sys/kern/vfs_cluster.c

   1 /*-
   2  * Copyright (c) 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Modifications/enhancements:
   5  *      Copyright (c) 1995 John S. Dyson.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by the University of
  18  *      California, Berkeley and its contributors.
  19  * 4. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  *
  35  *      @(#)vfs_cluster.c       8.7 (Berkeley) 2/13/94
  36  * $FreeBSD: src/sys/kern/vfs_cluster.c,v 1.92.2.9 2001/11/18 07:10:59 dillon Exp $
  37  * $DragonFly: src/sys/kern/vfs_cluster.c,v 1.40 2008/07/14 03:09:00 dillon Exp $
  38  */
  39
  40 #include "opt_debug_cluster.h"
  41
  42 #include <sys/param.h>
  43 #include <sys/systm.h>
  44 #include <sys/kernel.h>
  45 #include <sys/proc.h>
  46 #include <sys/buf.h>
  47 #include <sys/vnode.h>
  48 #include <sys/malloc.h>
  49 #include <sys/mount.h>
  50 #include <sys/resourcevar.h>
  51 #include <sys/vmmeter.h>
  52 #include <vm/vm.h>
  53 #include <vm/vm_object.h>
  54 #include <vm/vm_page.h>
  55 #include <sys/sysctl.h>
  56 #include <sys/buf2.h>
  57 #include <vm/vm_page2.h>
  58
  59 #if defined(CLUSTERDEBUG)
  60 #include <sys/sysctl.h>
  61 static int      rcluster= 0;
  62 SYSCTL_INT(_debug, OID_AUTO, rcluster, CTLFLAG_RW, &rcluster, 0, "");
  63 #endif
  64
  65 static MALLOC_DEFINE(M_SEGMENT, "cluster_save", "cluster_save buffer");
  66
  67 static struct cluster_save *
  68         cluster_collectbufs (struct vnode *vp, struct buf *last_bp,
  69                             int blksize);
  70 static struct buf *
  71         cluster_rbuild (struct vnode *vp, off_t filesize, off_t loffset,
  72                             off_t doffset, int blksize, int run,
  73                             struct buf *fbp);
  74 static void cluster_callback (struct bio *);
  75
  76
  77 static int write_behind = 1;
  78 SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0, "");
  79
  80 extern vm_page_t        bogus_page;
  81
  82 extern int cluster_pbuf_freecnt;
  83
  84 /*
  85  * Maximum number of blocks for read-ahead.
  86  */
  87 #define MAXRA 32
  88
  89 /*
  90  * This replaces bread.
  91  */
  92 int
  93 cluster_read(struct vnode *vp, off_t filesize, off_t loffset,
  94              int blksize, int totread, int seqcount, struct buf **bpp)
  95 {
  96         struct buf *bp, *rbp, *reqbp;
  97         off_t origoffset;
  98         off_t doffset;
  99         int error;
 100         int i;
 101         int maxra, racluster;
 102
 103         error = 0;
 104
 105         /*
 106          * Try to limit the amount of read-ahead by a few
 107          * ad-hoc parameters.  This needs work!!!
 108          */
 109         racluster = vmaxiosize(vp) / blksize;
 110         maxra = 2 * racluster + (totread / blksize);
 111         if (maxra > MAXRA)
 112                 maxra = MAXRA;
 113         if (maxra > nbuf/8)
 114                 maxra = nbuf/8;
 115
 116         /*
 117          * Get the requested block.
 118          */
 119         *bpp = reqbp = bp = getblk(vp, loffset, blksize, 0, 0);
 120         origoffset = loffset;
 121
 122         /*
 123          * if it is in the cache, then check to see if the reads have been
 124          * sequential.  If they have, then try some read-ahead, otherwise
 125          * back-off on prospective read-aheads.
 126          */
 127         if (bp->b_flags & B_CACHE) {
 128                 if (!seqcount) {
 129                         return 0;
 130                 } else if ((bp->b_flags & B_RAM) == 0) {
 131                         return 0;
 132                 } else {
 133                         struct buf *tbp;
 134                         bp->b_flags &= ~B_RAM;
 135
 136                         /*
 137                          * Set read-ahead-mark only if we can passively lock
 138                          * the buffer.  Note that with these flags the bp
 139                          * could very exist even though NULL is returned.
 140                          */
 141                         for (i = 1; i < maxra; i++) {
 142                                 tbp = findblk(vp, loffset + i * blksize,
 143                                               FINDBLK_NBLOCK);
 144                                 if (tbp == NULL)
 145                                         break;
 146                                 if (((i % racluster) == (racluster - 1)) ||
 147                                     (i == (maxra - 1))) {
 148                                         tbp->b_flags |= B_RAM;
 149                                 }
 150                                 BUF_UNLOCK(tbp);
 151                         }
 152                         if (i >= maxra)
 153                                 return 0;
 154                         loffset += i * blksize;
 155                 }
 156                 reqbp = bp = NULL;
 157         } else {
 158                 off_t firstread = bp->b_loffset;
 159                 int nblks;
 160
 161                 /*
 162                  * Set-up synchronous read for bp.
