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   1 /*
   2  * linux/fs/jbd/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/jbd.h>
  23 #include <linux/errno.h>
  24 #include <linux/slab.h>
  25
  26 /*
  27  * Unlink a buffer from a transaction checkpoint list.
  28  *
  29  * Called with j_list_lock held.
  30  */
  31 static inline void __buffer_unlink_first(struct journal_head *jh)
  32 {
  33         transaction_t *transaction = jh->b_cp_transaction;
  34
  35         jh->b_cpnext->b_cpprev = jh->b_cpprev;
  36         jh->b_cpprev->b_cpnext = jh->b_cpnext;
  37         if (transaction->t_checkpoint_list == jh) {
  38                 transaction->t_checkpoint_list = jh->b_cpnext;
  39                 if (transaction->t_checkpoint_list == jh)
  40                         transaction->t_checkpoint_list = NULL;
  41         }
  42 }
  43
  44 /*
  45  * Unlink a buffer from a transaction checkpoint(io) list.
  46  *
  47  * Called with j_list_lock held.
  48  */
  49 static inline void __buffer_unlink(struct journal_head *jh)
  50 {
  51         transaction_t *transaction = jh->b_cp_transaction;
  52
  53         __buffer_unlink_first(jh);
  54         if (transaction->t_checkpoint_io_list == jh) {
  55                 transaction->t_checkpoint_io_list = jh->b_cpnext;
  56                 if (transaction->t_checkpoint_io_list == jh)
  57                         transaction->t_checkpoint_io_list = NULL;
  58         }
  59 }
  60
  61 /*
  62  * Move a buffer from the checkpoint list to the checkpoint io list
  63  *
  64  * Called with j_list_lock held
  65  */
  66 static inline void __buffer_relink_io(struct journal_head *jh)
  67 {
  68         transaction_t *transaction = jh->b_cp_transaction;
  69
  70         __buffer_unlink_first(jh);
  71
  72         if (!transaction->t_checkpoint_io_list) {
  73                 jh->b_cpnext = jh->b_cpprev = jh;
  74         } else {
  75                 jh->b_cpnext = transaction->t_checkpoint_io_list;
  76                 jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
  77                 jh->b_cpprev->b_cpnext = jh;
  78                 jh->b_cpnext->b_cpprev = jh;
  79         }
  80         transaction->t_checkpoint_io_list = jh;
  81 }
  82
  83 /*
  84  * Try to release a checkpointed buffer from its transaction.
  85  * Returns 1 if we released it and 2 if we also released the
  86  * whole transaction.
  87  *
  88  * Requires j_list_lock
  89  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  90  */
  91 static int __try_to_free_cp_buf(struct journal_head *jh)
  92 {
  93         int ret = 0;
  94         struct buffer_head *bh = jh2bh(jh);
  95
  96         if (jh->b_jlist == BJ_None && !buffer_locked(bh) &&
  97             !buffer_dirty(bh) && !buffer_write_io_error(bh)) {
  98                 JBUFFER_TRACE(jh, "remove from checkpoint list");
  99                 ret = __journal_remove_checkpoint(jh) + 1;
 100                 jbd_unlock_bh_state(bh);
 101                 journal_remove_journal_head(bh);
 102                 BUFFER_TRACE(bh, "release");
 103                 __brelse(bh);
 104         } else {
 105                 jbd_unlock_bh_state(bh);
 106         }
 107         return ret;
 108 }
 109
 110 /*
 111  * __log_wait_for_space: wait until there is space in the journal.
 112  *
 113  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
 114  * for a checkpoint to free up some space in the log.
 115  */
 116 void __log_wait_for_space(journal_t *journal)
 117 {
 118         int nblocks;
 119         assert_spin_locked(&journal->j_state_lock);
 120
 121         nblocks = jbd_space_needed(journal);
 122         while (__log_space_left(journal) < nblocks) {
 123                 if (journal->j_flags & JFS_ABORT)
 124                         return;
 125                 spin_unlock(&journal->j_state_lock);
 126                 mutex_lock(&journal->j_checkpoint_mutex);
 127
 128                 /*
 129                  * Test again, another process may have checkpointed while we
 130                  * were waiting for the checkpoint lock. If there are no
 131                  * outstanding transactions there is nothing to checkpoint and
 132                  * we can't make progress. Abort the journal in this case.
