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/10/sys/kern/vfs_cluster.c 302234 2016-06-27 21:50:30Z bdrewery $");
   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/rwlock.h>
   50 #include <sys/vmmeter.h>
   51 #include <vm/vm.h>
   52 #include <vm/vm_object.h>
   53 #include <vm/vm_page.h>
   54 #include <sys/sysctl.h>
   55 
   56 #if defined(CLUSTERDEBUG)
   57 static int      rcluster= 0;
   58 SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0,
   59     "Debug VFS clustering code");
   60 #endif
   61 
   62 static MALLOC_DEFINE(M_SEGMENT, "cl_savebuf", "cluster_save buffer");
   63 
   64 static struct cluster_save *cluster_collectbufs(struct vnode *vp,
   65             struct buf *last_bp, int gbflags);
   66 static struct buf *cluster_rbuild(struct vnode *vp, u_quad_t filesize,
   67             daddr_t lbn, daddr_t blkno, long size, int run, int gbflags,
   68             struct buf *fbp);
   69 static void cluster_callback(struct buf *);
   70 
   71 static int write_behind = 1;
   72 SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0,
   73     "Cluster write-behind; 0: disable, 1: enable, 2: backed off");
   74 
   75 static int read_max = 64;
   76 SYSCTL_INT(_vfs, OID_AUTO, read_max, CTLFLAG_RW, &read_max, 0,
   77     "Cluster read-ahead max block count");
   78 
   79 static int read_min = 1;
   80 SYSCTL_INT(_vfs, OID_AUTO, read_min, CTLFLAG_RW, &read_min, 0,
   81     "Cluster read min block count");
   82 
   83 /* Page expended to mark partially backed buffers */
   84 extern vm_page_t        bogus_page;
   85 
   86 /*
   87  * Read data to a buf, including read-ahead if we find this to be beneficial.
   88  * cluster_read replaces bread.
   89  */
   90 int
   91 cluster_read(struct vnode *vp, u_quad_t filesize, daddr_t lblkno, long size,
   92     struct ucred *cred, long totread, int seqcount, int gbflags,
   93     struct buf **bpp)
   94 {
   95         struct buf *bp, *rbp, *reqbp;
   96         struct bufobj *bo;
   97         daddr_t blkno, origblkno;
   98         int maxra, racluster;
   99         int error, ncontig;
  100         int i;
  101 
  102         error = 0;
  103         bo = &vp->v_bufobj;
  104         if (!unmapped_buf_allowed)
  105                 gbflags &= ~GB_UNMAPPED;
  106 
  107         /*
  108          * Try to limit the amount of read-ahead by a few
  109          * ad-hoc parameters.  This needs work!!!
  110          */
  111         racluster = vp->v_mount->mnt_iosize_max / size;
  112         maxra = seqcount;
  113         maxra = min(read_max, maxra);
  114         maxra = min(nbuf/8, maxra);
  115         if (((u_quad_t)(lblkno + maxra + 1) * size) > filesize)
  116                 maxra = (filesize / size) - lblkno;
  117 
  118         /*
  119          * get the requested block
  120          */
  121         *bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0, gbflags);
  122         origblkno = lblkno;
  123 
  124         /*
  125          * if it is in the cache, then check to see if the reads have been
  126          * sequential.  If they have, then try some read-ahead, otherwise
  127          * back-off on prospective read-aheads.
  128          */
  129         if (bp->b_flags & B_CACHE) {
  130                 if (!seqcount) {
  131                         return 0;
  132                 } else if ((bp->b_flags & B_RAM) == 0) {
  133                         return 0;
  134                 } else {
  135                         bp->b_flags &= ~B_RAM;
  136                         BO_RLOCK(bo);
  137                         for (i = 1; i < maxra; i++) {
  138                                 /*
  139                                  * Stop if the buffer does not exist or it
  140                                  * is invalid (about to go away?)
  141                                  */
  142                                 rbp = gbincore(&vp->v_bufobj, lblkno+i);
  143                                 if (rbp == NULL || (rbp->b_flags & B_INVAL))
  144                                         break;
  145 
  146                                 /*
  147                                  * Set another read-ahead mark so we know 
  148                                  * to check again. (If we can lock the
  149                                  * buffer without waiting)
  150                                  */
  151                                 if ((((i % racluster) == (racluster - 1)) ||
  152                                     (i == (maxra - 1))) 
  153                                     && (0 == BUF_LOCK(rbp, 
  154                                         LK_EXCLUSIVE | LK_NOWAIT, NULL))) {
  155                                         rbp->b_flags |= B_RAM;
  156                                         BUF_UNLOCK(rbp);
  157                                 }                       
  158                         }
  159                         BO_RUNLOCK(bo);
  160                         if (i >= maxra) {
  161                                 return 0;
  162                         }
  163                         lblkno += i;
  164                 }
  165                 reqbp = bp = NULL;
  166         /*
  167          * If it isn't in the cache, then get a chunk from
  168          * disk if sequential, otherwise just get the block.