 163                  */
 164                 bp->b_cmd = BUF_CMD_READ;
 165                 bp->b_bio1.bio_done = biodone_sync;
 166                 bp->b_bio1.bio_flags |= BIO_SYNC;
 167
 168                 KASSERT(firstread != NOOFFSET,
 169                         ("cluster_read: no buffer offset"));
 170                 if (firstread + totread > filesize)
 171                         totread = (int)(filesize - firstread);
 172                 nblks = totread / blksize;
 173                 if (nblks) {
 174                         int burstbytes;
 175
 176                         if (nblks > racluster)
 177                                 nblks = racluster;
 178
 179                         error = VOP_BMAP(vp, loffset, &doffset,
 180                                          &burstbytes, NULL, BUF_CMD_READ);
 181                         if (error)
 182                                 goto single_block_read;
 183                         if (doffset == NOOFFSET)
 184                                 goto single_block_read;
 185                         if (burstbytes < blksize * 2)
 186                                 goto single_block_read;
 187                         if (nblks > burstbytes / blksize)
 188                                 nblks = burstbytes / blksize;
 189
 190                         bp = cluster_rbuild(vp, filesize, loffset,
 191                                             doffset, blksize, nblks, bp);
 192                         loffset += bp->b_bufsize;
 193                 } else {
 194 single_block_read:
 195                         /*
 196                          * if it isn't in the cache, then get a chunk from
 197                          * disk if sequential, otherwise just get the block.
 198                          */
 199                         bp->b_flags |= B_RAM;
 200                         loffset += blksize;
 201                 }
 202         }
 203
 204         /*
 205          * If B_CACHE was not set issue bp.  bp will either be an
 206          * asynchronous cluster buf or a synchronous single-buf.
 207          * If it is a single buf it will be the same as reqbp.
 208          *
 209          * NOTE: Once an async cluster buf is issued bp becomes invalid.
 210          */
 211         if (bp) {
 212 #if defined(CLUSTERDEBUG)
 213                 if (rcluster)
 214                         kprintf("S(%lld,%d,%d) ",
 215                             bp->b_loffset, bp->b_bcount, seqcount);
 216 #endif
 217                 if ((bp->b_flags & B_CLUSTER) == 0)
 218                         vfs_busy_pages(vp, bp);
 219                 bp->b_flags &= ~(B_ERROR|B_INVAL);
 220                 vn_strategy(vp, &bp->b_bio1);
 221                 error = 0;
 222                 /* bp invalid now */
 223         }
 224
 225         /*
 226          * If we have been doing sequential I/O, then do some read-ahead.
 227          *
 228          * Only mess with buffers which we can immediately lock.  HAMMER
 229          * will do device-readahead irrespective of what the blocks
 230          * represent.
 231          */
 232         rbp = NULL;
 233         if (!error &&
 234             seqcount &&
 235             loffset < origoffset + seqcount * blksize &&
 236             loffset + blksize <= filesize
 237         ) {
 238                 int nblksread;
 239                 int ntoread;
 240                 int burstbytes;
 241                 int tmp_error;
 242
 243                 rbp = getblk(vp, loffset, blksize,
 244                              GETBLK_SZMATCH|GETBLK_NOWAIT, 0);
 245                 if (rbp == NULL)
 246                         goto no_read_ahead;
 247                 if ((rbp->b_flags & B_CACHE)) {
 248                         bqrelse(rbp);
 249                         goto no_read_ahead;
 250                 }
 251
 252                 /*
 253                  * An error from the read-ahead bmap has nothing to do
 254                  * with the caller's original request.
 255                  */
 256                 tmp_error = VOP_BMAP(vp, loffset, &doffset,
 257                                      &burstbytes, NULL, BUF_CMD_READ);
 258                 if (tmp_error || doffset == NOOFFSET) {
 259                         rbp->b_flags |= B_INVAL;
 260                         brelse(rbp);
 261                         rbp = NULL;
 262                         goto no_read_ahead;
 263                 }
 264                 ntoread = burstbytes / blksize;
 265                 nblksread = (totread + blksize - 1) / blksize;
 266                 if (seqcount < nblksread)
 267                         seqcount = nblksread;
 268                 if (ntoread > seqcount)
 269                         ntoread = seqcount;
 270
 271                 /*
 272                  * rbp: async read
 273                  */
 274                 rbp->b_cmd = BUF_CMD_READ;
 275                 rbp->b_flags |= B_RAM/* | B_AGE*/;
 276
 277                 if (burstbytes) {
 278                         rbp = cluster_rbuild(vp, filesize, loffset,
 279                                              doffset, blksize,
 280                                              ntoread, rbp);
 281                 } else {
 282                         rbp->b_bio2.bio_offset = doffset;
 283                 }
 284 #if defined(CLUSTERDEBUG)
 285                 if (rcluster) {
 286                         if (bp)
 287                                 kprintf("A+(%lld,%d,%lld,%d) ",
 288                                     rbp->b_loffset, rbp->b_bcount,
 289                                     rbp->b_loffset - origoffset,
 290                                     seqcount);
 291                         else
 292                                 kprintf("A(%lld,%d,%lld,%d) ",
 293                                     rbp->b_loffset, rbp->b_bcount,
 294                                     rbp->b_loffset - origoffset,
 295                                     seqcount);
 296                 }
 297 #endif
 298                 rbp->b_flags &= ~(B_ERROR|B_INVAL);
 299
 300                 if ((rbp->b_flags & B_CLUSTER) == 0)
 301                         vfs_busy_pages(vp, rbp);
 302                 BUF_KERNPROC(rbp);
 303                 vn_strategy(vp, &rbp->b_bio1);
 304                 /* rbp invalid now */
 305         }
 306
 307         /*
 308          * Wait for our original buffer to complete its I/O.  reqbp will
 309          * be NULL if the original buffer was B_CACHE.  We are returning
 310          * (*bpp) which is the same as reqbp when reqbp != NULL.
