kernel/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                 JBUFFER_TRACE(jh, "remove from checkpoint list");
 100                 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
 101         }
 102         return ret;
 103 }
 104
 105 /*
 106  * __jbd2_log_wait_for_space: wait until there is space in the journal.
 107  *
 108  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
 109  * for a checkpoint to free up some space in the log.
 110  */
 111 void __jbd2_log_wait_for_space(journal_t *journal)
 112 {
 113         int nblocks, space_left;
 114         /* assert_spin_locked(&journal->j_state_lock); */
 115
 116         nblocks = jbd2_space_needed(journal);
 117         while (jbd2_log_space_left(journal) < nblocks) {
 118                 write_unlock(&journal->j_state_lock);
 119                 if (current->plug)
 120                         io_schedule();
 121                 mutex_lock(&journal->j_checkpoint_mutex);
 122
 123                 /*
 124                  * Test again, another process may have checkpointed while we
 125                  * were waiting for the checkpoint lock. If there are no
 126                  * transactions ready to be checkpointed, try to recover
 127                  * journal space by calling cleanup_journal_tail(), and if
 128                  * that doesn't work, by waiting for the currently committing
 129                  * transaction to complete.  If there is absolutely no way
 130                  * to make progress, this is either a BUG or corrupted
 131                  * filesystem, so abort the journal and leave a stack
 132                  * trace for forensic evidence.
 133                  */
 134                 write_lock(&journal->j_state_lock);
 135                 if (journal->j_flags & JBD2_ABORT) {
 136                         mutex_unlock(&journal->j_checkpoint_mutex);
 137                         return;
 138                 }
 139                 spin_lock(&journal->j_list_lock);
 140                 nblocks = jbd2_space_needed(journal);
 141                 space_left = jbd2_log_space_left(journal);
 142                 if (space_left < nblocks) {
 143                         int chkpt = journal->j_checkpoint_transactions != NULL;
 144                         tid_t tid = 0;
 145
 146                         if (journal->j_committing_transaction)
 147                                 tid = journal->j_committing_transaction->t_tid;
 148                         spin_unlock(&journal->j_list_lock);
 149                         write_unlock(&journal->j_state_lock);
 150                         if (chkpt) {
 151                                 jbd2_log_do_checkpoint(journal);
 152                         } else if (jbd2_cleanup_journal_tail(journal) == 0) {
 153                                 /* We were able to recover space; yay! */
 154                                 ;
 155                         } else if (tid) {
 156                                 /*
 157                                  * jbd2_journal_commit_transaction() may want
 158                                  * to take the checkpoint_mutex if JBD2_FLUSHED
 159                                  * is set.  So we need to temporarily drop it.
 160                                  */
 161                                 mutex_unlock(&journal->j_checkpoint_mutex);
 162                                 jbd2_log_wait_commit(journal, tid);
 163                                 write_lock(&journal->j_state_lock);
 164                                 continue;
 165                         } else {
 166                                 printk(KERN_ERR "%s: needed %d blocks and "
 167                                        "only had %d space available\n",
 168                                        __func__, nblocks, space_left);
 169                                 printk(KERN_ERR "%s: no way to get more "
 170                                        "journal space in %s\n", __func__,
 171                                        journal->j_devname);
 172                                 WARN_ON(1);
 173                                 jbd2_journal_abort(journal, 0);
 174                         }
 175                         write_lock(&journal->j_state_lock);
 176                 } else {
 177                         spin_unlock(&journal->j_list_lock);
 178                 }
 179                 mutex_unlock(&journal->j_checkpoint_mutex);
 180         }
 181 }
 182
 183 static void
 184 __flush_batch(journal_t *journal, int *batch_count)
 185 {
 186         int i;
 187         struct blk_plug plug;
 188
 189         blk_start_plug(&plug);
 190         for (i = 0; i < *batch_count; i++)
 191                 write_dirty_buffer(journal->j_chkpt_bhs[i], WRITE_SYNC);
 192         blk_finish_plug(&plug);
 193
 194         for (i = 0; i < *batch_count; i++) {
 195                 struct buffer_head *bh = journal->j_chkpt_bhs[i];
 196                 BUFFER_TRACE(bh, "brelse");
 197                 __brelse(bh);
 198         }
 199         *batch_count = 0;
 200 }
 201
 202 /*
 203  * Perform an actual checkpoint. We take the first transaction on the
 204  * list of transactions to be checkpointed and send all its buffers
 205  * to disk. We submit larger chunks of data at once.
