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/6.0/sys/kern/vfs_cluster.c 151777 2005-10-28 01:03:26Z ups $");
   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, "cluster_save buffer", "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         daddr_t blkno, origblkno;
   98         int maxra, racluster;
   99         int error, ncontig;
  100         int i;
  101 
  102         error = 0;
  103 
  104         /*
  105          * Try to limit the amount of read-ahead by a few
  106          * ad-hoc parameters.  This needs work!!!
  107          */
  108         racluster = vp->v_mount->mnt_iosize_max / size;
  109         maxra = seqcount;
  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;
  114 
  115         /*
  116          * get the requested block
  117          */
  118         *bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0, 0);
  119         origblkno = lblkno;
  120 
  121         /*
  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.
  125          */
  126         if (bp->b_flags & B_CACHE) {
  127                 if (!seqcount) {
  128                         return 0;
  129                 } else if ((bp->b_flags & B_RAM) == 0) {
  130                         return 0;
  131                 } else {
  132                         bp->b_flags &= ~B_RAM;
  133                         VI_LOCK(vp);
  134                         for (i = 1; i < maxra; i++) {
  135                                 /*
  136                                  * Stop if the buffer does not exist or it
  137                                  * is invalid (about to go away?)
  138                                  */
  139                                 rbp = gbincore(&vp->v_bufobj, lblkno+i);
  140                                 if (rbp == NULL || (rbp->b_flags & B_INVAL))
  141                                         break;
  142 
  143                                 /*
  144                                  * Set another read-ahead mark so we know 
  145                                  * to check again. (If we can lock the
  146                                  * buffer without waiting)
  147                                  */
  148                                 if ((((i % racluster) == (racluster - 1)) ||
  149                                     (i == (maxra - 1))) 
  150                                     && (0 == BUF_LOCK(rbp, 
  151                                         LK_EXCLUSIVE | LK_NOWAIT, NULL))) {
  152                                         rbp->b_flags |= B_RAM;
  153                                         BUF_UNLOCK(rbp);
  154                                 }                       
  155                         }
  156                         VI_UNLOCK(vp);
  157                         if (i >= maxra) {
  158                                 return 0;
  159                         }
  160                         lblkno += i;
  161                 }
  162                 reqbp = bp = NULL;
  163         /*
  164          * If it isn't in the cache, then get a chunk from
  165          * disk if sequential, otherwise just get the block.
  166          */
  167         } else {
  168                 off_t firstread = bp->b_offset;
  169                 int nblks;
  170 
  171                 KASSERT(bp->b_offset != NOOFFSET,
  172                     ("cluster_read: no buffer offset"));
  173 
  174                 ncontig = 0;
  175 
  176                 /*
  177                  * Compute the total number of blocks that we should read
  178                  * synchronously.
  179                  */
  180                 if (firstread + totread > filesize)
  181                         totread = filesize - firstread;
  182                 nblks = howmany(totread, size);
  183                 if (nblks > racluster)
  184                         nblks = racluster;
  185 
  186                 /*
  187                  * Now compute the number of contiguous blocks.
  188                  */
  189                 if (nblks > 1) {
  190                         error = VOP_BMAP(vp, lblkno, NULL,
  191                                 &blkno, &ncontig, NULL);
  192                         /*
  193                          * If this failed to map just do the original block.
  194                          */
  195                         if (error || blkno == -1)
  196                                 ncontig = 0;
  197                 }
  198 
  199                 /*
  200                  * If we have contiguous data available do a cluster
  201                  * otherwise just read the requested block.
  202                  */
  203                 if (ncontig) {
  204                         /* Account for our first block. */
  205                         ncontig = min(ncontig + 1, nblks);
  206                         if (ncontig < nblks)
  207                                 nblks = ncontig;
  208                         bp = cluster_rbuild(vp, filesize, lblkno,
  209                                 blkno, size, nblks, bp);
  210                         lblkno += (bp->b_bufsize / size);
  211                 } else {
  212                         bp->b_flags |= B_RAM;
  213                         bp->b_iocmd = BIO_READ;
  214                         lblkno += 1;
  215                 }
  216         }
  217 
  218         /*
  219          * handle the synchronous read so that it is available ASAP.
