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  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  92  */
  93 static int __try_to_free_cp_buf(struct journal_head *jh)
  94 {
  95         int ret = 0;
  96         struct buffer_head *bh = jh2bh(jh);
  97
  98         if (jh->b_jlist == BJ_None && !buffer_locked(bh) &&
  99             !buffer_dirty(bh) && !buffer_write_io_error(bh)) {
 100                 JBUFFER_TRACE(jh, "remove from checkpoint list");
 101                 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
 102                 jbd_unlock_bh_state(bh);
 103                 jbd2_journal_remove_journal_head(bh);
 104                 BUFFER_TRACE(bh, "release");
 105                 __brelse(bh);
 106         } else {
 107                 jbd_unlock_bh_state(bh);
 108         }
 109         return ret;
 110 }
 111
 112 /*
 113  * __jbd2_log_wait_for_space: wait until there is space in the journal.
 114  *
 115  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
 116  * for a checkpoint to free up some space in the log.
 117  */
 118 void __jbd2_log_wait_for_space(journal_t *journal)
 119 {
 120         int nblocks, space_left;
 121         assert_spin_locked(&journal->j_state_lock);
 122
 123         nblocks = jbd_space_needed(journal);
 124         while (__jbd2_log_space_left(journal) < nblocks) {
 125                 if (journal->j_flags & JBD2_ABORT)
 126                         return;
 127                 spin_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                 spin_lock(&journal->j_state_lock);
 142                 spin_lock(&journal->j_list_lock);
 143                 nblocks = jbd_space_needed(journal);
 144                 space_left = __jbd2_log_space_left(journal);
 145                 if (space_left < nblocks) {
 146                         int chkpt = journal->j_checkpoint_transactions != NULL;
 147                         tid_t tid = 0;
 148
 149                         if (journal->j_committing_transaction)
 150                                 tid = journal->j_committing_transaction->t_tid;
 151                         spin_unlock(&journal->j_list_lock);
 152                         spin_unlock(&journal->j_state_lock);
 153                         if (chkpt) {
 154                                 jbd2_log_do_checkpoint(journal);
 155                         } else if (jbd2_cleanup_journal_tail(journal) == 0) {
 156                                 /* We were able to recover space; yay! */
 157                                 ;
 158                         } else if (tid) {
 159                                 jbd2_log_wait_commit(journal, tid);
 160                         } else {
 161                                 printk(KERN_ERR "%s: needed %d blocks and "
 162                                        "only had %d space available\n",
 163                                        __func__, nblocks, space_left);
 164                                 printk(KERN_ERR "%s: no way to get more "
 165                                        "journal space in %s\n", __func__,
 166                                        journal->j_devname);
 167                                 WARN_ON(1);
 168                                 jbd2_journal_abort(journal, 0);
 169                         }
 170                         spin_lock(&journal->j_state_lock);
 171                 } else {
 172                         spin_unlock(&journal->j_list_lock);
 173                 }
 174                 mutex_unlock(&journal->j_checkpoint_mutex);
 175         }
 176 }
 177
 178 /*
 179  * We were unable to perform jbd_trylock_bh_state() inside j_list_lock.
 180  * The caller must restart a list walk.  Wait for someone else to run
 181  * jbd_unlock_bh_state().
 182  */
 183 static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
 184         __releases(journal->j_list_lock)
 185 {
 186         get_bh(bh);
 187         spin_unlock(&journal->j_list_lock);
 188         jbd_lock_bh_state(bh);
 189         jbd_unlock_bh_state(bh);
 190         put_bh(bh);
 191 }
 192
 193 /*
 194  * Clean up transaction's list of buffers submitted for io.
 195  * We wait for any pending IO to complete and remove any clean
 196  * buffers. Note that we take the buffers in the opposite ordering
 197  * from the one in which they were submitted for IO.
 198  *
 199  * Return 0 on success, and return <0 if some buffers have failed
 200  * to be written out.
 201  *
 202  * Called with j_list_lock held.
