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  * Check a checkpoint buffer could be release or not.
  62  *
  63  * Requires j_list_lock
  64  */
  65 static inline bool __cp_buffer_busy(struct journal_head *jh)
  66 {
  67         struct buffer_head *bh = jh2bh(jh);
  68
  69         return (jh->b_transaction || buffer_locked(bh) || buffer_dirty(bh));
  70 }
  71
  72 /*
  73  * __jbd2_log_wait_for_space: wait until there is space in the journal.
  74  *
  75  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
  76  * for a checkpoint to free up some space in the log.
  77  */
  78 void __jbd2_log_wait_for_space(journal_t *journal)
  79 __acquires(&journal->j_state_lock)
  80 __releases(&journal->j_state_lock)
  81 {
  82         int nblocks, space_left;
  83         /* assert_spin_locked(&journal->j_state_lock); */
  84
  85         nblocks = journal->j_max_transaction_buffers;
  86         while (jbd2_log_space_left(journal) < nblocks) {
  87                 write_unlock(&journal->j_state_lock);
  88                 mutex_lock_io(&journal->j_checkpoint_mutex);
  89
  90                 /*
  91                  * Test again, another process may have checkpointed while we
  92                  * were waiting for the checkpoint lock. If there are no
  93                  * transactions ready to be checkpointed, try to recover
  94                  * journal space by calling cleanup_journal_tail(), and if
  95                  * that doesn't work, by waiting for the currently committing
  96                  * transaction to complete.  If there is absolutely no way
  97                  * to make progress, this is either a BUG or corrupted
  98                  * filesystem, so abort the journal and leave a stack
  99                  * trace for forensic evidence.
 100                  */
 101                 write_lock(&journal->j_state_lock);
 102                 if (journal->j_flags & JBD2_ABORT) {
 103                         mutex_unlock(&journal->j_checkpoint_mutex);
 104                         return;
 105                 }
 106                 spin_lock(&journal->j_list_lock);
 107                 space_left = jbd2_log_space_left(journal);
 108                 if (space_left < nblocks) {
 109                         int chkpt = journal->j_checkpoint_transactions != NULL;
 110                         tid_t tid = 0;
 111
 112                         if (journal->j_committing_transaction)
 113                                 tid = journal->j_committing_transaction->t_tid;
 114                         spin_unlock(&journal->j_list_lock);
 115                         write_unlock(&journal->j_state_lock);
 116                         if (chkpt) {
 117                                 jbd2_log_do_checkpoint(journal);
 118                         } else if (jbd2_cleanup_journal_tail(journal) == 0) {
 119                                 /* We were able to recover space; yay! */
 120                                 ;
 121                         } else if (tid) {
 122                                 /*
 123                                  * jbd2_journal_commit_transaction() may want
 124                                  * to take the checkpoint_mutex if JBD2_FLUSHED
 125                                  * is set.  So we need to temporarily drop it.
 126                                  */
 127                                 mutex_unlock(&journal->j_checkpoint_mutex);
 128                                 jbd2_log_wait_commit(journal, tid);
 129                                 write_lock(&journal->j_state_lock);
 130                                 continue;
 131                         } else {
 132                                 printk(KERN_ERR "%s: needed %d blocks and "
 133                                        "only had %d space available\n",
 134                                        __func__, nblocks, space_left);
 135                                 printk(KERN_ERR "%s: no way to get more "
 136                                        "journal space in %s\n", __func__,
 137                                        journal->j_devname);
 138                                 WARN_ON(1);
 139                                 jbd2_journal_abort(journal, -EIO);
 140                         }
 141                         write_lock(&journal->j_state_lock);
 142                 } else {
 143                         spin_unlock(&journal->j_list_lock);
 144                 }
 145                 mutex_unlock(&journal->j_checkpoint_mutex);
 146         }
 147 }
 148
 149 static void
 150 __flush_batch(journal_t *journal, int *batch_count)
 151 {
 152         int i;
 153         struct blk_plug plug;
 154
 155         blk_start_plug(&plug);
 156         for (i = 0; i < *batch_count; i++)
 157                 write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
 158         blk_finish_plug(&plug);
 159
 160         for (i = 0; i < *batch_count; i++) {
 161                 struct buffer_head *bh = journal->j_chkpt_bhs[i];
 162                 BUFFER_TRACE(bh, "brelse");
 163                 __brelse(bh);
 164                 journal->j_chkpt_bhs[i] = NULL;
 165         }
 166         *batch_count = 0;
 167 }
 168
 169 /*
 170  * Perform an actual checkpoint. We take the first transaction on the
 171  * list of transactions to be checkpointed and send all its buffers
 172  * to disk. We submit larger chunks of data at once.