  220          */
  221         if (bp) {
  222                 if ((bp->b_flags & B_CLUSTER) == 0) {
  223                         vfs_busy_pages(bp, 0);
  224                 }
  225                 bp->b_flags &= ~B_INVAL;
  226                 bp->b_ioflags &= ~BIO_ERROR;
  227                 if ((bp->b_flags & B_ASYNC) || bp->b_iodone != NULL)
  228                         BUF_KERNPROC(bp);
  229                 bp->b_iooffset = dbtob(bp->b_blkno);
  230                 bstrategy(bp);
  231                 curproc->p_stats->p_ru.ru_inblock++;
  232         }
  233 
  234         /*
  235          * If we have been doing sequential I/O, then do some read-ahead.
  236          */
  237         while (lblkno < (origblkno + maxra)) {
  238                 error = VOP_BMAP(vp, lblkno, NULL, &blkno, &ncontig, NULL);
  239                 if (error)
  240                         break;
  241 
  242                 if (blkno == -1)
  243                         break;
  244 
  245                 /*
  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.
  249                  */
  250                 if (ncontig) {
  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) {
  256                                 bqrelse(rbp);
  257                                 continue;
  258                         }
  259                 } else {
  260                         rbp = getblk(vp, lblkno, size, 0, 0, 0);
  261                         lblkno += 1;
  262                         if (rbp->b_flags & B_DELWRI) {
  263                                 bqrelse(rbp);
  264                                 continue;
  265                         }
  266                         rbp->b_flags |= B_ASYNC | B_RAM;
  267                         rbp->b_iocmd = BIO_READ;
  268                         rbp->b_blkno = blkno;
  269                 }
  270                 if (rbp->b_flags & B_CACHE) {
  271                         rbp->b_flags &= ~B_ASYNC;
  272                         bqrelse(rbp);
  273                         continue;
  274                 }
  275                 if ((rbp->b_flags & B_CLUSTER) == 0) {
  276                         vfs_busy_pages(rbp, 0);
  277                 }
  278                 rbp->b_flags &= ~B_INVAL;
  279                 rbp->b_ioflags &= ~BIO_ERROR;
  280                 if ((rbp->b_flags & B_ASYNC) || rbp->b_iodone != NULL)
  281                         BUF_KERNPROC(rbp);
  282                 rbp->b_iooffset = dbtob(rbp->b_blkno);
  283                 bstrategy(rbp);
  284                 curproc->p_stats->p_ru.ru_inblock++;
  285         }
  286 
  287         if (reqbp)
  288                 return (bufwait(reqbp));
  289         else
  290                 return (error);
  291 }
  292 
  293 /*
  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.
  297  */
  298 static struct buf *
  299 cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
  300         struct vnode *vp;
  301         u_quad_t filesize;
  302         daddr_t lbn;
  303         daddr_t blkno;
  304         long size;
  305         int run;
  306         struct buf *fbp;
  307 {
  308         struct buf *bp, *tbp;
  309         daddr_t bn;
  310         int i, inc, j;
  311 
  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));
  315 
  316         /*
  317          * avoid a division
  318          */
  319         while ((u_quad_t) size * (lbn + run) > filesize) {
  320                 --run;
  321         }
  322 
  323         if (fbp) {
  324                 tbp = fbp;
  325                 tbp->b_iocmd = BIO_READ; 
  326         } else {
  327                 tbp = getblk(vp, lbn, size, 0, 0, 0);
  328                 if (tbp->b_flags & B_CACHE)
  329                         return tbp;
  330                 tbp->b_flags |= B_ASYNC | B_RAM;
  331                 tbp->b_iocmd = BIO_READ;
  332         }
  333 
  334         tbp->b_blkno = blkno;
  335         if( (tbp->b_flags & B_MALLOC) ||
  336                 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
  337                 return tbp;
  338 
  339         bp = trypbuf(&cluster_pbuf_freecnt);
  340         if (bp == 0)
  341                 return tbp;
  342 
  343         /*
  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.
