xref: /freebsd/sys/kern/vfs_cluster.c (revision b1897c197c06ebd09ab26a462489bd331c96ce2e)
1 /*-
2  * Copyright (c) 1993
3  *	The Regents of the University of California.  All rights reserved.
4  * Modifications/enhancements:
5  * 	Copyright (c) 1995 John S. Dyson.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *	This product includes software developed by the University of
18  *	California, Berkeley and its contributors.
19  * 4. Neither the name of the University nor the names of its contributors
20  *    may be used to endorse or promote products derived from this software
21  *    without specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
34  *
35  *	@(#)vfs_cluster.c	8.7 (Berkeley) 2/13/94
36  * $Id: vfs_cluster.c,v 1.56 1998/03/07 21:35:28 dyson Exp $
37  */
38 
39 #include "opt_debug_cluster.h"
40 
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/proc.h>
44 #include <sys/buf.h>
45 #include <sys/vnode.h>
46 #include <sys/mount.h>
47 #include <sys/resourcevar.h>
48 #include <vm/vm.h>
49 #include <vm/vm_prot.h>
50 #include <vm/vm_object.h>
51 #include <vm/vm_page.h>
52 
53 #if defined(CLUSTERDEBUG)
54 #include <sys/sysctl.h>
55 #include <sys/kernel.h>
56 static int	rcluster= 0;
57 SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0, "");
58 #endif
59 
60 #ifdef notyet_block_reallocation_enabled
61 static struct cluster_save *
62 	cluster_collectbufs __P((struct vnode *vp, struct buf *last_bp));
63 #endif
64 static struct buf *
65 	cluster_rbuild __P((struct vnode *vp, u_quad_t filesize, daddr_t lbn,
66 			    daddr_t blkno, long size, int run, struct buf *fbp));
67 
68 extern vm_page_t	bogus_page;
69 
70 /*
71  * Maximum number of blocks for read-ahead.
72  */
73 #define MAXRA 32
74 
75 /*
76  * This replaces bread.
77  */
78 int
79 cluster_read(vp, filesize, lblkno, size, cred, totread, seqcount, bpp)
80 	struct vnode *vp;
81 	u_quad_t filesize;
82 	daddr_t lblkno;
83 	long size;
84 	struct ucred *cred;
85 	long totread;
86 	int seqcount;
87 	struct buf **bpp;
88 {
89 	struct buf *bp, *rbp, *reqbp;
90 	daddr_t blkno, origblkno;
91 	int error, num_ra;
92 	int i;
93 	int maxra, racluster;
94 	long origtotread;
95 
96 	error = 0;
97 	if (vp->v_maxio == 0)
98 		vp->v_maxio = DFLTPHYS;
99 
100 	/*
101 	 * Try to limit the amount of read-ahead by a few
102 	 * ad-hoc parameters.  This needs work!!!
103 	 */
104 	racluster = vp->v_maxio/size;
105 	maxra = 2 * racluster + (totread / size);
106 	if (maxra > MAXRA)
107 		maxra = MAXRA;
108 	if (maxra > nbuf/8)
109 		maxra = nbuf/8;
110 
111 	/*
112 	 * get the requested block
113 	 */
114 	*bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0);
115 	origblkno = lblkno;
116 	origtotread = totread;
117 
118 	/*
119 	 * if it is in the cache, then check to see if the reads have been
120 	 * sequential.  If they have, then try some read-ahead, otherwise
121 	 * back-off on prospective read-aheads.
122 	 */
123 	if (bp->b_flags & B_CACHE) {
124 		if (!seqcount) {
125 			return 0;
126 		} else if ((bp->b_flags & B_RAM) == 0) {
127 			return 0;
128 		} else {
129 			int s;
130 			struct buf *tbp;
131 			bp->b_flags &= ~B_RAM;
132 			/*
133 			 * We do the spl here so that there is no window
134 			 * between the incore and the b_usecount increment
135 			 * below.  We opt to keep the spl out of the loop
136 			 * for efficiency.
137 			 */
138 			s = splbio();
139 			for(i=1;i<maxra;i++) {
140 
141 				if (!(tbp = incore(vp, lblkno+i))) {
142 					break;
143 				}
144 
145 				/*
146 				 * Set another read-ahead mark so we know to check
147 				 * again.
