist.h> 237 238 BIOHIST_DEFINE(biohist); 239 240 void 241 biohist_init(void) 242 { 243 244 BIOHIST_INIT(biohist, BIOHIST_SIZE); 245 } 246 247 /* 248 * Definitions for the buffer hash lists. 249 */ 250 #define BUFHASH(dvp, lbn) \ 251 (&bufhashtbl[(((long)(dvp) >> 8) + (int)(lbn)) & bufhash]) 252 LIST_HEAD(bufhashhdr, buf) *bufhashtbl, invalhash; 253 u_long bufhash; 254 255 static int bufhash_stats(struct hashstat_sysctl *, bool); 256 257 static kcondvar_t needbuffer_cv; 258 259 /* 260 * Buffer queue lock. 261 */ 262 kmutex_t bufcache_lock __cacheline_aligned; 263 kmutex_t buffer_lock __cacheline_aligned; 264 265 /* Software ISR for completed transfers. */ 266 static void *biodone_sih; 267 268 /* Buffer pool for I/O buffers. */ 269 static pool_cache_t buf_cache; 270 static pool_cache_t bufio_cache; 271 272 #define MEMPOOL_INDEX_OFFSET (ilog2(DEV_BSIZE)) /* smallest pool is 512 bytes */ 273 #define NMEMPOOLS (ilog2(MAXBSIZE) - MEMPOOL_INDEX_OFFSET + 1) 274 __CTASSERT((1 << (NMEMPOOLS + MEMPOOL_INDEX_OFFSET - 1)) == MAXBSIZE); 275 276 /* Buffer memory pools */ 277 static struct pool bmempools[NMEMPOOLS]; 278 279 static struct vm_map *buf_map; 280 281 /* 282 * Buffer memory pool allocator. 283 */ 284 static void * 285 bufpool_page_alloc(struct pool *pp, int flags) 286 { 287 288 return (void *)uvm_km_alloc(buf_map, 289 MAXBSIZE, MAXBSIZE, 290 ((flags & PR_WAITOK) ? 0 : UVM_KMF_NOWAIT|UVM_KMF_TRYLOCK) 291 | UVM_KMF_WIRED); 292 } 293 294 static void 295 bufpool_page_free(struct pool *pp, void *v) 296 { 297 298 uvm_km_free(buf_map, (vaddr_t)v, MAXBSIZE, UVM_KMF_WIRED); 299 } 300 301 static struct pool_allocator bufmempool_allocator = { 302 .pa_alloc = bufpool_page_alloc, 303 .pa_free = bufpool_page_free, 304 .pa_pagesz = MAXBSIZE, 305 }; 306 307 /* Buffer memory management variables */ 308 u_long bufmem_valimit; 309 u_long bufmem_hiwater; 310 u_long bufmem_lowater; 311 u_long bufmem; 312 313 /* 314 * MD code can call this to set a hard limit on the amount 315 * of virtual memory used by the buffer cache. 316 */ 317 int 318 buf_setvalimit(vsize_t sz) 319 { 320 321 /* We need to accommodate at least NMEMPOOLS of MAXBSIZE each */ 322 if (sz < NMEMPOOLS * MAXBSIZE) 323 return EINVAL; 324 325 bufmem_valimit = sz; 326 return 0; 327 } 328 329 static void 330 buf_setwm(void) 331 { 332 333 bufmem_hiwater = buf_memcalc(); 334 /* lowater is approx. 2% of memory (with bufcache = 15) */ 335 #define BUFMEM_WMSHIFT 3 336 #define BUFMEM_HIWMMIN (64 * 1024 << BUFMEM_WMSHIFT) 337 if (bufmem_hiwater < BUFMEM_HIWMMIN) 338 /* Ensure a reasonable minimum value */ 339 bufmem_hiwater = BUFMEM_HIWMMIN; 340 bufmem_lowater = bufmem_hiwater >> BUFMEM_WMSHIFT; 341 } 342 343 #ifdef DEBUG 344 int debug_verify_freelist = 0; 345 static int 346 checkfreelist(buf_t *bp, struct bqueue *dp, int ison) 347 { 348 buf_t *b; 349 350 if (!debug_verify_freelist) 351 return 1; 352 353 TAILQ_FOREACH(b, &dp->bq_queue, b_freelist) { 354 if (b == bp) 355 return ison ? 1 : 0; 356 } 357 358 return ison ? 0 : 1; 359 } 360 #endif 361 362 /* 363 * Insq/Remq for the buffer hash lists. 364 * Call with buffer queue locked. 365 */ 366 static void 367 binsheadfree(buf_t *bp, struct bqueue *dp) 368 { 369 370 KASSERT(mutex_owned(&bufcache_lock)); 371 KASSERT(bp->b_freelistindex == -1); 372 TAILQ_INSERT_HEAD(&dp->bq_queue, bp, b_freelist); 373 dp->bq_bytes += bp->b_bufsize; 374 bp->b_freelistindex = dp - bufqueues; 375 } 376 377 static void 378 binstailfree(buf_t *bp, struct bqueue *dp) 379 { 380 381 KASSERT(mutex_owned(&bufcache_lock)); 382 KASSERTMSG(bp->b_freelistindex == -1, "double free of buffer? " 383 "bp=%p, b_freelistindex=%d\n", bp, bp->b_freelistindex); 384 TAILQ_INSERT_TAIL(&dp->bq_queue, bp, b_freelist); 385 dp->bq_bytes += bp->b_bufsize; 386 bp->b_freelistindex = dp - bufqueues; 387 } 388 389 void 390 bremfree(buf_t *bp) 391 { 392 struct bqueue *dp; 393 int bqidx = bp->b_freelistindex; 394 395 KASSERT(mutex_owned(&bufcache_lock)); 396 397 KASSERT(bqidx != -1); 398 dp = &bufqueues[bqidx]; 399 KDASSERT(checkfreelist(bp, dp, 1)); 400 KASSERT(dp->bq_bytes >= bp->b_bufsize); 401 TAILQ_REMOVE(&dp->bq_queue, bp, b_freelist); 402 dp->bq_bytes -= bp->b_bufsize; 403 404 /* For the sysctl helper. */ 405 if (bp == dp->bq_marker) 406 dp->bq_marker = NULL; 407 408 #if defined(DIAGNOSTIC) 409 bp->b_freelistindex = -1; 410 #endif /* defined(DIAGNOSTIC) */ 411 } 412 413 /* 414 * note that for some ports this is used by pmap bootstrap code to 415 * determine kva size. 416 */ 417 u_long 418 buf_memcalc(void) 419 { 420 u_long n; 421 vsize_t mapsz = 0; 422 423 /* 424 * Determine the upper bound of memory to use for buffers. 425 * 426 * - If bufpages is specified, use that as the number 427 * pages. 428 * 429 * - Otherwise, use bufcache as the percentage of 430 * physical memory. 431 */ 432 if (bufpages != 0) { 433 n = bufpages; 434 } else { 435 if (bufcache < 5) { 436 printf("forcing bufcache %d -> 5", bufcache); 437 bufcache = 5; 438 } 439 if (bufcache > 95) { 440 printf("forcing bufcache %d -> 95", bufcache); 441 bufcache = 95; 442 } 443 if (buf_map != NULL) 444 mapsz = vm_map_max(buf_map) - vm_map_min(buf_map); 445 n = calc_cache_size(mapsz, bufcache, 446 (buf_map != kernel_map) ? 100 : BUFCACHE_VA_MAXPCT) 447 / PAGE_SIZE; 448 } 449 450 n <<= PAGE_SHIFT; 451 if (bufmem_valimit != 0 && n > bufmem_valimit) 452 n = bufmem_valimit; 453 454 return (n); 455 } 456 457 /* 458 * Initialize buffers and hash links for buffers. 459 */ 460 void 461 bufinit(void) 462 { 463 struct bqueue *dp; 464 int use_std; 465 u_int i; 466 467 biodone_vfs = biodone; 468 469 mutex_init(&bufcache_lock, MUTEX_DEFAULT, IPL_NONE); 470 mutex_init(&buffer_lock, MUTEX_DEFAULT, IPL_NONE); 471 cv_init(&needbuffer_cv, "needbuf"); 472 473 if (bufmem_valimit != 0) { 474 vaddr_t minaddr = 0, maxaddr; 475 buf_map = uvm_km_suballoc(kernel_map, &minaddr, &maxaddr, 476 bufmem_valimit, 0, false, 0); 477 if (buf_map == NULL) 478 panic("bufinit: cannot allocate submap"); 479 } else 480 buf_map = kernel_map; 481 482 /* 483 * Initialize buffer cache memory parameters. 484 */ 485 bufmem = 0; 486 buf_setwm(); 487 488 /* On "small" machines use small pool page sizes where possible */ 489 use_std = (physmem < atop(16*1024*1024)); 490 491 /* 492 * Also use them on systems that can map the pool pages using 493 * a direct-mapped segment. 