 311          */
 312 no_read_ahead:
 313         if (reqbp) {
 314                 KKASSERT(reqbp->b_bio1.bio_flags & BIO_SYNC);
 315                 error = biowait(&reqbp->b_bio1, "clurd");
 316         }
 317         return (error);
 318 }
 319
 320 /*
 321  * If blocks are contiguous on disk, use this to provide clustered
 322  * read ahead.  We will read as many blocks as possible sequentially
 323  * and then parcel them up into logical blocks in the buffer hash table.
 324  *
 325  * This function either returns a cluster buf or it returns fbp.  fbp is
 326  * already expected to be set up as a synchronous or asynchronous request.
 327  *
 328  * If a cluster buf is returned it will always be async.
 329  */
 330 static struct buf *
 331 cluster_rbuild(struct vnode *vp, off_t filesize, off_t loffset, off_t doffset,
 332                int blksize, int run, struct buf *fbp)
 333 {
 334         struct buf *bp, *tbp;
 335         off_t boffset;
 336         int i, j;
 337         int maxiosize = vmaxiosize(vp);
 338
 339         /*
 340          * avoid a division
 341          */
 342         while (loffset + run * blksize > filesize) {
 343                 --run;
 344         }
 345
 346         tbp = fbp;
 347         tbp->b_bio2.bio_offset = doffset;
 348         if((tbp->b_flags & B_MALLOC) ||
 349             ((tbp->b_flags & B_VMIO) == 0) || (run <= 1)) {
 350                 return tbp;
 351         }
 352
 353         bp = trypbuf(&cluster_pbuf_freecnt);
 354         if (bp == NULL) {
 355                 return tbp;
 356         }
 357
 358         /*
 359          * We are synthesizing a buffer out of vm_page_t's, but
 360          * if the block size is not page aligned then the starting
 361          * address may not be either.  Inherit the b_data offset
 362          * from the original buffer.
 363          */
 364         bp->b_data = (char *)((vm_offset_t)bp->b_data |
 365             ((vm_offset_t)tbp->b_data & PAGE_MASK));
 366         bp->b_flags |= B_CLUSTER | B_VMIO;
 367         bp->b_cmd = BUF_CMD_READ;
 368         bp->b_bio1.bio_done = cluster_callback;         /* default to async */
 369         bp->b_bio1.bio_caller_info1.cluster_head = NULL;
 370         bp->b_bio1.bio_caller_info2.cluster_tail = NULL;
 371         bp->b_loffset = loffset;
 372         bp->b_bio2.bio_offset = doffset;
 373         KASSERT(bp->b_loffset != NOOFFSET,
 374                 ("cluster_rbuild: no buffer offset"));
 375
 376         bp->b_bcount = 0;
 377         bp->b_bufsize = 0;
 378         bp->b_xio.xio_npages = 0;
 379
 380         for (boffset = doffset, i = 0; i < run; ++i, boffset += blksize) {
 381                 if (i) {
 382                         if ((bp->b_xio.xio_npages * PAGE_SIZE) +
 383                             round_page(blksize) > maxiosize) {
 384                                 break;
 385                         }
 386
 387                         /*
 388                          * Shortcut some checks and try to avoid buffers that
 389                          * would block in the lock.  The same checks have to
 390                          * be made again after we officially get the buffer.
 391                          */
 392                         tbp = getblk(vp, loffset + i * blksize, blksize,
 393                                      GETBLK_SZMATCH|GETBLK_NOWAIT, 0);
 394                         if (tbp == NULL)
 395                                 break;
 396                         for (j = 0; j < tbp->b_xio.xio_npages; j++) {
 397                                 if (tbp->b_xio.xio_pages[j]->valid)
 398                                         break;
 399                         }
 400                         if (j != tbp->b_xio.xio_npages) {
 401                                 bqrelse(tbp);
 402                                 break;
 403                         }
 404
 405                         /*
 406                          * Stop scanning if the buffer is fuly valid
 407                          * (marked B_CACHE), or locked (may be doing a
 408                          * background write), or if the buffer is not
 409                          * VMIO backed.  The clustering code can only deal
 410                          * with VMIO-backed buffers.
