kernel/fs/jbd/checkpoint.c

   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 #include <linux/blkdev.h>
  26 #include <trace/events/jbd.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                 /*
 101                  * Get our reference so that bh cannot be freed before
 102                  * we unlock it
 103                  */
 104                 get_bh(bh);
 105                 JBUFFER_TRACE(jh, "remove from checkpoint list");
 106                 ret = __journal_remove_checkpoint(jh) + 1;
 107                 jbd_unlock_bh_state(bh);
 108                 BUFFER_TRACE(bh, "release");
 109                 __brelse(bh);
 110         } else {
 111                 jbd_unlock_bh_state(bh);
 112         }
 113         return ret;
 114 }
 115
 116 /*
 117  * __log_wait_for_space: wait until there is space in the journal.
 118  *
 119  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
 120  * for a checkpoint to free up some space in the log.
 121  */
 122 void __log_wait_for_space(journal_t *journal)
 123 {
 124         int nblocks, space_left;
 125         assert_spin_locked(&journal->j_state_lock);
 126
 127         nblocks = jbd_space_needed(journal);
 128         while (__log_space_left(journal) < nblocks) {
 129                 if (journal->j_flags & JFS_ABORT)
 130                         return;
 131                 spin_unlock(&journal->j_state_lock);
 132                 if (current->plug)
 133                         io_schedule();
 134                 mutex_lock(&journal->j_checkpoint_mutex);
 135
 136                 /*
 137                  * Test again, another process may have checkpointed while we
 138                  * were waiting for the checkpoint lock. If there are no
 139                  * transactions ready to be checkpointed, try to recover
 140                  * journal space by calling cleanup_journal_tail(), and if
 141                  * that doesn't work, by waiting for the currently committing
 142                  * transaction to complete.  If there is absolutely no way
 143                  * to make progress, this is either a BUG or corrupted
 144                  * filesystem, so abort the journal and leave a stack
 145                  * trace for forensic evidence.
 146                  */
 147                 spin_lock(&journal->j_state_lock);
 148                 spin_lock(&journal->j_list_lock);
 149                 nblocks = jbd_space_needed(journal);
 150                 space_left = __log_space_left(journal);
 151                 if (space_left < nblocks) {
 152                         int chkpt = journal->j_checkpoint_transactions != NULL;
 153                         tid_t tid = 0;
 154
 155                         if (journal->j_committing_transaction)
 156                                 tid = journal->j_committing_transaction->t_tid;
 157                         spin_unlock(&journal->j_list_lock);
 158                         spin_unlock(&journal->j_state_lock);
 159                         if (chkpt) {
 160                                 log_do_checkpoint(journal);
 161                         } else if (cleanup_journal_tail(journal) == 0) {
 162                                 /* We were able to recover space; yay! */
 163                                 ;
 164                         } else if (tid) {
 165                                 log_wait_commit(journal, tid);
 166                         } else {
 167                                 printk(KERN_ERR "%s: needed %d blocks and "
 168                                        "only had %d space available\n",
 169                                        __func__, nblocks, space_left);
 170                                 printk(KERN_ERR "%s: no way to get more "
 171                                        "journal space\n", __func__);
 172                                 WARN_ON(1);
 173                                 journal_abort(journal, 0);
 174                         }
 175                         spin_lock(&journal->j_state_lock);
 176                 } else {
 177                         spin_unlock(&journal->j_list_lock);
 178                 }
 179                 mutex_unlock(&journal->j_checkpoint_mutex);
 180         }
 181 }
 182
 183 /*
 184  * We were unable to perform jbd_trylock_bh_state() inside j_list_lock.
 185  * The caller must restart a list walk.  Wait for someone else to run
 186  * jbd_unlock_bh_state().
 187  */
 188 static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
 189         __releases(journal->j_list_lock)
 190 {
 191         get_bh(bh);
 192         spin_unlock(&journal->j_list_lock);
 193         jbd_lock_bh_state(bh);
 194         jbd_unlock_bh_state(bh);
 195         put_bh(bh);
 196 }
 197
 198 /*
 199  * Clean up transaction's list of buffers submitted for io.
