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 buf *bp, *tbp;
 314         daddr_t bn;
 315         off_t off;
 316         long tinc, tsize;
 317         int i, inc, j, k, toff;
 318
 319         KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
 320             ("cluster_rbuild: size %ld != f_iosize %jd\n",
 321             size, (intmax_t)vp->v_mount->mnt_stat.f_iosize));
 322
 323         /*
 324          * avoid a division
 325          */
 326         while ((u_quad_t) size * (lbn + run) > filesize) {
 327                 --run;
 328         }
 329
 330         if (fbp) {
 331                 tbp = fbp;
 332                 tbp->b_iocmd = BIO_READ;
 333         } else {
 334                 tbp = getblk(vp, lbn, size, 0, 0, gbflags);
 335                 if (tbp->b_flags & B_CACHE)
 336                         return tbp;
 337                 tbp->b_flags |= B_ASYNC | B_RAM;
 338                 tbp->b_iocmd = BIO_READ;
 339         }
 340         tbp->b_blkno = blkno;
 341         if( (tbp->b_flags & B_MALLOC) ||
 342                 ((tbp->b_flags & B_VMIO) == 0) || (run <= 1) )
 343                 return tbp;
 344
 345         bp = trypbuf(&cluster_pbuf_freecnt);
 346         if (bp == 0)
 347                 return tbp;
 348
 349         /*
 350          * We are synthesizing a buffer out of vm_page_t's, but
 351          * if the block size is not page aligned then the starting
 352          * address may not be either.  Inherit the b_data offset
 353          * from the original buffer.
 354          */
 355         bp->b_flags = B_ASYNC | B_CLUSTER | B_VMIO;
 356         if ((gbflags & GB_UNMAPPED) != 0) {
 357                 bp->b_data = unmapped_buf;
 358         } else {
 359                 bp->b_data = (char *)((vm_offset_t)bp->b_data |
 360                     ((vm_offset_t)tbp->b_data & PAGE_MASK));
 361         }
 362         bp->b_iocmd = BIO_READ;
 363         bp->b_iodone = cluster_callback;
 364         bp->b_blkno = blkno;
 365         bp->b_lblkno = lbn;
 366         bp->b_offset = tbp->b_offset;
 367         KASSERT(bp->b_offset != NOOFFSET, ("cluster_rbuild: no buffer offset"));
 368         pbgetvp(vp, bp);
 369
 370         TAILQ_INIT(&bp->b_cluster.cluster_head);
 371
 372         bp->b_bcount = 0;
 373         bp->b_bufsize = 0;
 374         bp->b_npages = 0;
 375
 376         inc = btodb(size);
 377         for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
 378                 if (i == 0) {
 379                         VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 380                         vfs_drain_busy_pages(tbp);
 381                         vm_object_pip_add(tbp->b_bufobj->bo_object,
 382                             tbp->b_npages);
 383                         for (k = 0; k < tbp->b_npages; k++)
 384                                 vm_page_sbusy(tbp->b_pages[k]);
 385                         VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 386                 } else {
 387                         if ((bp->b_npages * PAGE_SIZE) +
 388                             round_page(size) > vp->v_mount->mnt_iosize_max) {
 389                                 break;
 390                         }
 391
 392                         tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT |
 393                             (gbflags & GB_UNMAPPED));
 394
 395                         /* Don't wait around for locked bufs. */
 396                         if (tbp == NULL)
 397                                 break;
 398
 399                         /*
 400                          * Stop scanning if the buffer is fully valid
 401                          * (marked B_CACHE), or locked (may be doing a
 402                          * background write), or if the buffer is not
 403                          * VMIO backed.  The clustering code can only deal
 404                          * with VMIO-backed buffers.  The bo lock is not
 405                          * required for the BKGRDINPROG check since it
 406                          * can not be set without the buf lock.
 407                          */
 408                         if ((tbp->b_vflags & BV_BKGRDINPROG) ||
 409                             (tbp->b_flags & B_CACHE) ||
 410                             (tbp->b_flags & B_VMIO) == 0) {
 411                                 bqrelse(tbp);
 412                                 break;
 413                         }
 414
 415                         /*
 416                          * The buffer must be completely invalid in order to
 417                          * take part in the cluster.  If it is partially valid
 418                          * then we stop.
