3 * The Regents of the University of California. All rights reserved.
4 * Modifications/enhancements:
5 * Copyright (c) 1995 John S. Dyson. All rights reserved.
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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 * 4. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * @(#)vfs_cluster.c 8.7 (Berkeley) 2/13/94
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
37 #include "opt_debug_cluster.h"
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/kernel.h>
45 #include <sys/vnode.h>
46 #include <sys/malloc.h>
47 #include <sys/mount.h>
48 #include <sys/resourcevar.h>
49 #include <sys/vmmeter.h>
51 #include <vm/vm_object.h>
52 #include <vm/vm_page.h>
53 #include <sys/sysctl.h>
55 #if defined(CLUSTERDEBUG)
56 static int rcluster= 0;
57 SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0,
58 "Debug VFS clustering code");
61 static MALLOC_DEFINE(M_SEGMENT, "cl_savebuf", "cluster_save buffer");
63 static struct cluster_save *
64 cluster_collectbufs(struct vnode *vp, struct buf *last_bp);
66 cluster_rbuild(struct vnode *vp, u_quad_t filesize, daddr_t lbn,
67 daddr_t blkno, long size, int run, struct buf *fbp);
68 static void cluster_callback(struct buf *);
70 static int write_behind = 1;
71 SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0,
72 "Cluster write-behind; 0: disable, 1: enable, 2: backed off");
74 static int read_max = 8;
75 SYSCTL_INT(_vfs, OID_AUTO, read_max, CTLFLAG_RW, &read_max, 0,
76 "Cluster read-ahead max block count");
78 /* Page expended to mark partially backed buffers */
79 extern vm_page_t bogus_page;
82 * Read data to a buf, including read-ahead if we find this to be beneficial.
83 * cluster_read replaces bread.
86 cluster_read(vp, filesize, lblkno, size, cred, totread, seqcount, bpp)
96 struct buf *bp, *rbp, *reqbp;
97 daddr_t blkno, origblkno;
105 * Try to limit the amount of read-ahead by a few
106 * ad-hoc parameters. This needs work!!!
108 racluster = vp->v_mount->mnt_iosize_max / size;
110 maxra = min(read_max, maxra);
111 maxra = min(nbuf/8, maxra);
112 if (((u_quad_t)(lblkno + maxra + 1) * size) > filesize)
113 maxra = (filesize / size) - lblkno;
116 * get the requested block
118 *bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0, 0);
122 * if it is in the cache, then check to see if the reads have been
123 * sequential. If they have, then try some read-ahead, otherwise
124 * back-off on prospective read-aheads.
126 if (bp->b_flags & B_CACHE) {
129 } else if ((bp->b_flags & B_RAM) == 0) {
132 bp->b_flags &= ~B_RAM;
134 for (i = 1; i < maxra; i++) {
136 * Stop if the buffer does not exist or it
137 * is invalid (about to go away?)
139 rbp = gbincore(&vp->v_bufobj, lblkno+i);
140 if (rbp == NULL || (rbp->b_flags & B_INVAL))
144 * Set another read-ahead mark so we know
145 * to check again. (If we can lock the
146 * buffer without waiting)
148 if ((((i % racluster) == (racluster - 1)) ||
150 && (0 == BUF_LOCK(rbp,
151 LK_EXCLUSIVE | LK_NOWAIT, NULL))) {
152 rbp->b_flags |= B_RAM;
164 * If it isn't in the cache, then get a chunk from
165 * disk if sequential, otherwise just get the block.
168 off_t firstread = bp->b_offset;
171 KASSERT(bp->b_offset != NOOFFSET,
172 ("cluster_read: no buffer offset"));
177 * Compute the total number of blocks that we should read
180 if (firstread + totread > filesize)
181 totread = filesize - firstread;
182 nblks = howmany(totread, size);
183 if (nblks > racluster)
187 * Now compute the number of contiguous blocks.
