The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_cluster.c

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    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  * 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.
   18  *
   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
   29  * SUCH DAMAGE.
   30  *
   31  *      @(#)vfs_cluster.c       8.7 (Berkeley) 2/13/94
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD: releng/8.1/sys/kern/vfs_cluster.c 199583 2009-11-20 15:27:52Z jhb $");
   36 
   37 #include "opt_debug_cluster.h"
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/kernel.h>
   42 #include <sys/proc.h>
   43 #include <sys/bio.h>
   44 #include <sys/buf.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>
   50 #include <vm/vm.h>
   51 #include <vm/vm_object.h>
   52 #include <vm/vm_page.h>
   53 #include <sys/sysctl.h>
   54 
   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");
   59 #endif
   60 
   61 static MALLOC_DEFINE(M_SEGMENT, "cl_savebuf", "cluster_save buffer");
   62 
   63 static struct cluster_save *
   64         cluster_collectbufs(struct vnode *vp, struct buf *last_bp);
   65 static struct buf *
   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 *);
   69 
   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");
   73 
   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");
   77 
   78 /* Page expended to mark partially backed buffers */
   79 extern vm_page_t        bogus_page;
   80 
   81 /*
   82  * Read data to a buf, including read-ahead if we find this to be beneficial.
   83  * cluster_read replaces bread.
   84  */
   85 int
   86 cluster_read(vp, filesize, lblkno, size, cred, totread, seqcount, bpp)
   87         struct vnode *vp;
   88         u_quad_t filesize;
   89         daddr_t lblkno;
   90         long size;
   91         struct ucred *cred;
   92         long totread;
   93         int seqcount;
   94         struct buf **bpp;
   95 {
   96         struct buf *bp, *rbp, *reqbp;
   97         struct bufobj *bo;
   98         daddr_t blkno, origblkno;
   99         int maxra, racluster;
  100         int error, ncontig;
  101         int i;
  102 
  103         error = 0;
  104         bo = &vp->v_bufobj;
  105 
  106         /*
  107          * Try to limit the amount of read-ahead by a few
  108          * ad-hoc parameters.  This needs work!!!
  109          */
  110         racluster = vp->v_mount->mnt_iosize_max / size;
  111         maxra = seqcount;
  112         maxra = min(read_max, maxra);
  113         maxra = min(nbuf/8, maxra);
  114         if (((u_quad_t)(lblkno + maxra + 1) * size) > filesize)
  115                 maxra = (filesize / size) - lblkno;
  116 
  117         /*
  118          * get the requested block
  119          */
  120         *bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0, 0);
  121         origblkno = lblkno;
  122 
  123         /*
  124          * if it is in the cache, then check to see if the reads have been
  125          * sequential.  If they have, then try some read-ahead, otherwise
  126          * back-off on prospective read-aheads.
  127          */
  128         if (bp->b_flags & B_CACHE) {
  129                 if (!seqcount) {
  130                         return 0;
  131                 } else if ((bp->b_flags & B_RAM) == 0) {
  132                         return 0;
  133                 } else {
  134                         bp->b_flags &= ~B_RAM;
  135                         BO_LOCK(bo);
  136                         for (i = 1; i < maxra; i++) {
  137                                 /*
  138                                  * Stop if the buffer does not exist or it
  139                                  * is invalid (about to go away?)
  140                                  */
  141                                 rbp = gbincore(&vp->v_bufobj, lblkno+i);
  142                                 if (rbp == NULL || (rbp->b_flags & B_INVAL))
  143                                         break;
  144 
  145                                 /*
  146                                  * Set another read-ahead mark so we know 
  147                                  * to check again. (If we can lock the
  148                                  * buffer without waiting)
  149                                  */
  150                                 if ((((i % racluster) == (racluster - 1)) ||
  151                                     (i == (maxra - 1))) 
  152                                     && (0 == BUF_LOCK(rbp, 
  153                                         LK_EXCLUSIVE | LK_NOWAIT, NULL))) {
  154                                         rbp->b_flags |= B_RAM;
  155                                         BUF_UNLOCK(rbp);
  156                                 }                       
  157                         }
  158                         BO_UNLOCK(bo);
  159                         if (i >= maxra) {
  160                                 return 0;
  161                         }
  162                         lblkno += i;
  163                 }
  164                 reqbp = bp = NULL;
  165         /*
  166          * If it isn't in the cache, then get a chunk from
  167          * disk if sequential, otherwise just get the block.