  169          */
  170         } else {
  171                 off_t firstread = bp->b_offset;
  172                 int nblks;
  173                 long minread;
  174 
  175                 KASSERT(bp->b_offset != NOOFFSET,
  176                     ("cluster_read: no buffer offset"));
  177 
  178                 ncontig = 0;
  179 
  180                 /*
  181                  * Adjust totread if needed
  182                  */
  183                 minread = read_min * size;
  184                 if (minread > totread)
  185                         totread = minread;
  186 
  187                 /*
  188                  * Compute the total number of blocks that we should read
  189                  * synchronously.
  190                  */
  191                 if (firstread + totread > filesize)
  192                         totread = filesize - firstread;
  193                 nblks = howmany(totread, size);
  194                 if (nblks > racluster)
  195                         nblks = racluster;
  196 
  197                 /*
  198                  * Now compute the number of contiguous blocks.
  199                  */
  200                 if (nblks > 1) {
  201                         error = VOP_BMAP(vp, lblkno, NULL,
  202                                 &blkno, &ncontig, NULL);
  203                         /*
  204                          * If this failed to map just do the original block.
  205                          */
  206                         if (error || blkno == -1)
  207                                 ncontig = 0;
  208                 }
  209 
  210                 /*
  211                  * If we have contiguous data available do a cluster
  212                  * otherwise just read the requested block.
  213                  */
  214                 if (ncontig) {
  215                         /* Account for our first block. */
  216                         ncontig = min(ncontig + 1, nblks);
  217                         if (ncontig < nblks)
  218                                 nblks = ncontig;
  219                         bp = cluster_rbuild(vp, filesize, lblkno,
  220                             blkno, size, nblks, gbflags, bp);
  221                         lblkno += (bp->b_bufsize / size);
  222                 } else {
  223                         bp->b_flags |= B_RAM;
  224                         bp->b_iocmd = BIO_READ;
  225                         lblkno += 1;
  226                 }
  227         }
  228 
  229         /*
  230          * handle the synchronous read so that it is available ASAP.
  231          */
  232         if (bp) {
  233                 if ((bp->b_flags & B_CLUSTER) == 0) {
  234                         vfs_busy_pages(bp, 0);
  235                 }
  236                 bp->b_flags &= ~B_INVAL;
  237                 bp->b_ioflags &= ~BIO_ERROR;
  238                 if ((bp->b_flags & B_ASYNC) || bp->b_iodone != NULL)
  239                         BUF_KERNPROC(bp);
  240                 bp->b_iooffset = dbtob(bp->b_blkno);
  241                 bstrategy(bp);
  242                 curthread->td_ru.ru_inblock++;
  243         }
  244 
  245         /*
  246          * If we have been doing sequential I/O, then do some read-ahead.
  247          */
  248         while (lblkno < (origblkno + maxra)) {
  249                 error = VOP_BMAP(vp, lblkno, NULL, &blkno, &ncontig, NULL);
  250                 if (error)
  251                         break;
  252 
  253                 if (blkno == -1)
  254                         break;
  255 
  256                 /*
  257                  * We could throttle ncontig here by maxra but we might as
  258                  * well read the data if it is contiguous.  We're throttled
  259                  * by racluster anyway.
  260                  */
  261                 if (ncontig) {
  262                         ncontig = min(ncontig + 1, racluster);
  263                         rbp = cluster_rbuild(vp, filesize, lblkno, blkno,
  264                             size, ncontig, gbflags, NULL);
  265                         lblkno += (rbp->b_bufsize / size);
  266                         if (rbp->b_flags & B_DELWRI) {
  267                                 bqrelse(rbp);
  268                                 continue;
  269                         }
  270                 } else {
  271                         rbp = getblk(vp, lblkno, size, 0, 0, gbflags);
  272                         lblkno += 1;
  273                         if (rbp->b_flags & B_DELWRI) {
  274                                 bqrelse(rbp);
  275                                 continue;
  276                         }
  277                         rbp->b_flags |= B_ASYNC | B_RAM;
  278                         rbp->b_iocmd = BIO_READ;
  279                         rbp->b_blkno = blkno;
  280                 }
  281                 if (rbp->b_flags & B_CACHE) {
  282                         rbp->b_flags &= ~B_ASYNC;
  283                         bqrelse(rbp);
  284                         continue;
  285                 }
  286                 if ((rbp->b_flags & B_CLUSTER) == 0) {
  287                         vfs_busy_pages(rbp, 0);
  288                 }
  289                 rbp->b_flags &= ~B_INVAL;
  290                 rbp->b_ioflags &= ~BIO_ERROR;
  291                 if ((rbp->b_flags & B_ASYNC) || rbp->b_iodone != NULL)
  292                         BUF_KERNPROC(rbp);
  293                 rbp->b_iooffset = dbtob(rbp->b_blkno);
  294                 bstrategy(rbp);
  295                 curthread->td_ru.ru_inblock++;
  296         }
  297 
  298         if (reqbp)
  299                 return (bufwait(reqbp));
  300         else
  301                 return (error);
  302 }
  303 
  304 /*
  305  * If blocks are contiguous on disk, use this to provide clustered
  306  * read ahead.  We will read as many blocks as possible sequentially
  307  * and then parcel them up into logical blocks in the buffer hash table.