494 */ 495 #ifdef PMAP_MAP_POOLPAGE 496 use_std = 1; 497 #endif 498 499 buf_cache = pool_cache_init(sizeof(buf_t), 0, 0, 0, 500 "bufpl", NULL, IPL_SOFTBIO, NULL, NULL, NULL); 501 bufio_cache = pool_cache_init(sizeof(buf_t), 0, 0, 0, 502 "biopl", NULL, IPL_BIO, NULL, NULL, NULL); 503 504 for (i = 0; i < NMEMPOOLS; i++) { 505 struct pool_allocator *pa; 506 struct pool *pp = &bmempools[i]; 507 u_int size = 1 << (i + MEMPOOL_INDEX_OFFSET); 508 char *name = kmem_alloc(8, KM_SLEEP); /* XXX: never freed */ 509 if (__predict_false(size >= 1048576)) 510 (void)snprintf(name, 8, "buf%um", size / 1048576); 511 else if (__predict_true(size >= 1024)) 512 (void)snprintf(name, 8, "buf%uk", size / 1024); 513 else 514 (void)snprintf(name, 8, "buf%ub", size); 515 pa = (size <= PAGE_SIZE && use_std) 516 ? &pool_allocator_nointr 517 : &bufmempool_allocator; 518 pool_init(pp, size, DEV_BSIZE, 0, 0, name, pa, IPL_NONE); 519 pool_setlowat(pp, 1); 520 pool_sethiwat(pp, 1); 521 } 522 523 /* Initialize the buffer queues */ 524 for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++) { 525 TAILQ_INIT(&dp->bq_queue); 526 dp->bq_bytes = 0; 527 } 528 529 /* 530 * Estimate hash table size based on the amount of memory we 531 * intend to use for the buffer cache. The average buffer 532 * size is dependent on our clients (i.e. filesystems). 533 * 534 * For now, use an empirical 3K per buffer. 535 */ 536 nbuf = (bufmem_hiwater / 1024) / 3; 537 bufhashtbl = hashinit(nbuf, HASH_LIST, true, &bufhash); 538 539 sysctl_kern_buf_setup(); 540 sysctl_vm_buf_setup(); 541 hashstat_register("bufhash", bufhash_stats); 542 } 543 544 void 545 bufinit2(void) 546 { 547 548 biodone_sih = softint_establish(SOFTINT_BIO | SOFTINT_MPSAFE, biointr, 549 NULL); 550 if (biodone_sih == NULL) 551 panic("bufinit2: can't establish soft interrupt"); 552 } 553 554 static int 555 buf_lotsfree(void) 556 { 557 u_long guess; 558 559 /* Always allocate if less than the low water mark. */ 560 if (bufmem < bufmem_lowater) 561 return 1; 562 563 /* Never allocate if greater than the high water mark. */ 564 if (bufmem > bufmem_hiwater) 565 return 0; 566 567 /* If there's anything on the AGE list, it should be eaten. */ 568 if (TAILQ_FIRST(&bufqueues[BQ_AGE].bq_queue) != NULL) 569 return 0; 570 571 /* 572 * The probabily of getting a new allocation is inversely 573 * proportional to the current size of the cache above 574 * the low water mark. Divide the total first to avoid overflows 575 * in the product. 576 */ 577 guess = cprng_fast32() % 16; 578 579 if ((bufmem_hiwater - bufmem_lowater) / 16 * guess >= 580 (bufmem - bufmem_lowater)) 581 return 1; 582 583 /* Otherwise don't allocate. */ 584 return 0; 585 } 586 587 /* 588 * Return estimate of bytes we think need to be 589 * released to help resolve low memory conditions. 590 * 591 * => called with bufcache_lock held. 592 */ 593 static int 594 buf_canrelease(void) 595 { 596 int pagedemand, ninvalid = 0; 597 598 KASSERT(mutex_owned(&bufcache_lock)); 599 600 if (bufmem < bufmem_lowater) 601 return 0; 602 603 if (bufmem > bufmem_hiwater) 604 return bufmem - bufmem_hiwater; 605 606 ninvalid += bufqueues[BQ_AGE].bq_bytes; 607 608 pagedemand = uvmexp.freetarg - uvm_availmem(false); 609 if (pagedemand < 0) 610 return ninvalid; 611 return MAX(ninvalid, MIN(2 * MAXBSIZE, 612 MIN((bufmem - bufmem_lowater) / 16, pagedemand * PAGE_SIZE))); 613 } 614 615 /* 616 * Buffer memory allocation helper functions 617 */ 618 static u_long 619 buf_mempoolidx(u_long size) 620 { 621 u_int n = 0; 622 623 size -= 1; 624 size >>= MEMPOOL_INDEX_OFFSET; 625 while (size) { 626 size >>= 1; 627 n += 1; 628 } 629 if (n >= NMEMPOOLS) 630 panic("buf mem pool index %d", n); 631 return n; 632 } 633 634 static u_long 635 buf_roundsize(u_long size) 636 { 637 /* Round up to nearest power of 2 */ 638 return (1 << (buf_mempoolidx(size) + MEMPOOL_INDEX_OFFSET)); 639 } 640 641 static void * 642 buf_alloc(size_t size) 643 { 644 u_int n = buf_mempoolidx(size); 645 void *addr; 646 647 while (1) { 648 addr = pool_get(&bmempools[n], PR_NOWAIT); 649 if (addr != NULL) 650 break; 651 652 /* No memory, see if we can free some. If so, try again */ 653 mutex_enter(&bufcache_lock); 654 if (buf_drain(1) > 0) { 655 mutex_exit(&bufcache_lock); 656 continue; 657 } 658 659 if (curlwp == uvm.pagedaemon_lwp) { 660 mutex_exit(&bufcache_lock); 661 return NULL; 662 } 663 664 /* Wait for buffers to arrive on the LRU queue */ 665 cv_timedwait(&needbuffer_cv, &bufcache_lock, hz / 4); 666 mutex_exit(&bufcache_lock); 667 } 668 669 return addr; 670 } 671 672 static void 673 buf_mrelease(void *addr, size_t size) 674 { 675 676 pool_put(&bmempools[buf_mempoolidx(size)], addr); 677 } 678 679 /* 680 * bread()/breadn() helper. 681 */ 682 static buf_t * 683 bio_doread(struct vnode *vp, daddr_t blkno, int size, int async) 684 { 685 buf_t *bp; 686 struct mount *mp; 687 688 bp = getblk(vp, blkno, size, 0, 0); 689 690 /* 691 * getblk() may return NULL if we are the pagedaemon. 692 */ 693 if (bp == NULL) { 694 KASSERT(curlwp == uvm.pagedaemon_lwp); 695 return NULL; 696 } 697 698 /* 699 * If buffer does not have data valid, start a read. 700 * Note that if buffer is BC_INVAL, getblk() won't return it. 701 * Therefore, it's valid if its I/O has completed or been delayed. 702 */ 703 if (!ISSET(bp->b_oflags, (BO_DONE | BO_DELWRI))) { 704 /* Start I/O for the buffer. */ 705 SET(bp->b_flags, B_READ | async); 706 if (async) 707 BIO_SETPRIO(bp, BPRIO_TIMELIMITED); 708 else 709 BIO_SETPRIO(bp, BPRIO_TIMECRITICAL); 710 VOP_STRATEGY(vp, bp); 711 712 /* Pay for the read. */ 713 curlwp->l_ru.ru_inblock++; 714 } else if (async) 715 brelse(bp, 0); 716 717 if (vp->v_type == VBLK) 718 mp = spec_node_getmountedfs(vp); 719 else 720 mp = vp->v_mount; 721 722 /* 723 * Collect statistics on synchronous and asynchronous reads. 724 * Reads from block devices are charged to their associated 725 * filesystem (if any). 726 */ 727 if (mp != NULL) { 728 if (async == 0) 729 mp->mnt_stat.f_syncreads++; 730 else 731 mp->mnt_stat.f_asyncreads++; 732 } 733 734 return (bp); 735 } 736 737 /* 738 * Read a disk block. 739 * This algorithm described in Bach (p.54). 740 */ 741 int 742 bread(struct vnode *vp, daddr_t blkno, int size, int flags, buf_t **bpp) 743 { 744 buf_t *bp; 745 int error; 746 747 BIOHIST_FUNC(__func__); BIOHIST_CALLED(biohist); 748 749 /* Get buffer for block. */ 750 bp = *bpp = bio_doread(vp, blkno, size, 0); 751 if (bp == NULL) 752 return ENOMEM; 753 754 /* Wait for the read to complete, and return result. */ 755 error = biowait(bp); 756 if (error == 0 && (flags & B_MODIFY) != 0) 757 error = fscow_run(bp, true); 758 if (error) { 759 brelse(bp, 0); 760 *bpp = NULL; 761 } 762 763 return error; 764 } 765 766 /* 767 * Read-ahead multiple disk blocks. The first is sync, the rest async. 768 * Trivial modification to the breada algorithm presented in Bach (p.55). 