  168          */
  169         } else {
  170                 off_t firstread = bp->b_offset;
  171                 int nblks;
  172 
  173                 KASSERT(bp->b_offset != NOOFFSET,
  174                     ("cluster_read: no buffer offset"));
  175 
  176                 ncontig = 0;
  177 
  178                 /*
  179                  * Compute the total number of blocks that we should read
  180                  * synchronously.
  181                  */
  182                 if (firstread + totread > filesize)
  183                         totread = filesize - firstread;
  184                 nblks = howmany(totread, size);
  185                 if (nblks > racluster)
  186                         nblks = racluster;
  187 
  188                 /*
  189                  * Now compute the number of contiguous blocks.
  190                  */
  191                 if (nblks > 1) {
  192                         error = VOP_BMAP(vp, lblkno, NULL,
  193                                 &blkno, &ncontig, NULL);
  194                         /*
  195                          * If this failed to map just do the original block.
  196                          */
  197                         if (error || blkno == -1)
  198                                 ncontig = 0;
  199                 }
  200 
  201                 /*
  202                  * If we have contiguous data available do a cluster
  203                  * otherwise just read the requested block.
  204                  */
  205                 if (ncontig) {
  206                         /* Account for our first block. */
  207                         ncontig = min(ncontig + 1, nblks);
  208                         if (ncontig < nblks)
  209                                 nblks = ncontig;
  210                         bp = cluster_rbuild(vp, filesize, lblkno,
  211                                 blkno, size, nblks, bp);
  212                         lblkno += (bp->b_bufsize / size);
  213                 } else {
  214                         bp->b_flags |= B_RAM;
  215                         bp->b_iocmd = BIO_READ;
  216                         lblkno += 1;
  217                 }
  218         }
  219 
  220         /*
  221          * handle the synchronous read so that it is available ASAP.
  222          */
  223         if (bp) {
  224                 if ((bp->b_flags & B_CLUSTER) == 0) {
  225                         vfs_busy_pages(bp, 0);
  226                 }
  227                 bp->b_flags &= ~B_INVAL;
  228                 bp->b_ioflags &= ~BIO_ERROR;
  229                 if ((bp->b_flags & B_ASYNC) || bp->b_iodone != NULL)
  230                         BUF_KERNPROC(bp);
  231                 bp->b_iooffset = dbtob(bp->b_blkno);
  232                 bstrategy(bp);
  233                 curthread->td_ru.ru_inblock++;
  234         }
  235 
  236         /*
  237          * If we have been doing sequential I/O, then do some read-ahead.
  238          */
  239         while (lblkno < (origblkno + maxra)) {
  240                 error = VOP_BMAP(vp, lblkno, NULL, &blkno, &ncontig, NULL);
  241                 if (error)
  242                         break;
  243 
  244                 if (blkno == -1)
  245                         break;
  246 
  247                 /*
  248                  * We could throttle ncontig here by maxra but we might as
  249                  * well read the data if it is contiguous.  We're throttled
  250                  * by racluster anyway.
  251                  */
  252                 if (ncontig) {
  253                         ncontig = min(ncontig + 1, racluster);
  254                         rbp = cluster_rbuild(vp, filesize, lblkno, blkno,
  255                                 size, ncontig, NULL);
  256                         lblkno += (rbp->b_bufsize / size);
  257                         if (rbp->b_flags & B_DELWRI) {
  258                                 bqrelse(rbp);
  259                                 continue;
  260                         }
  261                 } else {
  262                         rbp = getblk(vp, lblkno, size, 0, 0, 0);
  263                         lblkno += 1;
  264                         if (rbp->b_flags & B_DELWRI) {
  265                                 bqrelse(rbp);
  266                                 continue;
  267                         }
  268                         rbp->b_flags |= B_ASYNC | B_RAM;
  269                         rbp->b_iocmd = BIO_READ;
  270                         rbp->b_blkno = blkno;
  271                 }
  272                 if (rbp->b_flags & B_CACHE) {
  273                         rbp->b_flags &= ~B_ASYNC;
  274                         bqrelse(rbp);
  275                         continue;
  276                 }
  277                 if ((rbp->b_flags & B_CLUSTER) == 0) {
  278                         vfs_busy_pages(rbp, 0);
  279                 }
  280                 rbp->b_flags &= ~B_INVAL;
  281                 rbp->b_ioflags &= ~BIO_ERROR;
  282                 if ((rbp->b_flags & B_ASYNC) || rbp->b_iodone != NULL)
  283                         BUF_KERNPROC(rbp);
  284                 rbp->b_iooffset = dbtob(rbp->b_blkno);
  285                 bstrategy(rbp);
  286                 curthread->td_ru.ru_inblock++;
  287         }
  288 
  289         if (reqbp)
  290                 return (bufwait(reqbp));
  291         else
  292                 return (error);
  293 }
  294 
  295 /*
  296  * If blocks are contiguous on disk, use this to provide clustered
  297  * read ahead.  We will read as many blocks as possible sequentially
  298  * and then parcel them up into logical blocks in the buffer hash table.
