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

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    1 /*-
    2  * Copyright (c) 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  * Modifications/enhancements:
    5  *      Copyright (c) 1995 John S. Dyson.  All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 4. Neither the name of the University nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      @(#)vfs_cluster.c       8.7 (Berkeley) 2/13/94
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD: releng/11.1/sys/kern/vfs_cluster.c 298819 2016-04-29 22:15:33Z pfg $");
   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/racct.h>
   49 #include <sys/resourcevar.h>
   50 #include <sys/rwlock.h>
   51 #include <sys/vmmeter.h>
   52 #include <vm/vm.h>
   53 #include <vm/vm_object.h>
   54 #include <vm/vm_page.h>
   55 #include <sys/sysctl.h>
   56 
   57 #if defined(CLUSTERDEBUG)
   58 static int      rcluster= 0;
   59 SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0,
   60     "Debug VFS clustering code");
   61 #endif
   62 
   63 static MALLOC_DEFINE(M_SEGMENT, "cl_savebuf", "cluster_save buffer");
   64 
   65 static struct cluster_save *cluster_collectbufs(struct vnode *vp,
   66             struct buf *last_bp, int gbflags);
   67 static struct buf *cluster_rbuild(struct vnode *vp, u_quad_t filesize,
   68             daddr_t lbn, daddr_t blkno, long size, int run, int gbflags,
   69             struct buf *fbp);
   70 static void cluster_callback(struct buf *);
   71 
   72 static int write_behind = 1;
   73 SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0,
   74     "Cluster write-behind; 0: disable, 1: enable, 2: backed off");
   75 
   76 static int read_max = 64;
   77 SYSCTL_INT(_vfs, OID_AUTO, read_max, CTLFLAG_RW, &read_max, 0,
   78     "Cluster read-ahead max block count");
   79 
   80 static int read_min = 1;
   81 SYSCTL_INT(_vfs, OID_AUTO, read_min, CTLFLAG_RW, &read_min, 0,
   82     "Cluster read min block count");
   83 
   84 /* Page expended to mark partially backed buffers */
   85 extern vm_page_t        bogus_page;
   86 
   87 /*
   88  * Read data to a buf, including read-ahead if we find this to be beneficial.
   89  * cluster_read replaces bread.
   90  */
   91 int
   92 cluster_read(struct vnode *vp, u_quad_t filesize, daddr_t lblkno, long size,
   93     struct ucred *cred, long totread, int seqcount, int gbflags,
   94     struct buf **bpp)
   95 {
   96         struct buf *bp, *rbp, *reqbp;
   97         struct bufobj *bo;
   98         daddr_t blkno, origblkno;
   99         int maxra, racluster;
  100         int error, ncontig;
  101         int i;
  102 
  103         error = 0;
  104         bo = &vp->v_bufobj;
  105         if (!unmapped_buf_allowed)
  106                 gbflags &= ~GB_UNMAPPED;
  107 
  108         /*
  109          * Try to limit the amount of read-ahead by a few
  110          * ad-hoc parameters.  This needs work!!!
  111          */
  112         racluster = vp->v_mount->mnt_iosize_max / size;
  113         maxra = seqcount;
  114         maxra = min(read_max, maxra);
  115         maxra = min(nbuf/8, maxra);
  116         if (((u_quad_t)(lblkno + maxra + 1) * size) > filesize)
  117                 maxra = (filesize / size) - lblkno;
  118 
  119         /*
  120          * get the requested block
  121          */
  122         *bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0, gbflags);
  123         if (bp == NULL)
  124                 return (EBUSY);
  125         origblkno = lblkno;
  126 
  127         /*
  128          * if it is in the cache, then check to see if the reads have been
  129          * sequential.  If they have, then try some read-ahead, otherwise
  130          * back-off on prospective read-aheads.
  131          */
  132         if (bp->b_flags & B_CACHE) {
  133                 if (!seqcount) {
  134                         return 0;
  135                 } else if ((bp->b_flags & B_RAM) == 0) {
  136                         return 0;
  137                 } else {
  138                         bp->b_flags &= ~B_RAM;
  139                         BO_RLOCK(bo);
  140                         for (i = 1; i < maxra; i++) {
  141                                 /*
  142                                  * Stop if the buffer does not exist or it
  143                                  * is invalid (about to go away?)
  144                                  */
  145                                 rbp = gbincore(&vp->v_bufobj, lblkno+i);
  146                                 if (rbp == NULL || (rbp->b_flags & B_INVAL))
  147                                         break;
  148 
  149                                 /*
  150                                  * Set another read-ahead mark so we know 
  151                                  * to check again. (If we can lock the
  152                                  * buffer without waiting)
  153                                  */
  154                                 if ((((i % racluster) == (racluster - 1)) ||
  155                                     (i == (maxra - 1))) 
  156                                     && (0 == BUF_LOCK(rbp, 
  157                                         LK_EXCLUSIVE | LK_NOWAIT, NULL))) {
  158                                         rbp->b_flags |= B_RAM;
  159                                         BUF_UNLOCK(rbp);
  160                                 }                       
  161                         }
  162                         BO_RUNLOCK(bo);
  163                         if (i >= maxra) {
  164                                 return 0;
  165                         }
  166                         lblkno += i;
  167                 }
  168                 reqbp = bp = NULL;
  169         /*
  170          * If it isn't in the cache, then get a chunk from
  171          * disk if sequential, otherwise just get the block.