190 error = VOP_BMAP(vp, lblkno, NULL,
191 &blkno, &ncontig, NULL);
193 * If this failed to map just do the original block.
195 if (error || blkno == -1)
200 * If we have contiguous data available do a cluster
201 * otherwise just read the requested block.
204 /* Account for our first block. */
205 ncontig = min(ncontig + 1, nblks);
208 bp = cluster_rbuild(vp, filesize, lblkno,
209 blkno, size, nblks, bp);
210 lblkno += (bp->b_bufsize / size);
212 bp->b_flags |= B_RAM;
213 bp->b_iocmd = BIO_READ;
219 * handle the synchronous read so that it is available ASAP.
222 if ((bp->b_flags & B_CLUSTER) == 0) {
223 vfs_busy_pages(bp, 0);
225 bp->b_flags &= ~B_INVAL;
226 bp->b_ioflags &= ~BIO_ERROR;
227 if ((bp->b_flags & B_ASYNC) || bp->b_iodone != NULL)
229 bp->b_iooffset = dbtob(bp->b_blkno);
231 curthread->td_ru.ru_inblock++;
235 * If we have been doing sequential I/O, then do some read-ahead.
237 while (lblkno < (origblkno + maxra)) {
238 error = VOP_BMAP(vp, lblkno, NULL, &blkno, &ncontig, NULL);
246 * We could throttle ncontig here by maxra but we might as
247 * well read the data if it is contiguous. We're throttled
248 * by racluster anyway.
251 ncontig = min(ncontig + 1, racluster);
252 rbp = cluster_rbuild(vp, filesize, lblkno, blkno,
253 size, ncontig, NULL);
254 lblkno += (rbp->b_bufsize / size);
255 if (rbp->b_flags & B_DELWRI) {
260 rbp = getblk(vp, lblkno, size, 0, 0, 0);
262 if (rbp->b_flags & B_DELWRI) {
266 rbp->b_flags |= B_ASYNC | B_RAM;
267 rbp->b_iocmd = BIO_READ;
268 rbp->b_blkno = blkno;
270 if (rbp->b_flags & B_CACHE) {
271 rbp->b_flags &= ~B_ASYNC;
275 if ((rbp->b_flags & B_CLUSTER) == 0) {
276 vfs_busy_pages(rbp, 0);
278 rbp->b_flags &= ~B_INVAL;
279 rbp->b_ioflags &= ~BIO_ERROR;
280 if ((rbp->b_flags & B_ASYNC) || rbp->b_iodone != NULL)
282 rbp->b_iooffset = dbtob(rbp->b_blkno);
284 curthread->td_ru.ru_inblock++;
288 return (bufwait(reqbp));
294 * If blocks are contiguous on disk, use this to provide clustered
295 * read ahead. We will read as many blocks as possible sequentially
296 * and then parcel them up into logical blocks in the buffer hash table.
299 cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
308 struct buf *bp, *tbp;
312 KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
313 ("cluster_rbuild: size %ld != filesize %jd\n",
314 size, (intmax_t)vp->v_mount->mnt_stat.f_iosize));
319 while ((u_quad_t) size * (lbn + run) > filesize) {
325 tbp->b_iocmd = BIO_READ;
327 tbp = getblk(vp, lbn, size, 0, 0, 0);
328 if (tbp->b_flags & B_CACHE)
330 tbp->b_flags |= B_ASYNC | B_RAM;
331 tbp->b_iocmd = BIO_READ;
334 tbp->b_blkno = blkno;
335 if( (tbp->b_flags & B_MALLOC) ||
336 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
339 bp = trypbuf(&cluster_pbuf_freecnt);
344 * We are synthesizing a buffer out of vm_page_t's, but
345 * if the block size is not page aligned then the starting
346 * address may not be either. Inherit the b_data offset
347 * from the original buffer.