 203  */
 204 static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
 205 {
 206         struct journal_head *jh;
 207         struct buffer_head *bh;
 208         tid_t this_tid;
 209         int released = 0;
 210         int ret = 0;
 211
 212         this_tid = transaction->t_tid;
 213 restart:
 214         /* Did somebody clean up the transaction in the meanwhile? */
 215         if (journal->j_checkpoint_transactions != transaction ||
 216                         transaction->t_tid != this_tid)
 217                 return ret;
 218         while (!released && transaction->t_checkpoint_io_list) {
 219                 jh = transaction->t_checkpoint_io_list;
 220                 bh = jh2bh(jh);
 221                 if (!jbd_trylock_bh_state(bh)) {
 222                         jbd_sync_bh(journal, bh);
 223                         spin_lock(&journal->j_list_lock);
 224                         goto restart;
 225                 }
 226                 if (buffer_locked(bh)) {
 227                         atomic_inc(&bh->b_count);
 228                         spin_unlock(&journal->j_list_lock);
 229                         jbd_unlock_bh_state(bh);
 230                         wait_on_buffer(bh);
 231                         /* the journal_head may have gone by now */
 232                         BUFFER_TRACE(bh, "brelse");
 233                         __brelse(bh);
 234                         spin_lock(&journal->j_list_lock);
 235                         goto restart;
 236                 }
 237                 if (unlikely(buffer_write_io_error(bh)))
 238                         ret = -EIO;
 239
 240                 /*
 241                  * Now in whatever state the buffer currently is, we know that
 242                  * it has been written out and so we can drop it from the list
 243                  */
 244                 released = __jbd2_journal_remove_checkpoint(jh);
 245                 jbd_unlock_bh_state(bh);
 246                 jbd2_journal_remove_journal_head(bh);
 247                 __brelse(bh);
 248         }
 249
 250         return ret;
 251 }
 252
 253 static void
 254 __flush_batch(journal_t *journal, int *batch_count)
 255 {
 256         int i;
 257
 258         ll_rw_block(SWRITE, *batch_count, journal->j_chkpt_bhs);
 259         for (i = 0; i < *batch_count; i++) {
 260                 struct buffer_head *bh = journal->j_chkpt_bhs[i];
 261                 clear_buffer_jwrite(bh);
 262                 BUFFER_TRACE(bh, "brelse");
 263                 __brelse(bh);
 264         }
 265         *batch_count = 0;
 266 }
 267
 268 /*
 269  * Try to flush one buffer from the checkpoint list to disk.
 270  *
 271  * Return 1 if something happened which requires us to abort the current
 272  * scan of the checkpoint list.  Return <0 if the buffer has failed to
 273  * be written out.
 274  *
 275  * Called with j_list_lock held and drops it if 1 is returned
 276  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
 277  */
 278 static int __process_buffer(journal_t *journal, struct journal_head *jh,
 279                             int *batch_count, transaction_t *transaction)
 280 {
 281         struct buffer_head *bh = jh2bh(jh);
 282         int ret = 0;
 283
 284         if (buffer_locked(bh)) {
 285                 atomic_inc(&bh->b_count);
 286                 spin_unlock(&journal->j_list_lock);
 287                 jbd_unlock_bh_state(bh);
 288                 wait_on_buffer(bh);
 289                 /* the journal_head may have gone by now */
 290                 BUFFER_TRACE(bh, "brelse");
 291                 __brelse(bh);
 292                 ret = 1;
 293         } else if (jh->b_transaction != NULL) {
 294                 transaction_t *t = jh->b_transaction;
 295                 tid_t tid = t->t_tid;
 296
 297                 transaction->t_chp_stats.cs_forced_to_close++;
 298                 spin_unlock(&journal->j_list_lock);
 299                 jbd_unlock_bh_state(bh);
 300                 jbd2_log_start_commit(journal, tid);
 301                 jbd2_log_wait_commit(journal, tid);
 302                 ret = 1;
 303         } else if (!buffer_dirty(bh)) {
 304                 ret = 1;
 305                 if (unlikely(buffer_write_io_error(bh)))
 306                         ret = -EIO;
 307                 J_ASSERT_JH(jh, !buffer_jbddirty(bh));
 308                 BUFFER_TRACE(bh, "remove from checkpoint");
 309                 __jbd2_journal_remove_checkpoint(jh);
 310                 spin_unlock(&journal->j_list_lock);
 311                 jbd_unlock_bh_state(bh);
 312                 jbd2_journal_remove_journal_head(bh);
 313                 __brelse(bh);
 314         } else {
 315                 /*
 316                  * Important: we are about to write the buffer, and
 317                  * possibly block, while still holding the journal lock.