769 */ 770 int 771 breadn(struct vnode *vp, daddr_t blkno, int size, daddr_t *rablks, 772 int *rasizes, int nrablks, int flags, buf_t **bpp) 773 { 774 buf_t *bp; 775 int error, i; 776 777 BIOHIST_FUNC(__func__); BIOHIST_CALLED(biohist); 778 779 bp = *bpp = bio_doread(vp, blkno, size, 0); 780 if (bp == NULL) 781 return ENOMEM; 782 783 /* 784 * For each of the read-ahead blocks, start a read, if necessary. 785 */ 786 mutex_enter(&bufcache_lock); 787 for (i = 0; i < nrablks; i++) { 788 /* If it's in the cache, just go on to next one. */ 789 if (incore(vp, rablks[i])) 790 continue; 791 792 /* Get a buffer for the read-ahead block */ 793 mutex_exit(&bufcache_lock); 794 (void) bio_doread(vp, rablks[i], rasizes[i], B_ASYNC); 795 mutex_enter(&bufcache_lock); 796 } 797 mutex_exit(&bufcache_lock); 798 799 /* Otherwise, we had to start a read for it; wait until it's valid. */ 800 error = biowait(bp); 801 if (error == 0 && (flags & B_MODIFY) != 0) 802 error = fscow_run(bp, true); 803 if (error) { 804 brelse(bp, 0); 805 *bpp = NULL; 806 } 807 808 return error; 809 } 810 811 /* 812 * Block write. Described in Bach (p.56) 813 */ 814 int 815 bwrite(buf_t *bp) 816 { 817 int rv, sync, wasdelayed; 818 struct vnode *vp; 819 struct mount *mp; 820 821 BIOHIST_FUNC(__func__); BIOHIST_CALLARGS(biohist, "bp=%#jx", 822 (uintptr_t)bp, 0, 0, 0); 823 824 KASSERT(ISSET(bp->b_cflags, BC_BUSY)); 825 KASSERT(!cv_has_waiters(&bp->b_done)); 826 827 vp = bp->b_vp; 828 829 /* 830 * dholland 20160728 AFAICT vp==NULL must be impossible as it 831 * will crash upon reaching VOP_STRATEGY below... see further 832 * analysis on tech-kern. 833 */ 834 KASSERTMSG(vp != NULL, "bwrite given buffer with null vnode"); 835 836 if (vp != NULL) { 837 KASSERT(bp->b_objlock == vp->v_interlock); 838 if (vp->v_type == VBLK) 839 mp = spec_node_getmountedfs(vp); 840 else 841 mp = vp->v_mount; 842 } else { 843 mp = NULL; 844 } 845 846 if (mp && mp->mnt_wapbl) { 847 if (bp->b_iodone != mp->mnt_wapbl_op->wo_wapbl_biodone) { 848 bdwrite(bp); 849 return 0; 850 } 851 } 852 853 /* 854 * Remember buffer type, to switch on it later. If the write was 855 * synchronous, but the file system was mounted with MNT_ASYNC, 856 * convert it to a delayed write. 857 * XXX note that this relies on delayed tape writes being converted 858 * to async, not sync writes (which is safe, but ugly). 859 */ 860 sync = !ISSET(bp->b_flags, B_ASYNC); 861 if (sync && mp != NULL && ISSET(mp->mnt_flag, MNT_ASYNC)) { 862 bdwrite(bp); 863 return (0); 864 } 865 866 /* 867 * Collect statistics on synchronous and asynchronous writes. 868 * Writes to block devices are charged to their associated 869 * filesystem (if any). 870 */ 871 if (mp != NULL) { 872 if (sync) 873 mp->mnt_stat.f_syncwrites++; 874 else 875 mp->mnt_stat.f_asyncwrites++; 876 } 877 878 /* 879 * Pay for the I/O operation and make sure the buf is on the correct 880 * vnode queue. 881 */ 882 bp->b_error = 0; 883 wasdelayed = ISSET(bp->b_oflags, BO_DELWRI); 884 CLR(bp->b_flags, B_READ); 885 if (wasdelayed) { 886 mutex_enter(&bufcache_lock); 887 mutex_enter(bp->b_objlock); 888 CLR(bp->b_oflags, BO_DONE | BO_DELWRI); 889 reassignbuf(bp, bp->b_vp); 890 /* Wake anyone trying to busy the buffer via vnode's lists. */ 891 cv_broadcast(&bp->b_busy); 892 mutex_exit(&bufcache_lock); 893 } else { 894 curlwp->l_ru.ru_oublock++; 895 mutex_enter(bp->b_objlock); 896 CLR(bp->b_oflags, BO_DONE | BO_DELWRI); 897 } 898 if (vp != NULL) 899 vp->v_numoutput++; 900 mutex_exit(bp->b_objlock); 901 902 /* Initiate disk write. */ 903 if (sync) 904 BIO_SETPRIO(bp, BPRIO_TIMECRITICAL); 905 else 906 BIO_SETPRIO(bp, BPRIO_TIMELIMITED); 907 908 VOP_STRATEGY(vp, bp); 909 910 if (sync) { 911 /* If I/O was synchronous, wait for it to complete. */ 912 rv = biowait(bp); 913 914 /* Release the buffer. */ 915 brelse(bp, 0); 916 917 return (rv); 918 } else { 919 return (0); 920 } 921 } 922 923 int 924 vn_bwrite(void *v) 925 { 926 struct vop_bwrite_args *ap = v; 927 928 return (bwrite(ap->a_bp)); 929 } 930 931 /* 932 * Delayed write. 933 * 934 * The buffer is marked dirty, but is not queued for I/O. 935 * This routine should be used when the buffer is expected 936 * to be modified again soon, typically a small write that 937 * partially fills a buffer. 938 * 939 * NB: magnetic tapes cannot be delayed; they must be 940 * written in the order that the writes are requested. 941 * 942 * Described in Leffler, et al. (pp. 208-213). 943 */ 944 void 945 bdwrite(buf_t *bp) 946 { 947 948 BIOHIST_FUNC(__func__); BIOHIST_CALLARGS(biohist, "bp=%#jx", 949 (uintptr_t)bp, 0, 0, 0); 950 951 KASSERT(bp->b_vp == NULL || bp->b_vp->v_tag != VT_UFS || 952 bp->b_vp->v_type == VBLK || ISSET(bp->b_flags, B_COWDONE)); 953 KASSERT(ISSET(bp->b_cflags, BC_BUSY)); 954 KASSERT(!cv_has_waiters(&bp->b_done)); 955 956 /* If this is a tape block, write the block now. */ 957 if (bdev_type(bp->b_dev) == D_TAPE) { 958 bawrite(bp); 959 return; 960 } 961 962 if (wapbl_vphaswapbl(bp->b_vp)) { 963 struct mount *mp = wapbl_vptomp(bp->b_vp); 964 965 if (bp->b_iodone != mp->mnt_wapbl_op->wo_wapbl_biodone) { 966 WAPBL_ADD_BUF(mp, bp); 967 } 968 } 969 970 /* 971 * If the block hasn't been seen before: 972 * (1) Mark it as having been seen, 973 * (2) Charge for the write, 974 * (3) Make sure it's on its vnode's correct block list. 975 */ 976 KASSERT(bp->b_vp == NULL || bp->b_objlock == bp->b_vp->v_interlock); 977 978 if (!ISSET(bp->b_oflags, BO_DELWRI)) { 979 mutex_enter(&bufcache_lock); 980 mutex_enter(bp->b_objlock); 981 SET(bp->b_oflags, BO_DELWRI); 982 curlwp->l_ru.ru_oublock++; 983 reassignbuf(bp, bp->b_vp); 984 /* Wake anyone trying to busy the buffer via vnode's lists. */ 985 cv_broadcast(&bp->b_busy); 986 mutex_exit(&bufcache_lock); 987 } else { 988 mutex_enter(bp->b_objlock); 989 } 990 /* Otherwise, the "write" is done, so mark and release the buffer. */ 991 CLR(bp->b_oflags, BO_DONE); 992 mutex_exit(bp->b_objlock); 993 994 brelse(bp, 0); 995 } 996 997 /* 998 * Asynchronous block write; just an asynchronous bwrite(). 999 */ 1000 void 1001 bawrite(buf_t *bp) 1002 { 1003 1004 KASSERT(ISSET(bp->b_cflags, BC_BUSY)); 1005 KASSERT(bp->b_vp != NULL); 1006 1007 SET(bp->b_flags, B_ASYNC); 1008 VOP_BWRITE(bp->b_vp, bp); 1009 } 1010 1011 /* 1012 * Release a buffer on to the free lists. 1013 * Described in Bach (p. 46). 