  172          */
  173         } else {
  174                 off_t firstread = bp->b_offset;
  175                 int nblks;
  176                 long minread;
  177 
  178                 KASSERT(bp->b_offset != NOOFFSET,
  179                     ("cluster_read: no buffer offset"));
  180 
  181                 ncontig = 0;
  182 
  183                 /*
  184                  * Adjust totread if needed
  185                  */
  186                 minread = read_min * size;
  187                 if (minread > totread)
  188                         totread = minread;
  189 
  190                 /*
  191                  * Compute the total number of blocks that we should read
  192                  * synchronously.
  193                  */
  194                 if (firstread + totread > filesize)
  195                         totread = filesize - firstread;
  196                 nblks = howmany(totread, size);
  197                 if (nblks > racluster)
  198                         nblks = racluster;
  199 
  200                 /*
  201                  * Now compute the number of contiguous blocks.
  202                  */
  203                 if (nblks > 1) {
  204                         error = VOP_BMAP(vp, lblkno, NULL,
  205                                 &blkno, &ncontig, NULL);
  206                         /*
  207                          * If this failed to map just do the original block.
  208                          */
  209                         if (error || blkno == -1)
  210                                 ncontig = 0;
  211                 }
  212 
  213                 /*
  214                  * If we have contiguous data available do a cluster
  215                  * otherwise just read the requested block.
  216                  */
  217                 if (ncontig) {
  218                         /* Account for our first block. */
  219                         ncontig = min(ncontig + 1, nblks);
  220                         if (ncontig < nblks)
  221                                 nblks = ncontig;
  222                         bp = cluster_rbuild(vp, filesize, lblkno,
  223                             blkno, size, nblks, gbflags, bp);
  224                         lblkno += (bp->b_bufsize / size);
  225                 } else {
  226                         bp->b_flags |= B_RAM;
  227                         bp->b_iocmd = BIO_READ;
  228                         lblkno += 1;
  229                 }
  230         }
  231 
  232         /*
  233          * handle the synchronous read so that it is available ASAP.
  234          */
  235         if (bp) {
  236                 if ((bp->b_flags & B_CLUSTER) == 0) {
  237                         vfs_busy_pages(bp, 0);
  238                 }
  239                 bp->b_flags &= ~B_INVAL;
  240                 bp->b_ioflags &= ~BIO_ERROR;
  241                 if ((bp->b_flags & B_ASYNC) || bp->b_iodone != NULL)
  242                         BUF_KERNPROC(bp);
  243                 bp->b_iooffset = dbtob(bp->b_blkno);
  244                 bstrategy(bp);
  245 #ifdef RACCT
  246                 if (racct_enable) {
  247                         PROC_LOCK(curproc);
  248                         racct_add_buf(curproc, bp, 0);
  249                         PROC_UNLOCK(curproc);
  250                 }
  251 #endif /* RACCT */
  252                 curthread->td_ru.ru_inblock++;
  253         }
  254 
  255         /*
  256          * If we have been doing sequential I/O, then do some read-ahead.
  257          */
  258         while (lblkno < (origblkno + maxra)) {
  259                 error = VOP_BMAP(vp, lblkno, NULL, &blkno, &ncontig, NULL);
  260                 if (error)
  261                         break;
  262 
  263                 if (blkno == -1)
  264                         break;
  265 
  266                 /*
  267                  * We could throttle ncontig here by maxra but we might as
  268                  * well read the data if it is contiguous.  We're throttled
  269                  * by racluster anyway.
  270                  */
  271                 if (ncontig) {
  272                         ncontig = min(ncontig + 1, racluster);
  273                         rbp = cluster_rbuild(vp, filesize, lblkno, blkno,
  274                             size, ncontig, gbflags, NULL);
  275                         lblkno += (rbp->b_bufsize / size);
  276                         if (rbp->b_flags & B_DELWRI) {
  277                                 bqrelse(rbp);
  278                                 continue;
  279                         }
  280                 } else {
  281                         rbp = getblk(vp, lblkno, size, 0, 0, gbflags);
  282                         lblkno += 1;
  283                         if (rbp->b_flags & B_DELWRI) {
  284                                 bqrelse(rbp);
  285                                 continue;
  286                         }
  287                         rbp->b_flags |= B_ASYNC | B_RAM;
  288                         rbp->b_iocmd = BIO_READ;
  289                         rbp->b_blkno = blkno;
  290                 }
  291                 if (rbp->b_flags & B_CACHE) {
  292                         rbp->b_flags &= ~B_ASYNC;
  293                         bqrelse(rbp);
  294                         continue;
  295                 }
  296                 if ((rbp->b_flags & B_CLUSTER) == 0) {
  297                         vfs_busy_pages(rbp, 0);
  298                 }
  299                 rbp->b_flags &= ~B_INVAL;
  300                 rbp->b_ioflags &= ~BIO_ERROR;
  301                 if ((rbp->b_flags & B_ASYNC) || rbp->b_iodone != NULL)
  302                         BUF_KERNPROC(rbp);
  303                 rbp->b_iooffset = dbtob(rbp->b_blkno);
  304                 bstrategy(rbp);
  305 #ifdef RACCT
  306                 if (racct_enable) {
  307                         PROC_LOCK(curproc);
  308                         racct_add_buf(curproc, rbp, 0);
  309                         PROC_UNLOCK(curproc);
  310                 }
  311 #endif /* RACCT */
  312                 curthread->td_ru.ru_inblock++;
  313         }
  314 
  315         if (reqbp) {
  316                 /*
  317                  * Like bread, always brelse() the buffer when
  318                  * returning an error.
