summaryrefslogtreecommitdiffstats
path: root/sys/kern/vfs_cluster.c
blob: 72e80d63ece780cee5b30f265780615a5ccf9d2c (plain)
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
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
/*-
 * Copyright (c) 1993
 *	The Regents of the University of California.  All rights reserved.
 * Modifications/enhancements:
 * 	Copyright (c) 1995 John S. Dyson.  All rights reserved.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. 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_cluster.c	8.7 (Berkeley) 2/13/94
 * $FreeBSD$
 */

#include "opt_debug_cluster.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/resourcevar.h>
#include <sys/vmmeter.h>
#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <sys/sysctl.h>

#if defined(CLUSTERDEBUG)
static int	rcluster= 0;
SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0,
    "Debug VFS clustering code");
#endif

static MALLOC_DEFINE(M_SEGMENT, "cluster_save buffer", "cluster_save buffer");

static struct cluster_save *
	cluster_collectbufs(struct vnode *vp, struct buf *last_bp);
static struct buf *
	cluster_rbuild(struct vnode *vp, u_quad_t filesize, daddr_t lbn,
			 daddr_t blkno, long size, int run, struct buf *fbp);

static int write_behind = 1;
SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0,
    "Cluster write-behind; 0: disable, 1: enable, 2: backed off");

static int read_max = 8;
SYSCTL_INT(_vfs, OID_AUTO, read_max, CTLFLAG_RW, &read_max, 0,
    "Cluster read-ahead max block count");

/* Page expended to mark partially backed buffers */
extern vm_page_t	bogus_page;

/*
 * Number of physical bufs (pbufs) this subsystem is allowed.
 * Manipulated by vm_pager.c
 */
extern int cluster_pbuf_freecnt;

/*
 * Read data to a buf, including read-ahead if we find this to be beneficial.
 * cluster_read replaces bread.
 */
int
cluster_read(vp, filesize, lblkno, size, cred, totread, seqcount, bpp)
	struct vnode *vp;
	u_quad_t filesize;
	daddr_t lblkno;
	long size;
	struct ucred *cred;
	long totread;
	int seqcount;
	struct buf **bpp;
{
	struct buf *bp, *rbp, *reqbp;
	daddr_t blkno, origblkno;
	int maxra, racluster;
	int error, ncontig;
	int i;

	error = 0;

	/*
	 * Try to limit the amount of read-ahead by a few
	 * ad-hoc parameters.  This needs work!!!
	 */
	racluster = vp->v_mount->mnt_iosize_max / size;
	maxra = seqcount;
	maxra = min(read_max, maxra);
	maxra = min(nbuf/8, maxra);
	if (((u_quad_t)(lblkno + maxra + 1) * size) > filesize)
		maxra = (filesize / size) - lblkno;

	/*
	 * get the requested block
	 */
	*bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0, 0);
	origblkno = lblkno;

	/*
	 * if it is in the cache, then check to see if the reads have been
	 * sequential.  If they have, then try some read-ahead, otherwise
	 * back-off on prospective read-aheads.
	 */
	if (bp->b_flags & B_CACHE) {
		if (!seqcount) {
			return 0;
		} else if ((bp->b_flags & B_RAM) == 0) {
			return 0;
		} else {
			int s;
			bp->b_flags &= ~B_RAM;
			/*
			 * We do the spl here so that there is no window
			 * between the incore and the b_usecount increment
			 * below.  We opt to keep the spl out of the loop
			 * for efficiency.
			 */
			s = splbio();
			VI_LOCK(vp);
			for (i = 1; i < maxra; i++) {
				/*
				 * Stop if the buffer does not exist or it
				 * is invalid (about to go away?)
				 */
				rbp = gbincore(vp, lblkno+i);
				if (rbp == NULL || (rbp->b_flags & B_INVAL))
					break;