 200  * We wait for any pending IO to complete and remove any clean
 201  * buffers. Note that we take the buffers in the opposite ordering
 202  * from the one in which they were submitted for IO.
 203  *
 204  * Return 0 on success, and return <0 if some buffers have failed
 205  * to be written out.
 206  *
 207  * Called with j_list_lock held.
 208  */
 209 static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
 210 {
 211         struct journal_head *jh;
 212         struct buffer_head *bh;
 213         tid_t this_tid;
 214         int released = 0;
 215         int ret = 0;
 216
 217         this_tid = transaction->t_tid;
 218 restart:
 219         /* Did somebody clean up the transaction in the meanwhile? */
 220         if (journal->j_checkpoint_transactions != transaction ||
 221                         transaction->t_tid != this_tid)
 222                 return ret;
 223         while (!released && transaction->t_checkpoint_io_list) {
 224                 jh = transaction->t_checkpoint_io_list;
 225                 bh = jh2bh(jh);
 226                 if (!jbd_trylock_bh_state(bh)) {
 227                         jbd_sync_bh(journal, bh);
 228                         spin_lock(&journal->j_list_lock);
 229                         goto restart;
 230                 }
 231                 get_bh(bh);
 232                 if (buffer_locked(bh)) {
 233                         spin_unlock(&journal->j_list_lock);
 234                         jbd_unlock_bh_state(bh);
 235                         wait_on_buffer(bh);
 236                         /* the journal_head may have gone by now */
 237                         BUFFER_TRACE(bh, "brelse");
 238                         __brelse(bh);
 239                         spin_lock(&journal->j_list_lock);
 240                         goto restart;
 241                 }
 242                 if (unlikely(buffer_write_io_error(bh)))
 243                         ret = -EIO;
 244
 245                 /*
 246                  * Now in whatever state the buffer currently is, we know that
 247                  * it has been written out and so we can drop it from the list
 248                  */
 249                 released = __journal_remove_checkpoint(jh);
 250                 jbd_unlock_bh_state(bh);
 251                 __brelse(bh);
 252         }
 253
 254         return ret;
 255 }
 256
 257 #define NR_BATCH        64
 258
 259 static void
 260 __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
 261 {
 262         int i;
 263         struct blk_plug plug;
 264
 265         blk_start_plug(&plug);
 266         for (i = 0; i < *batch_count; i++)
 267                 write_dirty_buffer(bhs[i], WRITE_SYNC);
 268         blk_finish_plug(&plug);
 269
 270         for (i = 0; i < *batch_count; i++) {
 271                 struct buffer_head *bh = bhs[i];
 272                 clear_buffer_jwrite(bh);
 273                 BUFFER_TRACE(bh, "brelse");
 274                 __brelse(bh);
 275         }
 276         *batch_count = 0;
 277 }
 278
 279 /*
 280  * Try to flush one buffer from the checkpoint list to disk.
 281  *
 282  * Return 1 if something happened which requires us to abort the current
 283  * scan of the checkpoint list.  Return <0 if the buffer has failed to
 284  * be written out.
