sys/vfs/hammer/hammer_flusher.c

   1 /*
   2  * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   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  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * $DragonFly: src/sys/vfs/hammer/hammer_flusher.c,v 1.40.2.5 2008/08/02 21:24:28 dillon Exp $
  35  */
  36 /*
  37  * HAMMER dependancy flusher thread
  38  *
  39  * Meta data updates create buffer dependancies which are arranged as a
  40  * hierarchy of lists.
  41  */
  42
  43 #include "hammer.h"
  44
  45 static void hammer_flusher_master_thread(void *arg);
  46 static void hammer_flusher_slave_thread(void *arg);
  47 static void hammer_flusher_flush(hammer_mount_t hmp);
  48 static void hammer_flusher_flush_inode(hammer_inode_t ip,
  49                                         hammer_transaction_t trans);
  50
  51 /*
  52  * Support structures for the flusher threads.
  53  */
  54 struct hammer_flusher_info {
  55         TAILQ_ENTRY(hammer_flusher_info) entry;
  56         struct hammer_mount *hmp;
  57         thread_t        td;
  58         int             runstate;
  59         int             count;
  60         hammer_flush_group_t flg;
  61         hammer_inode_t  work_array[HAMMER_FLUSH_GROUP_SIZE];
  62 };
  63
  64 typedef struct hammer_flusher_info *hammer_flusher_info_t;
  65
  66 /*
  67  * Sync all inodes pending on the flusher.
  68  *
  69  * All flush groups will be flushed.  This does not queue dirty inodes
  70  * to the flush groups, it just flushes out what has already been queued!
  71  */
  72 void
  73 hammer_flusher_sync(hammer_mount_t hmp)
  74 {
  75         int seq;
  76
  77         seq = hammer_flusher_async(hmp, NULL);
  78         hammer_flusher_wait(hmp, seq);
  79 }
  80
  81 /*
  82  * Sync all inodes pending on the flusher - return immediately.
  83  *
  84  * All flush groups will be flushed.
  85  */
  86 int
  87 hammer_flusher_async(hammer_mount_t hmp, hammer_flush_group_t close_flg)
  88 {
  89         hammer_flush_group_t flg;
  90         int seq = hmp->flusher.next;
  91
  92         TAILQ_FOREACH(flg, &hmp->flush_group_list, flush_entry) {
  93                 if (flg->running == 0)
  94                         ++seq;
  95                 flg->closed = 1;
  96                 if (flg == close_flg)
  97                         break;
  98         }
  99         if (hmp->flusher.td) {
 100                 if (hmp->flusher.signal++ == 0)
 101                         wakeup(&hmp->flusher.signal);
 102         } else {
 103                 seq = hmp->flusher.done;
 104         }
 105         return(seq);
 106 }
 107
 108 int
 109 hammer_flusher_async_one(hammer_mount_t hmp)
 110 {
 111         int seq;
 112
 113         if (hmp->flusher.td) {
 114                 seq = hmp->flusher.next;
 115                 if (hmp->flusher.signal++ == 0)
 116                         wakeup(&hmp->flusher.signal);
 117         } else {
 118                 seq = hmp->flusher.done;
 119         }
 120         return(seq);
 121 }
 122
 123 /*
 124  * Wait for the flusher to get to the specified sequence number.
 125  * Signal the flusher as often as necessary to keep it going.