 419                          */
 420                         off = tbp->b_offset;
 421                         tsize = size;
 422                         VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 423                         for (j = 0; tsize > 0; j++) {
 424                                 toff = off & PAGE_MASK;
 425                                 tinc = tsize;
 426                                 if (toff + tinc > PAGE_SIZE)
 427                                         tinc = PAGE_SIZE - toff;
 428                                 VM_OBJECT_ASSERT_WLOCKED(tbp->b_pages[j]->object);
 429                                 if ((tbp->b_pages[j]->valid &
 430                                     vm_page_bits(toff, tinc)) != 0)
 431                                         break;
 432                                 if (vm_page_xbusied(tbp->b_pages[j]))
 433                                         break;
 434                                 vm_object_pip_add(tbp->b_bufobj->bo_object, 1);
 435                                 vm_page_sbusy(tbp->b_pages[j]);
 436                                 off += tinc;
 437                                 tsize -= tinc;
 438                         }
 439                         if (tsize > 0) {
 440 clean_sbusy:
 441                                 vm_object_pip_add(tbp->b_bufobj->bo_object, -j);
 442                                 for (k = 0; k < j; k++)
 443                                         vm_page_sunbusy(tbp->b_pages[k]);
 444                                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 445                                 bqrelse(tbp);
 446                                 break;
 447                         }
 448                         VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 449
 450                         /*
 451                          * Set a read-ahead mark as appropriate
 452                          */
 453                         if ((fbp && (i == 1)) || (i == (run - 1)))
 454                                 tbp->b_flags |= B_RAM;
 455
 456                         /*
 457                          * Set the buffer up for an async read (XXX should
 458                          * we do this only if we do not wind up brelse()ing?).
 459                          * Set the block number if it isn't set, otherwise
 460                          * if it is make sure it matches the block number we
 461                          * expect.
 462                          */
 463                         tbp->b_flags |= B_ASYNC;
 464                         tbp->b_iocmd = BIO_READ;
 465                         if (tbp->b_blkno == tbp->b_lblkno) {
 466                                 tbp->b_blkno = bn;
 467                         } else if (tbp->b_blkno != bn) {
 468                                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 469                                 goto clean_sbusy;
 470                         }
 471                 }
 472                 /*
 473                  * XXX fbp from caller may not be B_ASYNC, but we are going
 474                  * to biodone() it in cluster_callback() anyway
 475                  */
 476                 BUF_KERNPROC(tbp);
 477                 TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
 478                         tbp, b_cluster.cluster_entry);
 479                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 480                 for (j = 0; j < tbp->b_npages; j += 1) {
 481                         vm_page_t m;
 482                         m = tbp->b_pages[j];
 483                         if ((bp->b_npages == 0) ||
 484                             (bp->b_pages[bp->b_npages-1] != m)) {
 485                                 bp->b_pages[bp->b_npages] = m;
 486                                 bp->b_npages++;
 487                         }
 488                         if (m->valid == VM_PAGE_BITS_ALL)
 489                                 tbp->b_pages[j] = bogus_page;
 490                 }
 491                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 492                 /*
 493                  * Don't inherit tbp->b_bufsize as it may be larger due to
 494                  * a non-page-aligned size.  Instead just aggregate using
 495                  * 'size'.
 496                  */
 497                 if (tbp->b_bcount != size)
 498                         printf("warning: tbp->b_bcount wrong %ld vs %ld\n", tbp->b_bcount, size);
 499                 if (tbp->b_bufsize != size)
 500                         printf("warning: tbp->b_bufsize wrong %ld vs %ld\n", tbp->b_bufsize, size);
 501                 bp->b_bcount += size;
 502                 bp->b_bufsize += size;
 503         }
 504
 505         /*
 506          * Fully valid pages in the cluster are already good and do not need
 507          * to be re-read from disk.  Replace the page with bogus_page
 508          */
 509         VM_OBJECT_WLOCK(bp->b_bufobj->bo_object);
 510         for (j = 0; j < bp->b_npages; j++) {
 511                 VM_OBJECT_ASSERT_WLOCKED(bp->b_pages[j]->object);
 512                 if (bp->b_pages[j]->valid == VM_PAGE_BITS_ALL)
 513                         bp->b_pages[j] = bogus_page;
 514         }
 515         VM_OBJECT_WUNLOCK(bp->b_bufobj->bo_object);
 516         if (bp->b_bufsize > bp->b_kvasize)
 517                 panic("cluster_rbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
 518                     bp->b_bufsize, bp->b_kvasize);
 519
 520         if (buf_mapped(bp)) {
 521                 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 522                     (vm_page_t *)bp->b_pages, bp->b_npages);
 523         }
 524         return (bp);
 525 }
 526
 527 /*
 528  * Cleanup after a clustered read or write.
