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 #include <linux/blkdev.h>
  26 #include <trace/events/jbd2.h>
  27
  28 /*
  29  * Unlink a buffer from a transaction checkpoint list.
  30  *
  31  * Called with j_list_lock held.
  32  */
  33 static inline void __buffer_unlink_first(struct journal_head *jh)
  34 {
  35         transaction_t *transaction = jh->b_cp_transaction;
  36
  37         jh->b_cpnext->b_cpprev = jh->b_cpprev;
  38         jh->b_cpprev->b_cpnext = jh->b_cpnext;
  39         if (transaction->t_checkpoint_list == jh) {
  40                 transaction->t_checkpoint_list = jh->b_cpnext;
  41                 if (transaction->t_checkpoint_list == jh)
  42                         transaction->t_checkpoint_list = NULL;
  43         }
  44 }
  45
  46 /*
  47  * Unlink a buffer from a transaction checkpoint(io) list.
  48  *
  49  * Called with j_list_lock held.
  50  */
  51 static inline void __buffer_unlink(struct journal_head *jh)
  52 {
  53         transaction_t *transaction = jh->b_cp_transaction;
  54
  55         __buffer_unlink_first(jh);
  56         if (transaction->t_checkpoint_io_list == jh) {
  57                 transaction->t_checkpoint_io_list = jh->b_cpnext;
  58                 if (transaction->t_checkpoint_io_list == jh)
  59                         transaction->t_checkpoint_io_list = NULL;
  60         }
  61 }
  62
  63 /*
  64  * Move a buffer from the checkpoint list to the checkpoint io list
  65  *
  66  * Called with j_list_lock held
  67  */
  68 static inline void __buffer_relink_io(struct journal_head *jh)
  69 {
  70         transaction_t *transaction = jh->b_cp_transaction;
  71
  72         __buffer_unlink_first(jh);
  73
  74         if (!transaction->t_checkpoint_io_list) {
  75                 jh->b_cpnext = jh->b_cpprev = jh;
  76         } else {
  77                 jh->b_cpnext = transaction->t_checkpoint_io_list;
  78                 jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
  79                 jh->b_cpprev->b_cpnext = jh;
  80                 jh->b_cpnext->b_cpprev = jh;
  81         }
  82         transaction->t_checkpoint_io_list = jh;
  83 }
  84
  85 /*
  86  * Try to release a checkpointed buffer from its transaction.
  87  * Returns 1 if we released it and 2 if we also released the
  88  * whole transaction.
  89  *
  90  * Requires j_list_lock
  91  */
  92 static int __try_to_free_cp_buf(struct journal_head *jh)
  93 {
  94         int ret = 0;
  95         struct buffer_head *bh = jh2bh(jh);
  96
  97         if (jh->b_transaction == NULL && !buffer_locked(bh) &&
  98             !buffer_dirty(bh) && !buffer_write_io_error(bh)) {
  99                 /*
 100                  * Get our reference so that bh cannot be freed before
 101                  * we unlock it
 102                  */
 103                 get_bh(bh);
 104                 JBUFFER_TRACE(jh, "remove from checkpoint list");
 105                 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
 106                 BUFFER_TRACE(bh, "release");
 107                 __brelse(bh);
 108         }
 109         return ret;
 110 }
 111
 112 /*
 113  * __jbd2_log_wait_for_space: wait until there is space in the journal.
 114  *
 115  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
 116  * for a checkpoint to free up some space in the log.
 117  */
 118 void __jbd2_log_wait_for_space(journal_t *journal)
 119 {
 120         int nblocks, space_left;
 121         /* assert_spin_locked(&journal->j_state_lock); */
 122
 123         nblocks = jbd_space_needed(journal);
 124         while (__jbd2_log_space_left(journal) < nblocks) {
 125                 if (journal->j_flags & JBD2_ABORT)
 126                         return;
 127                 write_unlock(&journal->j_state_lock);
 128                 mutex_lock(&journal->j_checkpoint_mutex);
 129
 130                 /*
 131                  * Test again, another process may have checkpointed while we
 132                  * were waiting for the checkpoint lock. If there are no
 133                  * transactions ready to be checkpointed, try to recover
 134                  * journal space by calling cleanup_journal_tail(), and if
 135                  * that doesn't work, by waiting for the currently committing
 136                  * transaction to complete.  If there is absolutely no way
 137                  * to make progress, this is either a BUG or corrupted
 138                  * filesystem, so abort the journal and leave a stack
 139                  * trace for forensic evidence.
