fs/jbd/checkpoint.c

   1 /*
   2  * linux/fs/jbd/checkpoint.c
   3  *
   4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
   5  *
   6  * Copyright 1999 Red Hat Software --- All Rights Reserved
   7  *
   8  * This file is part of the Linux kernel and is made available under
   9  * the terms of the GNU General Public License, version 2, or at your
  10  * option, any later version, incorporated herein by reference.
  11  *
  12  * Checkpoint routines for the generic filesystem journaling code.
  13  * Part of the ext2fs journaling system.
  14  *
  15  * Checkpointing is the process of ensuring that a section of the log is
  16  * committed fully to disk, so that that portion of the log can be
  17  * reused.
  18  */
  19
  20 #include <linux/time.h>
  21 #include <linux/fs.h>
  22 #include <linux/jbd.h>
  23 #include <linux/errno.h>
  24 #include <linux/slab.h>
  25
  26 /*
  27  * Unlink a buffer from a transaction checkpoint list.
  28  *
  29  * Called with j_list_lock held.
  30  */
  31 static inline void __buffer_unlink_first(struct journal_head *jh)
  32 {
  33         transaction_t *transaction = jh->b_cp_transaction;
  34
  35         jh->b_cpnext->b_cpprev = jh->b_cpprev;
  36         jh->b_cpprev->b_cpnext = jh->b_cpnext;
  37         if (transaction->t_checkpoint_list == jh) {
  38                 transaction->t_checkpoint_list = jh->b_cpnext;
  39                 if (transaction->t_checkpoint_list == jh)
  40                         transaction->t_checkpoint_list = NULL;
  41         }
  42 }
  43
  44 /*
  45  * Unlink a buffer from a transaction checkpoint(io) list.
  46  *
  47  * Called with j_list_lock held.
  48  */
  49 static inline void __buffer_unlink(struct journal_head *jh)
  50 {
  51         transaction_t *transaction = jh->b_cp_transaction;
  52
  53         __buffer_unlink_first(jh);
  54         if (transaction->t_checkpoint_io_list == jh) {
  55                 transaction->t_checkpoint_io_list = jh->b_cpnext;
  56                 if (transaction->t_checkpoint_io_list == jh)
  57                         transaction->t_checkpoint_io_list = NULL;
  58         }
  59 }
  60
  61 /*
  62  * Move a buffer from the checkpoint list to the checkpoint io list
  63  *
  64  * Called with j_list_lock held
  65  */
  66 static inline void __buffer_relink_io(struct journal_head *jh)
  67 {
  68         transaction_t *transaction = jh->b_cp_transaction;
  69
  70         __buffer_unlink_first(jh);
  71
  72         if (!transaction->t_checkpoint_io_list) {
  73                 jh->b_cpnext = jh->b_cpprev = jh;
  74         } else {
  75                 jh->b_cpnext = transaction->t_checkpoint_io_list;
  76                 jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
  77                 jh->b_cpprev->b_cpnext = jh;
  78                 jh->b_cpnext->b_cpprev = jh;
  79         }
  80         transaction->t_checkpoint_io_list = jh;
  81 }
  82
  83 /*
  84  * Try to release a checkpointed buffer from its transaction.
  85  * Returns 1 if we released it and 2 if we also released the
  86  * whole transaction.
  87  *
  88  * Requires j_list_lock
  89  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  90  */
  91 static int __try_to_free_cp_buf(struct journal_head *jh)
  92 {
  93         int ret = 0;
  94         struct buffer_head *bh = jh2bh(jh);
  95
  96         if (jh->b_jlist == BJ_None && !buffer_locked(bh) &&
  97             !buffer_dirty(bh) && buffer_uptodate(bh)) {
  98                 JBUFFER_TRACE(jh, "remove from checkpoint list");
  99                 ret = __journal_remove_checkpoint(jh) + 1;
 100                 jbd_unlock_bh_state(bh);
 101                 journal_remove_journal_head(bh);
 102                 BUFFER_TRACE(bh, "release");
 103                 __brelse(bh);
 104         } else {
 105                 jbd_unlock_bh_state(bh);
 106         }
 107         return ret;
 108 }
 109
 110 /*
 111  * __log_wait_for_space: wait until there is space in the journal.
 112  *
 113  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
 114  * for a checkpoint to free up some space in the log.