  319                  */
  320                 error = bufwait(reqbp);
  321                 if (error != 0) {
  322                         brelse(reqbp);
  323                         *bpp = NULL;
  324                 }
  325         }
  326         return (error);
  327 }
  328 
  329 /*
  330  * If blocks are contiguous on disk, use this to provide clustered
  331  * read ahead.  We will read as many blocks as possible sequentially
  332  * and then parcel them up into logical blocks in the buffer hash table.
  333  */
  334 static struct buf *
  335 cluster_rbuild(struct vnode *vp, u_quad_t filesize, daddr_t lbn,
  336     daddr_t blkno, long size, int run, int gbflags, struct buf *fbp)
  337 {
  338         struct buf *bp, *tbp;
  339         daddr_t bn;
  340         off_t off;
  341         long tinc, tsize;
  342         int i, inc, j, k, toff;
  343 
  344         KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
  345             ("cluster_rbuild: size %ld != f_iosize %jd\n",
  346             size, (intmax_t)vp->v_mount->mnt_stat.f_iosize));
  347 
  348         /*
  349          * avoid a division
  350          */
  351         while ((u_quad_t) size * (lbn + run) > filesize) {
  352                 --run;
  353         }
  354 
  355         if (fbp) {
  356                 tbp = fbp;
  357                 tbp->b_iocmd = BIO_READ; 
  358         } else {
  359                 tbp = getblk(vp, lbn, size, 0, 0, gbflags);
  360                 if (tbp->b_flags & B_CACHE)
  361                         return tbp;
  362                 tbp->b_flags |= B_ASYNC | B_RAM;
  363                 tbp->b_iocmd = BIO_READ;
  364         }
  365         tbp->b_blkno = blkno;
  366         if( (tbp->b_flags & B_MALLOC) ||
  367                 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
  368                 return tbp;
  369 
  370         bp = trypbuf(&cluster_pbuf_freecnt);
  371         if (bp == NULL)
  372                 return tbp;
  373 
  374         /*
  375          * We are synthesizing a buffer out of vm_page_t's, but
  376          * if the block size is not page aligned then the starting
  377          * address may not be either.  Inherit the b_data offset
  378          * from the original buffer.
  379          */
  380         bp->b_flags = B_ASYNC | B_CLUSTER | B_VMIO;
  381         if ((gbflags & GB_UNMAPPED) != 0) {
  382                 bp->b_data = unmapped_buf;
  383         } else {
  384                 bp->b_data = (char *)((vm_offset_t)bp->b_data |
  385                     ((vm_offset_t)tbp->b_data & PAGE_MASK));
  386         }
  387         bp->b_iocmd = BIO_READ;
  388         bp->b_iodone = cluster_callback;
  389         bp->b_blkno = blkno;
  390         bp->b_lblkno = lbn;
  391         bp->b_offset = tbp->b_offset;
  392         KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
  393         pbgetvp(vp, bp);
  394 
  395         TAILQ_INIT(&bp->b_cluster.cluster_head);
  396 
  397         bp->b_bcount = 0;
  398         bp->b_bufsize = 0;
  399         bp->b_npages = 0;
  400 
  401         inc = btodb(size);
  402         for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
  403                 if (i == 0) {
  404                         VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  405                         vfs_drain_busy_pages(tbp);
  406                         vm_object_pip_add(tbp->b_bufobj->bo_object,
  407                             tbp->b_npages);
  408                         for (k = 0; k < tbp->b_npages; k++)
  409                                 vm_page_sbusy(tbp->b_pages[k]);
  410                         VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
  411                 } else {
  412                         if ((bp->b_npages * PAGE_SIZE) +
  413                             round_page(size) > vp->v_mount->mnt_iosize_max) {
  414                                 break;
  415                         }
  416 
  417                         tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT |
  418                             (gbflags & GB_UNMAPPED));
  419 
  420                         /* Don't wait around for locked bufs. */
  421                         if (tbp == NULL)
  422                                 break;
  423 
  424                         /*
  425                          * Stop scanning if the buffer is fully valid
  426                          * (marked B_CACHE), or locked (may be doing a
  427                          * background write), or if the buffer is not
  428                          * VMIO backed.  The clustering code can only deal
  429                          * with VMIO-backed buffers.  The bo lock is not
  430                          * required for the BKGRDINPROG check since it
  431                          * can not be set without the buf lock.