  308  */
  309 static struct buf *
  310 cluster_rbuild(struct vnode *vp, u_quad_t filesize, daddr_t lbn,
  311     daddr_t blkno, long size, int run, int gbflags, struct buf *fbp)
  312 {
  313         struct buf *bp, *tbp;
  314         daddr_t bn;
  315         off_t off;
  316         long tinc, tsize;
  317         int i, inc, j, k, toff;
  318 
  319         KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
  320             ("cluster_rbuild: size %ld != f_iosize %jd\n",
  321             size, (intmax_t)vp->v_mount->mnt_stat.f_iosize));
  322 
  323         /*
  324          * avoid a division
  325          */
  326         while ((u_quad_t) size * (lbn + run) > filesize) {
  327                 --run;
  328         }
  329 
  330         if (fbp) {
  331                 tbp = fbp;
  332                 tbp->b_iocmd = BIO_READ; 
  333         } else {
  334                 tbp = getblk(vp, lbn, size, 0, 0, gbflags);
  335                 if (tbp->b_flags & B_CACHE)
  336                         return tbp;
  337                 tbp->b_flags |= B_ASYNC | B_RAM;
  338                 tbp->b_iocmd = BIO_READ;
  339         }
  340         tbp->b_blkno = blkno;
  341         if( (tbp->b_flags & B_MALLOC) ||
  342                 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
  343                 return tbp;
  344 
  345         bp = trypbuf(&cluster_pbuf_freecnt);
  346         if (bp == 0)
  347                 return tbp;
  348 
  349         /*
  350          * We are synthesizing a buffer out of vm_page_t's, but
  351          * if the block size is not page aligned then the starting
  352          * address may not be either.  Inherit the b_data offset
  353          * from the original buffer.
  354          */
  355         bp->b_flags = B_ASYNC | B_CLUSTER | B_VMIO;
  356         if ((gbflags & GB_UNMAPPED) != 0) {
  357                 bp->b_flags |= B_UNMAPPED;
  358                 bp->b_data = unmapped_buf;
  359         } else {
  360                 bp->b_data = (char *)((vm_offset_t)bp->b_data |
  361                     ((vm_offset_t)tbp->b_data & PAGE_MASK));
  362         }
  363         bp->b_iocmd = BIO_READ;
  364         bp->b_iodone = cluster_callback;
  365         bp->b_blkno = blkno;
  366         bp->b_lblkno = lbn;
  367         bp->b_offset = tbp->b_offset;
  368         KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
  369         pbgetvp(vp, bp);
  370 
  371         TAILQ_INIT(&bp->b_cluster.cluster_head);
  372 
  373         bp->b_bcount = 0;
  374         bp->b_bufsize = 0;
  375         bp->b_npages = 0;
  376 
  377         inc = btodb(size);
  378         for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
  379                 if (i == 0) {
  380                         VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  381                         vfs_drain_busy_pages(tbp);
  382                         vm_object_pip_add(tbp->b_bufobj->bo_object,
  383                             tbp->b_npages);
  384                         for (k = 0; k < tbp->b_npages; k++)
  385                                 vm_page_sbusy(tbp->b_pages[k]);
  386                         VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
  387                 } else {
  388                         if ((bp->b_npages * PAGE_SIZE) +
  389                             round_page(size) > vp->v_mount->mnt_iosize_max) {
  390                                 break;
  391                         }
  392 
  393                         tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT |
  394                             (gbflags & GB_UNMAPPED));
  395 
  396                         /* Don't wait around for locked bufs. */
  397                         if (tbp == NULL)
  398                                 break;
  399 
  400                         /*
  401                          * Stop scanning if the buffer is fully valid
  402                          * (marked B_CACHE), or locked (may be doing a
  403                          * background write), or if the buffer is not
  404                          * VMIO backed.  The clustering code can only deal
  405                          * with VMIO-backed buffers.  The bo lock is not
  406                          * required for the BKGRDINPROG check since it
  407                          * can not be set without the buf lock.
  408                          */
  409                         if ((tbp->b_vflags & BV_BKGRDINPROG) ||
  410                             (tbp->b_flags & B_CACHE) ||
  411                             (tbp->b_flags & B_VMIO) == 0) {
  412                                 bqrelse(tbp);
  413                                 break;
  414                         }
  415 
  416                         /*
  417                          * The buffer must be completely invalid in order to
  418                          * take part in the cluster.  If it is partially valid
  419                          * then we stop.
