err.no Git - linux-2.6/blob - fs/jbd/commit.c

   1 /*
   2  * linux/fs/commit.c
   3  *
   4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
   5  *
   6  * Copyright 1998 Red Hat corp --- 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  * Journal commit routines for the generic filesystem journaling code;
  13  * part of the ext2fs journaling system.
  14  */
  15
  16 #include <linux/time.h>
  17 #include <linux/fs.h>
  18 #include <linux/jbd.h>
  19 #include <linux/errno.h>
  20 #include <linux/slab.h>
  21 #include <linux/mm.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/smp_lock.h>
  24
  25 /*
  26  * Default IO end handler for temporary BJ_IO buffer_heads.
  27  */
  28 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
  29 {
  30         BUFFER_TRACE(bh, "");
  31         if (uptodate)
  32                 set_buffer_uptodate(bh);
  33         else
  34                 clear_buffer_uptodate(bh);
  35         unlock_buffer(bh);
  36 }
  37
  38 /*
  39  * When an ext3-ordered file is truncated, it is possible that many pages are
  40  * not sucessfully freed, because they are attached to a committing transaction.
  41  * After the transaction commits, these pages are left on the LRU, with no
  42  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
  43  * by the VM, but their apparent absence upsets the VM accounting, and it makes
  44  * the numbers in /proc/meminfo look odd.
  45  *
  46  * So here, we have a buffer which has just come off the forget list.  Look to
  47  * see if we can strip all buffers from the backing page.
  48  *
  49  * Called under lock_journal(), and possibly under journal_datalist_lock.  The
  50  * caller provided us with a ref against the buffer, and we drop that here.
  51  */
  52 static void release_buffer_page(struct buffer_head *bh)
  53 {
  54         struct page *page;
  55
  56         if (buffer_dirty(bh))
  57                 goto nope;
  58         if (atomic_read(&bh->b_count) != 1)
  59                 goto nope;
  60         page = bh->b_page;
  61         if (!page)
  62                 goto nope;
  63         if (page->mapping)
  64                 goto nope;
  65
  66         /* OK, it's a truncated page */
  67         if (TestSetPageLocked(page))
  68                 goto nope;
  69
  70         page_cache_get(page);
  71         __brelse(bh);
  72         try_to_free_buffers(page);
  73         unlock_page(page);
  74         page_cache_release(page);
  75         return;
  76
  77 nope:
  78         __brelse(bh);
  79 }
  80
  81 /*
  82  * Try to acquire jbd_lock_bh_state() against the buffer, when j_list_lock is
  83  * held.  For ranking reasons we must trylock.  If we lose, schedule away and
  84  * return 0.  j_list_lock is dropped in this case.
  85  */
  86 static int inverted_lock(journal_t *journal, struct buffer_head *bh)
  87 {
  88         if (!jbd_trylock_bh_state(bh)) {
  89                 spin_unlock(&journal->j_list_lock);
  90                 schedule();
  91                 return 0;
  92         }
  93         return 1;
  94 }
  95
  96 /* Done it all: now write the commit record.  We should have
  97  * cleaned up our previous buffers by now, so if we are in abort
  98  * mode we can now just skip the rest of the journal write
  99  * entirely.
