fs/jbd2/checkpoint.c

   1 /*
   2  * linux/fs/jbd2/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/jbd2.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 = __jbd2_journal_remove_checkpoint(jh) + 1;
  99                 jbd_unlock_bh_state(bh);
 100                 jbd2_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  * __jbd2_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 __jbd2_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 (__jbd2_log_space_left(journal) < nblocks) {
 122                 if (journal->j_flags & JBD2_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 (__jbd2_log_space_left(journal) < nblocks) {
 134                         spin_unlock(&journal->j_state_lock);
 135                         jbd2_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         __releases(journal->j_list_lock)
 149 {
 150         get_bh(bh);
 151         spin_unlock(&journal->j_list_lock);
 152         jbd_lock_bh_state(bh);
 153         jbd_unlock_bh_state(bh);
 154         put_bh(bh);
 155 }
 156
 157 /*
 158  * Clean up transaction's list of buffers submitted for io.
 159  * We wait for any pending IO to complete and remove any clean
 160  * buffers. Note that we take the buffers in the opposite ordering
 161  * from the one in which they were submitted for IO.
 162  *
 163  * Called with j_list_lock held.
 164  */
 165 static void __wait_cp_io(journal_t *journal, transaction_t *transaction)
 166 {
 167         struct journal_head *jh;
 168         struct buffer_head *bh;
 169         tid_t this_tid;
 170         int released = 0;
 171
 172         this_tid = transaction->t_tid;
 173 restart:
 174         /* Did somebody clean up the transaction in the meanwhile? */
 175         if (journal->j_checkpoint_transactions != transaction ||
 176                         transaction->t_tid != this_tid)
 177                 return;
 178         while (!released && transaction->t_checkpoint_io_list) {
 179                 jh = transaction->t_checkpoint_io_list;
 180                 bh = jh2bh(jh);
 181                 if (!jbd_trylock_bh_state(bh)) {
 182                         jbd_sync_bh(journal, bh);
 183                         spin_lock(&journal->j_list_lock);
 184                         goto restart;
 185                 }
 186                 if (buffer_locked(bh)) {
 187                         atomic_inc(&bh->b_count);
 188                         spin_unlock(&journal->j_list_lock);
 189                         jbd_unlock_bh_state(bh);
 190                         wait_on_buffer(bh);
 191                         /* the journal_head may have gone by now */
 192                         BUFFER_TRACE(bh, "brelse");
 193                         __brelse(bh);
 194                         spin_lock(&journal->j_list_lock);
 195                         goto restart;
 196                 }
 197                 /*
 198                  * Now in whatever state the buffer currently is, we know that
 199                  * it has been written out and so we can drop it from the list
 200                  */
 201                 released = __jbd2_journal_remove_checkpoint(jh);
 202                 jbd_unlock_bh_state(bh);
 203                 jbd2_journal_remove_journal_head(bh);
 204                 __brelse(bh);
 205         }
 206 }
 207
 208 #define NR_BATCH        64
 209
 210 static void
 211 __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
 212 {
 213         int i;
 214
 215         ll_rw_block(SWRITE, *batch_count, bhs);
 216         for (i = 0; i < *batch_count; i++) {
 217                 struct buffer_head *bh = bhs[i];
 218                 clear_buffer_jwrite(bh);
 219                 BUFFER_TRACE(bh, "brelse");
 220                 __brelse(bh);
 221         }
 222         *batch_count = 0;
 223 }
 224
 225 /*
 226  * Try to flush one buffer from the checkpoint list to disk.
 227  *
 228  * Return 1 if something happened which requires us to abort the current
 229  * scan of the checkpoint list.