  420                          */
  421                         off = tbp->b_offset;
  422                         tsize = size;
  423                         VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  424                         for (j = 0; tsize > 0; j++) {
  425                                 toff = off & PAGE_MASK;
  426                                 tinc = tsize;
  427                                 if (toff + tinc > PAGE_SIZE)
  428                                         tinc = PAGE_SIZE - toff;
  429                                 VM_OBJECT_ASSERT_WLOCKED(tbp->b_pages[j]->object);
  430                                 if ((tbp->b_pages[j]->valid &
  431                                     vm_page_bits(toff, tinc)) != 0)
  432                                         break;
  433                                 if (vm_page_xbusied(tbp->b_pages[j]))
  434                                         break;
  435                                 vm_object_pip_add(tbp->b_bufobj->bo_object, 1);
  436                                 vm_page_sbusy(tbp->b_pages[j]);
  437                                 off += tinc;
  438                                 tsize -= tinc;
  439                         }
  440                         if (tsize > 0) {
  441 clean_sbusy:
  442                                 vm_object_pip_add(tbp->b_bufobj->bo_object, -j);
  443                                 for (k = 0; k < j; k++)
  444                                         vm_page_sunbusy(tbp->b_pages[k]);
  445                                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
  446                                 bqrelse(tbp);
  447                                 break;
  448                         }
  449                         VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
  450 
  451                         /*
  452                          * Set a read-ahead mark as appropriate
  453                          */
  454                         if ((fbp && (i == 1)) || (i == (run - 1)))
  455                                 tbp->b_flags |= B_RAM;
  456 
  457                         /*
  458                          * Set the buffer up for an async read (XXX should
  459                          * we do this only if we do not wind up brelse()ing?).
  460                          * Set the block number if it isn't set, otherwise
  461                          * if it is make sure it matches the block number we
  462                          * expect.
  463                          */
  464                         tbp->b_flags |= B_ASYNC;
  465                         tbp->b_iocmd = BIO_READ;
  466                         if (tbp->b_blkno == tbp->b_lblkno) {
  467                                 tbp->b_blkno = bn;
  468                         } else if (tbp->b_blkno != bn) {
  469                                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  470                                 goto clean_sbusy;
  471                         }
  472                 }
  473                 /*
  474                  * XXX fbp from caller may not be B_ASYNC, but we are going
  475                  * to biodone() it in cluster_callback() anyway
  476                  */
  477                 BUF_KERNPROC(tbp);
  478                 TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
  479                         tbp, b_cluster.cluster_entry);
  480                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  481                 for (j = 0; j < tbp->b_npages; j += 1) {
  482                         vm_page_t m;
  483                         m = tbp->b_pages[j];
  484                         if ((bp->b_npages == 0) ||
  485                             (bp->b_pages[bp->b_npages-1] != m)) {
  486                                 bp->b_pages[bp->b_npages] = m;
  487                                 bp->b_npages++;
  488                         }
  489                         if (m->valid == VM_PAGE_BITS_ALL)
  490                                 tbp->b_pages[j] = bogus_page;
  491                 }
  492                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
  493                 /*
  494                  * Don't inherit tbp->b_bufsize as it may be larger due to
  495                  * a non-page-aligned size.  Instead just aggregate using
  496                  * 'size'.
  497                  */
  498                 if (tbp->b_bcount != size)
  499                         printf("warning: tbp->b_bcount wrong %ld vs %ld\n", tbp->b_bcount, size);
  500                 if (tbp->b_bufsize != size)
  501                         printf("warning: tbp->b_bufsize wrong %ld vs %ld\n", tbp->b_bufsize, size);
  502                 bp->b_bcount += size;
  503                 bp->b_bufsize += size;
  504         }
  505 
  506         /*
  507          * Fully valid pages in the cluster are already good and do not need
  508          * to be re-read from disk.  Replace the page with bogus_page
  509          */
  510         VM_OBJECT_WLOCK(bp->b_bufobj->bo_object);
  511         for (j = 0; j < bp->b_npages; j++) {
  512                 VM_OBJECT_ASSERT_WLOCKED(bp->b_pages[j]->object);
  513                 if (bp->b_pages[j]->valid == VM_PAGE_BITS_ALL)
  514                         bp->b_pages[j] = bogus_page;
  515         }
  516         VM_OBJECT_WUNLOCK(bp->b_bufobj->bo_object);
  517         if (bp->b_bufsize > bp->b_kvasize)
  518                 panic("cluster_rbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
  519                     bp->b_bufsize, bp->b_kvasize);
  520         bp->b_kvasize = bp->b_bufsize;
  521 
  522         if ((bp->b_flags & B_UNMAPPED) == 0) {
  523                 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
  524                     (vm_page_t *)bp->b_pages, bp->b_npages);
  525         }
  526         return (bp);
  527 }
  528 
  529 /*
  530  * Cleanup after a clustered read or write.
  531  * This is complicated by the fact that any of the buffers might have
  532  * extra memory (if there were no empty buffer headers at allocbuf time)
  533  * that we will need to shift around.
  534  */
  535 static void
  536 cluster_callback(bp)
  537         struct buf *bp;
  538 {
  539         struct buf *nbp, *tbp;
  540         int error = 0;
  541 
  542         /*
  543          * Must propagate errors to all the components.
