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