/
vfs_bio.c
1821 lines (1578 loc) · 45.2 KB
/
vfs_bio.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/* $OpenBSD: vfs_bio.c,v 1.213 2024/02/03 18:51:58 beck Exp $ */
/* $NetBSD: vfs_bio.c,v 1.44 1996/06/11 11:15:36 pk Exp $ */
/*
* Copyright (c) 1994 Christopher G. Demetriou
* Copyright (c) 1982, 1986, 1989, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)vfs_bio.c 8.6 (Berkeley) 1/11/94
*/
/*
* Some references:
* Bach: The Design of the UNIX Operating System (Prentice Hall, 1986)
* Leffler, et al.: The Design and Implementation of the 4.3BSD
* UNIX Operating System (Addison Welley, 1989)
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/malloc.h>
#include <sys/pool.h>
#include <sys/specdev.h>
#include <sys/tracepoint.h>
#include <uvm/uvm_extern.h>
/* XXX Should really be in buf.h, but for uvm_constraint_range.. */
int buf_realloc_pages(struct buf *, struct uvm_constraint_range *, int);
struct uvm_constraint_range high_constraint;
int fliphigh;
int nobuffers;
int needbuffer;
/* private bufcache functions */
void bufcache_init(void);
void bufcache_adjust(void);
struct buf *bufcache_gethighcleanbuf(void);
struct buf *bufcache_getdmacleanbuf(void);
/*
* Buffer pool for I/O buffers.
*/
struct pool bufpool;
struct bufhead bufhead = LIST_HEAD_INITIALIZER(bufhead);
void buf_put(struct buf *);
struct buf *bio_doread(struct vnode *, daddr_t, int, int);
struct buf *buf_get(struct vnode *, daddr_t, size_t);
void bread_cluster_callback(struct buf *);
int64_t bufcache_recover_dmapages(int discard, int64_t howmany);
static struct buf *incore_locked(struct vnode *vp, daddr_t blkno);
struct bcachestats bcstats; /* counters */
long lodirtypages; /* dirty page count low water mark */
long hidirtypages; /* dirty page count high water mark */
long targetpages; /* target number of pages for cache size */
long buflowpages; /* smallest size cache allowed */
long bufhighpages; /* largest size cache allowed */
long bufbackpages; /* minimum number of pages we shrink when asked to */
vsize_t bufkvm;
struct proc *cleanerproc;
int bd_req; /* Sleep point for cleaner daemon. */
#define NUM_CACHES 2
#define DMA_CACHE 0
struct bufcache cleancache[NUM_CACHES];
struct bufqueue dirtyqueue;
void
buf_put(struct buf *bp)
{
splassert(IPL_BIO);
#ifdef DIAGNOSTIC
if (bp->b_pobj != NULL)
KASSERT(bp->b_bufsize > 0);
if (ISSET(bp->b_flags, B_DELWRI))
panic("buf_put: releasing dirty buffer");
if (bp->b_freelist.tqe_next != NOLIST &&
bp->b_freelist.tqe_next != (void *)-1)
panic("buf_put: still on the free list");
if (bp->b_vnbufs.le_next != NOLIST &&
bp->b_vnbufs.le_next != (void *)-1)
panic("buf_put: still on the vnode list");
#endif
LIST_REMOVE(bp, b_list);
bcstats.numbufs--;
if (buf_dealloc_mem(bp) != 0)
return;
pool_put(&bufpool, bp);
}
/*
* Initialize buffers and hash links for buffers.
*/
void
bufinit(void)
{
u_int64_t dmapages;
u_int64_t highpages;
dmapages = uvm_pagecount(&dma_constraint);
/* take away a guess at how much of this the kernel will consume */
dmapages -= (atop(physmem) - atop(uvmexp.free));
/* See if we have memory above the dma accessible region. */
high_constraint.ucr_low = dma_constraint.ucr_high;
high_constraint.ucr_high = no_constraint.ucr_high;
if (high_constraint.ucr_low != high_constraint.ucr_high)
high_constraint.ucr_low++;
highpages = uvm_pagecount(&high_constraint);
/*
* Do we have any significant amount of high memory above
* the DMA region? if so enable moving buffers there, if not,
* don't bother.
