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