 100  *
 101  * Returns 1 if the journal needs to be aborted or 0 on success
 102  */
 103 static int journal_write_commit_record(journal_t *journal,
 104                                         transaction_t *commit_transaction)
 105 {
 106         struct journal_head *descriptor;
 107         struct buffer_head *bh;
 108         int i, ret;
 109         int barrier_done = 0;
 110
 111         if (is_journal_aborted(journal))
 112                 return 0;
 113
 114         descriptor = journal_get_descriptor_buffer(journal);
 115         if (!descriptor)
 116                 return 1;
 117
 118         bh = jh2bh(descriptor);
 119
 120         /* AKPM: buglet - add `i' to tmp! */
 121         for (i = 0; i < bh->b_size; i += 512) {
 122                 journal_header_t *tmp = (journal_header_t*)bh->b_data;
 123                 tmp->h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
 124                 tmp->h_blocktype = cpu_to_be32(JFS_COMMIT_BLOCK);
 125                 tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 126         }
 127
 128         JBUFFER_TRACE(descriptor, "write commit block");
 129         set_buffer_dirty(bh);
 130         if (journal->j_flags & JFS_BARRIER) {
 131                 set_buffer_ordered(bh);
 132                 barrier_done = 1;
 133         }
 134         ret = sync_dirty_buffer(bh);
 135         /* is it possible for another commit to fail at roughly
 136          * the same time as this one?  If so, we don't want to
 137          * trust the barrier flag in the super, but instead want
 138          * to remember if we sent a barrier request
 139          */
 140         if (ret == -EOPNOTSUPP && barrier_done) {
 141                 char b[BDEVNAME_SIZE];
 142
 143                 printk(KERN_WARNING
 144                         "JBD: barrier-based sync failed on %s - "
 145                         "disabling barriers\n",
 146                         bdevname(journal->j_dev, b));
 147                 spin_lock(&journal->j_state_lock);
 148                 journal->j_flags &= ~JFS_BARRIER;
 149                 spin_unlock(&journal->j_state_lock);
 150
 151                 /* And try again, without the barrier */
 152                 clear_buffer_ordered(bh);
 153                 set_buffer_uptodate(bh);
 154                 set_buffer_dirty(bh);
 155                 ret = sync_dirty_buffer(bh);
 156         }
 157         put_bh(bh);             /* One for getblk() */
 158         journal_put_journal_head(descriptor);
 159
 160         return (ret == -EIO);
 161 }
 162
 163 /*
 164  * journal_commit_transaction
 165  *
 166  * The primary function for committing a transaction to the log.  This
 167  * function is called by the journal thread to begin a complete commit.
 168  */
 169 void journal_commit_transaction(journal_t *journal)
 170 {
 171         transaction_t *commit_transaction;
 172         struct journal_head *jh, *new_jh, *descriptor;
 173         struct buffer_head **wbuf = journal->j_wbuf;
 174         int bufs;
 175         int flags;
 176         int err;
 177         unsigned long blocknr;
 178         char *tagp = NULL;
 179         journal_header_t *header;
 180         journal_block_tag_t *tag = NULL;
 181         int space_left = 0;
 182         int first_tag = 0;
 183         int tag_flag;
 184         int i;
 185
 186         /*
 187          * First job: lock down the current transaction and wait for
 188          * all outstanding updates to complete.
 189          */
 190
 191 #ifdef COMMIT_STATS
 192         spin_lock(&journal->j_list_lock);
 193         summarise_journal_usage(journal);
 194         spin_unlock(&journal->j_list_lock);
 195 #endif
 196
 197         /* Do we need to erase the effects of a prior journal_flush? */
 198         if (journal->j_flags & JFS_FLUSHED) {
 199                 jbd_debug(3, "super block updated\n");
 200                 journal_update_superblock(journal, 1);
 201         } else {
 202                 jbd_debug(3, "superblock not updated\n");
 203         }
 204
 205         J_ASSERT(journal->j_running_transaction != NULL);
 206         J_ASSERT(journal->j_committing_transaction == NULL);
 207
 208         commit_transaction = journal->j_running_transaction;
 209         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 210
 211         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 212                         commit_transaction->t_tid);
 213
 214         spin_lock(&journal->j_state_lock);
 215         commit_transaction->t_state = T_LOCKED;
 216
 217         spin_lock(&commit_transaction->t_handle_lock);
 218         while (commit_transaction->t_updates) {
 219                 DEFINE_WAIT(wait);
 220
 221                 prepare_to_wait(&journal->j_wait_updates, &wait,
 222                                         TASK_UNINTERRUPTIBLE);
 223                 if (commit_transaction->t_updates) {
 224                         spin_unlock(&commit_transaction->t_handle_lock);
 225                         spin_unlock(&journal->j_state_lock);
 226                         schedule();
 227                         spin_lock(&journal->j_state_lock);
 228                         spin_lock(&commit_transaction->t_handle_lock);
 229                 }
 230                 finish_wait(&journal->j_wait_updates, &wait);
 231         }
 232         spin_unlock(&commit_transaction->t_handle_lock);
 233
 234         J_ASSERT (commit_transaction->t_outstanding_credits <=
 235                         journal->j_max_transaction_buffers);
 236
 237         /*
 238          * First thing we are allowed to do is to discard any remaining
 239          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 240          * that there are no such buffers: if a large filesystem
 241          * operation like a truncate needs to split itself over multiple
 242          * transactions, then it may try to do a journal_restart() while
 243          * there are still BJ_Reserved buffers outstanding.  These must
 244          * be released cleanly from the current transaction.