  544          */
  545         if (bp->b_ioflags & BIO_ERROR)
  546                 error = bp->b_error;
  547 
  548         if ((bp->b_flags & B_UNMAPPED) == 0) {
  549                 pmap_qremove(trunc_page((vm_offset_t) bp->b_data),
  550                     bp->b_npages);
  551         }
  552         /*
  553          * Move memory from the large cluster buffer into the component
  554          * buffers and mark IO as done on these.
  555          */
  556         for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
  557                 tbp; tbp = nbp) {
  558                 nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
  559                 if (error) {
  560                         tbp->b_ioflags |= BIO_ERROR;
  561                         tbp->b_error = error;
  562                 } else {
  563                         tbp->b_dirtyoff = tbp->b_dirtyend = 0;
  564                         tbp->b_flags &= ~B_INVAL;
  565                         tbp->b_ioflags &= ~BIO_ERROR;
  566                         /*
  567                          * XXX the bdwrite()/bqrelse() issued during
  568                          * cluster building clears B_RELBUF (see bqrelse()
  569                          * comment).  If direct I/O was specified, we have
  570                          * to restore it here to allow the buffer and VM
  571                          * to be freed.
  572                          */
  573                         if (tbp->b_flags & B_DIRECT)
  574                                 tbp->b_flags |= B_RELBUF;
  575                 }
  576                 bufdone(tbp);
  577         }
  578         pbrelvp(bp);
  579         relpbuf(bp, &cluster_pbuf_freecnt);
  580 }
  581 
  582 /*
  583  *      cluster_wbuild_wb:
  584  *
  585  *      Implement modified write build for cluster.
  586  *
  587  *              write_behind = 0        write behind disabled
  588  *              write_behind = 1        write behind normal (default)
  589  *              write_behind = 2        write behind backed-off
  590  */
  591 
  592 static __inline int
  593 cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len,
  594     int gbflags)
  595 {
  596         int r = 0;
  597 
  598         switch (write_behind) {
  599         case 2:
  600                 if (start_lbn < len)
  601                         break;
  602                 start_lbn -= len;
  603                 /* FALLTHROUGH */
  604         case 1:
  605                 r = cluster_wbuild(vp, size, start_lbn, len, gbflags);
  606                 /* FALLTHROUGH */
  607         default:
  608                 /* FALLTHROUGH */
  609                 break;
  610         }
  611         return(r);
  612 }
  613 
  614 /*
  615  * Do clustered write for FFS.
  616  *
  617  * Three cases:
  618  *      1. Write is not sequential (write asynchronously)
  619  *      Write is sequential:
  620  *      2.      beginning of cluster - begin cluster
  621  *      3.      middle of a cluster - add to cluster
  622  *      4.      end of a cluster - asynchronously write cluster
  623  */
  624 void
  625 cluster_write(struct vnode *vp, struct buf *bp, u_quad_t filesize, int seqcount,
  626     int gbflags)
  627 {
  628         daddr_t lbn;
  629         int maxclen, cursize;
  630         int lblocksize;
  631         int async;
  632 
  633         if (!unmapped_buf_allowed)
  634                 gbflags &= ~GB_UNMAPPED;
  635 
  636         if (vp->v_type == VREG) {
  637                 async = DOINGASYNC(vp);
  638                 lblocksize = vp->v_mount->mnt_stat.f_iosize;
  639         } else {
  640                 async = 0;
  641                 lblocksize = bp->b_bufsize;
  642         }
  643         lbn = bp->b_lblkno;
  644         KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));
  645 
  646         /* Initialize vnode to beginning of file. */
  647         if (lbn == 0)
  648                 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
  649 
  650         if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
  651             (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
  652                 maxclen = vp->v_mount->mnt_iosize_max / lblocksize - 1;
  653                 if (vp->v_clen != 0) {
  654                         /*
  655                          * Next block is not sequential.
  656                          *
  657                          * If we are not writing at end of file, the process
  658                          * seeked to another point in the file since its last
  659                          * write, or we have reached our maximum cluster size,
  660                          * then push the previous cluster. Otherwise try
  661                          * reallocating to make it sequential.
  662                          *
  663                          * Change to algorithm: only push previous cluster if
  664                          * it was sequential from the point of view of the
  665                          * seqcount heuristic, otherwise leave the buffer 
  666                          * intact so we can potentially optimize the I/O
  667                          * later on in the buf_daemon or update daemon
  668                          * flush.
  669                          */
  670                         cursize = vp->v_lastw - vp->v_cstart + 1;
  671                         if (((u_quad_t) bp->b_offset + lblocksize) != filesize ||
  672                             lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
  673                                 if (!async && seqcount > 0) {
  674                                         cluster_wbuild_wb(vp, lblocksize,
  675                                             vp->v_cstart, cursize, gbflags);
  676                                 }
  677                         } else {
  678                                 struct buf **bpp, **endbp;
  679                                 struct cluster_save *buflist;
  680 
  681                                 buflist = cluster_collectbufs(vp, bp, gbflags);
  682                                 endbp = &buflist->bs_children
  683                                     [buflist->bs_nchildren - 1];
  684                                 if (VOP_REALLOCBLKS(vp, buflist)) {
  685                                         /*
  686                                          * Failed, push the previous cluster
  687                                          * if *really* writing sequentially
  688                                          * in the logical file (seqcount > 1),
  689                                          * otherwise delay it in the hopes that
  690                                          * the low level disk driver can
  691                                          * optimize the write ordering.
