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: stable/9/sys/kern/vfs_cluster.c 255168 2013-09-03 05:20:42Z kib $");
   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 *cluster_collectbufs(struct vnode *vp,
   64             struct buf *last_bp, int gbflags);
   65 static struct buf *cluster_rbuild(struct vnode *vp, u_quad_t filesize,
   66             daddr_t lbn, daddr_t blkno, long size, int run, int gbflags,
   67             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 = 64;
   75 SYSCTL_INT(_vfs, OID_AUTO, read_max, CTLFLAG_RW, &read_max, 0,
   76     "Cluster read-ahead max block count");
   77 
   78 static int read_min = 1;
   79 SYSCTL_INT(_vfs, OID_AUTO, read_min, CTLFLAG_RW, &read_min, 0,
   80     "Cluster read min block count");
   81 
   82 /* Page expended to mark partially backed buffers */
   83 extern vm_page_t        bogus_page;
   84 
   85 /*
   86  * Read data to a buf, including read-ahead if we find this to be beneficial.
   87  * cluster_read replaces bread.
   88  */
   89 int
   90 cluster_read(struct vnode *vp, u_quad_t filesize, daddr_t lblkno, long size,
   91     struct ucred *cred, long totread, int seqcount, struct buf **bpp)
   92 {
   93 
   94         return (cluster_read_gb(vp, filesize, lblkno, size, cred, totread,
   95             seqcount, 0, bpp));
   96 }
   97 
   98 int
   99 cluster_read_gb(struct vnode *vp, u_quad_t filesize, daddr_t lblkno, long size,
  100     struct ucred *cred, long totread, int seqcount, int gbflags,
  101     struct buf **bpp)
  102 {
  103         struct buf *bp, *rbp, *reqbp;
  104         struct bufobj *bo;
  105         daddr_t blkno, origblkno;
  106         int maxra, racluster;
  107         int error, ncontig;
  108         int i;
  109 
  110         error = 0;
  111         bo = &vp->v_bufobj;
  112         if (!unmapped_buf_allowed)
  113                 gbflags &= ~GB_UNMAPPED;
  114 
  115         /*
  116          * Try to limit the amount of read-ahead by a few
  117          * ad-hoc parameters.  This needs work!!!
  118          */
  119         racluster = vp->v_mount->mnt_iosize_max / size;
  120         maxra = seqcount;
  121         maxra = min(read_max, maxra);
  122         maxra = min(nbuf/8, maxra);
  123         if (((u_quad_t)(lblkno + maxra + 1) * size) > filesize)
  124                 maxra = (filesize / size) - lblkno;
  125 
  126         /*
  127          * get the requested block
  128          */
  129         *bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0, gbflags);
  130         origblkno = lblkno;
  131 
  132         /*
  133          * if it is in the cache, then check to see if the reads have been
  134          * sequential.  If they have, then try some read-ahead, otherwise
  135          * back-off on prospective read-aheads.
  136          */
  137         if (bp->b_flags & B_CACHE) {
  138                 if (!seqcount) {
  139                         return 0;
  140                 } else if ((bp->b_flags & B_RAM) == 0) {
  141                         return 0;
  142                 } else {
  143                         bp->b_flags &= ~B_RAM;
  144                         BO_LOCK(bo);
  145                         for (i = 1; i < maxra; i++) {
  146                                 /*
  147                                  * Stop if the buffer does not exist or it
  148                                  * is invalid (about to go away?)
  149                                  */
  150                                 rbp = gbincore(&vp->v_bufobj, lblkno+i);
  151                                 if (rbp == NULL || (rbp->b_flags & B_INVAL))
  152                                         break;
  153 
  154                                 /*
  155                                  * Set another read-ahead mark so we know 
  156                                  * to check again. (If we can lock the
  157                                  * buffer without waiting)
  158                                  */
  159                                 if ((((i % racluster) == (racluster - 1)) ||
  160                                     (i == (maxra - 1))) 
  161                                     && (0 == BUF_LOCK(rbp, 
  162                                         LK_EXCLUSIVE | LK_NOWAIT, NULL))) {
  163                                         rbp->b_flags |= B_RAM;
  164                                         BUF_UNLOCK(rbp);
  165                                 }                       
  166                         }
  167                         BO_UNLOCK(bo);
  168                         if (i >= maxra) {
  169                                 return 0;
  170                         }
  171                         lblkno += i;
  172                 }
  173                 reqbp = bp = NULL;
  174         /*
  175          * If it isn't in the cache, then get a chunk from
  176          * disk if sequential, otherwise just get the block.
  177          */
  178         } else {
  179                 off_t firstread = bp->b_offset;
  180                 int nblks;
  181                 long minread;
  182 
  183                 KASSERT(bp->b_offset != NOOFFSET,
  184                     ("cluster_read: no buffer offset"));
  185 
  186                 ncontig = 0;
  187 
  188                 /*
  189                  * Adjust totread if needed
  190                  */
  191                 minread = read_min * size;
  192                 if (minread > totread)
  193                         totread = minread;
  194 
  195                 /*
  196                  * Compute the total number of blocks that we should read
  197                  * synchronously.