 245          *
 246          * In this case, the filesystem must still reserve write access
 247          * again before modifying the buffer in the new transaction, but
 248          * we do not require it to remember exactly which old buffers it
 249          * has reserved.  This is consistent with the existing behaviour
 250          * that multiple journal_get_write_access() calls to the same
 251          * buffer are perfectly permissable.
 252          */
 253         while (commit_transaction->t_reserved_list) {
 254                 jh = commit_transaction->t_reserved_list;
 255                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 256                 /*
 257                  * A journal_get_undo_access()+journal_release_buffer() may
 258                  * leave undo-committed data.
 259                  */
 260                 if (jh->b_committed_data) {
 261                         struct buffer_head *bh = jh2bh(jh);
 262
 263                         jbd_lock_bh_state(bh);
 264                         kfree(jh->b_committed_data);
 265                         jh->b_committed_data = NULL;
 266                         jbd_unlock_bh_state(bh);
 267                 }
 268                 journal_refile_buffer(journal, jh);
 269         }
 270
 271         /*
 272          * Now try to drop any written-back buffers from the journal's
 273          * checkpoint lists.  We do this *before* commit because it potentially
 274          * frees some memory
 275          */
 276         spin_lock(&journal->j_list_lock);
 277         __journal_clean_checkpoint_list(journal);
 278         spin_unlock(&journal->j_list_lock);
 279
 280         jbd_debug (3, "JBD: commit phase 1\n");
 281
 282         /*
 283          * Switch to a new revoke table.
 284          */
 285         journal_switch_revoke_table(journal);
 286
 287         commit_transaction->t_state = T_FLUSH;
 288         journal->j_committing_transaction = commit_transaction;
 289         journal->j_running_transaction = NULL;
 290         commit_transaction->t_log_start = journal->j_head;
 291         wake_up(&journal->j_wait_transaction_locked);
 292         spin_unlock(&journal->j_state_lock);
 293
 294         jbd_debug (3, "JBD: commit phase 2\n");
 295
 296         /*
 297          * First, drop modified flag: all accesses to the buffers
 298          * will be tracked for a new trasaction only -bzzz
 299          */
 300         spin_lock(&journal->j_list_lock);
 301         if (commit_transaction->t_buffers) {
 302                 new_jh = jh = commit_transaction->t_buffers->b_tnext;
 303                 do {
 304                         J_ASSERT_JH(new_jh, new_jh->b_modified == 1 ||
 305                                         new_jh->b_modified == 0);
 306                         new_jh->b_modified = 0;
 307                         new_jh = new_jh->b_tnext;
 308                 } while (new_jh != jh);
 309         }
 310         spin_unlock(&journal->j_list_lock);
 311
 312         /*
 313          * Now start flushing things to disk, in the order they appear
 314          * on the transaction lists.  Data blocks go first.
 315          */
 316
 317         err = 0;
 318         /*
 319          * Whenever we unlock the journal and sleep, things can get added
 320          * onto ->t_sync_datalist, so we have to keep looping back to
 321          * write_out_data until we *know* that the list is empty.
 322          */
 323         bufs = 0;
 324         /*
 325          * Cleanup any flushed data buffers from the data list.  Even in
 326          * abort mode, we want to flush this out as soon as possible.