 411                          */
 412                         if ((tbp->b_flags & (B_CACHE|B_LOCKED)) ||
 413                             (tbp->b_flags & B_VMIO) == 0 ||
 414                             (LIST_FIRST(&tbp->b_dep) != NULL &&
 415                              buf_checkread(tbp))
 416                         ) {
 417                                 bqrelse(tbp);
 418                                 break;
 419                         }
 420
 421                         /*
 422                          * The buffer must be completely invalid in order to
 423                          * take part in the cluster.  If it is partially valid
 424                          * then we stop.
 425                          */
 426                         for (j = 0;j < tbp->b_xio.xio_npages; j++) {
 427                                 if (tbp->b_xio.xio_pages[j]->valid)
 428                                         break;
 429                         }
 430                         if (j != tbp->b_xio.xio_npages) {
 431                                 bqrelse(tbp);
 432                                 break;
 433                         }
 434
 435                         /*
 436                          * Set a read-ahead mark as appropriate
 437                          */
 438                         if (i == 1 || i == (run - 1))
 439                                 tbp->b_flags |= B_RAM;
 440
 441                         /*
 442                          * Depress the priority of buffers not explicitly
 443                          * requested.
 444                          */
 445                         /* tbp->b_flags |= B_AGE; */
 446
 447                         /*
 448                          * Set the block number if it isn't set, otherwise
 449                          * if it is make sure it matches the block number we
 450                          * expect.
 451                          */
 452                         if (tbp->b_bio2.bio_offset == NOOFFSET) {
 453                                 tbp->b_bio2.bio_offset = boffset;
 454                         } else if (tbp->b_bio2.bio_offset != boffset) {
 455                                 brelse(tbp);
 456                                 break;
 457                         }
 458                 }
 459
 460                 /*
 461                  * The passed-in tbp (i == 0) will already be set up for
 462                  * async or sync operation.  All other tbp's acquire in
 463                  * our loop are set up for async operation.
 464                  */
 465                 tbp->b_cmd = BUF_CMD_READ;
 466                 BUF_KERNPROC(tbp);
 467                 cluster_append(&bp->b_bio1, tbp);
 468                 for (j = 0; j < tbp->b_xio.xio_npages; ++j) {
 469                         vm_page_t m;
 470                         m = tbp->b_xio.xio_pages[j];
 471                         vm_page_io_start(m);
 472                         vm_object_pip_add(m->object, 1);
 473                         if ((bp->b_xio.xio_npages == 0) ||
 474                                 (bp->b_xio.xio_pages[bp->b_xio.xio_npages-1] != m)) {
 475                                 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m;
 476                                 bp->b_xio.xio_npages++;
 477                         }
 478                         if ((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL)
 479                                 tbp->b_xio.xio_pages[j] = bogus_page;
 480                 }
 481                 /*
 482                  * XXX shouldn't this be += size for both, like in
 483                  * cluster_wbuild()?
 484                  *
 485                  * Don't inherit tbp->b_bufsize as it may be larger due to
 486                  * a non-page-aligned size.  Instead just aggregate using
 487                  * 'size'.
 488                  */
 489                 if (tbp->b_bcount != blksize)
 490                     kprintf("warning: tbp->b_bcount wrong %d vs %d\n", tbp->b_bcount, blksize);
 491                 if (tbp->b_bufsize != blksize)
 492                     kprintf("warning: tbp->b_bufsize wrong %d vs %d\n", tbp->b_bufsize, blksize);
 493                 bp->b_bcount += blksize;
 494                 bp->b_bufsize += blksize;
 495         }
 496
 497         /*
 498          * Fully valid pages in the cluster are already good and do not need
 499          * to be re-read from disk.  Replace the page with bogus_page
 500          */
 501         for (j = 0; j < bp->b_xio.xio_npages; j++) {
 502                 if ((bp->b_xio.xio_pages[j]->valid & VM_PAGE_BITS_ALL) ==
 503                     VM_PAGE_BITS_ALL) {
 504                         bp->b_xio.xio_pages[j] = bogus_page;
 505                 }
 506         }
 507         if (bp->b_bufsize > bp->b_kvasize) {
 508                 panic("cluster_rbuild: b_bufsize(%d) > b_kvasize(%d)",
 509                     bp->b_bufsize, bp->b_kvasize);
 510         }
 511         pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 512                 (vm_page_t *)bp->b_xio.xio_pages, bp->b_xio.xio_npages);
 513         BUF_KERNPROC(bp);
 514         return (bp);
 515 }
 516
 517 /*
 518  * Cleanup after a clustered read or write.
 519  * This is complicated by the fact that any of the buffers might have
 520  * extra memory (if there were no empty buffer headers at allocbuf time)
 521  * that we will need to shift around.
 522  *
 523  * The returned bio is &bp->b_bio1
 524  */
 525 void
 526 cluster_callback(struct bio *bio)
 527 {
 528         struct buf *bp = bio->bio_buf;
 529         struct buf *tbp;
 530         int error = 0;
 531
 532         /*
 533          * Must propogate errors to all the components.  A short read (EOF)
 534          * is a critical error.