1014 */ 1015 void 1016 brelsel(buf_t *bp, int set) 1017 { 1018 struct bqueue *bufq; 1019 struct vnode *vp; 1020 1021 SDT_PROBE2(io, kernel, , brelse, bp, set); 1022 1023 KASSERT(bp != NULL); 1024 KASSERT(mutex_owned(&bufcache_lock)); 1025 KASSERT(!cv_has_waiters(&bp->b_done)); 1026 1027 SET(bp->b_cflags, set); 1028 1029 KASSERT(ISSET(bp->b_cflags, BC_BUSY)); 1030 KASSERT(bp->b_iodone == NULL); 1031 1032 /* Wake up any processes waiting for any buffer to become free. */ 1033 cv_signal(&needbuffer_cv); 1034 1035 /* Wake up any proceeses waiting for _this_ buffer to become free */ 1036 if (ISSET(bp->b_cflags, BC_WANTED)) 1037 CLR(bp->b_cflags, BC_WANTED|BC_AGE); 1038 1039 /* If it's clean clear the copy-on-write flag. */ 1040 if (ISSET(bp->b_flags, B_COWDONE)) { 1041 mutex_enter(bp->b_objlock); 1042 if (!ISSET(bp->b_oflags, BO_DELWRI)) 1043 CLR(bp->b_flags, B_COWDONE); 1044 mutex_exit(bp->b_objlock); 1045 } 1046 1047 /* 1048 * Determine which queue the buffer should be on, then put it there. 1049 */ 1050 1051 /* If it's locked, don't report an error; try again later. */ 1052 if (ISSET(bp->b_flags, B_LOCKED)) 1053 bp->b_error = 0; 1054 1055 /* If it's not cacheable, or an error, mark it invalid. */ 1056 if (ISSET(bp->b_cflags, BC_NOCACHE) || bp->b_error != 0) 1057 SET(bp->b_cflags, BC_INVAL); 1058 1059 if (ISSET(bp->b_cflags, BC_VFLUSH)) { 1060 /* 1061 * This is a delayed write buffer that was just flushed to 1062 * disk. It is still on the LRU queue. If it's become 1063 * invalid, then we need to move it to a different queue; 1064 * otherwise leave it in its current position. 1065 */ 1066 CLR(bp->b_cflags, BC_VFLUSH); 1067 if (!ISSET(bp->b_cflags, BC_INVAL|BC_AGE) && 1068 !ISSET(bp->b_flags, B_LOCKED) && bp->b_error == 0) { 1069 KDASSERT(checkfreelist(bp, &bufqueues[BQ_LRU], 1)); 1070 goto already_queued; 1071 } else { 1072 bremfree(bp); 1073 } 1074 } 1075 1076 KDASSERT(checkfreelist(bp, &bufqueues[BQ_AGE], 0)); 1077 KDASSERT(checkfreelist(bp, &bufqueues[BQ_LRU], 0)); 1078 KDASSERT(checkfreelist(bp, &bufqueues[BQ_LOCKED], 0)); 1079 1080 if ((bp->b_bufsize <= 0) || ISSET(bp->b_cflags, BC_INVAL)) { 1081 /* 1082 * If it's invalid or empty, dissociate it from its vnode 1083 * and put on the head of the appropriate queue. 1084 */ 1085 if (ISSET(bp->b_flags, B_LOCKED)) { 1086 if (wapbl_vphaswapbl(vp = bp->b_vp)) { 1087 struct mount *mp = wapbl_vptomp(vp); 1088 1089 KASSERT(bp->b_iodone 1090 != mp->mnt_wapbl_op->wo_wapbl_biodone); 1091 WAPBL_REMOVE_BUF(mp, bp); 1092 } 1093 } 1094 1095 mutex_enter(bp->b_objlock); 1096 CLR(bp->b_oflags, BO_DONE|BO_DELWRI); 1097 if ((vp = bp->b_vp) != NULL) { 1098 KASSERT(bp->b_objlock == vp->v_interlock); 1099 reassignbuf(bp, bp->b_vp); 1100 brelvp(bp); 1101 mutex_exit(vp->v_interlock); 1102 } else { 1103 KASSERT(bp->b_objlock == &buffer_lock); 1104 mutex_exit(bp->b_objlock); 1105 } 1106 /* We want to dispose of the buffer, so wake everybody. */ 1107 cv_broadcast(&bp->b_busy); 1108 if (bp->b_bufsize <= 0) 1109 /* no data */ 1110 goto already_queued; 1111 else 1112 /* invalid data */ 1113 bufq = &bufqueues[BQ_AGE]; 1114 binsheadfree(bp, bufq); 1115 } else { 1116 /* 1117 * It has valid data. Put it on the end of the appropriate 1118 * queue, so that it'll stick around for as long as possible. 1119 * If buf is AGE, but has dependencies, must put it on last 1120 * bufqueue to be scanned, ie LRU. This protects against the 1121 * livelock where BQ_AGE only has buffers with dependencies, 1122 * and we thus never get to the dependent buffers in BQ_LRU. 1123 */ 1124 if (ISSET(bp->b_flags, B_LOCKED)) { 1125 /* locked in core */ 1126 bufq = &bufqueues[BQ_LOCKED]; 1127 } else if (!ISSET(bp->b_cflags, BC_AGE)) { 1128 /* valid data */ 1129 bufq = &bufqueues[BQ_LRU]; 1130 } else { 1131 /* stale but valid data */ 1132 bufq = &bufqueues[BQ_AGE]; 1133 } 1134 binstailfree(bp, bufq); 1135 } 1136 already_queued: 1137 /* Unlock the buffer. */ 1138 CLR(bp->b_cflags, BC_AGE|BC_BUSY|BC_NOCACHE); 1139 CLR(bp->b_flags, B_ASYNC); 1140 1141 /* 1142 * Wake only the highest priority waiter on the lock, in order to 1143 * prevent a thundering herd: many LWPs simultaneously awakening and 1144 * competing for the buffer's lock. Testing in 2019 revealed this 1145 * to reduce contention on bufcache_lock tenfold during a kernel 1146 * compile. Here and elsewhere, when the buffer is changing 1147 * identity, being disposed of, or moving from one list to another, 1148 * we wake all lock requestors. 1149 */ 1150 if (bp->b_bufsize <= 0) { 1151 cv_broadcast(&bp->b_busy); 1152 buf_destroy(bp); 1153 #ifdef DEBUG 1154 memset((char *)bp, 0, sizeof(*bp)); 1155 #endif 1156 pool_cache_put(buf_cache, bp); 1157 } else 1158 cv_signal(&bp->b_busy); 1159 } 1160 1161 void 1162 brelse(buf_t *bp, int set) 1163 { 1164 1165 mutex_enter(&bufcache_lock); 1166 brelsel(bp, set); 1167 mutex_exit(&bufcache_lock); 1168 } 1169 1170 /* 1171 * Determine if a block is in the cache. 1172 * Just look on what would be its hash chain. If it's there, return 1173 * a pointer to it, unless it's marked invalid. If it's marked invalid, 1174 * we normally don't return the buffer, unless the caller explicitly 1175 * wants us to. 1176 */ 1177 buf_t * 1178 incore(struct vnode *vp, daddr_t blkno) 1179 { 1180 buf_t *bp; 1181 1182 KASSERT(mutex_owned(&bufcache_lock)); 1183 1184 /* Search hash chain */ 1185 LIST_FOREACH(bp, BUFHASH(vp, blkno), b_hash) { 1186 if (bp->b_lblkno == blkno && bp->b_vp == vp && 1187 !ISSET(bp->b_cflags, BC_INVAL)) { 1188 KASSERT(bp->b_objlock == vp->v_interlock); 1189 return (bp); 1190 } 1191 } 1192 1193 return (NULL); 1194 } 1195 1196 /* 1197 * Get a block of requested size that is associated with 1198 * a given vnode and block offset. If it is found in the 1199 * block cache, mark it as having been found, make it busy 1200 * and return it. Otherwise, return an empty block of the 1201 * correct size. It is up to the caller to insure that the 1202 * cached blocks be of the correct size. 1203 */ 1204 buf_t * 1205 getblk(struct vnode *vp, daddr_t blkno, int size, int slpflag, int slptimeo) 1206 { 1207 int err, preserve; 1208 buf_t *bp; 1209 1210 mutex_enter(&bufcache_lock); 1211 SDT_PROBE3(io, kernel, , getblk__start, vp, blkno, size); 1212 loop: 1213 bp = incore(vp, blkno); 1214 if (bp != NULL) { 1215 err = bbusy(bp, ((slpflag & PCATCH) != 0), slptimeo, NULL); 1216 if (err != 0) { 1217 if (err == EPASSTHROUGH) 1218 goto loop; 1219 mutex_exit(&bufcache_lock); 1220 SDT_PROBE4(io, kernel, , getblk__done, 1221 vp, blkno, size, NULL); 1222 return (NULL); 1223 } 1224 KASSERT(!cv_has_waiters(&bp->b_done)); 1225 #ifdef DIAGNOSTIC 1226 if (ISSET(bp->b_oflags, BO_DONE|BO_DELWRI) && 1227 bp->b_bcount < size && vp->v_type != VBLK) 1228 panic("getblk: block size invariant failed"); 1229 #endif 1230 bremfree(bp); 1231 preserve = 1; 1232 } else { 1233 if ((bp = getnewbuf(slpflag, slptimeo, 0)) == NULL) 1234 goto loop; 