 327          */
 328 write_out_data:
 329         cond_resched();
 330         spin_lock(&journal->j_list_lock);
 331
 332         while (commit_transaction->t_sync_datalist) {
 333                 struct buffer_head *bh;
 334
 335                 jh = commit_transaction->t_sync_datalist;
 336                 commit_transaction->t_sync_datalist = jh->b_tnext;
 337                 bh = jh2bh(jh);
 338                 if (buffer_locked(bh)) {
 339                         BUFFER_TRACE(bh, "locked");
 340                         if (!inverted_lock(journal, bh))
 341                                 goto write_out_data;
 342                         __journal_temp_unlink_buffer(jh);
 343                         __journal_file_buffer(jh, commit_transaction,
 344                                                 BJ_Locked);
 345                         jbd_unlock_bh_state(bh);
 346                         if (lock_need_resched(&journal->j_list_lock)) {
 347                                 spin_unlock(&journal->j_list_lock);
 348                                 goto write_out_data;
 349                         }
 350                 } else {
 351                         if (buffer_dirty(bh)) {
 352                                 BUFFER_TRACE(bh, "start journal writeout");
 353                                 get_bh(bh);
 354                                 wbuf[bufs++] = bh;
 355                                 if (bufs == journal->j_wbufsize) {
 356                                         jbd_debug(2, "submit %d writes\n",
 357                                                         bufs);
 358                                         spin_unlock(&journal->j_list_lock);
 359                                         ll_rw_block(SWRITE, bufs, wbuf);
 360                                         journal_brelse_array(wbuf, bufs);
 361                                         bufs = 0;
 362                                         goto write_out_data;
 363                                 }
 364                         } else {
 365                                 BUFFER_TRACE(bh, "writeout complete: unfile");
 366                                 if (!inverted_lock(journal, bh))
 367                                         goto write_out_data;
 368                                 __journal_unfile_buffer(jh);
 369                                 jbd_unlock_bh_state(bh);
 370                                 journal_remove_journal_head(bh);
 371                                 put_bh(bh);
 372                                 if (lock_need_resched(&journal->j_list_lock)) {
 373                                         spin_unlock(&journal->j_list_lock);
 374                                         goto write_out_data;
 375                                 }
 376                         }
 377                 }
 378         }
 379
 380         if (bufs) {
 381                 spin_unlock(&journal->j_list_lock);
 382                 ll_rw_block(SWRITE, bufs, wbuf);
 383                 journal_brelse_array(wbuf, bufs);
 384                 spin_lock(&journal->j_list_lock);
 385         }
 386
 387         /*
 388          * Wait for all previously submitted IO to complete.
 389          */
 390         while (commit_transaction->t_locked_list) {
 391                 struct buffer_head *bh;
 392
 393                 jh = commit_transaction->t_locked_list->b_tprev;
 394                 bh = jh2bh(jh);
 395                 get_bh(bh);
 396                 if (buffer_locked(bh)) {
 397                         spin_unlock(&journal->j_list_lock);
 398                         wait_on_buffer(bh);
 399                         if (unlikely(!buffer_uptodate(bh)))
 400                                 err = -EIO;
 401                         spin_lock(&journal->j_list_lock);
 402                 }
 403                 if (!inverted_lock(journal, bh)) {
 404                         put_bh(bh);
 405                         spin_lock(&journal->j_list_lock);
 406                         continue;
 407                 }
 408                 if (buffer_jbd(bh) && jh->b_jlist == BJ_Locked) {
 409                         __journal_unfile_buffer(jh);
 410                         jbd_unlock_bh_state(bh);
 411                         journal_remove_journal_head(bh);
 412                         put_bh(bh);
 413                 } else {
 414                         jbd_unlock_bh_state(bh);
 415                 }
 416                 put_bh(bh);
 417                 cond_resched_lock(&journal->j_list_lock);
 418         }
 419         spin_unlock(&journal->j_list_lock);
 420
 421         if (err)
 422                 __journal_abort_hard(journal);
 423
 424         journal_write_revoke_records(journal, commit_transaction);
 425
 426         jbd_debug(3, "JBD: commit phase 2\n");
 427
 428         /*
 429          * If we found any dirty or locked buffers, then we should have
 430          * looped back up to the write_out_data label.  If there weren't
 431          * any then journal_clean_data_list should have wiped the list
 432          * clean by now, so check that it is in fact empty.