 173  *
 174  * The journal should be locked before calling this function.
 175  * Called with j_checkpoint_mutex held.
 176  */
 177 int jbd2_log_do_checkpoint(journal_t *journal)
 178 {
 179         struct journal_head     *jh;
 180         struct buffer_head      *bh;
 181         transaction_t           *transaction;
 182         tid_t                   this_tid;
 183         int                     result, batch_count = 0;
 184
 185         jbd2_debug(1, "Start checkpoint\n");
 186
 187         /*
 188          * First thing: if there are any transactions in the log which
 189          * don't need checkpointing, just eliminate them from the
 190          * journal straight away.
 191          */
 192         result = jbd2_cleanup_journal_tail(journal);
 193         trace_jbd2_checkpoint(journal, result);
 194         jbd2_debug(1, "cleanup_journal_tail returned %d\n", result);
 195         if (result <= 0)
 196                 return result;
 197
 198         /*
 199          * OK, we need to start writing disk blocks.  Take one transaction
 200          * and write it.
 201          */
 202         spin_lock(&journal->j_list_lock);
 203         if (!journal->j_checkpoint_transactions)
 204                 goto out;
 205         transaction = journal->j_checkpoint_transactions;
 206         if (transaction->t_chp_stats.cs_chp_time == 0)
 207                 transaction->t_chp_stats.cs_chp_time = jiffies;
 208         this_tid = transaction->t_tid;
 209 restart:
 210         /*
 211          * If someone cleaned up this transaction while we slept, we're
 212          * done (maybe it's a new transaction, but it fell at the same
 213          * address).
 214          */
 215         if (journal->j_checkpoint_transactions != transaction ||
 216             transaction->t_tid != this_tid)
 217                 goto out;
 218
 219         /* checkpoint all of the transaction's buffers */
 220         while (transaction->t_checkpoint_list) {
 221                 jh = transaction->t_checkpoint_list;
 222                 bh = jh2bh(jh);
 223
 224                 /*
 225                  * The buffer may be writing back, or flushing out in the
 226                  * last couple of cycles, or re-adding into a new transaction,
 227                  * need to check it again until it's unlocked.
 228                  */
 229                 if (buffer_locked(bh)) {
 230                         get_bh(bh);
 231                         spin_unlock(&journal->j_list_lock);
 232                         wait_on_buffer(bh);
 233                         /* the journal_head may have gone by now */
 234                         BUFFER_TRACE(bh, "brelse");
 235                         __brelse(bh);
 236                         goto retry;
 237                 }
 238                 if (jh->b_transaction != NULL) {
 239                         transaction_t *t = jh->b_transaction;
 240                         tid_t tid = t->t_tid;
 241
 242                         transaction->t_chp_stats.cs_forced_to_close++;
 243                         spin_unlock(&journal->j_list_lock);
 244                         if (unlikely(journal->j_flags & JBD2_UNMOUNT))
 245                                 /*
 246                                  * The journal thread is dead; so
 247                                  * starting and waiting for a commit
 248                                  * to finish will cause us to wait for
 249                                  * a _very_ long time.
 250                                  */
 251                                 printk(KERN_ERR
 252                 "JBD2: %s: Waiting for Godot: block %llu\n",
 253                 journal->j_devname, (unsigned long long) bh->b_blocknr);
 254
 255                         if (batch_count)
 256                                 __flush_batch(journal, &batch_count);
 257                         jbd2_log_start_commit(journal, tid);
 258                         /*
 259                          * jbd2_journal_commit_transaction() may want
 260                          * to take the checkpoint_mutex if JBD2_FLUSHED
 261                          * is set, jbd2_update_log_tail() called by
 262                          * jbd2_journal_commit_transaction() may also take
 263                          * checkpoint_mutex.  So we need to temporarily
 264                          * drop it.
 265                          */
 266                         mutex_unlock(&journal->j_checkpoint_mutex);
 267                         jbd2_log_wait_commit(journal, tid);
 268                         mutex_lock_io(&journal->j_checkpoint_mutex);
 269                         spin_lock(&journal->j_list_lock);
 270                         goto restart;
 271                 }
 272                 if (!buffer_dirty(bh)) {
 273                         BUFFER_TRACE(bh, "remove from checkpoint");
 274                         /*
 275                          * If the transaction was released or the checkpoint
 276                          * list was empty, we're done.