 133                  */
 134                 spin_lock(&journal->j_state_lock);
 135                 spin_lock(&journal->j_list_lock);
 136                 nblocks = jbd_space_needed(journal);
 137                 if (__log_space_left(journal) < nblocks) {
 138                         int chkpt = journal->j_checkpoint_transactions != NULL;
 139
 140                         spin_unlock(&journal->j_list_lock);
 141                         spin_unlock(&journal->j_state_lock);
 142                         if (chkpt) {
 143                                 log_do_checkpoint(journal);
 144                         } else {
 145                                 printk(KERN_ERR "%s: no transactions\n",
 146                                        __func__);
 147                                 journal_abort(journal, 0);
 148                         }
 149
 150                         spin_lock(&journal->j_state_lock);
 151                 } else {
 152                         spin_unlock(&journal->j_list_lock);
 153                 }
 154                 mutex_unlock(&journal->j_checkpoint_mutex);
 155         }
 156 }
 157
 158 /*
 159  * We were unable to perform jbd_trylock_bh_state() inside j_list_lock.
 160  * The caller must restart a list walk.  Wait for someone else to run
 161  * jbd_unlock_bh_state().
 162  */
 163 static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
 164         __releases(journal->j_list_lock)
 165 {
 166         get_bh(bh);
 167         spin_unlock(&journal->j_list_lock);
 168         jbd_lock_bh_state(bh);
 169         jbd_unlock_bh_state(bh);
 170         put_bh(bh);
 171 }
 172
 173 /*
 174  * Clean up transaction's list of buffers submitted for io.
 175  * We wait for any pending IO to complete and remove any clean
 176  * buffers. Note that we take the buffers in the opposite ordering
 177  * from the one in which they were submitted for IO.
 178  *
 179  * Return 0 on success, and return <0 if some buffers have failed
 180  * to be written out.
 181  *
 182  * Called with j_list_lock held.
 183  */
 184 static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
 185 {
 186         struct journal_head *jh;
 187         struct buffer_head *bh;
 188         tid_t this_tid;
 189         int released = 0;
 190         int ret = 0;
 191
 192         this_tid = transaction->t_tid;
 193 restart:
 194         /* Did somebody clean up the transaction in the meanwhile? */
 195         if (journal->j_checkpoint_transactions != transaction ||
 196                         transaction->t_tid != this_tid)
 197                 return ret;
 198         while (!released && transaction->t_checkpoint_io_list) {
 199                 jh = transaction->t_checkpoint_io_list;
 200                 bh = jh2bh(jh);
 201                 if (!jbd_trylock_bh_state(bh)) {
 202                         jbd_sync_bh(journal, bh);
 203                         spin_lock(&journal->j_list_lock);
 204                         goto restart;
 205                 }
 206                 if (buffer_locked(bh)) {
 207                         atomic_inc(&bh->b_count);
 208                         spin_unlock(&journal->j_list_lock);
 209                         jbd_unlock_bh_state(bh);
 210                         wait_on_buffer(bh);
 211                         /* the journal_head may have gone by now */
 212                         BUFFER_TRACE(bh, "brelse");
 213                         __brelse(bh);
 214                         spin_lock(&journal->j_list_lock);
 215                         goto restart;
 216                 }
 217                 if (unlikely(buffer_write_io_error(bh)))
 218                         ret = -EIO;
 219
 220                 /*
 221                  * Now in whatever state the buffer currently is, we know that
 222                  * it has been written out and so we can drop it from the list
 223                  */
 224                 released = __journal_remove_checkpoint(jh);
 225                 jbd_unlock_bh_state(bh);
 226                 journal_remove_journal_head(bh);
 227                 __brelse(bh);
 228         }
 229
 230         return ret;
 231 }
 232
 233 #define NR_BATCH        64
 234
 235 static void
 236 __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
 237 {
 238         int i;
 239
 240         ll_rw_block(SWRITE, *batch_count, bhs);
 241         for (i = 0; i < *batch_count; i++) {
 242                 struct buffer_head *bh = bhs[i];
 243                 clear_buffer_jwrite(bh);
 244                 BUFFER_TRACE(bh, "brelse");
 245                 __brelse(bh);
 246         }
 247         *batch_count = 0;
 248 }
 249
 250 /*
 251  * Try to flush one buffer from the checkpoint list to disk.
 252  *
 253  * Return 1 if something happened which requires us to abort the current
 254  * scan of the checkpoint list.  Return <0 if the buffer has failed to
 255  * be written out.
