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 = jbd2_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 = jbd2_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                                 /*
 160                                  * jbd2_journal_commit_transaction() may want
 161                                  * to take the checkpoint_mutex if JBD2_FLUSHED
 162                                  * is set.  So we need to temporarily drop it.
 163                                  */
 164                                 mutex_unlock(&journal->j_checkpoint_mutex);
 165                                 jbd2_log_wait_commit(journal, tid);
 166                                 write_lock(&journal->j_state_lock);
 167                                 continue;
 168                         } else {
 169                                 printk(KERN_ERR "%s: needed %d blocks and "
 170                                        "only had %d space available\n",
 171                                        __func__, nblocks, space_left);
 172                                 printk(KERN_ERR "%s: no way to get more "
 173                                        "journal space in %s\n", __func__,
 174                                        journal->j_devname);
 175                                 WARN_ON(1);
 176                                 jbd2_journal_abort(journal, 0);
 177                         }
 178                         write_lock(&journal->j_state_lock);
 179                 } else {
 180                         spin_unlock(&journal->j_list_lock);
 181                 }
 182                 mutex_unlock(&journal->j_checkpoint_mutex);
 183         }
 184 }
 185
 186 /*
 187  * Clean up transaction's list of buffers submitted for io.
 188  * We wait for any pending IO to complete and remove any clean
 189  * buffers. Note that we take the buffers in the opposite ordering
 190  * from the one in which they were submitted for IO.
 191  *
 192  * Return 0 on success, and return <0 if some buffers have failed
 193  * to be written out.
 194  *
 195  * Called with j_list_lock held.
 196  */
 197 static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
 198 {
 199         struct journal_head *jh;
 200         struct buffer_head *bh;
 201         tid_t this_tid;
 202         int released = 0;
 203         int ret = 0;
 204
 205         this_tid = transaction->t_tid;
 206 restart:
 207         /* Did somebody clean up the transaction in the meanwhile? */
 208         if (journal->j_checkpoint_transactions != transaction ||
 209                         transaction->t_tid != this_tid)
 210                 return ret;
 211         while (!released && transaction->t_checkpoint_io_list) {
 212                 jh = transaction->t_checkpoint_io_list;
 213                 bh = jh2bh(jh);
 214                 get_bh(bh);
 215                 if (buffer_locked(bh)) {
 216                         spin_unlock(&journal->j_list_lock);
 217                         wait_on_buffer(bh);
 218                         /* the journal_head may have gone by now */
 219                         BUFFER_TRACE(bh, "brelse");
 220                         __brelse(bh);
 221                         spin_lock(&journal->j_list_lock);
 222                         goto restart;
 223                 }
 224                 if (unlikely(buffer_write_io_error(bh)))
 225                         ret = -EIO;
 226
 227                 /*
 228                  * Now in whatever state the buffer currently is, we know that
 229                  * it has been written out and so we can drop it from the list
 230                  */
 231                 released = __jbd2_journal_remove_checkpoint(jh);
 232                 __brelse(bh);
 233         }
 234
 235         return ret;
 236 }
 237
 238 static void
 239 __flush_batch(journal_t *journal, int *batch_count)
 240 {
 241         int i;
 242         struct blk_plug plug;
 243
 244         blk_start_plug(&plug);
 245         for (i = 0; i < *batch_count; i++)
 246                 write_dirty_buffer(journal->j_chkpt_bhs[i], WRITE_SYNC);
 247         blk_finish_plug(&plug);
 248
 249         for (i = 0; i < *batch_count; i++) {
 250                 struct buffer_head *bh = journal->j_chkpt_bhs[i];
 251                 BUFFER_TRACE(bh, "brelse");
 252                 __brelse(bh);
 253         }
 254         *batch_count = 0;
 255 }
 256
 257 /*
 258  * Perform an actual checkpoint. We take the first transaction on the
 259  * list of transactions to be checkpointed and send all its buffers
 260  * to disk. We submit larger chunks of data at once.
 261  *
 262  * The journal should be locked before calling this function.
 263  * Called with j_checkpoint_mutex held.
 264  */
 265 int jbd2_log_do_checkpoint(journal_t *journal)
 266 {
 267         struct journal_head     *jh;
 268         struct buffer_head      *bh;
 269         transaction_t           *transaction;
 270         tid_t                   this_tid;
 271         int                     err, result, batch_count = 0;
 272
 273         jbd_debug(1, "Start checkpoint\n");
 274
 275         /*
 276          * First thing: if there are any transactions in the log which
 277          * don't need checkpointing, just eliminate them from the
 278          * journal straight away.