 115  */
 116 void __log_wait_for_space(journal_t *journal)
 117 {
 118         int nblocks;
 119         assert_spin_locked(&journal->j_state_lock);
 120
 121         nblocks = jbd_space_needed(journal);
 122         while (__log_space_left(journal) < nblocks) {
 123                 if (journal->j_flags & JFS_ABORT)
 124                         return;
 125                 spin_unlock(&journal->j_state_lock);
 126                 mutex_lock(&journal->j_checkpoint_mutex);
 127
 128                 /*
 129                  * Test again, another process may have checkpointed while we
 130                  * were waiting for the checkpoint lock
 131                  */
 132                 spin_lock(&journal->j_state_lock);
 133                 nblocks = jbd_space_needed(journal);
 134                 if (__log_space_left(journal) < nblocks) {
 135                         spin_unlock(&journal->j_state_lock);
 136                         log_do_checkpoint(journal);
 137                         spin_lock(&journal->j_state_lock);
 138                 }
 139                 mutex_unlock(&journal->j_checkpoint_mutex);
 140         }
 141 }
 142
 143 /*
 144  * We were unable to perform jbd_trylock_bh_state() inside j_list_lock.
 145  * The caller must restart a list walk.  Wait for someone else to run
 146  * jbd_unlock_bh_state().
 147  */
 148 static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
 149         __releases(journal->j_list_lock)
 150 {
 151         get_bh(bh);
 152         spin_unlock(&journal->j_list_lock);
 153         jbd_lock_bh_state(bh);
 154         jbd_unlock_bh_state(bh);
 155         put_bh(bh);
 156 }
 157
 158 /*
 159  * Clean up transaction's list of buffers submitted for io.
 160  * We wait for any pending IO to complete and remove any clean
 161  * buffers. Note that we take the buffers in the opposite ordering
 162  * from the one in which they were submitted for IO.
 163  *
 164  * Return 0 on success, and return <0 if some buffers have failed
 165  * to be written out.
 166  *
 167  * Called with j_list_lock held.
 168  */
 169 static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
 170 {
 171         struct journal_head *jh;
 172         struct buffer_head *bh;
 173         tid_t this_tid;
 174         int released = 0;
 175         int ret = 0;
 176
 177         this_tid = transaction->t_tid;
 178 restart:
 179         /* Did somebody clean up the transaction in the meanwhile? */
 180         if (journal->j_checkpoint_transactions != transaction ||
 181                         transaction->t_tid != this_tid)
 182                 return ret;
 183         while (!released && transaction->t_checkpoint_io_list) {
 184                 jh = transaction->t_checkpoint_io_list;
 185                 bh = jh2bh(jh);
 186                 if (!jbd_trylock_bh_state(bh)) {
 187                         jbd_sync_bh(journal, bh);
 188                         spin_lock(&journal->j_list_lock);
 189                         goto restart;
 190                 }
 191                 if (buffer_locked(bh)) {
 192                         atomic_inc(&bh->b_count);
 193                         spin_unlock(&journal->j_list_lock);
 194                         jbd_unlock_bh_state(bh);
 195                         wait_on_buffer(bh);
 196                         /* the journal_head may have gone by now */
 197                         BUFFER_TRACE(bh, "brelse");
 198                         __brelse(bh);
 199                         spin_lock(&journal->j_list_lock);
 200                         goto restart;
 201                 }
 202                 if (unlikely(!buffer_uptodate(bh)))
 203                         ret = -EIO;
 204
 205                 /*
 206                  * Now in whatever state the buffer currently is, we know that
 207                  * it has been written out and so we can drop it from the list
 208                  */
 209                 released = __journal_remove_checkpoint(jh);
 210                 jbd_unlock_bh_state(bh);
 211                 journal_remove_journal_head(bh);
 212                 __brelse(bh);
 213         }
 214
 215         return ret;
 216 }
 217
 218 #define NR_BATCH        64
 219
 220 static void
 221 __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
 222 {
 223         int i;
 224
 225         ll_rw_block(SWRITE, *batch_count, bhs);
 226         for (i = 0; i < *batch_count; i++) {
 227                 struct buffer_head *bh = bhs[i];
 228                 clear_buffer_jwrite(bh);
 229                 BUFFER_TRACE(bh, "brelse");
 230                 __brelse(bh);
 231         }
 232         *batch_count = 0;
 233 }
 234
 235 /*
 236  * Try to flush one buffer from the checkpoint list to disk.