148 				 */
149 				if (((i % racluster) == (racluster - 1)) ||
150 					(i == (maxra - 1)))
151 					tbp->b_flags |= B_RAM;
152 
153 				if ((tbp->b_usecount < 5) &&
154 					((tbp->b_flags & B_BUSY) == 0) &&
155 					(tbp->b_qindex == QUEUE_LRU)) {
156 					TAILQ_REMOVE(&bufqueues[QUEUE_LRU], tbp, b_freelist);
157 					TAILQ_INSERT_TAIL(&bufqueues[QUEUE_LRU], tbp, b_freelist);
158 				}
159 			}
160 			splx(s);
161 			if (i >= maxra) {
162 				return 0;
163 			}
164 			lblkno += i;
165 		}
166 		reqbp = bp = NULL;
167 	} else {
168 		u_quad_t firstread;
169 		firstread = (u_quad_t) lblkno * size;
170 		if (firstread + totread > filesize)
171 			totread = filesize - firstread;
172 		if (totread > size) {
173 			int nblks = 0;
174 			int ncontigafter;
175 			while (totread > 0) {
176 				nblks++;
177 				totread -= size;
178 			}
179 			if (nblks == 1)
180 				goto single_block_read;
181 			if (nblks > racluster)
182 				nblks = racluster;
183 
184 	    		error = VOP_BMAP(vp, lblkno, NULL,
185 				&blkno, &ncontigafter, NULL);
186 			if (error)
187 				goto single_block_read;
188 			if (blkno == -1)
189 				goto single_block_read;
190 			if (ncontigafter == 0)
191 				goto single_block_read;
192 			if (ncontigafter + 1 < nblks)
193 				nblks = ncontigafter + 1;
194 
195 			bp = cluster_rbuild(vp, filesize, lblkno,
196 				blkno, size, nblks, bp);
197 			lblkno += nblks;
198 		} else {
199 single_block_read:
200 			/*
201 			 * if it isn't in the cache, then get a chunk from
202 			 * disk if sequential, otherwise just get the block.
203 			 */
204 			bp->b_flags |= B_READ | B_RAM;
205 			lblkno += 1;
206 		}
207 	}
208 
209 	/*
210 	 * if we have been doing sequential I/O, then do some read-ahead
211 	 */
212 	rbp = NULL;
213 	if (seqcount && (lblkno < (origblkno + seqcount))) {
214 		/*
215 		 * we now build the read-ahead buffer if it is desirable.
216 		 */
217 		if (((u_quad_t)(lblkno + 1) * size) <= filesize &&
218 		    !(error = VOP_BMAP(vp, lblkno, NULL, &blkno, &num_ra, NULL)) &&
219 		    blkno != -1) {
220 			int nblksread;
221 			int ntoread = num_ra + 1;
222 			nblksread = (origtotread + size - 1) / size;
223 			if (seqcount < nblksread)
224 				seqcount = nblksread;
225 			if (seqcount < ntoread)
226 				ntoread = seqcount;
227 			if (num_ra) {
228 				rbp = cluster_rbuild(vp, filesize, lblkno,
229 					blkno, size, ntoread, NULL);
230 			} else {
231 				rbp = getblk(vp, lblkno, size, 0, 0);
232 				rbp->b_flags |= B_READ | B_ASYNC | B_RAM;
233 				rbp->b_blkno = blkno;
234 			}
235 		}
236 	}
237 
238 	/*
239 	 * handle the synchronous read
240 	 */
241 	if (bp) {
242 		if (bp->b_flags & (B_DONE | B_DELWRI)) {
243 			panic("cluster_read: DONE bp");
244 		} else {
245 #if defined(CLUSTERDEBUG)
246 			if (rcluster)
247 				printf("S(%d,%d,%d) ",
248 					bp->b_lblkno, bp->b_bcount, seqcount);
249 #endif
250 			if ((bp->b_flags & B_CLUSTER) == 0)
251 				vfs_busy_pages(bp, 0);
252 			error = VOP_STRATEGY(bp);
253 			curproc->p_stats->p_ru.ru_inblock++;