 529  * This is complicated by the fact that any of the buffers might have
 530  * extra memory (if there were no empty buffer headers at allocbuf time)
 531  * that we will need to shift around.
 532  */
 533 static void
 534 cluster_callback(bp)
 535         struct buf *bp;
 536 {
 537         struct buf *nbp, *tbp;
 538         int error = 0;
 539
 540         /*
 541          * Must propogate errors to all the components.
 542          */
 543         if (bp->b_ioflags & BIO_ERROR)
 544                 error = bp->b_error;
 545
 546         if (buf_mapped(bp)) {
 547                 pmap_qremove(trunc_page((vm_offset_t) bp->b_data),
 548                     bp->b_npages);
 549         }
 550         /*
 551          * Move memory from the large cluster buffer into the component
 552          * buffers and mark IO as done on these.
 553          */
 554         for (tbp = TAILQ_FIRST(&bp->b_cluster.cluster_head);
 555                 tbp; tbp = nbp) {
 556                 nbp = TAILQ_NEXT(&tbp->b_cluster, cluster_entry);
 557                 if (error) {
 558                         tbp->b_ioflags |= BIO_ERROR;
 559                         tbp->b_error = error;
 560                 } else {
 561                         tbp->b_dirtyoff = tbp->b_dirtyend = 0;
 562                         tbp->b_flags &= ~B_INVAL;
 563                         tbp->b_ioflags &= ~BIO_ERROR;
 564                         /*
 565                          * XXX the bdwrite()/bqrelse() issued during
 566                          * cluster building clears B_RELBUF (see bqrelse()
 567                          * comment).  If direct I/O was specified, we have
 568                          * to restore it here to allow the buffer and VM
 569                          * to be freed.
 570                          */
 571                         if (tbp->b_flags & B_DIRECT)
 572                                 tbp->b_flags |= B_RELBUF;
 573                 }
 574                 bufdone(tbp);
 575         }
 576         pbrelvp(bp);
 577         relpbuf(bp, &cluster_pbuf_freecnt);
 578 }
 579
 580 /*
 581  *      cluster_wbuild_wb:
 582  *
 583  *      Implement modified write build for cluster.
 584  *
 585  *              write_behind = 0        write behind disabled
 586  *              write_behind = 1        write behind normal (default)
 587  *              write_behind = 2        write behind backed-off
 588  */
 589
 590 static __inline int
 591 cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len,
 592     int gbflags)
 593 {
 594         int r = 0;
 595
 596         switch (write_behind) {
 597         case 2:
 598                 if (start_lbn < len)
 599                         break;
 600                 start_lbn -= len;
 601                 /* FALLTHROUGH */
 602         case 1:
 603                 r = cluster_wbuild(vp, size, start_lbn, len, gbflags);
 604                 /* FALLTHROUGH */
 605         default:
 606                 /* FALLTHROUGH */
 607                 break;
 608         }
 609         return(r);
 610 }
 611
 612 /*
 613  * Do clustered write for FFS.
 614  *
 615  * Three cases:
 616  *      1. Write is not sequential (write asynchronously)
 617  *      Write is sequential:
 618  *      2.      beginning of cluster - begin cluster
 619  *      3.      middle of a cluster - add to cluster
 620  *      4.      end of a cluster - asynchronously write cluster
 621  */
 622 void
 623 cluster_write(struct vnode *vp, struct buf *bp, u_quad_t filesize, int seqcount,
 624     int gbflags)
 625 {
 626         daddr_t lbn;
 627         int maxclen, cursize;
 628         int lblocksize;
 629         int async;
 630
 631         if (!unmapped_buf_allowed)
 632                 gbflags &= ~GB_UNMAPPED;
 633
 634         if (vp->v_type == VREG) {
 635                 async = DOINGASYNC(vp);
 636                 lblocksize = vp->v_mount->mnt_stat.f_iosize;
 637         } else {
 638                 async = 0;
 639                 lblocksize = bp->b_bufsize;
 640         }
 641         lbn = bp->b_lblkno;
 642         KASSERT(bp->b_offset != NOOFFSET, ("cluster_write: no buffer offset"));
 643
 644         /* Initialize vnode to beginning of file. */
 645         if (lbn == 0)
 646                 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
 647
 648         if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
 649             (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
 650                 maxclen = vp->v_mount->mnt_iosize_max / lblocksize - 1;
 651                 if (vp->v_clen != 0) {
 652                         /*
 653                          * Next block is not sequential.