 433          */
 434         J_ASSERT (commit_transaction->t_sync_datalist == NULL);
 435
 436         jbd_debug (3, "JBD: commit phase 3\n");
 437
 438         /*
 439          * Way to go: we have now written out all of the data for a
 440          * transaction!  Now comes the tricky part: we need to write out
 441          * metadata.  Loop over the transaction's entire buffer list:
 442          */
 443         commit_transaction->t_state = T_COMMIT;
 444
 445         descriptor = NULL;
 446         bufs = 0;
 447         while (commit_transaction->t_buffers) {
 448
 449                 /* Find the next buffer to be journaled... */
 450
 451                 jh = commit_transaction->t_buffers;
 452
 453                 /* If we're in abort mode, we just un-journal the buffer and
 454                    release it for background writing. */
 455
 456                 if (is_journal_aborted(journal)) {
 457                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 458                         journal_refile_buffer(journal, jh);
 459                         /* If that was the last one, we need to clean up
 460                          * any descriptor buffers which may have been
 461                          * already allocated, even if we are now
 462                          * aborting. */
 463                         if (!commit_transaction->t_buffers)
 464                                 goto start_journal_io;
 465                         continue;
 466                 }
 467
 468                 /* Make sure we have a descriptor block in which to
 469                    record the metadata buffer. */
 470
 471                 if (!descriptor) {
 472                         struct buffer_head *bh;
 473
 474                         J_ASSERT (bufs == 0);
 475
 476                         jbd_debug(4, "JBD: get descriptor\n");
 477
 478                         descriptor = journal_get_descriptor_buffer(journal);
 479                         if (!descriptor) {
 480                                 __journal_abort_hard(journal);
 481                                 continue;
 482                         }
 483
 484                         bh = jh2bh(descriptor);
 485                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 486                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 487                         header = (journal_header_t *)&bh->b_data[0];
 488                         header->h_magic     = cpu_to_be32(JFS_MAGIC_NUMBER);
 489                         header->h_blocktype = cpu_to_be32(JFS_DESCRIPTOR_BLOCK);
 490                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 491
 492                         tagp = &bh->b_data[sizeof(journal_header_t)];
 493                         space_left = bh->b_size - sizeof(journal_header_t);
 494                         first_tag = 1;
 495                         set_buffer_jwrite(bh);
 496                         set_buffer_dirty(bh);
 497                         wbuf[bufs++] = bh;
 498
 499                         /* Record it so that we can wait for IO
 500                            completion later */
 501                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 502                         journal_file_buffer(descriptor, commit_transaction,
 503                                         BJ_LogCtl);
 504                 }
 505
 506                 /* Where is the buffer to be written? */
 507
 508                 err = journal_next_log_block(journal, &blocknr);
 509                 /* If the block mapping failed, just abandon the buffer
 510                    and repeat this loop: we'll fall into the
 511                    refile-on-abort condition above. */
 512                 if (err) {
 513                         __journal_abort_hard(journal);
 514                         continue;
 515                 }
 516
 517                 /*
 518                  * start_this_handle() uses t_outstanding_credits to determine
 519                  * the free space in the log, but this counter is changed
 520                  * by journal_next_log_block() also.
 521                  */
 522                 commit_transaction->t_outstanding_credits--;
 523
 524                 /* Bump b_count to prevent truncate from stumbling over
 525                    the shadowed buffer!  @@@ This can go if we ever get
 526                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 527                 atomic_inc(&jh2bh(jh)->b_count);
 528
 529                 /* Make a temporary IO buffer with which to write it out
 530                    (this will requeue both the metadata buffer and the
 531                    temporary IO buffer). new_bh goes on BJ_IO*/
 532
 533                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 534                 /*
 535                  * akpm: journal_write_metadata_buffer() sets
 536                  * new_bh->b_transaction to commit_transaction.