254 		}
255 	}
256 	/*
257 	 * and if we have read-aheads, do them too
258 	 */
259 	if (rbp) {
260 		if (error) {
261 			rbp->b_flags &= ~(B_ASYNC | B_READ);
262 			brelse(rbp);
263 		} else if (rbp->b_flags & B_CACHE) {
264 			rbp->b_flags &= ~(B_ASYNC | B_READ);
265 			bqrelse(rbp);
266 		} else {
267 #if defined(CLUSTERDEBUG)
268 			if (rcluster) {
269 				if (bp)
270 					printf("A+(%d,%d,%d,%d) ",
271 					rbp->b_lblkno, rbp->b_bcount,
272 					rbp->b_lblkno - origblkno,
273 					seqcount);
274 				else
275 					printf("A(%d,%d,%d,%d) ",
276 					rbp->b_lblkno, rbp->b_bcount,
277 					rbp->b_lblkno - origblkno,
278 					seqcount);
279 			}
280 #endif
281 
282 			if ((rbp->b_flags & B_CLUSTER) == 0)
283 				vfs_busy_pages(rbp, 0);
284 			(void) VOP_STRATEGY(rbp);
285 			curproc->p_stats->p_ru.ru_inblock++;
286 		}
287 	}
288 	if (reqbp)
289 		return (biowait(reqbp));
290 	else
291 		return (error);
292 }
293 
294 /*
295  * If blocks are contiguous on disk, use this to provide clustered
296  * read ahead.  We will read as many blocks as possible sequentially
297  * and then parcel them up into logical blocks in the buffer hash table.
298  */
299 static struct buf *
300 cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
301 	struct vnode *vp;
302 	u_quad_t filesize;
303 	daddr_t lbn;
304 	daddr_t blkno;
305 	long size;
306 	int run;
307 	struct buf *fbp;
308 {
309 	struct buf *bp, *tbp;
310 	daddr_t bn;
311 	int i, inc, j;
312 
313 #ifdef DIAGNOSTIC
314 	if (size != vp->v_mount->mnt_stat.f_iosize)
315 		panic("cluster_rbuild: size %d != filesize %d\n",
316 		    size, vp->v_mount->mnt_stat.f_iosize);
317 #endif
318 	/*
319 	 * avoid a division
320 	 */
321 	while ((u_quad_t) size * (lbn + run) > filesize) {
322 		--run;
323 	}
324 
325 	if (fbp) {
326 		tbp = fbp;
327 		tbp->b_flags |= B_READ;
328 	} else {
329 		tbp = getblk(vp, lbn, size, 0, 0);
330 		if (tbp->b_flags & B_CACHE)
331 			return tbp;
332 		tbp->b_flags |= B_ASYNC | B_READ | B_RAM;
333 	}
334 
335 	tbp->b_blkno = blkno;
336 	if( (tbp->b_flags & B_MALLOC) ||
337 		((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
338 		return tbp;
339 
340 	bp = trypbuf();
341 	if (bp == 0)
342 		return tbp;
343 
344 	(vm_offset_t) bp->b_data |= ((vm_offset_t) tbp->b_data) & PAGE_MASK;
345 	bp->b_flags = B_ASYNC | B_READ | B_CALL | B_BUSY | B_CLUSTER | B_VMIO;
346 	bp->b_iodone = cluster_callback;
347 	bp->b_blkno = blkno;
348 	bp->b_lblkno = lbn;
349 	pbgetvp(vp, bp);
350 
351 	TAILQ_INIT(&bp->b_cluster.cluster_head);
352 
353 	bp->b_bcount = 0;
354 	bp->b_bufsize = 0;
355 	bp->b_npages = 0;
356 
357 	if (vp->v_maxio == 0)
358 		vp->v_maxio = DFLTPHYS;
359 	inc = btodb(size);
360 	for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
361 		if (i != 0) {
362 			if ((bp->b_npages * PAGE_SIZE) +
363 				round_page(size) > vp->v_maxio)
364 				break;
365 
366 			if (incore(vp, lbn + i))
367 				break;
368 
369 			tbp = getblk(vp, lbn + i, size, 0, 0);
370 
371 			if ((tbp->b_flags & B_CACHE) ||