 654                          *
 655                          * If we are not writing at end of file, the process
 656                          * seeked to another point in the file since its last
 657                          * write, or we have reached our maximum cluster size,
 658                          * then push the previous cluster. Otherwise try
 659                          * reallocating to make it sequential.
 660                          *
 661                          * Change to algorithm: only push previous cluster if
 662                          * it was sequential from the point of view of the
 663                          * seqcount heuristic, otherwise leave the buffer
 664                          * intact so we can potentially optimize the I/O
 665                          * later on in the buf_daemon or update daemon
 666                          * flush.
 667                          */
 668                         cursize = vp->v_lastw - vp->v_cstart + 1;
 669                         if (((u_quad_t) bp->b_offset + lblocksize) != filesize ||
 670                             lbn != vp->v_lastw + 1 || vp->v_clen <= cursize) {
 671                                 if (!async && seqcount > 0) {
 672                                         cluster_wbuild_wb(vp, lblocksize,
 673                                             vp->v_cstart, cursize, gbflags);
 674                                 }
 675                         } else {
 676                                 struct buf **bpp, **endbp;
 677                                 struct cluster_save *buflist;
 678
 679                                 buflist = cluster_collectbufs(vp, bp, gbflags);
 680                                 endbp = &buflist->bs_children
 681                                     [buflist->bs_nchildren - 1];
 682                                 if (VOP_REALLOCBLKS(vp, buflist)) {
 683                                         /*
 684                                          * Failed, push the previous cluster
 685                                          * if *really* writing sequentially
 686                                          * in the logical file (seqcount > 1),
 687                                          * otherwise delay it in the hopes that
 688                                          * the low level disk driver can
 689                                          * optimize the write ordering.
 690                                          */
 691                                         for (bpp = buflist->bs_children;
 692                                              bpp < endbp; bpp++)
 693                                                 brelse(*bpp);
 694                                         free(buflist, M_SEGMENT);
 695                                         if (seqcount > 1) {
 696                                                 cluster_wbuild_wb(vp,
 697                                                     lblocksize, vp->v_cstart,
 698                                                     cursize, gbflags);
 699                                         }
 700                                 } else {
 701                                         /*
 702                                          * Succeeded, keep building cluster.
 703                                          */
 704                                         for (bpp = buflist->bs_children;
 705                                              bpp <= endbp; bpp++)
 706                                                 bdwrite(*bpp);
 707                                         free(buflist, M_SEGMENT);
 708                                         vp->v_lastw = lbn;
 709                                         vp->v_lasta = bp->b_blkno;
 710                                         return;
 711                                 }
 712                         }
 713                 }
 714                 /*
 715                  * Consider beginning a cluster. If at end of file, make
 716                  * cluster as large as possible, otherwise find size of
 717                  * existing cluster.
 718                  */
 719                 if ((vp->v_type == VREG) &&
 720                         ((u_quad_t) bp->b_offset + lblocksize) != filesize &&
 721                     (bp->b_blkno == bp->b_lblkno) &&
 722                     (VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen, NULL) ||
 723                      bp->b_blkno == -1)) {
 724                         bawrite(bp);
 725                         vp->v_clen = 0;
 726                         vp->v_lasta = bp->b_blkno;
 727                         vp->v_cstart = lbn + 1;
 728                         vp->v_lastw = lbn;
 729                         return;
 730                 }
 731                 vp->v_clen = maxclen;
 732                 if (!async && maxclen == 0) {   /* I/O not contiguous */
 733                         vp->v_cstart = lbn + 1;
 734                         bawrite(bp);
 735                 } else {        /* Wait for rest of cluster */
 736                         vp->v_cstart = lbn;
 737                         bdwrite(bp);
 738                 }
 739         } else if (lbn == vp->v_cstart + vp->v_clen) {
 740                 /*
 741                  * At end of cluster, write it out if seqcount tells us we
 742                  * are operating sequentially, otherwise let the buf or
 743                  * update daemon handle it.