 277                          */
 278                         if (__jbd2_journal_remove_checkpoint(jh) ||
 279                             !transaction->t_checkpoint_list)
 280                                 goto out;
 281                 } else {
 282                         /*
 283                          * We are about to write the buffer, it could be
 284                          * raced by some other transaction shrink or buffer
 285                          * re-log logic once we release the j_list_lock,
 286                          * leave it on the checkpoint list and check status
 287                          * again to make sure it's clean.
 288                          */
 289                         BUFFER_TRACE(bh, "queue");
 290                         get_bh(bh);
 291                         J_ASSERT_BH(bh, !buffer_jwrite(bh));
 292                         journal->j_chkpt_bhs[batch_count++] = bh;
 293                         transaction->t_chp_stats.cs_written++;
 294                         transaction->t_checkpoint_list = jh->b_cpnext;
 295                 }
 296
 297                 if ((batch_count == JBD2_NR_BATCH) ||
 298                     need_resched() || spin_needbreak(&journal->j_list_lock) ||
 299                     jh2bh(transaction->t_checkpoint_list) == journal->j_chkpt_bhs[0])
 300                         goto unlock_and_flush;
 301         }
 302
 303         if (batch_count) {
 304                 unlock_and_flush:
 305                         spin_unlock(&journal->j_list_lock);
 306                 retry:
 307                         if (batch_count)
 308                                 __flush_batch(journal, &batch_count);
 309                         spin_lock(&journal->j_list_lock);
 310                         goto restart;
 311         }
 312
 313 out:
 314         spin_unlock(&journal->j_list_lock);
 315         result = jbd2_cleanup_journal_tail(journal);
 316
 317         return (result < 0) ? result : 0;
 318 }
 319
 320 /*
 321  * Check the list of checkpoint transactions for the journal to see if
 322  * we have already got rid of any since the last update of the log tail
 323  * in the journal superblock.  If so, we can instantly roll the
 324  * superblock forward to remove those transactions from the log.
 325  *
 326  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 327  *
 328  * Called with the journal lock held.
 329  *
 330  * This is the only part of the journaling code which really needs to be
 331  * aware of transaction aborts.  Checkpointing involves writing to the
 332  * main filesystem area rather than to the journal, so it can proceed
 333  * even in abort state, but we must not update the super block if
 334  * checkpointing may have failed.  Otherwise, we would lose some metadata
 335  * buffers which should be written-back to the filesystem.
 336  */
 337
 338 int jbd2_cleanup_journal_tail(journal_t *journal)
 339 {
 340         tid_t           first_tid;
 341         unsigned long   blocknr;
 342
 343         if (is_journal_aborted(journal))
 344                 return -EIO;
 345
 346         if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
 347                 return 1;
 348         J_ASSERT(blocknr != 0);
 349
 350         /*
 351          * We need to make sure that any blocks that were recently written out
 352          * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
 353          * we drop the transactions from the journal. It's unlikely this will
 354          * be necessary, especially with an appropriately sized journal, but we
 355          * need this to guarantee correctness.  Fortunately
 356          * jbd2_cleanup_journal_tail() doesn't get called all that often.
 357          */
 358         if (journal->j_flags & JBD2_BARRIER)
 359                 blkdev_issue_flush(journal->j_fs_dev);
 360
 361         return __jbd2_update_log_tail(journal, first_tid, blocknr);
 362 }
 363
 364
 365 /* Checkpoint list management */
 366
 367 /*
 368  * journal_clean_one_cp_list
 369  *
 370  * Find all the written-back checkpoint buffers in the given list and
 371  * release them. If 'destroy' is set, clean all buffers unconditionally.
 372  *
 373  * Called with j_list_lock held.
 374  * Returns 1 if we freed the transaction, 0 otherwise.