*/
if (highpages > dmapages / 4)
fliphigh = 1;
else
fliphigh = 0;
/*
* If MD code doesn't say otherwise, use up to 10% of DMA'able
* memory for buffers.
*/
if (bufcachepercent == 0)
bufcachepercent = 10;
/*
* XXX these values and their same use in kern_sysctl
* need to move into buf.h
*/
KASSERT(bufcachepercent <= 90);
KASSERT(bufcachepercent >= 5);
if (bufpages == 0)
bufpages = dmapages * bufcachepercent / 100;
if (bufpages < BCACHE_MIN)
bufpages = BCACHE_MIN;
KASSERT(bufpages < dmapages);
bufhighpages = bufpages;
/*
* Set the base backoff level for the buffer cache. We will
* not allow uvm to steal back more than this number of pages.
*/
buflowpages = dmapages * 5 / 100;
if (buflowpages < BCACHE_MIN)
buflowpages = BCACHE_MIN;
/*
* set bufbackpages to 100 pages, or 10 percent of the low water mark
* if we don't have that many pages.
*/
bufbackpages = buflowpages * 10 / 100;
if (bufbackpages > 100)
bufbackpages = 100;
/*
* If the MD code does not say otherwise, reserve 10% of kva
* space for mapping buffers.
*/
if (bufkvm == 0)
bufkvm = VM_KERNEL_SPACE_SIZE / 10;
/*
* Don't use more than twice the amount of bufpages for mappings.
* It's twice since we map things sparsely.
*/
if (bufkvm > bufpages * PAGE_SIZE)
bufkvm = bufpages * PAGE_SIZE;
/*
* Round bufkvm to MAXPHYS because we allocate chunks of va space
* in MAXPHYS chunks.
*/
bufkvm &= ~(MAXPHYS - 1);
pool_init(&bufpool, sizeof(struct buf), 0, IPL_BIO, 0, "bufpl", NULL);
bufcache_init();
/*
* hmm - bufkvm is an argument because it's static, while
* bufpages is global because it can change while running.
*/
buf_mem_init(bufkvm);
/*
* Set the dirty page high water mark to be less than the low
* water mark for pages in the buffer cache. This ensures we
* can always back off by throwing away clean pages, and give
* ourselves a chance to write out the dirty pages eventually.
*/
hidirtypages = (buflowpages / 4) * 3;
lodirtypages = buflowpages / 2;
/*
* We are allowed to use up to the reserve.
*/
targetpages = bufpages - RESERVE_PAGES;
}
/*
* Change cachepct
*/
void
bufadjust(int newbufpages)
{
int s;
int64_t npages;
if (newbufpages < buflowpages)
newbufpages = buflowpages;
s = splbio();
bufpages = newbufpages;
/*
* We are allowed to use up to the reserve
*/
targetpages = bufpages - RESERVE_PAGES;
npages = bcstats.dmapages - targetpages;
/*
* Shrinking the cache happens here only if someone has manually
* adjusted bufcachepercent - or the pagedaemon has told us
* to give back memory *now* - so we give it all back.
*/
if (bcstats.dmapages > targetpages)
(void) bufcache_recover_dmapages(0, bcstats.dmapages - targetpages);
bufcache_adjust();
/*
* Wake up the cleaner if we have lots of dirty pages,
* or if we are getting low on buffer cache kva.
*/
if ((UNCLEAN_PAGES >= hidirtypages) ||
bcstats.kvaslots_avail <= 2 * RESERVE_SLOTS)
wakeup(&bd_req);
splx(s);
}
/*
* Make the buffer cache back off from cachepct.
*/
int
bufbackoff(struct uvm_constraint_range *range, long size)
{
/*
* Back off "size" buffer cache pages. Called by the page
* daemon to consume buffer cache pages rather than scanning.