  432                          */
  433                         if ((tbp->b_vflags & BV_BKGRDINPROG) ||
  434                             (tbp->b_flags & B_CACHE) ||
  435                             (tbp->b_flags & B_VMIO) == 0) {
  436                                 bqrelse(tbp);
  437                                 break;
  438                         }
  439 
  440                         /*
  441                          * The buffer must be completely invalid in order to
  442                          * take part in the cluster.  If it is partially valid
  443                          * then we stop.
  444                          */
  445                         off = tbp->b_offset;
  446                         tsize = size;
  447                         VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  448                         for (j = 0; tsize > 0; j++) {
  449                                 toff = off & PAGE_MASK;
  450                                 tinc = tsize;
  451                                 if (toff + tinc > PAGE_SIZE)
  452                                         tinc = PAGE_SIZE - toff;
  453                                 VM_OBJECT_ASSERT_WLOCKED(tbp->b_pages[j]->object);
  454                                 if ((tbp->b_pages[j]->valid &
  455                                     vm_page_bits(toff, tinc)) != 0)
  456                                         break;
  457                                 if (vm_page_xbusied(tbp->b_pages[j]))
  458                                         break;
  459                                 vm_object_pip_add(tbp->b_bufobj->bo_object, 1);
  460                                 vm_page_sbusy(tbp->b_pages[j]);
  461                                 off += tinc;
  462                                 tsize -= tinc;
  463                         }
  464                         if (tsize > 0) {
  465 clean_sbusy:
  466                                 vm_object_pip_add(tbp->b_bufobj->bo_object, -j);
  467                                 for (k = 0; k < j; k++)
  468                                         vm_page_sunbusy(tbp->b_pages[k]);
  469                                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
  470                                 bqrelse(tbp);
  471                                 break;
  472                         }
  473                         VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
  474 
  475                         /*
  476                          * Set a read-ahead mark as appropriate
  477                          */
  478                         if ((fbp && (i == 1)) || (i == (run - 1)))
  479                                 tbp->b_flags |= B_RAM;
  480 
  481                         /*
  482                          * Set the buffer up for an async read (XXX should
  483                          * we do this only if we do not wind up brelse()ing?).
  484                          * Set the block number if it isn't set, otherwise
  485                          * if it is make sure it matches the block number we
  486                          * expect.
  487                          */
  488                         tbp->b_flags |= B_ASYNC;
  489                         tbp->b_iocmd = BIO_READ;
  490                         if (tbp->b_blkno == tbp->b_lblkno) {
  491                                 tbp->b_blkno = bn;
  492                         } else if (tbp->b_blkno != bn) {
  493                                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  494                                 goto clean_sbusy;
  495                         }
  496                 }
  497                 /*
  498                  * XXX fbp from caller may not be B_ASYNC, but we are going
  499                  * to biodone() it in cluster_callback() anyway
  500                  */
  501                 BUF_KERNPROC(tbp);
  502                 TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
  503                         tbp, b_cluster.cluster_entry);
  504                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  505                 for (j = 0; j < tbp->b_npages; j += 1) {
  506                         vm_page_t m;
  507                         m = tbp->b_pages[j];
  508                         if ((bp->b_npages == 0) ||
  509                             (bp->b_pages[bp->b_npages-1] != m)) {
  510                                 bp->b_pages[bp->b_npages] = m;
  511                                 bp->b_npages++;
  512                         }
  513                         if (m->valid == VM_PAGE_BITS_ALL)
  514                                 tbp->b_pages[j] = bogus_page;
  515                 }
  516                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
  517                 /*
  518                  * Don't inherit tbp->b_bufsize as it may be larger due to
  519                  * a non-page-aligned size.  Instead just aggregate using
  520                  * 'size'.
  521                  */
  522                 if (tbp->b_bcount != size)
  523                         printf("warning: tbp->b_bcount wrong %ld vs %ld\n", tbp->b_bcount, size);
  524                 if (tbp->b_bufsize != size)
  525                         printf("warning: tbp->b_bufsize wrong %ld vs %ld\n", tbp->b_bufsize, size);
  526                 bp->b_bcount += size;
  527                 bp->b_bufsize += size;
  528         }
  529 
  530         /*
  531          * Fully valid pages in the cluster are already good and do not need
  532          * to be re-read from disk.  Replace the page with bogus_page
  533          */
  534         VM_OBJECT_WLOCK(bp->b_bufobj->bo_object);
  535         for (j = 0; j < bp->b_npages; j++) {
  536                 VM_OBJECT_ASSERT_WLOCKED(bp->b_pages[j]->object);
  537                 if (bp->b_pages[j]->valid == VM_PAGE_BITS_ALL)
  538                         bp->b_pages[j] = bogus_page;
  539         }
  540         VM_OBJECT_WUNLOCK(bp->b_bufobj->bo_object);
  541         if (bp->b_bufsize > bp->b_kvasize)
  542                 panic("cluster_rbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
  543                     bp->b_bufsize, bp->b_kvasize);
  544 
  545         if (buf_mapped(bp)) {
  546                 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
  547                     (vm_page_t *)bp->b_pages, bp->b_npages);
  548         }
  549         return (bp);
  550 }
  551 
  552 /*
  553  * Cleanup after a clustered read or write.