 285  *
 286  * Called with j_list_lock held and drops it if 1 is returned
 287  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
 288  */
 289 static int __process_buffer(journal_t *journal, struct journal_head *jh,
 290                         struct buffer_head **bhs, int *batch_count)
 291 {
 292         struct buffer_head *bh = jh2bh(jh);
 293         int ret = 0;
 294
 295         if (buffer_locked(bh)) {
 296                 get_bh(bh);
 297                 spin_unlock(&journal->j_list_lock);
 298                 jbd_unlock_bh_state(bh);
 299                 wait_on_buffer(bh);
 300                 /* the journal_head may have gone by now */
 301                 BUFFER_TRACE(bh, "brelse");
 302                 __brelse(bh);
 303                 ret = 1;
 304         } else if (jh->b_transaction != NULL) {
 305                 transaction_t *t = jh->b_transaction;
 306                 tid_t tid = t->t_tid;
 307
 308                 spin_unlock(&journal->j_list_lock);
 309                 jbd_unlock_bh_state(bh);
 310                 log_start_commit(journal, tid);
 311                 log_wait_commit(journal, tid);
 312                 ret = 1;
 313         } else if (!buffer_dirty(bh)) {
 314                 ret = 1;
 315                 if (unlikely(buffer_write_io_error(bh)))
 316                         ret = -EIO;
 317                 get_bh(bh);
 318                 J_ASSERT_JH(jh, !buffer_jbddirty(bh));
 319                 BUFFER_TRACE(bh, "remove from checkpoint");
 320                 __journal_remove_checkpoint(jh);
 321                 spin_unlock(&journal->j_list_lock);
 322                 jbd_unlock_bh_state(bh);
 323                 __brelse(bh);
 324         } else {
 325                 /*
 326                  * Important: we are about to write the buffer, and
 327                  * possibly block, while still holding the journal lock.
 328                  * We cannot afford to let the transaction logic start
 329                  * messing around with this buffer before we write it to
 330                  * disk, as that would break recoverability.
 331                  */
 332                 BUFFER_TRACE(bh, "queue");
 333                 get_bh(bh);
 334                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 335                 set_buffer_jwrite(bh);
 336                 bhs[*batch_count] = bh;
 337                 __buffer_relink_io(jh);
 338                 jbd_unlock_bh_state(bh);
 339                 (*batch_count)++;
 340                 if (*batch_count == NR_BATCH) {
 341                         spin_unlock(&journal->j_list_lock);
 342                         __flush_batch(journal, bhs, batch_count);
 343                         ret = 1;
 344                 }
 345         }
 346         return ret;
 347 }
 348
 349 /*
 350  * Perform an actual checkpoint. We take the first transaction on the
 351  * list of transactions to be checkpointed and send all its buffers
 352  * to disk. We submit larger chunks of data at once.
 353  *
 354  * The journal should be locked before calling this function.
 355  * Called with j_checkpoint_mutex held.
 356  */
 357 int log_do_checkpoint(journal_t *journal)
 358 {
 359         transaction_t *transaction;
 360         tid_t this_tid;
 361         int result;
 362
 363         jbd_debug(1, "Start checkpoint\n");
 364
 365         /*
 366          * First thing: if there are any transactions in the log which
 367          * don't need checkpointing, just eliminate them from the
 368          * journal straight away.
 369          */
 370         result = cleanup_journal_tail(journal);
 371         trace_jbd_checkpoint(journal, result);
 372         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 373         if (result <= 0)
 374                 return result;
 375
 376         /*
 377          * OK, we need to start writing disk blocks.  Take one transaction
 378          * and write it.
 379          */
 380         result = 0;
 381         spin_lock(&journal->j_list_lock);
 382         if (!journal->j_checkpoint_transactions)
 383                 goto out;
 384         transaction = journal->j_checkpoint_transactions;
 385         this_tid = transaction->t_tid;
 386 restart:
 387         /*
 388          * If someone cleaned up this transaction while we slept, we're
 389          * done (maybe it's a new transaction, but it fell at the same
 390          * address).