 237  *
 238  * Return 1 if something happened which requires us to abort the current
 239  * scan of the checkpoint list.  Return <0 if the buffer has failed to
 240  * be written out.
 241  *
 242  * Called with j_list_lock held and drops it if 1 is returned
 243  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
 244  */
 245 static int __process_buffer(journal_t *journal, struct journal_head *jh,
 246                         struct buffer_head **bhs, int *batch_count)
 247 {
 248         struct buffer_head *bh = jh2bh(jh);
 249         int ret = 0;
 250
 251         if (buffer_locked(bh)) {
 252                 atomic_inc(&bh->b_count);
 253                 spin_unlock(&journal->j_list_lock);
 254                 jbd_unlock_bh_state(bh);
 255                 wait_on_buffer(bh);
 256                 /* the journal_head may have gone by now */
 257                 BUFFER_TRACE(bh, "brelse");
 258                 __brelse(bh);
 259                 ret = 1;
 260         } else if (jh->b_transaction != NULL) {
 261                 transaction_t *t = jh->b_transaction;
 262                 tid_t tid = t->t_tid;
 263
 264                 spin_unlock(&journal->j_list_lock);
 265                 jbd_unlock_bh_state(bh);
 266                 log_start_commit(journal, tid);
 267                 log_wait_commit(journal, tid);
 268                 ret = 1;
 269         } else if (!buffer_dirty(bh)) {
 270                 ret = 1;
 271                 if (unlikely(!buffer_uptodate(bh)))
 272                         ret = -EIO;
 273                 J_ASSERT_JH(jh, !buffer_jbddirty(bh));
 274                 BUFFER_TRACE(bh, "remove from checkpoint");
 275                 __journal_remove_checkpoint(jh);
 276                 spin_unlock(&journal->j_list_lock);
 277                 jbd_unlock_bh_state(bh);
 278                 journal_remove_journal_head(bh);
 279                 __brelse(bh);
 280         } else {
 281                 /*
 282                  * Important: we are about to write the buffer, and
 283                  * possibly block, while still holding the journal lock.
 284                  * We cannot afford to let the transaction logic start
 285                  * messing around with this buffer before we write it to
 286                  * disk, as that would break recoverability.
 287                  */
 288                 BUFFER_TRACE(bh, "queue");
 289                 get_bh(bh);
 290                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 291                 set_buffer_jwrite(bh);
 292                 bhs[*batch_count] = bh;
 293                 __buffer_relink_io(jh);
 294                 jbd_unlock_bh_state(bh);
 295                 (*batch_count)++;
 296                 if (*batch_count == NR_BATCH) {
 297                         spin_unlock(&journal->j_list_lock);
 298                         __flush_batch(journal, bhs, batch_count);
 299                         ret = 1;
 300                 }
 301         }
 302         return ret;
 303 }
 304
 305 /*
 306  * Perform an actual checkpoint. We take the first transaction on the
 307  * list of transactions to be checkpointed and send all its buffers
 308  * to disk. We submit larger chunks of data at once.
 309  *
 310  * The journal should be locked before calling this function.
 311  * Called with j_checkpoint_mutex held.
 312  */
 313 int log_do_checkpoint(journal_t *journal)
 314 {
 315         transaction_t *transaction;
 316         tid_t this_tid;
 317         int result;
 318
 319         jbd_debug(1, "Start checkpoint\n");
 320
 321         /*
 322          * First thing: if there are any transactions in the log which
 323          * don't need checkpointing, just eliminate them from the
 324          * journal straight away.
 325          */
 326         result = cleanup_journal_tail(journal);
 327         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 328         if (result <= 0)
 329                 return result;
 330
 331         /*
 332          * OK, we need to start writing disk blocks.  Take one transaction
 333          * and write it.
 334          */
 335         result = 0;
 336         spin_lock(&journal->j_list_lock);
 337         if (!journal->j_checkpoint_transactions)
 338                 goto out;
 339         transaction = journal->j_checkpoint_transactions;
 340         this_tid = transaction->t_tid;
 341 restart:
 342         /*
 343          * If someone cleaned up this transaction while we slept, we're
 344          * done (maybe it's a new transaction, but it fell at the same
 345          * address).
