sys/kern/vfs_cluster.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  * Modifications/enhancements:
   7  *      Copyright (c) 1995 John S. Dyson.  All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  *      @(#)vfs_cluster.c       8.7 (Berkeley) 2/13/94
  34  */
  35
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD$");
  38
  39 #include "opt_debug_cluster.h"
  40
  41 #include <sys/param.h>
  42 #include <sys/systm.h>
  43 #include <sys/kernel.h>
  44 #include <sys/proc.h>
  45 #include <sys/bio.h>
  46 #include <sys/buf.h>
  47 #include <sys/vnode.h>
  48 #include <sys/malloc.h>
  49 #include <sys/mount.h>
  50 #include <sys/racct.h>
  51 #include <sys/resourcevar.h>
  52 #include <sys/rwlock.h>
  53 #include <sys/vmmeter.h>
  54 #include <vm/vm.h>
  55 #include <vm/vm_object.h>
  56 #include <vm/vm_page.h>
  57 #include <sys/sysctl.h>
  58
  59 #if defined(CLUSTERDEBUG)
  60 static int      rcluster= 0;
  61 SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0,
  62     "Debug VFS clustering code");
  63 #endif
  64
  65 static MALLOC_DEFINE(M_SEGMENT, "cl_savebuf", "cluster_save buffer");
  66
  67 static struct cluster_save *cluster_collectbufs(struct vnode *vp,
  68             struct buf *last_bp, int gbflags);
  69 static struct buf *cluster_rbuild(struct vnode *vp, u_quad_t filesize,
  70             daddr_t lbn, daddr_t blkno, long size, int run, int gbflags,
  71             struct buf *fbp);
  72 static void cluster_callback(struct buf *);
  73
  74 static int write_behind = 1;
  75 SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0,
  76     "Cluster write-behind; 0: disable, 1: enable, 2: backed off");
  77
  78 static int read_max = 64;
  79 SYSCTL_INT(_vfs, OID_AUTO, read_max, CTLFLAG_RW, &read_max, 0,
  80     "Cluster read-ahead max block count");
  81
  82 static int read_min = 1;
  83 SYSCTL_INT(_vfs, OID_AUTO, read_min, CTLFLAG_RW, &read_min, 0,
  84     "Cluster read min block count");
  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         struct thread *td;
  98         daddr_t blkno, origblkno;
  99         int maxra, racluster;
 100         int error, ncontig;
 101         int i;
 102
 103         error = 0;
 104         td = curthread;
 105         bo = &vp->v_bufobj;
 106         if (!unmapped_buf_allowed)
 107                 gbflags &= ~GB_UNMAPPED;
 108
 109         /*
 110          * Try to limit the amount of read-ahead by a few
 111          * ad-hoc parameters.  This needs work!!!
 112          */
 113         racluster = vp->v_mount->mnt_iosize_max / size;
 114         maxra = seqcount;
 115         maxra = min(read_max, maxra);
 116         maxra = min(nbuf/8, maxra);
 117         if (((u_quad_t)(lblkno + maxra + 1) * size) > filesize)
 118                 maxra = (filesize / size) - lblkno;
 119
 120         /*
 121          * get the requested block
 122          */
 123         error = getblkx(vp, lblkno, size, 0, 0, gbflags, &bp);
 124         if (error != 0) {
 125                 *bpp = NULL;
 126                 return (error);
 127         }
 128         gbflags &= ~GB_NOSPARSE;
 129         origblkno = lblkno;
 130         *bpp = reqbp = bp;
 131
 132         /*
 133          * if it is in the cache, then check to see if the reads have been
 134          * sequential.  If they have, then try some read-ahead, otherwise
 135          * back-off on prospective read-aheads.
 136          */
 137         if (bp->b_flags & B_CACHE) {
 138                 if (!seqcount) {
 139                         return 0;
 140                 } else if ((bp->b_flags & B_RAM) == 0) {
 141                         return 0;
 142                 } else {
 143                         bp->b_flags &= ~B_RAM;
 144                         BO_RLOCK(bo);
 145                         for (i = 1; i < maxra; i++) {
 146                                 /*
 147                                  * Stop if the buffer does not exist or it
 148                                  * is invalid (about to go away?)
 149                                  */
 150                                 rbp = gbincore(&vp->v_bufobj, lblkno+i);
 151                                 if (rbp == NULL || (rbp->b_flags & B_INVAL))
 152                                         break;
 153
 154                                 /*
 155                                  * Set another read-ahead mark so we know
 156                                  * to check again. (If we can lock the
 157                                  * buffer without waiting)
 158                                  */
 159                                 if ((((i % racluster) == (racluster - 1)) ||
 160                                     (i == (maxra - 1)))
 161                                     && (0 == BUF_LOCK(rbp,
 162                                         LK_EXCLUSIVE | LK_NOWAIT, NULL))) {
 163                                         rbp->b_flags |= B_RAM;
 164                                         BUF_UNLOCK(rbp);
 165                                 }
 166                         }
 167                         BO_RUNLOCK(bo);
 168                         if (i >= maxra) {
 169                                 return 0;
 170                         }
 171                         lblkno += i;
 172                 }
 173                 reqbp = bp = NULL;
 174         /*
 175          * If it isn't in the cache, then get a chunk from
 176          * disk if sequential, otherwise just get the block.