 391          */
 392         if (journal->j_checkpoint_transactions == transaction &&
 393                         transaction->t_tid == this_tid) {
 394                 int batch_count = 0;
 395                 struct buffer_head *bhs[NR_BATCH];
 396                 struct journal_head *jh;
 397                 int retry = 0, err;
 398
 399                 while (!retry && transaction->t_checkpoint_list) {
 400                         struct buffer_head *bh;
 401
 402                         jh = transaction->t_checkpoint_list;
 403                         bh = jh2bh(jh);
 404                         if (!jbd_trylock_bh_state(bh)) {
 405                                 jbd_sync_bh(journal, bh);
 406                                 retry = 1;
 407                                 break;
 408                         }
 409                         retry = __process_buffer(journal, jh, bhs,&batch_count);
 410                         if (retry < 0 && !result)
 411                                 result = retry;
 412                         if (!retry && (need_resched() ||
 413                                 spin_needbreak(&journal->j_list_lock))) {
 414                                 spin_unlock(&journal->j_list_lock);
 415                                 retry = 1;
 416                                 break;
 417                         }
 418                 }
 419
 420                 if (batch_count) {
 421                         if (!retry) {
 422                                 spin_unlock(&journal->j_list_lock);
 423                                 retry = 1;
 424                         }
 425                         __flush_batch(journal, bhs, &batch_count);
 426                 }
 427
 428                 if (retry) {
 429                         spin_lock(&journal->j_list_lock);
 430                         goto restart;
 431                 }
 432                 /*
 433                  * Now we have cleaned up the first transaction's checkpoint
 434                  * list. Let's clean up the second one
 435                  */
 436                 err = __wait_cp_io(journal, transaction);
 437                 if (!result)
 438                         result = err;
 439         }
 440 out:
 441         spin_unlock(&journal->j_list_lock);
 442         if (result < 0)
 443                 journal_abort(journal, result);
 444         else
 445                 result = cleanup_journal_tail(journal);
 446
 447         return (result < 0) ? result : 0;
 448 }
 449
 450 /*
 451  * Check the list of checkpoint transactions for the journal to see if
 452  * we have already got rid of any since the last update of the log tail
 453  * in the journal superblock.  If so, we can instantly roll the
 454  * superblock forward to remove those transactions from the log.
 455  *
 456  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 457  *
 458  * This is the only part of the journaling code which really needs to be
 459  * aware of transaction aborts.  Checkpointing involves writing to the
 460  * main filesystem area rather than to the journal, so it can proceed
 461  * even in abort state, but we must not update the super block if
 462  * checkpointing may have failed.  Otherwise, we would lose some metadata
 463  * buffers which should be written-back to the filesystem.
 464  */
 465
 466 int cleanup_journal_tail(journal_t *journal)
 467 {
 468         transaction_t * transaction;
 469         tid_t           first_tid;
 470         unsigned int    blocknr, freed;
 471
 472         if (is_journal_aborted(journal))
 473                 return 1;
 474
 475         /*
 476          * OK, work out the oldest transaction remaining in the log, and
 477          * the log block it starts at.
 478          *
 479          * If the log is now empty, we need to work out which is the
 480          * next transaction ID we will write, and where it will
 481          * start.
 482          */
 483         spin_lock(&journal->j_state_lock);
 484         spin_lock(&journal->j_list_lock);
 485         transaction = journal->j_checkpoint_transactions;
 486         if (transaction) {
 487                 first_tid = transaction->t_tid;
 488                 blocknr = transaction->t_log_start;
 489         } else if ((transaction = journal->j_committing_transaction) != NULL) {
 490                 first_tid = transaction->t_tid;
 491                 blocknr = transaction->t_log_start;
 492         } else if ((transaction = journal->j_running_transaction) != NULL) {
 493                 first_tid = transaction->t_tid;
 494                 blocknr = journal->j_head;
 495         } else {
 496                 first_tid = journal->j_transaction_sequence;
 497                 blocknr = journal->j_head;
 498         }
 499         spin_unlock(&journal->j_list_lock);
 500         J_ASSERT(blocknr != 0);
 501
 502         /* If the oldest pinned transaction is at the tail of the log
 503            already then there's not much we can do right now. */
 504         if (journal->j_tail_sequence == first_tid) {
 505                 spin_unlock(&journal->j_state_lock);
 506                 return 1;
 507         }
 508         spin_unlock(&journal->j_state_lock);
 509
 510         /*
 511          * We need to make sure that any blocks that were recently written out
 512          * --- perhaps by log_do_checkpoint() --- are flushed out before we
 513          * drop the transactions from the journal. Similarly we need to be sure
 514          * superblock makes it to disk before next transaction starts reusing
 515          * freed space (otherwise we could replay some blocks of the new
 516          * transaction thinking they belong to the old one). So we use
 517          * WRITE_FLUSH_FUA. It's unlikely this will be necessary, especially
 518          * with an appropriately sized journal, but we need this to guarantee
 519          * correctness.  Fortunately cleanup_journal_tail() doesn't get called
 520          * all that often.
