1/* $NetBSD: vfs_bio.c,v 1.262 2016/10/28 20:17:27 jdolecek Exp $ */
2
3/*-
4 * Copyright (c) 2007, 2008, 2009 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 1.262 2016/10/28 20:17:27 jdolecek Exp $");
127
128#ifdef _KERNEL_OPT
129#include "opt_bufcache.h"
130#include "opt_dtrace.h"
131#endif
132
133#include <sys/param.h>
134#include <sys/systm.h>
135#include <sys/kernel.h>
136#include <sys/proc.h>
137#include <sys/buf.h>
138#include <sys/vnode.h>
139#include <sys/mount.h>
140#include <sys/resourcevar.h>
141#include <sys/sysctl.h>
142#include <sys/conf.h>
143#include <sys/kauth.h>
144#include <sys/fstrans.h>
145#include <sys/intr.h>
146#include <sys/cpu.h>
147#include <sys/wapbl.h>
148#include <sys/bitops.h>
149#include <sys/cprng.h>
150#include <sys/sdt.h>
151
152#include <uvm/uvm.h> /* extern struct uvm uvm */
153
154#include <miscfs/specfs/specdev.h>
155
156#ifndef BUFPAGES
157# define BUFPAGES 0
158#endif
159
160#ifdef BUFCACHE
161# if (BUFCACHE < 5) || (BUFCACHE > 95)
162# error BUFCACHE is not between 5 and 95
163# endif
164#else
165# define BUFCACHE 15
166#endif
167
168u_int nbuf; /* desired number of buffer headers */
169u_int bufpages = BUFPAGES; /* optional hardwired count */
170u_int bufcache = BUFCACHE; /* max % of RAM to use for buffer cache */
171
172/* Function prototypes */
173struct bqueue;
174
175static void buf_setwm(void);
176static int buf_trim(void);
177static void *bufpool_page_alloc(struct pool *, int);
178static void bufpool_page_free(struct pool *, void *);
179static buf_t *bio_doread(struct vnode *, daddr_t, int, int);
180static buf_t *getnewbuf(int, int, int);
181static int buf_lotsfree(void);
182static int buf_canrelease(void);
183static u_long buf_mempoolidx(u_long);
184static u_long buf_roundsize(u_long);
185static void *buf_alloc(size_t);
186static void buf_mrelease(void *, size_t);
187static void binsheadfree(buf_t *, struct bqueue *);
188static void binstailfree(buf_t *, struct bqueue *);
189#ifdef DEBUG
190static int checkfreelist(buf_t *, struct bqueue *, int);
191#endif
192static void biointr(void *);
193static void biodone2(buf_t *);
194static void bref(buf_t *);
195static void brele(buf_t *);
196static void sysctl_kern_buf_setup(void);
197static void sysctl_vm_buf_setup(void);
198
199/*
200 * Definitions for the buffer hash lists.
201 */
202#define BUFHASH(dvp, lbn) \
203 (&bufhashtbl[(((long)(dvp) >> 8) + (int)(lbn)) & bufhash])
204LIST_HEAD(bufhashhdr, buf) *bufhashtbl, invalhash;
205u_long bufhash;
206struct bqueue bufqueues[BQUEUES];
207
208static kcondvar_t needbuffer_cv;
209
210/*
211 * Buffer queue lock.
212 */
213kmutex_t bufcache_lock;
214kmutex_t buffer_lock;
215
216/* Software ISR for completed transfers. */
217static void *biodone_sih;
218
219/* Buffer pool for I/O buffers. */
220static pool_cache_t buf_cache;
221static pool_cache_t bufio_cache;
222
223#define MEMPOOL_INDEX_OFFSET (ilog2(DEV_BSIZE)) /* smallest pool is 512 bytes */
224#define NMEMPOOLS (ilog2(MAXBSIZE) - MEMPOOL_INDEX_OFFSET + 1)
225__CTASSERT((1 << (NMEMPOOLS + MEMPOOL_INDEX_OFFSET - 1)) == MAXBSIZE);
226
227/* Buffer memory pools */
228static struct pool bmempools[NMEMPOOLS];
229
230static struct vm_map *buf_map;
231
232/*
233 * Buffer memory pool allocator.
234 */
235static void *
236bufpool_page_alloc(struct pool *pp, int flags)
237{
238
239 return (void *)uvm_km_alloc(buf_map,
240 MAXBSIZE, MAXBSIZE,
241 ((flags & PR_WAITOK) ? 0 : UVM_KMF_NOWAIT|UVM_KMF_TRYLOCK)
242 | UVM_KMF_WIRED);
243}
244
245static void
246bufpool_page_free(struct pool *pp, void *v)
247{
248
249 uvm_km_free(buf_map, (vaddr_t)v, MAXBSIZE, UVM_KMF_WIRED);
250}
251
252static struct pool_allocator bufmempool_allocator = {
253 .pa_alloc = bufpool_page_alloc,
254 .pa_free = bufpool_page_free,
255 .pa_pagesz = MAXBSIZE,
256};
257
258/* Buffer memory management variables */
259u_long bufmem_valimit;
260u_long bufmem_hiwater;
261u_long bufmem_lowater;
262u_long bufmem;
263
264/*
265 * MD code can call this to set a hard limit on the amount
266 * of virtual memory used by the buffer cache.
267 */
268int
269buf_setvalimit(vsize_t sz)
270{
271
272 /* We need to accommodate at least NMEMPOOLS of MAXBSIZE each */
273 if (sz < NMEMPOOLS * MAXBSIZE)
274 return EINVAL;
275
276 bufmem_valimit = sz;
277 return 0;
278}
279
280static void
281buf_setwm(void)
282{
283
284 bufmem_hiwater = buf_memcalc();
285 /* lowater is approx. 2% of memory (with bufcache = 15) */
286#define BUFMEM_WMSHIFT 3
287#define BUFMEM_HIWMMIN (64 * 1024 << BUFMEM_WMSHIFT)
288 if (bufmem_hiwater < BUFMEM_HIWMMIN)
289 /* Ensure a reasonable minimum value */
290 bufmem_hiwater = BUFMEM_HIWMMIN;
291 bufmem_lowater = bufmem_hiwater >> BUFMEM_WMSHIFT;
292}
293
294#ifdef DEBUG
295int debug_verify_freelist = 0;
296static int
297checkfreelist(buf_t *bp, struct bqueue *dp, int ison)
298{
299 buf_t *b;
300
301 if (!debug_verify_freelist)
302 return 1;
303
304 TAILQ_FOREACH(b, &dp->bq_queue, b_freelist) {
305 if (b == bp)
306 return ison ? 1 : 0;
307 }
308
309 return ison ? 0 : 1;
310}
311#endif
312
313/*
314 * Insq/Remq for the buffer hash lists.
315 * Call with buffer queue locked.
316 */
317static void
318binsheadfree(buf_t *bp, struct bqueue *dp)
319{
320
321 KASSERT(mutex_owned(&bufcache_lock));
322 KASSERT(bp->b_freelistindex == -1);
323 TAILQ_INSERT_HEAD(&dp->bq_queue, bp, b_freelist);
324 dp->bq_bytes += bp->b_bufsize;
325 bp->b_freelistindex = dp - bufqueues;
326}
327
328static void
329binstailfree(buf_t *bp, struct bqueue *dp)
330{
331
332 KASSERT(mutex_owned(&bufcache_lock));
333 KASSERTMSG(bp->b_freelistindex == -1, "double free of buffer? "
334 "bp=%p, b_freelistindex=%d\n", bp, bp->b_freelistindex);
335 TAILQ_INSERT_TAIL(&dp->bq_queue, bp, b_freelist);
336 dp->bq_bytes += bp->b_bufsize;
337 bp->b_freelistindex = dp - bufqueues;
338}
339
340void
341bremfree(buf_t *bp)
342{
343 struct bqueue *dp;
344 int bqidx = bp->b_freelistindex;
345
346 KASSERT(mutex_owned(&bufcache_lock));
347
348 KASSERT(bqidx != -1);
349 dp = &bufqueues[bqidx];
350 KDASSERT(checkfreelist(bp, dp, 1));
351 KASSERT(dp->bq_bytes >= bp->b_bufsize);
352 TAILQ_REMOVE(&dp->bq_queue, bp, b_freelist);
353 dp->bq_bytes -= bp->b_bufsize;
354
355 /* For the sysctl helper. */
356 if (bp == dp->bq_marker)
357 dp->bq_marker = NULL;
358
359#if defined(DIAGNOSTIC)
360 bp->b_freelistindex = -1;
361#endif /* defined(DIAGNOSTIC) */
362}
363
364/*
365 * Add a reference to an buffer structure that came from buf_cache.