 140                  */
 141                 write_lock(&journal->j_state_lock);
 142                 spin_lock(&journal->j_list_lock);
 143                 nblocks = jbd_space_needed(journal);
 144                 space_left = __jbd2_log_space_left(journal);
 145                 if (space_left < nblocks) {
 146                         int chkpt = journal->j_checkpoint_transactions != NULL;
 147                         tid_t tid = 0;
 148
 149                         if (journal->j_committing_transaction)
 150                                 tid = journal->j_committing_transaction->t_tid;
 151                         spin_unlock(&journal->j_list_lock);
 152                         write_unlock(&journal->j_state_lock);
 153                         if (chkpt) {
 154                                 jbd2_log_do_checkpoint(journal);
 155                         } else if (jbd2_cleanup_journal_tail(journal) == 0) {
 156                                 /* We were able to recover space; yay! */
 157                                 ;
 158                         } else if (tid) {
 159                                 jbd2_log_wait_commit(journal, tid);
 160                         } else {
 161                                 printk(KERN_ERR "%s: needed %d blocks and "
 162                                        "only had %d space available\n",
 163                                        __func__, nblocks, space_left);
 164                                 printk(KERN_ERR "%s: no way to get more "
 165                                        "journal space in %s\n", __func__,
 166                                        journal->j_devname);
 167                                 WARN_ON(1);
 168                                 jbd2_journal_abort(journal, 0);
 169                         }
 170                         write_lock(&journal->j_state_lock);
 171                 } else {
 172                         spin_unlock(&journal->j_list_lock);
 173                 }
 174                 mutex_unlock(&journal->j_checkpoint_mutex);
 175         }
 176 }
 177
 178 /*
 179  * Clean up transaction's list of buffers submitted for io.
 180  * We wait for any pending IO to complete and remove any clean
 181  * buffers. Note that we take the buffers in the opposite ordering
 182  * from the one in which they were submitted for IO.
 183  *
 184  * Return 0 on success, and return <0 if some buffers have failed
 185  * to be written out.
 186  *
 187  * Called with j_list_lock held.
 188  */
 189 static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
 190 {
 191         struct journal_head *jh;
 192         struct buffer_head *bh;
 193         tid_t this_tid;
 194         int released = 0;
 195         int ret = 0;
 196
 197         this_tid = transaction->t_tid;
 198 restart:
 199         /* Did somebody clean up the transaction in the meanwhile? */
 200         if (journal->j_checkpoint_transactions != transaction ||
 201                         transaction->t_tid != this_tid)
 202                 return ret;
 203         while (!released && transaction->t_checkpoint_io_list) {
 204                 jh = transaction->t_checkpoint_io_list;
 205                 bh = jh2bh(jh);
 206                 get_bh(bh);
 207                 if (buffer_locked(bh)) {
 208                         spin_unlock(&journal->j_list_lock);
 209                         wait_on_buffer(bh);
 210                         /* the journal_head may have gone by now */
 211                         BUFFER_TRACE(bh, "brelse");
 212                         __brelse(bh);
 213                         spin_lock(&journal->j_list_lock);
 214                         goto restart;
 215                 }
 216                 if (unlikely(buffer_write_io_error(bh)))
 217                         ret = -EIO;
 218
 219                 /*
 220                  * Now in whatever state the buffer currently is, we know that
 221                  * it has been written out and so we can drop it from the list
 222                  */
 223                 released = __jbd2_journal_remove_checkpoint(jh);
 224                 __brelse(bh);
 225         }
 226
 227         return ret;
 228 }
 229
 230 static void
 231 __flush_batch(journal_t *journal, int *batch_count)
 232 {
 233         int i;
 234         struct blk_plug plug;
 235
 236         blk_start_plug(&plug);
 237         for (i = 0; i < *batch_count; i++)
 238                 write_dirty_buffer(journal->j_chkpt_bhs[i], WRITE_SYNC);
 239         blk_finish_plug(&plug);
 240
 241         for (i = 0; i < *batch_count; i++) {
 242                 struct buffer_head *bh = journal->j_chkpt_bhs[i];
 243                 BUFFER_TRACE(bh, "brelse");
 244                 __brelse(bh);
 245         }
 246         *batch_count = 0;
 247 }
 248
 249 /*
 250  * Try to flush one buffer from the checkpoint list to disk.