 346          */
 347         if (journal->j_checkpoint_transactions == transaction &&
 348                         transaction->t_tid == this_tid) {
 349                 int batch_count = 0;
 350                 struct buffer_head *bhs[NR_BATCH];
 351                 struct journal_head *jh;
 352                 int retry = 0, err;
 353
 354                 while (!retry && transaction->t_checkpoint_list) {
 355                         struct buffer_head *bh;
 356
 357                         jh = transaction->t_checkpoint_list;
 358                         bh = jh2bh(jh);
 359                         if (!jbd_trylock_bh_state(bh)) {
 360                                 jbd_sync_bh(journal, bh);
 361                                 retry = 1;
 362                                 break;
 363                         }
 364                         retry = __process_buffer(journal, jh, bhs,&batch_count);
 365                         if (retry < 0 && !result)
 366                                 result = retry;
 367                         if (!retry && (need_resched() ||
 368                                 spin_needbreak(&journal->j_list_lock))) {
 369                                 spin_unlock(&journal->j_list_lock);
 370                                 retry = 1;
 371                                 break;
 372                         }
 373                 }
 374
 375                 if (batch_count) {
 376                         if (!retry) {
 377                                 spin_unlock(&journal->j_list_lock);
 378                                 retry = 1;
 379                         }
 380                         __flush_batch(journal, bhs, &batch_count);
 381                 }
 382
 383                 if (retry) {
 384                         spin_lock(&journal->j_list_lock);
 385                         goto restart;
 386                 }
 387                 /*
 388                  * Now we have cleaned up the first transaction's checkpoint
 389                  * list. Let's clean up the second one
 390                  */
 391                 err = __wait_cp_io(journal, transaction);
 392                 if (!result)
 393                         result = err;
 394         }
 395 out:
 396         spin_unlock(&journal->j_list_lock);
 397         if (result < 0)
 398                 journal_abort(journal, result);
 399         else
 400                 result = cleanup_journal_tail(journal);
 401
 402         return (result < 0) ? result : 0;
 403 }
 404
 405 /*
 406  * Check the list of checkpoint transactions for the journal to see if
 407  * we have already got rid of any since the last update of the log tail
 408  * in the journal superblock.  If so, we can instantly roll the
 409  * superblock forward to remove those transactions from the log.
 410  *
 411  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 412  *
 413  * Called with the journal lock held.
 414  *
 415  * This is the only part of the journaling code which really needs to be
 416  * aware of transaction aborts.  Checkpointing involves writing to the
 417  * main filesystem area rather than to the journal, so it can proceed
 418  * even in abort state, but we must not update the super block if
 419  * checkpointing may have failed.  Otherwise, we would lose some metadata
 420  * buffers which should be written-back to the filesystem.
 421  */
 422
 423 int cleanup_journal_tail(journal_t *journal)
 424 {
 425         transaction_t * transaction;
 426         tid_t           first_tid;
 427         unsigned long   blocknr, freed;
 428
 429         if (is_journal_aborted(journal))
 430                 return 1;
 431
 432         /* OK, work out the oldest transaction remaining in the log, and
 433          * the log block it starts at.
 434          *
 435          * If the log is now empty, we need to work out which is the
 436          * next transaction ID we will write, and where it will
 437          * start. */
 438
 439         spin_lock(&journal->j_state_lock);
 440         spin_lock(&journal->j_list_lock);
 441         transaction = journal->j_checkpoint_transactions;
 442         if (transaction) {
 443                 first_tid = transaction->t_tid;
 444                 blocknr = transaction->t_log_start;
 445         } else if ((transaction = journal->j_committing_transaction) != NULL) {
 446                 first_tid = transaction->t_tid;
 447                 blocknr = transaction->t_log_start;
 448         } else if ((transaction = journal->j_running_transaction) != NULL) {
 449                 first_tid = transaction->t_tid;
 450                 blocknr = journal->j_head;
 451         } else {
 452                 first_tid = journal->j_transaction_sequence;
 453                 blocknr = journal->j_head;
 454         }
 455         spin_unlock(&journal->j_list_lock);
 456         J_ASSERT(blocknr != 0);
 457
 458         /* If the oldest pinned transaction is at the tail of the log
 459            already then there's not much we can do right now. */
 460         if (journal->j_tail_sequence == first_tid) {
 461                 spin_unlock(&journal->j_state_lock);
 462                 return 1;
 463         }
 464
 465         /* OK, update the superblock to recover the freed space.