1235 1236 if (incore(vp, blkno) != NULL) { 1237 /* The block has come into memory in the meantime. */ 1238 brelsel(bp, 0); 1239 goto loop; 1240 } 1241 1242 LIST_INSERT_HEAD(BUFHASH(vp, blkno), bp, b_hash); 1243 bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = blkno; 1244 mutex_enter(vp->v_interlock); 1245 bgetvp(vp, bp); 1246 mutex_exit(vp->v_interlock); 1247 preserve = 0; 1248 } 1249 mutex_exit(&bufcache_lock); 1250 1251 /* 1252 * LFS can't track total size of B_LOCKED buffer (locked_queue_bytes) 1253 * if we re-size buffers here. 1254 */ 1255 if (ISSET(bp->b_flags, B_LOCKED)) { 1256 KASSERT(bp->b_bufsize >= size); 1257 } else { 1258 if (allocbuf(bp, size, preserve)) { 1259 mutex_enter(&bufcache_lock); 1260 LIST_REMOVE(bp, b_hash); 1261 brelsel(bp, BC_INVAL); 1262 mutex_exit(&bufcache_lock); 1263 SDT_PROBE4(io, kernel, , getblk__done, 1264 vp, blkno, size, NULL); 1265 return NULL; 1266 } 1267 } 1268 BIO_SETPRIO(bp, BPRIO_DEFAULT); 1269 SDT_PROBE4(io, kernel, , getblk__done, vp, blkno, size, bp); 1270 return (bp); 1271 } 1272 1273 /* 1274 * Get an empty, disassociated buffer of given size. 1275 */ 1276 buf_t * 1277 geteblk(int size) 1278 { 1279 buf_t *bp; 1280 int error __diagused; 1281 1282 mutex_enter(&bufcache_lock); 1283 while ((bp = getnewbuf(0, 0, 0)) == NULL) 1284 ; 1285 1286 SET(bp->b_cflags, BC_INVAL); 1287 LIST_INSERT_HEAD(&invalhash, bp, b_hash); 1288 mutex_exit(&bufcache_lock); 1289 BIO_SETPRIO(bp, BPRIO_DEFAULT); 1290 error = allocbuf(bp, size, 0); 1291 KASSERT(error == 0); 1292 return (bp); 1293 } 1294 1295 /* 1296 * Expand or contract the actual memory allocated to a buffer. 1297 * 1298 * If the buffer shrinks, data is lost, so it's up to the 1299 * caller to have written it out *first*; this routine will not 1300 * start a write. If the buffer grows, it's the callers 1301 * responsibility to fill out the buffer's additional contents. 1302 */ 1303 int 1304 allocbuf(buf_t *bp, int size, int preserve) 1305 { 1306 void *addr; 1307 vsize_t oldsize, desired_size; 1308 int oldcount; 1309 int delta; 1310 1311 desired_size = buf_roundsize(size); 1312 if (desired_size > MAXBSIZE) 1313 printf("allocbuf: buffer larger than MAXBSIZE requested"); 1314 1315 oldcount = bp->b_bcount; 1316 1317 bp->b_bcount = size; 1318 1319 oldsize = bp->b_bufsize; 1320 if (oldsize == desired_size) { 1321 /* 1322 * Do not short cut the WAPBL resize, as the buffer length 1323 * could still have changed and this would corrupt the 1324 * tracking of the transaction length. 1325 */ 1326 goto out; 1327 } 1328 1329 /* 1330 * If we want a buffer of a different size, re-allocate the 1331 * buffer's memory; copy old content only if needed. 1332 */ 1333 addr = buf_alloc(desired_size); 1334 if (addr == NULL) 1335 return ENOMEM; 1336 if (preserve) 1337 memcpy(addr, bp->b_data, MIN(oldsize,desired_size)); 1338 if (bp->b_data != NULL) 1339 buf_mrelease(bp->b_data, oldsize); 1340 bp->b_data = addr; 1341 bp->b_bufsize = desired_size; 1342 1343 /* 1344 * Update overall buffer memory counter (protected by bufcache_lock) 1345 */ 1346 delta = (long)desired_size - (long)oldsize; 1347 1348 mutex_enter(&bufcache_lock); 1349 if ((bufmem += delta) > bufmem_hiwater) { 1350 /* 1351 * Need to trim overall memory usage. 1352 */ 1353 while (buf_canrelease()) { 1354 if (preempt_needed()) { 1355 mutex_exit(&bufcache_lock); 1356 preempt(); 1357 mutex_enter(&bufcache_lock); 1358 } 1359 if (buf_trim() == 0) 1360 break; 1361 } 1362 } 1363 mutex_exit(&bufcache_lock); 1364 1365 out: 1366 if (wapbl_vphaswapbl(bp->b_vp)) 1367 WAPBL_RESIZE_BUF(wapbl_vptomp(bp->b_vp), bp, oldsize, oldcount); 1368 1369 return 0; 1370 } 1371 1372 /* 1373 * Find a buffer which is available for use. 1374 * Select something from a free list. 1375 * Preference is to AGE list, then LRU list. 1376 * 1377 * Called with the buffer queues locked. 1378 * Return buffer locked. 1379 */ 1380 static buf_t * 1381 getnewbuf(int slpflag, int slptimeo, int from_bufq) 1382 { 1383 buf_t *bp; 1384 struct vnode *vp; 1385 struct mount *transmp = NULL; 1386 1387 SDT_PROBE0(io, kernel, , getnewbuf__start); 1388 1389 start: 1390 KASSERT(mutex_owned(&bufcache_lock)); 1391 1392 /* 1393 * Get a new buffer from the pool. 1394 */ 1395 if (!from_bufq && buf_lotsfree()) { 1396 mutex_exit(&bufcache_lock); 1397 bp = pool_cache_get(buf_cache, PR_NOWAIT); 1398 if (bp != NULL) { 1399 memset((char *)bp, 0, sizeof(*bp)); 1400 buf_init(bp); 1401 SET(bp->b_cflags, BC_BUSY); /* mark buffer busy */ 1402 mutex_enter(&bufcache_lock); 1403 #if defined(DIAGNOSTIC) 1404 bp->b_freelistindex = -1; 1405 #endif /* defined(DIAGNOSTIC) */ 1406 SDT_PROBE1(io, kernel, , getnewbuf__done, bp); 1407 return (bp); 1408 } 1409 mutex_enter(&bufcache_lock); 1410 } 1411 1412 KASSERT(mutex_owned(&bufcache_lock)); 1413 if ((bp = TAILQ_FIRST(&bufqueues[BQ_AGE].bq_queue)) != NULL) { 1414 KASSERT(!ISSET(bp->b_oflags, BO_DELWRI)); 1415 } else { 1416 TAILQ_FOREACH(bp, &bufqueues[BQ_LRU].bq_queue, b_freelist) { 1417 if (ISSET(bp->b_cflags, BC_VFLUSH) || 1418 !ISSET(bp->b_oflags, BO_DELWRI)) 1419 break; 1420 if (fstrans_start_nowait(bp->b_vp->v_mount) == 0) { 1421 KASSERT(transmp == NULL); 1422 transmp = bp->b_vp->v_mount; 1423 break; 1424 } 1425 } 1426 } 1427 if (bp != NULL) { 1428 KASSERT(!ISSET(bp->b_cflags, BC_BUSY) || ISSET(bp->b_cflags, BC_VFLUSH)); 1429 bremfree(bp); 1430 1431 /* Buffer is no longer on free lists. */ 1432 SET(bp->b_cflags, BC_BUSY); 1433 1434 /* Wake anyone trying to lock the old identity. */ 1435 cv_broadcast(&bp->b_busy); 1436 } else { 1437 /* 1438 * XXX: !from_bufq should be removed. 1439 */ 1440 if (!from_bufq || curlwp != uvm.pagedaemon_lwp) { 1441 /* wait for a free buffer of any kind */ 1442 if ((slpflag & PCATCH) != 0) 1443 (void)cv_timedwait_sig(&needbuffer_cv, 1444 &bufcache_lock, slptimeo); 1445 else 1446 (void)cv_timedwait(&needbuffer_cv, 1447 &bufcache_lock, slptimeo); 1448 } 1449 SDT_PROBE1(io, kernel, , getnewbuf__done, NULL); 1450 return (NULL); 1451 } 1452 1453 #ifdef DIAGNOSTIC 1454 if (bp->b_bufsize <= 0) 1455 panic("buffer %p: on queue but empty", bp); 1456 #endif 1457 1458 if (ISSET(bp->b_cflags, BC_VFLUSH)) { 1459 /* 1460 * This is a delayed write buffer being flushed to disk. Make 1461 * sure it gets aged out of the queue when it's finished, and 1462 * leave it off the LRU queue. 1463 */ 1464 CLR(bp->b_cflags, BC_VFLUSH); 1465 SET(bp->b_cflags, BC_AGE); 1466 goto start; 1467 } 1468 1469 KASSERT(ISSET(bp->b_cflags, BC_BUSY)); 1470 KASSERT(!cv_has_waiters(&bp->b_done)); 1471 1472 /* 1473 * If buffer was a delayed write, start it and return NULL 1474 * (since we might sleep while starting the write). 