  299  */
  300 static struct buf *
  301 cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
  302         struct vnode *vp;
  303         u_quad_t filesize;
  304         daddr_t lbn;
  305         daddr_t blkno;
  306         long size;
  307         int run;
  308         struct buf *fbp;
  309 {
  310         struct bufobj *bo;
  311         struct buf *bp, *tbp;
  312         daddr_t bn;
  313         off_t off;
  314         long tinc, tsize;
  315         int i, inc, j, toff;
  316 
  317         KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
  318             ("cluster_rbuild: size %ld != filesize %jd\n",
  319             size, (intmax_t)vp->v_mount->mnt_stat.f_iosize));
  320 
  321         /*
  322          * avoid a division
  323          */
  324         while ((u_quad_t) size * (lbn + run) > filesize) {
  325                 --run;
  326         }
  327 
  328         if (fbp) {
  329                 tbp = fbp;
  330                 tbp->b_iocmd = BIO_READ; 
  331         } else {
  332                 tbp = getblk(vp, lbn, size, 0, 0, 0);
  333                 if (tbp->b_flags & B_CACHE)
  334                         return tbp;
  335                 tbp->b_flags |= B_ASYNC | B_RAM;
  336                 tbp->b_iocmd = BIO_READ;
  337         }
  338         tbp->b_blkno = blkno;
  339         if( (tbp->b_flags & B_MALLOC) ||
  340                 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
  341                 return tbp;
  342 
  343         bp = trypbuf(&cluster_pbuf_freecnt);
  344         if (bp == 0)
  345                 return tbp;
  346 
  347         /*
  348          * We are synthesizing a buffer out of vm_page_t's, but
  349          * if the block size is not page aligned then the starting
  350          * address may not be either.  Inherit the b_data offset
  351          * from the original buffer.
  352          */
  353         bp->b_data = (char *)((vm_offset_t)bp->b_data |
  354             ((vm_offset_t)tbp->b_data & PAGE_MASK));
  355         bp->b_flags = B_ASYNC | B_CLUSTER | B_VMIO;
  356         bp->b_iocmd = BIO_READ;
  357         bp->b_iodone = cluster_callback;
  358         bp->b_blkno = blkno;
  359         bp->b_lblkno = lbn;
  360         bp->b_offset = tbp->b_offset;
  361         KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
  362         pbgetvp(vp, bp);
  363 
  364         TAILQ_INIT(&bp->b_cluster.cluster_head);
  365 
  366         bp->b_bcount = 0;
  367         bp->b_bufsize = 0;
  368         bp->b_npages = 0;
  369 
  370         inc = btodb(size);
  371         bo = &vp->v_bufobj;
  372         for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
  373                 if (i != 0) {
  374                         if ((bp->b_npages * PAGE_SIZE) +
  375                             round_page(size) > vp->v_mount->mnt_iosize_max) {
  376                                 break;
  377                         }
  378 
  379                         tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT);
  380 
  381                         /* Don't wait around for locked bufs. */
  382                         if (tbp == NULL)
  383                                 break;
  384 
  385                         /*
  386                          * Stop scanning if the buffer is fully valid
  387                          * (marked B_CACHE), or locked (may be doing a
  388                          * background write), or if the buffer is not
  389                          * VMIO backed.  The clustering code can only deal
  390                          * with VMIO-backed buffers.
  391                          */
  392                         BO_LOCK(bo);
  393                         if ((tbp->b_vflags & BV_BKGRDINPROG) ||
  394                             (tbp->b_flags & B_CACHE) ||
  395                             (tbp->b_flags & B_VMIO) == 0) {
  396                                 BO_UNLOCK(bo);
  397                                 bqrelse(tbp);
  398                                 break;
  399                         }
  400                         BO_UNLOCK(bo);
  401 
  402                         /*
  403                          * The buffer must be completely invalid in order to
  404                          * take part in the cluster.  If it is partially valid
  405                          * then we stop.