*
* It returns 0 to the pagedaemon to indicate that it has
* succeeded in freeing enough pages. It returns -1 to
* indicate that it could not and the pagedaemon should take
* other measures.
*
*/
long pdelta, oldbufpages;
/*
* If we will accept high memory for this backoff
* try to steal it from the high memory buffer cache.
*/
if (range != NULL && range->ucr_high > dma_constraint.ucr_high) {
struct buf *bp;
int64_t start = bcstats.numbufpages, recovered = 0;
int s = splbio();
while ((recovered < size) &&
(bp = bufcache_gethighcleanbuf())) {
bufcache_take(bp);
if (bp->b_vp) {
RBT_REMOVE(buf_rb_bufs,
&bp->b_vp->v_bufs_tree, bp);
brelvp(bp);
}
buf_put(bp);
recovered = start - bcstats.numbufpages;
}
bufcache_adjust();
splx(s);
/* If we got enough, return success */
if (recovered >= size)
return 0;
/*
* If we needed only memory above DMA,
* return failure
*/
if (range->ucr_low > dma_constraint.ucr_high)
return -1;
/* Otherwise get the rest from DMA */
size -= recovered;
}
/*
* XXX Otherwise do the dma memory cache dance. this needs
* refactoring later to get rid of 'bufpages'
*/
/*
* Back off by at least bufbackpages. If the page daemon gave us
* a larger size, back off by that much.
*/
pdelta = (size > bufbackpages) ? size : bufbackpages;
if (bufpages <= buflowpages)
return(-1);
if (bufpages - pdelta < buflowpages)
pdelta = bufpages - buflowpages;
oldbufpages = bufpages;
bufadjust(bufpages - pdelta);
if (oldbufpages - bufpages < size)
return (-1); /* we did not free what we were asked */
else
return(0);
}
/*
* Opportunistically flip a buffer into high memory. Will move the buffer
* if memory is available without sleeping, and return 0, otherwise will
* fail and return -1 with the buffer unchanged.
*/
int
buf_flip_high(struct buf *bp)
{
int ret = -1;
KASSERT(ISSET(bp->b_flags, B_BC));
KASSERT(ISSET(bp->b_flags, B_DMA));
KASSERT(bp->cache == DMA_CACHE);
KASSERT(fliphigh);
splassert(IPL_BIO);
/* Attempt to move the buffer to high memory if we can */
if (buf_realloc_pages(bp, &high_constraint, UVM_PLA_NOWAIT) == 0) {
KASSERT(!ISSET(bp->b_flags, B_DMA));
bcstats.highflips++;
ret = 0;
} else
bcstats.highflops++;
return ret;
}
/*
* Flip a buffer to dma reachable memory, when we need it there for
* I/O. This can sleep since it will wait for memory allocation in the
* DMA reachable area since we have to have the buffer there to proceed.
*/
void
buf_flip_dma(struct buf *bp)
{
KASSERT(ISSET(bp->b_flags, B_BC));
KASSERT(ISSET(bp->b_flags, B_BUSY));
KASSERT(bp->cache < NUM_CACHES);
splassert(IPL_BIO);
if (!ISSET(bp->b_flags, B_DMA)) {
/* move buf to dma reachable memory */
(void) buf_realloc_pages(bp, &dma_constraint, UVM_PLA_WAITOK);
KASSERT(ISSET(bp->b_flags, B_DMA));
bcstats.dmaflips++;
}
if (bp->cache > DMA_CACHE) {
CLR(bp->b_flags, B_COLD);
CLR(bp->b_flags, B_WARM);
bp->cache = DMA_CACHE;
}
}
struct buf *
bio_doread(struct vnode *vp, daddr_t blkno, int size, int async)
{
struct buf *bp;
struct mount *mp;
bp = getblk(vp, blkno, size, 0, INFSLP);
/*
* If buffer does not have valid data, start a read.