 256  *
 257  * Called with j_list_lock held and drops it if 1 is returned
 258  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
 259  */
 260 static int __process_buffer(journal_t *journal, struct journal_head *jh,
 261                         struct buffer_head **bhs, int *batch_count)
 262 {
 263         struct buffer_head *bh = jh2bh(jh);
 264         int ret = 0;
 265
 266         if (buffer_locked(bh)) {
 267                 atomic_inc(&bh->b_count);
 268                 spin_unlock(&journal->j_list_lock);
 269                 jbd_unlock_bh_state(bh);
 270                 wait_on_buffer(bh);
 271                 /* the journal_head may have gone by now */
 272                 BUFFER_TRACE(bh, "brelse");
 273                 __brelse(bh);
 274                 ret = 1;
 275         } else if (jh->b_transaction != NULL) {
 276                 transaction_t *t = jh->b_transaction;
 277                 tid_t tid = t->t_tid;
 278
 279                 spin_unlock(&journal->j_list_lock);
 280                 jbd_unlock_bh_state(bh);
 281                 log_start_commit(journal, tid);
 282                 log_wait_commit(journal, tid);
 283                 ret = 1;
 284         } else if (!buffer_dirty(bh)) {
 285                 ret = 1;
 286                 if (unlikely(buffer_write_io_error(bh)))
 287                         ret = -EIO;
 288                 J_ASSERT_JH(jh, !buffer_jbddirty(bh));
 289                 BUFFER_TRACE(bh, "remove from checkpoint");
 290                 __journal_remove_checkpoint(jh);
 291                 spin_unlock(&journal->j_list_lock);
 292                 jbd_unlock_bh_state(bh);
 293                 journal_remove_journal_head(bh);
 294                 __brelse(bh);
 295         } else {
 296                 /*
 297                  * Important: we are about to write the buffer, and
 298                  * possibly block, while still holding the journal lock.
 299                  * We cannot afford to let the transaction logic start
 300                  * messing around with this buffer before we write it to
 301                  * disk, as that would break recoverability.
 302                  */
 303                 BUFFER_TRACE(bh, "queue");
 304                 get_bh(bh);
 305                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 306                 set_buffer_jwrite(bh);
 307                 bhs[*batch_count] = bh;
 308                 __buffer_relink_io(jh);
 309                 jbd_unlock_bh_state(bh);
 310                 (*batch_count)++;
 311                 if (*batch_count == NR_BATCH) {
 312                         spin_unlock(&journal->j_list_lock);
 313                         __flush_batch(journal, bhs, batch_count);
 314                         ret = 1;
 315                 }
 316         }
 317         return ret;
 318 }
 319
 320 /*
 321  * Perform an actual checkpoint. We take the first transaction on the
 322  * list of transactions to be checkpointed and send all its buffers
 323  * to disk. We submit larger chunks of data at once.
 324  *
 325  * The journal should be locked before calling this function.
 326  * Called with j_checkpoint_mutex held.
 327  */
 328 int log_do_checkpoint(journal_t *journal)
 329 {
 330         transaction_t *transaction;
 331         tid_t this_tid;
 332         int result;
 333
 334         jbd_debug(1, "Start checkpoint\n");
 335
 336         /*
 337          * First thing: if there are any transactions in the log which
 338          * don't need checkpointing, just eliminate them from the
 339          * journal straight away.
 340          */
 341         result = cleanup_journal_tail(journal);
 342         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 343         if (result <= 0)
 344                 return result;
 345
 346         /*
 347          * OK, we need to start writing disk blocks.  Take one transaction
 348          * and write it.
 349          */
 350         result = 0;
 351         spin_lock(&journal->j_list_lock);
 352         if (!journal->j_checkpoint_transactions)
 353                 goto out;
 354         transaction = journal->j_checkpoint_transactions;
 355         this_tid = transaction->t_tid;
 356 restart:
 357         /*
 358          * If someone cleaned up this transaction while we slept, we're
 359          * done (maybe it's a new transaction, but it fell at the same
 360          * address).