  554  * This is complicated by the fact that any of the buffers might have
  555  * extra memory (if there were no empty buffer headers at allocbuf time)
  556  * that we will need to shift around.
  557  */
  558 static void
  559 cluster_callback(bp)
  560         struct buf *bp;
  561 {
  562         struct buf *nbp, *tbp;
  563         int error = 0;
  564 
  565         /*
  566          * Must propagate errors to all the components.
  567          */
  568         if (bp->b_ioflags & BIO_ERROR)
  569                 error = bp->b_error;
  570 
  571         if (buf_mapped(bp)) {
  572                 pmap_qremove(trunc_page((vm_offset_t) bp->b_data),
  573                     bp->b_npages);
  574         }
  575         /*
  576          * Move memory from the large cluster buffer into the component
  577          * buffers and mark IO as done on these.
  578          */
  579         for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
  580                 tbp; tbp = nbp) {
  581                 nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
  582                 if (error) {
  583                         tbp->b_ioflags |= BIO_ERROR;
  584                         tbp->b_error = error;
  585                 } else {
  586                         tbp->b_dirtyoff = tbp->b_dirtyend = 0;
  587                         tbp->b_flags &= ~B_INVAL;
  588                         tbp->b_ioflags &= ~BIO_ERROR;
  589                         /*
  590                          * XXX the bdwrite()/bqrelse() issued during
  591                          * cluster building clears B_RELBUF (see bqrelse()
  592                          * comment).  If direct I/O was specified, we have
  593                          * to restore it here to allow the buffer and VM
  594                          * to be freed.
  595                          */
  596                         if (tbp->b_flags & B_DIRECT)
  597                                 tbp->b_flags |= B_RELBUF;
  598                 }
  599                 bufdone(tbp);
  600         }
  601         pbrelvp(bp);
  602         relpbuf(bp, &cluster_pbuf_freecnt);
  603 }
  604 
  605 /*
  606  *      cluster_wbuild_wb:
  607  *
  608  *      Implement modified write build for cluster.
  609  *
  610  *              write_behind = 0        write behind disabled
  611  *              write_behind = 1        write behind normal (default)
  612  *              write_behind = 2        write behind backed-off
  613  */
  614 
  615 static __inline int
  616 cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len,
  617     int gbflags)
  618 {
  619         int r = 0;
  620 
  621         switch (write_behind) {
  622         case 2:
  623                 if (start_lbn < len)
  624                         break;
  625                 start_lbn -= len;
  626                 /* FALLTHROUGH */
  627         case 1:
  628                 r = cluster_wbuild(vp, size, start_lbn, len, gbflags);
  629                 /* FALLTHROUGH */
  630         default:
  631                 /* FALLTHROUGH */
  632                 break;
  633         }
  634         return(r);
  635 }
  636 
  637 /*
  638  * Do clustered write for FFS.
  639  *
  640  * Three cases:
  641  *      1. Write is not sequential (write asynchronously)
  642  *      Write is sequential:
  643  *      2.      beginning of cluster - begin cluster
  644  *      3.      middle of a cluster - add to cluster
  645  *      4.      end of a cluster - asynchronously write cluster
  646  */
  647 void
  648 cluster_write(struct vnode *vp, struct buf *bp, u_quad_t filesize, int seqcount,
  649     int gbflags)
  650 {
  651         daddr_t lbn;
  652         int maxclen, cursize;
  653         int lblocksize;
  654         int async;
  655 
  656         if (!unmapped_buf_allowed)
  657                 gbflags &= ~GB_UNMAPPED;
  658 
  659         if (vp->v_type == VREG) {
  660                 async = DOINGASYNC(vp);
  661                 lblocksize = vp->v_mount->mnt_stat.f_iosize;
  662         } else {
  663                 async = 0;
  664                 lblocksize = bp->b_bufsize;
  665         }
  666         lbn = bp->b_lblkno;
  667         KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));
  668 
  669         /* Initialize vnode to beginning of file. */
  670         if (lbn == 0)
  671                 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
  672 
  673         if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
  674             (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
  675                 maxclen = vp->v_mount->mnt_iosize_max / lblocksize - 1;
  676                 if (vp->v_clen != 0) {
  677                         /*
  678                          * Next block is not sequential.
  679                          *
  680                          * If we are not writing at end of file, the process
  681                          * seeked to another point in the file since its last
  682                          * write, or we have reached our maximum cluster size,
  683                          * then push the previous cluster. Otherwise try
  684                          * reallocating to make it sequential.
  685                          *
  686                          * Change to algorithm: only push previous cluster if
  687                          * it was sequential from the point of view of the
  688                          * seqcount heuristic, otherwise leave the buffer 
  689                          * intact so we can potentially optimize the I/O
  690                          * later on in the buf_daemon or update daemon
  691                          * flush.