  406                          */
  407                         off = tbp->b_offset;
  408                         tsize = size;
  409                         VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
  410                         for (j = 0; tsize > 0; j++) {
  411                                 toff = off & PAGE_MASK;
  412                                 tinc = tsize;
  413                                 if (toff + tinc > PAGE_SIZE)
  414                                         tinc = PAGE_SIZE - toff;
  415                                 VM_OBJECT_LOCK_ASSERT(tbp->b_pages[j]->object,
  416                                     MA_OWNED);
  417                                 if ((tbp->b_pages[j]->valid &
  418                                     vm_page_bits(toff, tinc)) != 0)
  419                                         break;
  420                                 off += tinc;
  421                                 tsize -= tinc;
  422                         }
  423                         VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
  424                         if (tsize > 0) {
  425                                 bqrelse(tbp);
  426                                 break;
  427                         }
  428 
  429                         /*
  430                          * Set a read-ahead mark as appropriate
  431                          */
  432                         if ((fbp && (i == 1)) || (i == (run - 1)))
  433                                 tbp->b_flags |= B_RAM;
  434 
  435                         /*
  436                          * Set the buffer up for an async read (XXX should
  437                          * we do this only if we do not wind up brelse()ing?).
  438                          * Set the block number if it isn't set, otherwise
  439                          * if it is make sure it matches the block number we
  440                          * expect.
  441                          */
  442                         tbp->b_flags |= B_ASYNC;
  443                         tbp->b_iocmd = BIO_READ;
  444                         if (tbp->b_blkno == tbp->b_lblkno) {
  445                                 tbp->b_blkno = bn;
  446                         } else if (tbp->b_blkno != bn) {
  447                                 brelse(tbp);
  448                                 break;
  449                         }
  450                 }
  451                 /*
  452                  * XXX fbp from caller may not be B_ASYNC, but we are going
  453                  * to biodone() it in cluster_callback() anyway
  454                  */
  455                 BUF_KERNPROC(tbp);
  456                 TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
  457                         tbp, b_cluster.cluster_entry);
  458                 VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
  459                 for (j = 0; j < tbp->b_npages; j += 1) {
  460                         vm_page_t m;
  461                         m = tbp->b_pages[j];
  462                         vm_page_io_start(m);
  463                         vm_object_pip_add(m->object, 1);
  464                         if ((bp->b_npages == 0) ||
  465                                 (bp->b_pages[bp->b_npages-1] != m)) {
  466                                 bp->b_pages[bp->b_npages] = m;
  467                                 bp->b_npages++;
  468                         }
  469                         if (m->valid == VM_PAGE_BITS_ALL)
  470                                 tbp->b_pages[j] = bogus_page;
  471                 }
  472                 VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
  473                 /*
  474                  * Don't inherit tbp->b_bufsize as it may be larger due to
  475                  * a non-page-aligned size.  Instead just aggregate using
  476                  * 'size'.
  477                  */
  478                 if (tbp->b_bcount != size)
  479                         printf("warning: tbp->b_bcount wrong %ld vs %ld\n", tbp->b_bcount, size);
  480                 if (tbp->b_bufsize != size)
  481                         printf("warning: tbp->b_bufsize wrong %ld vs %ld\n", tbp->b_bufsize, size);
  482                 bp->b_bcount += size;
  483                 bp->b_bufsize += size;
  484         }
  485 
  486         /*
  487          * Fully valid pages in the cluster are already good and do not need
  488          * to be re-read from disk.  Replace the page with bogus_page
  489          */
  490         VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
  491         for (j = 0; j < bp->b_npages; j++) {
  492                 VM_OBJECT_LOCK_ASSERT(bp->b_pages[j]->object, MA_OWNED);
  493                 if (bp->b_pages[j]->valid == VM_PAGE_BITS_ALL)
  494                         bp->b_pages[j] = bogus_page;
  495         }
  496         VM_OBJECT_UNLOCK(bp->b_bufobj->bo_object);
  497         if (bp->b_bufsize > bp->b_kvasize)
  498                 panic("cluster_rbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
  499                     bp->b_bufsize, bp->b_kvasize);
  500         bp->b_kvasize = bp->b_bufsize;
  501 
  502         pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
  503                 (vm_page_t *)bp->b_pages, bp->b_npages);
  504         return (bp);
  505 }
  506 
  507 /*
  508  * Cleanup after a clustered read or write.
  509  * This is complicated by the fact that any of the buffers might have
  510  * extra memory (if there were no empty buffer headers at allocbuf time)
  511  * that we will need to shift around.
  512  */
  513 static void
  514 cluster_callback(bp)
  515         struct buf *bp;
  516 {
  517         struct buf *nbp, *tbp;
  518         int error = 0;
  519 
  520         /*
  521          * Must propogate errors to all the components.
  522          */
  523         if (bp->b_ioflags & BIO_ERROR)
  524                 error = bp->b_error;
  525 
  526         pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);
  527         /*
  528          * Move memory from the large cluster buffer into the component
  529          * buffers and mark IO as done on these.