 521          */
 522         journal_update_sb_log_tail(journal, first_tid, blocknr,
 523                                    WRITE_FLUSH_FUA);
 524
 525         spin_lock(&journal->j_state_lock);
 526         /* OK, update the superblock to recover the freed space.
 527          * Physical blocks come first: have we wrapped beyond the end of
 528          * the log?  */
 529         freed = blocknr - journal->j_tail;
 530         if (blocknr < journal->j_tail)
 531                 freed = freed + journal->j_last - journal->j_first;
 532
 533         trace_jbd_cleanup_journal_tail(journal, first_tid, blocknr, freed);
 534         jbd_debug(1,
 535                   "Cleaning journal tail from %d to %d (offset %u), "
 536                   "freeing %u\n",
 537                   journal->j_tail_sequence, first_tid, blocknr, freed);
 538
 539         journal->j_free += freed;
 540         journal->j_tail_sequence = first_tid;
 541         journal->j_tail = blocknr;
 542         spin_unlock(&journal->j_state_lock);
 543         return 0;
 544 }
 545
 546
 547 /* Checkpoint list management */
 548
 549 /*
 550  * journal_clean_one_cp_list
 551  *
 552  * Find all the written-back checkpoint buffers in the given list and release
 553  * them.
 554  *
 555  * Called with j_list_lock held.
 556  * Returns number of buffers reaped (for debug)
 557  */
 558
 559 static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
 560 {
 561         struct journal_head *last_jh;
 562         struct journal_head *next_jh = jh;
 563         int ret, freed = 0;
 564
 565         *released = 0;
 566         if (!jh)
 567                 return 0;
 568
 569         last_jh = jh->b_cpprev;
 570         do {
 571                 jh = next_jh;
 572                 next_jh = jh->b_cpnext;
 573                 /* Use trylock because of the ranking */
 574                 if (jbd_trylock_bh_state(jh2bh(jh))) {
 575                         ret = __try_to_free_cp_buf(jh);
 576                         if (ret) {
 577                                 freed++;
 578                                 if (ret == 2) {
 579                                         *released = 1;
 580                                         return freed;
 581                                 }
 582                         }
 583                 }
 584                 /*
 585                  * This function only frees up some memory
 586                  * if possible so we dont have an obligation
 587                  * to finish processing. Bail out if preemption
 588                  * requested:
 589                  */
 590                 if (need_resched())
 591                         return freed;
 592         } while (jh != last_jh);
 593
 594         return freed;
 595 }
 596
 597 /*
 598  * journal_clean_checkpoint_list
 599  *
 600  * Find all the written-back checkpoint buffers in the journal and release them.
 601  *
 602  * Called with the journal locked.
 603  * Called with j_list_lock held.
 604  * Returns number of buffers reaped (for debug)
 605  */
 606
 607 int __journal_clean_checkpoint_list(journal_t *journal)
 608 {
 609         transaction_t *transaction, *last_transaction, *next_transaction;
 610         int ret = 0;
 611         int released;
 612
 613         transaction = journal->j_checkpoint_transactions;
 614         if (!transaction)
 615                 goto out;
 616
 617         last_transaction = transaction->t_cpprev;
 618         next_transaction = transaction;
 619         do {
 620                 transaction = next_transaction;
 621                 next_transaction = transaction->t_cpnext;
 622                 ret += journal_clean_one_cp_list(transaction->
 623                                 t_checkpoint_list, &released);
 624                 /*
 625                  * This function only frees up some memory if possible so we
 626                  * dont have an obligation to finish processing. Bail out if
 627                  * preemption requested:
 628                  */
 629                 if (need_resched())
 630                         goto out;
 631                 if (released)
 632                         continue;
 633                 /*
 634                  * It is essential that we are as careful as in the case of
 635                  * t_checkpoint_list with removing the buffer from the list as
 636                  * we can possibly see not yet submitted buffers on io_list
 637                  */
 638                 ret += journal_clean_one_cp_list(transaction->
 639                                 t_checkpoint_io_list, &released);
 640                 if (need_resched())
 641                         goto out;
 642         } while (transaction != last_transaction);
 643 out:
 644         return ret;
 645 }
 646
 647 /*
 648  * journal_remove_checkpoint: called after a buffer has been committed
 649  * to disk (either by being write-back flushed to disk, or being
 650  * committed to the log).