372 				(tbp->b_flags & B_VMIO) == 0) {
373 				bqrelse(tbp);
374 				break;
375 			}
376 
377 			for (j=0;j<tbp->b_npages;j++) {
378 				if (tbp->b_pages[j]->valid) {
379 					break;
380 				}
381 			}
382 
383 			if (j != tbp->b_npages) {
384 				/*
385 				 * force buffer to be re-constituted later
386 				 */
387 				tbp->b_flags |= B_RELBUF;
388 				brelse(tbp);
389 				break;
390 			}
391 
392 			if ((fbp && (i == 1)) || (i == (run - 1)))
393 				tbp->b_flags |= B_RAM;
394 			tbp->b_flags |= B_READ | B_ASYNC;
395 			if (tbp->b_blkno == tbp->b_lblkno) {
396 				tbp->b_blkno = bn;
397 			} else if (tbp->b_blkno != bn) {
398 				brelse(tbp);
399 				break;
400 			}
401 		}
402 		/* check for latent dependencies to be handled */
403 		if ((LIST_FIRST(&tbp->b_dep)) != NULL && bioops.io_start)
404 			(*bioops.io_start)(tbp);
405 		TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
406 			tbp, b_cluster.cluster_entry);
407 		for (j = 0; j < tbp->b_npages; j += 1) {
408 			vm_page_t m;
409 			m = tbp->b_pages[j];
410 			++m->busy;
411 			++m->object->paging_in_progress;
412 			if ((bp->b_npages == 0) ||
413 				(bp->b_pages[bp->b_npages-1] != m)) {
414 				bp->b_pages[bp->b_npages] = m;
415 				bp->b_npages++;
416 			}
417 			if ((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL)
418 				tbp->b_pages[j] = bogus_page;
419 		}
420 		bp->b_bcount += tbp->b_bcount;
421 		bp->b_bufsize += tbp->b_bufsize;
422 	}
423 
424 	for(j=0;j<bp->b_npages;j++) {
425 		if ((bp->b_pages[j]->valid & VM_PAGE_BITS_ALL) ==
426 			VM_PAGE_BITS_ALL)
427 			bp->b_pages[j] = bogus_page;
428 	}
429 	if (bp->b_bufsize > bp->b_kvasize)
430 		panic("cluster_rbuild: b_bufsize(%d) > b_kvasize(%d)\n",
431 			bp->b_bufsize, bp->b_kvasize);
432 	bp->b_kvasize = bp->b_bufsize;
433 
434 	pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
435 		(vm_page_t *)bp->b_pages, bp->b_npages);
436 	return (bp);
437 }
438 
439 /*
440  * Cleanup after a clustered read or write.
441  * This is complicated by the fact that any of the buffers might have
442  * extra memory (if there were no empty buffer headers at allocbuf time)
443  * that we will need to shift around.
444  */
445 void
446 cluster_callback(bp)
447 	struct buf *bp;
448 {
449 	struct buf *nbp, *tbp;
450 	int error = 0;
451 
452 	/*
453 	 * Must propogate errors to all the components.
454 	 */
455 	if (bp->b_flags & B_ERROR)
456 		error = bp->b_error;
457 
458 	pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);
459 	/*
460 	 * Move memory from the large cluster buffer into the component
461 	 * buffers and mark IO as done on these.
462 	 */
463 	for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
464 		tbp; tbp = nbp) {
465 		nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
466 		if (error) {
467 			tbp->b_flags |= B_ERROR;
468 			tbp->b_error = error;
469 		} else
470 		    tbp->b_dirtyoff = tbp->b_dirtyend = 0;
471 		biodone(tbp);
472 	}
473 	relpbuf(bp);
474 }
475 
476 /*
477  * Do clustered write for FFS.