* Note that if buffer is B_INVAL, getblk() won't return it.
* Therefore, it's valid if its I/O has completed or been delayed.
*/
if (!ISSET(bp->b_flags, (B_DONE | B_DELWRI))) {
SET(bp->b_flags, B_READ | async);
bcstats.pendingreads++;
bcstats.numreads++;
VOP_STRATEGY(bp->b_vp, bp);
/* Pay for the read. */
curproc->p_ru.ru_inblock++; /* XXX */
} else if (async) {
brelse(bp);
}
mp = vp->v_type == VBLK ? vp->v_specmountpoint : vp->v_mount;
/*
* Collect statistics on synchronous and asynchronous reads.
* Reads from block devices are charged to their associated
* filesystem (if any).
*/
if (mp != NULL) {
if (async == 0)
mp->mnt_stat.f_syncreads++;
else
mp->mnt_stat.f_asyncreads++;
}
return (bp);
}
/*
* Read a disk block.
* This algorithm described in Bach (p.54).
*/
int
bread(struct vnode *vp, daddr_t blkno, int size, struct buf **bpp)
{
struct buf *bp;
/* Get buffer for block. */
bp = *bpp = bio_doread(vp, blkno, size, 0);
/* Wait for the read to complete, and return result. */
return (biowait(bp));
}
/*
* Read-ahead multiple disk blocks. The first is sync, the rest async.
* Trivial modification to the breada algorithm presented in Bach (p.55).
*/
int
breadn(struct vnode *vp, daddr_t blkno, int size, daddr_t rablks[],
int rasizes[], int nrablks, struct buf **bpp)
{
struct buf *bp;
int i;
bp = *bpp = bio_doread(vp, blkno, size, 0);
/*
* For each of the read-ahead blocks, start a read, if necessary.
*/
for (i = 0; i < nrablks; i++) {
/* If it's in the cache, just go on to next one. */
if (incore(vp, rablks[i]))
continue;
/* Get a buffer for the read-ahead block */
(void) bio_doread(vp, rablks[i], rasizes[i], B_ASYNC);
}
/* Otherwise, we had to start a read for it; wait until it's valid. */
return (biowait(bp));
}
/*
* Called from interrupt context.
*/
void
bread_cluster_callback(struct buf *bp)
{
struct buf **xbpp = bp->b_saveaddr;
int i;
if (xbpp[1] != NULL) {
size_t newsize = xbpp[1]->b_bufsize;
/*
* Shrink this buffer's mapping to only cover its part of
* the total I/O.
*/
buf_fix_mapping(bp, newsize);
bp->b_bcount = newsize;
}
/* Invalidate read-ahead buffers if read short */
if (bp->b_resid > 0) {
for (i = 1; xbpp[i] != NULL; i++)
continue;
for (i = i - 1; i != 0; i--) {
if (xbpp[i]->b_bufsize <= bp->b_resid) {
bp->b_resid -= xbpp[i]->b_bufsize;
SET(xbpp[i]->b_flags, B_INVAL);
} else if (bp->b_resid > 0) {
bp->b_resid = 0;
SET(xbpp[i]->b_flags, B_INVAL);
} else
break;
}
}
for (i = 1; xbpp[i] != NULL; i++) {
if (ISSET(bp->b_flags, B_ERROR))
SET(xbpp[i]->b_flags, B_INVAL | B_ERROR);
/*
* Move the pages from the master buffer's uvm object
* into the individual buffer's uvm objects.