 375  */
 376 static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
 377 {
 378         struct journal_head *last_jh;
 379         struct journal_head *next_jh = jh;
 380
 381         if (!jh)
 382                 return 0;
 383
 384         last_jh = jh->b_cpprev;
 385         do {
 386                 jh = next_jh;
 387                 next_jh = jh->b_cpnext;
 388
 389                 if (!destroy && __cp_buffer_busy(jh))
 390                         return 0;
 391
 392                 if (__jbd2_journal_remove_checkpoint(jh))
 393                         return 1;
 394                 /*
 395                  * This function only frees up some memory
 396                  * if possible so we dont have an obligation
 397                  * to finish processing. Bail out if preemption
 398                  * requested:
 399                  */
 400                 if (need_resched())
 401                         return 0;
 402         } while (jh != last_jh);
 403
 404         return 0;
 405 }
 406
 407 /*
 408  * journal_shrink_one_cp_list
 409  *
 410  * Find 'nr_to_scan' written-back checkpoint buffers in the given list
 411  * and try to release them. If the whole transaction is released, set
 412  * the 'released' parameter. Return the number of released checkpointed
 413  * buffers.
 414  *
 415  * Called with j_list_lock held.
 416  */
 417 static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
 418                                                 unsigned long *nr_to_scan,
 419                                                 bool *released)
 420 {
 421         struct journal_head *last_jh;
 422         struct journal_head *next_jh = jh;
 423         unsigned long nr_freed = 0;
 424         int ret;
 425
 426         if (!jh || *nr_to_scan == 0)
 427                 return 0;
 428
 429         last_jh = jh->b_cpprev;
 430         do {
 431                 jh = next_jh;
 432                 next_jh = jh->b_cpnext;
 433
 434                 (*nr_to_scan)--;
 435                 if (__cp_buffer_busy(jh))
 436                         continue;
 437
 438                 nr_freed++;
 439                 ret = __jbd2_journal_remove_checkpoint(jh);
 440                 if (ret) {
 441                         *released = true;
 442                         break;
 443                 }
 444
 445                 if (need_resched())
 446                         break;
 447         } while (jh != last_jh && *nr_to_scan);
 448
 449         return nr_freed;
 450 }
 451
 452 /*
 453  * jbd2_journal_shrink_checkpoint_list
 454  *
 455  * Find 'nr_to_scan' written-back checkpoint buffers in the journal
 456  * and try to release them. Return the number of released checkpointed
 457  * buffers.
 458  *
 459  * Called with j_list_lock held.
 460  */
 461 unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
 462                                                   unsigned long *nr_to_scan)
 463 {
 464         transaction_t *transaction, *last_transaction, *next_transaction;
 465         bool released;
 466         tid_t first_tid = 0, last_tid = 0, next_tid = 0;
 467         tid_t tid = 0;
 468         unsigned long nr_freed = 0;
 469         unsigned long nr_scanned = *nr_to_scan;
 470
 471 again:
 472         spin_lock(&journal->j_list_lock);
 473         if (!journal->j_checkpoint_transactions) {
 474                 spin_unlock(&journal->j_list_lock);
 475                 goto out;
 476         }
 477
 478         /*
 479          * Get next shrink transaction, resume previous scan or start
 480          * over again. If some others do checkpoint and drop transaction
 481          * from the checkpoint list, we ignore saved j_shrink_transaction
 482          * and start over unconditionally.
 483          */
 484         if (journal->j_shrink_transaction)
 485                 transaction = journal->j_shrink_transaction;
 486         else
 487                 transaction = journal->j_checkpoint_transactions;
 488
 489         if (!first_tid)
 490                 first_tid = transaction->t_tid;
 491         last_transaction = journal->j_checkpoint_transactions->t_cpprev;
 492         next_transaction = transaction;
 493         last_tid = last_transaction->t_tid;
 494         do {
 495                 transaction = next_transaction;
 496                 next_transaction = transaction->t_cpnext;
 497                 tid = transaction->t_tid;
 498                 released = false;
 499
 500                 nr_freed += journal_shrink_one_cp_list(transaction->t_checkpoint_list,
 501                                                        nr_to_scan, &released);
 502                 if (*nr_to_scan == 0)
 503                         break;
 504                 if (need_resched() || spin_needbreak(&journal->j_list_lock))
 505                         break;
 506                 if (released)
 507                         continue;
 508
 509                 nr_freed += journal_shrink_one_cp_list(transaction->t_checkpoint_io_list,
 510                                                        nr_to_scan, &released);
 511                 if (*nr_to_scan == 0)
 512                         break;
 513                 if (need_resched() || spin_needbreak(&journal->j_list_lock))
 514                         break;
 515         } while (transaction != last_transaction);
 516
 517         if (transaction != last_transaction) {
 518                 journal->j_shrink_transaction = next_transaction;
 519                 next_tid = next_transaction->t_tid;
 520         } else {
 521                 journal->j_shrink_transaction = NULL;
 522                 next_tid = 0;
 523         }
 524
 525         spin_unlock(&journal->j_list_lock);
 526         cond_resched();
 527
 528         if (*nr_to_scan && next_tid)
 529                 goto again;
 530 out:
 531         nr_scanned -= *nr_to_scan;
 532         trace_jbd2_shrink_checkpoint_list(journal, first_tid, tid, last_tid,
 533                                           nr_freed, nr_scanned, next_tid);
 534
 535         return nr_freed;
 536 }
 537
 538 /*
 539  * journal_clean_checkpoint_list
 540  *
 541  * Find all the written-back checkpoint buffers in the journal and release them.
