fs/jbd2/checkpoint.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * linux/fs/jbd2/checkpoint.c
   4  *
   5  * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
   6  *
   7  * Copyright 1999 Red Hat Software --- All Rights Reserved
   8  *
   9  * Checkpoint routines for the generic filesystem journaling code.
  10  * Part of the ext2fs journaling system.
  11  *
  12  * Checkpointing is the process of ensuring that a section of the log is
  13  * committed fully to disk, so that that portion of the log can be
  14  * reused.
  15  */
  16
  17 #include <linux/time.h>
  18 #include <linux/fs.h>
  19 #include <linux/jbd2.h>
  20 #include <linux/errno.h>
  21 #include <linux/slab.h>
  22 #include <linux/blkdev.h>
  23 #include <trace/events/jbd2.h>
  24
  25 /*
  26  * Unlink a buffer from a transaction checkpoint list.
  27  *
  28  * Called with j_list_lock held.
  29  */
  30 static inline void __buffer_unlink_first(struct journal_head *jh)
  31 {
  32         transaction_t *transaction = jh->b_cp_transaction;
  33
  34         jh->b_cpnext->b_cpprev = jh->b_cpprev;
  35         jh->b_cpprev->b_cpnext = jh->b_cpnext;
  36         if (transaction->t_checkpoint_list == jh) {
  37                 transaction->t_checkpoint_list = jh->b_cpnext;
  38                 if (transaction->t_checkpoint_list == jh)
  39                         transaction->t_checkpoint_list = NULL;
  40         }
  41 }
  42
  43 /*
  44  * Unlink a buffer from a transaction checkpoint(io) list.
  45  *
  46  * Called with j_list_lock held.
  47  */
  48 static inline void __buffer_unlink(struct journal_head *jh)
  49 {
  50         transaction_t *transaction = jh->b_cp_transaction;
  51
  52         __buffer_unlink_first(jh);
  53         if (transaction->t_checkpoint_io_list == jh) {
  54                 transaction->t_checkpoint_io_list = jh->b_cpnext;
  55                 if (transaction->t_checkpoint_io_list == jh)
  56                         transaction->t_checkpoint_io_list = NULL;
  57         }
  58 }
  59
  60 /*
  61  * Move a buffer from the checkpoint list to the checkpoint io list
  62  *
  63  * Called with j_list_lock held
  64  */
  65 static inline void __buffer_relink_io(struct journal_head *jh)
  66 {
  67         transaction_t *transaction = jh->b_cp_transaction;
  68
  69         __buffer_unlink_first(jh);
  70
  71         if (!transaction->t_checkpoint_io_list) {
  72                 jh->b_cpnext = jh->b_cpprev = jh;
  73         } else {
  74                 jh->b_cpnext = transaction->t_checkpoint_io_list;
  75                 jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
  76                 jh->b_cpprev->b_cpnext = jh;
  77                 jh->b_cpnext->b_cpprev = jh;
  78         }
  79         transaction->t_checkpoint_io_list = jh;
  80 }
  81
  82 /*
  83  * Try to release a checkpointed buffer from its transaction.
  84  * Returns 1 if we released it and 2 if we also released the
  85  * whole transaction.
  86  *
  87  * Requires j_list_lock
  88  */
  89 static int __try_to_free_cp_buf(struct journal_head *jh)
  90 {
  91         int ret = 0;
  92         struct buffer_head *bh = jh2bh(jh);
  93
  94         if (jh->b_transaction == NULL && !buffer_locked(bh) &&
  95             !buffer_dirty(bh) && !buffer_write_io_error(bh)) {
  96                 JBUFFER_TRACE(jh, "remove from checkpoint list");
  97                 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
  98         }
  99         return ret;
 100 }
 101
 102 /*
 103  * __jbd2_log_wait_for_space: wait until there is space in the journal.
 104  *
 105  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
 106  * for a checkpoint to free up some space in the log.