366 */
367static inline void
368bref(buf_t *bp)
369{
370
371 KASSERT(mutex_owned(&bufcache_lock));
372 KASSERT(bp->b_refcnt > 0);
373
374 bp->b_refcnt++;
375}
376
377/*
378 * Free an unused buffer structure that came from buf_cache.
379 */
380static inline void
381brele(buf_t *bp)
382{
383
384 KASSERT(mutex_owned(&bufcache_lock));
385 KASSERT(bp->b_refcnt > 0);
386
387 if (bp->b_refcnt-- == 1) {
388 buf_destroy(bp);
389#ifdef DEBUG
390 memset((char *)bp, 0, sizeof(*bp));
391#endif
392 pool_cache_put(buf_cache, bp);
393 }
394}
395
396/*
397 * note that for some ports this is used by pmap bootstrap code to
398 * determine kva size.
399 */
400u_long
401buf_memcalc(void)
402{
403 u_long n;
404 vsize_t mapsz = 0;
405
406 /*
407 * Determine the upper bound of memory to use for buffers.
408 *
409 * - If bufpages is specified, use that as the number
410 * pages.
411 *
412 * - Otherwise, use bufcache as the percentage of
413 * physical memory.
414 */
415 if (bufpages != 0) {
416 n = bufpages;
417 } else {
418 if (bufcache < 5) {
419 printf("forcing bufcache %d -> 5", bufcache);
420 bufcache = 5;
421 }
422 if (bufcache > 95) {
423 printf("forcing bufcache %d -> 95", bufcache);
424 bufcache = 95;
425 }
426 if (buf_map != NULL)
427 mapsz = vm_map_max(buf_map) - vm_map_min(buf_map);
428 n = calc_cache_size(mapsz, bufcache,
429 (buf_map != kernel_map) ? 100 : BUFCACHE_VA_MAXPCT)
430 / PAGE_SIZE;
431 }
432
433 n <<= PAGE_SHIFT;
434 if (bufmem_valimit != 0 && n > bufmem_valimit)
435 n = bufmem_valimit;
436
437 return (n);
438}
439
440/*
441 * Initialize buffers and hash links for buffers.
442 */
443void
444bufinit(void)
445{
446 struct bqueue *dp;
447 int use_std;
448 u_int i;
449
450 biodone_vfs = biodone;
451
452 mutex_init(&bufcache_lock, MUTEX_DEFAULT, IPL_NONE);
453 mutex_init(&buffer_lock, MUTEX_DEFAULT, IPL_NONE);
454 cv_init(&needbuffer_cv, "needbuf");
455
456 if (bufmem_valimit != 0) {
457 vaddr_t minaddr = 0, maxaddr;
458 buf_map = uvm_km_suballoc(kernel_map, &minaddr, &maxaddr,
459 bufmem_valimit, 0, false, 0);
460 if (buf_map == NULL)
461 panic("bufinit: cannot allocate submap");
462 } else
463 buf_map = kernel_map;
464
465 /*
466 * Initialize buffer cache memory parameters.
467 */
468 bufmem = 0;
469 buf_setwm();
470
471 /* On "small" machines use small pool page sizes where possible */
472 use_std = (physmem < atop(16*1024*1024));
473
474 /*
475 * Also use them on systems that can map the pool pages using
476 * a direct-mapped segment.
477 */
478#ifdef PMAP_MAP_POOLPAGE
479 use_std = 1;
480#endif
481
482 buf_cache = pool_cache_init(sizeof(buf_t), 0, 0, 0,
483 "bufpl", NULL, IPL_SOFTBIO, NULL, NULL, NULL);
484 bufio_cache = pool_cache_init(sizeof(buf_t), 0, 0, 0,
485 "biopl", NULL, IPL_BIO, NULL, NULL, NULL);
486
487 for (i = 0; i < NMEMPOOLS; i++) {
488 struct pool_allocator *pa;
489 struct pool *pp = &bmempools[i];
490 u_int size = 1 << (i + MEMPOOL_INDEX_OFFSET);
491 char *name = kmem_alloc(8, KM_SLEEP); /* XXX: never freed */
492 if (__predict_false(size >= 1048576))
493 (void)snprintf(name, 8, "buf%um", size / 1048576);
494 else if (__predict_true(size >= 1024))
495 (void)snprintf(name, 8, "buf%uk", size / 1024);
496 else
497 (void)snprintf(name, 8, "buf%ub", size);
498 pa = (size <= PAGE_SIZE && use_std)
499 ? &pool_allocator_nointr
500 : &bufmempool_allocator;
501 pool_init(pp, size, 0, 0, 0, name, pa, IPL_NONE);
502 pool_setlowat(pp, 1);
503 pool_sethiwat(pp, 1);
504 }
505
506 /* Initialize the buffer queues */
507 for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++) {
508 TAILQ_INIT(&dp->bq_queue);
509 dp->bq_bytes = 0;
510 }
511
512 /*
513 * Estimate hash table size based on the amount of memory we
514 * intend to use for the buffer cache. The average buffer
515 * size is dependent on our clients (i.e. filesystems).
516 *
517 * For now, use an empirical 3K per buffer.
518 */
519 nbuf = (bufmem_hiwater / 1024) / 3;
520 bufhashtbl = hashinit(nbuf, HASH_LIST, true, &bufhash);
521
522 sysctl_kern_buf_setup();
523 sysctl_vm_buf_setup();
524}
525
526void
527bufinit2(void)
528{
529
530 biodone_sih = softint_establish(SOFTINT_BIO | SOFTINT_MPSAFE, biointr,
531 NULL);
532 if (biodone_sih == NULL)
533 panic("bufinit2: can't establish soft interrupt");
534}
535
536static int
537buf_lotsfree(void)
538{
539 u_long guess;
540
541 /* Always allocate if less than the low water mark. */
542 if (bufmem < bufmem_lowater)
543 return 1;
544
545 /* Never allocate if greater than the high water mark. */
546 if (bufmem > bufmem_hiwater)
547 return 0;
548
549 /* If there's anything on the AGE list, it should be eaten. */
550 if (TAILQ_FIRST(&bufqueues[BQ_AGE].bq_queue) != NULL)
551 return 0;
552
553 /*
554 * The probabily of getting a new allocation is inversely
555 * proportional to the current size of the cache above
556 * the low water mark. Divide the total first to avoid overflows
557 * in the product.
558 */
559 guess = cprng_fast32() % 16;
560
561 if ((bufmem_hiwater - bufmem_lowater) / 16 * guess >=
562 (bufmem - bufmem_lowater))
563 return 1;
564
565 /* Otherwise don't allocate. */
566 return 0;
567}
568
569/*
570 * Return estimate of bytes we think need to be
571 * released to help resolve low memory conditions.
572 *
573 * => called with bufcache_lock held.
574 */
575static int
576buf_canrelease(void)
577{
578 int pagedemand, ninvalid = 0;
579
580 KASSERT(mutex_owned(&bufcache_lock));
581
582 if (bufmem < bufmem_lowater)
583 return 0;
584
585 if (bufmem > bufmem_hiwater)
586 return bufmem - bufmem_hiwater;
587
588 ninvalid += bufqueues[BQ_AGE].bq_bytes;
589
590 pagedemand = uvmexp.freetarg - uvmexp.free;
591 if (pagedemand < 0)
592 return ninvalid;
593 return MAX(ninvalid, MIN(2 * MAXBSIZE,
594 MIN((bufmem - bufmem_lowater) / 16, pagedemand * PAGE_SIZE)));
595}
596
597/*
598 * Buffer memory allocation helper functions
599 */
600static u_long
601buf_mempoolidx(u_long size)
602{
603 u_int n = 0;
604
605 size -= 1;
606 size >>= MEMPOOL_INDEX_OFFSET;
607 while (size) {
608 size >>= 1;
609 n += 1;
610 }
611 if (n >= NMEMPOOLS)
612 panic("buf mem pool index %d", n);
613 return n;
614}
615
616static u_long
617buf_roundsize(u_long size)
618{
619 /* Round up to nearest power of 2 */
620 return (1 << (buf_mempoolidx(size) + MEMPOOL_INDEX_OFFSET));
621}
622
623static void *
624buf_alloc(size_t size)
625{
626 u_int n = buf_mempoolidx(size);
627 void *addr;
628
629 while (1) {
630 addr = pool_get(&bmempools[n], PR_NOWAIT);
631 if (addr != NULL)
632 break;
633
634 /* No memory, see if we can free some. If so, try again */
635 mutex_enter(&bufcache_lock);
636 if (buf_drain(1) > 0) {
637 mutex_exit(&bufcache_lock);
638 continue;
639 }
640
641 if (curlwp == uvm.pagedaemon_lwp) {
642 mutex_exit(&bufcache_lock);
643 return NULL;
644 }
645
646 /* Wait for buffers to arrive on the LRU queue */
647 cv_timedwait(&needbuffer_cv, &bufcache_lock, hz / 4);
648 mutex_exit(&bufcache_lock);
649 }
650
651 return addr;
652}
653
654static void
655buf_mrelease(void *addr, size_t size)
656{
657
658 pool_put(&bmempools[buf_mempoolidx(size)], addr);
659}
660
661/*
662 * bread()/breadn() helper.