  198                  */
  199                 if (firstread + totread > filesize)
  200                         totread = filesize - firstread;
  201                 nblks = howmany(totread, size);
  202                 if (nblks > racluster)
  203                         nblks = racluster;
  204 
  205                 /*
  206                  * Now compute the number of contiguous blocks.
  207                  */
  208                 if (nblks > 1) {
  209                         error = VOP_BMAP(vp, lblkno, NULL,
  210                                 &blkno, &ncontig, NULL);
  211                         /*
  212                          * If this failed to map just do the original block.
  213                          */
  214                         if (error || blkno == -1)
  215                                 ncontig = 0;
  216                 }
  217 
  218                 /*
  219                  * If we have contiguous data available do a cluster
  220                  * otherwise just read the requested block.
  221                  */
  222                 if (ncontig) {
  223                         /* Account for our first block. */
  224                         ncontig = min(ncontig + 1, nblks);
  225                         if (ncontig < nblks)
  226                                 nblks = ncontig;
  227                         bp = cluster_rbuild(vp, filesize, lblkno,
  228                             blkno, size, nblks, gbflags, bp);
  229                         lblkno += (bp->b_bufsize / size);
  230                 } else {
  231                         bp->b_flags |= B_RAM;
  232                         bp->b_iocmd = BIO_READ;
  233                         lblkno += 1;
  234                 }
  235         }
  236 
  237         /*
  238          * handle the synchronous read so that it is available ASAP.
  239          */
  240         if (bp) {
  241                 if ((bp->b_flags & B_CLUSTER) == 0) {
  242                         vfs_busy_pages(bp, 0);
  243                 }
  244                 bp->b_flags &= ~B_INVAL;
  245                 bp->b_ioflags &= ~BIO_ERROR;
  246                 if ((bp->b_flags & B_ASYNC) || bp->b_iodone != NULL)
  247                         BUF_KERNPROC(bp);
  248                 bp->b_iooffset = dbtob(bp->b_blkno);
  249                 bstrategy(bp);
  250                 curthread->td_ru.ru_inblock++;
  251         }
  252 
  253         /*
  254          * If we have been doing sequential I/O, then do some read-ahead.
  255          */
  256         while (lblkno < (origblkno + maxra)) {
  257                 error = VOP_BMAP(vp, lblkno, NULL, &blkno, &ncontig, NULL);
  258                 if (error)
  259                         break;
  260 
  261                 if (blkno == -1)
  262                         break;
  263 
  264                 /*
  265                  * We could throttle ncontig here by maxra but we might as
  266                  * well read the data if it is contiguous.  We're throttled
  267                  * by racluster anyway.
  268                  */
  269                 if (ncontig) {
  270                         ncontig = min(ncontig + 1, racluster);
  271                         rbp = cluster_rbuild(vp, filesize, lblkno, blkno,
  272                             size, ncontig, gbflags, NULL);
  273                         lblkno += (rbp->b_bufsize / size);
  274                         if (rbp->b_flags & B_DELWRI) {
  275                                 bqrelse(rbp);
  276                                 continue;
  277                         }
  278                 } else {
  279                         rbp = getblk(vp, lblkno, size, 0, 0, gbflags);
  280                         lblkno += 1;
  281                         if (rbp->b_flags & B_DELWRI) {
  282                                 bqrelse(rbp);
  283                                 continue;
  284                         }
  285                         rbp->b_flags |= B_ASYNC | B_RAM;
  286                         rbp->b_iocmd = BIO_READ;
  287                         rbp->b_blkno = blkno;
  288                 }
  289                 if (rbp->b_flags & B_CACHE) {
  290                         rbp->b_flags &= ~B_ASYNC;
  291                         bqrelse(rbp);
  292                         continue;
  293                 }
  294                 if ((rbp->b_flags & B_CLUSTER) == 0) {
  295                         vfs_busy_pages(rbp, 0);
  296                 }
  297                 rbp->b_flags &= ~B_INVAL;
  298                 rbp->b_ioflags &= ~BIO_ERROR;
  299                 if ((rbp->b_flags & B_ASYNC) || rbp->b_iodone != NULL)
  300                         BUF_KERNPROC(rbp);
  301                 rbp->b_iooffset = dbtob(rbp->b_blkno);
  302                 bstrategy(rbp);
  303                 curthread->td_ru.ru_inblock++;
  304         }
  305 
  306         if (reqbp)
  307                 return (bufwait(reqbp));
  308         else
  309                 return (error);
  310 }
  311 
  312 /*
  313  * If blocks are contiguous on disk, use this to provide clustered
  314  * read ahead.  We will read as many blocks as possible sequentially
  315  * and then parcel them up into logical blocks in the buffer hash table.