 206  *
 207  * The journal should be locked before calling this function.
 208  * Called with j_checkpoint_mutex held.
 209  */
 210 int jbd2_log_do_checkpoint(journal_t *journal)
 211 {
 212         struct journal_head     *jh;
 213         struct buffer_head      *bh;
 214         transaction_t           *transaction;
 215         tid_t                   this_tid;
 216         int                     result, batch_count = 0;
 217
 218         jbd_debug(1, "Start checkpoint\n");
 219
 220         /*
 221          * First thing: if there are any transactions in the log which
 222          * don't need checkpointing, just eliminate them from the
 223          * journal straight away.
 224          */
 225         result = jbd2_cleanup_journal_tail(journal);
 226         trace_jbd2_checkpoint(journal, result);
 227         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 228         if (result <= 0)
 229                 return result;
 230
 231         /*
 232          * OK, we need to start writing disk blocks.  Take one transaction
 233          * and write it.
 234          */
 235         result = 0;
 236         spin_lock(&journal->j_list_lock);
 237         if (!journal->j_checkpoint_transactions)
 238                 goto out;
 239         transaction = journal->j_checkpoint_transactions;
 240         if (transaction->t_chp_stats.cs_chp_time == 0)
 241                 transaction->t_chp_stats.cs_chp_time = jiffies;
 242         this_tid = transaction->t_tid;
 243 restart:
 244         /*
 245          * If someone cleaned up this transaction while we slept, we're
 246          * done (maybe it's a new transaction, but it fell at the same
 247          * address).
 248          */
 249         if (journal->j_checkpoint_transactions != transaction ||
 250             transaction->t_tid != this_tid)
 251                 goto out;
 252
 253         /* checkpoint all of the transaction's buffers */
 254         while (transaction->t_checkpoint_list) {
 255                 jh = transaction->t_checkpoint_list;
 256                 bh = jh2bh(jh);
 257
 258                 if (buffer_locked(bh)) {
 259                         spin_unlock(&journal->j_list_lock);
 260                         get_bh(bh);
 261                         wait_on_buffer(bh);
 262                         /* the journal_head may have gone by now */
 263                         BUFFER_TRACE(bh, "brelse");
 264                         __brelse(bh);
 265                         goto retry;
 266                 }
 267                 if (jh->b_transaction != NULL) {
 268                         transaction_t *t = jh->b_transaction;
 269                         tid_t tid = t->t_tid;
 270
 271                         transaction->t_chp_stats.cs_forced_to_close++;
 272                         spin_unlock(&journal->j_list_lock);
 273                         if (unlikely(journal->j_flags & JBD2_UNMOUNT))
 274                                 /*
 275                                  * The journal thread is dead; so
 276                                  * starting and waiting for a commit
 277                                  * to finish will cause us to wait for
 278                                  * a _very_ long time.
 279                                  */
 280                                 printk(KERN_ERR
 281                 "JBD2: %s: Waiting for Godot: block %llu\n",
 282                 journal->j_devname, (unsigned long long) bh->b_blocknr);
 283
 284                         jbd2_log_start_commit(journal, tid);
 285                         jbd2_log_wait_commit(journal, tid);
 286                         goto retry;
 287                 }
 288                 if (!buffer_dirty(bh)) {
 289                         if (unlikely(buffer_write_io_error(bh)) && !result)
 290                                 result = -EIO;
 291                         BUFFER_TRACE(bh, "remove from checkpoint");
 292                         if (__jbd2_journal_remove_checkpoint(jh))
 293                                 /* The transaction was released; we're done */
 294                                 goto out;
 295                         continue;
 296                 }
 297                 /*
 298                  * Important: we are about to write the buffer, and
 299                  * possibly block, while still holding the journal
 300                  * lock.  We cannot afford to let the transaction
 301                  * logic start messing around with this buffer before
 302                  * we write it to disk, as that would break
 303                  * recoverability.