 318                  * We cannot afford to let the transaction logic start
 319                  * messing around with this buffer before we write it to
 320                  * disk, as that would break recoverability.
 321                  */
 322                 BUFFER_TRACE(bh, "queue");
 323                 get_bh(bh);
 324                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 325                 set_buffer_jwrite(bh);
 326                 journal->j_chkpt_bhs[*batch_count] = bh;
 327                 __buffer_relink_io(jh);
 328                 jbd_unlock_bh_state(bh);
 329                 transaction->t_chp_stats.cs_written++;
 330                 (*batch_count)++;
 331                 if (*batch_count == JBD2_NR_BATCH) {
 332                         spin_unlock(&journal->j_list_lock);
 333                         __flush_batch(journal, batch_count);
 334                         ret = 1;
 335                 }
 336         }
 337         return ret;
 338 }
 339
 340 /*
 341  * Perform an actual checkpoint. We take the first transaction on the
 342  * list of transactions to be checkpointed and send all its buffers
 343  * to disk. We submit larger chunks of data at once.
 344  *
 345  * The journal should be locked before calling this function.
 346  * Called with j_checkpoint_mutex held.
 347  */
 348 int jbd2_log_do_checkpoint(journal_t *journal)
 349 {
 350         transaction_t *transaction;
 351         tid_t this_tid;
 352         int result;
 353
 354         jbd_debug(1, "Start checkpoint\n");
 355
 356         /*
 357          * First thing: if there are any transactions in the log which
 358          * don't need checkpointing, just eliminate them from the
 359          * journal straight away.
 360          */
 361         result = jbd2_cleanup_journal_tail(journal);
 362         trace_jbd2_checkpoint(journal, result);
 363         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 364         if (result <= 0)
 365                 return result;
 366
 367         /*
 368          * OK, we need to start writing disk blocks.  Take one transaction
 369          * and write it.
 370          */
 371         result = 0;
 372         spin_lock(&journal->j_list_lock);
 373         if (!journal->j_checkpoint_transactions)
 374                 goto out;
 375         transaction = journal->j_checkpoint_transactions;
 376         if (transaction->t_chp_stats.cs_chp_time == 0)
 377                 transaction->t_chp_stats.cs_chp_time = jiffies;
 378         this_tid = transaction->t_tid;
 379 restart:
 380         /*
 381          * If someone cleaned up this transaction while we slept, we're
 382          * done (maybe it's a new transaction, but it fell at the same
 383          * address).
 384          */
 385         if (journal->j_checkpoint_transactions == transaction &&
 386                         transaction->t_tid == this_tid) {
 387                 int batch_count = 0;
 388                 struct journal_head *jh;
 389                 int retry = 0, err;
 390
 391                 while (!retry && transaction->t_checkpoint_list) {
 392                         struct buffer_head *bh;
 393
 394                         jh = transaction->t_checkpoint_list;
 395                         bh = jh2bh(jh);
 396                         if (!jbd_trylock_bh_state(bh)) {
 397                                 jbd_sync_bh(journal, bh);
 398                                 retry = 1;
 399                                 break;
 400                         }
 401                         retry = __process_buffer(journal, jh, &batch_count,
 402                                                  transaction);
 403                         if (retry < 0 && !result)
 404                                 result = retry;
 405                         if (!retry && (need_resched() ||
 406                                 spin_needbreak(&journal->j_list_lock))) {
 407                                 spin_unlock(&journal->j_list_lock);
 408                                 retry = 1;
 409                                 break;
 410                         }
 411                 }
 412
 413                 if (batch_count) {
 414                         if (!retry) {
 415                                 spin_unlock(&journal->j_list_lock);
 416                                 retry = 1;
 417                         }
 418                         __flush_batch(journal, &batch_count);
 419                 }
 420
 421                 if (retry) {
 422                         spin_lock(&journal->j_list_lock);
 423                         goto restart;
 424                 }
 425                 /*
 426                  * Now we have cleaned up the first transaction's checkpoint
 427                  * list. Let's clean up the second one
 428                  */
 429                 err = __wait_cp_io(journal, transaction);
 430                 if (!result)
 431                         result = err;
 432         }
 433 out:
 434         spin_unlock(&journal->j_list_lock);
 435         if (result < 0)
 436                 jbd2_journal_abort(journal, result);
 437         else
 438                 result = jbd2_cleanup_journal_tail(journal);
 439
 440         return (result < 0) ? result : 0;
 441 }
 442
 443 /*
 444  * Check the list of checkpoint transactions for the journal to see if
 445  * we have already got rid of any since the last update of the log tail
 446  * in the journal superblock.  If so, we can instantly roll the
 447  * superblock forward to remove those transactions from the log.