  316  */
  317 static struct buf *
  318 cluster_rbuild(struct vnode *vp, u_quad_t filesize, daddr_t lbn,
  319     daddr_t blkno, long size, int run, int gbflags, struct buf *fbp)
  320 {
  321         struct bufobj *bo;
  322         struct buf *bp, *tbp;
  323         daddr_t bn;
  324         off_t off;
  325         long tinc, tsize;
  326         int i, inc, j, toff;
  327 
  328         KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
  329             ("cluster_rbuild: size %ld != filesize %jd\n",
  330             size, (intmax_t)vp->v_mount->mnt_stat.f_iosize));
  331 
  332         /*
  333          * avoid a division
  334          */
  335         while ((u_quad_t) size * (lbn + run) > filesize) {
  336                 --run;
  337         }
  338 
  339         if (fbp) {
  340                 tbp = fbp;
  341                 tbp->b_iocmd = BIO_READ; 
  342         } else {
  343                 tbp = getblk(vp, lbn, size, 0, 0, gbflags);
  344                 if (tbp->b_flags & B_CACHE)
  345                         return tbp;
  346                 tbp->b_flags |= B_ASYNC | B_RAM;
  347                 tbp->b_iocmd = BIO_READ;
  348         }
  349         tbp->b_blkno = blkno;
  350         if( (tbp->b_flags & B_MALLOC) ||
  351                 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
  352                 return tbp;
  353 
  354         bp = trypbuf(&cluster_pbuf_freecnt);
  355         if (bp == 0)
  356                 return tbp;
  357 
  358         /*
  359          * We are synthesizing a buffer out of vm_page_t's, but
  360          * if the block size is not page aligned then the starting
  361          * address may not be either.  Inherit the b_data offset
  362          * from the original buffer.
  363          */
  364         bp->b_flags = B_ASYNC | B_CLUSTER | B_VMIO;
  365         if ((gbflags & GB_UNMAPPED) != 0) {
  366                 bp->b_flags |= B_UNMAPPED;
  367                 bp->b_data = unmapped_buf;
  368         } else {
  369                 bp->b_data = (char *)((vm_offset_t)bp->b_data |
  370                     ((vm_offset_t)tbp->b_data & PAGE_MASK));
  371         }
  372         bp->b_iocmd = BIO_READ;
  373         bp->b_iodone = cluster_callback;
  374         bp->b_blkno = blkno;
  375         bp->b_lblkno = lbn;
  376         bp->b_offset = tbp->b_offset;
  377         KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
  378         pbgetvp(vp, bp);
  379 
  380         TAILQ_INIT(&bp->b_cluster.cluster_head);
  381 
  382         bp->b_bcount = 0;
  383         bp->b_bufsize = 0;
  384         bp->b_npages = 0;
  385 
  386         inc = btodb(size);
  387         bo = &vp->v_bufobj;
  388         for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
  389                 if (i != 0) {
  390                         if ((bp->b_npages * PAGE_SIZE) +
  391                             round_page(size) > vp->v_mount->mnt_iosize_max) {
  392                                 break;
  393                         }
  394 
  395                         tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT |
  396                             (gbflags & GB_UNMAPPED));
  397 
  398                         /* Don't wait around for locked bufs. */
  399                         if (tbp == NULL)
  400                                 break;
  401 
  402                         /*
  403                          * Stop scanning if the buffer is fully valid
  404                          * (marked B_CACHE), or locked (may be doing a
  405                          * background write), or if the buffer is not
  406                          * VMIO backed.  The clustering code can only deal
  407                          * with VMIO-backed buffers.
  408                          */
  409                         BO_LOCK(bo);
  410                         if ((tbp->b_vflags & BV_BKGRDINPROG) ||
  411                             (tbp->b_flags & B_CACHE) ||
  412                             (tbp->b_flags & B_VMIO) == 0) {
  413                                 BO_UNLOCK(bo);
  414                                 bqrelse(tbp);
  415                                 break;
  416                         }
  417                         BO_UNLOCK(bo);
  418 
  419                         /*
  420                          * The buffer must be completely invalid in order to
  421                          * take part in the cluster.  If it is partially valid
  422                          * then we stop.
  423                          */
  424                         off = tbp->b_offset;
  425                         tsize = size;
  426                         VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
  427                         for (j = 0; tsize > 0; j++) {
  428                                 toff = off & PAGE_MASK;
  429                                 tinc = tsize;
  430                                 if (toff + tinc > PAGE_SIZE)
  431                                         tinc = PAGE_SIZE - toff;
  432                                 VM_OBJECT_LOCK_ASSERT(tbp->b_pages[j]->object,
  433                                     MA_OWNED);
  434                                 if ((tbp->b_pages[j]->valid &
  435                                     vm_page_bits(toff, tinc)) != 0)
  436                                         break;
  437                                 off += tinc;
  438                                 tsize -= tinc;
  439                         }
  440                         VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
  441                         if (tsize > 0) {
  442                                 bqrelse(tbp);
  443                                 break;
  444                         }
  445 
  446                         /*
  447                          * Set a read-ahead mark as appropriate
  448                          */
  449                         if ((fbp && (i == 1)) || (i == (run - 1)))
  450                                 tbp->b_flags |= B_RAM;
  451 
  452                         /*
  453                          * Set the buffer up for an async read (XXX should
  454                          * we do this only if we do not wind up brelse()ing?).