663 */
664static buf_t *
665bio_doread(struct vnode *vp, daddr_t blkno, int size, int async)
666{
667 buf_t *bp;
668 struct mount *mp;
669
670 bp = getblk(vp, blkno, size, 0, 0);
671
672 /*
673 * getblk() may return NULL if we are the pagedaemon.
674 */
675 if (bp == NULL) {
676 KASSERT(curlwp == uvm.pagedaemon_lwp);
677 return NULL;
678 }
679
680 /*
681 * If buffer does not have data valid, start a read.
682 * Note that if buffer is BC_INVAL, getblk() won't return it.
683 * Therefore, it's valid if its I/O has completed or been delayed.
684 */
685 if (!ISSET(bp->b_oflags, (BO_DONE | BO_DELWRI))) {
686 /* Start I/O for the buffer. */
687 SET(bp->b_flags, B_READ | async);
688 if (async)
689 BIO_SETPRIO(bp, BPRIO_TIMELIMITED);
690 else
691 BIO_SETPRIO(bp, BPRIO_TIMECRITICAL);
692 VOP_STRATEGY(vp, bp);
693
694 /* Pay for the read. */
695 curlwp->l_ru.ru_inblock++;
696 } else if (async)
697 brelse(bp, 0);
698
699 if (vp->v_type == VBLK)
700 mp = spec_node_getmountedfs(vp);
701 else
702 mp = vp->v_mount;
703
704 /*
705 * Collect statistics on synchronous and asynchronous reads.
706 * Reads from block devices are charged to their associated
707 * filesystem (if any).
708 */
709 if (mp != NULL) {
710 if (async == 0)
711 mp->mnt_stat.f_syncreads++;
712 else
713 mp->mnt_stat.f_asyncreads++;
714 }
715
716 return (bp);
717}
718
719/*
720 * Read a disk block.
721 * This algorithm described in Bach (p.54).
722 */
723int
724bread(struct vnode *vp, daddr_t blkno, int size, int flags, buf_t **bpp)
725{
726 buf_t *bp;
727 int error;
728
729 /* Get buffer for block. */
730 bp = *bpp = bio_doread(vp, blkno, size, 0);
731 if (bp == NULL)
732 return ENOMEM;
733
734 /* Wait for the read to complete, and return result. */
735 error = biowait(bp);
736 if (error == 0 && (flags & B_MODIFY) != 0)
737 error = fscow_run(bp, true);
738 if (error) {
739 brelse(bp, 0);
740 *bpp = NULL;
741 }
742
743 return error;
744}
745
746/*
747 * Read-ahead multiple disk blocks. The first is sync, the rest async.
748 * Trivial modification to the breada algorithm presented in Bach (p.55).
749 */
750int
751breadn(struct vnode *vp, daddr_t blkno, int size, daddr_t *rablks,
752 int *rasizes, int nrablks, int flags, buf_t **bpp)
753{
754 buf_t *bp;
755 int error, i;
756
757 bp = *bpp = bio_doread(vp, blkno, size, 0);
758 if (bp == NULL)
759 return ENOMEM;
760
761 /*
762 * For each of the read-ahead blocks, start a read, if necessary.
763 */
764 mutex_enter(&bufcache_lock);
765 for (i = 0; i < nrablks; i++) {
766 /* If it's in the cache, just go on to next one. */
767 if (incore(vp, rablks[i]))
768 continue;
769
770 /* Get a buffer for the read-ahead block */
771 mutex_exit(&bufcache_lock);
772 (void) bio_doread(vp, rablks[i], rasizes[i], B_ASYNC);
773 mutex_enter(&bufcache_lock);
774 }
775 mutex_exit(&bufcache_lock);
776
777 /* Otherwise, we had to start a read for it; wait until it's valid. */
778 error = biowait(bp);
779 if (error == 0 && (flags & B_MODIFY) != 0)
780 error = fscow_run(bp, true);
781 if (error) {
782 brelse(bp, 0);
783 *bpp = NULL;
784 }
785
786 return error;
787}
788
789/*
790 * Block write. Described in Bach (p.56)
791 */
792int
793bwrite(buf_t *bp)
794{
795 int rv, sync, wasdelayed;
796 struct vnode *vp;
797 struct mount *mp;
798
799 KASSERT(ISSET(bp->b_cflags, BC_BUSY));
800 KASSERT(!cv_has_waiters(&bp->b_done));
801
802 vp = bp->b_vp;
803
804 /*
805 * dholland 20160728 AFAICT vp==NULL must be impossible as it
806 * will crash upon reaching VOP_STRATEGY below... see further
807 * analysis on tech-kern.
808 */
809 KASSERTMSG(vp != NULL, "bwrite given buffer with null vnode");
810
811 if (vp != NULL) {
812 KASSERT(bp->b_objlock == vp->v_interlock);
813 if (vp->v_type == VBLK)
814 mp = spec_node_getmountedfs(vp);
815 else
816 mp = vp->v_mount;
817 } else {
818 mp = NULL;
819 }
820
821 if (mp && mp->mnt_wapbl) {
822 if (bp->b_iodone != mp->mnt_wapbl_op->wo_wapbl_biodone) {
823 bdwrite(bp);
824 return 0;
825 }
826 }
827
828 /*
829 * Remember buffer type, to switch on it later. If the write was
830 * synchronous, but the file system was mounted with MNT_ASYNC,
831 * convert it to a delayed write.
832 * XXX note that this relies on delayed tape writes being converted
833 * to async, not sync writes (which is safe, but ugly).
834 */
835 sync = !ISSET(bp->b_flags, B_ASYNC);
836 if (sync && mp != NULL && ISSET(mp->mnt_flag, MNT_ASYNC)) {
837 bdwrite(bp);
838 return (0);
839 }
840
841 /*
842 * Collect statistics on synchronous and asynchronous writes.
843 * Writes to block devices are charged to their associated
844 * filesystem (if any).
845 */
846 if (mp != NULL) {
847 if (sync)
848 mp->mnt_stat.f_syncwrites++;
849 else
850 mp->mnt_stat.f_asyncwrites++;
851 }
852
853 /*
854 * Pay for the I/O operation and make sure the buf is on the correct
855 * vnode queue.
856 */
857 bp->b_error = 0;
858 wasdelayed = ISSET(bp->b_oflags, BO_DELWRI);
859 CLR(bp->b_flags, B_READ);
860 if (wasdelayed) {
861 mutex_enter(&bufcache_lock);
862 mutex_enter(bp->b_objlock);
863 CLR(bp->b_oflags, BO_DONE | BO_DELWRI);
864 reassignbuf(bp, bp->b_vp);
865 mutex_exit(&bufcache_lock);
866 } else {
867 curlwp->l_ru.ru_oublock++;
868 mutex_enter(bp->b_objlock);
869 CLR(bp->b_oflags, BO_DONE | BO_DELWRI);
870 }
871 if (vp != NULL)
872 vp->v_numoutput++;
873 mutex_exit(bp->b_objlock);
874
875 /* Initiate disk write. */
876 if (sync)
877 BIO_SETPRIO(bp, BPRIO_TIMECRITICAL);
878 else
879 BIO_SETPRIO(bp, BPRIO_TIMELIMITED);
880
881 VOP_STRATEGY(vp, bp);
882
883 if (sync) {
884 /* If I/O was synchronous, wait for it to complete. */
885 rv = biowait(bp);
886
887 /* Release the buffer. */
888 brelse(bp, 0);
889
890 return (rv);
891 } else {
892 return (0);
893 }
894}
895
896int
897vn_bwrite(void *v)
898{
899 struct vop_bwrite_args *ap = v;
900
901 return (bwrite(ap->a_bp));
902}
903
904/*
905 * Delayed write.
906 *
907 * The buffer is marked dirty, but is not queued for I/O.
908 * This routine should be used when the buffer is expected
909 * to be modified again soon, typically a small write that
910 * partially fills a buffer.
911 *
912 * NB: magnetic tapes cannot be delayed; they must be
913 * written in the order that the writes are requested.
914 *
915 * Described in Leffler, et al. (pp. 208-213).
