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  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by the University of
  18  *      California, Berkeley and its contributors.
  19  * 4. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  *
  35  *      @(#)vfs_cluster.c       8.7 (Berkeley) 2/13/94
  36  * $FreeBSD: src/sys/kern/vfs_cluster.c,v 1.92.2.9 2001/11/18 07:10:59 dillon Exp $
  37  * $DragonFly: src/sys/kern/vfs_cluster.c,v 1.12 2005/02/19 00:47:03 joerg Exp $
  38  */
  39
  40 #include "opt_debug_cluster.h"
  41
  42 #include <sys/param.h>
  43 #include <sys/systm.h>
  44 #include <sys/kernel.h>
  45 #include <sys/proc.h>
  46 #include <sys/buf.h>
  47 #include <sys/vnode.h>
  48 #include <sys/malloc.h>
  49 #include <sys/mount.h>
  50 #include <sys/resourcevar.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 #include <sys/buf2.h>
  57 #include <vm/vm_page2.h>
  58
  59 #if defined(CLUSTERDEBUG)
  60 #include <sys/sysctl.h>
  61 static int      rcluster= 0;
  62 SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0, "");
  63 #endif
  64
  65 static MALLOC_DEFINE(M_SEGMENT, "cluster_save", "cluster_save buffer");
  66
  67 static struct cluster_save *
  68         cluster_collectbufs (struct vnode *vp, struct buf *last_bp);
  69 static struct buf *
  70         cluster_rbuild (struct vnode *vp, u_quad_t filesize, daddr_t lbn,
  71                             daddr_t blkno, long size, int run, struct buf *fbp);
  72
  73 static int write_behind = 1;
  74 SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0, "");
  75
  76 extern vm_page_t        bogus_page;
  77
  78 extern int cluster_pbuf_freecnt;
  79
  80 /*
  81  * Maximum number of blocks for read-ahead.
  82  */
  83 #define MAXRA 32
  84
  85 /*
  86  * This replaces bread.
  87  */
  88 int
  89 cluster_read(struct vnode *vp, u_quad_t filesize, daddr_t lblkno,
  90         long size, long totread, int seqcount, struct buf **bpp)
  91 {
  92         struct buf *bp, *rbp, *reqbp;
  93         daddr_t blkno, origblkno;
  94         int error, num_ra;
  95         int i;
  96         int maxra, racluster;
  97         long origtotread;
  98
  99         error = 0;
 100
 101         /*
 102          * Try to limit the amount of read-ahead by a few
 103          * ad-hoc parameters.  This needs work!!!
 104          */
 105         racluster = vp->v_mount->mnt_iosize_max / size;
 106         maxra = 2 * racluster + (totread / size);
 107         if (maxra > MAXRA)
 108                 maxra = MAXRA;
 109         if (maxra > nbuf/8)
 110                 maxra = nbuf/8;
 111
 112         /*
 113          * get the requested block
 114          */
 115         *bpp = reqbp = bp = getblk(vp, lblkno, size, 0, 0);
 116         origblkno = lblkno;
 117         origtotread = totread;
 118
 119         /*
 120          * if it is in the cache, then check to see if the reads have been
 121          * sequential.  If they have, then try some read-ahead, otherwise
 122          * back-off on prospective read-aheads.
 123          */
 124         if (bp->b_flags & B_CACHE) {
 125                 if (!seqcount) {
 126                         return 0;
 127                 } else if ((bp->b_flags & B_RAM) == 0) {
 128                         return 0;
 129                 } else {
 130                         int s;
 131                         struct buf *tbp;
 132                         bp->b_flags &= ~B_RAM;
 133                         /*
 134                          * We do the spl here so that there is no window
 135                          * between the incore and the b_usecount increment
 136                          * below.  We opt to keep the spl out of the loop
 137                          * for efficiency.
 138                          */
 139                         s = splbio();
 140                         for (i = 1; i < maxra; i++) {
 141
 142                                 if (!(tbp = incore(vp, lblkno+i))) {
 143                                         break;
 144                                 }
 145
 146                                 /*
 147                                  * Set another read-ahead mark so we know
 148                                  * to check again.