  455                          * Set the block number if it isn't set, otherwise
  456                          * if it is make sure it matches the block number we
  457                          * expect.
  458                          */
  459                         tbp->b_flags |= B_ASYNC;
  460                         tbp->b_iocmd = BIO_READ;
  461                         if (tbp->b_blkno == tbp->b_lblkno) {
  462                                 tbp->b_blkno = bn;
  463                         } else if (tbp->b_blkno != bn) {
  464                                 brelse(tbp);
  465                                 break;
  466                         }
  467                 }
  468                 /*
  469                  * XXX fbp from caller may not be B_ASYNC, but we are going
  470                  * to biodone() it in cluster_callback() anyway
  471                  */
  472                 BUF_KERNPROC(tbp);
  473                 TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
  474                         tbp, b_cluster.cluster_entry);
  475                 VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
  476                 for (j = 0; j < tbp->b_npages; j += 1) {
  477                         vm_page_t m;
  478                         m = tbp->b_pages[j];
  479                         vm_page_io_start(m);
  480                         vm_object_pip_add(m->object, 1);
  481                         if ((bp->b_npages == 0) ||
  482                                 (bp->b_pages[bp->b_npages-1] != m)) {
  483                                 bp->b_pages[bp->b_npages] = m;
  484                                 bp->b_npages++;
  485                         }
  486                         if (m->valid == VM_PAGE_BITS_ALL)
  487                                 tbp->b_pages[j] = bogus_page;
  488                 }
  489                 VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
  490                 /*
  491                  * Don't inherit tbp->b_bufsize as it may be larger due to
  492                  * a non-page-aligned size.  Instead just aggregate using
  493                  * 'size'.
  494                  */
  495                 if (tbp->b_bcount != size)
  496                         printf("warning: tbp->b_bcount wrong %ld vs %ld\n", tbp->b_bcount, size);
  497                 if (tbp->b_bufsize != size)
  498                         printf("warning: tbp->b_bufsize wrong %ld vs %ld\n", tbp->b_bufsize, size);
  499                 bp->b_bcount += size;
  500                 bp->b_bufsize += size;
  501         }
  502 
  503         /*
  504          * Fully valid pages in the cluster are already good and do not need
  505          * to be re-read from disk.  Replace the page with bogus_page
  506          */
  507         VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
  508         for (j = 0; j < bp->b_npages; j++) {
  509                 VM_OBJECT_LOCK_ASSERT(bp->b_pages[j]->object, MA_OWNED);
  510                 if (bp->b_pages[j]->valid == VM_PAGE_BITS_ALL)
  511                         bp->b_pages[j] = bogus_page;
  512         }
  513         VM_OBJECT_UNLOCK(bp->b_bufobj->bo_object);
  514         if (bp->b_bufsize > bp->b_kvasize)
  515                 panic("cluster_rbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
  516                     bp->b_bufsize, bp->b_kvasize);
  517         bp->b_kvasize = bp->b_bufsize;
  518 
  519         if ((bp->b_flags & B_UNMAPPED) == 0) {
  520                 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
  521                     (vm_page_t *)bp->b_pages, bp->b_npages);
  522         }
  523         return (bp);
  524 }
  525 
  526 /*
  527  * Cleanup after a clustered read or write.
  528  * This is complicated by the fact that any of the buffers might have
  529  * extra memory (if there were no empty buffer headers at allocbuf time)
  530  * that we will need to shift around.
  531  */
  532 static void
  533 cluster_callback(bp)
  534         struct buf *bp;
  535 {
  536         struct buf *nbp, *tbp;
  537         int error = 0;
  538 
  539         /*
  540          * Must propogate errors to all the components.
  541          */
  542         if (bp->b_ioflags & BIO_ERROR)
  543                 error = bp->b_error;
  544 
  545         if ((bp->b_flags & B_UNMAPPED) == 0) {
  546                 pmap_qremove(trunc_page((vm_offset_t) bp->b_data),
  547                     bp->b_npages);
  548         }
  549         /*
  550          * Move memory from the large cluster buffer into the component
  551          * buffers and mark IO as done on these.