 126  */
 127 void
 128 hammer_flusher_wait(hammer_mount_t hmp, int seq)
 129 {
 130         while ((int)(seq - hmp->flusher.done) > 0) {
 131                 if (hmp->flusher.act != seq) {
 132                         if (hmp->flusher.signal++ == 0)
 133                                 wakeup(&hmp->flusher.signal);
 134                 }
 135                 tsleep(&hmp->flusher.done, 0, "hmrfls", 0);
 136         }
 137 }
 138
 139 void
 140 hammer_flusher_create(hammer_mount_t hmp)
 141 {
 142         hammer_flusher_info_t info;
 143         int i;
 144
 145         hmp->flusher.signal = 0;
 146         hmp->flusher.act = 0;
 147         hmp->flusher.done = 0;
 148         hmp->flusher.next = 1;
 149         hammer_ref(&hmp->flusher.finalize_lock);
 150         TAILQ_INIT(&hmp->flusher.run_list);
 151         TAILQ_INIT(&hmp->flusher.ready_list);
 152
 153         lwkt_create(hammer_flusher_master_thread, hmp,
 154                     &hmp->flusher.td, NULL, 0, -1, "hammer-M");
 155         for (i = 0; i < HAMMER_MAX_FLUSHERS; ++i) {
 156                 info = kmalloc(sizeof(*info), M_HAMMER, M_WAITOK|M_ZERO);
 157                 info->hmp = hmp;
 158                 TAILQ_INSERT_TAIL(&hmp->flusher.ready_list, info, entry);
 159                 lwkt_create(hammer_flusher_slave_thread, info,
 160                             &info->td, NULL, 0, -1, "hammer-S%d", i);
 161         }
 162 }
 163
 164 void
 165 hammer_flusher_destroy(hammer_mount_t hmp)
 166 {
 167         hammer_flusher_info_t info;
 168
 169         /*
 170          * Kill the master
 171          */
 172         hmp->flusher.exiting = 1;
 173         while (hmp->flusher.td) {
 174                 ++hmp->flusher.signal;
 175                 wakeup(&hmp->flusher.signal);
 176                 tsleep(&hmp->flusher.exiting, 0, "hmrwex", hz);
 177         }
 178
 179         /*
 180          * Kill the slaves
 181          */
 182         while ((info = TAILQ_FIRST(&hmp->flusher.ready_list)) != NULL) {
 183                 KKASSERT(info->runstate == 0);
 184                 TAILQ_REMOVE(&hmp->flusher.ready_list, info, entry);
 185                 info->runstate = -1;
 186                 wakeup(&info->runstate);
 187                 while (info->td)
 188                         tsleep(&info->td, 0, "hmrwwc", 0);
 189                 TAILQ_REMOVE(&hmp->flusher.ready_list, info, entry);
 190                 kfree(info, M_HAMMER);
 191         }
 192 }
 193
 194 /*
 195  * The master flusher thread manages the flusher sequence id and
 196  * synchronization with the slave work threads.
 197  */
 198 static void
 199 hammer_flusher_master_thread(void *arg)
 200 {
 201         hammer_flush_group_t flg;
 202         hammer_mount_t hmp;
 203
 204         hmp = arg;
 205
 206         for (;;) {
 207                 /*
 208                  * Do at least one flush cycle.  We may have to update the
 209                  * UNDO FIFO even if no inodes are queued.
 210                  */
 211                 for (;;) {
 212                         while (hmp->flusher.group_lock)
 213                                 tsleep(&hmp->flusher.group_lock, 0, "hmrhld", 0);
 214                         hmp->flusher.act = hmp->flusher.next;
 215                         ++hmp->flusher.next;
 216                         hammer_flusher_clean_loose_ios(hmp);
 217                         hammer_flusher_flush(hmp);
 218                         hmp->flusher.done = hmp->flusher.act;
 219                         wakeup(&hmp->flusher.done);
 220                         flg = TAILQ_FIRST(&hmp->flush_group_list);
 221                         if (flg == NULL || flg->closed == 0)
 222                                 break;
 223                         if (hmp->flags & HAMMER_MOUNT_CRITICAL_ERROR)
 224                                 break;
 225                 }
 226
 227                 /*
 228                  * Wait for activity.
 229                  */
 230                 if (hmp->flusher.exiting && TAILQ_EMPTY(&hmp->flush_group_list))
 231                         break;
 232                 while (hmp->flusher.signal == 0)
 233                         tsleep(&hmp->flusher.signal, 0, "hmrwwa", 0);
 234
 235                 /*
 236                  * Flush for each count on signal but only allow one extra
 237                  * flush request to build up.