 542  * If 'destroy' is set, release all buffers unconditionally.
 543  *
 544  * Called with j_list_lock held.
 545  */
 546 void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
 547 {
 548         transaction_t *transaction, *last_transaction, *next_transaction;
 549         int ret;
 550
 551         transaction = journal->j_checkpoint_transactions;
 552         if (!transaction)
 553                 return;
 554
 555         last_transaction = transaction->t_cpprev;
 556         next_transaction = transaction;
 557         do {
 558                 transaction = next_transaction;
 559                 next_transaction = transaction->t_cpnext;
 560                 ret = journal_clean_one_cp_list(transaction->t_checkpoint_list,
 561                                                 destroy);
 562                 /*
 563                  * This function only frees up some memory if possible so we
 564                  * dont have an obligation to finish processing. Bail out if
 565                  * preemption requested:
 566                  */
 567                 if (need_resched())
 568                         return;
 569                 if (ret)
 570                         continue;
 571                 /*
 572                  * It is essential that we are as careful as in the case of
 573                  * t_checkpoint_list with removing the buffer from the list as
 574                  * we can possibly see not yet submitted buffers on io_list
 575                  */
 576                 ret = journal_clean_one_cp_list(transaction->
 577                                 t_checkpoint_io_list, destroy);
 578                 if (need_resched())
 579                         return;
 580                 /*
 581                  * Stop scanning if we couldn't free the transaction. This
 582                  * avoids pointless scanning of transactions which still
 583                  * weren't checkpointed.
 584                  */
 585                 if (!ret)
 586                         return;
 587         } while (transaction != last_transaction);
 588 }
 589
 590 /*
 591  * Remove buffers from all checkpoint lists as journal is aborted and we just
 592  * need to free memory
 593  */
 594 void jbd2_journal_destroy_checkpoint(journal_t *journal)
 595 {
 596         /*
 597          * We loop because __jbd2_journal_clean_checkpoint_list() may abort
 598          * early due to a need of rescheduling.
 599          */
 600         while (1) {
 601                 spin_lock(&journal->j_list_lock);
 602                 if (!journal->j_checkpoint_transactions) {
 603                         spin_unlock(&journal->j_list_lock);
 604                         break;
 605                 }
 606                 __jbd2_journal_clean_checkpoint_list(journal, true);
 607                 spin_unlock(&journal->j_list_lock);
 608                 cond_resched();
 609         }
 610 }
 611
 612 /*
 613  * journal_remove_checkpoint: called after a buffer has been committed
 614  * to disk (either by being write-back flushed to disk, or being
 615  * committed to the log).
 616  *
 617  * We cannot safely clean a transaction out of the log until all of the
 618  * buffer updates committed in that transaction have safely been stored
 619  * elsewhere on disk.  To achieve this, all of the buffers in a
 620  * transaction need to be maintained on the transaction's checkpoint
 621  * lists until they have been rewritten, at which point this function is
 622  * called to remove the buffer from the existing transaction's
 623  * checkpoint lists.
 624  *
 625  * The function returns 1 if it frees the transaction, 0 otherwise.
 626  * The function can free jh and bh.
 627  *
 628  * This function is called with j_list_lock held.
 629  */
 630 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 631 {
 632         struct transaction_chp_stats_s *stats;
 633         transaction_t *transaction;
 634         journal_t *journal;
 635         struct buffer_head *bh = jh2bh(jh);
 636
 637         JBUFFER_TRACE(jh, "entry");
 638
 639         transaction = jh->b_cp_transaction;
 640         if (!transaction) {
 641                 JBUFFER_TRACE(jh, "not on transaction");
 642                 return 0;
 643         }
 644         journal = transaction->t_journal;
 645
 646         JBUFFER_TRACE(jh, "removing from transaction");
 647
 648         /*
 649          * If we have failed to write the buffer out to disk, the filesystem
 650          * may become inconsistent. We cannot abort the journal here since
 651          * we hold j_list_lock and we have to be careful about races with
 652          * jbd2_journal_destroy(). So mark the writeback IO error in the
 653          * journal here and we abort the journal later from a better context.