  552          */
  553         for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
  554                 tbp; tbp = nbp) {
  555                 nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
  556                 if (error) {
  557                         tbp->b_ioflags |= BIO_ERROR;
  558                         tbp->b_error = error;
  559                 } else {
  560                         tbp->b_dirtyoff = tbp->b_dirtyend = 0;
  561                         tbp->b_flags &= ~B_INVAL;
  562                         tbp->b_ioflags &= ~BIO_ERROR;
  563                         /*
  564                          * XXX the bdwrite()/bqrelse() issued during
  565                          * cluster building clears B_RELBUF (see bqrelse()
  566                          * comment).  If direct I/O was specified, we have
  567                          * to restore it here to allow the buffer and VM
  568                          * to be freed.
  569                          */
  570                         if (tbp->b_flags & B_DIRECT)
  571                                 tbp->b_flags |= B_RELBUF;
  572                 }
  573                 bufdone(tbp);
  574         }
  575         pbrelvp(bp);
  576         relpbuf(bp, &cluster_pbuf_freecnt);
  577 }
  578 
  579 /*
  580  *      cluster_wbuild_wb:
  581  *
  582  *      Implement modified write build for cluster.
  583  *
  584  *              write_behind = 0        write behind disabled
  585  *              write_behind = 1        write behind normal (default)
  586  *              write_behind = 2        write behind backed-off
  587  */
  588 
  589 static __inline int
  590 cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len,
  591     int gbflags)
  592 {
  593         int r = 0;
  594 
  595         switch (write_behind) {
  596         case 2:
  597                 if (start_lbn < len)
  598                         break;
  599                 start_lbn -= len;
  600                 /* FALLTHROUGH */
  601         case 1:
  602                 r = cluster_wbuild_gb(vp, size, start_lbn, len, gbflags);
  603                 /* FALLTHROUGH */
  604         default:
  605                 /* FALLTHROUGH */
  606                 break;
  607         }
  608         return(r);
  609 }
  610 
  611 /*
  612  * Do clustered write for FFS.
  613  *
  614  * Three cases:
  615  *      1. Write is not sequential (write asynchronously)
  616  *      Write is sequential:
  617  *      2.      beginning of cluster - begin cluster
  618  *      3.      middle of a cluster - add to cluster
  619  *      4.      end of a cluster - asynchronously write cluster
  620  */
  621 void
  622 cluster_write(struct vnode *vp, struct buf *bp, u_quad_t filesize, int seqcount)
  623 {
  624 
  625         cluster_write_gb(vp, bp, filesize, seqcount, 0);
  626 }
  627 
  628 void
  629 cluster_write_gb(struct vnode *vp, struct buf *bp, u_quad_t filesize,
  630     int seqcount, int gbflags)
  631 {
  632         daddr_t lbn;
  633         int maxclen, cursize;
  634         int lblocksize;
  635         int async;
  636 
  637         if (!unmapped_buf_allowed)
  638                 gbflags &= ~GB_UNMAPPED;
  639 
  640         if (vp->v_type == VREG) {
  641                 async = DOINGASYNC(vp);
  642                 lblocksize = vp->v_mount->mnt_stat.f_iosize;
  643         } else {
  644                 async = 0;
  645                 lblocksize = bp->b_bufsize;
  646         }
  647         lbn = bp->b_lblkno;
  648         KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));
  649 
  650         /* Initialize vnode to beginning of file. */
  651         if (lbn == 0)
  652                 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
  653 
  654         if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
  655             (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
  656                 maxclen = vp->v_mount->mnt_iosize_max / lblocksize - 1;
  657                 if (vp->v_clen != 0) {
  658                         /*
  659                          * Next block is not sequential.
  660                          *
  661                          * If we are not writing at end of file, the process
  662                          * seeked to another point in the file since its last
  663                          * write, or we have reached our maximum cluster size,
  664                          * then push the previous cluster. Otherwise try
  665                          * reallocating to make it sequential.
  666                          *
  667                          * Change to algorithm: only push previous cluster if
  668                          * it was sequential from the point of view of the
  669                          * seqcount heuristic, otherwise leave the buffer 
  670                          * intact so we can potentially optimize the I/O
  671                          * later on in the buf_daemon or update daemon
  672                          * flush.
  673                          */
  674                         cursize = vp->v_lastw - vp->v_cstart + 1;
  675                         if (((u_quad_t) bp->b_offset + lblocksize) != filesize ||
  676                             lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
  677                                 if (!async && seqcount > 0) {
  678                                         cluster_wbuild_wb(vp, lblocksize,
  679                                             vp->v_cstart, cursize, gbflags);
  680                                 }
  681                         } else {
  682                                 struct buf **bpp, **endbp;
  683                                 struct cluster_save *buflist;
  684 
  685                                 buflist = cluster_collectbufs(vp, bp, gbflags);
  686                                 endbp = &buflist->bs_children
  687                                     [buflist->bs_nchildren - 1];
  688                                 if (VOP_REALLOCBLKS(vp, buflist)) {
  689                                         /*
  690                                          * Failed, push the previous cluster
  691                                          * if *really* writing sequentially
  692                                          * in the logical file (seqcount > 1),
  693                                          * otherwise delay it in the hopes that
  694                                          * the low level disk driver can
  695                                          * optimize the write ordering.