349 bp->b_data = (char *)((vm_offset_t)bp->b_data |
350 ((vm_offset_t)tbp->b_data & PAGE_MASK));
351 bp->b_flags = B_ASYNC | B_CLUSTER | B_VMIO;
352 bp->b_iocmd = BIO_READ;
353 bp->b_iodone = cluster_callback;
356 bp->b_offset = tbp->b_offset;
357 KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
360 TAILQ_INIT(&bp->b_cluster.cluster_head);
367 for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
369 if ((bp->b_npages * PAGE_SIZE) +
370 round_page(size) > vp->v_mount->mnt_iosize_max) {
374 tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT);
376 /* Don't wait around for locked bufs. */
381 * Stop scanning if the buffer is fully valid
382 * (marked B_CACHE), or locked (may be doing a
383 * background write), or if the buffer is not
384 * VMIO backed. The clustering code can only deal
385 * with VMIO-backed buffers.
388 if ((tbp->b_vflags & BV_BKGRDINPROG) ||
389 (tbp->b_flags & B_CACHE) ||
390 (tbp->b_flags & B_VMIO) == 0) {
398 * The buffer must be completely invalid in order to
399 * take part in the cluster. If it is partially valid
402 VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
403 for (j = 0;j < tbp->b_npages; j++) {
404 VM_OBJECT_LOCK_ASSERT(tbp->b_pages[j]->object,
406 if (tbp->b_pages[j]->valid)
409 VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
410 if (j != tbp->b_npages) {
416 * Set a read-ahead mark as appropriate
418 if ((fbp && (i == 1)) || (i == (run - 1)))
419 tbp->b_flags |= B_RAM;
422 * Set the buffer up for an async read (XXX should
423 * we do this only if we do not wind up brelse()ing?).
424 * Set the block number if it isn't set, otherwise
425 * if it is make sure it matches the block number we
428 tbp->b_flags |= B_ASYNC;
429 tbp->b_iocmd = BIO_READ;
430 if (tbp->b_blkno == tbp->b_lblkno) {
432 } else if (tbp->b_blkno != bn) {
438 * XXX fbp from caller may not be B_ASYNC, but we are going
439 * to biodone() it in cluster_callback() anyway
442 TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
443 tbp, b_cluster.cluster_entry);
444 VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
445 for (j = 0; j < tbp->b_npages; j += 1) {
449 vm_object_pip_add(m->object, 1);
450 if ((bp->b_npages == 0) ||
451 (bp->b_pages[bp->b_npages-1] != m)) {
452 bp->b_pages[bp->b_npages] = m;
455 if ((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL)
456 tbp->b_pages[j] = bogus_page;
458 VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
460 * XXX shouldn't this be += size for both, like in
463 * Don't inherit tbp->b_bufsize as it may be larger due to
464 * a non-page-aligned size. Instead just aggregate using
467 if (tbp->b_bcount != size)
468 printf("warning: tbp->b_bcount wrong %ld vs %ld\n", tbp->b_bcount, size);
469 if (tbp->b_bufsize != size)
470 printf("warning: tbp->b_bufsize wrong %ld vs %ld\n", tbp->b_bufsize, size);
471 bp->b_bcount += size;
472 bp->b_bufsize += size;
476 * Fully valid pages in the cluster are already good and do not need
477 * to be re-read from disk. Replace the page with bogus_page
479 VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
480 for (j = 0; j < bp->b_npages; j++) {
481 VM_OBJECT_LOCK_ASSERT(bp->b_pages[j]->object, MA_OWNED);
482 if ((bp->b_pages[j]->valid & VM_PAGE_BITS_ALL) ==
484 bp->b_pages[j] = bogus_page;
487 VM_OBJECT_UNLOCK(bp->b_bufobj->bo_object);
488 if (bp->b_bufsize > bp->b_kvasize)
489 panic("cluster_rbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
490 bp->b_bufsize, bp->b_kvasize);
491 bp->b_kvasize = bp->b_bufsize;
493 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
494 (vm_page_t *)bp->b_pages, bp->b_npages);
499 * Cleanup after a clustered read or write.