 149                                  */
 150                                 if (((i % racluster) == (racluster - 1)) ||
 151                                         (i == (maxra - 1)))
 152                                         tbp->b_flags |= B_RAM;
 153                         }
 154                         splx(s);
 155                         if (i >= maxra) {
 156                                 return 0;
 157                         }
 158                         lblkno += i;
 159                 }
 160                 reqbp = bp = NULL;
 161         } else {
 162                 off_t firstread = bp->b_offset;
 163
 164                 KASSERT(bp->b_offset != NOOFFSET,
 165                     ("cluster_read: no buffer offset"));
 166                 if (firstread + totread > filesize)
 167                         totread = filesize - firstread;
 168                 if (totread > size) {
 169                         int nblks = 0;
 170                         int ncontigafter;
 171                         while (totread > 0) {
 172                                 nblks++;
 173                                 totread -= size;
 174                         }
 175                         if (nblks == 1)
 176                                 goto single_block_read;
 177                         if (nblks > racluster)
 178                                 nblks = racluster;
 179
 180                         error = VOP_BMAP(vp, lblkno, NULL,
 181                                 &blkno, &ncontigafter, NULL);
 182                         if (error)
 183                                 goto single_block_read;
 184                         if (blkno == -1)
 185                                 goto single_block_read;
 186                         if (ncontigafter == 0)
 187                                 goto single_block_read;
 188                         if (ncontigafter + 1 < nblks)
 189                                 nblks = ncontigafter + 1;
 190
 191                         bp = cluster_rbuild(vp, filesize, lblkno,
 192                                 blkno, size, nblks, bp);
 193                         lblkno += (bp->b_bufsize / size);
 194                 } else {
 195 single_block_read:
 196                         /*
 197                          * if it isn't in the cache, then get a chunk from
 198                          * disk if sequential, otherwise just get the block.
 199                          */
 200                         bp->b_flags |= B_READ | B_RAM;
 201                         lblkno += 1;
 202                 }
 203         }
 204
 205         /*
 206          * if we have been doing sequential I/O, then do some read-ahead
 207          */
 208         rbp = NULL;
 209         if (seqcount && (lblkno < (origblkno + seqcount))) {
 210                 /*
 211                  * we now build the read-ahead buffer if it is desirable.
 212                  */
 213                 if (((u_quad_t)(lblkno + 1) * size) <= filesize &&
 214                     !(error = VOP_BMAP(vp, lblkno, NULL, &blkno, &num_ra, NULL)) &&
 215                     blkno != -1) {
 216                         int nblksread;
 217                         int ntoread = num_ra + 1;
 218                         nblksread = (origtotread + size - 1) / size;
 219                         if (seqcount < nblksread)
 220                                 seqcount = nblksread;
 221                         if (seqcount < ntoread)
 222                                 ntoread = seqcount;
 223                         if (num_ra) {
 224                                 rbp = cluster_rbuild(vp, filesize, lblkno,
 225                                         blkno, size, ntoread, NULL);
 226                         } else {
 227                                 rbp = getblk(vp, lblkno, size, 0, 0);
 228                                 rbp->b_flags |= B_READ | B_ASYNC | B_RAM;
 229                                 rbp->b_blkno = blkno;
 230                         }
 231                 }
 232         }
 233
 234         /*
 235          * handle the synchronous read
 236          */
 237         if (bp) {
 238 #if defined(CLUSTERDEBUG)
 239                 if (rcluster)
 240                         printf("S(%ld,%ld,%d) ",
 241                             (long)bp->b_lblkno, bp->b_bcount, seqcount);
 242 #endif
 243                 if ((bp->b_flags & B_CLUSTER) == 0) {
 244                         vfs_busy_pages(bp, 0);
 245                 }
 246                 bp->b_flags &= ~(B_ERROR|B_INVAL);
 247                 if (bp->b_flags & (B_ASYNC|B_CALL))
 248                         BUF_KERNPROC(bp);
 249                 error = VOP_STRATEGY(vp, bp);
 250         }
 251
 252         /*
 253          * and if we have read-aheads, do them too
 254          */
 255         if (rbp) {
 256                 if (error) {
 257                         rbp->b_flags &= ~(B_ASYNC | B_READ);
 258                         brelse(rbp);
 259                 } else if (rbp->b_flags & B_CACHE) {
 260                         rbp->b_flags &= ~(B_ASYNC | B_READ);
 261                         bqrelse(rbp);
 262                 } else {
 263 #if defined(CLUSTERDEBUG)
 264                         if (rcluster) {
 265                                 if (bp)
 266                                         printf("A+(%ld,%ld,%ld,%d) ",