 251  *
 252  * Return 1 if something happened which requires us to abort the current
 253  * scan of the checkpoint list.  Return <0 if the buffer has failed to
 254  * be written out.
 255  *
 256  * Called with j_list_lock held and drops it if 1 is returned
 257  */
 258 static int __process_buffer(journal_t *journal, struct journal_head *jh,
 259                             int *batch_count, transaction_t *transaction)
 260 {
 261         struct buffer_head *bh = jh2bh(jh);
 262         int ret = 0;
 263
 264         if (buffer_locked(bh)) {
 265                 get_bh(bh);
 266                 spin_unlock(&journal->j_list_lock);
 267                 wait_on_buffer(bh);
 268                 /* the journal_head may have gone by now */
 269                 BUFFER_TRACE(bh, "brelse");
 270                 __brelse(bh);
 271                 ret = 1;
 272         } else if (jh->b_transaction != NULL) {
 273                 transaction_t *t = jh->b_transaction;
 274                 tid_t tid = t->t_tid;
 275
 276                 transaction->t_chp_stats.cs_forced_to_close++;
 277                 spin_unlock(&journal->j_list_lock);
 278                 if (unlikely(journal->j_flags & JBD2_UNMOUNT))
 279                         /*
 280                          * The journal thread is dead; so starting and
 281                          * waiting for a commit to finish will cause
 282                          * us to wait for a _very_ long time.
 283                          */
 284                         printk(KERN_ERR "JBD2: %s: "
 285                                "Waiting for Godot: block %llu\n",
 286                                journal->j_devname,
 287                                (unsigned long long) bh->b_blocknr);
 288                 jbd2_log_start_commit(journal, tid);
 289                 jbd2_log_wait_commit(journal, tid);
 290                 ret = 1;
 291         } else if (!buffer_dirty(bh)) {
 292                 ret = 1;
 293                 if (unlikely(buffer_write_io_error(bh)))
 294                         ret = -EIO;
 295                 get_bh(bh);
 296                 BUFFER_TRACE(bh, "remove from checkpoint");
 297                 __jbd2_journal_remove_checkpoint(jh);
 298                 spin_unlock(&journal->j_list_lock);
 299                 __brelse(bh);
 300         } else {
 301                 /*
 302                  * Important: we are about to write the buffer, and
 303                  * possibly block, while still holding the journal lock.
 304                  * We cannot afford to let the transaction logic start
 305                  * messing around with this buffer before we write it to
 306                  * disk, as that would break recoverability.
 307                  */
 308                 BUFFER_TRACE(bh, "queue");
 309                 get_bh(bh);
 310                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 311                 journal->j_chkpt_bhs[*batch_count] = bh;
 312                 __buffer_relink_io(jh);
 313                 transaction->t_chp_stats.cs_written++;
 314                 (*batch_count)++;
 315                 if (*batch_count == JBD2_NR_BATCH) {
 316                         spin_unlock(&journal->j_list_lock);
 317                         __flush_batch(journal, batch_count);
 318                         ret = 1;
 319                 }
 320         }
 321         return ret;
 322 }
 323
 324 /*
 325  * Perform an actual checkpoint. We take the first transaction on the
 326  * list of transactions to be checkpointed and send all its buffers
 327  * to disk. We submit larger chunks of data at once.
 328  *
 329  * The journal should be locked before calling this function.
 330  * Called with j_checkpoint_mutex held.
 331  */
 332 int jbd2_log_do_checkpoint(journal_t *journal)
 333 {
 334         transaction_t *transaction;
 335         tid_t this_tid;
 336         int result;
 337
 338         jbd_debug(1, "Start checkpoint\n");
 339
 340         /*
 341          * First thing: if there are any transactions in the log which
 342          * don't need checkpointing, just eliminate them from the
 343          * journal straight away.
