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