 535          */
 536         if (bp->b_flags & B_ERROR) {
 537                 error = bp->b_error;
 538         } else if (bp->b_bcount != bp->b_bufsize) {
 539                 panic("cluster_callback: unexpected EOF on cluster %p!", bio);
 540         }
 541
 542         pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_xio.xio_npages);
 543         /*
 544          * Move memory from the large cluster buffer into the component
 545          * buffers and mark IO as done on these.  Since the memory map
 546          * is the same, no actual copying is required.
 547          */
 548         while ((tbp = bio->bio_caller_info1.cluster_head) != NULL) {
 549                 bio->bio_caller_info1.cluster_head = tbp->b_cluster_next;
 550                 if (error) {
 551                         tbp->b_flags |= B_ERROR;
 552                         tbp->b_error = error;
 553                 } else {
 554                         tbp->b_dirtyoff = tbp->b_dirtyend = 0;
 555                         tbp->b_flags &= ~(B_ERROR|B_INVAL);
 556                         /*
 557                          * XXX the bdwrite()/bqrelse() issued during
 558                          * cluster building clears B_RELBUF (see bqrelse()
 559                          * comment).  If direct I/O was specified, we have
 560                          * to restore it here to allow the buffer and VM
 561                          * to be freed.
 562                          */
 563                         if (tbp->b_flags & B_DIRECT)
 564                                 tbp->b_flags |= B_RELBUF;
 565                 }
 566                 biodone(&tbp->b_bio1);
 567         }
 568         relpbuf(bp, &cluster_pbuf_freecnt);
 569 }
 570
 571 /*
 572  *      cluster_wbuild_wb:
 573  *
 574  *      Implement modified write build for cluster.
 575  *
 576  *              write_behind = 0        write behind disabled
 577  *              write_behind = 1        write behind normal (default)
 578  *              write_behind = 2        write behind backed-off
 579  */
 580
 581 static __inline int
 582 cluster_wbuild_wb(struct vnode *vp, int blksize, off_t start_loffset, int len)
 583 {
 584         int r = 0;
 585
 586         switch(write_behind) {
 587         case 2:
 588                 if (start_loffset < len)
 589                         break;
 590                 start_loffset -= len;
 591                 /* fall through */
 592         case 1:
 593                 r = cluster_wbuild(vp, blksize, start_loffset, len);
 594                 /* fall through */
 595         default:
 596                 /* fall through */
 597                 break;
 598         }
 599         return(r);
 600 }
 601
 602 /*
 603  * Do clustered write for FFS.
 604  *
 605  * Three cases:
 606  *      1. Write is not sequential (write asynchronously)
 607  *      Write is sequential:
 608  *      2.      beginning of cluster - begin cluster
 609  *      3.      middle of a cluster - add to cluster
 610  *      4.      end of a cluster - asynchronously write cluster
 611  */
 612 void
 613 cluster_write(struct buf *bp, off_t filesize, int blksize, int seqcount)
 614 {
 615         struct vnode *vp;
 616         off_t loffset;
 617         int maxclen, cursize;
 618         int async;
 619
 620         vp = bp->b_vp;
 621         if (vp->v_type == VREG)
 622                 async = vp->v_mount->mnt_flag & MNT_ASYNC;
 623         else
 624                 async = 0;
 625         loffset = bp->b_loffset;
 626         KASSERT(bp->b_loffset != NOOFFSET,
 627                 ("cluster_write: no buffer offset"));
 628
 629         /* Initialize vnode to beginning of file. */
 630         if (loffset == 0)
 631                 vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
 632
 633         if (vp->v_clen == 0 || loffset != vp->v_lastw + blksize ||
 634             bp->b_bio2.bio_offset == NOOFFSET ||
 635             (bp->b_bio2.bio_offset != vp->v_lasta + blksize)) {
 636                 maxclen = vmaxiosize(vp);
 637                 if (vp->v_clen != 0) {
 638                         /*
 639                          * Next block is not sequential.
 640                          *
 641                          * If we are not writing at end of file, the process
 642                          * seeked to another point in the file since its last
 643                          * write, or we have reached our maximum cluster size,
 644                          * then push the previous cluster. Otherwise try
 645                          * reallocating to make it sequential.
 646                          *
 647                          * Change to algorithm: only push previous cluster if
 648                          * it was sequential from the point of view of the
 649                          * seqcount heuristic, otherwise leave the buffer
 650                          * intact so we can potentially optimize the I/O
 651                          * later on in the buf_daemon or update daemon
 652                          * flush.
 653                          */
 654                         cursize = vp->v_lastw - vp->v_cstart + blksize;
 655                         if (bp->b_loffset + blksize != filesize ||
 656                             loffset != vp->v_lastw + blksize || vp->v_clen <= cursize) {
 657                                 if (!async && seqcount > 0) {
 658                                         cluster_wbuild_wb(vp, blksize,
 659                                                 vp->v_cstart, cursize);
 660                                 }
 661                         } else {
 662                                 struct buf **bpp, **endbp;
 663                                 struct cluster_save *buflist;
 664
 665                                 buflist = cluster_collectbufs(vp, bp, blksize);
 666                                 endbp = &buflist->bs_children
 667                                     [buflist->bs_nchildren - 1];
 668                                 if (VOP_REALLOCBLKS(vp, buflist)) {
 669                                         /*
 670                                          * Failed, push the previous cluster
 671                                          * if *really* writing sequentially
 672                                          * in the logical file (seqcount > 1),
 673                                          * otherwise delay it in the hopes that
 674                                          * the low level disk driver can
 675                                          * optimize the write ordering.