  530          */
  531         for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
  532                 tbp; tbp = nbp) {
  533                 nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
  534                 if (error) {
  535                         tbp->b_ioflags |= BIO_ERROR;
  536                         tbp->b_error = error;
  537                 } else {
  538                         tbp->b_dirtyoff = tbp->b_dirtyend = 0;
  539                         tbp->b_flags &= ~B_INVAL;
  540                         tbp->b_ioflags &= ~BIO_ERROR;
  541                         /*
  542                          * XXX the bdwrite()/bqrelse() issued during
  543                          * cluster building clears B_RELBUF (see bqrelse()
  544                          * comment).  If direct I/O was specified, we have
  545                          * to restore it here to allow the buffer and VM
  546                          * to be freed.
  547                          */
  548                         if (tbp->b_flags & B_DIRECT)
  549                                 tbp->b_flags |= B_RELBUF;
  550                 }
  551                 bufdone(tbp);
  552         }
  553         pbrelvp(bp);
  554         relpbuf(bp, &cluster_pbuf_freecnt);
  555 }
  556 
  557 /*
  558  *      cluster_wbuild_wb:
  559  *
  560  *      Implement modified write build for cluster.
  561  *
  562  *              write_behind = 0        write behind disabled
  563  *              write_behind = 1        write behind normal (default)
  564  *              write_behind = 2        write behind backed-off
  565  */
  566 
  567 static __inline int
  568 cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len)
  569 {
  570         int r = 0;
  571 
  572         switch(write_behind) {
  573         case 2:
  574                 if (start_lbn < len)
  575                         break;
  576                 start_lbn -= len;
  577                 /* FALLTHROUGH */
  578         case 1:
  579                 r = cluster_wbuild(vp, size, start_lbn, len);
  580                 /* FALLTHROUGH */
  581         default:
  582                 /* FALLTHROUGH */
  583                 break;
  584         }
  585         return(r);
  586 }
  587 
  588 /*
  589  * Do clustered write for FFS.
  590  *
  591  * Three cases:
  592  *      1. Write is not sequential (write asynchronously)
  593  *      Write is sequential:
  594  *      2.      beginning of cluster - begin cluster
  595  *      3.      middle of a cluster - add to cluster
  596  *      4.      end of a cluster - asynchronously write cluster
  597  */
  598 void
  599 cluster_write(struct vnode *vp, struct buf *bp, u_quad_t filesize, int seqcount)
  600 {
  601         daddr_t lbn;
  602         int maxclen, cursize;
  603         int lblocksize;
  604         int async;
  605 
  606         if (vp->v_type == VREG) {
  607                 async = vp->v_mount->mnt_kern_flag & MNTK_ASYNC;
  608                 lblocksize = vp->v_mount->mnt_stat.f_iosize;
  609         } else {
  610                 async = 0;
  611                 lblocksize = bp->b_bufsize;
  612         }
  613         lbn = bp->b_lblkno;
  614         KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));
  615 
  616         /* Initialize vnode to beginning of file. */
  617         if (lbn == 0)
  618                 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
  619 
  620         if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
  621             (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
  622                 maxclen = vp->v_mount->mnt_iosize_max / lblocksize - 1;
  623                 if (vp->v_clen != 0) {
  624                         /*
  625                          * Next block is not sequential.
  626                          *
  627                          * If we are not writing at end of file, the process
  628                          * seeked to another point in the file since its last
  629                          * write, or we have reached our maximum cluster size,
  630                          * then push the previous cluster. Otherwise try
  631                          * reallocating to make it sequential.
  632                          *
  633                          * Change to algorithm: only push previous cluster if
  634                          * it was sequential from the point of view of the
  635                          * seqcount heuristic, otherwise leave the buffer 
  636                          * intact so we can potentially optimize the I/O
  637                          * later on in the buf_daemon or update daemon
  638                          * flush.
  639                          */
  640                         cursize = vp->v_lastw - vp->v_cstart + 1;
  641                         if (((u_quad_t) bp->b_offset + lblocksize) != filesize ||
  642                             lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
  643                                 if (!async && seqcount > 0) {
  644                                         cluster_wbuild_wb(vp, lblocksize,
  645                                                 vp->v_cstart, cursize);
  646                                 }
  647                         } else {
  648                                 struct buf **bpp, **endbp;
  649                                 struct cluster_save *buflist;
  650 
  651                                 buflist = cluster_collectbufs(vp, bp);
  652                                 endbp = &buflist->bs_children
  653                                     [buflist->bs_nchildren - 1];
  654                                 if (VOP_REALLOCBLKS(vp, buflist)) {
  655                                         /*
  656                                          * Failed, push the previous cluster
  657                                          * if *really* writing sequentially
  658                                          * in the logical file (seqcount > 1),
  659                                          * otherwise delay it in the hopes that
  660                                          * the low level disk driver can
  661                                          * optimize the write ordering.