  696                                          */
  697                                         for (bpp = buflist->bs_children;
  698                                              bpp < endbp; bpp++)
  699                                                 brelse(*bpp);
  700                                         free(buflist, M_SEGMENT);
  701                                         if (seqcount > 1) {
  702                                                 cluster_wbuild_wb(vp, 
  703                                                     lblocksize, vp->v_cstart, 
  704                                                     cursize, gbflags);
  705                                         }
  706                                 } else {
  707                                         /*
  708                                          * Succeeded, keep building cluster.
  709                                          */
  710                                         for (bpp = buflist->bs_children;
  711                                              bpp <= endbp; bpp++)
  712                                                 bdwrite(*bpp);
  713                                         free(buflist, M_SEGMENT);
  714                                         vp->v_lastw = lbn;
  715                                         vp->v_lasta = bp->b_blkno;
  716                                         return;
  717                                 }
  718                         }
  719                 }
  720                 /*
  721                  * Consider beginning a cluster. If at end of file, make
  722                  * cluster as large as possible, otherwise find size of
  723                  * existing cluster.
  724                  */
  725                 if ((vp->v_type == VREG) &&
  726                         ((u_quad_t) bp->b_offset + lblocksize) != filesize &&
  727                     (bp->b_blkno == bp->b_lblkno) &&
  728                     (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
  729                      bp->b_blkno == -1)) {
  730                         bawrite(bp);
  731                         vp->v_clen = 0;
  732                         vp->v_lasta = bp->b_blkno;
  733                         vp->v_cstart = lbn + 1;
  734                         vp->v_lastw = lbn;
  735                         return;
  736                 }
  737                 vp->v_clen = maxclen;
  738                 if (!async && maxclen == 0) {   /* I/O not contiguous */
  739                         vp->v_cstart = lbn + 1;
  740                         bawrite(bp);
  741                 } else {        /* Wait for rest of cluster */
  742                         vp->v_cstart = lbn;
  743                         bdwrite(bp);
  744                 }
  745         } else if (lbn == vp->v_cstart + vp->v_clen) {
  746                 /*
  747                  * At end of cluster, write it out if seqcount tells us we
  748                  * are operating sequentially, otherwise let the buf or
  749                  * update daemon handle it.
  750                  */
  751                 bdwrite(bp);
  752                 if (seqcount > 1) {
  753                         cluster_wbuild_wb(vp, lblocksize, vp->v_cstart,
  754                             vp->v_clen + 1, gbflags);
  755                 }
  756                 vp->v_clen = 0;
  757                 vp->v_cstart = lbn + 1;
  758         } else if (vm_page_count_severe()) {
  759                 /*
  760                  * We are low on memory, get it going NOW
  761                  */
  762                 bawrite(bp);
  763         } else {
  764                 /*
  765                  * In the middle of a cluster, so just delay the I/O for now.
  766                  */
  767                 bdwrite(bp);
  768         }
  769         vp->v_lastw = lbn;
  770         vp->v_lasta = bp->b_blkno;
  771 }
  772 
  773 
  774 /*
  775  * This is an awful lot like cluster_rbuild...wish they could be combined.
  776  * The last lbn argument is the current block on which I/O is being
  777  * performed.  Check to see that it doesn't fall in the middle of
  778  * the current block (if last_bp == NULL).
  779  */
  780 int
  781 cluster_wbuild(struct vnode *vp, long size, daddr_t start_lbn, int len)
  782 {
  783 
  784         return (cluster_wbuild_gb(vp, size, start_lbn, len, 0));
  785 }
  786 
  787 int
  788 cluster_wbuild_gb(struct vnode *vp, long size, daddr_t start_lbn, int len,
  789     int gbflags)
  790 {
  791         struct buf *bp, *tbp;
  792         struct bufobj *bo;
  793         int i, j;
  794         int totalwritten = 0;
  795         int dbsize = btodb(size);
  796 
  797         if (!unmapped_buf_allowed)
  798                 gbflags &= ~GB_UNMAPPED;
  799 
  800         bo = &vp->v_bufobj;
  801         while (len > 0) {
  802                 /*
  803                  * If the buffer is not delayed-write (i.e. dirty), or it
  804                  * is delayed-write but either locked or inval, it cannot
  805                  * partake in the clustered write.
  806                  */
  807                 BO_LOCK(bo);
  808                 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
  809                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  810                         BO_UNLOCK(bo);
  811                         ++start_lbn;
  812                         --len;
  813                         continue;
  814                 }
  815                 if (BUF_LOCK(tbp,
  816                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, BO_MTX(bo))) {
  817                         ++start_lbn;
  818                         --len;
  819                         continue;
  820                 }
  821                 if ((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) {
  822                         BUF_UNLOCK(tbp);
  823                         ++start_lbn;
  824                         --len;
  825                         continue;
  826                 }
  827                 if (tbp->b_pin_count >  0) {
  828                         BUF_UNLOCK(tbp);
  829                         ++start_lbn;
  830                         --len;
  831                         continue;
  832                 }
  833                 bremfree(tbp);
  834                 tbp->b_flags &= ~B_DONE;
  835 
  836                 /*
  837                  * Extra memory in the buffer, punt on this buffer.