 448  *
 449  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 450  *
 451  * Called with the journal lock held.
 452  *
 453  * This is the only part of the journaling code which really needs to be
 454  * aware of transaction aborts.  Checkpointing involves writing to the
 455  * main filesystem area rather than to the journal, so it can proceed
 456  * even in abort state, but we must not update the super block if
 457  * checkpointing may have failed.  Otherwise, we would lose some metadata
 458  * buffers which should be written-back to the filesystem.
 459  */
 460
 461 int jbd2_cleanup_journal_tail(journal_t *journal)
 462 {
 463         transaction_t * transaction;
 464         tid_t           first_tid;
 465         unsigned long   blocknr, freed;
 466
 467         if (is_journal_aborted(journal))
 468                 return 1;
 469
 470         /* OK, work out the oldest transaction remaining in the log, and
 471          * the log block it starts at.
 472          *
 473          * If the log is now empty, we need to work out which is the
 474          * next transaction ID we will write, and where it will
 475          * start. */
 476
 477         spin_lock(&journal->j_state_lock);
 478         spin_lock(&journal->j_list_lock);
 479         transaction = journal->j_checkpoint_transactions;
 480         if (transaction) {
 481                 first_tid = transaction->t_tid;
 482                 blocknr = transaction->t_log_start;
 483         } else if ((transaction = journal->j_committing_transaction) != NULL) {
 484                 first_tid = transaction->t_tid;
 485                 blocknr = transaction->t_log_start;
 486         } else if ((transaction = journal->j_running_transaction) != NULL) {
 487                 first_tid = transaction->t_tid;
 488                 blocknr = journal->j_head;
 489         } else {
 490                 first_tid = journal->j_transaction_sequence;
 491                 blocknr = journal->j_head;
 492         }
 493         spin_unlock(&journal->j_list_lock);
 494         J_ASSERT(blocknr != 0);
 495
 496         /* If the oldest pinned transaction is at the tail of the log
 497            already then there's not much we can do right now. */
 498         if (journal->j_tail_sequence == first_tid) {
 499                 spin_unlock(&journal->j_state_lock);
 500                 return 1;
 501         }
 502
 503         /* OK, update the superblock to recover the freed space.
 504          * Physical blocks come first: have we wrapped beyond the end of
 505          * the log?  */
 506         freed = blocknr - journal->j_tail;
 507         if (blocknr < journal->j_tail)
 508                 freed = freed + journal->j_last - journal->j_first;
 509
 510         jbd_debug(1,
 511                   "Cleaning journal tail from %d to %d (offset %lu), "
 512                   "freeing %lu\n",
 513                   journal->j_tail_sequence, first_tid, blocknr, freed);
 514
 515         journal->j_free += freed;
 516         journal->j_tail_sequence = first_tid;
 517         journal->j_tail = blocknr;
 518         spin_unlock(&journal->j_state_lock);
 519
 520         /*
 521          * If there is an external journal, we need to make sure that
 522          * any data blocks that were recently written out --- perhaps
 523          * by jbd2_log_do_checkpoint() --- are flushed out before we
 524          * drop the transactions from the external journal.  It's
 525          * unlikely this will be necessary, especially with a
 526          * appropriately sized journal, but we need this to guarantee
 527          * correctness.  Fortunately jbd2_cleanup_journal_tail()
 528          * doesn't get called all that often.