 230  *
 231  * Called with j_list_lock held and drops it if 1 is returned
 232  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
 233  */
 234 static int __process_buffer(journal_t *journal, struct journal_head *jh,
 235                         struct buffer_head **bhs, int *batch_count,
 236                         transaction_t *transaction)
 237 {
 238         struct buffer_head *bh = jh2bh(jh);
 239         int ret = 0;
 240
 241         if (buffer_locked(bh)) {
 242                 atomic_inc(&bh->b_count);
 243                 spin_unlock(&journal->j_list_lock);
 244                 jbd_unlock_bh_state(bh);
 245                 wait_on_buffer(bh);
 246                 /* the journal_head may have gone by now */
 247                 BUFFER_TRACE(bh, "brelse");
 248                 __brelse(bh);
 249                 ret = 1;
 250         } else if (jh->b_transaction != NULL) {
 251                 transaction_t *t = jh->b_transaction;
 252                 tid_t tid = t->t_tid;
 253
 254                 transaction->t_chp_stats.cs_forced_to_close++;
 255                 spin_unlock(&journal->j_list_lock);
 256                 jbd_unlock_bh_state(bh);
 257                 jbd2_log_start_commit(journal, tid);
 258                 jbd2_log_wait_commit(journal, tid);
 259                 ret = 1;
 260         } else if (!buffer_dirty(bh)) {
 261                 J_ASSERT_JH(jh, !buffer_jbddirty(bh));
 262                 BUFFER_TRACE(bh, "remove from checkpoint");
 263                 __jbd2_journal_remove_checkpoint(jh);
 264                 spin_unlock(&journal->j_list_lock);
 265                 jbd_unlock_bh_state(bh);
 266                 jbd2_journal_remove_journal_head(bh);
 267                 __brelse(bh);
 268                 ret = 1;
 269         } else {
 270                 /*
 271                  * Important: we are about to write the buffer, and
 272                  * possibly block, while still holding the journal lock.
 273                  * We cannot afford to let the transaction logic start
 274                  * messing around with this buffer before we write it to
 275                  * disk, as that would break recoverability.
 276                  */
 277                 BUFFER_TRACE(bh, "queue");
 278                 get_bh(bh);
 279                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 280                 set_buffer_jwrite(bh);
 281                 bhs[*batch_count] = bh;
 282                 __buffer_relink_io(jh);
 283                 jbd_unlock_bh_state(bh);
 284                 transaction->t_chp_stats.cs_written++;
 285                 (*batch_count)++;
 286                 if (*batch_count == NR_BATCH) {
 287                         spin_unlock(&journal->j_list_lock);
 288                         __flush_batch(journal, bhs, batch_count);
 289                         ret = 1;
 290                 }
 291         }
 292         return ret;
 293 }
 294
 295 /*
 296  * Perform an actual checkpoint. We take the first transaction on the
 297  * list of transactions to be checkpointed and send all its buffers
 298  * to disk. We submit larger chunks of data at once.
 299  *
 300  * The journal should be locked before calling this function.
 301  */
 302 int jbd2_log_do_checkpoint(journal_t *journal)
 303 {
 304         transaction_t *transaction;
 305         tid_t this_tid;
 306         int result;
 307
 308         jbd_debug(1, "Start checkpoint\n");
 309
 310         /*
 311          * First thing: if there are any transactions in the log which
 312          * don't need checkpointing, just eliminate them from the
 313          * journal straight away.
 314          */
 315         result = jbd2_cleanup_journal_tail(journal);
 316         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 317         if (result <= 0)
 318                 return result;
 319
 320         /*
 321          * OK, we need to start writing disk blocks.  Take one transaction
 322          * and write it.
 323          */
 324         spin_lock(&journal->j_list_lock);
 325         if (!journal->j_checkpoint_transactions)
 326                 goto out;
 327         transaction = journal->j_checkpoint_transactions;
 328         if (transaction->t_chp_stats.cs_chp_time == 0)
 329                 transaction->t_chp_stats.cs_chp_time = jiffies;
 330         this_tid = transaction->t_tid;
 331 restart:
 332         /*
 333          * If someone cleaned up this transaction while we slept, we're
 334          * done (maybe it's a new transaction, but it fell at the same
 335          * address).