 537                  * We need to clean this up before we release new_bh
 538                  * (which is of type BJ_IO)
 539                  */
 540                 JBUFFER_TRACE(jh, "ph3: write metadata");
 541                 flags = journal_write_metadata_buffer(commit_transaction,
 542                                                       jh, &new_jh, blocknr);
 543                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 544                 wbuf[bufs++] = jh2bh(new_jh);
 545
 546                 /* Record the new block's tag in the current descriptor
 547                    buffer */
 548
 549                 tag_flag = 0;
 550                 if (flags & 1)
 551                         tag_flag |= JFS_FLAG_ESCAPE;
 552                 if (!first_tag)
 553                         tag_flag |= JFS_FLAG_SAME_UUID;
 554
 555                 tag = (journal_block_tag_t *) tagp;
 556                 tag->t_blocknr = cpu_to_be32(jh2bh(jh)->b_blocknr);
 557                 tag->t_flags = cpu_to_be32(tag_flag);
 558                 tagp += sizeof(journal_block_tag_t);
 559                 space_left -= sizeof(journal_block_tag_t);
 560
 561                 if (first_tag) {
 562                         memcpy (tagp, journal->j_uuid, 16);
 563                         tagp += 16;
 564                         space_left -= 16;
 565                         first_tag = 0;
 566                 }
 567
 568                 /* If there's no more to do, or if the descriptor is full,
 569                    let the IO rip! */
 570
 571                 if (bufs == journal->j_wbufsize ||
 572                     commit_transaction->t_buffers == NULL ||
 573                     space_left < sizeof(journal_block_tag_t) + 16) {
 574
 575                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 576
 577                         /* Write an end-of-descriptor marker before
 578                            submitting the IOs.  "tag" still points to
 579                            the last tag we set up. */
 580
 581                         tag->t_flags |= cpu_to_be32(JFS_FLAG_LAST_TAG);
 582
 583 start_journal_io:
 584                         for (i = 0; i < bufs; i++) {
 585                                 struct buffer_head *bh = wbuf[i];
 586                                 lock_buffer(bh);
 587                                 clear_buffer_dirty(bh);
 588                                 set_buffer_uptodate(bh);
 589                                 bh->b_end_io = journal_end_buffer_io_sync;
 590                                 submit_bh(WRITE, bh);
 591                         }
 592                         cond_resched();
 593
 594                         /* Force a new descriptor to be generated next
 595                            time round the loop. */
 596                         descriptor = NULL;
 597                         bufs = 0;
 598                 }
 599         }
 600
 601         /* Lo and behold: we have just managed to send a transaction to
 602            the log.  Before we can commit it, wait for the IO so far to
 603            complete.  Control buffers being written are on the
 604            transaction's t_log_list queue, and metadata buffers are on
 605            the t_iobuf_list queue.
 606
 607            Wait for the buffers in reverse order.  That way we are
 608            less likely to be woken up until all IOs have completed, and
 609            so we incur less scheduling load.
 610         */
 611
 612         jbd_debug(3, "JBD: commit phase 4\n");
 613
 614         /*
 615          * akpm: these are BJ_IO, and j_list_lock is not needed.
 616          * See __journal_try_to_free_buffer.
 617          */
 618 wait_for_iobuf:
 619         while (commit_transaction->t_iobuf_list != NULL) {
 620                 struct buffer_head *bh;
 621
 622                 jh = commit_transaction->t_iobuf_list->b_tprev;
 623                 bh = jh2bh(jh);
 624                 if (buffer_locked(bh)) {
 625                         wait_on_buffer(bh);
 626                         goto wait_for_iobuf;
 627                 }
 628                 if (cond_resched())
 629                         goto wait_for_iobuf;
 630
 631                 if (unlikely(!buffer_uptodate(bh)))
 632                         err = -EIO;
 633
 634                 clear_buffer_jwrite(bh);
 635
 636                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 637                 journal_unfile_buffer(journal, jh);
 638
 639                 /*
 640                  * ->t_iobuf_list should contain only dummy buffer_heads
 641                  * which were created by journal_write_metadata_buffer().