 107  */
 108 void __jbd2_log_wait_for_space(journal_t *journal)
 109 {
 110         int nblocks, space_left;
 111         /* assert_spin_locked(&journal->j_state_lock); */
 112
 113         nblocks = jbd2_space_needed(journal);
 114         while (jbd2_log_space_left(journal) < nblocks) {
 115                 write_unlock(&journal->j_state_lock);
 116                 mutex_lock_io(&journal->j_checkpoint_mutex);
 117
 118                 /*
 119                  * Test again, another process may have checkpointed while we
 120                  * were waiting for the checkpoint lock. If there are no
 121                  * transactions ready to be checkpointed, try to recover
 122                  * journal space by calling cleanup_journal_tail(), and if
 123                  * that doesn't work, by waiting for the currently committing
 124                  * transaction to complete.  If there is absolutely no way
 125                  * to make progress, this is either a BUG or corrupted
 126                  * filesystem, so abort the journal and leave a stack
 127                  * trace for forensic evidence.
 128                  */
 129                 write_lock(&journal->j_state_lock);
 130                 if (journal->j_flags & JBD2_ABORT) {
 131                         mutex_unlock(&journal->j_checkpoint_mutex);
 132                         return;
 133                 }
 134                 spin_lock(&journal->j_list_lock);
 135                 space_left = jbd2_log_space_left(journal);
 136                 if (space_left < nblocks) {
 137                         int chkpt = journal->j_checkpoint_transactions != NULL;
 138                         tid_t tid = 0;
 139
 140                         if (journal->j_committing_transaction)
 141                                 tid = journal->j_committing_transaction->t_tid;
 142                         spin_unlock(&journal->j_list_lock);
 143                         write_unlock(&journal->j_state_lock);
 144                         if (chkpt) {
 145                                 jbd2_log_do_checkpoint(journal);
 146                         } else if (jbd2_cleanup_journal_tail(journal) == 0) {
 147                                 /* We were able to recover space; yay! */
 148                                 ;
 149                         } else if (tid) {
 150                                 /*
 151                                  * jbd2_journal_commit_transaction() may want
 152                                  * to take the checkpoint_mutex if JBD2_FLUSHED
 153                                  * is set.  So we need to temporarily drop it.
 154                                  */
 155                                 mutex_unlock(&journal->j_checkpoint_mutex);
 156                                 jbd2_log_wait_commit(journal, tid);
 157                                 write_lock(&journal->j_state_lock);
 158                                 continue;
 159                         } else {
 160                                 printk(KERN_ERR "%s: needed %d blocks and "
 161                                        "only had %d space available\n",
 162                                        __func__, nblocks, space_left);
 163                                 printk(KERN_ERR "%s: no way to get more "
 164                                        "journal space in %s\n", __func__,
 165                                        journal->j_devname);
 166                                 WARN_ON(1);
 167                                 jbd2_journal_abort(journal, 0);
 168                         }
 169                         write_lock(&journal->j_state_lock);
 170                 } else {
 171                         spin_unlock(&journal->j_list_lock);
 172                 }
 173                 mutex_unlock(&journal->j_checkpoint_mutex);
 174         }
 175 }
 176
 177 static void
 178 __flush_batch(journal_t *journal, int *batch_count)
 179 {
 180         int i;
 181         struct blk_plug plug;
 182
 183         blk_start_plug(&plug);
 184         for (i = 0; i < *batch_count; i++)
 185                 write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
 186         blk_finish_plug(&plug);
 187
 188         for (i = 0; i < *batch_count; i++) {
 189                 struct buffer_head *bh = journal->j_chkpt_bhs[i];
 190                 BUFFER_TRACE(bh, "brelse");
 191                 __brelse(bh);
 192         }
 193         *batch_count = 0;
 194 }
 195
 196 /*
 197  * Perform an actual checkpoint. We take the first transaction on the
 198  * list of transactions to be checkpointed and send all its buffers
 199  * to disk. We submit larger chunks of data at once.
 200  *
 201  * The journal should be locked before calling this function.
 202  * Called with j_checkpoint_mutex held.
 203  */
 204 int jbd2_log_do_checkpoint(journal_t *journal)
 205 {
 206         struct journal_head     *jh;
 207         struct buffer_head      *bh;
 208         transaction_t           *transaction;
 209         tid_t                   this_tid;
 210         int                     result, batch_count = 0;
 211
 212         jbd_debug(1, "Start checkpoint\n");
 213
 214         /*
 215          * First thing: if there are any transactions in the log which
 216          * don't need checkpointing, just eliminate them from the
 217          * journal straight away.