*/
struct uvm_object *newobj = &xbpp[i]->b_uobj;
struct uvm_object *oldobj = &bp->b_uobj;
int page;
uvm_obj_init(newobj, &bufcache_pager, 1);
for (page = 0; page < atop(xbpp[i]->b_bufsize); page++) {
struct vm_page *pg = uvm_pagelookup(oldobj,
xbpp[i]->b_poffs + ptoa(page));
KASSERT(pg != NULL);
KASSERT(pg->wire_count == 1);
uvm_pagerealloc(pg, newobj, xbpp[i]->b_poffs + ptoa(page));
}
xbpp[i]->b_pobj = newobj;
biodone(xbpp[i]);
}
free(xbpp, M_TEMP, (i + 1) * sizeof(*xbpp));
if (ISSET(bp->b_flags, B_ASYNC)) {
brelse(bp);
} else {
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
}
/*
* Read-ahead multiple disk blocks, but make sure only one (big) I/O
* request is sent to the disk.
* XXX This should probably be dropped and breadn should instead be optimized
* XXX to do fewer I/O requests.
*/
int
bread_cluster(struct vnode *vp, daddr_t blkno, int size, struct buf **rbpp)
{
struct buf *bp, **xbpp;
int howmany, maxra, i, inc;
daddr_t sblkno;
*rbpp = bio_doread(vp, blkno, size, 0);
/*
* If the buffer is in the cache skip any I/O operation.
*/
if (ISSET((*rbpp)->b_flags, B_CACHE))
goto out;
if (size != round_page(size))
goto out;
if (VOP_BMAP(vp, blkno + 1, NULL, &sblkno, &maxra))
goto out;
maxra++;
if (sblkno == -1 || maxra < 2)
goto out;
howmany = MAXPHYS / size;
if (howmany > maxra)
howmany = maxra;
xbpp = mallocarray(howmany + 1, sizeof(*xbpp), M_TEMP, M_NOWAIT);
if (xbpp == NULL)
goto out;
for (i = howmany - 1; i >= 0; i--) {
size_t sz;
/*
* First buffer allocates big enough size to cover what
* all the other buffers need.
*/
sz = i == 0 ? howmany * size : 0;
xbpp[i] = buf_get(vp, blkno + i + 1, sz);
if (xbpp[i] == NULL) {
for (++i; i < howmany; i++) {
SET(xbpp[i]->b_flags, B_INVAL);
brelse(xbpp[i]);
}
free(xbpp, M_TEMP, (howmany + 1) * sizeof(*xbpp));
goto out;
}
}
bp = xbpp[0];
xbpp[howmany] = NULL;
inc = btodb(size);
for (i = 1; i < howmany; i++) {
bcstats.pendingreads++;
bcstats.numreads++;
/*
* We set B_DMA here because bp above will be B_DMA,
* and we are playing buffer slice-n-dice games from
* the memory allocated in bp.
*/
SET(xbpp[i]->b_flags, B_DMA | B_READ | B_ASYNC);
xbpp[i]->b_blkno = sblkno + (i * inc);
xbpp[i]->b_bufsize = xbpp[i]->b_bcount = size;
xbpp[i]->b_data = NULL;
xbpp[i]->b_pobj = bp->b_pobj;
xbpp[i]->b_poffs = bp->b_poffs + (i * size);
}
KASSERT(bp->b_lblkno == blkno + 1);
KASSERT(bp->b_vp == vp);
bp->b_blkno = sblkno;
SET(bp->b_flags, B_READ | B_ASYNC | B_CALL);
bp->b_saveaddr = (void *)xbpp;
bp->b_iodone = bread_cluster_callback;
bcstats.pendingreads++;
bcstats.numreads++;
VOP_STRATEGY(bp->b_vp, bp);
curproc->p_ru.ru_inblock++;
out:
return (biowait(*rbpp));
}
/*
* Block write. Described in Bach (p.56)
*/
int
bwrite(struct buf *bp)
{
int rv, async, wasdelayed, s;
struct vnode *vp;
struct mount *mp;
vp = bp->b_vp;
if (vp != NULL)
mp = vp->v_type == VBLK? vp->v_specmountpoint : vp->v_mount;
else
mp = NULL;
/*
* Remember buffer type, to switch on it later. If the write was
* synchronous, but the file system was mounted with MNT_ASYNC,
* convert it to a delayed write.
* XXX note that this relies on delayed tape writes being converted
* to async, not sync writes (which is safe, but ugly).