 466          * Physical blocks come first: have we wrapped beyond the end of
 467          * the log?  */
 468         freed = blocknr - journal->j_tail;
 469         if (blocknr < journal->j_tail)
 470                 freed = freed + journal->j_last - journal->j_first;
 471
 472         jbd_debug(1,
 473                   "Cleaning journal tail from %d to %d (offset %lu), "
 474                   "freeing %lu\n",
 475                   journal->j_tail_sequence, first_tid, blocknr, freed);
 476
 477         journal->j_free += freed;
 478         journal->j_tail_sequence = first_tid;
 479         journal->j_tail = blocknr;
 480         spin_unlock(&journal->j_state_lock);
 481         if (!(journal->j_flags & JFS_ABORT))
 482                 journal_update_superblock(journal, 1);
 483         return 0;
 484 }
 485
 486
 487 /* Checkpoint list management */
 488
 489 /*
 490  * journal_clean_one_cp_list
 491  *
 492  * Find all the written-back checkpoint buffers in the given list and release them.
 493  *
 494  * Called with the journal locked.
 495  * Called with j_list_lock held.
 496  * Returns number of bufers reaped (for debug)
 497  */
 498
 499 static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
 500 {
 501         struct journal_head *last_jh;
 502         struct journal_head *next_jh = jh;
 503         int ret, freed = 0;
 504
 505         *released = 0;
 506         if (!jh)
 507                 return 0;
 508
 509         last_jh = jh->b_cpprev;
 510         do {
 511                 jh = next_jh;
 512                 next_jh = jh->b_cpnext;
 513                 /* Use trylock because of the ranking */
 514                 if (jbd_trylock_bh_state(jh2bh(jh))) {
 515                         ret = __try_to_free_cp_buf(jh);
 516                         if (ret) {
 517                                 freed++;
 518                                 if (ret == 2) {
 519                                         *released = 1;
 520                                         return freed;
 521                                 }
 522                         }
 523                 }
 524                 /*
 525                  * This function only frees up some memory
 526                  * if possible so we dont have an obligation
 527                  * to finish processing. Bail out if preemption
 528                  * requested:
 529                  */
 530                 if (need_resched())
 531                         return freed;
 532         } while (jh != last_jh);
 533
 534         return freed;
 535 }
 536
 537 /*
 538  * journal_clean_checkpoint_list
 539  *
 540  * Find all the written-back checkpoint buffers in the journal and release them.
 541  *
 542  * Called with the journal locked.
 543  * Called with j_list_lock held.
 544  * Returns number of buffers reaped (for debug)
 545  */
 546
 547 int __journal_clean_checkpoint_list(journal_t *journal)
 548 {
 549         transaction_t *transaction, *last_transaction, *next_transaction;
 550         int ret = 0;
 551         int released;
 552
 553         transaction = journal->j_checkpoint_transactions;
 554         if (!transaction)
 555                 goto out;
 556
 557         last_transaction = transaction->t_cpprev;
 558         next_transaction = transaction;
 559         do {
 560                 transaction = next_transaction;
 561                 next_transaction = transaction->t_cpnext;
 562                 ret += journal_clean_one_cp_list(transaction->
 563                                 t_checkpoint_list, &released);
 564                 /*
 565                  * This function only frees up some memory if possible so we
 566                  * dont have an obligation to finish processing. Bail out if
 567                  * preemption requested:
 568                  */
 569                 if (need_resched())
 570                         goto out;
 571                 if (released)
 572                         continue;
 573                 /*
 574                  * It is essential that we are as careful as in the case of
 575                  * t_checkpoint_list with removing the buffer from the list as
 576                  * we can possibly see not yet submitted buffers on io_list
 577                  */
 578                 ret += journal_clean_one_cp_list(transaction->
 579                                 t_checkpoint_io_list, &released);
 580                 if (need_resched())
 581                         goto out;
 582         } while (transaction != last_transaction);
 583 out:
 584         return ret;
 585 }
 586
 587 /*
 588  * journal_remove_checkpoint: called after a buffer has been committed
 589  * to disk (either by being write-back flushed to disk, or being
 590  * committed to the log).
 591  *
 592  * We cannot safely clean a transaction out of the log until all of the
 593  * buffer updates committed in that transaction have safely been stored
 594  * elsewhere on disk.  To achieve this, all of the buffers in a
 595  * transaction need to be maintained on the transaction's checkpoint
 596  * lists until they have been rewritten, at which point this function is
 597  * called to remove the buffer from the existing transaction's
 598  * checkpoint lists.
 599  *
 600  * The function returns 1 if it frees the transaction, 0 otherwise.
 601  *
 602  * This function is called with the journal locked.