 304                  */
 305                 BUFFER_TRACE(bh, "queue");
 306                 get_bh(bh);
 307                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 308                 journal->j_chkpt_bhs[batch_count++] = bh;
 309                 __buffer_relink_io(jh);
 310                 transaction->t_chp_stats.cs_written++;
 311                 if ((batch_count == JBD2_NR_BATCH) ||
 312                     need_resched() ||
 313                     spin_needbreak(&journal->j_list_lock))
 314                         goto unlock_and_flush;
 315         }
 316
 317         if (batch_count) {
 318                 unlock_and_flush:
 319                         spin_unlock(&journal->j_list_lock);
 320                 retry:
 321                         if (batch_count)
 322                                 __flush_batch(journal, &batch_count);
 323                         spin_lock(&journal->j_list_lock);
 324                         goto restart;
 325         }
 326
 327         /*
 328          * Now we issued all of the transaction's buffers, let's deal
 329          * with the buffers that are out for I/O.
 330          */
 331 restart2:
 332         /* Did somebody clean up the transaction in the meanwhile? */
 333         if (journal->j_checkpoint_transactions != transaction ||
 334             transaction->t_tid != this_tid)
 335                 goto out;
 336
 337         while (transaction->t_checkpoint_io_list) {
 338                 jh = transaction->t_checkpoint_io_list;
 339                 bh = jh2bh(jh);
 340                 if (buffer_locked(bh)) {
 341                         spin_unlock(&journal->j_list_lock);
 342                         get_bh(bh);
 343                         wait_on_buffer(bh);
 344                         /* the journal_head may have gone by now */
 345                         BUFFER_TRACE(bh, "brelse");
 346                         __brelse(bh);
 347                         spin_lock(&journal->j_list_lock);
 348                         goto restart2;
 349                 }
 350                 if (unlikely(buffer_write_io_error(bh)) && !result)
 351                         result = -EIO;
 352
 353                 /*
 354                  * Now in whatever state the buffer currently is, we
 355                  * know that it has been written out and so we can
 356                  * drop it from the list
 357                  */
 358                 if (__jbd2_journal_remove_checkpoint(jh))
 359                         break;
 360         }
 361 out:
 362         spin_unlock(&journal->j_list_lock);
 363         if (result < 0)
 364                 jbd2_journal_abort(journal, result);
 365         else
 366                 result = jbd2_cleanup_journal_tail(journal);
 367
 368         return (result < 0) ? result : 0;
 369 }
 370
 371 /*
 372  * Check the list of checkpoint transactions for the journal to see if
 373  * we have already got rid of any since the last update of the log tail
 374  * in the journal superblock.  If so, we can instantly roll the
 375  * superblock forward to remove those transactions from the log.
 376  *
 377  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 378  *
 379  * Called with the journal lock held.
 380  *
 381  * This is the only part of the journaling code which really needs to be
 382  * aware of transaction aborts.  Checkpointing involves writing to the
 383  * main filesystem area rather than to the journal, so it can proceed
 384  * even in abort state, but we must not update the super block if
 385  * checkpointing may have failed.  Otherwise, we would lose some metadata
 386  * buffers which should be written-back to the filesystem.
 387  */
 388
 389 int jbd2_cleanup_journal_tail(journal_t *journal)
 390 {
 391         tid_t           first_tid;
 392         unsigned long   blocknr;
 393
 394         if (is_journal_aborted(journal))
 395                 return -EIO;
 396
 397         if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
 398                 return 1;
 399         J_ASSERT(blocknr != 0);
 400
 401         /*
 402          * We need to make sure that any blocks that were recently written out
 403          * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
 404          * we drop the transactions from the journal. It's unlikely this will
 405          * be necessary, especially with an appropriately sized journal, but we
 406          * need this to guarantee correctness.  Fortunately
 407          * jbd2_cleanup_journal_tail() doesn't get called all that often.
 408          */
 409         if (journal->j_flags & JBD2_BARRIER)
 410                 blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS, NULL);
 411
 412         return __jbd2_update_log_tail(journal, first_tid, blocknr);
 413 }
 414
 415
 416 /* Checkpoint list management */
 417
 418 /*
 419  * journal_clean_one_cp_list
 420  *
 421  * Find all the written-back checkpoint buffers in the given list and
 422  * release them. If 'destroy' is set, clean all buffers unconditionally.
 423  *
 424  * Called with j_list_lock held.
 425  * Returns 1 if we freed the transaction, 0 otherwise.