  348          */
  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;
  354         bp->b_blkno = blkno;
  355         bp->b_lblkno = lbn;
  356         bp->b_offset = tbp->b_offset;
  357         KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
  358         pbgetvp(vp, bp);
  359 
  360         TAILQ_INIT(&bp->b_cluster.cluster_head);
  361 
  362         bp->b_bcount = 0;
  363         bp->b_bufsize = 0;
  364         bp->b_npages = 0;
  365 
  366         inc = btodb(size);
  367         for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
  368                 if (i != 0) {
  369                         if ((bp->b_npages * PAGE_SIZE) +
  370                             round_page(size) > vp->v_mount->mnt_iosize_max) {
  371                                 break;
  372                         }
  373 
  374                         tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT);
  375 
  376                         /* Don't wait around for locked bufs. */
  377                         if (tbp == NULL)
  378                                 break;
  379 
  380                         /*
  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.
  386                          */
  387                         VI_LOCK(vp);
  388                         if ((tbp->b_vflags & BV_BKGRDINPROG) ||
  389                             (tbp->b_flags & B_CACHE) ||
  390                             (tbp->b_flags & B_VMIO) == 0) {
  391                                 VI_UNLOCK(vp);
  392                                 bqrelse(tbp);
  393                                 break;
  394                         }
  395                         VI_UNLOCK(vp);
  396 
  397                         /*
  398                          * The buffer must be completely invalid in order to
  399                          * take part in the cluster.  If it is partially valid
  400                          * then we stop.
  401                          */
  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,
  405                                     MA_OWNED);
  406                                 if (tbp->b_pages[j]->valid)
  407                                         break;
  408                         }
  409                         VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
  410                         if (j != tbp->b_npages) {
  411                                 bqrelse(tbp);
  412                                 break;
  413                         }
  414 
  415                         /*
  416                          * Set a read-ahead mark as appropriate
  417                          */
  418                         if ((fbp && (i == 1)) || (i == (run - 1)))
  419                                 tbp->b_flags |= B_RAM;
  420 
  421                         /*
  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
  426                          * expect.
  427                          */
  428                         tbp->b_flags |= B_ASYNC;
  429                         tbp->b_iocmd = BIO_READ;
  430                         if (tbp->b_blkno == tbp->b_lblkno) {
  431                                 tbp->b_blkno = bn;
  432                         } else if (tbp->b_blkno != bn) {
  433                                 brelse(tbp);
  434                                 break;
  435                         }
  436                 }
  437                 /*
  438                  * XXX fbp from caller may not be B_ASYNC, but we are going
  439                  * to biodone() it in cluster_callback() anyway
  440                  */
  441                 BUF_KERNPROC(tbp);
  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) {
  446                         vm_page_t m;
  447                         m = tbp->b_pages[j];
  448                         vm_page_io_start(m);
  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;
  453                                 bp->b_npages++;
  454                         }
  455                         if ((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL)
  456                                 tbp->b_pages[j] = bogus_page;
  457                 }
  458                 VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
  459                 /*
  460                  * XXX shouldn't this be += size for both, like in
  461                  * cluster_wbuild()?
  462                  *
  463                  * Don't inherit tbp->b_bufsize as it may be larger due to
  464                  * a non-page-aligned size.  Instead just aggregate using
  465                  * 'size'.
  466                  */
  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;
  473         }
  474 
  475         /*
  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
  478          */
  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) ==
  483                     VM_PAGE_BITS_ALL) {
  484                         bp->b_pages[j] = bogus_page;
  485                 }
  486         }
  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;
  492 
  493         pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
  494                 (vm_page_t *)bp->b_pages, bp->b_npages);
  495         return (bp);
  496 }
  497 
  498 /*
  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.