				/*
				 * Set another read-ahead mark so we know 
				 * to check again.
				 */
				if (((i % racluster) == (racluster - 1)) ||
					(i == (maxra - 1)))
					rbp->b_flags |= B_RAM;
			}
			VI_UNLOCK(vp);
			splx(s);
			if (i >= maxra) {
				return 0;
			}
			lblkno += i;
		}
		reqbp = bp = NULL;
	/*
	 * If it isn't in the cache, then get a chunk from
	 * disk if sequential, otherwise just get the block.
	 */
	} else {
		off_t firstread = bp->b_offset;
		int nblks;

		KASSERT(bp->b_offset != NOOFFSET,
		    ("cluster_read: no buffer offset"));

		ncontig = 0;

		/*
		 * Compute the total number of blocks that we should read
		 * synchronously.
		 */
		if (firstread + totread > filesize)
			totread = filesize - firstread;
		nblks = howmany(totread, size);
		if (nblks > racluster)
			nblks = racluster;

		/*
		 * Now compute the number of contiguous blocks.
		 */
		if (nblks > 1) {
	    		error = VOP_BMAP(vp, lblkno, NULL,
				&blkno, &ncontig, NULL);
			/*
			 * If this failed to map just do the original block.
			 */
			if (error || blkno == -1)
				ncontig = 0;
		}

		/*
		 * If we have contiguous data available do a cluster
		 * otherwise just read the requested block.
		 */
		if (ncontig) {
			/* Account for our first block. */
			ncontig = min(ncontig + 1, nblks);
			if (ncontig < nblks)
				nblks = ncontig;
			bp = cluster_rbuild(vp, filesize, lblkno,
				blkno, size, nblks, bp);
			lblkno += (bp->b_bufsize / size);
		} else {
			bp->b_flags |= B_RAM;
			bp->b_iocmd = BIO_READ;
			lblkno += 1;
		}
	}

	/*
	 * handle the synchronous read so that it is available ASAP.
	 */
	if (bp) {
		if ((bp->b_flags & B_CLUSTER) == 0) {
			vfs_busy_pages(bp, 0);
		}
		bp->b_flags &= ~B_INVAL;
		bp->b_ioflags &= ~BIO_ERROR;
		if ((bp->b_flags & B_ASYNC) || bp->b_iodone != NULL)
			BUF_KERNPROC(bp);
		error = VOP_STRATEGY(vp, bp);
		curproc->p_stats->p_ru.ru_inblock++;
		if (error)
			return (error);
	}

	/*
	 * If we have been doing sequential I/O, then do some read-ahead.
	 */
	while (lblkno < (origblkno + maxra)) {
		error = VOP_BMAP(vp, lblkno, NULL, &blkno, &ncontig, NULL);
		if (error)
			break;

		if (blkno == -1)
			break;

		/*
		 * We could throttle ncontig here by maxra but we might as
		 * well read the data if it is contiguous.  We're throttled
		 * by racluster anyway.
		 */
		if (ncontig) {
			ncontig = min(ncontig + 1, racluster);
			rbp = cluster_rbuild(vp, filesize, lblkno, blkno,
				size, ncontig, NULL);
			lblkno += (rbp->b_bufsize / size);
			if (rbp->b_flags & B_DELWRI) {
				bqrelse(rbp);
				continue;
			}
		} else {
			rbp = getblk(vp, lblkno, size, 0, 0, 0);
			lblkno += 1;
			if (rbp->b_flags & B_DELWRI) {
				bqrelse(rbp);
				continue;
			}
			rbp->b_flags |= B_ASYNC | B_RAM;
			rbp->b_iocmd = BIO_READ;
			rbp->b_blkno = blkno;
		}
		if (rbp->b_flags & B_CACHE) {
			rbp->b_flags &= ~B_ASYNC;
			bqrelse(rbp);
			continue;
		}
		if ((rbp->b_flags & B_CLUSTER) == 0) {
			vfs_busy_pages(rbp, 0);
		}
		rbp->b_flags &= ~B_INVAL;
		rbp->b_ioflags &= ~BIO_ERROR;
		if ((rbp->b_flags & B_ASYNC) || rbp->b_iodone != NULL)
			BUF_KERNPROC(rbp);
		(void) VOP_STRATEGY(vp, rbp);
		curproc->p_stats->p_ru.ru_inblock++;
	}