  662                                          */
  663                                         for (bpp = buflist->bs_children;
  664                                              bpp < endbp; bpp++)
  665                                                 brelse(*bpp);
  666                                         free(buflist, M_SEGMENT);
  667                                         if (seqcount > 1) {
  668                                                 cluster_wbuild_wb(vp, 
  669                                                     lblocksize, vp->v_cstart, 
  670                                                     cursize);
  671                                         }
  672                                 } else {
  673                                         /*
  674                                          * Succeeded, keep building cluster.
  675                                          */
  676                                         for (bpp = buflist->bs_children;
  677                                              bpp <= endbp; bpp++)
  678                                                 bdwrite(*bpp);
  679                                         free(buflist, M_SEGMENT);
  680                                         vp->v_lastw = lbn;
  681                                         vp->v_lasta = bp->b_blkno;
  682                                         return;
  683                                 }
  684                         }
  685                 }
  686                 /*
  687                  * Consider beginning a cluster. If at end of file, make
  688                  * cluster as large as possible, otherwise find size of
  689                  * existing cluster.
  690                  */
  691                 if ((vp->v_type == VREG) &&
  692                         ((u_quad_t) bp->b_offset + lblocksize) != filesize &&
  693                     (bp->b_blkno == bp->b_lblkno) &&
  694                     (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
  695                      bp->b_blkno == -1)) {
  696                         bawrite(bp);
  697                         vp->v_clen = 0;
  698                         vp->v_lasta = bp->b_blkno;
  699                         vp->v_cstart = lbn + 1;
  700                         vp->v_lastw = lbn;
  701                         return;
  702                 }
  703                 vp->v_clen = maxclen;
  704                 if (!async && maxclen == 0) {   /* I/O not contiguous */
  705                         vp->v_cstart = lbn + 1;
  706                         bawrite(bp);
  707                 } else {        /* Wait for rest of cluster */
  708                         vp->v_cstart = lbn;
  709                         bdwrite(bp);
  710                 }
  711         } else if (lbn == vp->v_cstart + vp->v_clen) {
  712                 /*
  713                  * At end of cluster, write it out if seqcount tells us we
  714                  * are operating sequentially, otherwise let the buf or
  715                  * update daemon handle it.
  716                  */
  717                 bdwrite(bp);
  718                 if (seqcount > 1)
  719                         cluster_wbuild_wb(vp, lblocksize, vp->v_cstart, vp->v_clen + 1);
  720                 vp->v_clen = 0;
  721                 vp->v_cstart = lbn + 1;
  722         } else if (vm_page_count_severe()) {
  723                 /*
  724                  * We are low on memory, get it going NOW
  725                  */
  726                 bawrite(bp);
  727         } else {
  728                 /*
  729                  * In the middle of a cluster, so just delay the I/O for now.
  730                  */
  731                 bdwrite(bp);
  732         }
  733         vp->v_lastw = lbn;
  734         vp->v_lasta = bp->b_blkno;
  735 }
  736 
  737 
  738 /*
  739  * This is an awful lot like cluster_rbuild...wish they could be combined.
  740  * The last lbn argument is the current block on which I/O is being
  741  * performed.  Check to see that it doesn't fall in the middle of
  742  * the current block (if last_bp == NULL).
  743  */
  744 int
  745 cluster_wbuild(vp, size, start_lbn, len)
  746         struct vnode *vp;
  747         long size;
  748         daddr_t start_lbn;
  749         int len;
  750 {
  751         struct buf *bp, *tbp;
  752         struct bufobj *bo;
  753         int i, j;
  754         int totalwritten = 0;
  755         int dbsize = btodb(size);
  756 
  757         bo = &vp->v_bufobj;
  758         while (len > 0) {
  759                 /*
  760                  * If the buffer is not delayed-write (i.e. dirty), or it
  761                  * is delayed-write but either locked or inval, it cannot
  762                  * partake in the clustered write.