 744                  */
 745                 bdwrite(bp);
 746                 if (seqcount > 1) {
 747                         cluster_wbuild_wb(vp, lblocksize, vp->v_cstart,
 748                             vp->v_clen + 1, gbflags);
 749                 }
 750                 vp->v_clen = 0;
 751                 vp->v_cstart = lbn + 1;
 752         } else if (vm_page_count_severe()) {
 753                 /*
 754                  * We are low on memory, get it going NOW
 755                  */
 756                 bawrite(bp);
 757         } else {
 758                 /*
 759                  * In the middle of a cluster, so just delay the I/O for now.
 760                  */
 761                 bdwrite(bp);
 762         }
 763         vp->v_lastw = lbn;
 764         vp->v_lasta = bp->b_blkno;
 765 }
 766
 767
 768 /*
 769  * This is an awful lot like cluster_rbuild...wish they could be combined.
 770  * The last lbn argument is the current block on which I/O is being
 771  * performed.  Check to see that it doesn't fall in the middle of
 772  * the current block (if last_bp == NULL).
 773  */
 774 int
 775 cluster_wbuild(struct vnode *vp, long size, daddr_t start_lbn, int len,
 776     int gbflags)
 777 {
 778         struct buf *bp, *tbp;
 779         struct bufobj *bo;
 780         int i, j;
 781         int totalwritten = 0;
 782         int dbsize = btodb(size);
 783
 784         if (!unmapped_buf_allowed)
 785                 gbflags &= ~GB_UNMAPPED;
 786
 787         bo = &vp->v_bufobj;
 788         while (len > 0) {
 789                 /*
 790                  * If the buffer is not delayed-write (i.e. dirty), or it
 791                  * is delayed-write but either locked or inval, it cannot
 792                  * partake in the clustered write.
 793                  */
 794                 BO_LOCK(bo);
 795                 if ((tbp = gbincore(&vp->v_bufobj, start_lbn)) == NULL ||
 796                     (tbp->b_vflags & BV_BKGRDINPROG)) {
 797                         BO_UNLOCK(bo);
 798                         ++start_lbn;
 799                         --len;
 800                         continue;
 801                 }
 802                 if (BUF_LOCK(tbp,
 803                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, BO_LOCKPTR(bo))) {
 804                         ++start_lbn;
 805                         --len;
 806                         continue;
 807                 }
 808                 if ((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) {
 809                         BUF_UNLOCK(tbp);
 810                         ++start_lbn;
 811                         --len;
 812                         continue;
 813                 }
 814                 if (tbp->b_pin_count >  0) {
 815                         BUF_UNLOCK(tbp);
 816                         ++start_lbn;
 817                         --len;
 818                         continue;
 819                 }
 820                 bremfree(tbp);
 821                 tbp->b_flags &= ~B_DONE;
 822
 823                 /*
 824                  * Extra memory in the buffer, punt on this buffer.
 825                  * XXX we could handle this in most cases, but we would
 826                  * have to push the extra memory down to after our max
 827                  * possible cluster size and then potentially pull it back
 828                  * up if the cluster was terminated prematurely--too much
 829                  * hassle.
 830                  */
 831                 if (((tbp->b_flags & (B_CLUSTEROK | B_MALLOC | B_VMIO)) !=
 832                      (B_CLUSTEROK | B_VMIO)) ||
 833                   (tbp->b_bcount != tbp->b_bufsize) ||
 834                   (tbp->b_bcount != size) ||
 835                   (len == 1) ||
 836                   ((bp = (vp->v_vflag & VV_MD) != 0 ?
 837                   trypbuf(&cluster_pbuf_freecnt) :
 838                   getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
 839                         totalwritten += tbp->b_bufsize;
 840                         bawrite(tbp);
 841                         ++start_lbn;
 842                         --len;
 843                         continue;
 844                 }
 845
 846                 /*
 847                  * We got a pbuf to make the cluster in.
 848                  * so initialise it.