 177          */
 178         } else {
 179                 off_t firstread = bp->b_offset;
 180                 int nblks;
 181                 long minread;
 182
 183                 KASSERT(bp->b_offset != NOOFFSET,
 184                     ("cluster_read: no buffer offset"));
 185
 186                 ncontig = 0;
 187
 188                 /*
 189                  * Adjust totread if needed
 190                  */
 191                 minread = read_min * size;
 192                 if (minread > totread)
 193                         totread = minread;
 194
 195                 /*
 196                  * Compute the total number of blocks that we should read
 197                  * synchronously.
 198                  */
 199                 if (firstread + totread > filesize)
 200                         totread = filesize - firstread;
 201                 nblks = howmany(totread, size);
 202                 if (nblks > racluster)
 203                         nblks = racluster;
 204
 205                 /*
 206                  * Now compute the number of contiguous blocks.
 207                  */
 208                 if (nblks > 1) {
 209                         error = VOP_BMAP(vp, lblkno, NULL,
 210                                 &blkno, &ncontig, NULL);
 211                         /*
 212                          * If this failed to map just do the original block.
 213                          */
 214                         if (error || blkno == -1)
 215                                 ncontig = 0;
 216                 }
 217
 218                 /*
 219                  * If we have contiguous data available do a cluster
 220                  * otherwise just read the requested block.
 221                  */
 222                 if (ncontig) {
 223                         /* Account for our first block. */
 224                         ncontig = min(ncontig + 1, nblks);
 225                         if (ncontig < nblks)
 226                                 nblks = ncontig;
 227                         bp = cluster_rbuild(vp, filesize, lblkno,
 228                             blkno, size, nblks, gbflags, bp);
 229                         lblkno += (bp->b_bufsize / size);
 230                 } else {
 231                         bp->b_flags |= B_RAM;
 232                         bp->b_iocmd = BIO_READ;
 233                         lblkno += 1;
 234                 }
 235         }
 236
 237         /*
 238          * handle the synchronous read so that it is available ASAP.
 239          */
 240         if (bp) {
 241                 if ((bp->b_flags & B_CLUSTER) == 0) {
 242                         vfs_busy_pages(bp, 0);
 243                 }
 244                 bp->b_flags &= ~B_INVAL;
 245                 bp->b_ioflags &= ~BIO_ERROR;
 246                 if ((bp->b_flags & B_ASYNC) || bp->b_iodone != NULL)
 247                         BUF_KERNPROC(bp);
 248                 bp->b_iooffset = dbtob(bp->b_blkno);
 249                 bstrategy(bp);
 250 #ifdef RACCT
 251                 if (racct_enable) {
 252                         PROC_LOCK(td->td_proc);
 253                         racct_add_buf(td->td_proc, bp, 0);
 254                         PROC_UNLOCK(td->td_proc);
 255                 }
 256 #endif /* RACCT */
 257                 td->td_ru.ru_inblock++;
 258         }
 259
 260         /*
 261          * If we have been doing sequential I/O, then do some read-ahead.
 262          */
 263         while (lblkno < (origblkno + maxra)) {
 264                 error = VOP_BMAP(vp, lblkno, NULL, &blkno, &ncontig, NULL);
 265                 if (error)
 266                         break;
 267
 268                 if (blkno == -1)
 269                         break;
 270
 271                 /*
 272                  * We could throttle ncontig here by maxra but we might as
 273                  * well read the data if it is contiguous.  We're throttled
 274                  * by racluster anyway.
 275                  */
 276                 if (ncontig) {
 277                         ncontig = min(ncontig + 1, racluster);
 278                         rbp = cluster_rbuild(vp, filesize, lblkno, blkno,
 279                             size, ncontig, gbflags, NULL);
 280                         lblkno += (rbp->b_bufsize / size);
 281                         if (rbp->b_flags & B_DELWRI) {
 282                                 bqrelse(rbp);
 283                                 continue;
 284                         }
 285                 } else {
 286                         rbp = getblk(vp, lblkno, size, 0, 0, gbflags);
 287                         lblkno += 1;
 288                         if (rbp->b_flags & B_DELWRI) {
 289                                 bqrelse(rbp);
 290                                 continue;
 291                         }
 292                         rbp->b_flags |= B_ASYNC | B_RAM;
 293                         rbp->b_iocmd = BIO_READ;
 294                         rbp->b_blkno = blkno;
 295                 }
 296                 if (rbp->b_flags & B_CACHE) {
 297                         rbp->b_flags &= ~B_ASYNC;
 298                         bqrelse(rbp);
 299                         continue;
 300                 }
 301                 if ((rbp->b_flags & B_CLUSTER) == 0) {
 302                         vfs_busy_pages(rbp, 0);
 303                 }
 304                 rbp->b_flags &= ~B_INVAL;
 305                 rbp->b_ioflags &= ~BIO_ERROR;
 306                 if ((rbp->b_flags & B_ASYNC) || rbp->b_iodone != NULL)
 307                         BUF_KERNPROC(rbp);
 308                 rbp->b_iooffset = dbtob(rbp->b_blkno);
 309                 bstrategy(rbp);
 310 #ifdef RACCT
 311                 if (racct_enable) {
 312                         PROC_LOCK(td->td_proc);
 313                         racct_add_buf(td->td_proc, rbp, 0);
 314                         PROC_UNLOCK(td->td_proc);
 315                 }
 316 #endif /* RACCT */
 317                 td->td_ru.ru_inblock++;
 318         }
 319
 320         if (reqbp) {
 321                 /*
 322                  * Like bread, always brelse() the buffer when
 323                  * returning an error.