1475 */ 1476 if (ISSET(bp->b_oflags, BO_DELWRI)) { 1477 /* 1478 * This buffer has gone through the LRU, so make sure it gets 1479 * reused ASAP. 1480 */ 1481 SET(bp->b_cflags, BC_AGE); 1482 mutex_exit(&bufcache_lock); 1483 bawrite(bp); 1484 KASSERT(transmp != NULL); 1485 fstrans_done(transmp); 1486 mutex_enter(&bufcache_lock); 1487 SDT_PROBE1(io, kernel, , getnewbuf__done, NULL); 1488 return (NULL); 1489 } 1490 1491 KASSERT(transmp == NULL); 1492 1493 vp = bp->b_vp; 1494 1495 /* clear out various other fields */ 1496 bp->b_cflags = BC_BUSY; 1497 bp->b_oflags = 0; 1498 bp->b_flags = 0; 1499 bp->b_dev = NODEV; 1500 bp->b_blkno = 0; 1501 bp->b_lblkno = 0; 1502 bp->b_rawblkno = 0; 1503 bp->b_iodone = 0; 1504 bp->b_error = 0; 1505 bp->b_resid = 0; 1506 bp->b_bcount = 0; 1507 1508 LIST_REMOVE(bp, b_hash); 1509 1510 /* Disassociate us from our vnode, if we had one... */ 1511 if (vp != NULL) { 1512 mutex_enter(vp->v_interlock); 1513 brelvp(bp); 1514 mutex_exit(vp->v_interlock); 1515 } 1516 1517 SDT_PROBE1(io, kernel, , getnewbuf__done, bp); 1518 return (bp); 1519 } 1520 1521 /* 1522 * Invalidate the specified buffer if it exists. 1523 */ 1524 void 1525 binvalbuf(struct vnode *vp, daddr_t blkno) 1526 { 1527 buf_t *bp; 1528 int err; 1529 1530 mutex_enter(&bufcache_lock); 1531 1532 loop: 1533 bp = incore(vp, blkno); 1534 if (bp != NULL) { 1535 err = bbusy(bp, 0, 0, NULL); 1536 if (err == EPASSTHROUGH) 1537 goto loop; 1538 bremfree(bp); 1539 if (ISSET(bp->b_oflags, BO_DELWRI)) { 1540 SET(bp->b_cflags, BC_NOCACHE); 1541 mutex_exit(&bufcache_lock); 1542 bwrite(bp); 1543 } else { 1544 brelsel(bp, BC_INVAL); 1545 mutex_exit(&bufcache_lock); 1546 } 1547 } else 1548 mutex_exit(&bufcache_lock); 1549 } 1550 1551 /* 1552 * Attempt to free an aged buffer off the queues. 1553 * Called with queue lock held. 1554 * Returns the amount of buffer memory freed. 1555 */ 1556 static int 1557 buf_trim(void) 1558 { 1559 buf_t *bp; 1560 long size; 1561 1562 KASSERT(mutex_owned(&bufcache_lock)); 1563 1564 /* Instruct getnewbuf() to get buffers off the queues */ 1565 if ((bp = getnewbuf(PCATCH, 1, 1)) == NULL) 1566 return 0; 1567 1568 KASSERT((bp->b_cflags & BC_WANTED) == 0); 1569 size = bp->b_bufsize; 1570 bufmem -= size; 1571 if (size > 0) { 1572 buf_mrelease(bp->b_data, size); 1573 bp->b_bcount = bp->b_bufsize = 0; 1574 } 1575 /* brelse() will return the buffer to the global buffer pool */ 1576 brelsel(bp, 0); 1577 return size; 1578 } 1579 1580 int 1581 buf_drain(int n) 1582 { 1583 int size = 0, sz; 1584 1585 KASSERT(mutex_owned(&bufcache_lock)); 1586 1587 while (size < n && bufmem > bufmem_lowater) { 1588 sz = buf_trim(); 1589 if (sz <= 0) 1590 break; 1591 size += sz; 1592 } 1593 1594 return size; 1595 } 1596 1597 /* 1598 * Wait for operations on the buffer to complete. 1599 * When they do, extract and return the I/O's error value. 1600 */ 1601 int 1602 biowait(buf_t *bp) 1603 { 1604 1605 BIOHIST_FUNC(__func__); 1606 1607 KASSERT(ISSET(bp->b_cflags, BC_BUSY)); 1608 1609 SDT_PROBE1(io, kernel, , wait__start, bp); 1610 1611 mutex_enter(bp->b_objlock); 1612 1613 BIOHIST_CALLARGS(biohist, "bp=%#jx, oflags=0x%jx, ret_addr=%#jx", 1614 (uintptr_t)bp, bp->b_oflags, 1615 (uintptr_t)__builtin_return_address(0), 0); 1616 1617 while (!ISSET(bp->b_oflags, BO_DONE | BO_DELWRI)) { 1618 BIOHIST_LOG(biohist, "waiting bp=%#jx", (uintptr_t)bp, 0, 0, 0); 1619 cv_wait(&bp->b_done, bp->b_objlock); 1620 } 1621 mutex_exit(bp->b_objlock); 1622 1623 SDT_PROBE1(io, kernel, , wait__done, bp); 1624 1625 BIOHIST_LOG(biohist, "return %jd", bp->b_error, 0, 0, 0); 1626 1627 return bp->b_error; 1628 } 1629 1630 /* 1631 * Mark I/O complete on a buffer. 1632 * 1633 * If a callback has been requested, e.g. the pageout 1634 * daemon, do so. Otherwise, awaken waiting processes. 1635 * 1636 * [ Leffler, et al., says on p.247: 1637 * "This routine wakes up the blocked process, frees the buffer 1638 * for an asynchronous write, or, for a request by the pagedaemon 1639 * process, invokes a procedure specified in the buffer structure" ] 1640 * 1641 * In real life, the pagedaemon (or other system processes) wants 1642 * to do async stuff too, and doesn't want the buffer brelse()'d. 1643 * (for swap pager, that puts swap buffers on the free lists (!!!), 1644 * for the vn device, that puts allocated buffers on the free lists!) 1645 */ 1646 void 1647 biodone(buf_t *bp) 1648 { 1649 int s; 1650 1651 BIOHIST_FUNC(__func__); 1652 1653 KASSERT(!ISSET(bp->b_oflags, BO_DONE)); 1654 1655 if (cpu_intr_p()) { 1656 /* From interrupt mode: defer to a soft interrupt. */ 1657 s = splvm(); 1658 TAILQ_INSERT_TAIL(&curcpu()->ci_data.cpu_biodone, bp, b_actq); 1659 1660 BIOHIST_CALLARGS(biohist, "bp=%#jx, softint scheduled", 1661 (uintptr_t)bp, 0, 0, 0); 1662 softint_schedule(biodone_sih); 1663 splx(s); 1664 } else { 1665 /* Process now - the buffer may be freed soon. */ 1666 biodone2(bp); 1667 } 1668 } 1669 1670 SDT_PROBE_DEFINE1(io, kernel, , done, "struct buf *"/*bp*/); 1671 1672 static void 1673 biodone2(buf_t *bp) 1674 { 1675 void (*callout)(buf_t *); 1676 1677 SDT_PROBE1(io, kernel, ,done, bp); 1678 1679 BIOHIST_FUNC(__func__); 1680 BIOHIST_CALLARGS(biohist, "bp=%#jx", (uintptr_t)bp, 0, 0, 0); 1681 1682 mutex_enter(bp->b_objlock); 1683 /* Note that the transfer is done. */ 1684 if (ISSET(bp->b_oflags, BO_DONE)) 1685 panic("biodone2 already"); 1686 CLR(bp->b_flags, B_COWDONE); 1687 SET(bp->b_oflags, BO_DONE); 1688 BIO_SETPRIO(bp, BPRIO_DEFAULT); 1689 1690 /* Wake up waiting writers. */ 1691 if (!ISSET(bp->b_flags, B_READ)) 1692 vwakeup(bp); 1693 1694 if ((callout = bp->b_iodone) != NULL) { 1695 BIOHIST_LOG(biohist, "callout %#jx", (uintptr_t)callout, 1696 0, 0, 0); 1697 1698 /* Note callout done, then call out. */ 1699 KASSERT(!cv_has_waiters(&bp->b_done)); 1700 bp->b_iodone = NULL; 1701 mutex_exit(bp->b_objlock); 1702 (*callout)(bp); 1703 } else if (ISSET(bp->b_flags, B_ASYNC)) { 1704 /* If async, release. */ 1705 BIOHIST_LOG(biohist, "async", 0, 0, 0, 0); 1706 KASSERT(!cv_has_waiters(&bp->b_done)); 1707 mutex_exit(bp->b_objlock); 1708 brelse(bp, 0); 1709 } else { 1710 /* Otherwise just wake up waiters in biowait(). */ 1711 BIOHIST_LOG(biohist, "wake-up", 0, 0, 0, 0); 1712 cv_broadcast(&bp->b_done); 1713 mutex_exit(bp->b_objlock); 1714 } 1715 } 1716 1717 static void 1718 biointr(void *cookie) 1719 { 1720 struct cpu_info *ci; 1721 buf_t *bp; 1722 int s; 1723 1724 BIOHIST_FUNC(__func__); BIOHIST_CALLED(biohist); 1725 1726 ci = curcpu(); 1727 1728 s = splvm(); 1729 while (!TAILQ_EMPTY(&ci->ci_data.cpu_biodone)) { 1730 KASSERT(curcpu() == ci); 