  503  */
  504 static void
  505 cluster_callback(bp)
  506         struct buf *bp;
  507 {
  508         struct buf *nbp, *tbp;
  509         int error = 0;
  510 
  511         /*
  512          * Must propogate errors to all the components.
  513          */
  514         if (bp->b_ioflags & BIO_ERROR)
  515                 error = bp->b_error;
  516 
  517         pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);
  518         /*
  519          * Move memory from the large cluster buffer into the component
  520          * buffers and mark IO as done on these.
  521          */
  522         for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
  523                 tbp; tbp = nbp) {
  524                 nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
  525                 if (error) {
  526                         tbp->b_ioflags |= BIO_ERROR;
  527                         tbp->b_error = error;
  528                 } else {
  529                         tbp->b_dirtyoff = tbp->b_dirtyend = 0;
  530                         tbp->b_flags &= ~B_INVAL;
  531                         tbp->b_ioflags &= ~BIO_ERROR;
  532                         /*
  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
  537                          * to be freed.
  538                          */
  539                         if (tbp->b_flags & B_DIRECT)
  540                                 tbp->b_flags |= B_RELBUF;
  541                 }
  542                 bufdone(tbp);
  543         }
  544         pbrelvp(bp);
  545         relpbuf(bp, &cluster_pbuf_freecnt);
  546 }
  547 
  548 /*
  549  *      cluster_wbuild_wb:
  550  *
  551  *      Implement modified write build for cluster.
  552  *
  553  *              write_behind = 0        write behind disabled
  554  *              write_behind = 1        write behind normal (default)
  555  *              write_behind = 2        write behind backed-off
  556  */
  557 
  558 static __inline int
  559 cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len)
  560 {
  561         int r = 0;
  562 
  563         switch(write_behind) {
  564         case 2:
  565                 if (start_lbn < len)
  566                         break;
  567                 start_lbn -= len;
  568                 /* FALLTHROUGH */
  569         case 1:
  570                 r = cluster_wbuild(vp, size, start_lbn, len);
  571                 /* FALLTHROUGH */
  572         default:
  573                 /* FALLTHROUGH */
  574                 break;
  575         }
  576         return(r);
  577 }
  578 
  579 /*
  580  * Do clustered write for FFS.
  581  *
  582  * Three cases:
  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
  588  */
  589 void
  590 cluster_write(struct vnode *vp, struct buf *bp, u_quad_t filesize, int seqcount)
  591 {
  592         daddr_t lbn;
  593         int maxclen, cursize;
  594         int lblocksize;
  595         int async;
  596 
  597         if (vp->v_type == VREG) {
  598                 async = vp->v_mount->mnt_flag & MNT_ASYNC;
  599                 lblocksize = vp->v_mount->mnt_stat.f_iosize;
  600         } else {
  601                 async = 0;
  602                 lblocksize = bp->b_bufsize;
  603         }
  604         lbn = bp->b_lblkno;
  605         KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));
  606 
  607         /* Initialize vnode to beginning of file. */
  608         if (lbn == 0)
  609                 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
  610 
  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) {
  615                         /*
  616                          * Next block is not sequential.
  617                          *
  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.
  623                          *
  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
  629                          * flush.
  630                          */
  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);
  637                                 }
  638                         } else {
  639                                 struct buf **bpp, **endbp;
  640                                 struct cluster_save *buflist;
  641 
  642                                 buflist = cluster_collectbufs(vp, bp);
  643                                 endbp = &buflist->bs_children
  644                                     [buflist->bs_nchildren - 1];
  645                                 if (VOP_REALLOCBLKS(vp, buflist)) {
  646                                         /*
  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.
  653                                          */
  654                                         for (bpp = buflist->bs_children;
  655                                              bpp < endbp; bpp++)
  656                                                 brelse(*bpp);
  657                                         free(buflist, M_SEGMENT);
  658                                         if (seqcount > 1) {
  659                                                 cluster_wbuild_wb(vp, 
  660                                                     lblocksize, vp->v_cstart, 
  661                                                     cursize);
  662                                         }
  663                                 } else {
  664                                         /*
  665                                          * Succeeded, keep building cluster.