 238                  */
 239                 if (--hmp->flusher.signal != 0)
 240                         hmp->flusher.signal = 1;
 241         }
 242
 243         /*
 244          * And we are done.
 245          */
 246         hmp->flusher.td = NULL;
 247         wakeup(&hmp->flusher.exiting);
 248         lwkt_exit();
 249 }
 250
 251 /*
 252  * Flush all inodes in the current flush group.
 253  */
 254 static void
 255 hammer_flusher_flush(hammer_mount_t hmp)
 256 {
 257         hammer_flusher_info_t info;
 258         hammer_flush_group_t flg;
 259         hammer_reserve_t resv;
 260         hammer_inode_t ip;
 261         hammer_inode_t next_ip;
 262         int slave_index;
 263         int count;
 264
 265         /*
 266          * Just in-case there's a flush race on mount
 267          */
 268         if (TAILQ_FIRST(&hmp->flusher.ready_list) == NULL)
 269                 return;
 270
 271         /*
 272          * We only do one flg but we may have to loop/retry.
 273          */
 274         count = 0;
 275         while ((flg = TAILQ_FIRST(&hmp->flush_group_list)) != NULL) {
 276                 ++count;
 277                 if (hammer_debug_general & 0x0001) {
 278                         kprintf("hammer_flush %d ttl=%d recs=%d\n",
 279                                 hmp->flusher.act,
 280                                 flg->total_count, flg->refs);
 281                 }
 282                 if (hmp->flags & HAMMER_MOUNT_CRITICAL_ERROR)
 283                         break;
 284                 hammer_start_transaction_fls(&hmp->flusher.trans, hmp);
 285
 286                 /*
 287                  * If the previous flush cycle just about exhausted our
 288                  * UNDO space we may have to do a dummy cycle to move the
 289                  * first_offset up before actually digging into a new cycle,
 290                  * or the new cycle will not have sufficient undo space.
 291                  */
 292                 if (hammer_flusher_undo_exhausted(&hmp->flusher.trans, 3))
 293                         hammer_flusher_finalize(&hmp->flusher.trans, 0);
 294
 295                 /*
 296                  * Ok, we are running this flush group now (this prevents new
 297                  * additions to it).
 298                  */
 299                 flg->running = 1;
 300                 if (hmp->next_flush_group == flg)
 301                         hmp->next_flush_group = TAILQ_NEXT(flg, flush_entry);
 302
 303                 /*
 304                  * Iterate the inodes in the flg's flush_list and assign
 305                  * them to slaves.
 306                  */
 307                 slave_index = 0;
 308                 info = TAILQ_FIRST(&hmp->flusher.ready_list);
 309                 next_ip = TAILQ_FIRST(&flg->flush_list);
 310
 311                 while ((ip = next_ip) != NULL) {
 312                         next_ip = TAILQ_NEXT(ip, flush_entry);
 313
 314                         /*
 315                          * Add ip to the slave's work array.  The slave is
 316                          * not currently running.
 317                          */
 318                         info->work_array[info->count++] = ip;
 319                         if (info->count != HAMMER_FLUSH_GROUP_SIZE)
 320                                 continue;
 321
 322                         /*
 323                          * Get the slave running
 324                          */
 325                         TAILQ_REMOVE(&hmp->flusher.ready_list, info, entry);
 326                         TAILQ_INSERT_TAIL(&hmp->flusher.run_list, info, entry);
 327                         info->flg = flg;
 328                         info->runstate = 1;
 329                         wakeup(&info->runstate);
 330
 331                         /*
 332                          * Get a new slave.  We may have to wait for one to
 333                          * finish running.