 676                                          */
 677                                         for (bpp = buflist->bs_children;
 678                                              bpp < endbp; bpp++)
 679                                                 brelse(*bpp);
 680                                         kfree(buflist, M_SEGMENT);
 681                                         if (seqcount > 1) {
 682                                                 cluster_wbuild_wb(vp,
 683                                                     blksize, vp->v_cstart,
 684                                                     cursize);
 685                                         }
 686                                 } else {
 687                                         /*
 688                                          * Succeeded, keep building cluster.
 689                                          */
 690                                         for (bpp = buflist->bs_children;
 691                                              bpp <= endbp; bpp++)
 692                                                 bdwrite(*bpp);
 693                                         kfree(buflist, M_SEGMENT);
 694                                         vp->v_lastw = loffset;
 695                                         vp->v_lasta = bp->b_bio2.bio_offset;
 696                                         return;
 697                                 }
 698                         }
 699                 }
 700                 /*
 701                  * Consider beginning a cluster. If at end of file, make
 702                  * cluster as large as possible, otherwise find size of
 703                  * existing cluster.
 704                  */
 705                 if ((vp->v_type == VREG) &&
 706                     bp->b_loffset + blksize != filesize &&
 707                     (bp->b_bio2.bio_offset == NOOFFSET) &&
 708                     (VOP_BMAP(vp, loffset, &bp->b_bio2.bio_offset, &maxclen, NULL, BUF_CMD_WRITE) ||
 709                      bp->b_bio2.bio_offset == NOOFFSET)) {
 710                         bawrite(bp);
 711                         vp->v_clen = 0;
 712                         vp->v_lasta = bp->b_bio2.bio_offset;
 713                         vp->v_cstart = loffset + blksize;
 714                         vp->v_lastw = loffset;
 715                         return;
 716                 }
 717                 if (maxclen > blksize)
 718                         vp->v_clen = maxclen - blksize;
 719                 else
 720                         vp->v_clen = 0;
 721                 if (!async && vp->v_clen == 0) { /* I/O not contiguous */
 722                         vp->v_cstart = loffset + blksize;
 723                         bawrite(bp);
 724                 } else {        /* Wait for rest of cluster */
 725                         vp->v_cstart = loffset;
 726                         bdwrite(bp);
 727                 }
 728         } else if (loffset == vp->v_cstart + vp->v_clen) {
 729                 /*
 730                  * At end of cluster, write it out if seqcount tells us we
 731                  * are operating sequentially, otherwise let the buf or
 732                  * update daemon handle it.
 733                  */
 734                 bdwrite(bp);
 735                 if (seqcount > 1)
 736                         cluster_wbuild_wb(vp, blksize, vp->v_cstart,
 737                                           vp->v_clen + blksize);
 738                 vp->v_clen = 0;
 739                 vp->v_cstart = loffset + blksize;
 740         } else if (vm_page_count_severe()) {
 741                 /*
 742                  * We are low on memory, get it going NOW
 743                  */
 744                 bawrite(bp);
 745         } else {
 746                 /*
 747                  * In the middle of a cluster, so just delay the I/O for now.
 748                  */
 749                 bdwrite(bp);
 750         }
 751         vp->v_lastw = loffset;
 752         vp->v_lasta = bp->b_bio2.bio_offset;
 753 }
 754
 755
 756 /*
 757  * This is an awful lot like cluster_rbuild...wish they could be combined.
 758  * The last lbn argument is the current block on which I/O is being
 759  * performed.  Check to see that it doesn't fall in the middle of
 760  * the current block (if last_bp == NULL).
 761  */
 762 int
 763 cluster_wbuild(struct vnode *vp, int blksize, off_t start_loffset, int bytes)
 764 {
 765         struct buf *bp, *tbp;
 766         int i, j;
 767         int totalwritten = 0;
 768         int maxiosize = vmaxiosize(vp);
 769
 770         while (bytes > 0) {
 771                 /*
 772                  * If the buffer is not delayed-write (i.e. dirty), or it
 773                  * is delayed-write but either locked or inval, it cannot
 774                  * partake in the clustered write.
 775                  */
 776                 tbp = findblk(vp, start_loffset, FINDBLK_NBLOCK);
 777                 if (tbp == NULL ||
 778                     (tbp->b_flags & (B_LOCKED | B_INVAL | B_DELWRI)) != B_DELWRI ||
 779                     (LIST_FIRST(&tbp->b_dep) && buf_checkwrite(tbp))) {
 780                         if (tbp)
 781                                 BUF_UNLOCK(tbp);
 782                         start_loffset += blksize;
 783                         bytes -= blksize;
 784                         continue;
 785                 }
 786                 bremfree(tbp);
 787                 KKASSERT(tbp->b_cmd == BUF_CMD_DONE);
 788
 789                 /*
 790                  * Extra memory in the buffer, punt on this buffer.