  692                          */
  693                         cursize = vp->v_lastw - vp->v_cstart + 1;
  694                         if (((u_quad_t) bp->b_offset + lblocksize) != filesize ||
  695                             lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
  696                                 if (!async && seqcount > 0) {
  697                                         cluster_wbuild_wb(vp, lblocksize,
  698                                             vp->v_cstart, cursize, gbflags);
  699                                 }
  700                         } else {
  701                                 struct buf **bpp, **endbp;
  702                                 struct cluster_save *buflist;
  703 
  704                                 buflist = cluster_collectbufs(vp, bp, gbflags);
  705                                 endbp = &buflist->bs_children
  706                                     [buflist->bs_nchildren - 1];
  707                                 if (VOP_REALLOCBLKS(vp, buflist)) {
  708                                         /*
  709                                          * Failed, push the previous cluster
  710                                          * if *really* writing sequentially
  711                                          * in the logical file (seqcount > 1),
  712                                          * otherwise delay it in the hopes that
  713                                          * the low level disk driver can
  714                                          * optimize the write ordering.
  715                                          */
  716                                         for (bpp = buflist->bs_children;
  717                                              bpp < endbp; bpp++)
  718                                                 brelse(*bpp);
  719                                         free(buflist, M_SEGMENT);
  720                                         if (seqcount > 1) {
  721                                                 cluster_wbuild_wb(vp, 
  722                                                     lblocksize, vp->v_cstart, 
  723                                                     cursize, gbflags);
  724                                         }
  725                                 } else {
  726                                         /*
  727                                          * Succeeded, keep building cluster.
  728                                          */
  729                                         for (bpp = buflist->bs_children;
  730                                              bpp <= endbp; bpp++)
  731                                                 bdwrite(*bpp);
  732                                         free(buflist, M_SEGMENT);
  733                                         vp->v_lastw = lbn;
  734                                         vp->v_lasta = bp->b_blkno;
  735                                         return;
  736                                 }
  737                         }
  738                 }
  739                 /*
  740                  * Consider beginning a cluster. If at end of file, make
  741                  * cluster as large as possible, otherwise find size of
  742                  * existing cluster.
  743                  */
  744                 if ((vp->v_type == VREG) &&
  745                         ((u_quad_t) bp->b_offset + lblocksize) != filesize &&
  746                     (bp->b_blkno == bp->b_lblkno) &&
  747                     (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
  748                      bp->b_blkno == -1)) {
  749                         bawrite(bp);
  750                         vp->v_clen = 0;
  751                         vp->v_lasta = bp->b_blkno;
  752                         vp->v_cstart = lbn + 1;
  753                         vp->v_lastw = lbn;
  754                         return;
  755                 }
  756                 vp->v_clen = maxclen;
  757                 if (!async && maxclen == 0) {   /* I/O not contiguous */
  758                         vp->v_cstart = lbn + 1;
  759                         bawrite(bp);
  760                 } else {        /* Wait for rest of cluster */
  761                         vp->v_cstart = lbn;
  762                         bdwrite(bp);
  763                 }
  764         } else if (lbn == vp->v_cstart + vp->v_clen) {
  765                 /*
  766                  * At end of cluster, write it out if seqcount tells us we
  767                  * are operating sequentially, otherwise let the buf or
  768                  * update daemon handle it.
  769                  */
  770                 bdwrite(bp);
  771                 if (seqcount > 1) {
  772                         cluster_wbuild_wb(vp, lblocksize, vp->v_cstart,
  773                             vp->v_clen + 1, gbflags);
  774                 }
  775                 vp->v_clen = 0;
  776                 vp->v_cstart = lbn + 1;
  777         } else if (vm_page_count_severe()) {
  778                 /*
  779                  * We are low on memory, get it going NOW
  780                  */
  781                 bawrite(bp);
  782         } else {
  783                 /*
  784                  * In the middle of a cluster, so just delay the I/O for now.
  785                  */
  786                 bdwrite(bp);
  787         }
  788         vp->v_lastw = lbn;
  789         vp->v_lasta = bp->b_blkno;
  790 }
  791 
  792 
  793 /*
  794  * This is an awful lot like cluster_rbuild...wish they could be combined.
  795  * The last lbn argument is the current block on which I/O is being
  796  * performed.  Check to see that it doesn't fall in the middle of
  797  * the current block (if last_bp == NULL).
  798  */
  799 int
  800 cluster_wbuild(struct vnode *vp, long size, daddr_t start_lbn, int len,
  801     int gbflags)
  802 {
  803         struct buf *bp, *tbp;
  804         struct bufobj *bo;
  805         int i, j;
  806         int totalwritten = 0;
  807         int dbsize = btodb(size);
  808 
  809         if (!unmapped_buf_allowed)
  810                 gbflags &= ~GB_UNMAPPED;
  811 
  812         bo = &vp->v_bufobj;
  813         while (len > 0) {
  814                 /*
  815                  * If the buffer is not delayed-write (i.e. dirty), or it
  816                  * is delayed-write but either locked or inval, it cannot
  817                  * partake in the clustered write.