 334                          */
 335                         while ((info = TAILQ_FIRST(&hmp->flusher.ready_list)) == NULL) {
 336                                 tsleep(&hmp->flusher.ready_list, 0, "hmrfcc", 0);
 337                         }
 338                 }
 339
 340                 /*
 341                  * Run the current slave if necessary
 342                  */
 343                 if (info->count) {
 344                         TAILQ_REMOVE(&hmp->flusher.ready_list, info, entry);
 345                         TAILQ_INSERT_TAIL(&hmp->flusher.run_list, info, entry);
 346                         info->flg = flg;
 347                         info->runstate = 1;
 348                         wakeup(&info->runstate);
 349                 }
 350
 351                 /*
 352                  * Wait for all slaves to finish running
 353                  */
 354                 while (TAILQ_FIRST(&hmp->flusher.run_list) != NULL)
 355                         tsleep(&hmp->flusher.ready_list, 0, "hmrfcc", 0);
 356
 357                 /*
 358                  * Do the final finalization, clean up
 359                  */
 360                 hammer_flusher_finalize(&hmp->flusher.trans, 1);
 361                 hmp->flusher.tid = hmp->flusher.trans.tid;
 362
 363                 hammer_done_transaction(&hmp->flusher.trans);
 364
 365                 /*
 366                  * Loop up on the same flg.  If the flg is done clean it up
 367                  * and break out.  We only flush one flg.
 368                  */
 369                 if (TAILQ_FIRST(&flg->flush_list) == NULL) {
 370                         KKASSERT(TAILQ_EMPTY(&flg->flush_list));
 371                         KKASSERT(flg->refs == 0);
 372                         TAILQ_REMOVE(&hmp->flush_group_list, flg, flush_entry);
 373                         kfree(flg, M_HAMMER);
 374                         break;
 375                 }
 376         }
 377
 378         /*
 379          * We may have pure meta-data to flush, or we may have to finish
 380          * cycling the UNDO FIFO, even if there were no flush groups.
 381          */
 382         if (count == 0 && hammer_flusher_haswork(hmp)) {
 383                 hammer_start_transaction_fls(&hmp->flusher.trans, hmp);
 384                 hammer_flusher_finalize(&hmp->flusher.trans, 1);
 385                 hammer_done_transaction(&hmp->flusher.trans);
 386         }
 387
 388         /*
 389          * Clean up any freed big-blocks (typically zone-2).
 390          * resv->flush_group is typically set several flush groups ahead
 391          * of the free to ensure that the freed block is not reused until
 392          * it can no longer be reused.
 393          */
 394         while ((resv = TAILQ_FIRST(&hmp->delay_list)) != NULL) {
 395                 if (resv->flush_group != hmp->flusher.act)
 396                         break;
 397                 hammer_reserve_clrdelay(hmp, resv);
 398         }
 399 }
 400
 401
 402 /*
 403  * The slave flusher thread pulls work off the master flush_list until no
 404  * work is left.
 405  */
 406 static void
 407 hammer_flusher_slave_thread(void *arg)
 408 {
 409         hammer_flush_group_t flg;
 410         hammer_flusher_info_t info;
 411         hammer_mount_t hmp;
 412         hammer_inode_t ip;
 413         int i;
 414
 415         info = arg;
 416         hmp = info->hmp;
 417
 418         for (;;) {
 419                 while (info->runstate == 0)
 420                         tsleep(&info->runstate, 0, "hmrssw", 0);
 421                 if (info->runstate < 0)
 422                         break;
 423                 flg = info->flg;
 424
 425                 for (i = 0; i < info->count; ++i) {
 426                         ip = info->work_array[i];
 427                         hammer_flusher_flush_inode(ip, &hmp->flusher.trans);
 428                         ++hammer_stats_inode_flushes;
 429                 }
 430                 info->count = 0;
 431                 info->runstate = 0;
 432                 TAILQ_REMOVE(&hmp->flusher.run_list, info, entry);
 433                 TAILQ_INSERT_TAIL(&hmp->flusher.ready_list, info, entry);
 434                 wakeup(&hmp->flusher.ready_list);
 435         }
 436         info->td = NULL;
 437         wakeup(&info->td);
 438         lwkt_exit();
 439 }
 440
 441 void
 442 hammer_flusher_clean_loose_ios(hammer_mount_t hmp)
 443 {
 444         hammer_buffer_t buffer;
 445         hammer_io_t io;
 446
 447         /*
 448          * loose ends - buffers without bp's aren't tracked by the kernel
 449          * and can build up, so clean them out.  This can occur when an
 450          * IO completes on a buffer with no references left.