	if (reqbp)
		return (bufwait(reqbp));
	else
		return (error);
}

/*
 * If blocks are contiguous on disk, use this to provide clustered
 * read ahead.  We will read as many blocks as possible sequentially
 * and then parcel them up into logical blocks in the buffer hash table.
 */
static struct buf *
cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
	struct vnode *vp;
	u_quad_t filesize;
	daddr_t lbn;
	daddr_t blkno;
	long size;
	int run;
	struct buf *fbp;
{
	struct buf *bp, *tbp;
	daddr_t bn;
	int i, inc, j;

	GIANT_REQUIRED;

	KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
	    ("cluster_rbuild: size %ld != filesize %ld\n",
	    size, vp->v_mount->mnt_stat.f_iosize));

	/*
	 * avoid a division
	 */
	while ((u_quad_t) size * (lbn + run) > filesize) {
		--run;
	}

	if (fbp) {
		tbp = fbp;
		tbp->b_iocmd = BIO_READ; 
	} else {
		tbp = getblk(vp, lbn, size, 0, 0, 0);
		if (tbp->b_flags & B_CACHE)
			return tbp;
		tbp->b_flags |= B_ASYNC | B_RAM;
		tbp->b_iocmd = BIO_READ;
	}

	tbp->b_blkno = blkno;
	if( (tbp->b_flags & B_MALLOC) ||
		((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
		return tbp;

	bp = trypbuf(&cluster_pbuf_freecnt);
	if (bp == 0)
		return tbp;

	/*
	 * We are synthesizing a buffer out of vm_page_t's, but
	 * if the block size is not page aligned then the starting
	 * address may not be either.  Inherit the b_data offset
	 * from the original buffer.
	 */
	bp->b_data = (char *)((vm_offset_t)bp->b_data |
	    ((vm_offset_t)tbp->b_data & PAGE_MASK));
	bp->b_flags = B_ASYNC | B_CLUSTER | B_VMIO;
	bp->b_iocmd = BIO_READ;
	bp->b_iodone = cluster_callback;
	bp->b_blkno = blkno;
	bp->b_lblkno = lbn;
	bp->b_offset = tbp->b_offset;
	KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
	pbgetvp(vp, bp);

	TAILQ_INIT(&bp->b_cluster.cluster_head);

	bp->b_bcount = 0;
	bp->b_bufsize = 0;
	bp->b_npages = 0;

	inc = btodb(size);
	for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
		if (i != 0) {
			if ((bp->b_npages * PAGE_SIZE) +
			    round_page(size) > vp->v_mount->mnt_iosize_max) {
				break;
			}

			tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT);

			/* Don't wait around for locked bufs. */
			if (tbp == NULL)
				break;

			/*
			 * Stop scanning if the buffer is fully valid
			 * (marked B_CACHE), or locked (may be doing a
			 * background write), or if the buffer is not
			 * VMIO backed.  The clustering code can only deal
			 * with VMIO-backed buffers.
			 */
			if ((tbp->b_flags & (B_CACHE|B_LOCKED)) ||
				(tbp->b_flags & B_VMIO) == 0) {
				bqrelse(tbp);
				break;
			}

			/*
			 * The buffer must be completely invalid in order to
			 * take part in the cluster.  If it is partially valid
			 * then we stop.
			 */
			for (j = 0;j < tbp->b_npages; j++) {
				if (tbp->b_pages[j]->valid)
					break;
			}
			if (j != tbp->b_npages) {
				bqrelse(tbp);
				break;
			}