 324                  */
 325                 error = bufwait(reqbp);
 326                 if (error != 0) {
 327                         brelse(reqbp);
 328                         *bpp = NULL;
 329                 }
 330         }
 331         return (error);
 332 }
 333
 334 /*
 335  * If blocks are contiguous on disk, use this to provide clustered
 336  * read ahead.  We will read as many blocks as possible sequentially
 337  * and then parcel them up into logical blocks in the buffer hash table.
 338  */
 339 static struct buf *
 340 cluster_rbuild(struct vnode *vp, u_quad_t filesize, daddr_t lbn,
 341     daddr_t blkno, long size, int run, int gbflags, struct buf *fbp)
 342 {
 343         struct buf *bp, *tbp;
 344         daddr_t bn;
 345         off_t off;
 346         long tinc, tsize;
 347         int i, inc, j, k, toff;
 348
 349         KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
 350             ("cluster_rbuild: size %ld != f_iosize %jd\n",
 351             size, (intmax_t)vp->v_mount->mnt_stat.f_iosize));
 352
 353         /*
 354          * avoid a division
 355          */
 356         while ((u_quad_t) size * (lbn + run) > filesize) {
 357                 --run;
 358         }
 359
 360         if (fbp) {
 361                 tbp = fbp;
 362                 tbp->b_iocmd = BIO_READ;
 363         } else {
 364                 tbp = getblk(vp, lbn, size, 0, 0, gbflags);
 365                 if (tbp->b_flags & B_CACHE)
 366                         return tbp;
 367                 tbp->b_flags |= B_ASYNC | B_RAM;
 368                 tbp->b_iocmd = BIO_READ;
 369         }
 370         tbp->b_blkno = blkno;
 371         if( (tbp->b_flags & B_MALLOC) ||
 372                 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
 373                 return tbp;
 374
 375         bp = trypbuf(&cluster_pbuf_freecnt);
 376         if (bp == NULL)
 377                 return tbp;
 378
 379         /*
 380          * We are synthesizing a buffer out of vm_page_t's, but
 381          * if the block size is not page aligned then the starting
 382          * address may not be either.  Inherit the b_data offset
 383          * from the original buffer.
 384          */
 385         bp->b_flags = B_ASYNC | B_CLUSTER | B_VMIO;
 386         if ((gbflags & GB_UNMAPPED) != 0) {
 387                 bp->b_data = unmapped_buf;
 388         } else {
 389                 bp->b_data = (char *)((vm_offset_t)bp->b_data |
 390                     ((vm_offset_t)tbp->b_data & PAGE_MASK));
 391         }
 392         bp->b_iocmd = BIO_READ;
 393         bp->b_iodone = cluster_callback;
 394         bp->b_blkno = blkno;
 395         bp->b_lblkno = lbn;
 396         bp->b_offset = tbp->b_offset;
 397         KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
 398         pbgetvp(vp, bp);
 399
 400         TAILQ_INIT(&bp->b_cluster.cluster_head);
 401
 402         bp->b_bcount = 0;
 403         bp->b_bufsize = 0;
 404         bp->b_npages = 0;
 405
 406         inc = btodb(size);
 407         for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
 408                 if (i == 0) {
 409                         VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 410                         vfs_drain_busy_pages(tbp);
 411                         vm_object_pip_add(tbp->b_bufobj->bo_object,
 412                             tbp->b_npages);
 413                         for (k = 0; k < tbp->b_npages; k++)
 414                                 vm_page_sbusy(tbp->b_pages[k]);
 415                         VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 416                 } else {
 417                         if ((bp->b_npages * PAGE_SIZE) +
 418                             round_page(size) > vp->v_mount->mnt_iosize_max) {
 419                                 break;
 420                         }
 421
 422                         tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT |
 423                             (gbflags & GB_UNMAPPED));
 424
 425                         /* Don't wait around for locked bufs. */
 426                         if (tbp == NULL)
 427                                 break;
 428
 429                         /*
 430                          * Stop scanning if the buffer is fully valid
 431                          * (marked B_CACHE), or locked (may be doing a
 432                          * background write), or if the buffer is not
 433                          * VMIO backed.  The clustering code can only deal
 434                          * with VMIO-backed buffers.  The bo lock is not
 435                          * required for the BKGRDINPROG check since it
 436                          * can not be set without the buf lock.