  666                                          */
  667                                         for (bpp = buflist->bs_children;
  668                                              bpp <= endbp; bpp++)
  669                                                 bdwrite(*bpp);
  670                                         free(buflist, M_SEGMENT);
  671                                         vp->v_lastw = lbn;
  672                                         vp->v_lasta = bp->b_blkno;
  673                                         return;
  674                                 }
  675                         }
  676                 }
  677                 /*
  678                  * Consider beginning a cluster. If at end of file, make
  679                  * cluster as large as possible, otherwise find size of
  680                  * existing cluster.
  681                  */
  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)) {
  687                         bawrite(bp);
  688                         vp->v_clen = 0;
  689                         vp->v_lasta = bp->b_blkno;
  690                         vp->v_cstart = lbn + 1;
  691                         vp->v_lastw = lbn;
  692                         return;
  693                 }
  694                 vp->v_clen = maxclen;
  695                 if (!async && maxclen == 0) {   /* I/O not contiguous */
  696                         vp->v_cstart = lbn + 1;
  697                         bawrite(bp);
  698                 } else {        /* Wait for rest of cluster */
  699                         vp->v_cstart = lbn;
  700                         bdwrite(bp);
  701                 }
  702         } else if (lbn == vp->v_cstart + vp->v_clen) {
  703                 /*
  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.
  707                  */
  708                 bdwrite(bp);
  709                 if (seqcount > 1)
  710                         cluster_wbuild_wb(vp, lblocksize, vp->v_cstart, vp->v_clen + 1);
  711                 vp->v_clen = 0;
  712                 vp->v_cstart = lbn + 1;
  713         } else if (vm_page_count_severe()) {
  714                 /*
  715                  * We are low on memory, get it going NOW
  716                  */
  717                 bawrite(bp);
  718         } else {
  719                 /*
  720                  * In the middle of a cluster, so just delay the I/O for now.
  721                  */
  722                 bdwrite(bp);
  723         }
  724         vp->v_lastw = lbn;
  725         vp->v_lasta = bp->b_blkno;
  726 }
  727 
  728 
  729 /*
  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).
  734  */
  735 int
  736 cluster_wbuild(vp, size, start_lbn, len)
  737         struct vnode *vp;
  738         long size;
  739         daddr_t start_lbn;
  740         int len;
  741 {
  742         struct buf *bp, *tbp;
  743         int i, j;
  744         int totalwritten = 0;
  745         int dbsize = btodb(size);
  746 
  747         while (len > 0) {
  748                 /*
  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.
  752                  */
  753                 VI_LOCK(vp);
  754                 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
  755                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  756                         VI_UNLOCK(vp);
  757                         ++start_lbn;
  758                         --len;
  759                         continue;
  760                 }
  761                 if (BUF_LOCK(tbp,
  762                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, VI_MTX(vp))) {
  763                         ++start_lbn;
  764                         --len;
  765                         continue;
  766                 }
  767                 if ((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) {
  768                         BUF_UNLOCK(tbp);
  769                         ++start_lbn;
  770                         --len;
  771                         continue;
  772                 }
  773                 bremfree(tbp);
  774                 tbp->b_flags &= ~B_DONE;
  775 
  776                 /*
  777                  * Extra memory in the buffer, punt on this buffer.
  778                  * XXX we could handle this in most cases, but we would
  779                  * have to push the extra memory down to after our max
  780                  * possible cluster size and then potentially pull it back
  781                  * up if the cluster was terminated prematurely--too much
  782                  * hassle.