			/*
			 * Set a read-ahead mark as appropriate
			 */
			if ((fbp && (i == 1)) || (i == (run - 1)))
				tbp->b_flags |= B_RAM;

			/*
			 * Set the buffer up for an async read (XXX should
			 * we do this only if we do not wind up brelse()ing?).
			 * Set the block number if it isn't set, otherwise
			 * if it is make sure it matches the block number we
			 * expect.
			 */
			tbp->b_flags |= B_ASYNC;
			tbp->b_iocmd = BIO_READ;
			if (tbp->b_blkno == tbp->b_lblkno) {
				tbp->b_blkno = bn;
			} else if (tbp->b_blkno != bn) {
				brelse(tbp);
				break;
			}
		}
		/*
		 * XXX fbp from caller may not be B_ASYNC, but we are going
		 * to biodone() it in cluster_callback() anyway
		 */
		BUF_KERNPROC(tbp);
		TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
			tbp, b_cluster.cluster_entry);
		if (tbp->b_object != NULL)
			VM_OBJECT_LOCK(tbp->b_object);
		vm_page_lock_queues();
		for (j = 0; j < tbp->b_npages; j += 1) {
			vm_page_t m;
			m = tbp->b_pages[j];
			vm_page_io_start(m);
			vm_object_pip_add(m->object, 1);
			if ((bp->b_npages == 0) ||
				(bp->b_pages[bp->b_npages-1] != m)) {
				bp->b_pages[bp->b_npages] = m;
				bp->b_npages++;
			}
			if ((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL)
				tbp->b_pages[j] = bogus_page;
		}
		vm_page_unlock_queues();
		if (tbp->b_object != NULL)
			VM_OBJECT_UNLOCK(tbp->b_object);
		/*
		 * XXX shouldn't this be += size for both, like in
		 * cluster_wbuild()?
		 *
		 * Don't inherit tbp->b_bufsize as it may be larger due to
		 * a non-page-aligned size.  Instead just aggregate using
		 * 'size'.
		 */
		if (tbp->b_bcount != size)
			printf("warning: tbp->b_bcount wrong %ld vs %ld\n", tbp->b_bcount, size);
		if (tbp->b_bufsize != size)
			printf("warning: tbp->b_bufsize wrong %ld vs %ld\n", tbp->b_bufsize, size);
		bp->b_bcount += size;
		bp->b_bufsize += size;
	}

	/*
	 * Fully valid pages in the cluster are already good and do not need
	 * to be re-read from disk.  Replace the page with bogus_page
	 */
	for (j = 0; j < bp->b_npages; j++) {
		if ((bp->b_pages[j]->valid & VM_PAGE_BITS_ALL) ==
		    VM_PAGE_BITS_ALL) {
			bp->b_pages[j] = bogus_page;
		}
	}
	if (bp->b_bufsize > bp->b_kvasize)
		panic("cluster_rbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
		    bp->b_bufsize, bp->b_kvasize);
	bp->b_kvasize = bp->b_bufsize;

	pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
		(vm_page_t *)bp->b_pages, bp->b_npages);
	return (bp);
}

/*
 * Cleanup after a clustered read or write.
 * This is complicated by the fact that any of the buffers might have
 * extra memory (if there were no empty buffer headers at allocbuf time)
 * that we will need to shift around.
 */
void
cluster_callback(bp)
	struct buf *bp;
{
	struct buf *nbp, *tbp;
	int error = 0;

	GIANT_REQUIRED;