 344          */
 345         result = jbd2_cleanup_journal_tail(journal);
 346         trace_jbd2_checkpoint(journal, result);
 347         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 348         if (result <= 0)
 349                 return result;
 350
 351         /*
 352          * OK, we need to start writing disk blocks.  Take one transaction
 353          * and write it.
 354          */
 355         result = 0;
 356         spin_lock(&journal->j_list_lock);
 357         if (!journal->j_checkpoint_transactions)
 358                 goto out;
 359         transaction = journal->j_checkpoint_transactions;
 360         if (transaction->t_chp_stats.cs_chp_time == 0)
 361                 transaction->t_chp_stats.cs_chp_time = jiffies;
 362         this_tid = transaction->t_tid;
 363 restart:
 364         /*
 365          * If someone cleaned up this transaction while we slept, we're
 366          * done (maybe it's a new transaction, but it fell at the same
 367          * address).
 368          */
 369         if (journal->j_checkpoint_transactions == transaction &&
 370                         transaction->t_tid == this_tid) {
 371                 int batch_count = 0;
 372                 struct journal_head *jh;
 373                 int retry = 0, err;
 374
 375                 while (!retry && transaction->t_checkpoint_list) {
 376                         jh = transaction->t_checkpoint_list;
 377                         retry = __process_buffer(journal, jh, &batch_count,
 378                                                  transaction);
 379                         if (retry < 0 && !result)
 380                                 result = retry;
 381                         if (!retry && (need_resched() ||
 382                                 spin_needbreak(&journal->j_list_lock))) {
 383                                 spin_unlock(&journal->j_list_lock);
 384                                 retry = 1;
 385                                 break;
 386                         }
 387                 }
 388
 389                 if (batch_count) {
 390                         if (!retry) {
 391                                 spin_unlock(&journal->j_list_lock);
 392                                 retry = 1;
 393                         }
 394                         __flush_batch(journal, &batch_count);
 395                 }
 396
 397                 if (retry) {
 398                         spin_lock(&journal->j_list_lock);
 399                         goto restart;
 400                 }
 401                 /*
 402                  * Now we have cleaned up the first transaction's checkpoint
 403                  * list. Let's clean up the second one
 404                  */
 405                 err = __wait_cp_io(journal, transaction);
 406                 if (!result)
 407                         result = err;
 408         }
 409 out:
 410         spin_unlock(&journal->j_list_lock);
 411         if (result < 0)
 412                 jbd2_journal_abort(journal, result);
 413         else
 414                 result = jbd2_cleanup_journal_tail(journal);
 415
 416         return (result < 0) ? result : 0;
 417 }
 418
 419 /*
 420  * Check the list of checkpoint transactions for the journal to see if
 421  * we have already got rid of any since the last update of the log tail
 422  * in the journal superblock.  If so, we can instantly roll the
 423  * superblock forward to remove those transactions from the log.
 424  *
 425  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 426  *
 427  * Called with the journal lock held.
 428  *
 429  * This is the only part of the journaling code which really needs to be
 430  * aware of transaction aborts.  Checkpointing involves writing to the
 431  * main filesystem area rather than to the journal, so it can proceed
 432  * even in abort state, but we must not update the super block if
 433  * checkpointing may have failed.  Otherwise, we would lose some metadata
 434  * buffers which should be written-back to the filesystem.
 435  */
 436
 437 int jbd2_cleanup_journal_tail(journal_t *journal)
 438 {
 439         tid_t           first_tid;
 440         unsigned long   blocknr;
 441
 442         if (is_journal_aborted(journal))
 443                 return 1;
 444
 445         if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
 446                 return 1;
 447         J_ASSERT(blocknr != 0);
 448
 449         /*
 450          * We need to make sure that any blocks that were recently written out
 451          * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
 452          * we drop the transactions from the journal. It's unlikely this will
 453          * be necessary, especially with an appropriately sized journal, but we
 454          * need this to guarantee correctness.  Fortunately
 455          * jbd2_cleanup_journal_tail() doesn't get called all that often.