 437                          */
 438                         if ((tbp->b_vflags & BV_BKGRDINPROG) ||
 439                             (tbp->b_flags & B_CACHE) ||
 440                             (tbp->b_flags & B_VMIO) == 0) {
 441                                 bqrelse(tbp);
 442                                 break;
 443                         }
 444
 445                         /*
 446                          * The buffer must be completely invalid in order to
 447                          * take part in the cluster.  If it is partially valid
 448                          * then we stop.
 449                          */
 450                         off = tbp->b_offset;
 451                         tsize = size;
 452                         VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 453                         for (j = 0; tsize > 0; j++) {
 454                                 toff = off & PAGE_MASK;
 455                                 tinc = tsize;
 456                                 if (toff + tinc > PAGE_SIZE)
 457                                         tinc = PAGE_SIZE - toff;
 458                                 VM_OBJECT_ASSERT_WLOCKED(tbp->b_pages[j]->object);
 459                                 if ((tbp->b_pages[j]->valid &
 460                                     vm_page_bits(toff, tinc)) != 0)
 461                                         break;
 462                                 if (vm_page_xbusied(tbp->b_pages[j]))
 463                                         break;
 464                                 vm_object_pip_add(tbp->b_bufobj->bo_object, 1);
 465                                 vm_page_sbusy(tbp->b_pages[j]);
 466                                 off += tinc;
 467                                 tsize -= tinc;
 468                         }
 469                         if (tsize > 0) {
 470 clean_sbusy:
 471                                 vm_object_pip_add(tbp->b_bufobj->bo_object, -j);
 472                                 for (k = 0; k < j; k++)
 473                                         vm_page_sunbusy(tbp->b_pages[k]);
 474                                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 475                                 bqrelse(tbp);
 476                                 break;
 477                         }
 478                         VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 479
 480                         /*
 481                          * Set a read-ahead mark as appropriate
 482                          */
 483                         if ((fbp && (i == 1)) || (i == (run - 1)))
 484                                 tbp->b_flags |= B_RAM;
 485
 486                         /*
 487                          * Set the buffer up for an async read (XXX should
 488                          * we do this only if we do not wind up brelse()ing?).
 489                          * Set the block number if it isn't set, otherwise
 490                          * if it is make sure it matches the block number we
 491                          * expect.
 492                          */
 493                         tbp->b_flags |= B_ASYNC;
 494                         tbp->b_iocmd = BIO_READ;
 495                         if (tbp->b_blkno == tbp->b_lblkno) {
 496                                 tbp->b_blkno = bn;
 497                         } else if (tbp->b_blkno != bn) {
 498                                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 499                                 goto clean_sbusy;
 500                         }
 501                 }
 502                 /*
 503                  * XXX fbp from caller may not be B_ASYNC, but we are going
 504                  * to biodone() it in cluster_callback() anyway
 505                  */
 506                 BUF_KERNPROC(tbp);
 507                 TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
 508                         tbp, b_cluster.cluster_entry);
 509                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 510                 for (j = 0; j < tbp->b_npages; j += 1) {
 511                         vm_page_t m;
 512                         m = tbp->b_pages[j];
 513                         if ((bp->b_npages == 0) ||
 514                             (bp->b_pages[bp->b_npages-1] != m)) {
 515                                 bp->b_pages[bp->b_npages] = m;
 516                                 bp->b_npages++;
 517                         }
 518                         if (m->valid == VM_PAGE_BITS_ALL)
 519                                 tbp->b_pages[j] = bogus_page;
 520                 }
 521                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 522                 /*
 523                  * Don't inherit tbp->b_bufsize as it may be larger due to
 524                  * a non-page-aligned size.  Instead just aggregate using
 525                  * 'size'.
 526                  */
 527                 if (tbp->b_bcount != size)
 528                         printf("warning: tbp->b_bcount wrong %ld vs %ld\n", tbp->b_bcount, size);
 529                 if (tbp->b_bufsize != size)
 530                         printf("warning: tbp->b_bufsize wrong %ld vs %ld\n", tbp->b_bufsize, size);
 531                 bp->b_bcount += size;
 532                 bp->b_bufsize += size;
 533         }
 534
 535         /*
 536          * Fully valid pages in the cluster are already good and do not need
 537          * to be re-read from disk.  Replace the page with bogus_page
 538          */
 539         VM_OBJECT_WLOCK(bp->b_bufobj->bo_object);
 540         for (j = 0; j < bp->b_npages; j++) {
 541                 VM_OBJECT_ASSERT_WLOCKED(bp->b_pages[j]->object);
 542                 if (bp->b_pages[j]->valid == VM_PAGE_BITS_ALL)
 543                         bp->b_pages[j] = bogus_page;
 544         }
 545         VM_OBJECT_WUNLOCK(bp->b_bufobj->bo_object);
 546         if (bp->b_bufsize > bp->b_kvasize)
 547                 panic("cluster_rbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
 548                     bp->b_bufsize, bp->b_kvasize);
 549
 550         if (buf_mapped(bp)) {
 551                 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 552                     (vm_page_t *)bp->b_pages, bp->b_npages);
 553         }
 554         return (bp);
 555 }
 556
 557 /*
 558  * Cleanup after a clustered read or write.