1731 1732 bp = TAILQ_FIRST(&ci->ci_data.cpu_biodone); 1733 TAILQ_REMOVE(&ci->ci_data.cpu_biodone, bp, b_actq); 1734 splx(s); 1735 1736 BIOHIST_LOG(biohist, "bp=%#jx", (uintptr_t)bp, 0, 0, 0); 1737 biodone2(bp); 1738 1739 s = splvm(); 1740 } 1741 splx(s); 1742 } 1743 1744 static void 1745 sysctl_fillbuf(const buf_t *i, struct buf_sysctl *o) 1746 { 1747 const bool allowaddr = get_expose_address(curproc); 1748 1749 memset(o, 0, sizeof(*o)); 1750 1751 o->b_flags = i->b_flags | i->b_cflags | i->b_oflags; 1752 o->b_error = i->b_error; 1753 o->b_prio = i->b_prio; 1754 o->b_dev = i->b_dev; 1755 o->b_bufsize = i->b_bufsize; 1756 o->b_bcount = i->b_bcount; 1757 o->b_resid = i->b_resid; 1758 COND_SET_VALUE(o->b_addr, PTRTOUINT64(i->b_data), allowaddr); 1759 o->b_blkno = i->b_blkno; 1760 o->b_rawblkno = i->b_rawblkno; 1761 COND_SET_VALUE(o->b_iodone, PTRTOUINT64(i->b_iodone), allowaddr); 1762 COND_SET_VALUE(o->b_proc, PTRTOUINT64(i->b_proc), allowaddr); 1763 COND_SET_VALUE(o->b_vp, PTRTOUINT64(i->b_vp), allowaddr); 1764 COND_SET_VALUE(o->b_saveaddr, PTRTOUINT64(i->b_saveaddr), allowaddr); 1765 o->b_lblkno = i->b_lblkno; 1766 } 1767 1768 static int 1769 sysctl_dobuf(SYSCTLFN_ARGS) 1770 { 1771 buf_t *bp; 1772 struct buf_sysctl bs; 1773 struct bqueue *bq; 1774 char *dp; 1775 u_int i, op, arg; 1776 size_t len, needed, elem_size, out_size; 1777 int error, elem_count, retries; 1778 1779 if (namelen == 1 && name[0] == CTL_QUERY) 1780 return (sysctl_query(SYSCTLFN_CALL(rnode))); 1781 1782 if (namelen != 4) 1783 return (EINVAL); 1784 1785 retries = 100; 1786 retry: 1787 dp = oldp; 1788 len = (oldp != NULL) ? *oldlenp : 0; 1789 op = name[0]; 1790 arg = name[1]; 1791 elem_size = name[2]; 1792 elem_count = name[3]; 1793 out_size = MIN(sizeof(bs), elem_size); 1794 1795 /* 1796 * at the moment, these are just "placeholders" to make the 1797 * API for retrieving kern.buf data more extensible in the 1798 * future. 1799 * 1800 * XXX kern.buf currently has "netbsd32" issues. hopefully 1801 * these will be resolved at a later point. 1802 */ 1803 if (op != KERN_BUF_ALL || arg != KERN_BUF_ALL || 1804 elem_size < 1 || elem_count < 0) 1805 return (EINVAL); 1806 1807 if (oldp == NULL) { 1808 /* count only, don't run through the buffer queues */ 1809 needed = pool_cache_nget(buf_cache) - pool_cache_nput(buf_cache); 1810 *oldlenp = (needed + KERN_BUFSLOP) * elem_size; 1811 1812 return 0; 1813 } 1814 1815 error = 0; 1816 needed = 0; 1817 sysctl_unlock(); 1818 mutex_enter(&bufcache_lock); 1819 for (i = 0; i < BQUEUES; i++) { 1820 bq = &bufqueues[i]; 1821 TAILQ_FOREACH(bp, &bq->bq_queue, b_freelist) { 1822 bq->bq_marker = bp; 1823 if (len >= elem_size && elem_count > 0) { 1824 sysctl_fillbuf(bp, &bs); 1825 mutex_exit(&bufcache_lock); 1826 error = copyout(&bs, dp, out_size); 1827 mutex_enter(&bufcache_lock); 1828 if (error) 1829 break; 1830 if (bq->bq_marker != bp) { 1831 /* 1832 * This sysctl node is only for 1833 * statistics. Retry; if the 1834 * queue keeps changing, then 1835 * bail out. 1836 */ 1837 if (retries-- == 0) { 1838 error = EAGAIN; 1839 break; 1840 } 1841 mutex_exit(&bufcache_lock); 1842 sysctl_relock(); 1843 goto retry; 1844 } 1845 dp += elem_size; 1846 len -= elem_size; 1847 } 1848 needed += elem_size; 1849 if (elem_count > 0 && elem_count != INT_MAX) 1850 elem_count--; 1851 } 1852 if (error != 0) 1853 break; 1854 } 1855 mutex_exit(&bufcache_lock); 1856 sysctl_relock(); 1857 1858 *oldlenp = needed; 1859 1860 return (error); 1861 } 1862 1863 static int 1864 sysctl_bufvm_update(SYSCTLFN_ARGS) 1865 { 1866 int error, rv; 1867 struct sysctlnode node; 1868 unsigned int temp_bufcache; 1869 unsigned long temp_water; 1870 1871 /* Take a copy of the supplied node and its data */ 1872 node = *rnode; 1873 if (node.sysctl_data == &bufcache) { 1874 node.sysctl_data = &temp_bufcache; 1875 temp_bufcache = *(unsigned int *)rnode->sysctl_data; 1876 } else { 1877 node.sysctl_data = &temp_water; 1878 temp_water = *(unsigned long *)rnode->sysctl_data; 1879 } 1880 1881 /* Update the copy */ 1882 error = sysctl_lookup(SYSCTLFN_CALL(&node)); 1883 if (error || newp == NULL) 1884 return (error); 1885 1886 if (rnode->sysctl_data == &bufcache) { 1887 if (temp_bufcache > 100) 1888 return (EINVAL); 1889 bufcache = temp_bufcache; 1890 buf_setwm(); 1891 } else if (rnode->sysctl_data == &bufmem_lowater) { 1892 if (bufmem_hiwater - temp_water < 16) 1893 return (EINVAL); 1894 bufmem_lowater = temp_water; 1895 } else if (rnode->sysctl_data == &bufmem_hiwater) { 1896 if (temp_water - bufmem_lowater < 16) 1897 return (EINVAL); 1898 bufmem_hiwater = temp_water; 1899 } else 1900 return (EINVAL); 1901 1902 /* Drain until below new high water mark */ 1903 sysctl_unlock(); 1904 mutex_enter(&bufcache_lock); 1905 while (bufmem > bufmem_hiwater) { 1906 rv = buf_drain((bufmem - bufmem_hiwater) / (2 * 1024)); 1907 if (rv <= 0) 1908 break; 1909 } 1910 mutex_exit(&bufcache_lock); 1911 sysctl_relock(); 1912 1913 return 0; 1914 } 1915 1916 static struct sysctllog *vfsbio_sysctllog; 1917 1918 static void 1919 sysctl_kern_buf_setup(void) 1920 { 1921 1922 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL, 1923 CTLFLAG_PERMANENT, 1924 CTLTYPE_NODE, "buf", 1925 SYSCTL_DESCR("Kernel buffer cache information"), 1926 sysctl_dobuf, 0, NULL, 0, 1927 CTL_KERN, KERN_BUF, CTL_EOL); 1928 } 1929 1930 static void 1931 sysctl_vm_buf_setup(void) 1932 { 1933 1934 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL, 1935 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 1936 CTLTYPE_INT, "bufcache", 1937 SYSCTL_DESCR("Percentage of physical memory to use for " 1938 "buffer cache"), 1939 sysctl_bufvm_update, 0, &bufcache, 0, 1940 CTL_VM, CTL_CREATE, CTL_EOL); 1941 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL, 1942 CTLFLAG_PERMANENT|CTLFLAG_READONLY, 1943 CTLTYPE_LONG, "bufmem", 1944 SYSCTL_DESCR("Amount of kernel memory used by buffer " 1945 "cache"), 1946 NULL, 0, &bufmem, 0, 1947 CTL_VM, CTL_CREATE, CTL_EOL); 1948 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL, 1949 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 1950 CTLTYPE_LONG, "bufmem_lowater", 1951 SYSCTL_DESCR("Minimum amount of kernel memory to " 1952 "reserve for buffer cache"), 1953 sysctl_bufvm_update, 0, &bufmem_lowater, 0, 1954 CTL_VM, CTL_CREATE, CTL_EOL); 1955 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL, 1956 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 1957 CTLTYPE_LONG, "bufmem_hiwater", 1958 SYSCTL_DESCR("Maximum amount of kernel memory to use " 1959 "for buffer cache"), 1960 sysctl_bufvm_update, 0, &bufmem_hiwater, 0, 1961 CTL_VM, CTL_CREATE, CTL_EOL); 1962 } 1963 1964 static int 1965 bufhash_stats(struct hashstat_sysctl *hs, bool fill) 1966 { 1967 buf_t *bp; 1968 uint64_t chain; 1969 1970 strlcpy(hs->hash_name, "bufhash", sizeof(hs->hash_name)); 1971 strlcpy(hs->hash_desc, "buffer hash", sizeof(hs->hash_desc)); 1972 if (!fill) 1973 return 0; 1974 1975 hs->hash_size = bufhash + 1; 1976 1977 for (size_t i = 0; i < hs->hash_size; i++) { 1978 chain = 0; 1979 1980 mutex_enter(&bufcache_lock); 1981 LIST_FOREACH(bp, &bufhashtbl[i], b_hash) { 1982 chain++; 1983 } 1984 mutex_exit(&bufcache_lock); 1985 1986 if (chain > 0) { 1987 hs->hash_used++; 1988 hs->hash_items += chain; 1989 if (chain > hs->hash_maxchain) 1990 hs->hash_maxchain = chain; 1991 } 1992 preempt_point(); 1993 } 1994 1995 return 0; 1996 } 1997 1998 #ifdef DEBUG 1999 /* 2000 * Print out statistics on the current allocation of the buffer pool. 2001 * Can be enabled to print out on every ``sync'' by setting "syncprt" 2002 * in vfs_syscalls.c using sysctl. 