  818                  */
  819                 BO_LOCK(bo);
  820                 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
  821                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  822                         BO_UNLOCK(bo);
  823                         ++start_lbn;
  824                         --len;
  825                         continue;
  826                 }
  827                 if (BUF_LOCK(tbp,
  828                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, BO_LOCKPTR(bo))) {
  829                         ++start_lbn;
  830                         --len;
  831                         continue;
  832                 }
  833                 if ((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) {
  834                         BUF_UNLOCK(tbp);
  835                         ++start_lbn;
  836                         --len;
  837                         continue;
  838                 }
  839                 if (tbp->b_pin_count >  0) {
  840                         BUF_UNLOCK(tbp);
  841                         ++start_lbn;
  842                         --len;
  843                         continue;
  844                 }
  845                 bremfree(tbp);
  846                 tbp->b_flags &= ~B_DONE;
  847 
  848                 /*
  849                  * Extra memory in the buffer, punt on this buffer.
  850                  * XXX we could handle this in most cases, but we would
  851                  * have to push the extra memory down to after our max
  852                  * possible cluster size and then potentially pull it back
  853                  * up if the cluster was terminated prematurely--too much
  854                  * hassle.
  855                  */
  856                 if (((tbp->b_flags & (B_CLUSTEROK | B_MALLOC | B_VMIO)) != 
  857                      (B_CLUSTEROK | B_VMIO)) ||
  858                   (tbp->b_bcount != tbp->b_bufsize) ||
  859                   (tbp->b_bcount != size) ||
  860                   (len == 1) ||
  861                   ((bp = (vp->v_vflag & VV_MD) != 0 ?
  862                   trypbuf(&cluster_pbuf_freecnt) :
  863                   getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
  864                         totalwritten += tbp->b_bufsize;
  865                         bawrite(tbp);
  866                         ++start_lbn;
  867                         --len;
  868                         continue;
  869                 }
  870 
  871                 /*
  872                  * We got a pbuf to make the cluster in.
  873                  * so initialise it.
  874                  */
  875                 TAILQ_INIT(&bp->b_cluster.cluster_head);
  876                 bp->b_bcount = 0;
  877                 bp->b_bufsize = 0;
  878                 bp->b_npages = 0;
  879                 if (tbp->b_wcred != NOCRED)
  880                         bp->b_wcred = crhold(tbp->b_wcred);
  881 
  882                 bp->b_blkno = tbp->b_blkno;
  883                 bp->b_lblkno = tbp->b_lblkno;
  884                 bp->b_offset = tbp->b_offset;
  885 
  886                 /*
  887                  * We are synthesizing a buffer out of vm_page_t's, but
  888                  * if the block size is not page aligned then the starting
  889                  * address may not be either.  Inherit the b_data offset
  890                  * from the original buffer.
  891                  */
  892                 if ((gbflags & GB_UNMAPPED) == 0 ||
  893                     (tbp->b_flags & B_VMIO) == 0) {
  894                         bp->b_data = (char *)((vm_offset_t)bp->b_data |
  895                             ((vm_offset_t)tbp->b_data & PAGE_MASK));
  896                 } else {
  897                         bp->b_data = unmapped_buf;
  898                 }
  899                 bp->b_flags |= B_CLUSTER | (tbp->b_flags & (B_VMIO |
  900                     B_NEEDCOMMIT));
  901                 bp->b_iodone = cluster_callback;
  902                 pbgetvp(vp, bp);
  903                 /*
  904                  * From this location in the file, scan forward to see
  905                  * if there are buffers with adjacent data that need to
  906                  * be written as well.
  907                  */
  908                 for (i = 0; i < len; ++i, ++start_lbn) {
  909                         if (i != 0) { /* If not the first buffer */
  910                                 /*
  911                                  * If the adjacent data is not even in core it
  912                                  * can't need to be written.
  913                                  */
  914                                 BO_LOCK(bo);
  915                                 if ((tbp = gbincore(bo, start_lbn)) == NULL ||
  916                                     (tbp->b_vflags & BV_BKGRDINPROG)) {
  917                                         BO_UNLOCK(bo);
  918                                         break;
  919                                 }
  920 
  921                                 /*
  922                                  * If it IS in core, but has different
  923                                  * characteristics, or is locked (which
  924                                  * means it could be undergoing a background
  925                                  * I/O or be in a weird state), then don't
  926                                  * cluster with it.
  927                                  */
  928                                 if (BUF_LOCK(tbp,
  929                                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
  930                                     BO_LOCKPTR(bo)))
  931                                         break;
  932 
  933                                 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
  934                                     B_INVAL | B_DELWRI | B_NEEDCOMMIT))
  935                                     != (B_DELWRI | B_CLUSTEROK |
  936                                     (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
  937                                     tbp->b_wcred != bp->b_wcred) {
  938                                         BUF_UNLOCK(tbp);
  939                                         break;
  940                                 }
  941 
  942                                 /*
  943                                  * Check that the combined cluster
  944                                  * would make sense with regard to pages
  945                                  * and would not be too large
  946                                  */
  947                                 if ((tbp->b_bcount != size) ||
  948                                   ((bp->b_blkno + (dbsize * i)) !=
  949                                     tbp->b_blkno) ||
  950                                   ((tbp->b_npages + bp->b_npages) >
  951                                     (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
  952                                         BUF_UNLOCK(tbp);
  953                                         break;
  954                                 }
  955 
  956                                 /*
  957                                  * Do not pull in pinned buffers.