 451          */
 452         if ((io = TAILQ_FIRST(&hmp->lose_list)) != NULL) {
 453                 crit_enter();   /* biodone() race */
 454                 while ((io = TAILQ_FIRST(&hmp->lose_list)) != NULL) {
 455                         KKASSERT(io->mod_list == &hmp->lose_list);
 456                         TAILQ_REMOVE(&hmp->lose_list, io, mod_entry);
 457                         io->mod_list = NULL;
 458                         if (io->lock.refs == 0)
 459                                 ++hammer_count_refedbufs;
 460                         hammer_ref(&io->lock);
 461                         buffer = (void *)io;
 462                         hammer_rel_buffer(buffer, 0);
 463                 }
 464                 crit_exit();
 465         }
 466 }
 467
 468 /*
 469  * Flush a single inode that is part of a flush group.
 470  *
 471  * Flusher errors are extremely serious, even ENOSPC shouldn't occur because
 472  * the front-end should have reserved sufficient space on the media.  Any
 473  * error other then EWOULDBLOCK will force the mount to be read-only.
 474  */
 475 static
 476 void
 477 hammer_flusher_flush_inode(hammer_inode_t ip, hammer_transaction_t trans)
 478 {
 479         hammer_mount_t hmp = ip->hmp;
 480         int error;
 481
 482         hammer_flusher_clean_loose_ios(hmp);
 483         error = hammer_sync_inode(trans, ip);
 484
 485         /*
 486          * EWOULDBLOCK can happen under normal operation, all other errors
 487          * are considered extremely serious.  We must set WOULDBLOCK
 488          * mechanics to deal with the mess left over from the abort of the
 489          * previous flush.
 490          */
 491         if (error) {
 492                 ip->flags |= HAMMER_INODE_WOULDBLOCK;
 493                 if (error == EWOULDBLOCK)
 494                         error = 0;
 495         }
 496         hammer_flush_inode_done(ip, error);
 497         while (hmp->flusher.finalize_want)
 498                 tsleep(&hmp->flusher.finalize_want, 0, "hmrsxx", 0);
 499         if (hammer_flusher_undo_exhausted(trans, 1)) {
 500                 kprintf("HAMMER: Warning: UNDO area too small!\n");
 501                 hammer_flusher_finalize(trans, 1);
 502         } else if (hammer_flusher_meta_limit(trans->hmp)) {
 503                 hammer_flusher_finalize(trans, 0);
 504         }
 505 }
 506
 507 /*
 508  * Return non-zero if the UNDO area has less then (QUARTER / 4) of its
 509  * space left.
 510  *
 511  * 1/4 - Emergency free undo space level.  Below this point the flusher
 512  *       will finalize even if directory dependancies have not been resolved.
 513  *
 514  * 2/4 - Used by the pruning and reblocking code.  These functions may be
 515  *       running in parallel with a flush and cannot be allowed to drop
 516  *       available undo space to emergency levels.
 517  *
 518  * 3/4 - Used at the beginning of a flush to force-sync the volume header
 519  *       to give the flush plenty of runway to work in.
 520  */
 521 int
 522 hammer_flusher_undo_exhausted(hammer_transaction_t trans, int quarter)
 523 {
 524         if (hammer_undo_space(trans) <
 525             hammer_undo_max(trans->hmp) * quarter / 4) {
 526                 return(1);
 527         } else {
 528                 return(0);
 529         }
 530 }
 531
 532 /*
 533  * Flush all pending UNDOs, wait for write completion, update the volume
 534  * header with the new UNDO end position, and flush it.  Then
 535  * asynchronously flush the meta-data.