 559  * This is complicated by the fact that any of the buffers might have
 560  * extra memory (if there were no empty buffer headers at allocbuf time)
 561  * that we will need to shift around.
 562  */
 563 static void
 564 cluster_callback(struct buf *bp)
 565 {
 566         struct buf *nbp, *tbp;
 567         int error = 0;
 568
 569         /*
 570          * Must propagate errors to all the components.
 571          */
 572         if (bp->b_ioflags & BIO_ERROR)
 573                 error = bp->b_error;
 574
 575         if (buf_mapped(bp)) {
 576                 pmap_qremove(trunc_page((vm_offset_t) bp->b_data),
 577                     bp->b_npages);
 578         }
 579         /*
 580          * Move memory from the large cluster buffer into the component
 581          * buffers and mark IO as done on these.
 582          */
 583         for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
 584                 tbp; tbp = nbp) {
 585                 nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
 586                 if (error) {
 587                         tbp->b_ioflags |= BIO_ERROR;
 588                         tbp->b_error = error;
 589                 } else {
 590                         tbp->b_dirtyoff = tbp->b_dirtyend = 0;
 591                         tbp->b_flags &= ~B_INVAL;
 592                         tbp->b_ioflags &= ~BIO_ERROR;
 593                         /*
 594                          * XXX the bdwrite()/bqrelse() issued during
 595                          * cluster building clears B_RELBUF (see bqrelse()
 596                          * comment).  If direct I/O was specified, we have
 597                          * to restore it here to allow the buffer and VM
 598                          * to be freed.
 599                          */
 600                         if (tbp->b_flags & B_DIRECT)
 601                                 tbp->b_flags |= B_RELBUF;
 602                 }
 603                 bufdone(tbp);
 604         }
 605         pbrelvp(bp);
 606         relpbuf(bp, &cluster_pbuf_freecnt);
 607 }
 608
 609 /*
 610  *      cluster_wbuild_wb:
 611  *
 612  *      Implement modified write build for cluster.
 613  *
 614  *              write_behind = 0        write behind disabled
 615  *              write_behind = 1        write behind normal (default)
 616  *              write_behind = 2        write behind backed-off
 617  */
 618
 619 static __inline int
 620 cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len,
 621     int gbflags)
 622 {
 623         int r = 0;
 624
 625         switch (write_behind) {
 626         case 2:
 627                 if (start_lbn < len)
 628                         break;
 629                 start_lbn -= len;
 630                 /* FALLTHROUGH */
 631         case 1:
 632                 r = cluster_wbuild(vp, size, start_lbn, len, gbflags);
 633                 /* FALLTHROUGH */
 634         default:
 635                 /* FALLTHROUGH */
 636                 break;
 637         }
 638         return(r);
 639 }
 640
 641 /*
 642  * Do clustered write for FFS.
 643  *
 644  * Three cases:
 645  *      1. Write is not sequential (write asynchronously)
 646  *      Write is sequential:
 647  *      2.      beginning of cluster - begin cluster
 648  *      3.      middle of a cluster - add to cluster
 649  *      4.      end of a cluster - asynchronously write cluster
 650  */
 651 void
 652 cluster_write(struct vnode *vp, struct buf *bp, u_quad_t filesize, int seqcount,
 653     int gbflags)
 654 {
 655         daddr_t lbn;
 656         int maxclen, cursize;
 657         int lblocksize;
 658         int async;
 659
 660         if (!unmapped_buf_allowed)
 661                 gbflags &= ~GB_UNMAPPED;
 662
 663         if (vp->v_type == VREG) {
 664                 async = DOINGASYNC(vp);
 665                 lblocksize = vp->v_mount->mnt_stat.f_iosize;
 666         } else {
 667                 async = 0;
 668                 lblocksize = bp->b_bufsize;
 669         }
 670         lbn = bp->b_lblkno;
 671         KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));
 672
 673         /* Initialize vnode to beginning of file. */
 674         if (lbn == 0)
 675                 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
 676
 677         if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
 678             (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
 679                 maxclen = vp->v_mount->mnt_iosize_max / lblocksize - 1;
 680                 if (vp->v_clen != 0) {
 681                         /*
 682                          * Next block is not sequential.
 683                          *
 684                          * If we are not writing at end of file, the process
 685                          * seeked to another point in the file since its last
 686                          * write, or we have reached our maximum cluster size,
 687                          * then push the previous cluster. Otherwise try
 688                          * reallocating to make it sequential.
 689                          *
 690                          * Change to algorithm: only push previous cluster if
 691                          * it was sequential from the point of view of the
 692                          * seqcount heuristic, otherwise leave the buffer
 693                          * intact so we can potentially optimize the I/O
 694                          * later on in the buf_daemon or update daemon
 695                          * flush.