 267                                             (long)rbp->b_lblkno, rbp->b_bcount,
 268                                             (long)(rbp->b_lblkno - origblkno),
 269                                             seqcount);
 270                                 else
 271                                         printf("A(%ld,%ld,%ld,%d) ",
 272                                             (long)rbp->b_lblkno, rbp->b_bcount,
 273                                             (long)(rbp->b_lblkno - origblkno),
 274                                             seqcount);
 275                         }
 276 #endif
 277
 278                         if ((rbp->b_flags & B_CLUSTER) == 0) {
 279                                 vfs_busy_pages(rbp, 0);
 280                         }
 281                         rbp->b_flags &= ~(B_ERROR|B_INVAL);
 282                         if (rbp->b_flags & (B_ASYNC|B_CALL))
 283                                 BUF_KERNPROC(rbp);
 284                         (void) VOP_STRATEGY(vp, rbp);
 285                 }
 286         }
 287         if (reqbp)
 288                 return (biowait(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(struct vnode *vp, u_quad_t filesize, daddr_t lbn,
 300         daddr_t blkno, long size, int run, struct buf *fbp)
 301 {
 302         struct buf *bp, *tbp;
 303         daddr_t bn;
 304         int i, inc, j;
 305
 306         KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
 307             ("cluster_rbuild: size %ld != filesize %ld\n",
 308             size, vp->v_mount->mnt_stat.f_iosize));
 309
 310         /*
 311          * avoid a division
 312          */
 313         while ((u_quad_t) size * (lbn + run) > filesize) {
 314                 --run;
 315         }
 316
 317         if (fbp) {
 318                 tbp = fbp;
 319                 tbp->b_flags |= B_READ;
 320         } else {
 321                 tbp = getblk(vp, lbn, size, 0, 0);
 322                 if (tbp->b_flags & B_CACHE)
 323                         return tbp;
 324                 tbp->b_flags |= B_ASYNC | B_READ | B_RAM;
 325         }
 326
 327         tbp->b_blkno = blkno;
 328         if( (tbp->b_flags & B_MALLOC) ||
 329                 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
 330                 return tbp;
 331
 332         bp = trypbuf(&cluster_pbuf_freecnt);
 333         if (bp == 0)
 334                 return tbp;
 335
 336         /*
 337          * We are synthesizing a buffer out of vm_page_t's, but
 338          * if the block size is not page aligned then the starting
 339          * address may not be either.  Inherit the b_data offset
 340          * from the original buffer.
 341          */
 342         bp->b_data = (char *)((vm_offset_t)bp->b_data |
 343             ((vm_offset_t)tbp->b_data & PAGE_MASK));
 344         bp->b_flags = B_ASYNC | B_READ | B_CALL | B_CLUSTER | B_VMIO;
 345         bp->b_iodone = cluster_callback;
 346         bp->b_blkno = blkno;
 347         bp->b_lblkno = lbn;
 348         bp->b_offset = tbp->b_offset;
 349         KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
 350         pbgetvp(vp, bp);
 351
 352         TAILQ_INIT(&bp->b_cluster.cluster_head);
 353
 354         bp->b_bcount = 0;
 355         bp->b_bufsize = 0;
 356         bp->b_xio.xio_npages = 0;
 357
 358         inc = btodb(size);
 359         for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
 360                 if (i != 0) {
 361                         if ((bp->b_xio.xio_npages * PAGE_SIZE) +
 362                             round_page(size) > vp->v_mount->mnt_iosize_max) {
 363                                 break;
 364                         }
 365
 366                         /*
 367                          * Shortcut some checks and try to avoid buffers that
 368                          * would block in the lock.  The same checks have to
 369                          * be made again after we officially get the buffer.
 370                          */
 371                         if ((tbp = incore(vp, lbn + i)) != NULL) {
 372                                 if (BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT))
 373                                         break;
 374                                 BUF_UNLOCK(tbp);
 375
 376                                 for (j = 0; j < tbp->b_xio.xio_npages; j++) {
 377                                         if (tbp->b_xio.xio_pages[j]->valid)
 378                                                 break;
 379                                 }
 380
 381                                 if (j != tbp->b_xio.xio_npages)
 382                                         break;
 383
 384                                 if (tbp->b_bcount != size)
 385                                         break;
 386                         }
 387
 388                         tbp = getblk(vp, lbn + i, size, 0, 0);
 389
 390                         /*
 391                          * Stop scanning if the buffer is fuly valid
 392                          * (marked B_CACHE), or locked (may be doing a
 393                          * background write), or if the buffer is not
 394                          * VMIO backed.  The clustering code can only deal
 395                          * with VMIO-backed buffers.