478  *
479  * Three cases:
480  *	1. Write is not sequential (write asynchronously)
481  *	Write is sequential:
482  *	2.	beginning of cluster - begin cluster
483  *	3.	middle of a cluster - add to cluster
484  *	4.	end of a cluster - asynchronously write cluster
485  */
486 void
487 cluster_write(bp, filesize)
488 	struct buf *bp;
489 	u_quad_t filesize;
490 {
491 	struct vnode *vp;
492 	daddr_t lbn;
493 	int maxclen, cursize;
494 	int lblocksize;
495 	int async;
496 
497 	vp = bp->b_vp;
498 	if (vp->v_maxio == 0)
499 		vp->v_maxio = DFLTPHYS;
500 	if (vp->v_type == VREG) {
501 		async = vp->v_mount->mnt_flag & MNT_ASYNC;
502 		lblocksize = vp->v_mount->mnt_stat.f_iosize;
503 	} else {
504 		async = 0;
505 		lblocksize = bp->b_bufsize;
506 	}
507 	lbn = bp->b_lblkno;
508 
509 	/* Initialize vnode to beginning of file. */
510 	if (lbn == 0)
511 		vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
512 
513 	if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
514 	    (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
515 		maxclen = vp->v_maxio / lblocksize - 1;
516 		if (vp->v_clen != 0) {
517 			/*
518 			 * Next block is not sequential.
519 			 *
520 			 * If we are not writing at end of file, the process
521 			 * seeked to another point in the file since its last
522 			 * write, or we have reached our maximum cluster size,
523 			 * then push the previous cluster. Otherwise try
524 			 * reallocating to make it sequential.
525 			 */
526 			cursize = vp->v_lastw - vp->v_cstart + 1;
527 #ifndef notyet_block_reallocation_enabled
528 			if (((u_quad_t)(lbn + 1) * lblocksize) != filesize ||
529 				lbn != vp->v_lastw + 1 ||
530 				vp->v_clen <= cursize) {
531 				if (!async)
532 					cluster_wbuild(vp, lblocksize,
533 						vp->v_cstart, cursize);
534 			}
535 #else
536 			if ((lbn + 1) * lblocksize != filesize ||
537 			    lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
538 				if (!async)
539 					cluster_wbuild(vp, lblocksize,
540 						vp->v_cstart, cursize);
541 			} else {
542 				struct buf **bpp, **endbp;
543 				struct cluster_save *buflist;
544 
545 				buflist = cluster_collectbufs(vp, bp);
546 				endbp = &buflist->bs_children
547 				    [buflist->bs_nchildren - 1];
548 				if (VOP_REALLOCBLKS(vp, buflist)) {
549 					/*
550 					 * Failed, push the previous cluster.
551 					 */
552 					for (bpp = buflist->bs_children;
553 					     bpp < endbp; bpp++)
554 						brelse(*bpp);
555 					free(buflist, M_SEGMENT);
556 					cluster_wbuild(vp, lblocksize,
557 					    vp->v_cstart, cursize);
558 				} else {
559 					/*
560 					 * Succeeded, keep building cluster.
561 					 */
562 					for (bpp = buflist->bs_children;
563 					     bpp <= endbp; bpp++)
564 						bdwrite(*bpp);
565 					free(buflist, M_SEGMENT);
566 					vp->v_lastw = lbn;
567 					vp->v_lasta = bp->b_blkno;
568 					return;
569 				}
570 			}
571 #endif /* notyet_block_reallocation_enabled */
572 		}
573 		/*
574 		 * Consider beginning a cluster. If at end of file, make
575 		 * cluster as large as possible, otherwise find size of
576 		 * existing cluster.
577 		 */
578 		if ((vp->v_type == VREG) &&
579 			((u_quad_t) (lbn + 1) * lblocksize) != filesize &&
580 		    (bp->b_blkno == bp->b_lblkno) &&
581 		    (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
582 		     bp->b_blkno == -1)) {
583 			bawrite(bp);
584 			vp->v_clen = 0;
585 			vp->v_lasta = bp->b_blkno;
586 			vp->v_cstart = lbn + 1;
587 			vp->v_lastw = lbn;
588 			return;
589 		}
590 		vp->v_clen = maxclen;
591 		if (!async && maxclen == 0) {	/* I/O not contiguous */
592 			vp->v_cstart = lbn + 1;
593 			bawrite(bp);
594 		} else {	/* Wait for rest of cluster */
595 			vp->v_cstart = lbn;
596 			bdwrite(bp);
597 		}
598 	} else if (lbn == vp->v_cstart + vp->v_clen) {
599 		/*
600 		 * At end of cluster, write it out.