 696                          */
 697                         cursize = vp->v_lastw - vp->v_cstart + 1;
 698                         if (((u_quad_t) bp->b_offset + lblocksize) != filesize ||
 699                             lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
 700                                 if (!async && seqcount > 0) {
 701                                         cluster_wbuild_wb(vp, lblocksize,
 702                                             vp->v_cstart, cursize, gbflags);
 703                                 }
 704                         } else {
 705                                 struct buf **bpp, **endbp;
 706                                 struct cluster_save *buflist;
 707
 708                                 buflist = cluster_collectbufs(vp, bp, gbflags);
 709                                 endbp = &buflist->bs_children
 710                                     [buflist->bs_nchildren - 1];
 711                                 if (VOP_REALLOCBLKS(vp, buflist)) {
 712                                         /*
 713                                          * Failed, push the previous cluster
 714                                          * if *really* writing sequentially
 715                                          * in the logical file (seqcount > 1),
 716                                          * otherwise delay it in the hopes that
 717                                          * the low level disk driver can
 718                                          * optimize the write ordering.
 719                                          */
 720                                         for (bpp = buflist->bs_children;
 721                                              bpp < endbp; bpp++)
 722                                                 brelse(*bpp);
 723                                         free(buflist, M_SEGMENT);
 724                                         if (seqcount > 1) {
 725                                                 cluster_wbuild_wb(vp,
 726                                                     lblocksize, vp->v_cstart,
 727                                                     cursize, gbflags);
 728                                         }
 729                                 } else {
 730                                         /*
 731                                          * Succeeded, keep building cluster.
 732                                          */
 733                                         for (bpp = buflist->bs_children;
 734                                              bpp <= endbp; bpp++)
 735                                                 bdwrite(*bpp);
 736                                         free(buflist, M_SEGMENT);
 737                                         vp->v_lastw = lbn;
 738                                         vp->v_lasta = bp->b_blkno;
 739                                         return;
 740                                 }
 741                         }
 742                 }
 743                 /*
 744                  * Consider beginning a cluster. If at end of file, make
 745                  * cluster as large as possible, otherwise find size of
 746                  * existing cluster.
 747                  */
 748                 if ((vp->v_type == VREG) &&
 749                         ((u_quad_t) bp->b_offset + lblocksize) != filesize &&
 750                     (bp->b_blkno == bp->b_lblkno) &&
 751                     (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
 752                      bp->b_blkno == -1)) {
 753                         bawrite(bp);
 754                         vp->v_clen = 0;
 755                         vp->v_lasta = bp->b_blkno;
 756                         vp->v_cstart = lbn + 1;
 757                         vp->v_lastw = lbn;
 758                         return;
 759                 }
 760                 vp->v_clen = maxclen;
 761                 if (!async && maxclen == 0) {   /* I/O not contiguous */
 762                         vp->v_cstart = lbn + 1;
 763                         bawrite(bp);
 764                 } else {        /* Wait for rest of cluster */
 765                         vp->v_cstart = lbn;
 766                         bdwrite(bp);
 767                 }
 768         } else if (lbn == vp->v_cstart + vp->v_clen) {
 769                 /*
 770                  * At end of cluster, write it out if seqcount tells us we
 771                  * are operating sequentially, otherwise let the buf or
 772                  * update daemon handle it.
 773                  */
 774                 bdwrite(bp);
 775                 if (seqcount > 1) {
 776                         cluster_wbuild_wb(vp, lblocksize, vp->v_cstart,
 777                             vp->v_clen + 1, gbflags);
 778                 }
 779                 vp->v_clen = 0;
 780                 vp->v_cstart = lbn + 1;
 781         } else if (vm_page_count_severe()) {
 782                 /*
 783                  * We are low on memory, get it going NOW
 784                  */
 785                 bawrite(bp);
 786         } else {
 787                 /*
 788                  * In the middle of a cluster, so just delay the I/O for now.
 789                  */
 790                 bdwrite(bp);
 791         }
 792         vp->v_lastw = lbn;
 793         vp->v_lasta = bp->b_blkno;
 794 }
 795
 796
 797 /*
 798  * This is an awful lot like cluster_rbuild...wish they could be combined.
 799  * The last lbn argument is the current block on which I/O is being
 800  * performed.  Check to see that it doesn't fall in the middle of
 801  * the current block (if last_bp == NULL).
 802  */
 803 int
 804 cluster_wbuild(struct vnode *vp, long size, daddr_t start_lbn, int len,
 805     int gbflags)
 806 {
 807         struct buf *bp, *tbp;
 808         struct bufobj *bo;
 809         int i, j;
 810         int totalwritten = 0;
 811         int dbsize = btodb(size);
 812
 813         if (!unmapped_buf_allowed)
 814                 gbflags &= ~GB_UNMAPPED;
 815
 816         bo = &vp->v_bufobj;
 817         while (len > 0) {
 818                 /*
 819                  * If the buffer is not delayed-write (i.e. dirty), or it
 820                  * is delayed-write but either locked or inval, it cannot
 821                  * partake in the clustered write.