  692                                          */
  693                                         for (bpp = buflist->bs_children;
  694                                              bpp < endbp; bpp++)
  695                                                 brelse(*bpp);
  696                                         free(buflist, M_SEGMENT);
  697                                         if (seqcount > 1) {
  698                                                 cluster_wbuild_wb(vp, 
  699                                                     lblocksize, vp->v_cstart, 
  700                                                     cursize, gbflags);
  701                                         }
  702                                 } else {
  703                                         /*
  704                                          * Succeeded, keep building cluster.
  705                                          */
  706                                         for (bpp = buflist->bs_children;
  707                                              bpp <= endbp; bpp++)
  708                                                 bdwrite(*bpp);
  709                                         free(buflist, M_SEGMENT);
  710                                         vp->v_lastw = lbn;
  711                                         vp->v_lasta = bp->b_blkno;
  712                                         return;
  713                                 }
  714                         }
  715                 }
  716                 /*
  717                  * Consider beginning a cluster. If at end of file, make
  718                  * cluster as large as possible, otherwise find size of
  719                  * existing cluster.
  720                  */
  721                 if ((vp->v_type == VREG) &&
  722                         ((u_quad_t) bp->b_offset + lblocksize) != filesize &&
  723                     (bp->b_blkno == bp->b_lblkno) &&
  724                     (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
  725                      bp->b_blkno == -1)) {
  726                         bawrite(bp);
  727                         vp->v_clen = 0;
  728                         vp->v_lasta = bp->b_blkno;
  729                         vp->v_cstart = lbn + 1;
  730                         vp->v_lastw = lbn;
  731                         return;
  732                 }
  733                 vp->v_clen = maxclen;
  734                 if (!async && maxclen == 0) {   /* I/O not contiguous */
  735                         vp->v_cstart = lbn + 1;
  736                         bawrite(bp);
  737                 } else {        /* Wait for rest of cluster */
  738                         vp->v_cstart = lbn;
  739                         bdwrite(bp);
  740                 }
  741         } else if (lbn == vp->v_cstart + vp->v_clen) {
  742                 /*
  743                  * At end of cluster, write it out if seqcount tells us we
  744                  * are operating sequentially, otherwise let the buf or
  745                  * update daemon handle it.
  746                  */
  747                 bdwrite(bp);
  748                 if (seqcount > 1) {
  749                         cluster_wbuild_wb(vp, lblocksize, vp->v_cstart,
  750                             vp->v_clen + 1, gbflags);
  751                 }
  752                 vp->v_clen = 0;
  753                 vp->v_cstart = lbn + 1;
  754         } else if (vm_page_count_severe()) {
  755                 /*
  756                  * We are low on memory, get it going NOW
  757                  */
  758                 bawrite(bp);
  759         } else {
  760                 /*
  761                  * In the middle of a cluster, so just delay the I/O for now.
  762                  */
  763                 bdwrite(bp);
  764         }
  765         vp->v_lastw = lbn;
  766         vp->v_lasta = bp->b_blkno;
  767 }
  768 
  769 
  770 /*
  771  * This is an awful lot like cluster_rbuild...wish they could be combined.
  772  * The last lbn argument is the current block on which I/O is being
  773  * performed.  Check to see that it doesn't fall in the middle of
  774  * the current block (if last_bp == NULL).
  775  */
  776 int
  777 cluster_wbuild(struct vnode *vp, long size, daddr_t start_lbn, int len,
  778     int gbflags)
  779 {
  780         struct buf *bp, *tbp;
  781         struct bufobj *bo;
  782         int i, j;
  783         int totalwritten = 0;
  784         int dbsize = btodb(size);
  785 
  786         if (!unmapped_buf_allowed)
  787                 gbflags &= ~GB_UNMAPPED;
  788 
  789         bo = &vp->v_bufobj;
  790         while (len > 0) {
  791                 /*
  792                  * If the buffer is not delayed-write (i.e. dirty), or it
  793                  * is delayed-write but either locked or inval, it cannot
  794                  * partake in the clustered write.
  795                  */
  796                 BO_LOCK(bo);
  797                 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
  798                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  799                         BO_UNLOCK(bo);
  800                         ++start_lbn;
  801                         --len;
  802                         continue;
  803                 }
  804                 if (BUF_LOCK(tbp,
  805                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, BO_LOCKPTR(bo))) {
  806                         ++start_lbn;
  807                         --len;
  808                         continue;
  809                 }
  810                 if ((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) {
  811                         BUF_UNLOCK(tbp);
  812                         ++start_lbn;
  813                         --len;
  814                         continue;
  815                 }
  816                 if (tbp->b_pin_count >  0) {
  817                         BUF_UNLOCK(tbp);
  818                         ++start_lbn;
  819                         --len;
  820                         continue;
  821                 }
  822                 bremfree(tbp);
  823                 tbp->b_flags &= ~B_DONE;
  824 
  825                 /*
  826                  * Extra memory in the buffer, punt on this buffer.