  838                  * XXX we could handle this in most cases, but we would
  839                  * have to push the extra memory down to after our max
  840                  * possible cluster size and then potentially pull it back
  841                  * up if the cluster was terminated prematurely--too much
  842                  * hassle.
  843                  */
  844                 if (((tbp->b_flags & (B_CLUSTEROK | B_MALLOC | B_VMIO)) != 
  845                      (B_CLUSTEROK | B_VMIO)) ||
  846                   (tbp->b_bcount != tbp->b_bufsize) ||
  847                   (tbp->b_bcount != size) ||
  848                   (len == 1) ||
  849                   ((bp = (vp->v_vflag & VV_MD) != 0 ?
  850                   trypbuf(&cluster_pbuf_freecnt) :
  851                   getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
  852                         totalwritten += tbp->b_bufsize;
  853                         bawrite(tbp);
  854                         ++start_lbn;
  855                         --len;
  856                         continue;
  857                 }
  858 
  859                 /*
  860                  * We got a pbuf to make the cluster in.
  861                  * so initialise it.
  862                  */
  863                 TAILQ_INIT(&bp->b_cluster.cluster_head);
  864                 bp->b_bcount = 0;
  865                 bp->b_bufsize = 0;
  866                 bp->b_npages = 0;
  867                 if (tbp->b_wcred != NOCRED)
  868                         bp->b_wcred = crhold(tbp->b_wcred);
  869 
  870                 bp->b_blkno = tbp->b_blkno;
  871                 bp->b_lblkno = tbp->b_lblkno;
  872                 bp->b_offset = tbp->b_offset;
  873 
  874                 /*
  875                  * We are synthesizing a buffer out of vm_page_t's, but
  876                  * if the block size is not page aligned then the starting
  877                  * address may not be either.  Inherit the b_data offset
  878                  * from the original buffer.
  879                  */
  880                 if ((gbflags & GB_UNMAPPED) == 0 ||
  881                     (tbp->b_flags & B_VMIO) == 0) {
  882                         bp->b_data = (char *)((vm_offset_t)bp->b_data |
  883                             ((vm_offset_t)tbp->b_data & PAGE_MASK));
  884                 } else {
  885                         bp->b_flags |= B_UNMAPPED;
  886                         bp->b_data = unmapped_buf;
  887                 }
  888                 bp->b_flags |= B_CLUSTER | (tbp->b_flags & (B_VMIO |
  889                     B_NEEDCOMMIT));
  890                 bp->b_iodone = cluster_callback;
  891                 pbgetvp(vp, bp);
  892                 /*
  893                  * From this location in the file, scan forward to see
  894                  * if there are buffers with adjacent data that need to
  895                  * be written as well.
  896                  */
  897                 for (i = 0; i < len; ++i, ++start_lbn) {
  898                         if (i != 0) { /* If not the first buffer */
  899                                 /*
  900                                  * If the adjacent data is not even in core it
  901                                  * can't need to be written.
  902                                  */
  903                                 BO_LOCK(bo);
  904                                 if ((tbp = gbincore(bo, start_lbn)) == NULL ||
  905                                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  906                                         BO_UNLOCK(bo);
  907                                         break;
  908                                 }
  909 
  910                                 /*
  911                                  * If it IS in core, but has different
  912                                  * characteristics, or is locked (which
  913                                  * means it could be undergoing a background
  914                                  * I/O or be in a weird state), then don't
  915                                  * cluster with it.
  916                                  */
  917                                 if (BUF_LOCK(tbp,
  918                                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
  919                                     BO_MTX(bo)))
  920                                         break;
  921 
  922                                 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
  923                                     B_INVAL | B_DELWRI | B_NEEDCOMMIT))
  924                                     != (B_DELWRI | B_CLUSTEROK |
  925                                     (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
  926                                     tbp->b_wcred != bp->b_wcred) {
  927                                         BUF_UNLOCK(tbp);
  928                                         break;
  929                                 }
  930 
  931                                 /*
  932                                  * Check that the combined cluster
  933                                  * would make sense with regard to pages
  934                                  * and would not be too large
  935                                  */
  936                                 if ((tbp->b_bcount != size) ||
  937                                   ((bp->b_blkno + (dbsize * i)) !=
  938                                     tbp->b_blkno) ||
  939                                   ((tbp->b_npages + bp->b_npages) >
  940                                     (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
  941                                         BUF_UNLOCK(tbp);
  942                                         break;
  943                                 }
  944 
  945                                 /*
  946                                  * Do not pull in pinned buffers.