 396                          */
 397                         if ((tbp->b_flags & (B_CACHE|B_LOCKED)) ||
 398                             (tbp->b_flags & B_VMIO) == 0) {
 399                                 bqrelse(tbp);
 400                                 break;
 401                         }
 402
 403                         /*
 404                          * The buffer must be completely invalid in order to
 405                          * take part in the cluster.  If it is partially valid
 406                          * then we stop.
 407                          */
 408                         for (j = 0;j < tbp->b_xio.xio_npages; j++) {
 409                                 if (tbp->b_xio.xio_pages[j]->valid)
 410                                         break;
 411                         }
 412                         if (j != tbp->b_xio.xio_npages) {
 413                                 bqrelse(tbp);
 414                                 break;
 415                         }
 416
 417                         /*
 418                          * Set a read-ahead mark as appropriate
 419                          */
 420                         if ((fbp && (i == 1)) || (i == (run - 1)))
 421                                 tbp->b_flags |= B_RAM;
 422
 423                         /*
 424                          * Set the buffer up for an async read (XXX should
 425                          * we do this only if we do not wind up brelse()ing?).
 426                          * Set the block number if it isn't set, otherwise
 427                          * if it is make sure it matches the block number we
 428                          * expect.
 429                          */
 430                         tbp->b_flags |= B_READ | B_ASYNC;
 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                 for (j = 0; j < tbp->b_xio.xio_npages; j += 1) {
 446                         vm_page_t m;
 447                         m = tbp->b_xio.xio_pages[j];
 448                         vm_page_io_start(m);
 449                         vm_object_pip_add(m->object, 1);
 450                         if ((bp->b_xio.xio_npages == 0) ||
 451                                 (bp->b_xio.xio_pages[bp->b_xio.xio_npages-1] != m)) {
 452                                 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m;
 453                                 bp->b_xio.xio_npages++;
 454                         }
 455                         if ((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL)
 456                                 tbp->b_xio.xio_pages[j] = bogus_page;
 457                 }
 458                 /*
 459                  * XXX shouldn't this be += size for both, like in
 460                  * cluster_wbuild()?
 461                  *
 462                  * Don't inherit tbp->b_bufsize as it may be larger due to
 463                  * a non-page-aligned size.  Instead just aggregate using
 464                  * 'size'.
 465                  */
 466                 if (tbp->b_bcount != size)
 467                     printf("warning: tbp->b_bcount wrong %ld vs %ld\n", tbp->b_bcount, size);
 468                 if (tbp->b_bufsize != size)
 469                     printf("warning: tbp->b_bufsize wrong %ld vs %ld\n", tbp->b_bufsize, size);
 470                 bp->b_bcount += size;
 471                 bp->b_bufsize += size;
 472         }
 473
 474         /*
 475          * Fully valid pages in the cluster are already good and do not need
 476          * to be re-read from disk.  Replace the page with bogus_page
 477          */
 478         for (j = 0; j < bp->b_xio.xio_npages; j++) {
 479                 if ((bp->b_xio.xio_pages[j]->valid & VM_PAGE_BITS_ALL) ==
 480                     VM_PAGE_BITS_ALL) {
 481                         bp->b_xio.xio_pages[j] = bogus_page;
 482                 }
 483         }
 484         if (bp->b_bufsize > bp->b_kvasize)
 485                 panic("cluster_rbuild: b_bufsize(%ld) > b_kvasize(%d)",
 486                     bp->b_bufsize, bp->b_kvasize);
 487         bp->b_kvasize = bp->b_bufsize;
 488
 489         pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 490                 (vm_page_t *)bp->b_xio.xio_pages, bp->b_xio.xio_npages);
 491         return (bp);
 492 }
 493
 494 /*
 495  * Cleanup after a clustered read or write.
 496  * This is complicated by the fact that any of the buffers might have
 497  * extra memory (if there were no empty buffer headers at allocbuf time)
 498  * that we will need to shift around.
 499  */
 500 void
 501 cluster_callback(struct buf *bp)
 502 {
 503         struct buf *nbp, *tbp;
 504         int error = 0;
 505
 506         /*
 507          * Must propogate errors to all the components.
