/*- * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #if defined(CLUSTERDEBUG) #include static int rcluster= 0; SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0, ""); #endif static MALLOC_DEFINE(M_SEGMENT, "cluster_save buffer", "cluster_save buffer"); static struct cluster_save * cluster_collectbufs __P((struct vnode *vp, struct buf *last_bp)); static struct buf * cluster_rbuild __P((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, ""); extern vm_page_t bogus_page; extern int cluster_pbuf_freecnt; /* * Maximum number of blocks for read-ahead. */ #define MAXRA 32 /* * This 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 error, num_ra; int i; int maxra, racluster; long origtotread; 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 = 2 * racluster + (totread / size); if (maxra > MAXRA) maxra = MAXRA; if (maxra > nbuf/8) maxra = nbuf/8; /* * get the requested block */ *bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0); origblkno = lblkno; origtotread = totread; /* * 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; struct buf *tbp; 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(); for (i = 1; i < maxra; i++) { if (!(tbp = incore(vp, lblkno+i))) { break; } /* * Set another read-ahead mark so we know * to check again. */ if (((i % racluster) == (racluster - 1)) || (i == (maxra - 1))) tbp->b_flags |= B_RAM; } splx(s); if (i >= maxra) { return 0; } lblkno += i; } reqbp = bp = NULL; } else { off_t firstread = bp->b_offset; KASSERT(bp->b_offset != NOOFFSET, ("cluster_read: no buffer offset")); if (firstread + totread > filesize) totread = filesize - firstread; if (totread > size) { int nblks = 0; int ncontigafter; while (totread > 0) { nblks++; totread -= size; } if (nblks == 1) goto single_block_read; if (nblks > racluster) nblks = racluster; error = VOP_BMAP(vp, lblkno, NULL, &blkno, &ncontigafter, NULL); if (error) goto single_block_read; if (blkno == -1) goto single_block_read; if (ncontigafter == 0) goto single_block_read; if (ncontigafter + 1 < nblks) nblks = ncontigafter + 1; bp = cluster_rbuild(vp, filesize, lblkno, blkno, size, nblks, bp); lblkno += (bp->b_bufsize / size); } else { single_block_read: /* * if it isn't in the cache, then get a chunk from * disk if sequential, otherwise just get the block. */ bp->b_flags |= B_READ | B_RAM; lblkno += 1; } } /* * if we have been doing sequential I/O, then do some read-ahead */ rbp = NULL; if (seqcount && (lblkno < (origblkno + seqcount))) { /* * we now build the read-ahead buffer if it is desirable. */ if (((u_quad_t)(lblkno + 1) * size) <= filesize && !(error = VOP_BMAP(vp, lblkno, NULL, &blkno, &num_ra, NULL)) && blkno != -1) { int nblksread; int ntoread = num_ra + 1; nblksread = (origtotread + size - 1) / size; if (seqcount < nblksread) seqcount = nblksread; if (seqcount < ntoread) ntoread = seqcount; if (num_ra) { rbp = cluster_rbuild(vp, filesize, lblkno, blkno, size, ntoread, NULL); } else { rbp = getblk(vp, lblkno, size, 0, 0); rbp->b_flags |= B_READ | B_ASYNC | B_RAM; rbp->b_blkno = blkno; } } } /* * handle the synchronous read */ if (bp) { #if defined(CLUSTERDEBUG) if (rcluster) printf("S(%ld,%ld,%d) ", (long)bp->b_lblkno, bp->b_bcount, seqcount); #endif if ((bp->b_flags & B_CLUSTER) == 0) vfs_busy_pages(bp, 0); bp->b_flags &= ~(B_ERROR|B_INVAL); if (bp->b_flags & (B_ASYNC|B_CALL)) BUF_KERNPROC(bp); error = VOP_STRATEGY(vp, bp); curproc->p_stats->p_ru.ru_inblock++; } /* * and if we have read-aheads, do them too */ if (rbp) { if (error) { rbp->b_flags &= ~(B_ASYNC | B_READ); brelse(rbp); } else if (rbp->b_flags & B_CACHE) { rbp->b_flags &= ~(B_ASYNC | B_READ); bqrelse(rbp); } else { #if defined(CLUSTERDEBUG) if (rcluster) { if (bp) printf("A+(%ld,%ld,%ld,%d) ", (long)rbp->b_lblkno, rbp->b_bcount, (long)(rbp->b_lblkno - origblkno), seqcount); else printf("A(%ld,%ld,%ld,%d) ", (long)rbp->b_lblkno, rbp->b_bcount, (long)(rbp->b_lblkno - origblkno), seqcount); } #endif if ((rbp->b_flags & B_CLUSTER) == 0) vfs_busy_pages(rbp, 0); rbp->b_flags &= ~(B_ERROR|B_INVAL); if (rbp->b_flags & (B_ASYNC|B_CALL)) BUF_KERNPROC(rbp); (void) VOP_STRATEGY(vp, rbp); curproc->p_stats->p_ru.ru_inblock++; } } if (reqbp) return (biowait(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; 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_flags |= B_READ; } else { tbp = getblk(vp, lbn, size, 0, 0); if (tbp->b_flags & B_CACHE) return tbp; tbp->b_flags |= B_ASYNC | B_READ | B_RAM; } 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; bp->b_data = (char *)((vm_offset_t)bp->b_data | ((vm_offset_t)tbp->b_data & PAGE_MASK)); bp->b_flags = B_ASYNC | B_READ | B_CALL | B_CLUSTER | B_VMIO; 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; if ((tbp = incore(vp, lbn + i)) != NULL) { if (BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT)) break; BUF_UNLOCK(tbp); for (j = 0; j < tbp->b_npages; j++) if (tbp->b_pages[j]->valid) break; if (j != tbp->b_npages) break; if (tbp->b_bcount != size) break; } tbp = getblk(vp, lbn + i, size, 0, 0); if ((tbp->b_flags & B_CACHE) || (tbp->b_flags & B_VMIO) == 0) { bqrelse(tbp); break; } for (j = 0;j < tbp->b_npages; j++) if (tbp->b_pages[j]->valid) break; if (j != tbp->b_npages) { bqrelse(tbp); break; } if ((fbp && (i == 1)) || (i == (run - 1))) tbp->b_flags |= B_RAM; tbp->b_flags |= B_READ | B_ASYNC; 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); 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; } bp->b_bcount += tbp->b_bcount; bp->b_bufsize += tbp->b_bufsize; } for(j=0;jb_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; /* * Must propogate errors to all the components. */ if (bp->b_flags & B_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_flags |= B_ERROR; tbp->b_error = error; } else { tbp->b_dirtyoff = tbp->b_dirtyend = 0; tbp->b_flags &= ~(B_ERROR|B_INVAL); } biodone(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; /* fall through */ case 1: r = cluster_wbuild(vp, size, start_lbn, len); /* fall through */ default: /* fall through */ 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) struct buf *bp; u_quad_t filesize; { 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. */ 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) 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. */ for (bpp = buflist->bs_children; bpp < endbp; bpp++) brelse(*bpp); free(buflist, M_SEGMENT); 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. */ bdwrite(bp); cluster_wbuild_wb(vp, lblocksize, vp->v_cstart, vp->v_clen + 1); vp->v_clen = 0; vp->v_cstart = lbn + 1; } 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); while (len > 0) { s = splbio(); if (((tbp = gbincore(vp, start_lbn)) == NULL) || ((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) || BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT)) { ++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_CLUSTEROK) || (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_bufsize = 0; bp->b_npages = 0; if (tbp->b_wcred != NOCRED) { bp->b_wcred = tbp->b_wcred; crhold(bp->b_wcred); } bp->b_blkno = tbp->b_blkno; bp->b_lblkno = tbp->b_lblkno; bp->b_offset = tbp->b_offset; bp->b_data = (char *)((vm_offset_t)bp->b_data | ((vm_offset_t)tbp->b_data & PAGE_MASK)); bp->b_flags |= B_CALL | 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. */ if ((tbp = gbincore(vp, start_lbn)) == NULL) { splx(s); break; } /* * If it IS in core, but has different * characteristics, don't cluster with it. */ 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_wcred != bp->b_wcred || BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT)) { 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 && bioops.io_start) (*bioops.io_start)(tbp); /* * If the IO is via the VM then we do some * special VM hackery. (yuck) */ 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; } } } 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++; } } } bp->b_bcount += size; bp->b_bufsize += size; s = splbio(); bundirty(tbp); tbp->b_flags &= ~(B_READ | B_DONE | B_ERROR); tbp->b_flags |= B_ASYNC; reassignbuf(tbp, tbp->b_vp); /* put on clean list */ ++tbp->b_vp->v_numoutput; 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); }