*/
async = ISSET(bp->b_flags, B_ASYNC);
if (!async && mp && ISSET(mp->mnt_flag, MNT_ASYNC)) {
/*
* Don't convert writes from VND on async filesystems
* that already have delayed writes in the upper layer.
*/
if (!ISSET(bp->b_flags, B_NOCACHE)) {
bdwrite(bp);
return (0);
}
}
/*
* Collect statistics on synchronous and asynchronous writes.
* Writes to block devices are charged to their associated
* filesystem (if any).
*/
if (mp != NULL) {
if (async)
mp->mnt_stat.f_asyncwrites++;
else
mp->mnt_stat.f_syncwrites++;
}
bcstats.pendingwrites++;
bcstats.numwrites++;
wasdelayed = ISSET(bp->b_flags, B_DELWRI);
CLR(bp->b_flags, (B_READ | B_DONE | B_ERROR | B_DELWRI));
s = splbio();
/*
* If not synchronous, pay for the I/O operation and make
* sure the buf is on the correct vnode queue. We have
* to do this now, because if we don't, the vnode may not
* be properly notified that its I/O has completed.
*/
if (wasdelayed) {
reassignbuf(bp);
} else
curproc->p_ru.ru_oublock++;
/* Initiate disk write. Make sure the appropriate party is charged. */
bp->b_vp->v_numoutput++;
buf_flip_dma(bp);
SET(bp->b_flags, B_WRITEINPROG);
splx(s);
VOP_STRATEGY(bp->b_vp, bp);
/*
* If the queue is above the high water mark, wait till
* the number of outstanding write bufs drops below the low
* water mark.
*/
if (bp->b_bq)
bufq_wait(bp->b_bq);
if (async)
return (0);
/*
* If I/O was synchronous, wait for it to complete.
*/
rv = biowait(bp);
/* Release the buffer. */
brelse(bp);
return (rv);
}
/*
* Delayed write.
*
* The buffer is marked dirty, but is not queued for I/O.
* This routine should be used when the buffer is expected
* to be modified again soon, typically a small write that
* partially fills a buffer.
*
* NB: magnetic tapes cannot be delayed; they must be
* written in the order that the writes are requested.
*
* Described in Leffler, et al. (pp. 208-213).
*/
void
bdwrite(struct buf *bp)
{
int s;
/*
* If the block hasn't been seen before:
* (1) Mark it as having been seen,
* (2) Charge for the write.
* (3) Make sure it's on its vnode's correct block list,
* (4) If a buffer is rewritten, move it to end of dirty list
*/
if (!ISSET(bp->b_flags, B_DELWRI)) {
SET(bp->b_flags, B_DELWRI);
s = splbio();
buf_flip_dma(bp);
reassignbuf(bp);
splx(s);
curproc->p_ru.ru_oublock++; /* XXX */
}
/* The "write" is done, so mark and release the buffer. */
CLR(bp->b_flags, B_NEEDCOMMIT);
CLR(bp->b_flags, B_NOCACHE); /* Must cache delayed writes */
SET(bp->b_flags, B_DONE);
brelse(bp);
}
/*
* Asynchronous block write; just an asynchronous bwrite().
*/
void
bawrite(struct buf *bp)
{
SET(bp->b_flags, B_ASYNC);
VOP_BWRITE(bp);
}
/*
* Must be called at splbio()
*/
void
buf_dirty(struct buf *bp)
{
splassert(IPL_BIO);
#ifdef DIAGNOSTIC
if (!ISSET(bp->b_flags, B_BUSY))
panic("Trying to dirty buffer on freelist!");
#endif
if (ISSET(bp->b_flags, B_DELWRI) == 0) {
SET(bp->b_flags, B_DELWRI);
buf_flip_dma(bp);
reassignbuf(bp);
}
}
/*
* Must be called at splbio()
*/
void
buf_undirty(struct buf *bp)
{
splassert(IPL_BIO);
#ifdef DIAGNOSTIC
if (!ISSET(bp->b_flags, B_BUSY))
panic("Trying to undirty buffer on freelist!");
#endif
if (ISSET(bp->b_flags, B_DELWRI)) {
CLR(bp->b_flags, B_DELWRI);
reassignbuf(bp);
}
}
/*
* Release a buffer on to the free lists.