500 * This is complicated by the fact that any of the buffers might have
501 * extra memory (if there were no empty buffer headers at allocbuf time)
502 * that we will need to shift around.
508 struct buf *nbp, *tbp;
512 * Must propogate errors to all the components.
514 if (bp->b_ioflags & BIO_ERROR)
517 pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);
519 * Move memory from the large cluster buffer into the component
520 * buffers and mark IO as done on these.
522 for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
524 nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
526 tbp->b_ioflags |= BIO_ERROR;
527 tbp->b_error = error;
529 tbp->b_dirtyoff = tbp->b_dirtyend = 0;
530 tbp->b_flags &= ~B_INVAL;
531 tbp->b_ioflags &= ~BIO_ERROR;
533 * XXX the bdwrite()/bqrelse() issued during
534 * cluster building clears B_RELBUF (see bqrelse()
535 * comment). If direct I/O was specified, we have
536 * to restore it here to allow the buffer and VM
539 if (tbp->b_flags & B_DIRECT)
540 tbp->b_flags |= B_RELBUF;
545 relpbuf(bp, &cluster_pbuf_freecnt);
551 * Implement modified write build for cluster.
553 * write_behind = 0 write behind disabled
554 * write_behind = 1 write behind normal (default)
555 * write_behind = 2 write behind backed-off
559 cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len)
563 switch(write_behind) {
570 r = cluster_wbuild(vp, size, start_lbn, len);
580 * Do clustered write for FFS.
583 * 1. Write is not sequential (write asynchronously)
584 * Write is sequential:
585 * 2. beginning of cluster - begin cluster
586 * 3. middle of a cluster - add to cluster
587 * 4. end of a cluster - asynchronously write cluster
590 cluster_write(struct vnode *vp, struct buf *bp, u_quad_t filesize, int seqcount)
593 int maxclen, cursize;
597 if (vp->v_type == VREG) {
598 async = vp->v_mount->mnt_kern_flag & MNTK_ASYNC;
599 lblocksize = vp->v_mount->mnt_stat.f_iosize;
602 lblocksize = bp->b_bufsize;
605 KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));
607 /* Initialize vnode to beginning of file. */
609 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
611 if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
612 (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
613 maxclen = vp->v_mount->mnt_iosize_max / lblocksize - 1;
614 if (vp->v_clen != 0) {
616 * Next block is not sequential.
618 * If we are not writing at end of file, the process
619 * seeked to another point in the file since its last
620 * write, or we have reached our maximum cluster size,
621 * then push the previous cluster. Otherwise try
622 * reallocating to make it sequential.
624 * Change to algorithm: only push previous cluster if
625 * it was sequential from the point of view of the
626 * seqcount heuristic, otherwise leave the buffer
627 * intact so we can potentially optimize the I/O
628 * later on in the buf_daemon or update daemon
631 cursize = vp->v_lastw - vp->v_cstart + 1;
632 if (((u_quad_t) bp->b_offset + lblocksize) != filesize ||
633 lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
634 if (!async && seqcount > 0) {
635 cluster_wbuild_wb(vp, lblocksize,
636 vp->v_cstart, cursize);
639 struct buf **bpp, **endbp;
640 struct cluster_save *buflist;
642 buflist = cluster_collectbufs(vp, bp);
643 endbp = &buflist->bs_children
644 [buflist->bs_nchildren - 1];
645 if (VOP_REALLOCBLKS(vp, buflist)) {
647 * Failed, push the previous cluster
648 * if *really* writing sequentially
649 * in the logical file (seqcount > 1),
650 * otherwise delay it in the hopes that
651 * the low level disk driver can
652 * optimize the write ordering.