 508          */
 509         if (bp->b_flags & B_ERROR)
 510                 error = bp->b_error;
 511
 512         pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_xio.xio_npages);
 513         /*
 514          * Move memory from the large cluster buffer into the component
 515          * buffers and mark IO as done on these.
 516          */
 517         for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
 518                 tbp; tbp = nbp) {
 519                 nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
 520                 if (error) {
 521                         tbp->b_flags |= B_ERROR;
 522                         tbp->b_error = error;
 523                 } else {
 524                         tbp->b_dirtyoff = tbp->b_dirtyend = 0;
 525                         tbp->b_flags &= ~(B_ERROR|B_INVAL);
 526                         /*
 527                          * XXX the bdwrite()/bqrelse() issued during
 528                          * cluster building clears B_RELBUF (see bqrelse()
 529                          * comment).  If direct I/O was specified, we have
 530                          * to restore it here to allow the buffer and VM
 531                          * to be freed.
 532                          */
 533                         if (tbp->b_flags & B_DIRECT)
 534                                 tbp->b_flags |= B_RELBUF;
 535                 }
 536                 biodone(tbp);
 537         }
 538         relpbuf(bp, &cluster_pbuf_freecnt);
 539 }
 540
 541 /*
 542  *      cluster_wbuild_wb:
 543  *
 544  *      Implement modified write build for cluster.
 545  *
 546  *              write_behind = 0        write behind disabled
 547  *              write_behind = 1        write behind normal (default)
 548  *              write_behind = 2        write behind backed-off
 549  */
 550
 551 static __inline int
 552 cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len)
 553 {
 554         int r = 0;
 555
 556         switch(write_behind) {
 557         case 2:
 558                 if (start_lbn < len)
 559                         break;
 560                 start_lbn -= len;
 561                 /* fall through */
 562         case 1:
 563                 r = cluster_wbuild(vp, size, start_lbn, len);
 564                 /* fall through */
 565         default:
 566                 /* fall through */
 567                 break;
 568         }
 569         return(r);
 570 }
 571
 572 /*
 573  * Do clustered write for FFS.
 574  *
 575  * Three cases:
 576  *      1. Write is not sequential (write asynchronously)
 577  *      Write is sequential:
 578  *      2.      beginning of cluster - begin cluster
 579  *      3.      middle of a cluster - add to cluster
 580  *      4.      end of a cluster - asynchronously write cluster
 581  */
 582 void
 583 cluster_write(struct buf *bp, u_quad_t filesize, int seqcount)
 584 {
 585         struct vnode *vp;
 586         daddr_t lbn;
 587         int maxclen, cursize;
 588         int lblocksize;
 589         int async;
 590
 591         vp = bp->b_vp;
 592         if (vp->v_type == VREG) {
 593                 async = vp->v_mount->mnt_flag & MNT_ASYNC;
 594                 lblocksize = vp->v_mount->mnt_stat.f_iosize;
 595         } else {
 596                 async = 0;
 597                 lblocksize = bp->b_bufsize;
 598         }
 599         lbn = bp->b_lblkno;
 600         KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));
 601
 602         /* Initialize vnode to beginning of file. */
 603         if (lbn == 0)
 604                 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
 605
 606         if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
 607             (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
 608                 maxclen = vp->v_mount->mnt_iosize_max / lblocksize - 1;
 609                 if (vp->v_clen != 0) {
 610                         /*
 611                          * Next block is not sequential.
 612                          *
 613                          * If we are not writing at end of file, the process
 614                          * seeked to another point in the file since its last
 615                          * write, or we have reached our maximum cluster size,
 616                          * then push the previous cluster. Otherwise try
 617                          * reallocating to make it sequential.
 618                          *
 619                          * Change to algorithm: only push previous cluster if
 620                          * it was sequential from the point of view of the
 621                          * seqcount heuristic, otherwise leave the buffer
 622                          * intact so we can potentially optimize the I/O
 623                          * later on in the buf_daemon or update daemon
 624                          * flush.
