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