  763                  */
  764                 BO_LOCK(bo);
  765                 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
  766                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  767                         BO_UNLOCK(bo);
  768                         ++start_lbn;
  769                         --len;
  770                         continue;
  771                 }
  772                 if (BUF_LOCK(tbp,
  773                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, BO_MTX(bo))) {
  774                         ++start_lbn;
  775                         --len;
  776                         continue;
  777                 }
  778                 if ((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) {
  779                         BUF_UNLOCK(tbp);
  780                         ++start_lbn;
  781                         --len;
  782                         continue;
  783                 }
  784                 if (tbp->b_pin_count >  0) {
  785                         BUF_UNLOCK(tbp);
  786                         ++start_lbn;
  787                         --len;
  788                         continue;
  789                 }
  790                 bremfree(tbp);
  791                 tbp->b_flags &= ~B_DONE;
  792 
  793                 /*
  794                  * Extra memory in the buffer, punt on this buffer.
  795                  * XXX we could handle this in most cases, but we would
  796                  * have to push the extra memory down to after our max
  797                  * possible cluster size and then potentially pull it back
  798                  * up if the cluster was terminated prematurely--too much
  799                  * hassle.
  800                  */
  801                 if (((tbp->b_flags & (B_CLUSTEROK | B_MALLOC | B_VMIO)) != 
  802                      (B_CLUSTEROK | B_VMIO)) ||
  803                   (tbp->b_bcount != tbp->b_bufsize) ||
  804                   (tbp->b_bcount != size) ||
  805                   (len == 1) ||
  806                   ((bp = getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
  807                         totalwritten += tbp->b_bufsize;
  808                         bawrite(tbp);
  809                         ++start_lbn;
  810                         --len;
  811                         continue;
  812                 }
  813 
  814                 /*
  815                  * We got a pbuf to make the cluster in.
  816                  * so initialise it.
  817                  */
  818                 TAILQ_INIT(&bp->b_cluster.cluster_head);
  819                 bp->b_bcount = 0;
  820                 bp->b_bufsize = 0;
  821                 bp->b_npages = 0;
  822                 if (tbp->b_wcred != NOCRED)
  823                         bp->b_wcred = crhold(tbp->b_wcred);
  824 
  825                 bp->b_blkno = tbp->b_blkno;
  826                 bp->b_lblkno = tbp->b_lblkno;
  827                 bp->b_offset = tbp->b_offset;
  828 
  829                 /*
  830                  * We are synthesizing a buffer out of vm_page_t's, but
  831                  * if the block size is not page aligned then the starting
  832                  * address may not be either.  Inherit the b_data offset
  833                  * from the original buffer.
  834                  */
  835                 bp->b_data = (char *)((vm_offset_t)bp->b_data |
  836                     ((vm_offset_t)tbp->b_data & PAGE_MASK));
  837                 bp->b_flags |= B_CLUSTER |
  838                                 (tbp->b_flags & (B_VMIO | B_NEEDCOMMIT));
  839                 bp->b_iodone = cluster_callback;
  840                 pbgetvp(vp, bp);
  841                 /*
  842                  * From this location in the file, scan forward to see
  843                  * if there are buffers with adjacent data that need to
  844                  * be written as well.
  845                  */
  846                 for (i = 0; i < len; ++i, ++start_lbn) {
  847                         if (i != 0) { /* If not the first buffer */
  848                                 /*
  849                                  * If the adjacent data is not even in core it
  850                                  * can't need to be written.
  851                                  */
  852                                 BO_LOCK(bo);
  853                                 if ((tbp = gbincore(bo, start_lbn)) == NULL ||
  854                                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  855                                         BO_UNLOCK(bo);
  856                                         break;
  857                                 }
  858 
  859                                 /*
  860                                  * If it IS in core, but has different
  861                                  * characteristics, or is locked (which
  862                                  * means it could be undergoing a background
  863                                  * I/O or be in a weird state), then don't
  864                                  * cluster with it.
  865                                  */
  866                                 if (BUF_LOCK(tbp,
  867                                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
  868                                     BO_MTX(bo)))
  869                                         break;
  870 
  871                                 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
  872                                     B_INVAL | B_DELWRI | B_NEEDCOMMIT))
  873                                     != (B_DELWRI | B_CLUSTEROK |
  874                                     (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
  875                                     tbp->b_wcred != bp->b_wcred) {
  876                                         BUF_UNLOCK(tbp);
  877                                         break;
  878                                 }
  879 
  880                                 /*
  881                                  * Check that the combined cluster
  882                                  * would make sense with regard to pages
  883                                  * and would not be too large
  884                                  */
  885                                 if ((tbp->b_bcount != size) ||
  886                                   ((bp->b_blkno + (dbsize * i)) !=
  887                                     tbp->b_blkno) ||
  888                                   ((tbp->b_npages + bp->b_npages) >
  889                                     (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
  890                                         BUF_UNLOCK(tbp);
  891                                         break;
  892                                 }
  893 
  894                                 /*
  895                                  * Do not pull in pinned buffers.