  958                                  */
  959                                 if (tbp->b_pin_count > 0) {
  960                                         BUF_UNLOCK(tbp);
  961                                         break;
  962                                 }
  963 
  964                                 /*
  965                                  * Ok, it's passed all the tests,
  966                                  * so remove it from the free list
  967                                  * and mark it busy. We will use it.
  968                                  */
  969                                 bremfree(tbp);
  970                                 tbp->b_flags &= ~B_DONE;
  971                         } /* end of code for non-first buffers only */
  972                         /*
  973                          * If the IO is via the VM then we do some
  974                          * special VM hackery (yuck).  Since the buffer's
  975                          * block size may not be page-aligned it is possible
  976                          * for a page to be shared between two buffers.  We
  977                          * have to get rid of the duplication when building
  978                          * the cluster.
  979                          */
  980                         if (tbp->b_flags & B_VMIO) {
  981                                 vm_page_t m;
  982 
  983                                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
  984                                 if (i == 0) {
  985                                         vfs_drain_busy_pages(tbp);
  986                                 } else { /* if not first buffer */
  987                                         for (j = 0; j < tbp->b_npages; j += 1) {
  988                                                 m = tbp->b_pages[j];
  989                                                 if (vm_page_xbusied(m)) {
  990                                                         VM_OBJECT_WUNLOCK(
  991                                                             tbp->b_object);
  992                                                         bqrelse(tbp);
  993                                                         goto finishcluster;
  994                                                 }
  995                                         }
  996                                 }
  997                                 for (j = 0; j < tbp->b_npages; j += 1) {
  998                                         m = tbp->b_pages[j];
  999                                         vm_page_sbusy(m);
 1000                                         vm_object_pip_add(m->object, 1);
 1001                                         if ((bp->b_npages == 0) ||
 1002                                           (bp->b_pages[bp->b_npages - 1] != m)) {
 1003                                                 bp->b_pages[bp->b_npages] = m;
 1004                                                 bp->b_npages++;
 1005                                         }
 1006                                 }
 1007                                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 1008                         }
 1009                         bp->b_bcount += size;
 1010                         bp->b_bufsize += size;
 1011                         /*
 1012                          * If any of the clustered buffers have their
 1013                          * B_BARRIER flag set, transfer that request to
 1014                          * the cluster.
 1015                          */
 1016                         bp->b_flags |= (tbp->b_flags & B_BARRIER);
 1017                         tbp->b_flags &= ~(B_DONE | B_BARRIER);
 1018                         tbp->b_flags |= B_ASYNC;
 1019                         tbp->b_ioflags &= ~BIO_ERROR;
 1020                         tbp->b_iocmd = BIO_WRITE;
 1021                         bundirty(tbp);
 1022                         reassignbuf(tbp);               /* put on clean list */
 1023                         bufobj_wref(tbp->b_bufobj);
 1024                         BUF_KERNPROC(tbp);
 1025                         TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
 1026                                 tbp, b_cluster.cluster_entry);
 1027                 }
 1028         finishcluster:
 1029                 if (buf_mapped(bp)) {
 1030                         pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 1031                             (vm_page_t *)bp->b_pages, bp->b_npages);
 1032                 }
 1033                 if (bp->b_bufsize > bp->b_kvasize)
 1034                         panic(
 1035                             "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
 1036                             bp->b_bufsize, bp->b_kvasize);
 1037                 totalwritten += bp->b_bufsize;
 1038                 bp->b_dirtyoff = 0;
 1039                 bp->b_dirtyend = bp->b_bufsize;
 1040                 bawrite(bp);
 1041 
 1042                 len -= i;
 1043         }
 1044         return totalwritten;
 1045 }
 1046 
 1047 /*
 1048  * Collect together all the buffers in a cluster.
 1049  * Plus add one additional buffer.
 1050  */
 1051 static struct cluster_save *
 1052 cluster_collectbufs(struct vnode *vp, struct buf *last_bp, int gbflags)
 1053 {
 1054         struct cluster_save *buflist;
 1055         struct buf *bp;
 1056         daddr_t lbn;
 1057         int i, len;
 1058 
 1059         len = vp->v_lastw - vp->v_cstart + 1;
 1060         buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
 1061             M_SEGMENT, M_WAITOK);
 1062         buflist->bs_nchildren = 0;
 1063         buflist->bs_children = (struct buf **) (buflist + 1);
 1064         for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
 1065                 (void)bread_gb(vp, lbn, last_bp->b_bcount, NOCRED,
 1066                     gbflags, &bp);
 1067                 buflist->bs_children[i] = bp;
 1068                 if (bp->b_blkno == bp->b_lblkno)
 1069                         VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno,
 1070                                 NULL, NULL);
 1071         }
 1072         buflist->bs_children[i] = bp = last_bp;
 1073         if (bp->b_blkno == bp->b_lblkno)
 1074                 VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL);
 1075         buflist->bs_nchildren = i + 1;
 1076         return (buflist);
 1077 }

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