 791                  * XXX we could handle this in most cases, but we would
 792                  * have to push the extra memory down to after our max
 793                  * possible cluster size and then potentially pull it back
 794                  * up if the cluster was terminated prematurely--too much
 795                  * hassle.
 796                  */
 797                 if (((tbp->b_flags & (B_CLUSTEROK|B_MALLOC)) != B_CLUSTEROK) ||
 798                     (tbp->b_bcount != tbp->b_bufsize) ||
 799                     (tbp->b_bcount != blksize) ||
 800                     (bytes == blksize) ||
 801                     ((bp = getpbuf(&cluster_pbuf_freecnt)) == NULL)) {
 802                         totalwritten += tbp->b_bufsize;
 803                         bawrite(tbp);
 804                         start_loffset += blksize;
 805                         bytes -= blksize;
 806                         continue;
 807                 }
 808
 809                 /*
 810                  * Set up the pbuf.  Track our append point with b_bcount
 811                  * and b_bufsize.  b_bufsize is not used by the device but
 812                  * our caller uses it to loop clusters and we use it to
 813                  * detect a premature EOF on the block device.
 814                  */
 815                 bp->b_bcount = 0;
 816                 bp->b_bufsize = 0;
 817                 bp->b_xio.xio_npages = 0;
 818                 bp->b_loffset = tbp->b_loffset;
 819                 bp->b_bio2.bio_offset = tbp->b_bio2.bio_offset;
 820
 821                 /*
 822                  * We are synthesizing a buffer out of vm_page_t's, but
 823                  * if the block size is not page aligned then the starting
 824                  * address may not be either.  Inherit the b_data offset
 825                  * from the original buffer.
 826                  */
 827                 bp->b_data = (char *)((vm_offset_t)bp->b_data |
 828                     ((vm_offset_t)tbp->b_data & PAGE_MASK));
 829                 bp->b_flags &= ~B_ERROR;
 830                 bp->b_flags |= B_CLUSTER | B_BNOCLIP |
 831                         (tbp->b_flags & (B_VMIO | B_NEEDCOMMIT));
 832                 bp->b_bio1.bio_caller_info1.cluster_head = NULL;
 833                 bp->b_bio1.bio_caller_info2.cluster_tail = NULL;
 834
 835                 /*
 836                  * From this location in the file, scan forward to see
 837                  * if there are buffers with adjacent data that need to
 838                  * be written as well.
 839                  */
 840                 for (i = 0; i < bytes; (i += blksize), (start_loffset += blksize)) {
 841                         if (i != 0) { /* If not the first buffer */
 842                                 tbp = findblk(vp, start_loffset,
 843                                               FINDBLK_NBLOCK);
 844                                 /*
 845                                  * Buffer not found or could not be locked
 846                                  * non-blocking.
 847                                  */
 848                                 if (tbp == NULL)
 849                                         break;
 850
 851                                 /*
 852                                  * If it IS in core, but has different
 853                                  * characteristics, then don't cluster
 854                                  * with it.
 855                                  */
 856                                 if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
 857                                      B_INVAL | B_DELWRI | B_NEEDCOMMIT))
 858                                     != (B_DELWRI | B_CLUSTEROK |
 859                                      (bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
 860                                     (tbp->b_flags & B_LOCKED) ||
 861                                     (LIST_FIRST(&tbp->b_dep) &&
 862                                      buf_checkwrite(tbp))
 863                                 ) {
 864                                         BUF_UNLOCK(tbp);
 865                                         break;
 866                                 }
 867
 868                                 /*
 869                                  * Check that the combined cluster
 870                                  * would make sense with regard to pages
 871                                  * and would not be too large
 872                                  */
 873                                 if ((tbp->b_bcount != blksize) ||
 874                                   ((bp->b_bio2.bio_offset + i) !=
 875                                     tbp->b_bio2.bio_offset) ||
 876                                   ((tbp->b_xio.xio_npages + bp->b_xio.xio_npages) >
 877                                     (maxiosize / PAGE_SIZE))) {
 878                                         BUF_UNLOCK(tbp);
 879                                         break;
 880                                 }
 881                                 /*
 882                                  * Ok, it's passed all the tests,
 883                                  * so remove it from the free list
 884                                  * and mark it busy. We will use it.
 885                                  */
 886                                 bremfree(tbp);
 887                                 KKASSERT(tbp->b_cmd == BUF_CMD_DONE);
 888                         } /* end of code for non-first buffers only */
 889
 890                         /*
 891                          * If the IO is via the VM then we do some
 892                          * special VM hackery (yuck).  Since the buffer's
 893                          * block size may not be page-aligned it is possible
 894                          * for a page to be shared between two buffers.  We
 895                          * have to get rid of the duplication when building
 896                          * the cluster.