  827                  * XXX we could handle this in most cases, but we would
  828                  * have to push the extra memory down to after our max
  829                  * possible cluster size and then potentially pull it back
  830                  * up if the cluster was terminated prematurely--too much
  831                  * hassle.
  832                  */
  833                 if (((tbp->b_flags & (B_CLUSTEROK | B_MALLOC | B_VMIO)) != 
  834                      (B_CLUSTEROK | B_VMIO)) ||
  835                   (tbp->b_bcount != tbp->b_bufsize) ||
  836                   (tbp->b_bcount != size) ||
  837                   (len == 1) ||
  838                   ((bp = (vp->v_vflag & VV_MD) != 0 ?
  839                   trypbuf(&cluster_pbuf_freecnt) :
  840                   getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
  841                         totalwritten += tbp->b_bufsize;
  842                         bawrite(tbp);
  843                         ++start_lbn;
  844                         --len;
  845                         continue;
  846                 }
  847 
  848                 /*
  849                  * We got a pbuf to make the cluster in.
  850                  * so initialise it.
  851                  */
  852                 TAILQ_INIT(&bp->b_cluster.cluster_head);
  853                 bp->b_bcount = 0;
  854                 bp->b_bufsize = 0;
  855                 bp->b_npages = 0;
  856                 if (tbp->b_wcred != NOCRED)
  857                         bp->b_wcred = crhold(tbp->b_wcred);
  858 
  859                 bp->b_blkno = tbp->b_blkno;
  860                 bp->b_lblkno = tbp->b_lblkno;
  861                 bp->b_offset = tbp->b_offset;
  862 
  863                 /*
  864                  * We are synthesizing a buffer out of vm_page_t's, but
  865                  * if the block size is not page aligned then the starting
  866                  * address may not be either.  Inherit the b_data offset
  867                  * from the original buffer.
  868                  */
  869                 if ((gbflags & GB_UNMAPPED) == 0 ||
  870                     (tbp->b_flags & B_VMIO) == 0) {
  871                         bp->b_data = (char *)((vm_offset_t)bp->b_data |
  872                             ((vm_offset_t)tbp->b_data & PAGE_MASK));
  873                 } else {
  874                         bp->b_flags |= B_UNMAPPED;
  875                         bp->b_data = unmapped_buf;
  876                 }
  877                 bp->b_flags |= B_CLUSTER | (tbp->b_flags & (B_VMIO |
  878                     B_NEEDCOMMIT));
  879                 bp->b_iodone = cluster_callback;
  880                 pbgetvp(vp, bp);
  881                 /*
  882                  * From this location in the file, scan forward to see
  883                  * if there are buffers with adjacent data that need to
  884                  * be written as well.
  885                  */
  886                 for (i = 0; i < len; ++i, ++start_lbn) {
  887                         if (i != 0) { /* If not the first buffer */
  888                                 /*
  889                                  * If the adjacent data is not even in core it
  890                                  * can't need to be written.
  891                                  */
  892                                 BO_LOCK(bo);
  893                                 if ((tbp = gbincore(bo, start_lbn)) == NULL ||
  894                                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  895                                         BO_UNLOCK(bo);
  896                                         break;
  897                                 }
  898 
  899                                 /*
  900                                  * If it IS in core, but has different
  901                                  * characteristics, or is locked (which
  902                                  * means it could be undergoing a background
  903                                  * I/O or be in a weird state), then don't
  904                                  * cluster with it.
  905                                  */
  906                                 if (BUF_LOCK(tbp,
  907                                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
  908                                     BO_LOCKPTR(bo)))
  909                                         break;
  910 
  911                                 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
  912                                     B_INVAL | B_DELWRI | B_NEEDCOMMIT))
  913                                     != (B_DELWRI | B_CLUSTEROK |
  914                                     (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
  915                                     tbp->b_wcred != bp->b_wcred) {
  916                                         BUF_UNLOCK(tbp);
  917                                         break;
  918                                 }
  919 
  920                                 /*
  921                                  * Check that the combined cluster
  922                                  * would make sense with regard to pages
  923                                  * and would not be too large
  924                                  */
  925                                 if ((tbp->b_bcount != size) ||
  926                                   ((bp->b_blkno + (dbsize * i)) !=
  927                                     tbp->b_blkno) ||
  928                                   ((tbp->b_npages + bp->b_npages) >
  929                                     (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
  930                                         BUF_UNLOCK(tbp);
  931                                         break;
  932                                 }
  933 
  934                                 /*
  935                                  * Do not pull in pinned buffers.