916 */
917void
918bdwrite(buf_t *bp)
919{
920
921 KASSERT(bp->b_vp == NULL || bp->b_vp->v_tag != VT_UFS ||
922 bp->b_vp->v_type == VBLK || ISSET(bp->b_flags, B_COWDONE));
923 KASSERT(ISSET(bp->b_cflags, BC_BUSY));
924 KASSERT(!cv_has_waiters(&bp->b_done));
925
926 /* If this is a tape block, write the block now. */
927 if (bdev_type(bp->b_dev) == D_TAPE) {
928 bawrite(bp);
929 return;
930 }
931
932 if (wapbl_vphaswapbl(bp->b_vp)) {
933 struct mount *mp = wapbl_vptomp(bp->b_vp);
934
935 if (bp->b_iodone != mp->mnt_wapbl_op->wo_wapbl_biodone) {
936 WAPBL_ADD_BUF(mp, bp);
937 }
938 }
939
940 /*
941 * If the block hasn't been seen before:
942 * (1) Mark it as having been seen,
943 * (2) Charge for the write,
944 * (3) Make sure it's on its vnode's correct block list.
945 */
946 KASSERT(bp->b_vp == NULL || bp->b_objlock == bp->b_vp->v_interlock);
947
948 if (!ISSET(bp->b_oflags, BO_DELWRI)) {
949 mutex_enter(&bufcache_lock);
950 mutex_enter(bp->b_objlock);
951 SET(bp->b_oflags, BO_DELWRI);
952 curlwp->l_ru.ru_oublock++;
953 reassignbuf(bp, bp->b_vp);
954 mutex_exit(&bufcache_lock);
955 } else {
956 mutex_enter(bp->b_objlock);
957 }
958 /* Otherwise, the "write" is done, so mark and release the buffer. */
959 CLR(bp->b_oflags, BO_DONE);
960 mutex_exit(bp->b_objlock);
961
962 brelse(bp, 0);
963}
964
965/*
966 * Asynchronous block write; just an asynchronous bwrite().
967 */
968void
969bawrite(buf_t *bp)
970{
971
972 KASSERT(ISSET(bp->b_cflags, BC_BUSY));
973 KASSERT(bp->b_vp != NULL);
974
975 SET(bp->b_flags, B_ASYNC);
976 VOP_BWRITE(bp->b_vp, bp);
977}
978
979/*
980 * Release a buffer on to the free lists.
981 * Described in Bach (p. 46).
982 */
983void
984brelsel(buf_t *bp, int set)
985{
986 struct bqueue *bufq;
987 struct vnode *vp;
988
989 KASSERT(bp != NULL);
990 KASSERT(mutex_owned(&bufcache_lock));
991 KASSERT(!cv_has_waiters(&bp->b_done));
992 KASSERT(bp->b_refcnt > 0);
993
994 SET(bp->b_cflags, set);
995
996 KASSERT(ISSET(bp->b_cflags, BC_BUSY));
997 KASSERT(bp->b_iodone == NULL);
998
999 /* Wake up any processes waiting for any buffer to become free. */
1000 cv_signal(&needbuffer_cv);
1001
1002 /* Wake up any proceeses waiting for _this_ buffer to become free */
1003 if (ISSET(bp->b_cflags, BC_WANTED))
1004 CLR(bp->b_cflags, BC_WANTED|BC_AGE);
1005
1006 /* If it's clean clear the copy-on-write flag. */
1007 if (ISSET(bp->b_flags, B_COWDONE)) {
1008 mutex_enter(bp->b_objlock);
1009 if (!ISSET(bp->b_oflags, BO_DELWRI))
1010 CLR(bp->b_flags, B_COWDONE);
1011 mutex_exit(bp->b_objlock);
1012 }
1013
1014 /*
1015 * Determine which queue the buffer should be on, then put it there.
1016 */
1017
1018 /* If it's locked, don't report an error; try again later. */
1019 if (ISSET(bp->b_flags, B_LOCKED))
1020 bp->b_error = 0;
1021
1022 /* If it's not cacheable, or an error, mark it invalid. */
1023 if (ISSET(bp->b_cflags, BC_NOCACHE) || bp->b_error != 0)
1024 SET(bp->b_cflags, BC_INVAL);
1025
1026 if (ISSET(bp->b_cflags, BC_VFLUSH)) {
1027 /*
1028 * This is a delayed write buffer that was just flushed to
1029 * disk. It is still on the LRU queue. If it's become
1030 * invalid, then we need to move it to a different queue;
1031 * otherwise leave it in its current position.
1032 */
1033 CLR(bp->b_cflags, BC_VFLUSH);
1034 if (!ISSET(bp->b_cflags, BC_INVAL|BC_AGE) &&
1035 !ISSET(bp->b_flags, B_LOCKED) && bp->b_error == 0) {
1036 KDASSERT(checkfreelist(bp, &bufqueues[BQ_LRU], 1));
1037 goto already_queued;
1038 } else {
1039 bremfree(bp);
1040 }
1041 }
1042
1043 KDASSERT(checkfreelist(bp, &bufqueues[BQ_AGE], 0));
1044 KDASSERT(checkfreelist(bp, &bufqueues[BQ_LRU], 0));
1045 KDASSERT(checkfreelist(bp, &bufqueues[BQ_LOCKED], 0));
1046
1047 if ((bp->b_bufsize <= 0) || ISSET(bp->b_cflags, BC_INVAL)) {
1048 /*
1049 * If it's invalid or empty, dissociate it from its vnode
1050 * and put on the head of the appropriate queue.
1051 */
1052 if (ISSET(bp->b_flags, B_LOCKED)) {
1053 if (wapbl_vphaswapbl(vp = bp->b_vp)) {
1054 struct mount *mp = wapbl_vptomp(vp);
1055
1056 KASSERT(bp->b_iodone
1057 != mp->mnt_wapbl_op->wo_wapbl_biodone);
1058 WAPBL_REMOVE_BUF(mp, bp);
1059 }
1060 }
1061
1062 mutex_enter(bp->b_objlock);
1063 CLR(bp->b_oflags, BO_DONE|BO_DELWRI);
1064 if ((vp = bp->b_vp) != NULL) {
1065 KASSERT(bp->b_objlock == vp->v_interlock);
1066 reassignbuf(bp, bp->b_vp);
1067 brelvp(bp);
1068 mutex_exit(vp->v_interlock);
1069 } else {
1070 KASSERT(bp->b_objlock == &buffer_lock);
1071 mutex_exit(bp->b_objlock);
1072 }
1073
1074 if (bp->b_bufsize <= 0)
1075 /* no data */
1076 goto already_queued;
1077 else
1078 /* invalid data */
1079 bufq = &bufqueues[BQ_AGE];
1080 binsheadfree(bp, bufq);
1081 } else {
1082 /*
1083 * It has valid data. Put it on the end of the appropriate
1084 * queue, so that it'll stick around for as long as possible.
1085 * If buf is AGE, but has dependencies, must put it on last
1086 * bufqueue to be scanned, ie LRU. This protects against the
1087 * livelock where BQ_AGE only has buffers with dependencies,
1088 * and we thus never get to the dependent buffers in BQ_LRU.
1089 */
1090 if (ISSET(bp->b_flags, B_LOCKED)) {
1091 /* locked in core */
1092 bufq = &bufqueues[BQ_LOCKED];
1093 } else if (!ISSET(bp->b_cflags, BC_AGE)) {
1094 /* valid data */
1095 bufq = &bufqueues[BQ_LRU];
1096 } else {
1097 /* stale but valid data */
1098 bufq = &bufqueues[BQ_AGE];
1099 }
1100 binstailfree(bp, bufq);
1101 }
1102already_queued:
1103 /* Unlock the buffer. */
1104 CLR(bp->b_cflags, BC_AGE|BC_BUSY|BC_NOCACHE);
1105 CLR(bp->b_flags, B_ASYNC);
1106 cv_broadcast(&bp->b_busy);
1107
1108 if (bp->b_bufsize <= 0)
1109 brele(bp);
1110}
1111
1112void
1113brelse(buf_t *bp, int set)
1114{
1115
1116 mutex_enter(&bufcache_lock);
1117 brelsel(bp, set);
1118 mutex_exit(&bufcache_lock);
1119}
1120
1121/*
1122 * Determine if a block is in the cache.
1123 * Just look on what would be its hash chain. If it's there, return
1124 * a pointer to it, unless it's marked invalid. If it's marked invalid,
1125 * we normally don't return the buffer, unless the caller explicitly
1126 * wants us to.