 654          */
 655         if (buffer_write_io_error(bh))
 656                 set_bit(JBD2_CHECKPOINT_IO_ERROR, &journal->j_atomic_flags);
 657
 658         __buffer_unlink(jh);
 659         jh->b_cp_transaction = NULL;
 660         percpu_counter_dec(&journal->j_checkpoint_jh_count);
 661         jbd2_journal_put_journal_head(jh);
 662
 663         /* Is this transaction empty? */
 664         if (transaction->t_checkpoint_list || transaction->t_checkpoint_io_list)
 665                 return 0;
 666
 667         /*
 668          * There is one special case to worry about: if we have just pulled the
 669          * buffer off a running or committing transaction's checkpoing list,
 670          * then even if the checkpoint list is empty, the transaction obviously
 671          * cannot be dropped!
 672          *
 673          * The locking here around t_state is a bit sleazy.
 674          * See the comment at the end of jbd2_journal_commit_transaction().
 675          */
 676         if (transaction->t_state != T_FINISHED)
 677                 return 0;
 678
 679         /*
 680          * OK, that was the last buffer for the transaction, we can now
 681          * safely remove this transaction from the log.
 682          */
 683         stats = &transaction->t_chp_stats;
 684         if (stats->cs_chp_time)
 685                 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
 686                                                     jiffies);
 687         trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
 688                                     transaction->t_tid, stats);
 689
 690         __jbd2_journal_drop_transaction(journal, transaction);
 691         jbd2_journal_free_transaction(transaction);
 692         return 1;
 693 }
 694
 695 /*
 696  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 697  * list so that we know when it is safe to clean the transaction out of
 698  * the log.
 699  *
 700  * Called with the journal locked.
 701  * Called with j_list_lock held.
 702  */
 703 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
 704                                transaction_t *transaction)
 705 {
 706         JBUFFER_TRACE(jh, "entry");
 707         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 708         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 709
 710         /* Get reference for checkpointing transaction */
 711         jbd2_journal_grab_journal_head(jh2bh(jh));
 712         jh->b_cp_transaction = transaction;
 713
 714         if (!transaction->t_checkpoint_list) {
 715                 jh->b_cpnext = jh->b_cpprev = jh;
 716         } else {
 717                 jh->b_cpnext = transaction->t_checkpoint_list;
 718                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 719                 jh->b_cpprev->b_cpnext = jh;
 720                 jh->b_cpnext->b_cpprev = jh;
 721         }
 722         transaction->t_checkpoint_list = jh;
 723         percpu_counter_inc(&transaction->t_journal->j_checkpoint_jh_count);
 724 }
 725
 726 /*
 727  * We've finished with this transaction structure: adios...
 728  *
 729  * The transaction must have no links except for the checkpoint by this
 730  * point.
 731  *
 732  * Called with the journal locked.
 733  * Called with j_list_lock held.
 734  */
 735
 736 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 737 {
 738         assert_spin_locked(&journal->j_list_lock);
 739
 740         journal->j_shrink_transaction = NULL;
 741         if (transaction->t_cpnext) {
 742                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 743                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 744                 if (journal->j_checkpoint_transactions == transaction)
 745                         journal->j_checkpoint_transactions =
 746                                 transaction->t_cpnext;
 747                 if (journal->j_checkpoint_transactions == transaction)
 748                         journal->j_checkpoint_transactions = NULL;
 749         }
 750
 751         J_ASSERT(transaction->t_state == T_FINISHED);
 752         J_ASSERT(transaction->t_buffers == NULL);
 753         J_ASSERT(transaction->t_forget == NULL);
 754         J_ASSERT(transaction->t_shadow_list == NULL);
 755         J_ASSERT(transaction->t_checkpoint_list == NULL);
 756         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 757         J_ASSERT(atomic_read(&transaction->t_updates) == 0);
 758         J_ASSERT(journal->j_committing_transaction != transaction);
 759         J_ASSERT(journal->j_running_transaction != transaction);
 760
 761         trace_jbd2_drop_transaction(journal, transaction);
 762
 763         jbd2_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 764 }