  896                                  */
  897                                 if (tbp->b_pin_count > 0) {
  898                                         BUF_UNLOCK(tbp);
  899                                         break;
  900                                 }
  901 
  902                                 /*
  903                                  * Ok, it's passed all the tests,
  904                                  * so remove it from the free list
  905                                  * and mark it busy. We will use it.
  906                                  */
  907                                 bremfree(tbp);
  908                                 tbp->b_flags &= ~B_DONE;
  909                         } /* end of code for non-first buffers only */
  910                         /*
  911                          * If the IO is via the VM then we do some
  912                          * special VM hackery (yuck).  Since the buffer's
  913                          * block size may not be page-aligned it is possible
  914                          * for a page to be shared between two buffers.  We
  915                          * have to get rid of the duplication when building
  916                          * the cluster.
  917                          */
  918                         if (tbp->b_flags & B_VMIO) {
  919                                 vm_page_t m;
  920 
  921                                 VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
  922                                 if (i != 0) { /* if not first buffer */
  923                                         for (j = 0; j < tbp->b_npages; j += 1) {
  924                                                 m = tbp->b_pages[j];
  925                                                 if (m->oflags & VPO_BUSY) {
  926                                                         VM_OBJECT_UNLOCK(
  927                                                             tbp->b_object);
  928                                                         bqrelse(tbp);
  929                                                         goto finishcluster;
  930                                                 }
  931                                         }
  932                                 }
  933                                 for (j = 0; j < tbp->b_npages; j += 1) {
  934                                         m = tbp->b_pages[j];
  935                                         vm_page_io_start(m);
  936                                         vm_object_pip_add(m->object, 1);
  937                                         if ((bp->b_npages == 0) ||
  938                                           (bp->b_pages[bp->b_npages - 1] != m)) {
  939                                                 bp->b_pages[bp->b_npages] = m;
  940                                                 bp->b_npages++;
  941                                         }
  942                                 }
  943                                 VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
  944                         }
  945                         bp->b_bcount += size;
  946                         bp->b_bufsize += size;
  947                         bundirty(tbp);
  948                         tbp->b_flags &= ~B_DONE;
  949                         tbp->b_ioflags &= ~BIO_ERROR;
  950                         tbp->b_flags |= B_ASYNC;
  951                         tbp->b_iocmd = BIO_WRITE;
  952                         reassignbuf(tbp);               /* put on clean list */
  953                         bufobj_wref(tbp->b_bufobj);
  954                         BUF_KERNPROC(tbp);
  955                         TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
  956                                 tbp, b_cluster.cluster_entry);
  957                 }
  958         finishcluster:
  959                 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
  960                         (vm_page_t *) bp->b_pages, bp->b_npages);
  961                 if (bp->b_bufsize > bp->b_kvasize)
  962                         panic(
  963                             "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
  964                             bp->b_bufsize, bp->b_kvasize);
  965                 bp->b_kvasize = bp->b_bufsize;
  966                 totalwritten += bp->b_bufsize;
  967                 bp->b_dirtyoff = 0;
  968                 bp->b_dirtyend = bp->b_bufsize;
  969                 bawrite(bp);
  970 
  971                 len -= i;
  972         }
  973         return totalwritten;
  974 }
  975 
  976 /*
  977  * Collect together all the buffers in a cluster.
  978  * Plus add one additional buffer.
  979  */
  980 static struct cluster_save *
  981 cluster_collectbufs(vp, last_bp)
  982         struct vnode *vp;
  983         struct buf *last_bp;
  984 {
  985         struct cluster_save *buflist;
  986         struct buf *bp;
  987         daddr_t lbn;
  988         int i, len;
  989 
  990         len = vp->v_lastw - vp->v_cstart + 1;
  991         buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
  992             M_SEGMENT, M_WAITOK);
  993         buflist->bs_nchildren = 0;
  994         buflist->bs_children = (struct buf **) (buflist + 1);
  995         for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
  996                 (void) bread(vp, lbn, last_bp->b_bcount, NOCRED, &bp);
  997                 buflist->bs_children[i] = bp;
  998                 if (bp->b_blkno == bp->b_lblkno)
  999                         VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno,
 1000                                 NULL, NULL);
 1001         }
 1002         buflist->bs_children[i] = bp = last_bp;
 1003         if (bp->b_blkno == bp->b_lblkno)
 1004                 VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL);
 1005         buflist->bs_nchildren = i + 1;
 1006         return (buflist);
 1007 }

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