 651  *
 652  * We cannot safely clean a transaction out of the log until all of the
 653  * buffer updates committed in that transaction have safely been stored
 654  * elsewhere on disk.  To achieve this, all of the buffers in a
 655  * transaction need to be maintained on the transaction's checkpoint
 656  * lists until they have been rewritten, at which point this function is
 657  * called to remove the buffer from the existing transaction's
 658  * checkpoint lists.
 659  *
 660  * The function returns 1 if it frees the transaction, 0 otherwise.
 661  * The function can free jh and bh.
 662  *
 663  * This function is called with j_list_lock held.
 664  * This function is called with jbd_lock_bh_state(jh2bh(jh))
 665  */
 666
 667 int __journal_remove_checkpoint(struct journal_head *jh)
 668 {
 669         transaction_t *transaction;
 670         journal_t *journal;
 671         int ret = 0;
 672
 673         JBUFFER_TRACE(jh, "entry");
 674
 675         if ((transaction = jh->b_cp_transaction) == NULL) {
 676                 JBUFFER_TRACE(jh, "not on transaction");
 677                 goto out;
 678         }
 679         journal = transaction->t_journal;
 680
 681         JBUFFER_TRACE(jh, "removing from transaction");
 682         __buffer_unlink(jh);
 683         jh->b_cp_transaction = NULL;
 684         journal_put_journal_head(jh);
 685
 686         if (transaction->t_checkpoint_list != NULL ||
 687             transaction->t_checkpoint_io_list != NULL)
 688                 goto out;
 689
 690         /*
 691          * There is one special case to worry about: if we have just pulled the
 692          * buffer off a running or committing transaction's checkpoing list,
 693          * then even if the checkpoint list is empty, the transaction obviously
 694          * cannot be dropped!
 695          *
 696          * The locking here around t_state is a bit sleazy.
 697          * See the comment at the end of journal_commit_transaction().
 698          */
 699         if (transaction->t_state != T_FINISHED)
 700                 goto out;
 701
 702         /* OK, that was the last buffer for the transaction: we can now
 703            safely remove this transaction from the log */
 704
 705         __journal_drop_transaction(journal, transaction);
 706
 707         /* Just in case anybody was waiting for more transactions to be
 708            checkpointed... */
 709         wake_up(&journal->j_wait_logspace);
 710         ret = 1;
 711 out:
 712         return ret;
 713 }
 714
 715 /*
 716  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 717  * list so that we know when it is safe to clean the transaction out of
 718  * the log.
 719  *
 720  * Called with the journal locked.
 721  * Called with j_list_lock held.
 722  */
 723 void __journal_insert_checkpoint(struct journal_head *jh,
 724                                transaction_t *transaction)
 725 {
 726         JBUFFER_TRACE(jh, "entry");
 727         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 728         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 729
 730         /* Get reference for checkpointing transaction */
 731         journal_grab_journal_head(jh2bh(jh));
 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 __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_sync_datalist == NULL);
 771         J_ASSERT(transaction->t_forget == NULL);
 772         J_ASSERT(transaction->t_iobuf_list == NULL);
 773         J_ASSERT(transaction->t_shadow_list == NULL);
 774         J_ASSERT(transaction->t_log_list == NULL);
 775         J_ASSERT(transaction->t_checkpoint_list == NULL);
 776         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 777         J_ASSERT(transaction->t_updates == 0);
 778         J_ASSERT(journal->j_committing_transaction != transaction);
 779         J_ASSERT(journal->j_running_transaction != transaction);
 780
 781         trace_jbd_drop_transaction(journal, transaction);
 782         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 783         kfree(transaction);
 784 }