 822                  */
 823                 BO_LOCK(bo);
 824                 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
 825                     (tbp->b_vflags & BV_BKGRDINPROG)) {
 826                         BO_UNLOCK(bo);
 827                         ++start_lbn;
 828                         --len;
 829                         continue;
 830                 }
 831                 if (BUF_LOCK(tbp,
 832                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, BO_LOCKPTR(bo))) {
 833                         ++start_lbn;
 834                         --len;
 835                         continue;
 836                 }
 837                 if ((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) {
 838                         BUF_UNLOCK(tbp);
 839                         ++start_lbn;
 840                         --len;
 841                         continue;
 842                 }
 843                 bremfree(tbp);
 844                 tbp->b_flags &= ~B_DONE;
 845
 846                 /*
 847                  * Extra memory in the buffer, punt on this buffer.
 848                  * XXX we could handle this in most cases, but we would
 849                  * have to push the extra memory down to after our max
 850                  * possible cluster size and then potentially pull it back
 851                  * up if the cluster was terminated prematurely--too much
 852                  * hassle.
 853                  */
 854                 if (((tbp->b_flags & (B_CLUSTEROK | B_MALLOC | B_VMIO)) !=
 855                      (B_CLUSTEROK | B_VMIO)) ||
 856                   (tbp->b_bcount != tbp->b_bufsize) ||
 857                   (tbp->b_bcount != size) ||
 858                   (len == 1) ||
 859                   ((bp = (vp->v_vflag & VV_MD) != 0 ?
 860                   trypbuf(&cluster_pbuf_freecnt) :
 861                   getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
 862                         totalwritten += tbp->b_bufsize;
 863                         bawrite(tbp);
 864                         ++start_lbn;
 865                         --len;
 866                         continue;
 867                 }
 868
 869                 /*
 870                  * We got a pbuf to make the cluster in.
 871                  * so initialise it.
 872                  */
 873                 TAILQ_INIT(&bp->b_cluster.cluster_head);
 874                 bp->b_bcount = 0;
 875                 bp->b_bufsize = 0;
 876                 bp->b_npages = 0;
 877                 if (tbp->b_wcred != NOCRED)
 878                         bp->b_wcred = crhold(tbp->b_wcred);
 879
 880                 bp->b_blkno = tbp->b_blkno;
 881                 bp->b_lblkno = tbp->b_lblkno;
 882                 bp->b_offset = tbp->b_offset;
 883
 884                 /*
 885                  * We are synthesizing a buffer out of vm_page_t's, but
 886                  * if the block size is not page aligned then the starting
 887                  * address may not be either.  Inherit the b_data offset
 888                  * from the original buffer.
 889                  */
 890                 if ((gbflags & GB_UNMAPPED) == 0 ||
 891                     (tbp->b_flags & B_VMIO) == 0) {
 892                         bp->b_data = (char *)((vm_offset_t)bp->b_data |
 893                             ((vm_offset_t)tbp->b_data & PAGE_MASK));
 894                 } else {
 895                         bp->b_data = unmapped_buf;
 896                 }
 897                 bp->b_flags |= B_CLUSTER | (tbp->b_flags & (B_VMIO |
 898                     B_NEEDCOMMIT));
 899                 bp->b_iodone = cluster_callback;
 900                 pbgetvp(vp, bp);
 901                 /*
 902                  * From this location in the file, scan forward to see
 903                  * if there are buffers with adjacent data that need to
 904                  * be written as well.
 905                  */
 906                 for (i = 0; i < len; ++i, ++start_lbn) {
 907                         if (i != 0) { /* If not the first buffer */
 908                                 /*
 909                                  * If the adjacent data is not even in core it
 910                                  * can't need to be written.
 911                                  */
 912                                 BO_LOCK(bo);
 913                                 if ((tbp = gbincore(bo, start_lbn)) == NULL ||
 914                                     (tbp->b_vflags & BV_BKGRDINPROG)) {
 915                                         BO_UNLOCK(bo);
 916                                         break;
 917                                 }
 918
 919                                 /*
 920                                  * If it IS in core, but has different
 921                                  * characteristics, or is locked (which
 922                                  * means it could be undergoing a background
 923                                  * I/O or be in a weird state), then don't
 924                                  * cluster with it.
 925                                  */
 926                                 if (BUF_LOCK(tbp,
 927                                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
 928                                     BO_LOCKPTR(bo)))
 929                                         break;
 930
 931                                 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
 932                                     B_INVAL | B_DELWRI | B_NEEDCOMMIT))
 933                                     != (B_DELWRI | B_CLUSTEROK |
 934                                     (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
 935                                     tbp->b_wcred != bp->b_wcred) {
 936                                         BUF_UNLOCK(tbp);
 937                                         break;
 938                                 }
 939
 940                                 /*
 941                                  * Check that the combined cluster
 942                                  * would make sense with regard to pages
 943                                  * and would not be too large
 944                                  */
 945                                 if ((tbp->b_bcount != size) ||
 946                                   ((bp->b_blkno + (dbsize * i)) !=
 947                                     tbp->b_blkno) ||
 948                                   ((tbp->b_npages + bp->b_npages) >
 949                                     (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
 950                                         BUF_UNLOCK(tbp);
 951                                         break;
 952                                 }
 953
 954                                 /*
 955                                  * Ok, it's passed all the tests,
 956                                  * so remove it from the free list
 957                                  * and mark it busy. We will use it.