 536  *
 537  * If this is the last finalization in a flush group we also synchronize
 538  * our cached blockmap and set hmp->flusher_undo_start and our cached undo
 539  * fifo first_offset so the next flush resets the FIFO pointers.
 540  *
 541  * If this is not final it is being called because too many dirty meta-data
 542  * buffers have built up and must be flushed with UNDO synchronization to
 543  * avoid a buffer cache deadlock.
 544  */
 545 void
 546 hammer_flusher_finalize(hammer_transaction_t trans, int final)
 547 {
 548         hammer_volume_t root_volume;
 549         hammer_blockmap_t cundomap, dundomap;
 550         hammer_mount_t hmp;
 551         hammer_io_t io;
 552         int count;
 553         int i;
 554
 555         hmp = trans->hmp;
 556         root_volume = trans->rootvol;
 557
 558         /*
 559          * Exclusively lock the flusher.  This guarantees that all dirty
 560          * buffers will be idled (have a mod-count of 0).
 561          */
 562         ++hmp->flusher.finalize_want;
 563         hammer_lock_ex(&hmp->flusher.finalize_lock);
 564
 565         /*
 566          * If this isn't the final sync several threads may have hit the
 567          * meta-limit at the same time and raced.  Only sync if we really
 568          * have to, after acquiring the lock.
 569          */
 570         if (final == 0 && !hammer_flusher_meta_limit(hmp))
 571                 goto done;
 572
 573         if (hmp->flags & HAMMER_MOUNT_CRITICAL_ERROR)
 574                 goto done;
 575
 576         /*
 577          * Flush data buffers.  This can occur asynchronously and at any
 578          * time.  We must interlock against the frontend direct-data write
 579          * but do not have to acquire the sync-lock yet.
 580          */
 581         count = 0;
 582         while ((io = TAILQ_FIRST(&hmp->data_list)) != NULL) {
 583                 if (io->ioerror)
 584                         break;
 585                 if (io->lock.refs == 0)
 586                         ++hammer_count_refedbufs;
 587                 hammer_ref(&io->lock);
 588                 hammer_io_write_interlock(io);
 589                 KKASSERT(io->type != HAMMER_STRUCTURE_VOLUME);
 590                 hammer_io_flush(io);
 591                 hammer_io_done_interlock(io);
 592                 hammer_rel_buffer((hammer_buffer_t)io, 0);
 593                 ++count;
 594         }
 595
 596         /*
 597          * The sync-lock is required for the remaining sequence.  This lock
 598          * prevents meta-data from being modified.
 599          */
 600         hammer_sync_lock_ex(trans);
 601
 602         /*
 603          * If we have been asked to finalize the volume header sync the
 604          * cached blockmap to the on-disk blockmap.  Generate an UNDO
 605          * record for the update.
 606          */
 607         if (final) {
 608                 cundomap = &hmp->blockmap[0];
 609                 dundomap = &root_volume->ondisk->vol0_blockmap[0];
 610                 if (root_volume->io.modified) {
 611                         hammer_modify_volume(trans, root_volume,
 612                                              dundomap, sizeof(hmp->blockmap));
 613                         for (i = 0; i < HAMMER_MAX_ZONES; ++i)
 614                                 hammer_crc_set_blockmap(&cundomap[i]);
 615                         bcopy(cundomap, dundomap, sizeof(hmp->blockmap));
 616                         hammer_modify_volume_done(root_volume);
 617                 }
 618         }
 619
 620         /*
 621          * Flush UNDOs
 622          */
 623         count = 0;
 624         while ((io = TAILQ_FIRST(&hmp->undo_list)) != NULL) {
 625                 if (io->ioerror)
 626                         break;
 627                 KKASSERT(io->modify_refs == 0);
 628                 if (io->lock.refs == 0)
 629                         ++hammer_count_refedbufs;
 630                 hammer_ref(&io->lock);
 631                 KKASSERT(io->type != HAMMER_STRUCTURE_VOLUME);
 632                 hammer_io_flush(io);
 633                 hammer_rel_buffer((hammer_buffer_t)io, 0);
 634                 ++count;
 635         }
 636
 637         /*
 638          * Wait for I/Os to complete
 639          */
 640         hammer_flusher_clean_loose_ios(hmp);
 641         hammer_io_wait_all(hmp, "hmrfl1");
 642
 643         if (hmp->flags & HAMMER_MOUNT_CRITICAL_ERROR)
 644                 goto failed;
 645
 646         /*
 647          * Update the on-disk volume header with new UNDO FIFO end position
 648          * (do not generate new UNDO records for this change).  We have to
 649          * do this for the UNDO FIFO whether (final) is set or not.