 849                  */
 850                 TAILQ_INIT(&bp->b_cluster.cluster_head);
 851                 bp->b_bcount = 0;
 852                 bp->b_bufsize = 0;
 853                 bp->b_npages = 0;
 854                 if (tbp->b_wcred != NOCRED)
 855                         bp->b_wcred = crhold(tbp->b_wcred);
 856
 857                 bp->b_blkno = tbp->b_blkno;
 858                 bp->b_lblkno = tbp->b_lblkno;
 859                 bp->b_offset = tbp->b_offset;
 860
 861                 /*
 862                  * We are synthesizing a buffer out of vm_page_t's, but
 863                  * if the block size is not page aligned then the starting
 864                  * address may not be either.  Inherit the b_data offset
 865                  * from the original buffer.
 866                  */
 867                 if ((gbflags & GB_UNMAPPED) == 0 ||
 868                     (tbp->b_flags & B_VMIO) == 0) {
 869                         bp->b_data = (char *)((vm_offset_t)bp->b_data |
 870                             ((vm_offset_t)tbp->b_data & PAGE_MASK));
 871                 } else {
 872                         bp->b_data = unmapped_buf;
 873                 }
 874                 bp->b_flags |= B_CLUSTER | (tbp->b_flags & (B_VMIO |
 875                     B_NEEDCOMMIT));
 876                 bp->b_iodone = cluster_callback;
 877                 pbgetvp(vp, bp);
 878                 /*
 879                  * From this location in the file, scan forward to see
 880                  * if there are buffers with adjacent data that need to
 881                  * be written as well.
 882                  */
 883                 for (i = 0; i < len; ++i, ++start_lbn) {
 884                         if (i != 0) { /* If not the first buffer */
 885                                 /*
 886                                  * If the adjacent data is not even in core it
 887                                  * can't need to be written.
 888                                  */
 889                                 BO_LOCK(bo);
 890                                 if ((tbp = gbincore(bo, start_lbn)) == NULL ||
 891                                     (tbp->b_vflags & BV_BKGRDINPROG)) {
 892                                         BO_UNLOCK(bo);
 893                                         break;
 894                                 }
 895
 896                                 /*
 897                                  * If it IS in core, but has different
 898                                  * characteristics, or is locked (which
 899                                  * means it could be undergoing a background
 900                                  * I/O or be in a weird state), then don't
 901                                  * cluster with it.
 902                                  */
 903                                 if (BUF_LOCK(tbp,
 904                                     LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
 905                                     BO_LOCKPTR(bo)))
 906                                         break;
 907
 908                                 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
 909                                     B_INVAL | B_DELWRI | B_NEEDCOMMIT))
 910                                     != (B_DELWRI | B_CLUSTEROK |
 911                                     (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
 912                                     tbp->b_wcred != bp->b_wcred) {
 913                                         BUF_UNLOCK(tbp);
 914                                         break;
 915                                 }
 916
 917                                 /*
 918                                  * Check that the combined cluster
 919                                  * would make sense with regard to pages
 920                                  * and would not be too large
 921                                  */
 922                                 if ((tbp->b_bcount != size) ||
 923                                   ((bp->b_blkno + (dbsize * i)) !=
 924                                     tbp->b_blkno) ||
 925                                   ((tbp->b_npages + bp->b_npages) >
 926                                     (vp->v_mount->mnt_iosize_max / PAGE_SIZE))) {
 927                                         BUF_UNLOCK(tbp);
 928                                         break;
 929                                 }
 930
 931                                 /*
 932                                  * Do not pull in pinned buffers.
 933                                  */
 934                                 if (tbp->b_pin_count > 0) {
 935                                         BUF_UNLOCK(tbp);
 936                                         break;
 937                                 }
 938
 939                                 /*
 940                                  * Ok, it's passed all the tests,
 941                                  * so remove it from the free list
 942                                  * and mark it busy. We will use it.
 943                                  */
 944                                 bremfree(tbp);
 945                                 tbp->b_flags &= ~B_DONE;
 946                         } /* end of code for non-first buffers only */
 947                         /*
 948                          * If the IO is via the VM then we do some
 949                          * special VM hackery (yuck).  Since the buffer's
 950                          * block size may not be page-aligned it is possible
 951                          * for a page to be shared between two buffers.  We
 952                          * have to get rid of the duplication when building
 953                          * the cluster.