 361          */
 362         if (journal->j_checkpoint_transactions == transaction &&
 363                         transaction->t_tid == this_tid) {
 364                 int batch_count = 0;
 365                 struct buffer_head *bhs[NR_BATCH];
 366                 struct journal_head *jh;
 367                 int retry = 0, err;
 368
 369                 while (!retry && transaction->t_checkpoint_list) {
 370                         struct buffer_head *bh;
 371
 372                         jh = transaction->t_checkpoint_list;
 373                         bh = jh2bh(jh);
 374                         if (!jbd_trylock_bh_state(bh)) {
 375                                 jbd_sync_bh(journal, bh);
 376                                 retry = 1;
 377                                 break;
 378                         }
 379                         retry = __process_buffer(journal, jh, bhs,&batch_count);
 380                         if (retry < 0 && !result)
 381                                 result = retry;
 382                         if (!retry && (need_resched() ||
 383                                 spin_needbreak(&journal->j_list_lock))) {
 384                                 spin_unlock(&journal->j_list_lock);
 385                                 retry = 1;
 386                                 break;
 387                         }
 388                 }
 389
 390                 if (batch_count) {
 391                         if (!retry) {
 392                                 spin_unlock(&journal->j_list_lock);
 393                                 retry = 1;
 394                         }
 395                         __flush_batch(journal, bhs, &batch_count);
 396                 }
 397
 398                 if (retry) {
 399                         spin_lock(&journal->j_list_lock);
 400                         goto restart;
 401                 }
 402                 /*
 403                  * Now we have cleaned up the first transaction's checkpoint
 404                  * list. Let's clean up the second one
 405                  */
 406                 err = __wait_cp_io(journal, transaction);
 407                 if (!result)
 408                         result = err;
 409         }
 410 out:
 411         spin_unlock(&journal->j_list_lock);
 412         if (result < 0)
 413                 journal_abort(journal, result);
 414         else
 415                 result = cleanup_journal_tail(journal);
 416
 417         return (result < 0) ? result : 0;
 418 }
 419
 420 /*
 421  * Check the list of checkpoint transactions for the journal to see if
 422  * we have already got rid of any since the last update of the log tail
 423  * in the journal superblock.  If so, we can instantly roll the
 424  * superblock forward to remove those transactions from the log.
 425  *
 426  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 427  *
 428  * Called with the journal lock held.
 429  *
 430  * This is the only part of the journaling code which really needs to be
 431  * aware of transaction aborts.  Checkpointing involves writing to the
 432  * main filesystem area rather than to the journal, so it can proceed
 433  * even in abort state, but we must not update the super block if
 434  * checkpointing may have failed.  Otherwise, we would lose some metadata
 435  * buffers which should be written-back to the filesystem.
 436  */
 437
 438 int cleanup_journal_tail(journal_t *journal)
 439 {
 440         transaction_t * transaction;
 441         tid_t           first_tid;
 442         unsigned long   blocknr, freed;
 443
 444         if (is_journal_aborted(journal))
 445                 return 1;
 446
 447         /* OK, work out the oldest transaction remaining in the log, and
 448          * the log block it starts at.
 449          *
 450          * If the log is now empty, we need to work out which is the
 451          * next transaction ID we will write, and where it will
 452          * start. */
 453
 454         spin_lock(&journal->j_state_lock);
 455         spin_lock(&journal->j_list_lock);
 456         transaction = journal->j_checkpoint_transactions;
 457         if (transaction) {
 458                 first_tid = transaction->t_tid;
 459                 blocknr = transaction->t_log_start;
 460         } else if ((transaction = journal->j_committing_transaction) != NULL) {
 461                 first_tid = transaction->t_tid;
 462                 blocknr = transaction->t_log_start;
 463         } else if ((transaction = journal->j_running_transaction) != NULL) {
 464                 first_tid = transaction->t_tid;
 465                 blocknr = journal->j_head;
 466         } else {
 467                 first_tid = journal->j_transaction_sequence;
 468                 blocknr = journal->j_head;
 469         }
 470         spin_unlock(&journal->j_list_lock);
 471         J_ASSERT(blocknr != 0);
 472
 473         /* If the oldest pinned transaction is at the tail of the log
 474            already then there's not much we can do right now. */
 475         if (journal->j_tail_sequence == first_tid) {
 476                 spin_unlock(&journal->j_state_lock);
 477                 return 1;
 478         }
 479
 480         /* OK, update the superblock to recover the freed space.