601 		 */
602 		bdwrite(bp);
603 		cluster_wbuild(vp, lblocksize, vp->v_cstart, vp->v_clen + 1);
604 		vp->v_clen = 0;
605 		vp->v_cstart = lbn + 1;
606 	} else
607 		/*
608 		 * In the middle of a cluster, so just delay the I/O for now.
609 		 */
610 		bdwrite(bp);
611 	vp->v_lastw = lbn;
612 	vp->v_lasta = bp->b_blkno;
613 }
614 
615 
616 /*
617  * This is an awful lot like cluster_rbuild...wish they could be combined.
618  * The last lbn argument is the current block on which I/O is being
619  * performed.  Check to see that it doesn't fall in the middle of
620  * the current block (if last_bp == NULL).
621  */
622 int
623 cluster_wbuild(vp, size, start_lbn, len)
624 	struct vnode *vp;
625 	long size;
626 	daddr_t start_lbn;
627 	int len;
628 {
629 	struct buf *bp, *tbp;
630 	int i, j, s;
631 	int totalwritten = 0;
632 	int dbsize = btodb(size);
633 	while (len > 0) {
634 		s = splbio();
635 		if (((tbp = gbincore(vp, start_lbn)) == NULL) ||
636 			((tbp->b_flags & (B_INVAL|B_BUSY|B_DELWRI)) != B_DELWRI)) {
637 			++start_lbn;
638 			--len;
639 			splx(s);
640 			continue;
641 		}
642 		bremfree(tbp);
643 		tbp->b_flags |= B_BUSY;
644 		tbp->b_flags &= ~B_DONE;
645 		splx(s);
646 
647 	/*
648 	 * Extra memory in the buffer, punt on this buffer. XXX we could
649 	 * handle this in most cases, but we would have to push the extra
650 	 * memory down to after our max possible cluster size and then
651 	 * potentially pull it back up if the cluster was terminated
652 	 * prematurely--too much hassle.
653 	 */
654 		if (((tbp->b_flags & (B_CLUSTEROK|B_MALLOC)) != B_CLUSTEROK) ||
655 			(tbp->b_bcount != tbp->b_bufsize) ||
656 			(tbp->b_bcount != size) ||
657 			len == 1) {
658 			totalwritten += tbp->b_bufsize;
659 			bawrite(tbp);
660 			++start_lbn;
661 			--len;
662 			continue;
663 		}
664 
665 		bp = trypbuf();
666 		if (bp == NULL) {
667 			totalwritten += tbp->b_bufsize;
668 			bawrite(tbp);
669 			++start_lbn;
670 			--len;
671 			continue;
672 		}
673 
674 		TAILQ_INIT(&bp->b_cluster.cluster_head);
675 		bp->b_bcount = 0;
676 		bp->b_bufsize = 0;
677 		bp->b_npages = 0;
678 		if (tbp->b_wcred != NOCRED) {
679 		    bp->b_wcred = tbp->b_wcred;
680 		    crhold(bp->b_wcred);
681 		}
682 
683 		bp->b_blkno = tbp->b_blkno;
684 		bp->b_lblkno = tbp->b_lblkno;
685 		(vm_offset_t) bp->b_data |= ((vm_offset_t) tbp->b_data) & PAGE_MASK;
686 		bp->b_flags |= B_CALL | B_BUSY | B_CLUSTER |
687 						(tbp->b_flags & (B_VMIO|B_NEEDCOMMIT));
688 		bp->b_iodone = cluster_callback;
689 		pbgetvp(vp, bp);
690 		for (i = 0; i < len; ++i, ++start_lbn) {
691 			if (i != 0) {
692 				s = splbio();
693 				if ((tbp = gbincore(vp, start_lbn)) == NULL) {
694 					splx(s);
695 					break;
696 				}
697 
698 				if ((tbp->b_flags & (B_VMIO|B_CLUSTEROK|B_INVAL|B_BUSY|B_DELWRI|B_NEEDCOMMIT)) != (B_DELWRI|B_CLUSTEROK|(bp->b_flags & (B_VMIO|B_NEEDCOMMIT)))) {
699 					splx(s);
700 					break;
701 				}
702 
703 				if (tbp->b_wcred != bp->b_wcred) {