 218          */
 219         result = jbd2_cleanup_journal_tail(journal);
 220         trace_jbd2_checkpoint(journal, result);
 221         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 222         if (result <= 0)
 223                 return result;
 224
 225         /*
 226          * OK, we need to start writing disk blocks.  Take one transaction
 227          * and write it.
 228          */
 229         result = 0;
 230         spin_lock(&journal->j_list_lock);
 231         if (!journal->j_checkpoint_transactions)
 232                 goto out;
 233         transaction = journal->j_checkpoint_transactions;
 234         if (transaction->t_chp_stats.cs_chp_time == 0)
 235                 transaction->t_chp_stats.cs_chp_time = jiffies;
 236         this_tid = transaction->t_tid;
 237 restart:
 238         /*
 239          * If someone cleaned up this transaction while we slept, we're
 240          * done (maybe it's a new transaction, but it fell at the same
 241          * address).
 242          */
 243         if (journal->j_checkpoint_transactions != transaction ||
 244             transaction->t_tid != this_tid)
 245                 goto out;
 246
 247         /* checkpoint all of the transaction's buffers */
 248         while (transaction->t_checkpoint_list) {
 249                 jh = transaction->t_checkpoint_list;
 250                 bh = jh2bh(jh);
 251
 252                 if (buffer_locked(bh)) {
 253                         get_bh(bh);
 254                         spin_unlock(&journal->j_list_lock);
 255                         wait_on_buffer(bh);
 256                         /* the journal_head may have gone by now */
 257                         BUFFER_TRACE(bh, "brelse");
 258                         __brelse(bh);
 259                         goto retry;
 260                 }
 261                 if (jh->b_transaction != NULL) {
 262                         transaction_t *t = jh->b_transaction;
 263                         tid_t tid = t->t_tid;
 264
 265                         transaction->t_chp_stats.cs_forced_to_close++;
 266                         spin_unlock(&journal->j_list_lock);
 267                         if (unlikely(journal->j_flags & JBD2_UNMOUNT))
 268                                 /*
 269                                  * The journal thread is dead; so
 270                                  * starting and waiting for a commit
 271                                  * to finish will cause us to wait for
 272                                  * a _very_ long time.
 273                                  */
 274                                 printk(KERN_ERR
 275                 "JBD2: %s: Waiting for Godot: block %llu\n",
 276                 journal->j_devname, (unsigned long long) bh->b_blocknr);
 277
 278                         if (batch_count)
 279                                 __flush_batch(journal, &batch_count);
 280                         jbd2_log_start_commit(journal, tid);
 281                         /*
 282                          * jbd2_journal_commit_transaction() may want
 283                          * to take the checkpoint_mutex if JBD2_FLUSHED
 284                          * is set, jbd2_update_log_tail() called by
 285                          * jbd2_journal_commit_transaction() may also take
 286                          * checkpoint_mutex.  So we need to temporarily
 287                          * drop it.
 288                          */
 289                         mutex_unlock(&journal->j_checkpoint_mutex);
 290                         jbd2_log_wait_commit(journal, tid);
 291                         mutex_lock_io(&journal->j_checkpoint_mutex);
 292                         spin_lock(&journal->j_list_lock);
 293                         goto restart;
 294                 }
 295                 if (!buffer_dirty(bh)) {
 296                         if (unlikely(buffer_write_io_error(bh)) && !result)
 297                                 result = -EIO;
 298                         BUFFER_TRACE(bh, "remove from checkpoint");
 299                         if (__jbd2_journal_remove_checkpoint(jh))
 300                                 /* The transaction was released; we're done */
 301                                 goto out;
 302                         continue;
 303                 }
 304                 /*
 305                  * Important: we are about to write the buffer, and
 306                  * possibly block, while still holding the journal
 307                  * lock.  We cannot afford to let the transaction
 308                  * logic start messing around with this buffer before
 309                  * we write it to disk, as that would break
 310                  * recoverability.