 954                          */
 955                         if (tbp->b_flags & B_VMIO) {
 956                                 vm_page_t m;
 957
 958                                 VM_OBJECT_WLOCK(tbp->b_bufobj->bo_object);
 959                                 if (i == 0) {
 960                                         vfs_drain_busy_pages(tbp);
 961                                 } else { /* if not first buffer */
 962                                         for (j = 0; j < tbp->b_npages; j += 1) {
 963                                                 m = tbp->b_pages[j];
 964                                                 if (vm_page_xbusied(m)) {
 965                                                         VM_OBJECT_WUNLOCK(
 966                                                             tbp->b_object);
 967                                                         bqrelse(tbp);
 968                                                         goto finishcluster;
 969                                                 }
 970                                         }
 971                                 }
 972                                 for (j = 0; j < tbp->b_npages; j += 1) {
 973                                         m = tbp->b_pages[j];
 974                                         vm_page_sbusy(m);
 975                                         vm_object_pip_add(m->object, 1);
 976                                         if ((bp->b_npages == 0) ||
 977                                           (bp->b_pages[bp->b_npages - 1] != m)) {
 978                                                 bp->b_pages[bp->b_npages] = m;
 979                                                 bp->b_npages++;
 980                                         }
 981                                 }
 982                                 VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);
 983                         }
 984                         bp->b_bcount += size;
 985                         bp->b_bufsize += size;
 986                         /*
 987                          * If any of the clustered buffers have their
 988                          * B_BARRIER flag set, transfer that request to
 989                          * the cluster.
 990                          */
 991                         bp->b_flags |= (tbp->b_flags & B_BARRIER);
 992                         tbp->b_flags &= ~(B_DONE | B_BARRIER);
 993                         tbp->b_flags |= B_ASYNC;
 994                         tbp->b_ioflags &= ~BIO_ERROR;
 995                         tbp->b_iocmd = BIO_WRITE;
 996                         bundirty(tbp);
 997                         reassignbuf(tbp);               /* put on clean list */
 998                         bufobj_wref(tbp->b_bufobj);
 999                         BUF_KERNPROC(tbp);
1000                         TAILQ_INSERT_TAIL(&bp->b_cluster.cluster_head,
1001                                 tbp, b_cluster.cluster_entry);
1002                 }
1003         finishcluster:
1004                 if (buf_mapped(bp)) {
1005                         pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
1006                             (vm_page_t *)bp->b_pages, bp->b_npages);
1007                 }
1008                 if (bp->b_bufsize > bp->b_kvasize)
1009                         panic(
1010                             "cluster_wbuild: b_bufsize(%ld) > b_kvasize(%d)\n",
1011                             bp->b_bufsize, bp->b_kvasize);
1012                 totalwritten += bp->b_bufsize;
1013                 bp->b_dirtyoff = 0;
1014                 bp->b_dirtyend = bp->b_bufsize;
1015                 bawrite(bp);
1016
1017                 len -= i;
1018         }
1019         return totalwritten;
1020 }
1021
1022 /*
1023  * Collect together all the buffers in a cluster.
1024  * Plus add one additional buffer.
1025  */
1026 static struct cluster_save *
1027 cluster_collectbufs(struct vnode *vp, struct buf *last_bp, int gbflags)
1028 {
1029         struct cluster_save *buflist;
1030         struct buf *bp;
1031         daddr_t lbn;
1032         int i, len;
1033
1034         len = vp->v_lastw - vp->v_cstart + 1;
1035         buflist = malloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
1036             M_SEGMENT, M_WAITOK);
1037         buflist->bs_nchildren = 0;
1038         buflist->bs_children = (struct buf **) (buflist + 1);
1039         for (lbn = vp->v_cstart, i = 0; i < len; lbn++, i++) {
1040                 (void)bread_gb(vp, lbn, last_bp->b_bcount, NOCRED,
1041                     gbflags, &bp);
1042                 buflist->bs_children[i] = bp;
1043                 if (bp->b_blkno == bp->b_lblkno)
1044                         VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno,
1045                                 NULL, NULL);
1046         }
1047         buflist->bs_children[i] = bp = last_bp;
1048         if (bp->b_blkno == bp->b_lblkno)
1049                 VOP_BMAP(vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL);
1050         buflist->bs_nchildren = i + 1;
1051         return (buflist);
1052 }