	/*
	 * Must propogate errors to all the components.
	 */
	if (bp->b_ioflags & BIO_ERROR)
		error = bp->b_error;

	pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);
	/*
	 * Move memory from the large cluster buffer into the component
	 * buffers and mark IO as done on these.
	 */
	for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
		tbp; tbp = nbp) {
		nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
		if (error) {
			tbp->b_ioflags |= BIO_ERROR;
			tbp->b_error = error;
		} else {
			tbp->b_dirtyoff = tbp->b_dirtyend = 0;
			tbp->b_flags &= ~B_INVAL;
			tbp->b_ioflags &= ~BIO_ERROR;
			/*
			 * XXX the bdwrite()/bqrelse() issued during
			 * cluster building clears B_RELBUF (see bqrelse()
			 * comment).  If direct I/O was specified, we have
			 * to restore it here to allow the buffer and VM
			 * to be freed.
			 */
			if (tbp->b_flags & B_DIRECT)
				tbp->b_flags |= B_RELBUF;
		}
		bufdone(tbp);
	}
	relpbuf(bp, &cluster_pbuf_freecnt);
}

/*
 *	cluster_wbuild_wb:
 *
 *	Implement modified write build for cluster.
 *
 *		write_behind = 0	write behind disabled
 *		write_behind = 1	write behind normal (default)
 *		write_behind = 2	write behind backed-off
 */

static __inline int
cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len)
{
	int r = 0;

	switch(write_behind) {
	case 2:
		if (start_lbn < len)
			break;
		start_lbn -= len;
		/* FALLTHROUGH */
	case 1:
		r = cluster_wbuild(vp, size, start_lbn, len);
		/* FALLTHROUGH */
	default:
		/* FALLTHROUGH */
		break;
	}
	return(r);
}

/*
 * Do clustered write for FFS.
 *
 * Three cases:
 *	1. Write is not sequential (write asynchronously)
 *	Write is sequential:
 *	2.	beginning of cluster - begin cluster
 *	3.	middle of a cluster - add to cluster
 *	4.	end of a cluster - asynchronously write cluster
 */
void
cluster_write(bp, filesize, seqcount)
	struct buf *bp;
	u_quad_t filesize;
	int seqcount;
{
	struct vnode *vp;
	daddr_t lbn;
	int maxclen, cursize;
	int lblocksize;
	int async;

	vp = bp->b_vp;
	if (vp->v_type == VREG) {
		async = vp->v_mount->mnt_flag & MNT_ASYNC;
		lblocksize = vp->v_mount->mnt_stat.f_iosize;
	} else {
		async = 0;
		lblocksize = bp->b_bufsize;
	}
	lbn = bp->b_lblkno;
	KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));

	/* Initialize vnode to beginning of file. */
	if (lbn == 0)
		vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;

	if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
	    (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
		maxclen = vp->v_mount->mnt_iosize_max / lblocksize - 1;
		if (vp->v_clen != 0) {
			/*
			 * Next block is not sequential.
			 *
			 * If we are not writing at end of file, the process
			 * seeked to another point in the file since its last
			 * write, or we have reached our maximum cluster size,
			 * then push the previous cluster. Otherwise try
			 * reallocating to make it sequential.
			 *
			 * Change to algorithm: only push previous cluster if
			 * it was sequential from the point of view of the
			 * seqcount heuristic, otherwise leave the buffer 
			 * intact so we can potentially optimize the I/O
			 * later on in the buf_daemon or update daemon
			 * flush.
			 */
			cursize = vp->v_lastw - vp->v_cstart + 1;
			if (((u_quad_t) bp->b_offset + lblocksize) != filesize ||
			    lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
				if (!async && seqcount > 0) {
					cluster_wbuild_wb(vp, lblocksize,
						vp->v_cstart, cursize);
				}
			} else {
				struct buf **bpp, **endbp;
				struct cluster_save *buflist;