 481          * Physical blocks come first: have we wrapped beyond the end of
 482          * the log?  */
 483         freed = blocknr - journal->j_tail;
 484         if (blocknr < journal->j_tail)
 485                 freed = freed + journal->j_last - journal->j_first;
 486
 487         jbd_debug(1,
 488                   "Cleaning journal tail from %d to %d (offset %lu), "
 489                   "freeing %lu\n",
 490                   journal->j_tail_sequence, first_tid, blocknr, freed);
 491
 492         journal->j_free += freed;
 493         journal->j_tail_sequence = first_tid;
 494         journal->j_tail = blocknr;
 495         spin_unlock(&journal->j_state_lock);
 496         if (!(journal->j_flags & JFS_ABORT))
 497                 journal_update_superblock(journal, 1);
 498         return 0;
 499 }
 500
 501
 502 /* Checkpoint list management */
 503
 504 /*
 505  * journal_clean_one_cp_list
 506  *
 507  * Find all the written-back checkpoint buffers in the given list and release them.
 508  *
 509  * Called with the journal locked.
 510  * Called with j_list_lock held.
 511  * Returns number of bufers reaped (for debug)
 512  */
 513
 514 static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
 515 {
 516         struct journal_head *last_jh;
 517         struct journal_head *next_jh = jh;
 518         int ret, freed = 0;
 519
 520         *released = 0;
 521         if (!jh)
 522                 return 0;
 523
 524         last_jh = jh->b_cpprev;
 525         do {
 526                 jh = next_jh;
 527                 next_jh = jh->b_cpnext;
 528                 /* Use trylock because of the ranking */
 529                 if (jbd_trylock_bh_state(jh2bh(jh))) {
 530                         ret = __try_to_free_cp_buf(jh);
 531                         if (ret) {
 532                                 freed++;
 533                                 if (ret == 2) {
 534                                         *released = 1;
 535                                         return freed;
 536                                 }
 537                         }
 538                 }
 539                 /*
 540                  * This function only frees up some memory
 541                  * if possible so we dont have an obligation
 542                  * to finish processing. Bail out if preemption
 543                  * requested:
 544                  */
 545                 if (need_resched())
 546                         return freed;
 547         } while (jh != last_jh);
 548
 549         return freed;
 550 }
 551
 552 /*
 553  * journal_clean_checkpoint_list
 554  *
 555  * Find all the written-back checkpoint buffers in the journal and release them.
 556  *
 557  * Called with the journal locked.
 558  * Called with j_list_lock held.
 559  * Returns number of buffers reaped (for debug)
 560  */
 561
 562 int __journal_clean_checkpoint_list(journal_t *journal)
 563 {
 564         transaction_t *transaction, *last_transaction, *next_transaction;
 565         int ret = 0;
 566         int released;
 567
 568         transaction = journal->j_checkpoint_transactions;
 569         if (!transaction)
 570                 goto out;
 571
 572         last_transaction = transaction->t_cpprev;
 573         next_transaction = transaction;
 574         do {
 575                 transaction = next_transaction;
 576                 next_transaction = transaction->t_cpnext;
 577                 ret += journal_clean_one_cp_list(transaction->
 578                                 t_checkpoint_list, &released);
 579                 /*
 580                  * This function only frees up some memory if possible so we
 581                  * dont have an obligation to finish processing. Bail out if
 582                  * preemption requested:
 583                  */
 584                 if (need_resched())
 585                         goto out;
 586                 if (released)
 587                         continue;
 588                 /*
 589                  * It is essential that we are as careful as in the case of
 590                  * t_checkpoint_list with removing the buffer from the list as
 591                  * we can possibly see not yet submitted buffers on io_list
 592                  */
 593                 ret += journal_clean_one_cp_list(transaction->
 594                                 t_checkpoint_io_list, &released);
 595                 if (need_resched())
 596                         goto out;
 597         } while (transaction != last_transaction);
 598 out:
 599         return ret;
 600 }
 601
 602 /*
 603  * journal_remove_checkpoint: called after a buffer has been committed
 604  * to disk (either by being write-back flushed to disk, or being
 605  * committed to the log).
 606  *
 607  * We cannot safely clean a transaction out of the log until all of the
 608  * buffer updates committed in that transaction have safely been stored
 609  * elsewhere on disk.  To achieve this, all of the buffers in a
 610  * transaction need to be maintained on the transaction's checkpoint
 611  * lists until they have been rewritten, at which point this function is
 612  * called to remove the buffer from the existing transaction's
 613  * checkpoint lists.
 614  *
 615  * The function returns 1 if it frees the transaction, 0 otherwise.
 616  *
 617  * This function is called with the journal locked.