 529          */
 530         if ((journal->j_fs_dev != journal->j_dev) &&
 531             (journal->j_flags & JBD2_BARRIER))
 532                 blkdev_issue_flush(journal->j_fs_dev, NULL);
 533         if (!(journal->j_flags & JBD2_ABORT))
 534                 jbd2_journal_update_superblock(journal, 1);
 535         return 0;
 536 }
 537
 538
 539 /* Checkpoint list management */
 540
 541 /*
 542  * journal_clean_one_cp_list
 543  *
 544  * Find all the written-back checkpoint buffers in the given list and release them.
 545  *
 546  * Called with the journal locked.
 547  * Called with j_list_lock held.
 548  * Returns number of bufers reaped (for debug)
 549  */
 550
 551 static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
 552 {
 553         struct journal_head *last_jh;
 554         struct journal_head *next_jh = jh;
 555         int ret, freed = 0;
 556
 557         *released = 0;
 558         if (!jh)
 559                 return 0;
 560
 561         last_jh = jh->b_cpprev;
 562         do {
 563                 jh = next_jh;
 564                 next_jh = jh->b_cpnext;
 565                 /* Use trylock because of the ranking */
 566                 if (jbd_trylock_bh_state(jh2bh(jh))) {
 567                         ret = __try_to_free_cp_buf(jh);
 568                         if (ret) {
 569                                 freed++;
 570                                 if (ret == 2) {
 571                                         *released = 1;
 572                                         return freed;
 573                                 }
 574                         }
 575                 }
 576                 /*
 577                  * This function only frees up some memory
 578                  * if possible so we dont have an obligation
 579                  * to finish processing. Bail out if preemption
 580                  * requested:
 581                  */
 582                 if (need_resched())
 583                         return freed;
 584         } while (jh != last_jh);
 585
 586         return freed;
 587 }
 588
 589 /*
 590  * journal_clean_checkpoint_list
 591  *
 592  * Find all the written-back checkpoint buffers in the journal and release them.
 593  *
 594  * Called with the journal locked.
 595  * Called with j_list_lock held.
 596  * Returns number of buffers reaped (for debug)
 597  */
 598
 599 int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
 600 {
 601         transaction_t *transaction, *last_transaction, *next_transaction;
 602         int ret = 0;
 603         int released;
 604
 605         transaction = journal->j_checkpoint_transactions;
 606         if (!transaction)
 607                 goto out;
 608
 609         last_transaction = transaction->t_cpprev;
 610         next_transaction = transaction;
 611         do {
 612                 transaction = next_transaction;
 613                 next_transaction = transaction->t_cpnext;
 614                 ret += journal_clean_one_cp_list(transaction->
 615                                 t_checkpoint_list, &released);
 616                 /*
 617                  * This function only frees up some memory if possible so we
 618                  * dont have an obligation to finish processing. Bail out if
 619                  * preemption requested:
 620                  */
 621                 if (need_resched())
 622                         goto out;
 623                 if (released)
 624                         continue;
 625                 /*
 626                  * It is essential that we are as careful as in the case of
 627                  * t_checkpoint_list with removing the buffer from the list as
 628                  * we can possibly see not yet submitted buffers on io_list
 629                  */
 630                 ret += journal_clean_one_cp_list(transaction->
 631                                 t_checkpoint_io_list, &released);
 632                 if (need_resched())
 633                         goto out;
 634         } while (transaction != last_transaction);
 635 out:
 636         return ret;
 637 }
 638
 639 /*
 640  * journal_remove_checkpoint: called after a buffer has been committed
 641  * to disk (either by being write-back flushed to disk, or being
 642  * committed to the log).
 643  *
 644  * We cannot safely clean a transaction out of the log until all of the
 645  * buffer updates committed in that transaction have safely been stored
 646  * elsewhere on disk.  To achieve this, all of the buffers in a
 647  * transaction need to be maintained on the transaction's checkpoint
 648  * lists until they have been rewritten, at which point this function is
 649  * called to remove the buffer from the existing transaction's
 650  * checkpoint lists.
 651  *
 652  * The function returns 1 if it frees the transaction, 0 otherwise.
 653  *
 654  * This function is called with the journal locked.
 655  * This function is called with j_list_lock held.