704 					splx(s);
705 					break;
706 				}
707 
708 				if ((tbp->b_bcount != size) ||
709 					((bp->b_blkno + dbsize * i) != tbp->b_blkno) ||
710 					((tbp->b_npages + bp->b_npages) > (vp->v_maxio / PAGE_SIZE))) {
711 					splx(s);
712 					break;
713 				}
714 				bremfree(tbp);
715 				tbp->b_flags |= B_BUSY;
716 				tbp->b_flags &= ~B_DONE;
717 				splx(s);
718 			}
719 			/* check for latent dependencies to be handled */
720 			if ((LIST_FIRST(&tbp->b_dep)) != NULL &&
721 			    bioops.io_start)
722 				(*bioops.io_start)(tbp);
723 			if (tbp->b_flags & B_VMIO) {
724 				vm_page_t m;
725 
726 				if (i != 0) {
727 					for (j = 0; j < tbp->b_npages; j += 1) {
728 						m = tbp->b_pages[j];
729 						if (m->flags & PG_BUSY)
730 							goto finishcluster;
731 					}
732 				}
733 
734 				for (j = 0; j < tbp->b_npages; j += 1) {
735 					m = tbp->b_pages[j];
736 					++m->busy;
737 					++m->object->paging_in_progress;
738 					if ((bp->b_npages == 0) ||
739 						(bp->b_pages[bp->b_npages - 1] != m)) {
740 						bp->b_pages[bp->b_npages] = m;
741 						bp->b_npages++;
742 					}
743 				}
744 			}
745 			bp->b_bcount += size;
746 			bp->b_bufsize += size;
747 
748 			--numdirtybuffers;
749 			tbp->b_flags &= ~(B_READ | B_DONE | B_ERROR | B_DELWRI);
750 			tbp->b_flags |= B_ASYNC;
751 			s = splbio();
752 			reassignbuf(tbp, tbp->b_vp);	/* put on clean list */
753 			++tbp->b_vp->v_numoutput;
754 			splx(s);
755 			TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
756 				tbp, b_cluster.cluster_entry);
757 		}
758 	finishcluster:
759 		pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
760 			(vm_page_t *) bp->b_pages, bp->b_npages);
761 		if (bp->b_bufsize > bp->b_kvasize)
762 			panic("cluster_wbuild: b_bufsize(%d) > b_kvasize(%d)\n",
763 				bp->b_bufsize, bp->b_kvasize);
764 		bp->b_kvasize = bp->b_bufsize;
765 		totalwritten += bp->b_bufsize;
766 		bp->b_dirtyoff = 0;
767 		bp->b_dirtyend = bp->b_bufsize;
768 		bawrite(bp);
769 
770 		len -= i;
771 	}
772 	return totalwritten;
773 }
774 
775 #ifdef notyet_block_reallocation_enabled
776 /*
777  * Collect together all the buffers in a cluster.
778  * Plus add one additional buffer.
779  */
780 static struct cluster_save *
781 cluster_collectbufs(vp, last_bp)
782 	struct vnode *vp;
783 	struct buf *last_bp;
784 {
785 	struct cluster_save *buflist;
786 	daddr_t lbn;
787 	int i, len;
788 
789 	len = vp->v_lastw - vp->v_cstart + 1;
790 	buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
791 	    M_SEGMENT, M_WAITOK);
792 	buflist->bs_nchildren = 0;
793 	buflist->bs_children = (struct buf **) (buflist + 1);
794 	for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++)
795 		(void) bread(vp, lbn, last_bp->b_bcount, NOCRED,
796 		    &buflist->bs_children[i]);
797 	buflist->bs_children[i] = last_bp;
798 	buflist->bs_nchildren = i + 1;
799 	return (buflist);
800 }
801 #endif /* notyet_block_reallocation_enabled */
802