 456          */
 457         if (journal->j_flags & JBD2_BARRIER)
 458                 blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
 459
 460         __jbd2_update_log_tail(journal, first_tid, blocknr);
 461         return 0;
 462 }
 463
 464
 465 /* Checkpoint list management */
 466
 467 /*
 468  * journal_clean_one_cp_list
 469  *
 470  * Find all the written-back checkpoint buffers in the given list and
 471  * release them.
 472  *
 473  * Called with the journal locked.
 474  * Called with j_list_lock held.
 475  * Returns number of buffers reaped (for debug)
 476  */
 477
 478 static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
 479 {
 480         struct journal_head *last_jh;
 481         struct journal_head *next_jh = jh;
 482         int ret, freed = 0;
 483
 484         *released = 0;
 485         if (!jh)
 486                 return 0;
 487
 488         last_jh = jh->b_cpprev;
 489         do {
 490                 jh = next_jh;
 491                 next_jh = jh->b_cpnext;
 492                 ret = __try_to_free_cp_buf(jh);
 493                 if (ret) {
 494                         freed++;
 495                         if (ret == 2) {
 496                                 *released = 1;
 497                                 return freed;
 498                         }
 499                 }
 500                 /*
 501                  * This function only frees up some memory
 502                  * if possible so we dont have an obligation
 503                  * to finish processing. Bail out if preemption
 504                  * requested:
 505                  */
 506                 if (need_resched())
 507                         return freed;
 508         } while (jh != last_jh);
 509
 510         return freed;
 511 }
 512
 513 /*
 514  * journal_clean_checkpoint_list
 515  *
 516  * Find all the written-back checkpoint buffers in the journal and release them.
 517  *
 518  * Called with the journal locked.
 519  * Called with j_list_lock held.
 520  * Returns number of buffers reaped (for debug)
 521  */
 522
 523 int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
 524 {
 525         transaction_t *transaction, *last_transaction, *next_transaction;
 526         int ret = 0;
 527         int released;
 528
 529         transaction = journal->j_checkpoint_transactions;
 530         if (!transaction)
 531                 goto out;
 532
 533         last_transaction = transaction->t_cpprev;
 534         next_transaction = transaction;
 535         do {
 536                 transaction = next_transaction;
 537                 next_transaction = transaction->t_cpnext;
 538                 ret += journal_clean_one_cp_list(transaction->
 539                                 t_checkpoint_list, &released);
 540                 /*
 541                  * This function only frees up some memory if possible so we
 542                  * dont have an obligation to finish processing. Bail out if
 543                  * preemption requested:
 544                  */
 545                 if (need_resched())
 546                         goto out;
 547                 if (released)
 548                         continue;
 549                 /*
 550                  * It is essential that we are as careful as in the case of
 551                  * t_checkpoint_list with removing the buffer from the list as
 552                  * we can possibly see not yet submitted buffers on io_list
 553                  */
 554                 ret += journal_clean_one_cp_list(transaction->
 555                                 t_checkpoint_io_list, &released);
 556                 if (need_resched())
 557                         goto out;
 558         } while (transaction != last_transaction);
 559 out:
 560         return ret;
 561 }
 562
 563 /*
 564  * journal_remove_checkpoint: called after a buffer has been committed
 565  * to disk (either by being write-back flushed to disk, or being
 566  * committed to the log).
 567  *
 568  * We cannot safely clean a transaction out of the log until all of the
 569  * buffer updates committed in that transaction have safely been stored
 570  * elsewhere on disk.  To achieve this, all of the buffers in a
 571  * transaction need to be maintained on the transaction's checkpoint
 572  * lists until they have been rewritten, at which point this function is
 573  * called to remove the buffer from the existing transaction's
 574  * checkpoint lists.
 575  *
 576  * The function returns 1 if it frees the transaction, 0 otherwise.
 577  * The function can free jh and bh.
 578  *
 579  * This function is called with j_list_lock held.