 656  * This function is called with jbd_lock_bh_state(jh2bh(jh))
 657  */
 658
 659 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 660 {
 661         struct transaction_chp_stats_s *stats;
 662         transaction_t *transaction;
 663         journal_t *journal;
 664         int ret = 0;
 665
 666         JBUFFER_TRACE(jh, "entry");
 667
 668         if ((transaction = jh->b_cp_transaction) == NULL) {
 669                 JBUFFER_TRACE(jh, "not on transaction");
 670                 goto out;
 671         }
 672         journal = transaction->t_journal;
 673
 674         __buffer_unlink(jh);
 675         jh->b_cp_transaction = NULL;
 676
 677         if (transaction->t_checkpoint_list != NULL ||
 678             transaction->t_checkpoint_io_list != NULL)
 679                 goto out;
 680         JBUFFER_TRACE(jh, "transaction has no more buffers");
 681
 682         /*
 683          * There is one special case to worry about: if we have just pulled the
 684          * buffer off a running or committing transaction's checkpoing list,
 685          * then even if the checkpoint list is empty, the transaction obviously
 686          * cannot be dropped!
 687          *
 688          * The locking here around t_state is a bit sleazy.
 689          * See the comment at the end of jbd2_journal_commit_transaction().
 690          */
 691         if (transaction->t_state != T_FINISHED) {
 692                 JBUFFER_TRACE(jh, "belongs to running/committing transaction");
 693                 goto out;
 694         }
 695
 696         /* OK, that was the last buffer for the transaction: we can now
 697            safely remove this transaction from the log */
 698         stats = &transaction->t_chp_stats;
 699         if (stats->cs_chp_time)
 700                 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
 701                                                     jiffies);
 702         trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
 703                                     transaction->t_tid, stats);
 704
 705         __jbd2_journal_drop_transaction(journal, transaction);
 706         kfree(transaction);
 707
 708         /* Just in case anybody was waiting for more transactions to be
 709            checkpointed... */
 710         wake_up(&journal->j_wait_logspace);
 711         ret = 1;
 712 out:
 713         JBUFFER_TRACE(jh, "exit");
 714         return ret;
 715 }
 716
 717 /*
 718  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 719  * list so that we know when it is safe to clean the transaction out of
 720  * the log.
 721  *
 722  * Called with the journal locked.
 723  * Called with j_list_lock held.
 724  */
 725 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
 726                                transaction_t *transaction)
 727 {
 728         JBUFFER_TRACE(jh, "entry");
 729         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 730         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 731
 732         jh->b_cp_transaction = transaction;
 733
 734         if (!transaction->t_checkpoint_list) {
 735                 jh->b_cpnext = jh->b_cpprev = jh;
 736         } else {
 737                 jh->b_cpnext = transaction->t_checkpoint_list;
 738                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 739                 jh->b_cpprev->b_cpnext = jh;
 740                 jh->b_cpnext->b_cpprev = jh;
 741         }
 742         transaction->t_checkpoint_list = jh;
 743 }
 744
 745 /*
 746  * We've finished with this transaction structure: adios...
 747  *
 748  * The transaction must have no links except for the checkpoint by this
 749  * point.
 750  *
 751  * Called with the journal locked.
 752  * Called with j_list_lock held.
 753  */
 754
 755 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 756 {
 757         assert_spin_locked(&journal->j_list_lock);
 758         if (transaction->t_cpnext) {
 759                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 760                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 761                 if (journal->j_checkpoint_transactions == transaction)
 762                         journal->j_checkpoint_transactions =
 763                                 transaction->t_cpnext;
 764                 if (journal->j_checkpoint_transactions == transaction)
 765                         journal->j_checkpoint_transactions = NULL;
 766         }
 767
 768         J_ASSERT(transaction->t_state == T_FINISHED);
 769         J_ASSERT(transaction->t_buffers == NULL);
 770         J_ASSERT(transaction->t_forget == NULL);
 771         J_ASSERT(transaction->t_iobuf_list == NULL);
 772         J_ASSERT(transaction->t_shadow_list == NULL);
 773         J_ASSERT(transaction->t_log_list == NULL);
 774         J_ASSERT(transaction->t_checkpoint_list == NULL);
 775         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 776         J_ASSERT(transaction->t_updates == 0);
 777         J_ASSERT(journal->j_committing_transaction != transaction);
 778         J_ASSERT(journal->j_running_transaction != transaction);
 779
 780         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 781 }