 650          *
 651          * Also update the on-disk next_tid field.  This does not require
 652          * an UNDO.  However, because our TID is generated before we get
 653          * the sync lock another sync may have beat us to the punch.
 654          *
 655          * This also has the side effect of updating first_offset based on
 656          * a prior finalization when the first finalization of the next flush
 657          * cycle occurs, removing any undo info from the prior finalization
 658          * from consideration.
 659          *
 660          * The volume header will be flushed out synchronously.
 661          */
 662         dundomap = &root_volume->ondisk->vol0_blockmap[HAMMER_ZONE_UNDO_INDEX];
 663         cundomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
 664
 665         if (dundomap->first_offset != cundomap->first_offset ||
 666                    dundomap->next_offset != cundomap->next_offset) {
 667                 hammer_modify_volume(NULL, root_volume, NULL, 0);
 668                 dundomap->first_offset = cundomap->first_offset;
 669                 dundomap->next_offset = cundomap->next_offset;
 670                 hammer_crc_set_blockmap(dundomap);
 671                 hammer_modify_volume_done(root_volume);
 672         }
 673
 674         /*
 675          * vol0_next_tid is used for TID selection and is updated without
 676          * an UNDO so we do not reuse a TID that may have been rolled-back.
 677          *
 678          * vol0_last_tid is the highest fully-synchronized TID.  It is
 679          * set-up when the UNDO fifo is fully synced, later on (not here).
 680          */
 681         if (root_volume->io.modified) {
 682                 hammer_modify_volume(NULL, root_volume, NULL, 0);
 683                 if (root_volume->ondisk->vol0_next_tid < trans->tid)
 684                         root_volume->ondisk->vol0_next_tid = trans->tid;
 685                 hammer_crc_set_volume(root_volume->ondisk);
 686                 hammer_modify_volume_done(root_volume);
 687                 hammer_io_flush(&root_volume->io);
 688         }
 689
 690         /*
 691          * Wait for I/Os to complete
 692          */
 693         hammer_flusher_clean_loose_ios(hmp);
 694         hammer_io_wait_all(hmp, "hmrfl2");
 695
 696         if (hmp->flags & HAMMER_MOUNT_CRITICAL_ERROR)
 697                 goto failed;
 698
 699         /*
 700          * Flush meta-data.  The meta-data will be undone if we crash
 701          * so we can safely flush it asynchronously.
 702          *
 703          * Repeated catchups will wind up flushing this update's meta-data
 704          * and the UNDO buffers for the next update simultaniously.  This
 705          * is ok.
 706          */
 707         count = 0;
 708         while ((io = TAILQ_FIRST(&hmp->meta_list)) != NULL) {
 709                 if (io->ioerror)
 710                         break;
 711                 KKASSERT(io->modify_refs == 0);
 712                 if (io->lock.refs == 0)
 713                         ++hammer_count_refedbufs;
 714                 hammer_ref(&io->lock);
 715                 KKASSERT(io->type != HAMMER_STRUCTURE_VOLUME);
 716                 hammer_io_flush(io);
 717                 hammer_rel_buffer((hammer_buffer_t)io, 0);
 718                 ++count;
 719         }
 720
 721         /*
 722          * If this is the final finalization for the flush group set
 723          * up for the next sequence by setting a new first_offset in
 724          * our cached blockmap and clearing the undo history.