 426  */
 427 static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
 428 {
 429         struct journal_head *last_jh;
 430         struct journal_head *next_jh = jh;
 431         int ret;
 432         int freed = 0;
 433
 434         if (!jh)
 435                 return 0;
 436
 437         last_jh = jh->b_cpprev;
 438         do {
 439                 jh = next_jh;
 440                 next_jh = jh->b_cpnext;
 441                 if (!destroy)
 442                         ret = __try_to_free_cp_buf(jh);
 443                 else
 444                         ret = __jbd2_journal_remove_checkpoint(jh) + 1;
 445                 if (!ret)
 446                         return freed;
 447                 if (ret == 2)
 448                         return 1;
 449                 freed = 1;
 450                 /*
 451                  * This function only frees up some memory
 452                  * if possible so we dont have an obligation
 453                  * to finish processing. Bail out if preemption
 454                  * requested:
 455                  */
 456                 if (need_resched())
 457                         return freed;
 458         } while (jh != last_jh);
 459
 460         return freed;
 461 }
 462
 463 /*
 464  * journal_clean_checkpoint_list
 465  *
 466  * Find all the written-back checkpoint buffers in the journal and release them.
 467  * If 'destroy' is set, release all buffers unconditionally.
 468  *
 469  * Called with j_list_lock held.
 470  */
 471 void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
 472 {
 473         transaction_t *transaction, *last_transaction, *next_transaction;
 474         int ret;
 475
 476         transaction = journal->j_checkpoint_transactions;
 477         if (!transaction)
 478                 return;
 479
 480         last_transaction = transaction->t_cpprev;
 481         next_transaction = transaction;
 482         do {
 483                 transaction = next_transaction;
 484                 next_transaction = transaction->t_cpnext;
 485                 ret = journal_clean_one_cp_list(transaction->t_checkpoint_list,
 486                                                 destroy);
 487                 /*
 488                  * This function only frees up some memory if possible so we
 489                  * dont have an obligation to finish processing. Bail out if
 490                  * preemption requested:
 491                  */
 492                 if (need_resched())
 493                         return;
 494                 if (ret)
 495                         continue;
 496                 /*
 497                  * It is essential that we are as careful as in the case of
 498                  * t_checkpoint_list with removing the buffer from the list as
 499                  * we can possibly see not yet submitted buffers on io_list
 500                  */
 501                 ret = journal_clean_one_cp_list(transaction->
 502                                 t_checkpoint_io_list, destroy);
 503                 if (need_resched())
 504                         return;
 505                 /*
 506                  * Stop scanning if we couldn't free the transaction. This
 507                  * avoids pointless scanning of transactions which still
 508                  * weren't checkpointed.
 509                  */
 510                 if (!ret)
 511                         return;
 512         } while (transaction != last_transaction);
 513 }
 514
 515 /*
 516  * Remove buffers from all checkpoint lists as journal is aborted and we just
 517  * need to free memory
 518  */
 519 void jbd2_journal_destroy_checkpoint(journal_t *journal)
 520 {
 521         /*
 522          * We loop because __jbd2_journal_clean_checkpoint_list() may abort
 523          * early due to a need of rescheduling.
 524          */
 525         while (1) {
 526                 spin_lock(&journal->j_list_lock);
 527                 if (!journal->j_checkpoint_transactions) {
 528                         spin_unlock(&journal->j_list_lock);
 529                         break;
 530                 }
 531                 __jbd2_journal_clean_checkpoint_list(journal, true);
 532                 spin_unlock(&journal->j_list_lock);
 533                 cond_resched();
 534         }
 535 }
 536
 537 /*
 538  * journal_remove_checkpoint: called after a buffer has been committed
 539  * to disk (either by being write-back flushed to disk, or being
 540  * committed to the log).
 541  *
 542  * We cannot safely clean a transaction out of the log until all of the
 543  * buffer updates committed in that transaction have safely been stored
 544  * elsewhere on disk.  To achieve this, all of the buffers in a
 545  * transaction need to be maintained on the transaction's checkpoint
 546  * lists until they have been rewritten, at which point this function is
 547  * called to remove the buffer from the existing transaction's
 548  * checkpoint lists.
 549  *
 550  * The function returns 1 if it frees the transaction, 0 otherwise.