654 for (bpp = buflist->bs_children;
657 free(buflist, M_SEGMENT);
659 cluster_wbuild_wb(vp,
660 lblocksize, vp->v_cstart,
665 * Succeeded, keep building cluster.
667 for (bpp = buflist->bs_children;
670 free(buflist, M_SEGMENT);
672 vp->v_lasta = bp->b_blkno;
678 * Consider beginning a cluster. If at end of file, make
679 * cluster as large as possible, otherwise find size of
682 if ((vp->v_type == VREG) &&
683 ((u_quad_t) bp->b_offset + lblocksize) != filesize &&
684 (bp->b_blkno == bp->b_lblkno) &&
685 (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
686 bp->b_blkno == -1)) {
689 vp->v_lasta = bp->b_blkno;
690 vp->v_cstart = lbn + 1;
694 vp->v_clen = maxclen;
695 if (!async && maxclen == 0) { /* I/O not contiguous */
696 vp->v_cstart = lbn + 1;
698 } else { /* Wait for rest of cluster */
702 } else if (lbn == vp->v_cstart + vp->v_clen) {
704 * At end of cluster, write it out if seqcount tells us we
705 * are operating sequentially, otherwise let the buf or
706 * update daemon handle it.
710 cluster_wbuild_wb(vp, lblocksize, vp->v_cstart, vp->v_clen + 1);
712 vp->v_cstart = lbn + 1;
713 } else if (vm_page_count_severe()) {
715 * We are low on memory, get it going NOW
720 * In the middle of a cluster, so just delay the I/O for now.
725 vp->v_lasta = bp->b_blkno;
730 * This is an awful lot like cluster_rbuild...wish they could be combined.
731 * The last lbn argument is the current block on which I/O is being
732 * performed. Check to see that it doesn't fall in the middle of
733 * the current block (if last_bp == NULL).
736 cluster_wbuild(vp, size, start_lbn, len)
742 struct buf *bp, *tbp;
744 int totalwritten = 0;
745 int dbsize = btodb(size);
749 * If the buffer is not delayed-write (i.e. dirty), or it
750 * is delayed-write but either locked or inval, it cannot
751 * partake in the clustered write.
754 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
755 (tbp->b_vflags & BV_BKGRDINPROG)) {
762 LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, VI_MTX(vp))) {
767 if ((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) {
773 if (tbp->b_pin_count > 0) {
780 tbp->b_flags &= ~B_DONE;
783 * Extra memory in the buffer, punt on this buffer.
784 * XXX we could handle this in most cases, but we would
785 * have to push the extra memory down to after our max
786 * possible cluster size and then potentially pull it back
787 * up if the cluster was terminated prematurely--too much
790 if (((tbp->b_flags & (B_CLUSTEROK | B_MALLOC | B_VMIO)) !=
791 (B_CLUSTEROK | B_VMIO)) ||
792 (tbp->b_bcount != tbp->b_bufsize) ||
793 (tbp->b_bcount != size) ||
795 ((bp = getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
796 totalwritten += tbp->b_bufsize;
804 * We got a pbuf to make the cluster in.
807 TAILQ_INIT(&bp->b_cluster.cluster_head);
811 if (tbp->b_wcred != NOCRED)
812 bp->b_wcred = crhold(tbp->b_wcred);
814 bp->b_blkno = tbp->b_blkno;
815 bp->b_lblkno = tbp->b_lblkno;
816 bp->b_offset = tbp->b_offset;
819 * We are synthesizing a buffer out of vm_page_t's, but
820 * if the block size is not page aligned then the starting
821 * address may not be either. Inherit the b_data offset
822 * from the original buffer.
824 bp->b_data = (char *)((vm_offset_t)bp->b_data |
825 ((vm_offset_t)tbp->b_data & PAGE_MASK));
826 bp->b_flags |= B_CLUSTER |
827 (tbp->b_flags & (B_VMIO | B_NEEDCOMMIT));
828 bp->b_iodone = cluster_callback;
831 * From this location in the file, scan forward to see
832 * if there are buffers with adjacent data that need to
833 * be written as well.