				buflist = cluster_collectbufs(vp, bp);
				endbp = &buflist->bs_children
				    [buflist->bs_nchildren - 1];
				if (VOP_REALLOCBLKS(vp, buflist)) {
					/*
					 * Failed, push the previous cluster
					 * if *really* writing sequentially
					 * in the logical file (seqcount > 1),
					 * otherwise delay it in the hopes that
					 * the low level disk driver can
					 * optimize the write ordering.
					 */
					for (bpp = buflist->bs_children;
					     bpp < endbp; bpp++)
						brelse(*bpp);
					free(buflist, M_SEGMENT);
					if (seqcount > 1) {
						cluster_wbuild_wb(vp, 
						    lblocksize, vp->v_cstart, 
						    cursize);
					}
				} else {
					/*
					 * Succeeded, keep building cluster.
					 */
					for (bpp = buflist->bs_children;
					     bpp <= endbp; bpp++)
						bdwrite(*bpp);
					free(buflist, M_SEGMENT);
					vp->v_lastw = lbn;
					vp->v_lasta = bp->b_blkno;
					return;
				}
			}
		}
		/*
		 * Consider beginning a cluster. If at end of file, make
		 * cluster as large as possible, otherwise find size of
		 * existing cluster.
		 */
		if ((vp->v_type == VREG) &&
			((u_quad_t) bp->b_offset + lblocksize) != filesize &&
		    (bp->b_blkno == bp->b_lblkno) &&
		    (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
		     bp->b_blkno == -1)) {
			bawrite(bp);
			vp->v_clen = 0;
			vp->v_lasta = bp->b_blkno;
			vp->v_cstart = lbn + 1;
			vp->v_lastw = lbn;
			return;
		}
		vp->v_clen = maxclen;
		if (!async && maxclen == 0) {	/* I/O not contiguous */
			vp->v_cstart = lbn + 1;
			bawrite(bp);
		} else {	/* Wait for rest of cluster */
			vp->v_cstart = lbn;
			bdwrite(bp);
		}
	} else if (lbn == vp->v_cstart + vp->v_clen) {
		/*
		 * At end of cluster, write it out if seqcount tells us we
		 * are operating sequentially, otherwise let the buf or
		 * update daemon handle it.
		 */
		bdwrite(bp);
		if (seqcount > 1)
			cluster_wbuild_wb(vp, lblocksize, vp->v_cstart, vp->v_clen + 1);
		vp->v_clen = 0;
		vp->v_cstart = lbn + 1;
	} else if (vm_page_count_severe()) {
		/*
		 * We are low on memory, get it going NOW
		 */
		bawrite(bp);
	} else {
		/*
		 * In the middle of a cluster, so just delay the I/O for now.
		 */
		bdwrite(bp);
	}
	vp->v_lastw = lbn;
	vp->v_lasta = bp->b_blkno;
}


/*
 * This is an awful lot like cluster_rbuild...wish they could be combined.
 * The last lbn argument is the current block on which I/O is being
 * performed.  Check to see that it doesn't fall in the middle of
 * the current block (if last_bp == NULL).
 */
int
cluster_wbuild(vp, size, start_lbn, len)
	struct vnode *vp;
	long size;
	daddr_t start_lbn;
	int len;
{
	struct buf *bp, *tbp;
	int i, j, s;
	int totalwritten = 0;
	int dbsize = btodb(size);

	GIANT_REQUIRED;

	while (len > 0) {
		s = splbio();
		/*
		 * If the buffer is not delayed-write (i.e. dirty), or it
		 * is delayed-write but either locked or inval, it cannot
		 * partake in the clustered write.
		 */
		VI_LOCK(vp);
		if ((tbp = gbincore(vp, start_lbn)) == NULL) {
			VI_UNLOCK(vp);
			++start_lbn;
			--len;
			splx(s);
			continue;
		}
		if (BUF_LOCK(tbp,
		    LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, VI_MTX(vp))) {
			++start_lbn;
			--len;
			splx(s);
			continue;
		}
		if ((tbp->b_flags & (B_LOCKED | B_INVAL | B_DELWRI)) !=
		    B_DELWRI) {
			BUF_UNLOCK(tbp);
			++start_lbn;
			--len;
			splx(s);
			continue;
		}
		bremfree(tbp);
		tbp->b_flags &= ~B_DONE;
		splx(s);