 625                          */
 626                         cursize = vp->v_lastw - vp->v_cstart + 1;
 627                         if (((u_quad_t) bp->b_offset + lblocksize) != filesize ||
 628                             lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
 629                                 if (!async && seqcount > 0) {
 630                                         cluster_wbuild_wb(vp, lblocksize,
 631                                                 vp->v_cstart, cursize);
 632                                 }
 633                         } else {
 634                                 struct buf **bpp, **endbp;
 635                                 struct cluster_save *buflist;
 636
 637                                 buflist = cluster_collectbufs(vp, bp);
 638                                 endbp = &buflist->bs_children
 639                                     [buflist->bs_nchildren - 1];
 640                                 if (VOP_REALLOCBLKS(vp, buflist)) {
 641                                         /*
 642                                          * Failed, push the previous cluster
 643                                          * if *really* writing sequentially
 644                                          * in the logical file (seqcount > 1),
 645                                          * otherwise delay it in the hopes that
 646                                          * the low level disk driver can
 647                                          * optimize the write ordering.
 648                                          */
 649                                         for (bpp = buflist->bs_children;
 650                                              bpp < endbp; bpp++)
 651                                                 brelse(*bpp);
 652                                         free(buflist, M_SEGMENT);
 653                                         if (seqcount > 1) {
 654                                                 cluster_wbuild_wb(vp,
 655                                                     lblocksize, vp->v_cstart,
 656                                                     cursize);
 657                                         }
 658                                 } else {
 659                                         /*
 660                                          * Succeeded, keep building cluster.
 661                                          */
 662                                         for (bpp = buflist->bs_children;
 663                                              bpp <= endbp; bpp++)
 664                                                 bdwrite(*bpp);
 665                                         free(buflist, M_SEGMENT);
 666                                         vp->v_lastw = lbn;
 667                                         vp->v_lasta = bp->b_blkno;
 668                                         return;
 669                                 }
 670                         }
 671                 }
 672                 /*
 673                  * Consider beginning a cluster. If at end of file, make
 674                  * cluster as large as possible, otherwise find size of
 675                  * existing cluster.
 676                  */
 677                 if ((vp->v_type == VREG) &&
 678                         ((u_quad_t) bp->b_offset + lblocksize) != filesize &&
 679                     (bp->b_blkno == bp->b_lblkno) &&
 680                     (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
 681                      bp->b_blkno == -1)) {
 682                         bawrite(bp);
 683                         vp->v_clen = 0;
 684                         vp->v_lasta = bp->b_blkno;
 685                         vp->v_cstart = lbn + 1;
 686                         vp->v_lastw = lbn;
 687                         return;
 688                 }
 689                 vp->v_clen = maxclen;
 690                 if (!async && maxclen == 0) {   /* I/O not contiguous */
 691                         vp->v_cstart = lbn + 1;
 692                         bawrite(bp);
 693                 } else {        /* Wait for rest of cluster */
 694                         vp->v_cstart = lbn;
 695                         bdwrite(bp);
 696                 }
 697         } else if (lbn == vp->v_cstart + vp->v_clen) {
 698                 /*
 699                  * At end of cluster, write it out if seqcount tells us we
 700                  * are operating sequentially, otherwise let the buf or
 701                  * update daemon handle it.
 702                  */
 703                 bdwrite(bp);
 704                 if (seqcount > 1)
 705                         cluster_wbuild_wb(vp, lblocksize, vp->v_cstart, vp->v_clen + 1);
 706                 vp->v_clen = 0;
 707                 vp->v_cstart = lbn + 1;
 708         } else if (vm_page_count_severe()) {
 709                 /*
 710                  * We are low on memory, get it going NOW
 711                  */
 712                 bawrite(bp);
 713         } else {
 714                 /*
 715                  * In the middle of a cluster, so just delay the I/O for now.
 716                  */
 717                 bdwrite(bp);
 718         }
 719         vp->v_lastw = lbn;
 720         vp->v_lasta = bp->b_blkno;
 721 }
 722
 723
 724 /*
 725  * This is an awful lot like cluster_rbuild...wish they could be combined.
 726  * The last lbn argument is the current block on which I/O is being
 727  * performed.  Check to see that it doesn't fall in the middle of
 728  * the current block (if last_bp == NULL).
 729  */
 730 int
 731 cluster_wbuild(struct vnode *vp, long size, daddr_t start_lbn, int len)
 732 {
 733         struct buf *bp, *tbp;
 734         int i, j, s;
 735         int totalwritten = 0;
 736         int dbsize = btodb(size);
 737
 738         while (len > 0) {
 739                 s = splbio();
 740                 /*
 741                  * If the buffer is not delayed-write (i.e. dirty), or it
 742                  * is delayed-write but either locked or inval, it cannot
 743                  * partake in the clustered write.