* Described in Bach (p. 46).
*/
void
brelse(struct buf *bp)
{
int s;
s = splbio();
if (bp->b_data != NULL)
KASSERT(bp->b_bufsize > 0);
/*
* Determine which queue the buffer should be on, then put it there.
*/
/* If it's not cacheable, or an error, mark it invalid. */
if (ISSET(bp->b_flags, (B_NOCACHE|B_ERROR)))
SET(bp->b_flags, B_INVAL);
/* If it's a write error, also mark the vnode as damaged. */
if (ISSET(bp->b_flags, B_ERROR) && !ISSET(bp->b_flags, B_READ)) {
if (bp->b_vp && bp->b_vp->v_type == VREG)
SET(bp->b_vp->v_bioflag, VBIOERROR);
}
if (ISSET(bp->b_flags, B_INVAL)) {
/*
* If the buffer is invalid, free it now rather than leaving
* it in a queue and wasting memory.
*/
if (ISSET(bp->b_flags, B_DELWRI)) {
CLR(bp->b_flags, B_DELWRI);
}
if (bp->b_vp) {
RBT_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp);
brelvp(bp);
}
bp->b_vp = NULL;
/*
* Wake up any processes waiting for _this_ buffer to
* become free. They are not allowed to grab it
* since it will be freed. But the only sleeper is
* getblk and it will restart the operation after
* sleep.
*/
if (ISSET(bp->b_flags, B_WANTED)) {
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
buf_put(bp);
} else {
/*
* It has valid data. Put it on the end of the appropriate
* queue, so that it'll stick around for as long as possible.
*/
bufcache_release(bp);
/* Unlock the buffer. */
CLR(bp->b_flags, (B_AGE | B_ASYNC | B_NOCACHE | B_DEFERRED));
buf_release(bp);
/* Wake up any processes waiting for _this_ buffer to
* become free. */
if (ISSET(bp->b_flags, B_WANTED)) {
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
if (bcstats.dmapages > targetpages)
(void) bufcache_recover_dmapages(0,
bcstats.dmapages - targetpages);
bufcache_adjust();
}
/* Wake up syncer and cleaner processes waiting for buffers. */
if (nobuffers) {
nobuffers = 0;
wakeup(&nobuffers);
}
/* Wake up any processes waiting for any buffer to become free. */
if (needbuffer && bcstats.dmapages < targetpages &&
bcstats.kvaslots_avail > RESERVE_SLOTS) {
needbuffer = 0;
wakeup(&needbuffer);
}
splx(s);
}
/*
* Determine if a block is in the cache. Just look on what would be its hash
* chain. If it's there, return a pointer to it, unless it's marked invalid.
*/
static struct buf *
incore_locked(struct vnode *vp, daddr_t blkno)
{
struct buf *bp;
struct buf b;
splassert(IPL_BIO);
/* Search buf lookup tree */
b.b_lblkno = blkno;
bp = RBT_FIND(buf_rb_bufs, &vp->v_bufs_tree, &b);
if (bp != NULL && ISSET(bp->b_flags, B_INVAL))
bp = NULL;
return (bp);
}
struct buf *
incore(struct vnode *vp, daddr_t blkno)
{
struct buf *bp;
int s;
s = splbio();
bp = incore_locked(vp, blkno);
splx(s);
return (bp);
}
/*
* Get a block of requested size that is associated with
* a given vnode and block offset. If it is found in the
* block cache, mark it as having been found, make it busy
* and return it. Otherwise, return an empty block of the
* correct size. It is up to the caller to ensure that the
* cached blocks be of the correct size.
*/
struct buf *