 336          */
 337         if (journal->j_checkpoint_transactions == transaction &&
 338                         transaction->t_tid == this_tid) {
 339                 int batch_count = 0;
 340                 struct buffer_head *bhs[NR_BATCH];
 341                 struct journal_head *jh;
 342                 int retry = 0;
 343
 344                 while (!retry && transaction->t_checkpoint_list) {
 345                         struct buffer_head *bh;
 346
 347                         jh = transaction->t_checkpoint_list;
 348                         bh = jh2bh(jh);
 349                         if (!jbd_trylock_bh_state(bh)) {
 350                                 jbd_sync_bh(journal, bh);
 351                                 retry = 1;
 352                                 break;
 353                         }
 354                         retry = __process_buffer(journal, jh, bhs, &batch_count,
 355                                                  transaction);
 356                         if (!retry && (need_resched() ||
 357                                 spin_needbreak(&journal->j_list_lock))) {
 358                                 spin_unlock(&journal->j_list_lock);
 359                                 retry = 1;
 360                                 break;
 361                         }
 362                 }
 363
 364                 if (batch_count) {
 365                         if (!retry) {
 366                                 spin_unlock(&journal->j_list_lock);
 367                                 retry = 1;
 368                         }
 369                         __flush_batch(journal, bhs, &batch_count);
 370                 }
 371
 372                 if (retry) {
 373                         spin_lock(&journal->j_list_lock);
 374                         goto restart;
 375                 }
 376                 /*
 377                  * Now we have cleaned up the first transaction's checkpoint
 378                  * list. Let's clean up the second one
 379                  */
 380                 __wait_cp_io(journal, transaction);
 381         }
 382 out:
 383         spin_unlock(&journal->j_list_lock);
 384         result = jbd2_cleanup_journal_tail(journal);
 385         if (result < 0)
 386                 return result;
 387         return 0;
 388 }
 389
 390 /*
 391  * Check the list of checkpoint transactions for the journal to see if
 392  * we have already got rid of any since the last update of the log tail
 393  * in the journal superblock.  If so, we can instantly roll the
 394  * superblock forward to remove those transactions from the log.
 395  *
 396  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 397  *
 398  * Called with the journal lock held.
 399  *
 400  * This is the only part of the journaling code which really needs to be
 401  * aware of transaction aborts.  Checkpointing involves writing to the
 402  * main filesystem area rather than to the journal, so it can proceed
 403  * even in abort state, but we must not update the journal superblock if
 404  * we have an abort error outstanding.
 405  */
 406
 407 int jbd2_cleanup_journal_tail(journal_t *journal)
 408 {
 409         transaction_t * transaction;
 410         tid_t           first_tid;
 411         unsigned long   blocknr, freed;
 412
 413         /* OK, work out the oldest transaction remaining in the log, and
 414          * the log block it starts at.
 415          *
 416          * If the log is now empty, we need to work out which is the
 417          * next transaction ID we will write, and where it will
 418          * start. */
 419
 420         spin_lock(&journal->j_state_lock);
 421         spin_lock(&journal->j_list_lock);
 422         transaction = journal->j_checkpoint_transactions;
 423         if (transaction) {
 424                 first_tid = transaction->t_tid;
 425                 blocknr = transaction->t_log_start;
 426         } else if ((transaction = journal->j_committing_transaction) != NULL) {
 427                 first_tid = transaction->t_tid;
 428                 blocknr = transaction->t_log_start;
 429         } else if ((transaction = journal->j_running_transaction) != NULL) {
 430                 first_tid = transaction->t_tid;
 431                 blocknr = journal->j_head;
 432         } else {
 433                 first_tid = journal->j_transaction_sequence;
 434                 blocknr = journal->j_head;
 435         }
 436         spin_unlock(&journal->j_list_lock);
 437         J_ASSERT(blocknr != 0);
 438
 439         /* If the oldest pinned transaction is at the tail of the log
 440            already then there's not much we can do right now. */
 441         if (journal->j_tail_sequence == first_tid) {
 442                 spin_unlock(&journal->j_state_lock);
 443                 return 1;
 444         }
 445
 446         /* OK, update the superblock to recover the freed space.