 958                                  */
 959                                 bremfree(tbp);
 960                                 tbp->b_flags &= ~B_DONE;
 961                         } /* end of code for non-first buffers only */
 962                         /*
 963                          * If the IO is via the VM then we do some
 964                          * special VM hackery (yuck).  Since the buffer's
 965                          * block size may not be page-aligned it is possible
 966                          * for a page to be shared between two buffers.  We
 967                          * have to get rid of the duplication when building
 968                          * the cluster.
 969                          */
 970                         if (tbp->b_flags & B_VMIO) {
 971                                 vm_page_t m;
 972
 973                                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 974                                 if (i == 0) {
 975                                         vfs_drain_busy_pages(tbp);
 976                                 } else { /* if not first buffer */
 977                                         for (j = 0; j < tbp->b_npages; j += 1) {
 978                                                 m = tbp->b_pages[j];
 979                                                 if (vm_page_xbusied(m)) {
 980                                                         VM_OBJECT_WUNLOCK(
 981                                                             tbp->b_object);
 982                                                         bqrelse(tbp);
 983                                                         goto finishcluster;
 984                                                 }
 985                                         }
 986                                 }
 987                                 for (j = 0; j < tbp->b_npages; j += 1) {
 988                                         m = tbp->b_pages[j];
 989                                         vm_page_sbusy(m);
 990                                         vm_object_pip_add(m->object, 1);
 991                                         if ((bp->b_npages == 0) ||
 992                                           (bp->b_pages[bp->b_npages - 1] != m)) {
 993                                                 bp->b_pages[bp->b_npages] = m;
 994                                                 bp->b_npages++;
 995                                         }
 996                                 }
 997                                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 998                         }
 999                         bp->b_bcount += size;
1000                         bp->b_bufsize += size;
1001                         /*
1002                          * If any of the clustered buffers have their
1003                          * B_BARRIER flag set, transfer that request to
1004                          * the cluster.
1005                          */
1006                         bp->b_flags |= (tbp->b_flags & B_BARRIER);
1007                         tbp->b_flags &= ~(B_DONE | B_BARRIER);
1008                         tbp->b_flags |= B_ASYNC;
1009                         tbp->b_ioflags &= ~BIO_ERROR;
1010                         tbp->b_iocmd = BIO_WRITE;
1011                         bundirty(tbp);
1012                         reassignbuf(tbp);               /* put on clean list */
1013                         bufobj_wref(tbp->b_bufobj);
1014                         BUF_KERNPROC(tbp);
1015                         buf_track(tbp, __func__);
1016                         TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
1017                                 tbp, b_cluster.cluster_entry);
1018                 }
1019         finishcluster:
1020                 if (buf_mapped(bp)) {
1021                         pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
1022                             (vm_page_t *)bp->b_pages, bp->b_npages);
1023                 }
1024                 if (bp->b_bufsize > bp->b_kvasize)
1025                         panic(
1026                             "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
1027                             bp->b_bufsize, bp->b_kvasize);
1028                 totalwritten += bp->b_bufsize;
1029                 bp->b_dirtyoff = 0;
1030                 bp->b_dirtyend = bp->b_bufsize;
1031                 bawrite(bp);
1032
1033                 len -= i;
1034         }
1035         return totalwritten;
1036 }
1037
1038 /*
1039  * Collect together all the buffers in a cluster.
1040  * Plus add one additional buffer.
1041  */
1042 static struct cluster_save *
1043 cluster_collectbufs(struct vnode *vp, struct buf *last_bp, int gbflags)
1044 {
1045         struct cluster_save *buflist;
1046         struct buf *bp;
1047         daddr_t lbn;
1048         int i, len;
1049
1050         len = vp->v_lastw - vp->v_cstart + 1;
1051         buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
1052             M_SEGMENT, M_WAITOK);
1053         buflist->bs_nchildren = 0;
1054         buflist->bs_children = (struct buf **) (buflist + 1);
1055         for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
1056                 (void)bread_gb(vp, lbn, last_bp->b_bcount, NOCRED,
1057                     gbflags, &bp);
1058                 buflist->bs_children[i] = bp;
1059                 if (bp->b_blkno == bp->b_lblkno)
1060                         VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno,
1061                                 NULL, NULL);
1062         }
1063         buflist->bs_children[i] = bp = last_bp;
1064         if (bp->b_blkno == bp->b_lblkno)
1065                 VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL);
1066         buflist->bs_nchildren = i + 1;
1067         return (buflist);
1068 }