 279          */
 280         result = jbd2_cleanup_journal_tail(journal);
 281         trace_jbd2_checkpoint(journal, result);
 282         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 283         if (result <= 0)
 284                 return result;
 285
 286         /*
 287          * OK, we need to start writing disk blocks.  Take one transaction
 288          * and write it.
 289          */
 290         result = 0;
 291         spin_lock(&journal->j_list_lock);
 292         if (!journal->j_checkpoint_transactions)
 293                 goto out;
 294         transaction = journal->j_checkpoint_transactions;
 295         if (transaction->t_chp_stats.cs_chp_time == 0)
 296                 transaction->t_chp_stats.cs_chp_time = jiffies;
 297         this_tid = transaction->t_tid;
 298 restart:
 299         /*
 300          * If someone cleaned up this transaction while we slept, we're
 301          * done (maybe it's a new transaction, but it fell at the same
 302          * address).
 303          */
 304         if (journal->j_checkpoint_transactions != transaction ||
 305             transaction->t_tid != this_tid)
 306                 goto out;
 307
 308         /* checkpoint all of the transaction's buffers */
 309         while (transaction->t_checkpoint_list) {
 310                 jh = transaction->t_checkpoint_list;
 311                 bh = jh2bh(jh);
 312
 313                 if (buffer_locked(bh)) {
 314                         spin_unlock(&journal->j_list_lock);
 315                         get_bh(bh);
 316                         wait_on_buffer(bh);
 317                         /* the journal_head may have gone by now */
 318                         BUFFER_TRACE(bh, "brelse");
 319                         __brelse(bh);
 320                         goto retry;
 321                 }
 322                 if (jh->b_transaction != NULL) {
 323                         transaction_t *t = jh->b_transaction;
 324                         tid_t tid = t->t_tid;
 325
 326                         transaction->t_chp_stats.cs_forced_to_close++;
 327                         spin_unlock(&journal->j_list_lock);
 328                         if (unlikely(journal->j_flags & JBD2_UNMOUNT))
 329                                 /*
 330                                  * The journal thread is dead; so
 331                                  * starting and waiting for a commit
 332                                  * to finish will cause us to wait for
 333                                  * a _very_ long time.
 334                                  */
 335                                 printk(KERN_ERR
 336                 "JBD2: %s: Waiting for Godot: block %llu\n",
 337                 journal->j_devname, (unsigned long long) bh->b_blocknr);
 338
 339                         jbd2_log_start_commit(journal, tid);
 340                         jbd2_log_wait_commit(journal, tid);
 341                         goto retry;
 342                 }
 343                 if (!buffer_dirty(bh)) {
 344                         if (unlikely(buffer_write_io_error(bh)) && !result)
 345                                 result = -EIO;
 346                         get_bh(bh);
 347                         BUFFER_TRACE(bh, "remove from checkpoint");
 348                         __jbd2_journal_remove_checkpoint(jh);
 349                         spin_unlock(&journal->j_list_lock);
 350                         __brelse(bh);
 351                         goto retry;
 352                 }
 353                 /*
 354                  * Important: we are about to write the buffer, and
 355                  * possibly block, while still holding the journal
 356                  * lock.  We cannot afford to let the transaction
 357                  * logic start messing around with this buffer before
 358                  * we write it to disk, as that would break
 359                  * recoverability.
 360                  */
 361                 BUFFER_TRACE(bh, "queue");
 362                 get_bh(bh);
 363                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 364                 journal->j_chkpt_bhs[batch_count++] = bh;
 365                 __buffer_relink_io(jh);
 366                 transaction->t_chp_stats.cs_written++;
 367                 if ((batch_count == JBD2_NR_BATCH) ||
 368                     need_resched() ||
 369                     spin_needbreak(&journal->j_list_lock))
 370                         goto unlock_and_flush;
 371         }
 372
 373         if (batch_count) {
 374                 unlock_and_flush:
 375                         spin_unlock(&journal->j_list_lock);
 376                 retry:
 377                         if (batch_count)
 378                                 __flush_batch(journal, &batch_count);
 379                         spin_lock(&journal->j_list_lock);
 380                         goto restart;
 381         }
 382
 383         /*
 384          * Now we issued all of the transaction's buffers, let's deal
 385          * with the buffers that are out for I/O.
 386          */
 387         err = __wait_cp_io(journal, transaction);
 388         if (!result)
 389                 result = err;
 390 out:
 391         spin_unlock(&journal->j_list_lock);
 392         if (result < 0)
 393                 jbd2_journal_abort(journal, result);
 394         else
 395                 result = jbd2_cleanup_journal_tail(journal);
 396
 397         return (result < 0) ? result : 0;
 398 }
 399
 400 /*
 401  * Check the list of checkpoint transactions for the journal to see if
 402  * we have already got rid of any since the last update of the log tail
 403  * in the journal superblock.  If so, we can instantly roll the
 404  * superblock forward to remove those transactions from the log.