  947                                  */
  948                                 if (tbp->b_pin_count > 0) {
  949                                         BUF_UNLOCK(tbp);
  950                                         break;
  951                                 }
  952 
  953                                 /*
  954                                  * Ok, it's passed all the tests,
  955                                  * so remove it from the free list
  956                                  * and mark it busy. We will use it.
  957                                  */
  958                                 bremfree(tbp);
  959                                 tbp->b_flags &= ~B_DONE;
  960                         } /* end of code for non-first buffers only */
  961                         /*
  962                          * If the IO is via the VM then we do some
  963                          * special VM hackery (yuck).  Since the buffer's
  964                          * block size may not be page-aligned it is possible
  965                          * for a page to be shared between two buffers.  We
  966                          * have to get rid of the duplication when building
  967                          * the cluster.
  968                          */
  969                         if (tbp->b_flags & B_VMIO) {
  970                                 vm_page_t m;
  971 
  972                                 VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
  973                                 if (i != 0) { /* if not first buffer */
  974                                         for (j = 0; j < tbp->b_npages; j += 1) {
  975                                                 m = tbp->b_pages[j];
  976                                                 if (m->oflags & VPO_BUSY) {
  977                                                         VM_OBJECT_UNLOCK(
  978                                                             tbp->b_object);
  979                                                         bqrelse(tbp);
  980                                                         goto finishcluster;
  981                                                 }
  982                                         }
  983                                 }
  984                                 for (j = 0; j < tbp->b_npages; j += 1) {
  985                                         m = tbp->b_pages[j];
  986                                         vm_page_io_start(m);
  987                                         vm_object_pip_add(m->object, 1);
  988                                         if ((bp->b_npages == 0) ||
  989                                           (bp->b_pages[bp->b_npages - 1] != m)) {
  990                                                 bp->b_pages[bp->b_npages] = m;
  991                                                 bp->b_npages++;
  992                                         }
  993                                 }
  994                                 VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
  995                         }
  996                         bp->b_bcount += size;
  997                         bp->b_bufsize += size;
  998                         /*
  999                          * If any of the clustered buffers have their
 1000                          * B_BARRIER flag set, transfer that request to
 1001                          * the cluster.
 1002                          */
 1003                         bp->b_flags |= (tbp->b_flags & B_BARRIER);
 1004                         tbp->b_flags &= ~(B_DONE | B_BARRIER);
 1005                         tbp->b_flags |= B_ASYNC;
 1006                         tbp->b_ioflags &= ~BIO_ERROR;
 1007                         tbp->b_iocmd = BIO_WRITE;
 1008                         bundirty(tbp);
 1009                         reassignbuf(tbp);               /* put on clean list */
 1010                         bufobj_wref(tbp->b_bufobj);
 1011                         BUF_KERNPROC(tbp);
 1012                         TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
 1013                                 tbp, b_cluster.cluster_entry);
 1014                 }
 1015         finishcluster:
 1016                 if ((bp->b_flags & B_UNMAPPED) == 0) {
 1017                         pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 1018                             (vm_page_t *)bp->b_pages, bp->b_npages);
 1019                 }
 1020                 if (bp->b_bufsize > bp->b_kvasize)
 1021                         panic(
 1022                             "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
 1023                             bp->b_bufsize, bp->b_kvasize);
 1024                 bp->b_kvasize = bp->b_bufsize;
 1025                 totalwritten += bp->b_bufsize;
 1026                 bp->b_dirtyoff = 0;
 1027                 bp->b_dirtyend = bp->b_bufsize;
 1028                 bawrite(bp);
 1029 
 1030                 len -= i;
 1031         }
 1032         return totalwritten;
 1033 }
 1034 
 1035 /*
 1036  * Collect together all the buffers in a cluster.
 1037  * Plus add one additional buffer.
 1038  */
 1039 static struct cluster_save *
 1040 cluster_collectbufs(struct vnode *vp, struct buf *last_bp, int gbflags)
 1041 {
 1042         struct cluster_save *buflist;
 1043         struct buf *bp;
 1044         daddr_t lbn;
 1045         int i, len;
 1046 
 1047         len = vp->v_lastw - vp->v_cstart + 1;
 1048         buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
 1049             M_SEGMENT, M_WAITOK);
 1050         buflist->bs_nchildren = 0;
 1051         buflist->bs_children = (struct buf **) (buflist + 1);
 1052         for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
 1053                 (void)bread_gb(vp, lbn, last_bp->b_bcount, NOCRED,
 1054                     gbflags, &bp);
 1055                 buflist->bs_children[i] = bp;
 1056                 if (bp->b_blkno == bp->b_lblkno)
 1057                         VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno,
 1058                                 NULL, NULL);
 1059         }
 1060         buflist->bs_children[i] = bp = last_bp;
 1061         if (bp->b_blkno == bp->b_lblkno)
 1062                 VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL);
 1063         buflist->bs_nchildren = i + 1;
 1064         return (buflist);
 1065 }

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