1127 */
1128buf_t *
1129incore(struct vnode *vp, daddr_t blkno)
1130{
1131 buf_t *bp;
1132
1133 KASSERT(mutex_owned(&bufcache_lock));
1134
1135 /* Search hash chain */
1136 LIST_FOREACH(bp, BUFHASH(vp, blkno), b_hash) {
1137 if (bp->b_lblkno == blkno && bp->b_vp == vp &&
1138 !ISSET(bp->b_cflags, BC_INVAL)) {
1139 KASSERT(bp->b_objlock == vp->v_interlock);
1140 return (bp);
1141 }
1142 }
1143
1144 return (NULL);
1145}
1146
1147/*
1148 * Get a block of requested size that is associated with
1149 * a given vnode and block offset. If it is found in the
1150 * block cache, mark it as having been found, make it busy
1151 * and return it. Otherwise, return an empty block of the
1152 * correct size. It is up to the caller to insure that the
1153 * cached blocks be of the correct size.
1154 */
1155buf_t *
1156getblk(struct vnode *vp, daddr_t blkno, int size, int slpflag, int slptimeo)
1157{
1158 int err, preserve;
1159 buf_t *bp;
1160
1161 mutex_enter(&bufcache_lock);
1162 loop:
1163 bp = incore(vp, blkno);
1164 if (bp != NULL) {
1165 err = bbusy(bp, ((slpflag & PCATCH) != 0), slptimeo, NULL);
1166 if (err != 0) {
1167 if (err == EPASSTHROUGH)
1168 goto loop;
1169 mutex_exit(&bufcache_lock);
1170 return (NULL);
1171 }
1172 KASSERT(!cv_has_waiters(&bp->b_done));
1173#ifdef DIAGNOSTIC
1174 if (ISSET(bp->b_oflags, BO_DONE|BO_DELWRI) &&
1175 bp->b_bcount < size && vp->v_type != VBLK)
1176 panic("getblk: block size invariant failed");
1177#endif
1178 bremfree(bp);
1179 preserve = 1;
1180 } else {
1181 if ((bp = getnewbuf(slpflag, slptimeo, 0)) == NULL)
1182 goto loop;
1183
1184 if (incore(vp, blkno) != NULL) {
1185 /* The block has come into memory in the meantime. */
1186 brelsel(bp, 0);
1187 goto loop;
1188 }
1189
1190 LIST_INSERT_HEAD(BUFHASH(vp, blkno), bp, b_hash);
1191 bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = blkno;
1192 mutex_enter(vp->v_interlock);
1193 bgetvp(vp, bp);
1194 mutex_exit(vp->v_interlock);
1195 preserve = 0;
1196 }
1197 mutex_exit(&bufcache_lock);
1198
1199 /*
1200 * LFS can't track total size of B_LOCKED buffer (locked_queue_bytes)
1201 * if we re-size buffers here.
1202 */
1203 if (ISSET(bp->b_flags, B_LOCKED)) {
1204 KASSERT(bp->b_bufsize >= size);
1205 } else {
1206 if (allocbuf(bp, size, preserve)) {
1207 mutex_enter(&bufcache_lock);
1208 LIST_REMOVE(bp, b_hash);
1209 mutex_exit(&bufcache_lock);
1210 brelse(bp, BC_INVAL);
1211 return NULL;
1212 }
1213 }
1214 BIO_SETPRIO(bp, BPRIO_DEFAULT);
1215 return (bp);
1216}
1217
1218/*
1219 * Get an empty, disassociated buffer of given size.
1220 */
1221buf_t *
1222geteblk(int size)
1223{
1224 buf_t *bp;
1225 int error __diagused;
1226
1227 mutex_enter(&bufcache_lock);
1228 while ((bp = getnewbuf(0, 0, 0)) == NULL)
1229 ;
1230
1231 SET(bp->b_cflags, BC_INVAL);
1232 LIST_INSERT_HEAD(&invalhash, bp, b_hash);
1233 mutex_exit(&bufcache_lock);
1234 BIO_SETPRIO(bp, BPRIO_DEFAULT);
1235 error = allocbuf(bp, size, 0);
1236 KASSERT(error == 0);
1237 return (bp);
1238}
1239
1240/*
1241 * Expand or contract the actual memory allocated to a buffer.
1242 *
1243 * If the buffer shrinks, data is lost, so it's up to the
1244 * caller to have written it out *first*; this routine will not
1245 * start a write. If the buffer grows, it's the callers
1246 * responsibility to fill out the buffer's additional contents.
1247 */
1248int
1249allocbuf(buf_t *bp, int size, int preserve)
1250{
1251 void *addr;
1252 vsize_t oldsize, desired_size;
1253 int oldcount;
1254 int delta;
1255
1256 desired_size = buf_roundsize(size);
1257 if (desired_size > MAXBSIZE)
1258 printf("allocbuf: buffer larger than MAXBSIZE requested");
1259
1260 oldcount = bp->b_bcount;
1261
1262 bp->b_bcount = size;
1263
1264 oldsize = bp->b_bufsize;
1265 if (oldsize == desired_size) {
1266 /*
1267 * Do not short cut the WAPBL resize, as the buffer length
1268 * could still have changed and this would corrupt the
1269 * tracking of the transaction length.
1270 */
1271 goto out;
1272 }
1273
1274 /*
1275 * If we want a buffer of a different size, re-allocate the
1276 * buffer's memory; copy old content only if needed.
1277 */
1278 addr = buf_alloc(desired_size);
1279 if (addr == NULL)
1280 return ENOMEM;
1281 if (preserve)
1282 memcpy(addr, bp->b_data, MIN(oldsize,desired_size));
1283 if (bp->b_data != NULL)
1284 buf_mrelease(bp->b_data, oldsize);
1285 bp->b_data = addr;
1286 bp->b_bufsize = desired_size;
1287
1288 /*
1289 * Update overall buffer memory counter (protected by bufcache_lock)
1290 */
1291 delta = (long)desired_size - (long)oldsize;
1292
1293 mutex_enter(&bufcache_lock);
1294 if ((bufmem += delta) > bufmem_hiwater) {
1295 /*
1296 * Need to trim overall memory usage.
1297 */
1298 while (buf_canrelease()) {
1299 if (curcpu()->ci_schedstate.spc_flags &
1300 SPCF_SHOULDYIELD) {
1301 mutex_exit(&bufcache_lock);
1302 preempt();
1303 mutex_enter(&bufcache_lock);
1304 }
1305 if (buf_trim() == 0)
1306 break;
1307 }
1308 }
1309 mutex_exit(&bufcache_lock);
1310
1311 out:
1312 if (wapbl_vphaswapbl(bp->b_vp))
1313 WAPBL_RESIZE_BUF(wapbl_vptomp(bp->b_vp), bp, oldsize, oldcount);
1314
1315 return 0;
1316}
1317
1318/*
1319 * Find a buffer which is available for use.
1320 * Select something from a free list.
1321 * Preference is to AGE list, then LRU list.
1322 *
1323 * Called with the buffer queues locked.
1324 * Return buffer locked.
1325 */
1326buf_t *
1327getnewbuf(int slpflag, int slptimeo, int from_bufq)
1328{
1329 buf_t *bp;
1330 struct vnode *vp;
1331
1332 start:
1333 KASSERT(mutex_owned(&bufcache_lock));
1334
1335 /*
1336 * Get a new buffer from the pool.
1337 */
1338 if (!from_bufq && buf_lotsfree()) {
1339 mutex_exit(&bufcache_lock);
1340 bp = pool_cache_get(buf_cache, PR_NOWAIT);
1341 if (bp != NULL) {
1342 memset((char *)bp, 0, sizeof(*bp));
1343 buf_init(bp);
1344 SET(bp->b_cflags, BC_BUSY); /* mark buffer busy */
1345 mutex_enter(&bufcache_lock);
1346#if defined(DIAGNOSTIC)
1347 bp->b_freelistindex = -1;
1348#endif /* defined(DIAGNOSTIC) */
1349 return (bp);
1350 }
1351 mutex_enter(&bufcache_lock);
1352 }
1353
1354 KASSERT(mutex_owned(&bufcache_lock));
1355 if ((bp = TAILQ_FIRST(&bufqueues[BQ_AGE].bq_queue)) != NULL ||
1356 (bp = TAILQ_FIRST(&bufqueues[BQ_LRU].bq_queue)) != NULL) {
1357 KASSERT(!ISSET(bp->b_cflags, BC_BUSY) || ISSET(bp->b_cflags, BC_VFLUSH));
1358 bremfree(bp);
1359
1360 /* Buffer is no longer on free lists. */
1361 SET(bp->b_cflags, BC_BUSY);
1362 } else {
1363 /*
1364 * XXX: !from_bufq should be removed.