 897                          */
 898                         if (tbp->b_flags & B_VMIO) {
 899                                 vm_page_t m;
 900
 901                                 if (i != 0) { /* if not first buffer */
 902                                         for (j = 0; j < tbp->b_xio.xio_npages; ++j) {
 903                                                 m = tbp->b_xio.xio_pages[j];
 904                                                 if (m->flags & PG_BUSY) {
 905                                                         bqrelse(tbp);
 906                                                         goto finishcluster;
 907                                                 }
 908                                         }
 909                                 }
 910
 911                                 for (j = 0; j < tbp->b_xio.xio_npages; ++j) {
 912                                         m = tbp->b_xio.xio_pages[j];
 913                                         vm_page_io_start(m);
 914                                         vm_object_pip_add(m->object, 1);
 915                                         if ((bp->b_xio.xio_npages == 0) ||
 916                                           (bp->b_xio.xio_pages[bp->b_xio.xio_npages - 1] != m)) {
 917                                                 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m;
 918                                                 bp->b_xio.xio_npages++;
 919                                         }
 920                                 }
 921                         }
 922                         bp->b_bcount += blksize;
 923                         bp->b_bufsize += blksize;
 924
 925                         bundirty(tbp);
 926                         tbp->b_flags &= ~B_ERROR;
 927                         tbp->b_cmd = BUF_CMD_WRITE;
 928                         BUF_KERNPROC(tbp);
 929                         cluster_append(&bp->b_bio1, tbp);
 930
 931                         /*
 932                          * check for latent dependencies to be handled
 933                          */
 934                         if (LIST_FIRST(&tbp->b_dep) != NULL)
 935                                 buf_start(tbp);
 936                 }
 937         finishcluster:
 938                 pmap_qenter(trunc_page((vm_offset_t) bp->b_data),
 939                         (vm_page_t *) bp->b_xio.xio_pages, bp->b_xio.xio_npages);
 940                 if (bp->b_bufsize > bp->b_kvasize) {
 941                         panic(
 942                             "cluster_wbuild: b_bufsize(%d) > b_kvasize(%d)\n",
 943                             bp->b_bufsize, bp->b_kvasize);
 944                 }
 945                 totalwritten += bp->b_bufsize;
 946                 bp->b_dirtyoff = 0;
 947                 bp->b_dirtyend = bp->b_bufsize;
 948                 bp->b_bio1.bio_done = cluster_callback;
 949                 bp->b_cmd = BUF_CMD_WRITE;
 950
 951                 vfs_busy_pages(vp, bp);
 952                 bp->b_runningbufspace = bp->b_bufsize;
 953                 if (bp->b_runningbufspace) {
 954                         runningbufspace += bp->b_runningbufspace;
 955                         ++runningbufcount;
 956                 }
 957                 BUF_KERNPROC(bp);
 958                 vn_strategy(vp, &bp->b_bio1);
 959
 960                 bytes -= i;
 961         }
 962         return totalwritten;
 963 }
 964
 965 /*
 966  * Collect together all the buffers in a cluster.
 967  * Plus add one additional buffer.
 968  */
 969 static struct cluster_save *
 970 cluster_collectbufs(struct vnode *vp, struct buf *last_bp, int blksize)
 971 {
 972         struct cluster_save *buflist;
 973         struct buf *bp;
 974         off_t loffset;
 975         int i, len;
 976
 977         len = (int)(vp->v_lastw - vp->v_cstart + blksize) / blksize;
 978         buflist = kmalloc(sizeof(struct buf *) * (len + 1) + sizeof(*buflist),
 979                          M_SEGMENT, M_WAITOK);
 980         buflist->bs_nchildren = 0;
 981         buflist->bs_children = (struct buf **) (buflist + 1);
 982         for (loffset = vp->v_cstart, i = 0; i < len; (loffset += blksize), i++) {
 983                 (void) bread(vp, loffset, last_bp->b_bcount, &bp);
 984                 buflist->bs_children[i] = bp;
 985                 if (bp->b_bio2.bio_offset == NOOFFSET) {
 986                         VOP_BMAP(bp->b_vp, bp->b_loffset,
 987                                  &bp->b_bio2.bio_offset,
 988                                  NULL, NULL, BUF_CMD_WRITE);
 989                 }
 990         }
 991         buflist->bs_children[i] = bp = last_bp;
 992         if (bp->b_bio2.bio_offset == NOOFFSET) {
 993                 VOP_BMAP(bp->b_vp, bp->b_loffset, &bp->b_bio2.bio_offset,
 994                          NULL, NULL, BUF_CMD_WRITE);
 995         }
 996         buflist->bs_nchildren = i + 1;
 997         return (buflist);
 998 }
 999
1000 void
1001 cluster_append(struct bio *bio, struct buf *tbp)
1002 {
1003         tbp->b_cluster_next = NULL;
1004         if (bio->bio_caller_info1.cluster_head == NULL) {
1005                 bio->bio_caller_info1.cluster_head = tbp;
1006                 bio->bio_caller_info2.cluster_tail = tbp;
1007         } else {
1008                 bio->bio_caller_info2.cluster_tail->b_cluster_next = tbp;
1009                 bio->bio_caller_info2.cluster_tail = tbp;
1010         }
1011 }
1012