2003 */ 2004 void 2005 vfs_bufstats(void) 2006 { 2007 int i, j, count; 2008 buf_t *bp; 2009 struct bqueue *dp; 2010 int counts[MAXBSIZE / MIN_PAGE_SIZE + 1]; 2011 static const char *bname[BQUEUES] = { "LOCKED", "LRU", "AGE" }; 2012 2013 for (dp = bufqueues, i = 0; dp < &bufqueues[BQUEUES]; dp++, i++) { 2014 count = 0; 2015 memset(counts, 0, sizeof(counts)); 2016 TAILQ_FOREACH(bp, &dp->bq_queue, b_freelist) { 2017 counts[bp->b_bufsize / PAGE_SIZE]++; 2018 count++; 2019 } 2020 printf("%s: total-%d", bname[i], count); 2021 for (j = 0; j <= MAXBSIZE / PAGE_SIZE; j++) 2022 if (counts[j] != 0) 2023 printf(", %d-%d", j * PAGE_SIZE, counts[j]); 2024 printf("\n"); 2025 } 2026 } 2027 #endif /* DEBUG */ 2028 2029 /* ------------------------------ */ 2030 2031 buf_t * 2032 getiobuf(struct vnode *vp, bool waitok) 2033 { 2034 buf_t *bp; 2035 2036 bp = pool_cache_get(bufio_cache, (waitok ? PR_WAITOK : PR_NOWAIT)); 2037 if (bp == NULL) 2038 return bp; 2039 2040 buf_init(bp); 2041 2042 if ((bp->b_vp = vp) != NULL) { 2043 bp->b_objlock = vp->v_interlock; 2044 } else { 2045 KASSERT(bp->b_objlock == &buffer_lock); 2046 } 2047 2048 return bp; 2049 } 2050 2051 void 2052 putiobuf(buf_t *bp) 2053 { 2054 2055 buf_destroy(bp); 2056 pool_cache_put(bufio_cache, bp); 2057 } 2058 2059 /* 2060 * nestiobuf_iodone: b_iodone callback for nested buffers. 2061 */ 2062 2063 void 2064 nestiobuf_iodone(buf_t *bp) 2065 { 2066 buf_t *mbp = bp->b_private; 2067 int error; 2068 int donebytes; 2069 2070 KASSERT(bp->b_bcount <= bp->b_bufsize); 2071 KASSERT(mbp != bp); 2072 2073 error = bp->b_error; 2074 if (bp->b_error == 0 && 2075 (bp->b_bcount < bp->b_bufsize || bp->b_resid > 0)) { 2076 /* 2077 * Not all got transferred, raise an error. We have no way to 2078 * propagate these conditions to mbp. 2079 */ 2080 error = EIO; 2081 } 2082 2083 donebytes = bp->b_bufsize; 2084 2085 putiobuf(bp); 2086 nestiobuf_done(mbp, donebytes, error); 2087 } 2088 2089 /* 2090 * nestiobuf_setup: setup a "nested" buffer. 2091 * 2092 * => 'mbp' is a "master" buffer which is being divided into sub pieces. 2093 * => 'bp' should be a buffer allocated by getiobuf. 2094 * => 'offset' is a byte offset in the master buffer. 2095 * => 'size' is a size in bytes of this nested buffer. 2096 */ 2097 2098 void 2099 nestiobuf_setup(buf_t *mbp, buf_t *bp, int offset, size_t size) 2100 { 2101 const int b_pass = mbp->b_flags & (B_READ|B_PHYS|B_RAW|B_MEDIA_FLAGS); 2102 struct vnode *vp = mbp->b_vp; 2103 2104 KASSERT(mbp->b_bcount >= offset + size); 2105 bp->b_vp = vp; 2106 bp->b_dev = mbp->b_dev; 2107 bp->b_objlock = mbp->b_objlock; 2108 bp->b_cflags = BC_BUSY; 2109 bp->b_flags = B_ASYNC | b_pass; 2110 bp->b_iodone = nestiobuf_iodone; 2111 bp->b_data = (char *)mbp->b_data + offset; 2112 bp->b_resid = bp->b_bcount = size; 2113 bp->b_bufsize = bp->b_bcount; 2114 bp->b_private = mbp; 2115 BIO_COPYPRIO(bp, mbp); 2116 if (BUF_ISWRITE(bp) && vp != NULL) { 2117 mutex_enter(vp->v_interlock); 2118 vp->v_numoutput++; 2119 mutex_exit(vp->v_interlock); 2120 } 2121 } 2122 2123 /* 2124 * nestiobuf_done: propagate completion to the master buffer. 2125 * 2126 * => 'donebytes' specifies how many bytes in the 'mbp' is completed. 2127 * => 'error' is an errno(2) that 'donebytes' has been completed with. 2128 */ 2129 2130 void 2131 nestiobuf_done(buf_t *mbp, int donebytes, int error) 2132 { 2133 2134 if (donebytes == 0) { 2135 return; 2136 } 2137 mutex_enter(mbp->b_objlock); 2138 KASSERT(mbp->b_resid >= donebytes); 2139 mbp->b_resid -= donebytes; 2140 if (error) 2141 mbp->b_error = error; 2142 if (mbp->b_resid == 0) { 2143 if (mbp->b_error) 2144 mbp->b_resid = mbp->b_bcount; 2145 mutex_exit(mbp->b_objlock); 2146 biodone(mbp); 2147 } else 2148 mutex_exit(mbp->b_objlock); 2149 } 2150 2151 void 2152 buf_init(buf_t *bp) 2153 { 2154 2155 cv_init(&bp->b_busy, "biolock"); 2156 cv_init(&bp->b_done, "biowait"); 2157 bp->b_dev = NODEV; 2158 bp->b_error = 0; 2159 bp->b_flags = 0; 2160 bp->b_cflags = 0; 2161 bp->b_oflags = 0; 2162 bp->b_objlock = &buffer_lock; 2163 bp->b_iodone = NULL; 2164 bp->b_dev = NODEV; 2165 bp->b_vnbufs.le_next = NOLIST; 2166 BIO_SETPRIO(bp, BPRIO_DEFAULT); 2167 } 2168 2169 void 2170 buf_destroy(buf_t *bp) 2171 { 2172 2173 cv_destroy(&bp->b_done); 2174 cv_destroy(&bp->b_busy); 2175 } 2176 2177 int 2178 bbusy(buf_t *bp, bool intr, int timo, kmutex_t *interlock) 2179 { 2180 int error; 2181 2182 KASSERT(mutex_owned(&bufcache_lock)); 2183 2184 SDT_PROBE4(io, kernel, , bbusy__start, bp, intr, timo, interlock); 2185 2186 if ((bp->b_cflags & BC_BUSY) != 0) { 2187 if (curlwp == uvm.pagedaemon_lwp) { 2188 error = EDEADLK; 2189 goto out; 2190 } 2191 bp->b_cflags |= BC_WANTED; 2192 if (interlock != NULL) 2193 mutex_exit(interlock); 2194 if (intr) { 2195 error = cv_timedwait_sig(&bp->b_busy, &bufcache_lock, 2196 timo); 2197 } else { 2198 error = cv_timedwait(&bp->b_busy, &bufcache_lock, 2199 timo); 2200 } 2201 /* 2202 * At this point the buffer may be gone: don't touch it 2203 * again. The caller needs to find it again and retry. 2204 */ 2205 if (interlock != NULL) 2206 mutex_enter(interlock); 2207 if (error == 0) 2208 error = EPASSTHROUGH; 2209 } else { 2210 bp->b_cflags |= BC_BUSY; 2211 error = 0; 2212 } 2213 2214 out: SDT_PROBE5(io, kernel, , bbusy__done, 2215 bp, intr, timo, interlock, error); 2216 return error; 2217 } 2218 2219 /* 2220 * Nothing outside this file should really need to know about nbuf, 2221 * but a few things still want to read it, so give them a way to do that. 2222 */ 2223 u_int 2224 buf_nbuf(void) 2225 { 2226 2227 return nbuf; 2228 }
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