1365 */
1366 if (!from_bufq || curlwp != uvm.pagedaemon_lwp) {
1367 /* wait for a free buffer of any kind */
1368 if ((slpflag & PCATCH) != 0)
1369 (void)cv_timedwait_sig(&needbuffer_cv,
1370 &bufcache_lock, slptimeo);
1371 else
1372 (void)cv_timedwait(&needbuffer_cv,
1373 &bufcache_lock, slptimeo);
1374 }
1375 return (NULL);
1376 }
1377
1378#ifdef DIAGNOSTIC
1379 if (bp->b_bufsize <= 0)
1380 panic("buffer %p: on queue but empty", bp);
1381#endif
1382
1383 if (ISSET(bp->b_cflags, BC_VFLUSH)) {
1384 /*
1385 * This is a delayed write buffer being flushed to disk. Make
1386 * sure it gets aged out of the queue when it's finished, and
1387 * leave it off the LRU queue.
1388 */
1389 CLR(bp->b_cflags, BC_VFLUSH);
1390 SET(bp->b_cflags, BC_AGE);
1391 goto start;
1392 }
1393
1394 KASSERT(ISSET(bp->b_cflags, BC_BUSY));
1395 KASSERT(bp->b_refcnt > 0);
1396 KASSERT(!cv_has_waiters(&bp->b_done));
1397
1398 /*
1399 * If buffer was a delayed write, start it and return NULL
1400 * (since we might sleep while starting the write).
1401 */
1402 if (ISSET(bp->b_oflags, BO_DELWRI)) {
1403 /*
1404 * This buffer has gone through the LRU, so make sure it gets
1405 * reused ASAP.
1406 */
1407 SET(bp->b_cflags, BC_AGE);
1408 mutex_exit(&bufcache_lock);
1409 bawrite(bp);
1410 mutex_enter(&bufcache_lock);
1411 return (NULL);
1412 }
1413
1414 vp = bp->b_vp;
1415
1416 /* clear out various other fields */
1417 bp->b_cflags = BC_BUSY;
1418 bp->b_oflags = 0;
1419 bp->b_flags = 0;
1420 bp->b_dev = NODEV;
1421 bp->b_blkno = 0;
1422 bp->b_lblkno = 0;
1423 bp->b_rawblkno = 0;
1424 bp->b_iodone = 0;
1425 bp->b_error = 0;
1426 bp->b_resid = 0;
1427 bp->b_bcount = 0;
1428
1429 LIST_REMOVE(bp, b_hash);
1430
1431 /* Disassociate us from our vnode, if we had one... */
1432 if (vp != NULL) {
1433 mutex_enter(vp->v_interlock);
1434 brelvp(bp);
1435 mutex_exit(vp->v_interlock);
1436 }
1437
1438 return (bp);
1439}
1440
1441/*
1442 * Attempt to free an aged buffer off the queues.
1443 * Called with queue lock held.
1444 * Returns the amount of buffer memory freed.
1445 */
1446static int
1447buf_trim(void)
1448{
1449 buf_t *bp;
1450 long size;
1451
1452 KASSERT(mutex_owned(&bufcache_lock));
1453
1454 /* Instruct getnewbuf() to get buffers off the queues */
1455 if ((bp = getnewbuf(PCATCH, 1, 1)) == NULL)
1456 return 0;
1457
1458 KASSERT((bp->b_cflags & BC_WANTED) == 0);
1459 size = bp->b_bufsize;
1460 bufmem -= size;
1461 if (size > 0) {
1462 buf_mrelease(bp->b_data, size);
1463 bp->b_bcount = bp->b_bufsize = 0;
1464 }
1465 /* brelse() will return the buffer to the global buffer pool */
1466 brelsel(bp, 0);
1467 return size;
1468}
1469
1470int
1471buf_drain(int n)
1472{
1473 int size = 0, sz;
1474
1475 KASSERT(mutex_owned(&bufcache_lock));
1476
1477 while (size < n && bufmem > bufmem_lowater) {
1478 sz = buf_trim();
1479 if (sz <= 0)
1480 break;
1481 size += sz;
1482 }
1483
1484 return size;
1485}
1486
1487SDT_PROVIDER_DEFINE(io);
1488
1489SDT_PROBE_DEFINE1(io, kernel, , wait__start, "struct buf *"/*bp*/);
1490SDT_PROBE_DEFINE1(io, kernel, , wait__done, "struct buf *"/*bp*/);
1491
1492/*
1493 * Wait for operations on the buffer to complete.
1494 * When they do, extract and return the I/O's error value.
1495 */
1496int
1497biowait(buf_t *bp)
1498{
1499
1500 KASSERT(ISSET(bp->b_cflags, BC_BUSY));
1501 KASSERT(bp->b_refcnt > 0);
1502
1503 SDT_PROBE1(io, kernel, , wait__start, bp);
1504
1505 mutex_enter(bp->b_objlock);
1506 while (!ISSET(bp->b_oflags, BO_DONE | BO_DELWRI))
1507 cv_wait(&bp->b_done, bp->b_objlock);
1508 mutex_exit(bp->b_objlock);
1509
1510 SDT_PROBE1(io, kernel, , wait__done, bp);
1511
1512 return bp->b_error;
1513}
1514
1515/*
1516 * Mark I/O complete on a buffer.
1517 *
1518 * If a callback has been requested, e.g. the pageout
1519 * daemon, do so. Otherwise, awaken waiting processes.
1520 *
1521 * [ Leffler, et al., says on p.247:
1522 * "This routine wakes up the blocked process, frees the buffer
1523 * for an asynchronous write, or, for a request by the pagedaemon
1524 * process, invokes a procedure specified in the buffer structure" ]
1525 *
1526 * In real life, the pagedaemon (or other system processes) wants
1527 * to do async stuff to, and doesn't want the buffer brelse()'d.
1528 * (for swap pager, that puts swap buffers on the free lists (!!!),
1529 * for the vn device, that puts allocated buffers on the free lists!)
1530 */
1531void
1532biodone(buf_t *bp)
1533{
1534 int s;
1535
1536 KASSERT(!ISSET(bp->b_oflags, BO_DONE));
1537
1538 if (cpu_intr_p()) {
1539 /* From interrupt mode: defer to a soft interrupt. */
1540 s = splvm();
1541 TAILQ_INSERT_TAIL(&curcpu()->ci_data.cpu_biodone, bp, b_actq);
1542 softint_schedule(biodone_sih);
1543 splx(s);
1544 } else {
1545 /* Process now - the buffer may be freed soon. */
1546 biodone2(bp);
1547 }
1548}
1549
1550SDT_PROBE_DEFINE1(io, kernel, , done, "struct buf *"/*bp*/);
1551
1552static void
1553biodone2(buf_t *bp)
1554{
1555 void (*callout)(buf_t *);
1556
1557 SDT_PROBE1(io, kernel, ,done, bp);
1558
1559 mutex_enter(bp->b_objlock);
1560 /* Note that the transfer is done. */
1561 if (ISSET(bp->b_oflags, BO_DONE))
1562 panic("biodone2 already");
1563 CLR(bp->b_flags, B_COWDONE);
1564 SET(bp->b_oflags, BO_DONE);
1565 BIO_SETPRIO(bp, BPRIO_DEFAULT);
1566
1567 /* Wake up waiting writers. */
1568 if (!ISSET(bp->b_flags, B_READ))
1569 vwakeup(bp);
1570
1571 if ((callout = bp->b_iodone) != NULL) {
1572 /* Note callout done, then call out. */
1573 KASSERT(!cv_has_waiters(&bp->b_done));
1574 KERNEL_LOCK(1, NULL); /* XXXSMP */
1575 bp->b_iodone = NULL;
1576 mutex_exit(bp->b_objlock);
1577 (*callout)(bp);
1578 KERNEL_UNLOCK_ONE(NULL); /* XXXSMP */
1579 } else if (ISSET(bp->b_flags, B_ASYNC)) {
1580 /* If async, release. */
1581 KASSERT(!cv_has_waiters(&bp->b_done));
1582 mutex_exit(bp->b_objlock);
1583 brelse(bp, 0);
1584 } else {
1585 /* Otherwise just wake up waiters in biowait(). */
1586 cv_broadcast(&bp->b_done);
1587 mutex_exit(bp->b_objlock);
1588 }
1589}
1590
1591static void
1592biointr(void *cookie)
1593{
1594 struct cpu_info *ci;
1595 buf_t *bp;
1596 int s;
1597
1598 ci = curcpu();
1599
1600 while (!TAILQ_EMPTY(&ci->ci_data.cpu_biodone)) {
1601 KASSERT(curcpu() == ci);
1602
1603 s = splvm();
1604 bp = TAILQ_FIRST(&ci->ci_data.cpu_biodone);
1605 TAILQ_REMOVE(&ci->ci_data.cpu_biodone, bp, b_actq);
1606 splx(s);
1607
1608 biodone2(bp);
1609 }
1610}
1611
1612/*
1613 * Wait for all buffers to complete I/O
1614 * Return the number of "stuck" buffers.