 744                  */
 745                 if (((tbp = gbincore(vp, start_lbn)) == NULL) ||
 746                   ((tbp->b_flags & (B_LOCKED | B_INVAL | B_DELWRI)) != B_DELWRI) ||
 747                   BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT)) {
 748                         ++start_lbn;
 749                         --len;
 750                         splx(s);
 751                         continue;
 752                 }
 753                 bremfree(tbp);
 754                 tbp->b_flags &= ~B_DONE;
 755                 splx(s);
 756
 757                 /*
 758                  * Extra memory in the buffer, punt on this buffer.
 759                  * XXX we could handle this in most cases, but we would
 760                  * have to push the extra memory down to after our max
 761                  * possible cluster size and then potentially pull it back
 762                  * up if the cluster was terminated prematurely--too much
 763                  * hassle.
 764                  */
 765                 if (((tbp->b_flags & (B_CLUSTEROK|B_MALLOC)) != B_CLUSTEROK) ||
 766                   (tbp->b_bcount != tbp->b_bufsize) ||
 767                   (tbp->b_bcount != size) ||
 768                   (len == 1) ||
 769                   ((bp = getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
 770                         totalwritten += tbp->b_bufsize;
 771                         bawrite(tbp);
 772                         ++start_lbn;
 773                         --len;
 774                         continue;
 775                 }
 776
 777                 /*
 778                  * We got a pbuf to make the cluster in.
 779                  * so initialise it.
 780                  */
 781                 TAILQ_INIT(&bp->b_cluster.cluster_head);
 782                 bp->b_bcount = 0;
 783                 bp->b_bufsize = 0;
 784                 bp->b_xio.xio_npages = 0;
 785                 bp->b_blkno = tbp->b_blkno;
 786                 bp->b_lblkno = tbp->b_lblkno;
 787                 bp->b_offset = tbp->b_offset;
 788
 789                 /*
 790                  * We are synthesizing a buffer out of vm_page_t's, but
 791                  * if the block size is not page aligned then the starting
 792                  * address may not be either.  Inherit the b_data offset
 793                  * from the original buffer.
 794                  */
 795                 bp->b_data = (char *)((vm_offset_t)bp->b_data |
 796                     ((vm_offset_t)tbp->b_data & PAGE_MASK));
 797                 bp->b_flags |= B_CALL | B_CLUSTER |
 798                         (tbp->b_flags & (B_VMIO | B_NEEDCOMMIT | B_NOWDRAIN));
 799                 bp->b_iodone = cluster_callback;
 800                 pbgetvp(vp, bp);
 801                 /*
 802                  * From this location in the file, scan forward to see
 803                  * if there are buffers with adjacent data that need to
 804                  * be written as well.
 805                  */
 806                 for (i = 0; i < len; ++i, ++start_lbn) {
 807                         if (i != 0) { /* If not the first buffer */
 808                                 s = splbio();
 809                                 /*
 810                                  * If the adjacent data is not even in core it
 811                                  * can't need to be written.
 812                                  */
 813                                 if ((tbp = gbincore(vp, start_lbn)) == NULL) {
 814                                         splx(s);
 815                                         break;
 816                                 }
 817
 818                                 /*
 819                                  * If it IS in core, but has different
 820                                  * characteristics, or is locked (which
 821                                  * means it could be undergoing a background
 822                                  * I/O or be in a weird state), then don't
 823                                  * cluster with it.
 824                                  */
 825                                 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
 826                                     B_INVAL | B_DELWRI | B_NEEDCOMMIT))
 827                                   != (B_DELWRI | B_CLUSTEROK |
 828                                     (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
 829                                     (tbp->b_flags & B_LOCKED) ||
 830                                     BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT)) {
 831                                         splx(s);
 832                                         break;
 833                                 }
 834
 835                                 /*
 836                                  * Check that the combined cluster
 837                                  * would make sense with regard to pages
 838                                  * and would not be too large
 839                                  */
 840                                 if ((tbp->b_bcount != size) ||
 841                                   ((bp->b_blkno + (dbsize * i)) !=
 842                                     tbp->b_blkno) ||
 843                                   ((tbp->b_xio.xio_npages + bp->b_xio.xio_npages) >
 844                                     (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
 845                                         BUF_UNLOCK(tbp);
 846                                         splx(s);
 847                                         break;
 848                                 }
 849                                 /*
 850                                  * Ok, it's passed all the tests,
 851                                  * so remove it from the free list
 852                                  * and mark it busy. We will use it.
