fs/jbd/checkpoint.c

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