 311                  */
 312                 BUFFER_TRACE(bh, "queue");
 313                 get_bh(bh);
 314                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 315                 journal->j_chkpt_bhs[batch_count++] = bh;
 316                 __buffer_relink_io(jh);
 317                 transaction->t_chp_stats.cs_written++;
 318                 if ((batch_count == JBD2_NR_BATCH) ||
 319                     need_resched() ||
 320                     spin_needbreak(&journal->j_list_lock))
 321                         goto unlock_and_flush;
 322         }
 323
 324         if (batch_count) {
 325                 unlock_and_flush:
 326                         spin_unlock(&journal->j_list_lock);
 327                 retry:
 328                         if (batch_count)
 329                                 __flush_batch(journal, &batch_count);
 330                         spin_lock(&journal->j_list_lock);
 331                         goto restart;
 332         }
 333
 334         /*
 335          * Now we issued all of the transaction's buffers, let's deal
 336          * with the buffers that are out for I/O.
 337          */
 338 restart2:
 339         /* Did somebody clean up the transaction in the meanwhile? */
 340         if (journal->j_checkpoint_transactions != transaction ||
 341             transaction->t_tid != this_tid)
 342                 goto out;
 343
 344         while (transaction->t_checkpoint_io_list) {
 345                 jh = transaction->t_checkpoint_io_list;
 346                 bh = jh2bh(jh);
 347                 if (buffer_locked(bh)) {
 348                         get_bh(bh);
 349                         spin_unlock(&journal->j_list_lock);
 350                         wait_on_buffer(bh);
 351                         /* the journal_head may have gone by now */
 352                         BUFFER_TRACE(bh, "brelse");
 353                         __brelse(bh);
 354                         spin_lock(&journal->j_list_lock);
 355                         goto restart2;
 356                 }
 357                 if (unlikely(buffer_write_io_error(bh)) && !result)
 358                         result = -EIO;
 359
 360                 /*
 361                  * Now in whatever state the buffer currently is, we
 362                  * know that it has been written out and so we can
 363                  * drop it from the list
 364                  */
 365                 if (__jbd2_journal_remove_checkpoint(jh))
 366                         break;
 367         }
 368 out:
 369         spin_unlock(&journal->j_list_lock);
 370         if (result < 0)
 371                 jbd2_journal_abort(journal, result);
 372         else
 373                 result = jbd2_cleanup_journal_tail(journal);
 374
 375         return (result < 0) ? result : 0;
 376 }
 377
 378 /*
 379  * Check the list of checkpoint transactions for the journal to see if
 380  * we have already got rid of any since the last update of the log tail
 381  * in the journal superblock.  If so, we can instantly roll the
 382  * superblock forward to remove those transactions from the log.
 383  *
 384  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 385  *
 386  * Called with the journal lock held.
 387  *
 388  * This is the only part of the journaling code which really needs to be
 389  * aware of transaction aborts.  Checkpointing involves writing to the
 390  * main filesystem area rather than to the journal, so it can proceed
 391  * even in abort state, but we must not update the super block if
 392  * checkpointing may have failed.  Otherwise, we would lose some metadata
 393  * buffers which should be written-back to the filesystem.
 394  */
 395
 396 int jbd2_cleanup_journal_tail(journal_t *journal)
 397 {
 398         tid_t           first_tid;
 399         unsigned long   blocknr;
 400
 401         if (is_journal_aborted(journal))
 402                 return -EIO;
 403
 404         if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
 405                 return 1;
 406         J_ASSERT(blocknr != 0);
 407
 408         /*
 409          * We need to make sure that any blocks that were recently written out
 410          * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
 411          * we drop the transactions from the journal. It's unlikely this will
 412          * be necessary, especially with an appropriately sized journal, but we
 413          * need this to guarantee correctness.  Fortunately
 414          * jbd2_cleanup_journal_tail() doesn't get called all that often.
 415          */
 416         if (journal->j_flags & JBD2_BARRIER)
 417                 blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS, NULL);
 418
 419         return __jbd2_update_log_tail(journal, first_tid, blocknr);
 420 }
 421
 422
 423 /* Checkpoint list management */
 424
 425 /*
 426  * journal_clean_one_cp_list
 427  *
 428  * Find all the written-back checkpoint buffers in the given list and
 429  * release them. If 'destroy' is set, clean all buffers unconditionally.
 430  *
 431  * Called with j_list_lock held.
 432  * Returns 1 if we freed the transaction, 0 otherwise.