 603  * This function is called with j_list_lock held.
 604  * This function is called with jbd_lock_bh_state(jh2bh(jh))
 605  */
 606
 607 int __journal_remove_checkpoint(struct journal_head *jh)
 608 {
 609         transaction_t *transaction;
 610         journal_t *journal;
 611         int ret = 0;
 612
 613         JBUFFER_TRACE(jh, "entry");
 614
 615         if ((transaction = jh->b_cp_transaction) == NULL) {
 616                 JBUFFER_TRACE(jh, "not on transaction");
 617                 goto out;
 618         }
 619         journal = transaction->t_journal;
 620
 621         __buffer_unlink(jh);
 622         jh->b_cp_transaction = NULL;
 623
 624         if (transaction->t_checkpoint_list != NULL ||
 625             transaction->t_checkpoint_io_list != NULL)
 626                 goto out;
 627         JBUFFER_TRACE(jh, "transaction has no more buffers");
 628
 629         /*
 630          * There is one special case to worry about: if we have just pulled the
 631          * buffer off a running or committing transaction's checkpoing list,
 632          * then even if the checkpoint list is empty, the transaction obviously
 633          * cannot be dropped!
 634          *
 635          * The locking here around t_state is a bit sleazy.
 636          * See the comment at the end of journal_commit_transaction().
 637          */
 638         if (transaction->t_state != T_FINISHED) {
 639                 JBUFFER_TRACE(jh, "belongs to running/committing transaction");
 640                 goto out;
 641         }
 642
 643         /* OK, that was the last buffer for the transaction: we can now
 644            safely remove this transaction from the log */
 645
 646         __journal_drop_transaction(journal, transaction);
 647
 648         /* Just in case anybody was waiting for more transactions to be
 649            checkpointed... */
 650         wake_up(&journal->j_wait_logspace);
 651         ret = 1;
 652 out:
 653         JBUFFER_TRACE(jh, "exit");
 654         return ret;
 655 }
 656
 657 /*
 658  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 659  * list so that we know when it is safe to clean the transaction out of
 660  * the log.
 661  *
 662  * Called with the journal locked.
 663  * Called with j_list_lock held.
 664  */
 665 void __journal_insert_checkpoint(struct journal_head *jh,
 666                                transaction_t *transaction)
 667 {
 668         JBUFFER_TRACE(jh, "entry");
 669         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 670         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 671
 672         jh->b_cp_transaction = transaction;
 673
 674         if (!transaction->t_checkpoint_list) {
 675                 jh->b_cpnext = jh->b_cpprev = jh;
 676         } else {
 677                 jh->b_cpnext = transaction->t_checkpoint_list;
 678                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 679                 jh->b_cpprev->b_cpnext = jh;
 680                 jh->b_cpnext->b_cpprev = jh;
 681         }
 682         transaction->t_checkpoint_list = jh;
 683 }
 684
 685 /*
 686  * We've finished with this transaction structure: adios...
 687  *
 688  * The transaction must have no links except for the checkpoint by this
 689  * point.
 690  *
 691  * Called with the journal locked.
 692  * Called with j_list_lock held.
 693  */
 694
 695 void __journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 696 {
 697         assert_spin_locked(&journal->j_list_lock);
 698         if (transaction->t_cpnext) {
 699                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 700                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 701                 if (journal->j_checkpoint_transactions == transaction)
 702                         journal->j_checkpoint_transactions =
 703                                 transaction->t_cpnext;
 704                 if (journal->j_checkpoint_transactions == transaction)
 705                         journal->j_checkpoint_transactions = NULL;
 706         }
 707
 708         J_ASSERT(transaction->t_state == T_FINISHED);
 709         J_ASSERT(transaction->t_buffers == NULL);
 710         J_ASSERT(transaction->t_sync_datalist == NULL);
 711         J_ASSERT(transaction->t_forget == NULL);
 712         J_ASSERT(transaction->t_iobuf_list == NULL);
 713         J_ASSERT(transaction->t_shadow_list == NULL);
 714         J_ASSERT(transaction->t_log_list == NULL);
 715         J_ASSERT(transaction->t_checkpoint_list == NULL);
 716         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 717         J_ASSERT(transaction->t_updates == 0);
 718         J_ASSERT(journal->j_committing_transaction != transaction);
 719         J_ASSERT(journal->j_running_transaction != transaction);
 720
 721         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 722         kfree(transaction);
 723 }