 618  * This function is called with j_list_lock held.
 619  * This function is called with jbd_lock_bh_state(jh2bh(jh))
 620  */
 621
 622 int __journal_remove_checkpoint(struct journal_head *jh)
 623 {
 624         transaction_t *transaction;
 625         journal_t *journal;
 626         int ret = 0;
 627
 628         JBUFFER_TRACE(jh, "entry");
 629
 630         if ((transaction = jh->b_cp_transaction) == NULL) {
 631                 JBUFFER_TRACE(jh, "not on transaction");
 632                 goto out;
 633         }
 634         journal = transaction->t_journal;
 635
 636         __buffer_unlink(jh);
 637         jh->b_cp_transaction = NULL;
 638
 639         if (transaction->t_checkpoint_list != NULL ||
 640             transaction->t_checkpoint_io_list != NULL)
 641                 goto out;
 642         JBUFFER_TRACE(jh, "transaction has no more buffers");
 643
 644         /*
 645          * There is one special case to worry about: if we have just pulled the
 646          * buffer off a running or committing transaction's checkpoing list,
 647          * then even if the checkpoint list is empty, the transaction obviously
 648          * cannot be dropped!
 649          *
 650          * The locking here around t_state is a bit sleazy.
 651          * See the comment at the end of journal_commit_transaction().
 652          */
 653         if (transaction->t_state != T_FINISHED) {
 654                 JBUFFER_TRACE(jh, "belongs to running/committing transaction");
 655                 goto out;
 656         }
 657
 658         /* OK, that was the last buffer for the transaction: we can now
 659            safely remove this transaction from the log */
 660
 661         __journal_drop_transaction(journal, transaction);
 662
 663         /* Just in case anybody was waiting for more transactions to be
 664            checkpointed... */
 665         wake_up(&journal->j_wait_logspace);
 666         ret = 1;
 667 out:
 668         JBUFFER_TRACE(jh, "exit");
 669         return ret;
 670 }
 671
 672 /*
 673  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 674  * list so that we know when it is safe to clean the transaction out of
 675  * the log.
 676  *
 677  * Called with the journal locked.
 678  * Called with j_list_lock held.
 679  */
 680 void __journal_insert_checkpoint(struct journal_head *jh,
 681                                transaction_t *transaction)
 682 {
 683         JBUFFER_TRACE(jh, "entry");
 684         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 685         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 686
 687         jh->b_cp_transaction = transaction;
 688
 689         if (!transaction->t_checkpoint_list) {
 690                 jh->b_cpnext = jh->b_cpprev = jh;
 691         } else {
 692                 jh->b_cpnext = transaction->t_checkpoint_list;
 693                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 694                 jh->b_cpprev->b_cpnext = jh;
 695                 jh->b_cpnext->b_cpprev = jh;
 696         }
 697         transaction->t_checkpoint_list = jh;
 698 }
 699
 700 /*
 701  * We've finished with this transaction structure: adios...
 702  *
 703  * The transaction must have no links except for the checkpoint by this
 704  * point.
 705  *
 706  * Called with the journal locked.
 707  * Called with j_list_lock held.
 708  */
 709
 710 void __journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 711 {
 712         assert_spin_locked(&journal->j_list_lock);
 713         if (transaction->t_cpnext) {
 714                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 715                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 716                 if (journal->j_checkpoint_transactions == transaction)
 717                         journal->j_checkpoint_transactions =
 718                                 transaction->t_cpnext;
 719                 if (journal->j_checkpoint_transactions == transaction)
 720                         journal->j_checkpoint_transactions = NULL;
 721         }
 722
 723         J_ASSERT(transaction->t_state == T_FINISHED);
 724         J_ASSERT(transaction->t_buffers == NULL);
 725         J_ASSERT(transaction->t_sync_datalist == NULL);
 726         J_ASSERT(transaction->t_forget == NULL);
 727         J_ASSERT(transaction->t_iobuf_list == NULL);
 728         J_ASSERT(transaction->t_shadow_list == NULL);
 729         J_ASSERT(transaction->t_log_list == NULL);
 730         J_ASSERT(transaction->t_checkpoint_list == NULL);
 731         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 732         J_ASSERT(transaction->t_updates == 0);
 733         J_ASSERT(journal->j_committing_transaction != transaction);
 734         J_ASSERT(journal->j_running_transaction != transaction);
 735
 736         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 737         kfree(transaction);
 738 }