 405  *
 406  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 407  *
 408  * Called with the journal lock held.
 409  *
 410  * This is the only part of the journaling code which really needs to be
 411  * aware of transaction aborts.  Checkpointing involves writing to the
 412  * main filesystem area rather than to the journal, so it can proceed
 413  * even in abort state, but we must not update the super block if
 414  * checkpointing may have failed.  Otherwise, we would lose some metadata
 415  * buffers which should be written-back to the filesystem.
 416  */
 417
 418 int jbd2_cleanup_journal_tail(journal_t *journal)
 419 {
 420         tid_t           first_tid;
 421         unsigned long   blocknr;
 422
 423         if (is_journal_aborted(journal))
 424                 return 1;
 425
 426         if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
 427                 return 1;
 428         J_ASSERT(blocknr != 0);
 429
 430         /*
 431          * We need to make sure that any blocks that were recently written out
 432          * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
 433          * we drop the transactions from the journal. It's unlikely this will
 434          * be necessary, especially with an appropriately sized journal, but we
 435          * need this to guarantee correctness.  Fortunately
 436          * jbd2_cleanup_journal_tail() doesn't get called all that often.
 437          */
 438         if (journal->j_flags & JBD2_BARRIER)
 439                 blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
 440
 441         __jbd2_update_log_tail(journal, first_tid, blocknr);
 442         return 0;
 443 }
 444
 445
 446 /* Checkpoint list management */
 447
 448 /*
 449  * journal_clean_one_cp_list
 450  *
 451  * Find all the written-back checkpoint buffers in the given list and
 452  * release them.
 453  *
 454  * Called with the journal locked.
 455  * Called with j_list_lock held.
 456  * Returns number of buffers reaped (for debug)
 457  */
 458
 459 static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
 460 {
 461         struct journal_head *last_jh;
 462         struct journal_head *next_jh = jh;
 463         int ret, freed = 0;
 464
 465         *released = 0;
 466         if (!jh)
 467                 return 0;
 468
 469         last_jh = jh->b_cpprev;
 470         do {
 471                 jh = next_jh;
 472                 next_jh = jh->b_cpnext;
 473                 ret = __try_to_free_cp_buf(jh);
 474                 if (ret) {
 475                         freed++;
 476                         if (ret == 2) {
 477                                 *released = 1;
 478                                 return freed;
 479                         }
 480                 }
 481                 /*
 482                  * This function only frees up some memory
 483                  * if possible so we dont have an obligation
 484                  * to finish processing. Bail out if preemption
 485                  * requested:
 486                  */
 487                 if (need_resched())
 488                         return freed;
 489         } while (jh != last_jh);
 490
 491         return freed;
 492 }
 493
 494 /*
 495  * journal_clean_checkpoint_list
 496  *
 497  * Find all the written-back checkpoint buffers in the journal and release them.
 498  *
 499  * Called with the journal locked.
 500  * Called with j_list_lock held.
 501  * Returns number of buffers reaped (for debug)
 502  */
 503
 504 int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
 505 {
 506         transaction_t *transaction, *last_transaction, *next_transaction;
 507         int ret = 0;
 508         int released;
 509
 510         transaction = journal->j_checkpoint_transactions;
 511         if (!transaction)
 512                 goto out;
 513
 514         last_transaction = transaction->t_cpprev;
 515         next_transaction = transaction;
 516         do {
 517                 transaction = next_transaction;
 518                 next_transaction = transaction->t_cpnext;
 519                 ret += journal_clean_one_cp_list(transaction->
 520                                 t_checkpoint_list, &released);
 521                 /*
 522                  * This function only frees up some memory if possible so we
 523                  * dont have an obligation to finish processing. Bail out if
 524                  * preemption requested:
 525                  */
 526                 if (need_resched())
 527                         goto out;
 528                 if (released)
 529                         continue;
 530                 /*
 531                  * It is essential that we are as careful as in the case of
 532                  * t_checkpoint_list with removing the buffer from the list as
 533                  * we can possibly see not yet submitted buffers on io_list
 534                  */
 535                 ret += journal_clean_one_cp_list(transaction->
 536                                 t_checkpoint_io_list, &released);
 537                 if (need_resched())
 538                         goto out;
 539         } while (transaction != last_transaction);
 540 out:
 541         return ret;
 542 }
 543
 544 /*
 545  * journal_remove_checkpoint: called after a buffer has been committed
 546  * to disk (either by being write-back flushed to disk, or being
 547  * committed to the log).