 725          *
 726          * Even though we have updated our cached first_offset, the on-disk
 727          * first_offset still governs available-undo-space calculations.
 728          */
 729         if (final) {
 730                 cundomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
 731                 if (cundomap->first_offset == cundomap->next_offset) {
 732                         hmp->hflags &= ~HMNT_UNDO_DIRTY;
 733                 } else {
 734                         cundomap->first_offset = cundomap->next_offset;
 735                         hmp->hflags |= HMNT_UNDO_DIRTY;
 736                 }
 737                 hammer_clear_undo_history(hmp);
 738
 739                 /*
 740                  * Flush tid sequencing.  flush_tid1 is fully synchronized,
 741                  * meaning a crash will not roll it back.  flush_tid2 has
 742                  * been written out asynchronously and a crash will roll
 743                  * it back.  flush_tid1 is used for all mirroring masters.
 744                  */
 745                 if (hmp->flush_tid1 != hmp->flush_tid2) {
 746                         hmp->flush_tid1 = hmp->flush_tid2;
 747                         wakeup(&hmp->flush_tid1);
 748                 }
 749                 hmp->flush_tid2 = trans->tid;
 750         }
 751
 752         /*
 753          * Cleanup.  Report any critical errors.
 754          */
 755 failed:
 756         hammer_sync_unlock(trans);
 757
 758         if (hmp->flags & HAMMER_MOUNT_CRITICAL_ERROR) {
 759                 kprintf("HAMMER(%s): Critical write error during flush, "
 760                         "refusing to sync UNDO FIFO\n",
 761                         root_volume->ondisk->vol_name);
 762         }
 763
 764 done:
 765         hammer_unlock(&hmp->flusher.finalize_lock);
 766
 767         if (--hmp->flusher.finalize_want == 0)
 768                 wakeup(&hmp->flusher.finalize_want);
 769         hammer_stats_commits += final;
 770 }
 771
 772 /*
 773  * Return non-zero if too many dirty meta-data buffers have built up.
 774  *
 775  * Since we cannot allow such buffers to flush until we have dealt with
 776  * the UNDOs, we risk deadlocking the kernel's buffer cache.
 777  */
 778 int
 779 hammer_flusher_meta_limit(hammer_mount_t hmp)
 780 {
 781         if (hmp->locked_dirty_space + hmp->io_running_space >
 782             hammer_limit_dirtybufspace) {
 783                 return(1);
 784         }
 785         return(0);
 786 }
 787
 788 /*
 789  * Return non-zero if too many dirty meta-data buffers have built up.
 790  *
 791  * This version is used by background operations (mirror, prune, reblock)
 792  * to leave room for foreground operations.
 793  */
 794 int
 795 hammer_flusher_meta_halflimit(hammer_mount_t hmp)
 796 {
 797         if (hmp->locked_dirty_space + hmp->io_running_space >
 798             hammer_limit_dirtybufspace / 2) {
 799                 return(1);
 800         }
 801         return(0);
 802 }
 803
 804 /*
 805  * Return non-zero if the flusher still has something to flush.
 806  */
 807 int
 808 hammer_flusher_haswork(hammer_mount_t hmp)
 809 {
 810         if (hmp->flags & HAMMER_MOUNT_CRITICAL_ERROR)
 811                 return(0);
 812         if (TAILQ_FIRST(&hmp->flush_group_list) ||      /* dirty inodes */
 813             TAILQ_FIRST(&hmp->volu_list) ||             /* dirty bufffers */
 814             TAILQ_FIRST(&hmp->undo_list) ||
 815             TAILQ_FIRST(&hmp->data_list) ||
 816             TAILQ_FIRST(&hmp->meta_list) ||
 817             (hmp->hflags & HMNT_UNDO_DIRTY)             /* UNDO FIFO sync */
 818         ) {
 819                 return(1);
 820         }
 821         return(0);
 822 }
 823