 853                                  */
 854                                 bremfree(tbp);
 855                                 tbp->b_flags &= ~B_DONE;
 856                                 splx(s);
 857                         } /* end of code for non-first buffers only */
 858                         /* check for latent dependencies to be handled */
 859                         if ((LIST_FIRST(&tbp->b_dep)) != NULL &&
 860                             bioops.io_start)
 861                                 (*bioops.io_start)(tbp);
 862                         /*
 863                          * If the IO is via the VM then we do some
 864                          * special VM hackery (yuck).  Since the buffer's
 865                          * block size may not be page-aligned it is possible
 866                          * for a page to be shared between two buffers.  We
 867                          * have to get rid of the duplication when building
 868                          * the cluster.
 869                          */
 870                         if (tbp->b_flags & B_VMIO) {
 871                                 vm_page_t m;
 872
 873                                 if (i != 0) { /* if not first buffer */
 874                                         for (j = 0; j < tbp->b_xio.xio_npages; j += 1) {
 875                                                 m = tbp->b_xio.xio_pages[j];
 876                                                 if (m->flags & PG_BUSY) {
 877                                                         bqrelse(tbp);
 878                                                         goto finishcluster;
 879                                                 }
 880                                         }
 881                                 }
 882
 883                                 for (j = 0; j < tbp->b_xio.xio_npages; j += 1) {
 884                                         m = tbp->b_xio.xio_pages[j];
 885                                         vm_page_io_start(m);
 886                                         vm_object_pip_add(m->object, 1);
 887                                         if ((bp->b_xio.xio_npages == 0) ||
 888                                           (bp->b_xio.xio_pages[bp->b_xio.xio_npages - 1] != m)) {
 889                                                 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m;
 890                                                 bp->b_xio.xio_npages++;
 891                                         }
 892                                 }
 893                         }
 894                         bp->b_bcount += size;
 895                         bp->b_bufsize += size;
 896
 897                         s = splbio();
 898                         bundirty(tbp);
 899                         tbp->b_flags &= ~(B_READ | B_DONE | B_ERROR);
 900                         tbp->b_flags |= B_ASYNC;
 901                         reassignbuf(tbp, tbp->b_vp);    /* put on clean list */
 902                         ++tbp->b_vp->v_numoutput;
 903                         splx(s);
 904                         BUF_KERNPROC(tbp);
 905                         TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
 906                                 tbp, b_cluster.cluster_entry);
 907                 }
 908         finishcluster:
 909                 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 910                         (vm_page_t *) bp->b_xio.xio_pages, bp->b_xio.xio_npages);
 911                 if (bp->b_bufsize > bp->b_kvasize)
 912                         panic(
 913                             "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
 914                             bp->b_bufsize, bp->b_kvasize);
 915                 bp->b_kvasize = bp->b_bufsize;
 916                 totalwritten += bp->b_bufsize;
 917                 bp->b_dirtyoff = 0;
 918                 bp->b_dirtyend = bp->b_bufsize;
 919                 bawrite(bp);
 920
 921                 len -= i;
 922         }
 923         return totalwritten;
 924 }
 925
 926 /*
 927  * Collect together all the buffers in a cluster.
 928  * Plus add one additional buffer.
 929  */
 930 static struct cluster_save *
 931 cluster_collectbufs(struct vnode *vp, struct buf *last_bp)
 932 {
 933         struct cluster_save *buflist;
 934         struct buf *bp;
 935         daddr_t lbn;
 936         int i, len;
 937
 938         len = vp->v_lastw - vp->v_cstart + 1;
 939         buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
 940             M_SEGMENT, M_WAITOK);
 941         buflist->bs_nchildren = 0;
 942         buflist->bs_children = (struct buf **) (buflist + 1);
 943         for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
 944                 (void) bread(vp, lbn, last_bp->b_bcount, &bp);
 945                 buflist->bs_children[i] = bp;
 946                 if (bp->b_blkno == bp->b_lblkno)
 947                         VOP_BMAP(bp->b_vp, bp->b_lblkno, NULL, &bp->b_blkno,
 948                                 NULL, NULL);
 949         }
 950         buflist->bs_children[i] = bp = last_bp;
 951         if (bp->b_blkno == bp->b_lblkno)
 952                 VOP_BMAP(bp->b_vp, bp->b_lblkno, NULL, &bp->b_blkno,
 953                         NULL, NULL);
 954         buflist->bs_nchildren = i + 1;
 955         return (buflist);
 956 }