		/*
		 * Extra memory in the buffer, punt on this buffer.
		 * XXX we could handle this in most cases, but we would
		 * have to push the extra memory down to after our max
		 * possible cluster size and then potentially pull it back
		 * up if the cluster was terminated prematurely--too much
		 * hassle.
		 */
		if (((tbp->b_flags & (B_CLUSTEROK | B_MALLOC | B_VMIO)) != 
		     (B_CLUSTEROK | B_VMIO)) ||
		  (tbp->b_bcount != tbp->b_bufsize) ||
		  (tbp->b_bcount != size) ||
		  (len == 1) ||
		  ((bp = getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
			totalwritten += tbp->b_bufsize;
			bawrite(tbp);
			++start_lbn;
			--len;
			continue;
		}

		/*
		 * We got a pbuf to make the cluster in.
		 * so initialise it.
		 */
		TAILQ_INIT(&bp->b_cluster.cluster_head);
		bp->b_bcount = 0;
		bp->b_magic = tbp->b_magic;
		bp->b_op = tbp->b_op;
		bp->b_bufsize = 0;
		bp->b_npages = 0;
		if (tbp->b_wcred != NOCRED)
			bp->b_wcred = crhold(tbp->b_wcred);

		bp->b_blkno = tbp->b_blkno;
		bp->b_lblkno = tbp->b_lblkno;
		bp->b_offset = tbp->b_offset;

		/*
		 * We are synthesizing a buffer out of vm_page_t's, but
		 * if the block size is not page aligned then the starting
		 * address may not be either.  Inherit the b_data offset
		 * from the original buffer.
		 */
		bp->b_data = (char *)((vm_offset_t)bp->b_data |
		    ((vm_offset_t)tbp->b_data & PAGE_MASK));
		bp->b_flags |= B_CLUSTER |
				(tbp->b_flags & (B_VMIO | B_NEEDCOMMIT));
		bp->b_iodone = cluster_callback;
		pbgetvp(vp, bp);
		/*
		 * From this location in the file, scan forward to see
		 * if there are buffers with adjacent data that need to
		 * be written as well.
		 */
		for (i = 0; i < len; ++i, ++start_lbn) {
			if (i != 0) { /* If not the first buffer */
				s = splbio();
				/*
				 * If the adjacent data is not even in core it
				 * can't need to be written.
				 */
				VI_LOCK(vp);
				if ((tbp = gbincore(vp, start_lbn)) == NULL) {
					VI_UNLOCK(vp);
					splx(s);
					break;
				}

				/*
				 * If it IS in core, but has different
				 * characteristics, or is locked (which
				 * means it could be undergoing a background
				 * I/O or be in a weird state), then don't
				 * cluster with it.
				 */
				if (BUF_LOCK(tbp,
				    LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
				    VI_MTX(vp))) {
					splx(s);
					break;
				}

				if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
				    B_INVAL | B_DELWRI | B_NEEDCOMMIT))
				    != (B_DELWRI | B_CLUSTEROK |
				    (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
				    (tbp->b_flags & B_LOCKED) ||
				    tbp->b_wcred != bp->b_wcred) {
					BUF_UNLOCK(tbp);
					splx(s);
					break;
				}

				/*
				 * Check that the combined cluster
				 * would make sense with regard to pages
				 * and would not be too large
				 */
				if ((tbp->b_bcount != size) ||
				  ((bp->b_blkno + (dbsize * i)) !=
				    tbp->b_blkno) ||
				  ((tbp->b_npages + bp->b_npages) >
				    (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
					BUF_UNLOCK(tbp);
					splx(s);
					break;
				}
				/*
				 * Ok, it's passed all the tests,
				 * so remove it from the free list
				 * and mark it busy. We will use it.
				 */
				bremfree(tbp);
				tbp->b_flags &= ~B_DONE;
				splx(s);
			} /* end of code for non-first buffers only */
			/* check for latent dependencies to be handled */
			if ((LIST_FIRST(&tbp->b_dep)) != NULL) {
				tbp->b_iocmd = BIO_WRITE;
				buf_start(tbp);
			}
			/*
			 * If the IO is via the VM then we do some
			 * special VM hackery (yuck).  Since the buffer's
			 * block size may not be page-aligned it is possible
			 * for a page to be shared between two buffers.  We
			 * have to get rid of the duplication when building
			 * the cluster.
			 */
			if (tbp->b_flags & B_VMIO) {
				vm_page_t m;