 580  */
 581 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 582 {
 583         struct transaction_chp_stats_s *stats;
 584         transaction_t *transaction;
 585         journal_t *journal;
 586         int ret = 0;
 587
 588         JBUFFER_TRACE(jh, "entry");
 589
 590         if ((transaction = jh->b_cp_transaction) == NULL) {
 591                 JBUFFER_TRACE(jh, "not on transaction");
 592                 goto out;
 593         }
 594         journal = transaction->t_journal;
 595
 596         JBUFFER_TRACE(jh, "removing from transaction");
 597         __buffer_unlink(jh);
 598         jh->b_cp_transaction = NULL;
 599         jbd2_journal_put_journal_head(jh);
 600
 601         if (transaction->t_checkpoint_list != NULL ||
 602             transaction->t_checkpoint_io_list != NULL)
 603                 goto out;
 604
 605         /*
 606          * There is one special case to worry about: if we have just pulled the
 607          * buffer off a running or committing transaction's checkpoing list,
 608          * then even if the checkpoint list is empty, the transaction obviously
 609          * cannot be dropped!
 610          *
 611          * The locking here around t_state is a bit sleazy.
 612          * See the comment at the end of jbd2_journal_commit_transaction().
 613          */
 614         if (transaction->t_state != T_FINISHED)
 615                 goto out;
 616
 617         /* OK, that was the last buffer for the transaction: we can now
 618            safely remove this transaction from the log */
 619         stats = &transaction->t_chp_stats;
 620         if (stats->cs_chp_time)
 621                 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
 622                                                     jiffies);
 623         trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
 624                                     transaction->t_tid, stats);
 625
 626         __jbd2_journal_drop_transaction(journal, transaction);
 627         jbd2_journal_free_transaction(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         return ret;
 635 }
 636
 637 /*
 638  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 639  * list so that we know when it is safe to clean the transaction out of
 640  * the log.
 641  *
 642  * Called with the journal locked.
 643  * Called with j_list_lock held.
 644  */
 645 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
 646                                transaction_t *transaction)
 647 {
 648         JBUFFER_TRACE(jh, "entry");
 649         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 650         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 651
 652         /* Get reference for checkpointing transaction */
 653         jbd2_journal_grab_journal_head(jh2bh(jh));
 654         jh->b_cp_transaction = transaction;
 655
 656         if (!transaction->t_checkpoint_list) {
 657                 jh->b_cpnext = jh->b_cpprev = jh;
 658         } else {
 659                 jh->b_cpnext = transaction->t_checkpoint_list;
 660                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 661                 jh->b_cpprev->b_cpnext = jh;
 662                 jh->b_cpnext->b_cpprev = jh;
 663         }
 664         transaction->t_checkpoint_list = jh;
 665 }
 666
 667 /*
 668  * We've finished with this transaction structure: adios...
 669  *
 670  * The transaction must have no links except for the checkpoint by this
 671  * point.
 672  *
 673  * Called with the journal locked.
 674  * Called with j_list_lock held.
 675  */
 676
 677 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 678 {
 679         assert_spin_locked(&journal->j_list_lock);
 680         if (transaction->t_cpnext) {
 681                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 682                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 683                 if (journal->j_checkpoint_transactions == transaction)
 684                         journal->j_checkpoint_transactions =
 685                                 transaction->t_cpnext;
 686                 if (journal->j_checkpoint_transactions == transaction)
 687                         journal->j_checkpoint_transactions = NULL;
 688         }
 689
 690         J_ASSERT(transaction->t_state == T_FINISHED);
 691         J_ASSERT(transaction->t_buffers == NULL);
 692         J_ASSERT(transaction->t_forget == NULL);
 693         J_ASSERT(transaction->t_iobuf_list == NULL);
 694         J_ASSERT(transaction->t_shadow_list == NULL);
 695         J_ASSERT(transaction->t_log_list == NULL);
 696         J_ASSERT(transaction->t_checkpoint_list == NULL);
 697         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 698         J_ASSERT(atomic_read(&transaction->t_updates) == 0);
 699         J_ASSERT(journal->j_committing_transaction != transaction);
 700         J_ASSERT(journal->j_running_transaction != transaction);
 701
 702         trace_jbd2_drop_transaction(journal, transaction);
 703
 704         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 705 }