  783                  */
  784                 if (((tbp->b_flags & (B_CLUSTEROK | B_MALLOC | B_VMIO)) != 
  785                      (B_CLUSTEROK | B_VMIO)) ||
  786                   (tbp->b_bcount != tbp->b_bufsize) ||
  787                   (tbp->b_bcount != size) ||
  788                   (len == 1) ||
  789                   ((bp = getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
  790                         totalwritten += tbp->b_bufsize;
  791                         bawrite(tbp);
  792                         ++start_lbn;
  793                         --len;
  794                         continue;
  795                 }
  796 
  797                 /*
  798                  * We got a pbuf to make the cluster in.
  799                  * so initialise it.
  800                  */
  801                 TAILQ_INIT(&bp->b_cluster.cluster_head);
  802                 bp->b_bcount = 0;
  803                 bp->b_bufsize = 0;
  804                 bp->b_npages = 0;
  805                 if (tbp->b_wcred != NOCRED)
  806                         bp->b_wcred = crhold(tbp->b_wcred);
  807 
  808                 bp->b_blkno = tbp->b_blkno;
  809                 bp->b_lblkno = tbp->b_lblkno;
  810                 bp->b_offset = tbp->b_offset;
  811 
  812                 /*
  813                  * We are synthesizing a buffer out of vm_page_t's, but
  814                  * if the block size is not page aligned then the starting
  815                  * address may not be either.  Inherit the b_data offset
  816                  * from the original buffer.
  817                  */
  818                 bp->b_data = (char *)((vm_offset_t)bp->b_data |
  819                     ((vm_offset_t)tbp->b_data & PAGE_MASK));
  820                 bp->b_flags |= B_CLUSTER |
  821                                 (tbp->b_flags & (B_VMIO | B_NEEDCOMMIT));
  822                 bp->b_iodone = cluster_callback;
  823                 pbgetvp(vp, bp);
  824                 /*
  825                  * From this location in the file, scan forward to see
  826                  * if there are buffers with adjacent data that need to
  827                  * be written as well.
  828                  */
  829                 for (i = 0; i < len; ++i, ++start_lbn) {
  830                         if (i != 0) { /* If not the first buffer */
  831                                 /*
  832                                  * If the adjacent data is not even in core it
  833                                  * can't need to be written.
  834                                  */
  835                                 VI_LOCK(vp);
  836                                 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
  837                                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  838                                         VI_UNLOCK(vp);
  839                                         break;
  840                                 }
  841 
  842                                 /*
  843                                  * If it IS in core, but has different
  844                                  * characteristics, or is locked (which
  845                                  * means it could be undergoing a background
  846                                  * I/O or be in a weird state), then don't
  847                                  * cluster with it.
  848                                  */
  849                                 if (BUF_LOCK(tbp,
  850                                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
  851                                     VI_MTX(vp)))
  852                                         break;
  853 
  854                                 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
  855                                     B_INVAL | B_DELWRI | B_NEEDCOMMIT))
  856                                     != (B_DELWRI | B_CLUSTEROK |
  857                                     (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
  858                                     tbp->b_wcred != bp->b_wcred) {
  859                                         BUF_UNLOCK(tbp);
  860                                         break;
  861                                 }
  862 
  863                                 /*
  864                                  * Check that the combined cluster
  865                                  * would make sense with regard to pages
  866                                  * and would not be too large
  867                                  */
  868                                 if ((tbp->b_bcount != size) ||
  869                                   ((bp->b_blkno + (dbsize * i)) !=
  870                                     tbp->b_blkno) ||
  871                                   ((tbp->b_npages + bp->b_npages) >
  872                                     (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
  873                                         BUF_UNLOCK(tbp);
  874                                         break;
  875                                 }
  876                                 /*
  877                                  * Ok, it's passed all the tests,
  878                                  * so remove it from the free list
  879                                  * and mark it busy. We will use it.
  880                                  */
  881                                 bremfree(tbp);
  882                                 tbp->b_flags &= ~B_DONE;
  883                         } /* end of code for non-first buffers only */
  884                         /* check for latent dependencies to be handled */
  885                         if ((LIST_FIRST(&tbp->b_dep)) != NULL) {
  886                                 tbp->b_iocmd = BIO_WRITE;
  887                                 buf_start(tbp);
  888                         }
  889                         /*
  890                          * If the IO is via the VM then we do some
  891                          * special VM hackery (yuck).  Since the buffer's
  892                          * block size may not be page-aligned it is possible
  893                          * for a page to be shared between two buffers.  We
  894                          * have to get rid of the duplication when building
  895                          * the cluster.