				if (i != 0) { /* if not first buffer */
					for (j = 0; j < tbp->b_npages; j += 1) {
						m = tbp->b_pages[j];
						if (m->flags & PG_BUSY) {
							bqrelse(tbp);
							goto finishcluster;
						}
					}
				}
				if (tbp->b_object != NULL)
					VM_OBJECT_LOCK(tbp->b_object);
				vm_page_lock_queues();
				for (j = 0; j < tbp->b_npages; j += 1) {
					m = tbp->b_pages[j];
					vm_page_io_start(m);
					vm_object_pip_add(m->object, 1);
					if ((bp->b_npages == 0) ||
					  (bp->b_pages[bp->b_npages - 1] != m)) {
						bp->b_pages[bp->b_npages] = m;
						bp->b_npages++;
					}
				}
				vm_page_unlock_queues();
				if (tbp->b_object != NULL)
					VM_OBJECT_UNLOCK(tbp->b_object);
			}
			bp->b_bcount += size;
			bp->b_bufsize += size;

			s = splbio();
			bundirty(tbp);
			tbp->b_flags &= ~B_DONE;
			tbp->b_ioflags &= ~BIO_ERROR;
			tbp->b_flags |= B_ASYNC;
			tbp->b_iocmd = BIO_WRITE;
			reassignbuf(tbp, tbp->b_vp);	/* put on clean list */
			VI_LOCK(tbp->b_vp);
			++tbp->b_vp->v_numoutput;
			VI_UNLOCK(tbp->b_vp);
			splx(s);
			BUF_KERNPROC(tbp);
			TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
				tbp, b_cluster.cluster_entry);
		}
	finishcluster:
		pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
			(vm_page_t *) bp->b_pages, bp->b_npages);
		if (bp->b_bufsize > bp->b_kvasize)
			panic(
			    "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
			    bp->b_bufsize, bp->b_kvasize);
		bp->b_kvasize = bp->b_bufsize;
		totalwritten += bp->b_bufsize;
		bp->b_dirtyoff = 0;
		bp->b_dirtyend = bp->b_bufsize;
		bawrite(bp);

		len -= i;
	}
	return totalwritten;
}

/*
 * Collect together all the buffers in a cluster.
 * Plus add one additional buffer.
 */
static struct cluster_save *
cluster_collectbufs(vp, last_bp)
	struct vnode *vp;
	struct buf *last_bp;
{
	struct cluster_save *buflist;
	struct buf *bp;
	daddr_t lbn;
	int i, len;

	len = vp->v_lastw - vp->v_cstart + 1;
	buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
	    M_SEGMENT, M_WAITOK);
	buflist->bs_nchildren = 0;
	buflist->bs_children = (struct buf **) (buflist + 1);
	for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
		(void) bread(vp, lbn, last_bp->b_bcount, NOCRED, &bp);
		buflist->bs_children[i] = bp;
		if (bp->b_blkno == bp->b_lblkno)
			VOP_BMAP(bp->b_vp, bp->b_lblkno, NULL, &bp->b_blkno,
				NULL, NULL);
	}
	buflist->bs_children[i] = bp = last_bp;
	if (bp->b_blkno == bp->b_lblkno)
		VOP_BMAP(bp->b_vp, bp->b_lblkno, NULL, &bp->b_blkno,
			NULL, NULL);
	buflist->bs_nchildren = i + 1;
	return (buflist);
}
OpenPOWER on IntegriCloud