  936                                  */
  937                                 if (tbp->b_pin_count > 0) {
  938                                         BUF_UNLOCK(tbp);
  939                                         break;
  940                                 }
  941 
  942                                 /*
  943                                  * Ok, it's passed all the tests,
  944                                  * so remove it from the free list
  945                                  * and mark it busy. We will use it.
  946                                  */
  947                                 bremfree(tbp);
  948                                 tbp->b_flags &= ~B_DONE;
  949                         } /* end of code for non-first buffers only */
  950                         /*
  951                          * If the IO is via the VM then we do some
  952                          * special VM hackery (yuck).  Since the buffer's
  953                          * block size may not be page-aligned it is possible
  954                          * for a page to be shared between two buffers.  We
  955                          * have to get rid of the duplication when building
  956                          * the cluster.
  957                          */
  958                         if (tbp->b_flags & B_VMIO) {
  959                                 vm_page_t m;
  960 
  961                                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  962                                 if (i == 0) {
  963                                         vfs_drain_busy_pages(tbp);
  964                                 } else { /* if not first buffer */
  965                                         for (j = 0; j < tbp->b_npages; j += 1) {
  966                                                 m = tbp->b_pages[j];
  967                                                 if (vm_page_xbusied(m)) {
  968                                                         VM_OBJECT_WUNLOCK(
  969                                                             tbp->b_object);
  970                                                         bqrelse(tbp);
  971                                                         goto finishcluster;
  972                                                 }
  973                                         }
  974                                 }
  975                                 for (j = 0; j < tbp->b_npages; j += 1) {
  976                                         m = tbp->b_pages[j];
  977                                         vm_page_sbusy(m);
  978                                         vm_object_pip_add(m->object, 1);
  979                                         if ((bp->b_npages == 0) ||
  980                                           (bp->b_pages[bp->b_npages - 1] != m)) {
  981                                                 bp->b_pages[bp->b_npages] = m;
  982                                                 bp->b_npages++;
  983                                         }
  984                                 }
  985                                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
  986                         }
  987                         bp->b_bcount += size;
  988                         bp->b_bufsize += size;
  989                         /*
  990                          * If any of the clustered buffers have their
  991                          * B_BARRIER flag set, transfer that request to
  992                          * the cluster.
  993                          */
  994                         bp->b_flags |= (tbp->b_flags & B_BARRIER);
  995                         tbp->b_flags &= ~(B_DONE | B_BARRIER);
  996                         tbp->b_flags |= B_ASYNC;
  997                         tbp->b_ioflags &= ~BIO_ERROR;
  998                         tbp->b_iocmd = BIO_WRITE;
  999                         bundirty(tbp);
 1000                         reassignbuf(tbp);               /* put on clean list */
 1001                         bufobj_wref(tbp->b_bufobj);
 1002                         BUF_KERNPROC(tbp);
 1003                         TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
 1004                                 tbp, b_cluster.cluster_entry);
 1005                 }
 1006         finishcluster:
 1007                 if ((bp->b_flags & B_UNMAPPED) == 0) {
 1008                         pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 1009                             (vm_page_t *)bp->b_pages, bp->b_npages);
 1010                 }
 1011                 if (bp->b_bufsize > bp->b_kvasize)
 1012                         panic(
 1013                             "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
 1014                             bp->b_bufsize, bp->b_kvasize);
 1015                 bp->b_kvasize = bp->b_bufsize;
 1016                 totalwritten += bp->b_bufsize;
 1017                 bp->b_dirtyoff = 0;
 1018                 bp->b_dirtyend = bp->b_bufsize;
 1019                 bawrite(bp);
 1020 
 1021                 len -= i;
 1022         }
 1023         return totalwritten;
 1024 }
 1025 
 1026 /*
 1027  * Collect together all the buffers in a cluster.
 1028  * Plus add one additional buffer.
 1029  */
 1030 static struct cluster_save *
 1031 cluster_collectbufs(struct vnode *vp, struct buf *last_bp, int gbflags)
 1032 {
 1033         struct cluster_save *buflist;
 1034         struct buf *bp;
 1035         daddr_t lbn;
 1036         int i, len;
 1037 
 1038         len = vp->v_lastw - vp->v_cstart + 1;
 1039         buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
 1040             M_SEGMENT, M_WAITOK);
 1041         buflist->bs_nchildren = 0;
 1042         buflist->bs_children = (struct buf **) (buflist + 1);
 1043         for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
 1044                 (void)bread_gb(vp, lbn, last_bp->b_bcount, NOCRED,
 1045                     gbflags, &bp);
 1046                 buflist->bs_children[i] = bp;
 1047                 if (bp->b_blkno == bp->b_lblkno)
 1048                         VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno,
 1049                                 NULL, NULL);
 1050         }
 1051         buflist->bs_children[i] = bp = last_bp;
 1052         if (bp->b_blkno == bp->b_lblkno)
 1053                 VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL);
 1054         buflist->bs_nchildren = i + 1;
 1055         return (buflist);
 1056 }

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