 447          * Physical blocks come first: have we wrapped beyond the end of
 448          * the log?  */
 449         freed = blocknr - journal->j_tail;
 450         if (blocknr < journal->j_tail)
 451                 freed = freed + journal->j_last - journal->j_first;
 452
 453         jbd_debug(1,
 454                   "Cleaning journal tail from %d to %d (offset %lu), "
 455                   "freeing %lu\n",
 456                   journal->j_tail_sequence, first_tid, blocknr, freed);
 457
 458         journal->j_free += freed;
 459         journal->j_tail_sequence = first_tid;
 460         journal->j_tail = blocknr;
 461         spin_unlock(&journal->j_state_lock);
 462         if (!(journal->j_flags & JBD2_ABORT))
 463                 jbd2_journal_update_superblock(journal, 1);
 464         return 0;
 465 }
 466
 467
 468 /* Checkpoint list management */
 469
 470 /*
 471  * journal_clean_one_cp_list
 472  *
 473  * Find all the written-back checkpoint buffers in the given list and release them.
 474  *
 475  * Called with the journal locked.
 476  * Called with j_list_lock held.
 477  * Returns number of bufers reaped (for debug)
 478  */
 479
 480 static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
 481 {
 482         struct journal_head *last_jh;
 483         struct journal_head *next_jh = jh;
 484         int ret, freed = 0;
 485
 486         *released = 0;
 487         if (!jh)
 488                 return 0;
 489
 490         last_jh = jh->b_cpprev;
 491         do {
 492                 jh = next_jh;
 493                 next_jh = jh->b_cpnext;
 494                 /* Use trylock because of the ranking */
 495                 if (jbd_trylock_bh_state(jh2bh(jh))) {
 496                         ret = __try_to_free_cp_buf(jh);
 497                         if (ret) {
 498                                 freed++;
 499                                 if (ret == 2) {
 500                                         *released = 1;
 501                                         return freed;
 502                                 }
 503                         }
 504                 }
 505                 /*
 506                  * This function only frees up some memory
 507                  * if possible so we dont have an obligation
 508                  * to finish processing. Bail out if preemption
 509                  * requested:
 510                  */
 511                 if (need_resched())
 512                         return freed;
 513         } while (jh != last_jh);
 514
 515         return freed;
 516 }
 517
 518 /*
 519  * journal_clean_checkpoint_list
 520  *
 521  * Find all the written-back checkpoint buffers in the journal and release them.
 522  *
 523  * Called with the journal locked.
 524  * Called with j_list_lock held.
 525  * Returns number of buffers reaped (for debug)
 526  */
 527
 528 int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
 529 {
 530         transaction_t *transaction, *last_transaction, *next_transaction;
 531         int ret = 0;
 532         int released;
 533
 534         transaction = journal->j_checkpoint_transactions;
 535         if (!transaction)
 536                 goto out;
 537
 538         last_transaction = transaction->t_cpprev;
 539         next_transaction = transaction;
 540         do {
 541                 transaction = next_transaction;
 542                 next_transaction = transaction->t_cpnext;
 543                 ret += journal_clean_one_cp_list(transaction->
 544                                 t_checkpoint_list, &released);
 545                 /*
 546                  * This function only frees up some memory if possible so we
 547                  * dont have an obligation to finish processing. Bail out if
 548                  * preemption requested:
 549                  */
 550                 if (need_resched())
 551                         goto out;
 552                 if (released)
 553                         continue;
 554                 /*
 555                  * It is essential that we are as careful as in the case of
 556                  * t_checkpoint_list with removing the buffer from the list as
 557                  * we can possibly see not yet submitted buffers on io_list
 558                  */
 559                 ret += journal_clean_one_cp_list(transaction->
 560                                 t_checkpoint_io_list, &released);
 561                 if (need_resched())
 562                         goto out;
 563         } while (transaction != last_transaction);
 564 out:
 565         return ret;
 566 }
 567
 568 /*
 569  * journal_remove_checkpoint: called after a buffer has been committed
 570  * to disk (either by being write-back flushed to disk, or being
 571  * committed to the log).
 572  *
 573  * We cannot safely clean a transaction out of the log until all of the
 574  * buffer updates committed in that transaction have safely been stored
 575  * elsewhere on disk.  To achieve this, all of the buffers in a
 576  * transaction need to be maintained on the transaction's checkpoint
 577  * lists until they have been rewritten, at which point this function is
 578  * called to remove the buffer from the existing transaction's
 579  * checkpoint lists.
 580  *
 581  * The function returns 1 if it frees the transaction, 0 otherwise.
 582  *
 583  * This function is called with the journal locked.
 584  * This function is called with j_list_lock held.
