sys/kern/vfs_cluster.c

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