 548  *
 549  * We cannot safely clean a transaction out of the log until all of the
 550  * buffer updates committed in that transaction have safely been stored
 551  * elsewhere on disk.  To achieve this, all of the buffers in a
 552  * transaction need to be maintained on the transaction's checkpoint
 553  * lists until they have been rewritten, at which point this function is
 554  * called to remove the buffer from the existing transaction's
 555  * checkpoint lists.
 556  *
 557  * The function returns 1 if it frees the transaction, 0 otherwise.
 558  * The function can free jh and bh.
 559  *
 560  * This function is called with j_list_lock held.
 561  */
 562 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 563 {
 564         struct transaction_chp_stats_s *stats;
 565         transaction_t *transaction;
 566         journal_t *journal;
 567         int ret = 0;
 568
 569         JBUFFER_TRACE(jh, "entry");
 570
 571         if ((transaction = jh->b_cp_transaction) == NULL) {
 572                 JBUFFER_TRACE(jh, "not on transaction");
 573                 goto out;
 574         }
 575         journal = transaction->t_journal;
 576
 577         JBUFFER_TRACE(jh, "removing from transaction");
 578         __buffer_unlink(jh);
 579         jh->b_cp_transaction = NULL;
 580         jbd2_journal_put_journal_head(jh);
 581
 582         if (transaction->t_checkpoint_list != NULL ||
 583             transaction->t_checkpoint_io_list != NULL)
 584                 goto out;
 585
 586         /*
 587          * There is one special case to worry about: if we have just pulled the
 588          * buffer off a running or committing transaction's checkpoing list,
 589          * then even if the checkpoint list is empty, the transaction obviously
 590          * cannot be dropped!
 591          *
 592          * The locking here around t_state is a bit sleazy.
 593          * See the comment at the end of jbd2_journal_commit_transaction().
 594          */
 595         if (transaction->t_state != T_FINISHED)
 596                 goto out;
 597
 598         /* OK, that was the last buffer for the transaction: we can now
 599            safely remove this transaction from the log */
 600         stats = &transaction->t_chp_stats;
 601         if (stats->cs_chp_time)
 602                 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
 603                                                     jiffies);
 604         trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
 605                                     transaction->t_tid, stats);
 606
 607         __jbd2_journal_drop_transaction(journal, transaction);
 608         jbd2_journal_free_transaction(transaction);
 609         ret = 1;
 610 out:
 611         return ret;
 612 }
 613
 614 /*
 615  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 616  * list so that we know when it is safe to clean the transaction out of
 617  * the log.
 618  *
 619  * Called with the journal locked.
 620  * Called with j_list_lock held.
 621  */
 622 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
 623                                transaction_t *transaction)
 624 {
 625         JBUFFER_TRACE(jh, "entry");
 626         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 627         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 628
 629         /* Get reference for checkpointing transaction */
 630         jbd2_journal_grab_journal_head(jh2bh(jh));
 631         jh->b_cp_transaction = transaction;
 632
 633         if (!transaction->t_checkpoint_list) {
 634                 jh->b_cpnext = jh->b_cpprev = jh;
 635         } else {
 636                 jh->b_cpnext = transaction->t_checkpoint_list;
 637                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 638                 jh->b_cpprev->b_cpnext = jh;
 639                 jh->b_cpnext->b_cpprev = jh;
 640         }
 641         transaction->t_checkpoint_list = jh;
 642 }
 643
 644 /*
 645  * We've finished with this transaction structure: adios...
 646  *
 647  * The transaction must have no links except for the checkpoint by this
 648  * point.
 649  *
 650  * Called with the journal locked.
 651  * Called with j_list_lock held.
 652  */
 653
 654 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 655 {
 656         assert_spin_locked(&journal->j_list_lock);
 657         if (transaction->t_cpnext) {
 658                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 659                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 660                 if (journal->j_checkpoint_transactions == transaction)
 661                         journal->j_checkpoint_transactions =
 662                                 transaction->t_cpnext;
 663                 if (journal->j_checkpoint_transactions == transaction)
 664                         journal->j_checkpoint_transactions = NULL;
 665         }
 666
 667         J_ASSERT(transaction->t_state == T_FINISHED);
 668         J_ASSERT(transaction->t_buffers == NULL);
 669         J_ASSERT(transaction->t_forget == NULL);
 670         J_ASSERT(transaction->t_shadow_list == NULL);
 671         J_ASSERT(transaction->t_checkpoint_list == NULL);
 672         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 673         J_ASSERT(atomic_read(&transaction->t_updates) == 0);
 674         J_ASSERT(journal->j_committing_transaction != transaction);
 675         J_ASSERT(journal->j_running_transaction != transaction);
 676
 677         trace_jbd2_drop_transaction(journal, transaction);
 678
 679         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 680 }