835 for (i = 0; i < len; ++i, ++start_lbn) {
836 if (i != 0) { /* If not the first buffer */
838 * If the adjacent data is not even in core it
839 * can't need to be written.
842 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
843 (tbp->b_vflags & BV_BKGRDINPROG)) {
849 * If it IS in core, but has different
850 * characteristics, or is locked (which
851 * means it could be undergoing a background
852 * I/O or be in a weird state), then don't
856 LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
860 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
861 B_INVAL | B_DELWRI | B_NEEDCOMMIT))
862 != (B_DELWRI | B_CLUSTEROK |
863 (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
864 tbp->b_wcred != bp->b_wcred) {
870 * Check that the combined cluster
871 * would make sense with regard to pages
872 * and would not be too large
874 if ((tbp->b_bcount != size) ||
875 ((bp->b_blkno + (dbsize * i)) !=
877 ((tbp->b_npages + bp->b_npages) >
878 (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
884 * Do not pull in pinned buffers.
886 if (tbp->b_pin_count > 0) {
892 * Ok, it's passed all the tests,
893 * so remove it from the free list
894 * and mark it busy. We will use it.
897 tbp->b_flags &= ~B_DONE;
898 } /* end of code for non-first buffers only */
900 * If the IO is via the VM then we do some
901 * special VM hackery (yuck). Since the buffer's
902 * block size may not be page-aligned it is possible
903 * for a page to be shared between two buffers. We
904 * have to get rid of the duplication when building
907 if (tbp->b_flags & B_VMIO) {
910 VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
911 if (i != 0) { /* if not first buffer */
912 for (j = 0; j < tbp->b_npages; j += 1) {
914 if (m->oflags & VPO_BUSY) {
922 for (j = 0; j < tbp->b_npages; j += 1) {
925 vm_object_pip_add(m->object, 1);
926 if ((bp->b_npages == 0) ||
927 (bp->b_pages[bp->b_npages - 1] != m)) {
928 bp->b_pages[bp->b_npages] = m;
932 VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
934 bp->b_bcount += size;
935 bp->b_bufsize += size;
937 tbp->b_flags &= ~B_DONE;
938 tbp->b_ioflags &= ~BIO_ERROR;
939 tbp->b_flags |= B_ASYNC;
940 tbp->b_iocmd = BIO_WRITE;
941 reassignbuf(tbp); /* put on clean list */
942 bufobj_wref(tbp->b_bufobj);
944 TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
945 tbp, b_cluster.cluster_entry);
948 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
949 (vm_page_t *) bp->b_pages, bp->b_npages);
950 if (bp->b_bufsize > bp->b_kvasize)
952 "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
953 bp->b_bufsize, bp->b_kvasize);
954 bp->b_kvasize = bp->b_bufsize;
955 totalwritten += bp->b_bufsize;
957 bp->b_dirtyend = bp->b_bufsize;
966 * Collect together all the buffers in a cluster.
967 * Plus add one additional buffer.
969 static struct cluster_save *
970 cluster_collectbufs(vp, last_bp)
974 struct cluster_save *buflist;
979 len = vp->v_lastw - vp->v_cstart + 1;
980 buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
981 M_SEGMENT, M_WAITOK);
982 buflist->bs_nchildren = 0;
983 buflist->bs_children = (struct buf **) (buflist + 1);
984 for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
985 (void) bread(vp, lbn, last_bp->b_bcount, NOCRED, &bp);
986 buflist->bs_children[i] = bp;
987 if (bp->b_blkno == bp->b_lblkno)
988 VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno,
991 buflist->bs_children[i] = bp = last_bp;
992 if (bp->b_blkno == bp->b_lblkno)
993 VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL);
994 buflist->bs_nchildren = i + 1;