 433  */
 434 static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
 435 {
 436         struct journal_head *last_jh;
 437         struct journal_head *next_jh = jh;
 438         int ret;
 439
 440         if (!jh)
 441                 return 0;
 442
 443         last_jh = jh->b_cpprev;
 444         do {
 445                 jh = next_jh;
 446                 next_jh = jh->b_cpnext;
 447                 if (!destroy)
 448                         ret = __try_to_free_cp_buf(jh);
 449                 else
 450                         ret = __jbd2_journal_remove_checkpoint(jh) + 1;
 451                 if (!ret)
 452                         return 0;
 453                 if (ret == 2)
 454                         return 1;
 455                 /*
 456                  * This function only frees up some memory
 457                  * if possible so we dont have an obligation
 458                  * to finish processing. Bail out if preemption
 459                  * requested:
 460                  */
 461                 if (need_resched())
 462                         return 0;
 463         } while (jh != last_jh);
 464
 465         return 0;
 466 }
 467
 468 /*
 469  * journal_clean_checkpoint_list
 470  *
 471  * Find all the written-back checkpoint buffers in the journal and release them.
 472  * If 'destroy' is set, release all buffers unconditionally.
 473  *
 474  * Called with j_list_lock held.
 475  */
 476 void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
 477 {
 478         transaction_t *transaction, *last_transaction, *next_transaction;
 479         int ret;
 480
 481         transaction = journal->j_checkpoint_transactions;
 482         if (!transaction)
 483                 return;
 484
 485         last_transaction = transaction->t_cpprev;
 486         next_transaction = transaction;
 487         do {
 488                 transaction = next_transaction;
 489                 next_transaction = transaction->t_cpnext;
 490                 ret = journal_clean_one_cp_list(transaction->t_checkpoint_list,
 491                                                 destroy);
 492                 /*
 493                  * This function only frees up some memory if possible so we
 494                  * dont have an obligation to finish processing. Bail out if
 495                  * preemption requested:
 496                  */
 497                 if (need_resched())
 498                         return;
 499                 if (ret)
 500                         continue;
 501                 /*
 502                  * It is essential that we are as careful as in the case of
 503                  * t_checkpoint_list with removing the buffer from the list as
 504                  * we can possibly see not yet submitted buffers on io_list
 505                  */
 506                 ret = journal_clean_one_cp_list(transaction->
 507                                 t_checkpoint_io_list, destroy);
 508                 if (need_resched())
 509                         return;
 510                 /*
 511                  * Stop scanning if we couldn't free the transaction. This
 512                  * avoids pointless scanning of transactions which still
 513                  * weren't checkpointed.
 514                  */
 515                 if (!ret)
 516                         return;
 517         } while (transaction != last_transaction);
 518 }
 519
 520 /*
 521  * Remove buffers from all checkpoint lists as journal is aborted and we just
 522  * need to free memory
 523  */
 524 void jbd2_journal_destroy_checkpoint(journal_t *journal)
 525 {
 526         /*
 527          * We loop because __jbd2_journal_clean_checkpoint_list() may abort
 528          * early due to a need of rescheduling.
 529          */
 530         while (1) {
 531                 spin_lock(&journal->j_list_lock);
 532                 if (!journal->j_checkpoint_transactions) {
 533                         spin_unlock(&journal->j_list_lock);
 534                         break;
 535                 }
 536                 __jbd2_journal_clean_checkpoint_list(journal, true);
 537                 spin_unlock(&journal->j_list_lock);
 538                 cond_resched();
 539         }
 540 }
 541
 542 /*
 543  * journal_remove_checkpoint: called after a buffer has been committed
 544  * to disk (either by being write-back flushed to disk, or being
 545  * committed to the log).
 546  *
 547  * We cannot safely clean a transaction out of the log until all of the
 548  * buffer updates committed in that transaction have safely been stored
 549  * elsewhere on disk.  To achieve this, all of the buffers in a
 550  * transaction need to be maintained on the transaction's checkpoint
 551  * lists until they have been rewritten, at which point this function is
 552  * called to remove the buffer from the existing transaction's
 553  * checkpoint lists.
 554  *
 555  * The function returns 1 if it frees the transaction, 0 otherwise.
 556  * The function can free jh and bh.