  896                          */
  897                         if (tbp->b_flags & B_VMIO) {
  898                                 vm_page_t m;
  899 
  900                                 VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
  901                                 if (i != 0) { /* if not first buffer */
  902                                         for (j = 0; j < tbp->b_npages; j += 1) {
  903                                                 m = tbp->b_pages[j];
  904                                                 if (m->flags & PG_BUSY) {
  905                                                         VM_OBJECT_UNLOCK(
  906                                                             tbp->b_object);
  907                                                         bqrelse(tbp);
  908                                                         goto finishcluster;
  909                                                 }
  910                                         }
  911                                 }
  912                                 for (j = 0; j < tbp->b_npages; j += 1) {
  913                                         m = tbp->b_pages[j];
  914                                         vm_page_io_start(m);
  915                                         vm_object_pip_add(m->object, 1);
  916                                         if ((bp->b_npages == 0) ||
  917                                           (bp->b_pages[bp->b_npages - 1] != m)) {
  918                                                 bp->b_pages[bp->b_npages] = m;
  919                                                 bp->b_npages++;
  920                                         }
  921                                 }
  922                                 VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
  923                         }
  924                         bp->b_bcount += size;
  925                         bp->b_bufsize += size;
  926                         bundirty(tbp);
  927                         tbp->b_flags &= ~B_DONE;
  928                         tbp->b_ioflags &= ~BIO_ERROR;
  929                         tbp->b_flags |= B_ASYNC;
  930                         tbp->b_iocmd = BIO_WRITE;
  931                         reassignbuf(tbp);               /* put on clean list */
  932                         bufobj_wref(tbp->b_bufobj);
  933                         BUF_KERNPROC(tbp);
  934                         TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
  935                                 tbp, b_cluster.cluster_entry);
  936                 }
  937         finishcluster:
  938                 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
  939                         (vm_page_t *) bp->b_pages, bp->b_npages);
  940                 if (bp->b_bufsize > bp->b_kvasize)
  941                         panic(
  942                             "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
  943                             bp->b_bufsize, bp->b_kvasize);
  944                 bp->b_kvasize = bp->b_bufsize;
  945                 totalwritten += bp->b_bufsize;
  946                 bp->b_dirtyoff = 0;
  947                 bp->b_dirtyend = bp->b_bufsize;
  948                 bawrite(bp);
  949 
  950                 len -= i;
  951         }
  952         return totalwritten;
  953 }
  954 
  955 /*
  956  * Collect together all the buffers in a cluster.
  957  * Plus add one additional buffer.
  958  */
  959 static struct cluster_save *
  960 cluster_collectbufs(vp, last_bp)
  961         struct vnode *vp;
  962         struct buf *last_bp;
  963 {
  964         struct cluster_save *buflist;
  965         struct buf *bp;
  966         daddr_t lbn;
  967         int i, len;
  968 
  969         len = vp->v_lastw - vp->v_cstart + 1;
  970         buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
  971             M_SEGMENT, M_WAITOK);
  972         buflist->bs_nchildren = 0;
  973         buflist->bs_children = (struct buf **) (buflist + 1);
  974         for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
  975                 (void) bread(vp, lbn, last_bp->b_bcount, NOCRED, &bp);
  976                 buflist->bs_children[i] = bp;
  977                 if (bp->b_blkno == bp->b_lblkno)
  978                         VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno,
  979                                 NULL, NULL);
  980         }
  981         buflist->bs_children[i] = bp = last_bp;
  982         if (bp->b_blkno == bp->b_lblkno)
  983                 VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL);
  984         buflist->bs_nchildren = i + 1;
  985         return (buflist);
  986 }

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