 585  * This function is called with jbd_lock_bh_state(jh2bh(jh))
 586  */
 587
 588 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 589 {
 590         transaction_t *transaction;
 591         journal_t *journal;
 592         int ret = 0;
 593
 594         JBUFFER_TRACE(jh, "entry");
 595
 596         if ((transaction = jh->b_cp_transaction) == NULL) {
 597                 JBUFFER_TRACE(jh, "not on transaction");
 598                 goto out;
 599         }
 600         journal = transaction->t_journal;
 601
 602         __buffer_unlink(jh);
 603         jh->b_cp_transaction = NULL;
 604
 605         if (transaction->t_checkpoint_list != NULL ||
 606             transaction->t_checkpoint_io_list != NULL)
 607                 goto out;
 608         JBUFFER_TRACE(jh, "transaction has no more buffers");
 609
 610         /*
 611          * There is one special case to worry about: if we have just pulled the
 612          * buffer off a running or committing transaction's checkpoing list,
 613          * then even if the checkpoint list is empty, the transaction obviously
 614          * cannot be dropped!
 615          *
 616          * The locking here around t_state is a bit sleazy.
 617          * See the comment at the end of jbd2_journal_commit_transaction().
 618          */
 619         if (transaction->t_state != T_FINISHED) {
 620                 JBUFFER_TRACE(jh, "belongs to running/committing transaction");
 621                 goto out;
 622         }
 623
 624         /* OK, that was the last buffer for the transaction: we can now
 625            safely remove this transaction from the log */
 626
 627         __jbd2_journal_drop_transaction(journal, transaction);
 628
 629         /* Just in case anybody was waiting for more transactions to be
 630            checkpointed... */
 631         wake_up(&journal->j_wait_logspace);
 632         ret = 1;
 633 out:
 634         JBUFFER_TRACE(jh, "exit");
 635         return ret;
 636 }
 637
 638 /*
 639  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 640  * list so that we know when it is safe to clean the transaction out of
 641  * the log.
 642  *
 643  * Called with the journal locked.
 644  * Called with j_list_lock held.
 645  */
 646 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
 647                                transaction_t *transaction)
 648 {
 649         JBUFFER_TRACE(jh, "entry");
 650         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 651         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 652
 653         jh->b_cp_transaction = transaction;
 654
 655         if (!transaction->t_checkpoint_list) {
 656                 jh->b_cpnext = jh->b_cpprev = jh;
 657         } else {
 658                 jh->b_cpnext = transaction->t_checkpoint_list;
 659                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 660                 jh->b_cpprev->b_cpnext = jh;
 661                 jh->b_cpnext->b_cpprev = jh;
 662         }
 663         transaction->t_checkpoint_list = jh;
 664 }
 665
 666 /*
 667  * We've finished with this transaction structure: adios...
 668  *
 669  * The transaction must have no links except for the checkpoint by this
 670  * point.
 671  *
 672  * Called with the journal locked.
 673  * Called with j_list_lock held.
 674  */
 675
 676 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 677 {
 678         assert_spin_locked(&journal->j_list_lock);
 679         if (transaction->t_cpnext) {
 680                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 681                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 682                 if (journal->j_checkpoint_transactions == transaction)
 683                         journal->j_checkpoint_transactions =
 684                                 transaction->t_cpnext;
 685                 if (journal->j_checkpoint_transactions == transaction)
 686                         journal->j_checkpoint_transactions = NULL;
 687         }
 688
 689         J_ASSERT(transaction->t_state == T_FINISHED);
 690         J_ASSERT(transaction->t_buffers == NULL);
 691         J_ASSERT(transaction->t_forget == NULL);
 692         J_ASSERT(transaction->t_iobuf_list == NULL);
 693         J_ASSERT(transaction->t_shadow_list == NULL);
 694         J_ASSERT(transaction->t_log_list == NULL);
 695         J_ASSERT(transaction->t_checkpoint_list == NULL);
 696         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 697         J_ASSERT(transaction->t_updates == 0);
 698         J_ASSERT(journal->j_committing_transaction != transaction);
 699         J_ASSERT(journal->j_running_transaction != transaction);
 700
 701         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 702         kfree(transaction);
 703 }