1615 */
1616int
1617buf_syncwait(void)
1618{
1619 buf_t *bp;
1620 int iter, nbusy, nbusy_prev = 0, ihash;
1621
1622 for (iter = 0; iter < 20;) {
1623 mutex_enter(&bufcache_lock);
1624 nbusy = 0;
1625 for (ihash = 0; ihash < bufhash+1; ihash++) {
1626 LIST_FOREACH(bp, &bufhashtbl[ihash], b_hash) {
1627 if ((bp->b_cflags & (BC_BUSY|BC_INVAL)) == BC_BUSY)
1628 nbusy += ((bp->b_flags & B_READ) == 0);
1629 }
1630 }
1631 mutex_exit(&bufcache_lock);
1632
1633 if (nbusy == 0)
1634 break;
1635 if (nbusy_prev == 0)
1636 nbusy_prev = nbusy;
1637 printf("%d ", nbusy);
1638 kpause("bflush", false, MAX(1, hz / 25 * iter), NULL);
1639 if (nbusy >= nbusy_prev) /* we didn't flush anything */
1640 iter++;
1641 else
1642 nbusy_prev = nbusy;
1643 }
1644
1645 if (nbusy) {
1646#if defined(DEBUG) || defined(DEBUG_HALT_BUSY)
1647 printf("giving up\nPrinting vnodes for busy buffers\n");
1648 for (ihash = 0; ihash < bufhash+1; ihash++) {
1649 LIST_FOREACH(bp, &bufhashtbl[ihash], b_hash) {
1650 if ((bp->b_cflags & (BC_BUSY|BC_INVAL)) == BC_BUSY &&
1651 (bp->b_flags & B_READ) == 0)
1652 vprint(NULL, bp->b_vp);
1653 }
1654 }
1655#endif
1656 }
1657
1658 return nbusy;
1659}
1660
1661static void
1662sysctl_fillbuf(buf_t *i, struct buf_sysctl *o)
1663{
1664
1665 o->b_flags = i->b_flags | i->b_cflags | i->b_oflags;
1666 o->b_error = i->b_error;
1667 o->b_prio = i->b_prio;
1668 o->b_dev = i->b_dev;
1669 o->b_bufsize = i->b_bufsize;
1670 o->b_bcount = i->b_bcount;
1671 o->b_resid = i->b_resid;
1672 o->b_addr = PTRTOUINT64(i->b_data);
1673 o->b_blkno = i->b_blkno;
1674 o->b_rawblkno = i->b_rawblkno;
1675 o->b_iodone = PTRTOUINT64(i->b_iodone);
1676 o->b_proc = PTRTOUINT64(i->b_proc);
1677 o->b_vp = PTRTOUINT64(i->b_vp);
1678 o->b_saveaddr = PTRTOUINT64(i->b_saveaddr);
1679 o->b_lblkno = i->b_lblkno;
1680}
1681
1682#define KERN_BUFSLOP 20
1683static int
1684sysctl_dobuf(SYSCTLFN_ARGS)
1685{
1686 buf_t *bp;
1687 struct buf_sysctl bs;
1688 struct bqueue *bq;
1689 char *dp;
1690 u_int i, op, arg;
1691 size_t len, needed, elem_size, out_size;
1692 int error, elem_count, retries;
1693
1694 if (namelen == 1 && name[0] == CTL_QUERY)
1695 return (sysctl_query(SYSCTLFN_CALL(rnode)));
1696
1697 if (namelen != 4)
1698 return (EINVAL);
1699
1700 retries = 100;
1701 retry:
1702 dp = oldp;
1703 len = (oldp != NULL) ? *oldlenp : 0;
1704 op = name[0];
1705 arg = name[1];
1706 elem_size = name[2];
1707 elem_count = name[3];
1708 out_size = MIN(sizeof(bs), elem_size);
1709
1710 /*
1711 * at the moment, these are just "placeholders" to make the
1712 * API for retrieving kern.buf data more extensible in the
1713 * future.
1714 *
1715 * XXX kern.buf currently has "netbsd32" issues. hopefully
1716 * these will be resolved at a later point.
1717 */
1718 if (op != KERN_BUF_ALL || arg != KERN_BUF_ALL ||
1719 elem_size < 1 || elem_count < 0)
1720 return (EINVAL);
1721
1722 error = 0;
1723 needed = 0;
1724 sysctl_unlock();
1725 mutex_enter(&bufcache_lock);
1726 for (i = 0; i < BQUEUES; i++) {
1727 bq = &bufqueues[i];
1728 TAILQ_FOREACH(bp, &bq->bq_queue, b_freelist) {
1729 bq->bq_marker = bp;
1730 if (len >= elem_size && elem_count > 0) {
1731 sysctl_fillbuf(bp, &bs);
1732 mutex_exit(&bufcache_lock);
1733 error = copyout(&bs, dp, out_size);
1734 mutex_enter(&bufcache_lock);
1735 if (error)
1736 break;
1737 if (bq->bq_marker != bp) {
1738 /*
1739 * This sysctl node is only for
1740 * statistics. Retry; if the
1741 * queue keeps changing, then
1742 * bail out.
1743 */
1744 if (retries-- == 0) {
1745 error = EAGAIN;
1746 break;
1747 }
1748 mutex_exit(&bufcache_lock);
1749 sysctl_relock();
1750 goto retry;
1751 }
1752 dp += elem_size;
1753 len -= elem_size;
1754 }
1755 needed += elem_size;
1756 if (elem_count > 0 && elem_count != INT_MAX)
1757 elem_count--;
1758 }
1759 if (error != 0)
1760 break;
1761 }
1762 mutex_exit(&bufcache_lock);
1763 sysctl_relock();
1764
1765 *oldlenp = needed;
1766 if (oldp == NULL)
1767 *oldlenp += KERN_BUFSLOP * sizeof(buf_t);
1768
1769 return (error);
1770}
1771
1772static int
1773sysctl_bufvm_update(SYSCTLFN_ARGS)
1774{
1775 int error, rv;
1776 struct sysctlnode node;
1777 unsigned int temp_bufcache;
1778 unsigned long temp_water;
1779
1780 /* Take a copy of the supplied node and its data */
1781 node = *rnode;
1782 if (node.sysctl_data == &bufcache) {
1783 node.sysctl_data = &temp_bufcache;
1784 temp_bufcache = *(unsigned int *)rnode->sysctl_data;
1785 } else {
1786 node.sysctl_data = &temp_water;
1787 temp_water = *(unsigned long *)rnode->sysctl_data;
1788 }
1789
1790 /* Update the copy */
1791 error = sysctl_lookup(SYSCTLFN_CALL(&node));
1792 if (error || newp == NULL)
1793 return (error);
1794
1795 if (rnode->sysctl_data == &bufcache) {
1796 if (temp_bufcache > 100)
1797 return (EINVAL);
1798 bufcache = temp_bufcache;
1799 buf_setwm();
1800 } else if (rnode->sysctl_data == &bufmem_lowater) {
1801 if (bufmem_hiwater - temp_water < 16)
1802 return (EINVAL);
1803 bufmem_lowater = temp_water;
1804 } else if (rnode->sysctl_data == &bufmem_hiwater) {
1805 if (temp_water - bufmem_lowater < 16)
1806 return (EINVAL);
1807 bufmem_hiwater = temp_water;
1808 } else
1809 return (EINVAL);
1810
1811 /* Drain until below new high water mark */
1812 sysctl_unlock();
1813 mutex_enter(&bufcache_lock);
1814 while (bufmem > bufmem_hiwater) {
1815 rv = buf_drain((bufmem - bufmem_hiwater) / (2 * 1024));
1816 if (rv <= 0)
1817 break;
1818 }
1819 mutex_exit(&bufcache_lock);
1820 sysctl_relock();
1821
1822 return 0;
1823}
1824
1825static struct sysctllog *vfsbio_sysctllog;
1826
1827static void
1828sysctl_kern_buf_setup(void)
1829{
1830
1831 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL,
1832 CTLFLAG_PERMANENT,
1833 CTLTYPE_NODE, "buf",
1834 SYSCTL_DESCR("Kernel buffer cache information"),
1835 sysctl_dobuf, 0, NULL, 0,
1836 CTL_KERN, KERN_BUF, CTL_EOL);
1837}
1838
1839static void
1840sysctl_vm_buf_setup(void)
1841{
1842
1843 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL,
1844 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
1845 CTLTYPE_INT, "bufcache",
1846 SYSCTL_DESCR("Percentage of physical memory to use for "
1847 "buffer cache"),
1848 sysctl_bufvm_update, 0, &bufcache, 0,
1849 CTL_VM, CTL_CREATE, CTL_EOL);
1850 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL,
1851 CTLFLAG_PERMANENT|CTLFLAG_READONLY,
1852 CTLTYPE_LONG, "bufmem",
1853 SYSCTL_DESCR("Amount of kernel memory used by buffer "
1854 "cache"),
1855 NULL, 0, &bufmem, 0,
1856 CTL_VM, CTL_CREATE, CTL_EOL);
1857 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL,
1858 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
1859 CTLTYPE_LONG, "bufmem_lowater",
1860 SYSCTL_DESCR("Minimum amount of kernel memory to "
1861 "reserve for buffer cache"),
1862 sysctl_bufvm_update, 0, &bufmem_lowater, 0,
1863 CTL_VM, CTL_CREATE, CTL_EOL);
1864 sysctl_createv(&vfsbio_sysctllog, 0, NULL, NULL,
1865 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
1866 CTLTYPE_LONG, "bufmem_hiwater",
1867 SYSCTL_DESCR("Maximum amount of kernel memory to use "
1868 "for buffer cache"),
1869 sysctl_bufvm_update, 0, &bufmem_hiwater, 0,
1870 CTL_VM, CTL_CREATE, CTL_EOL);
1871}
1872
1873#ifdef DEBUG
1874/*
1875 * Print out statistics on the current allocation of the buffer pool.