 551  * The function can free jh and bh.
 552  *
 553  * This function is called with j_list_lock held.
 554  */
 555 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 556 {
 557         struct transaction_chp_stats_s *stats;
 558         transaction_t *transaction;
 559         journal_t *journal;
 560         int ret = 0;
 561
 562         JBUFFER_TRACE(jh, "entry");
 563
 564         if ((transaction = jh->b_cp_transaction) == NULL) {
 565                 JBUFFER_TRACE(jh, "not on transaction");
 566                 goto out;
 567         }
 568         journal = transaction->t_journal;
 569
 570         JBUFFER_TRACE(jh, "removing from transaction");
 571         __buffer_unlink(jh);
 572         jh->b_cp_transaction = NULL;
 573         jbd2_journal_put_journal_head(jh);
 574
 575         if (transaction->t_checkpoint_list != NULL ||
 576             transaction->t_checkpoint_io_list != NULL)
 577                 goto out;
 578
 579         /*
 580          * There is one special case to worry about: if we have just pulled the
 581          * buffer off a running or committing transaction's checkpoing list,
 582          * then even if the checkpoint list is empty, the transaction obviously
 583          * cannot be dropped!
 584          *
 585          * The locking here around t_state is a bit sleazy.
 586          * See the comment at the end of jbd2_journal_commit_transaction().
 587          */
 588         if (transaction->t_state != T_FINISHED)
 589                 goto out;
 590
 591         /* OK, that was the last buffer for the transaction: we can now
 592            safely remove this transaction from the log */
 593         stats = &transaction->t_chp_stats;
 594         if (stats->cs_chp_time)
 595                 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
 596                                                     jiffies);
 597         trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
 598                                     transaction->t_tid, stats);
 599
 600         __jbd2_journal_drop_transaction(journal, transaction);
 601         jbd2_journal_free_transaction(transaction);
 602         ret = 1;
 603 out:
 604         return ret;
 605 }
 606
 607 /*
 608  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 609  * list so that we know when it is safe to clean the transaction out of
 610  * the log.
 611  *
 612  * Called with the journal locked.
 613  * Called with j_list_lock held.
 614  */
 615 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
 616                                transaction_t *transaction)
 617 {
 618         JBUFFER_TRACE(jh, "entry");
 619         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 620         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 621
 622         /* Get reference for checkpointing transaction */
 623         jbd2_journal_grab_journal_head(jh2bh(jh));
 624         jh->b_cp_transaction = transaction;
 625
 626         if (!transaction->t_checkpoint_list) {
 627                 jh->b_cpnext = jh->b_cpprev = jh;
 628         } else {
 629                 jh->b_cpnext = transaction->t_checkpoint_list;
 630                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 631                 jh->b_cpprev->b_cpnext = jh;
 632                 jh->b_cpnext->b_cpprev = jh;
 633         }
 634         transaction->t_checkpoint_list = jh;
 635 }
 636
 637 /*
 638  * We've finished with this transaction structure: adios...
 639  *
 640  * The transaction must have no links except for the checkpoint by this
 641  * point.
 642  *
 643  * Called with the journal locked.
 644  * Called with j_list_lock held.
 645  */
 646
 647 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 648 {
 649         assert_spin_locked(&journal->j_list_lock);
 650         if (transaction->t_cpnext) {
 651                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 652                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 653                 if (journal->j_checkpoint_transactions == transaction)
 654                         journal->j_checkpoint_transactions =
 655                                 transaction->t_cpnext;
 656                 if (journal->j_checkpoint_transactions == transaction)
 657                         journal->j_checkpoint_transactions = NULL;
 658         }
 659
 660         J_ASSERT(transaction->t_state == T_FINISHED);
 661         J_ASSERT(transaction->t_buffers == NULL);
 662         J_ASSERT(transaction->t_forget == NULL);
 663         J_ASSERT(transaction->t_shadow_list == NULL);
 664         J_ASSERT(transaction->t_checkpoint_list == NULL);
 665         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 666         J_ASSERT(atomic_read(&transaction->t_updates) == 0);
 667         J_ASSERT(journal->j_committing_transaction != transaction);
 668         J_ASSERT(journal->j_running_transaction != transaction);
 669
 670         trace_jbd2_drop_transaction(journal, transaction);
 671
 672         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 673 }