 557  *
 558  * This function is called with j_list_lock held.
 559  */
 560 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 561 {
 562         struct transaction_chp_stats_s *stats;
 563         transaction_t *transaction;
 564         journal_t *journal;
 565         int ret = 0;
 566
 567         JBUFFER_TRACE(jh, "entry");
 568
 569         if ((transaction = jh->b_cp_transaction) == NULL) {
 570                 JBUFFER_TRACE(jh, "not on transaction");
 571                 goto out;
 572         }
 573         journal = transaction->t_journal;
 574
 575         JBUFFER_TRACE(jh, "removing from transaction");
 576         __buffer_unlink(jh);
 577         jh->b_cp_transaction = NULL;
 578         jbd2_journal_put_journal_head(jh);
 579
 580         if (transaction->t_checkpoint_list != NULL ||
 581             transaction->t_checkpoint_io_list != NULL)
 582                 goto out;
 583
 584         /*
 585          * There is one special case to worry about: if we have just pulled the
 586          * buffer off a running or committing transaction's checkpoing list,
 587          * then even if the checkpoint list is empty, the transaction obviously
 588          * cannot be dropped!
 589          *
 590          * The locking here around t_state is a bit sleazy.
 591          * See the comment at the end of jbd2_journal_commit_transaction().
 592          */
 593         if (transaction->t_state != T_FINISHED)
 594                 goto out;
 595
 596         /* OK, that was the last buffer for the transaction: we can now
 597            safely remove this transaction from the log */
 598         stats = &transaction->t_chp_stats;
 599         if (stats->cs_chp_time)
 600                 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
 601                                                     jiffies);
 602         trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
 603                                     transaction->t_tid, stats);
 604
 605         __jbd2_journal_drop_transaction(journal, transaction);
 606         jbd2_journal_free_transaction(transaction);
 607         ret = 1;
 608 out:
 609         return ret;
 610 }
 611
 612 /*
 613  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 614  * list so that we know when it is safe to clean the transaction out of
 615  * the log.
 616  *
 617  * Called with the journal locked.
 618  * Called with j_list_lock held.
 619  */
 620 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
 621                                transaction_t *transaction)
 622 {
 623         JBUFFER_TRACE(jh, "entry");
 624         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 625         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 626
 627         /* Get reference for checkpointing transaction */
 628         jbd2_journal_grab_journal_head(jh2bh(jh));
 629         jh->b_cp_transaction = transaction;
 630
 631         if (!transaction->t_checkpoint_list) {
 632                 jh->b_cpnext = jh->b_cpprev = jh;
 633         } else {
 634                 jh->b_cpnext = transaction->t_checkpoint_list;
 635                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 636                 jh->b_cpprev->b_cpnext = jh;
 637                 jh->b_cpnext->b_cpprev = jh;
 638         }
 639         transaction->t_checkpoint_list = jh;
 640 }
 641
 642 /*
 643  * We've finished with this transaction structure: adios...
 644  *
 645  * The transaction must have no links except for the checkpoint by this
 646  * point.
 647  *
 648  * Called with the journal locked.
 649  * Called with j_list_lock held.
 650  */
 651
 652 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 653 {
 654         assert_spin_locked(&journal->j_list_lock);
 655         if (transaction->t_cpnext) {
 656                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 657                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 658                 if (journal->j_checkpoint_transactions == transaction)
 659                         journal->j_checkpoint_transactions =
 660                                 transaction->t_cpnext;
 661                 if (journal->j_checkpoint_transactions == transaction)
 662                         journal->j_checkpoint_transactions = NULL;
 663         }
 664
 665         J_ASSERT(transaction->t_state == T_FINISHED);
 666         J_ASSERT(transaction->t_buffers == NULL);
 667         J_ASSERT(transaction->t_forget == NULL);
 668         J_ASSERT(transaction->t_shadow_list == NULL);
 669         J_ASSERT(transaction->t_checkpoint_list == NULL);
 670         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 671         J_ASSERT(atomic_read(&transaction->t_updates) == 0);
 672         J_ASSERT(journal->j_committing_transaction != transaction);
 673         J_ASSERT(journal->j_running_transaction != transaction);
 674
 675         trace_jbd2_drop_transaction(journal, transaction);
 676
 677         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 678 }