1876 * Can be enabled to print out on every ``sync'' by setting "syncprt"
1877 * in vfs_syscalls.c using sysctl.
1878 */
1879void
1880vfs_bufstats(void)
1881{
1882 int i, j, count;
1883 buf_t *bp;
1884 struct bqueue *dp;
1885 int counts[MAXBSIZE / MIN_PAGE_SIZE + 1];
1886 static const char *bname[BQUEUES] = { "LOCKED", "LRU", "AGE" };
1887
1888 for (dp = bufqueues, i = 0; dp < &bufqueues[BQUEUES]; dp++, i++) {
1889 count = 0;
1890 memset(counts, 0, sizeof(counts));
1891 TAILQ_FOREACH(bp, &dp->bq_queue, b_freelist) {
1892 counts[bp->b_bufsize / PAGE_SIZE]++;
1893 count++;
1894 }
1895 printf("%s: total-%d", bname[i], count);
1896 for (j = 0; j <= MAXBSIZE / PAGE_SIZE; j++)
1897 if (counts[j] != 0)
1898 printf(", %d-%d", j * PAGE_SIZE, counts[j]);
1899 printf("\n");
1900 }
1901}
1902#endif /* DEBUG */
1903
1904/* ------------------------------ */
1905
1906buf_t *
1907getiobuf(struct vnode *vp, bool waitok)
1908{
1909 buf_t *bp;
1910
1911 bp = pool_cache_get(bufio_cache, (waitok ? PR_WAITOK : PR_NOWAIT));
1912 if (bp == NULL)
1913 return bp;
1914
1915 buf_init(bp);
1916
1917 if ((bp->b_vp = vp) == NULL)
1918 bp->b_objlock = &buffer_lock;
1919 else
1920 bp->b_objlock = vp->v_interlock;
1921
1922 return bp;
1923}
1924
1925void
1926putiobuf(buf_t *bp)
1927{
1928
1929 buf_destroy(bp);
1930 pool_cache_put(bufio_cache, bp);
1931}
1932
1933/*
1934 * nestiobuf_iodone: b_iodone callback for nested buffers.
1935 */
1936
1937void
1938nestiobuf_iodone(buf_t *bp)
1939{
1940 buf_t *mbp = bp->b_private;
1941 int error;
1942 int donebytes;
1943
1944 KASSERT(bp->b_bcount <= bp->b_bufsize);
1945 KASSERT(mbp != bp);
1946
1947 error = bp->b_error;
1948 if (bp->b_error == 0 &&
1949 (bp->b_bcount < bp->b_bufsize || bp->b_resid > 0)) {
1950 /*
1951 * Not all got transfered, raise an error. We have no way to
1952 * propagate these conditions to mbp.
1953 */
1954 error = EIO;
1955 }
1956
1957 donebytes = bp->b_bufsize;
1958
1959 putiobuf(bp);
1960 nestiobuf_done(mbp, donebytes, error);
1961}
1962
1963/*
1964 * nestiobuf_setup: setup a "nested" buffer.
1965 *
1966 * => 'mbp' is a "master" buffer which is being divided into sub pieces.
1967 * => 'bp' should be a buffer allocated by getiobuf.
1968 * => 'offset' is a byte offset in the master buffer.
1969 * => 'size' is a size in bytes of this nested buffer.
1970 */
1971
1972void
1973nestiobuf_setup(buf_t *mbp, buf_t *bp, int offset, size_t size)
1974{
1975 const int b_read = mbp->b_flags & B_READ;
1976 struct vnode *vp = mbp->b_vp;
1977
1978 KASSERT(mbp->b_bcount >= offset + size);
1979 bp->b_vp = vp;
1980 bp->b_dev = mbp->b_dev;
1981 bp->b_objlock = mbp->b_objlock;
1982 bp->b_cflags = BC_BUSY;
1983 bp->b_flags = B_ASYNC | b_read;
1984 bp->b_iodone = nestiobuf_iodone;
1985 bp->b_data = (char *)mbp->b_data + offset;
1986 bp->b_resid = bp->b_bcount = size;
1987 bp->b_bufsize = bp->b_bcount;
1988 bp->b_private = mbp;
1989 BIO_COPYPRIO(bp, mbp);
1990 if (!b_read && vp != NULL) {
1991 mutex_enter(vp->v_interlock);
1992 vp->v_numoutput++;
1993 mutex_exit(vp->v_interlock);
1994 }
1995}
1996
1997/*
1998 * nestiobuf_done: propagate completion to the master buffer.
1999 *
2000 * => 'donebytes' specifies how many bytes in the 'mbp' is completed.
2001 * => 'error' is an errno(2) that 'donebytes' has been completed with.
2002 */
2003
2004void
2005nestiobuf_done(buf_t *mbp, int donebytes, int error)
2006{
2007
2008 if (donebytes == 0) {
2009 return;
2010 }
2011 mutex_enter(mbp->b_objlock);
2012 KASSERT(mbp->b_resid >= donebytes);
2013 mbp->b_resid -= donebytes;
2014 if (error)
2015 mbp->b_error = error;
2016 if (mbp->b_resid == 0) {
2017 if (mbp->b_error)
2018 mbp->b_resid = mbp->b_bcount;
2019 mutex_exit(mbp->b_objlock);
2020 biodone(mbp);
2021 } else
2022 mutex_exit(mbp->b_objlock);
2023}
2024
2025void
2026buf_init(buf_t *bp)
2027{
2028
2029 cv_init(&bp->b_busy, "biolock");
2030 cv_init(&bp->b_done, "biowait");
2031 bp->b_dev = NODEV;
2032 bp->b_error = 0;
2033 bp->b_flags = 0;
2034 bp->b_cflags = 0;
2035 bp->b_oflags = 0;
2036 bp->b_objlock = &buffer_lock;
2037 bp->b_iodone = NULL;
2038 bp->b_refcnt = 1;
2039 bp->b_dev = NODEV;
2040 bp->b_vnbufs.le_next = NOLIST;
2041 BIO_SETPRIO(bp, BPRIO_DEFAULT);
2042}
2043
2044void
2045buf_destroy(buf_t *bp)
2046{
2047
2048 cv_destroy(&bp->b_done);
2049 cv_destroy(&bp->b_busy);
2050}
2051
2052int
2053bbusy(buf_t *bp, bool intr, int timo, kmutex_t *interlock)
2054{
2055 int error;
2056
2057 KASSERT(mutex_owned(&bufcache_lock));
2058
2059 if ((bp->b_cflags & BC_BUSY) != 0) {
2060 if (curlwp == uvm.pagedaemon_lwp)
2061 return EDEADLK;
2062 bp->b_cflags |= BC_WANTED;
2063 bref(bp);
2064 if (interlock != NULL)
2065 mutex_exit(interlock);
2066 if (intr) {
2067 error = cv_timedwait_sig(&bp->b_busy, &bufcache_lock,
2068 timo);
2069 } else {
2070 error = cv_timedwait(&bp->b_busy, &bufcache_lock,
2071 timo);
2072 }
2073 brele(bp);
2074 if (interlock != NULL)
2075 mutex_enter(interlock);
2076 if (error != 0)
2077 return error;
2078 return EPASSTHROUGH;
2079 }
2080 bp->b_cflags |= BC_BUSY;
2081
2082 return 0;
2083}
2084