 642                  */
 643                 BUFFER_TRACE(bh, "dumping temporary bh");
 644                 journal_put_journal_head(jh);
 645                 __brelse(bh);
 646                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 647                 free_buffer_head(bh);
 648
 649                 /* We also have to unlock and free the corresponding
 650                    shadowed buffer */
 651                 jh = commit_transaction->t_shadow_list->b_tprev;
 652                 bh = jh2bh(jh);
 653                 clear_bit(BH_JWrite, &bh->b_state);
 654                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 655
 656                 /* The metadata is now released for reuse, but we need
 657                    to remember it against this transaction so that when
 658                    we finally commit, we can do any checkpointing
 659                    required. */
 660                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 661                 journal_file_buffer(jh, commit_transaction, BJ_Forget);
 662                 /* Wake up any transactions which were waiting for this
 663                    IO to complete */
 664                 wake_up_bit(&bh->b_state, BH_Unshadow);
 665                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 666                 __brelse(bh);
 667         }
 668
 669         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 670
 671         jbd_debug(3, "JBD: commit phase 5\n");
 672
 673         /* Here we wait for the revoke record and descriptor record buffers */
 674  wait_for_ctlbuf:
 675         while (commit_transaction->t_log_list != NULL) {
 676                 struct buffer_head *bh;
 677
 678                 jh = commit_transaction->t_log_list->b_tprev;
 679                 bh = jh2bh(jh);
 680                 if (buffer_locked(bh)) {
 681                         wait_on_buffer(bh);
 682                         goto wait_for_ctlbuf;
 683                 }
 684                 if (cond_resched())
 685                         goto wait_for_ctlbuf;
 686
 687                 if (unlikely(!buffer_uptodate(bh)))
 688                         err = -EIO;
 689
 690                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 691                 clear_buffer_jwrite(bh);
 692                 journal_unfile_buffer(journal, jh);
 693                 journal_put_journal_head(jh);
 694                 __brelse(bh);           /* One for getblk */
 695                 /* AKPM: bforget here */
 696         }
 697
 698         jbd_debug(3, "JBD: commit phase 6\n");
 699
 700         if (journal_write_commit_record(journal, commit_transaction))
 701                 err = -EIO;
 702
 703         if (err)
 704                 __journal_abort_hard(journal);
 705
 706         /* End of a transaction!  Finally, we can do checkpoint
 707            processing: any buffers committed as a result of this
 708            transaction can be removed from any checkpoint list it was on
 709            before. */
 710
 711         jbd_debug(3, "JBD: commit phase 7\n");
 712
 713         J_ASSERT(commit_transaction->t_sync_datalist == NULL);
 714         J_ASSERT(commit_transaction->t_buffers == NULL);
 715         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 716         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 717         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 718         J_ASSERT(commit_transaction->t_log_list == NULL);
 719
 720 restart_loop:
 721         /*
 722          * As there are other places (journal_unmap_buffer()) adding buffers
 723          * to this list we have to be careful and hold the j_list_lock.
 724          */
 725         spin_lock(&journal->j_list_lock);
 726         while (commit_transaction->t_forget) {
 727                 transaction_t *cp_transaction;
 728                 struct buffer_head *bh;
 729
 730                 jh = commit_transaction->t_forget;
 731                 spin_unlock(&journal->j_list_lock);
 732                 bh = jh2bh(jh);
 733                 jbd_lock_bh_state(bh);
 734                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 735                         jh->b_transaction == journal->j_running_transaction);
 736
 737                 /*
 738                  * If there is undo-protected committed data against
 739                  * this buffer, then we can remove it now.  If it is a
 740                  * buffer needing such protection, the old frozen_data
 741                  * field now points to a committed version of the
 742                  * buffer, so rotate that field to the new committed
 743                  * data.
 744                  *
 745                  * Otherwise, we can just throw away the frozen data now.
 746                  */
 747                 if (jh->b_committed_data) {
 748                         kfree(jh->b_committed_data);
 749                         jh->b_committed_data = NULL;
 750                         if (jh->b_frozen_data) {
 751                                 jh->b_committed_data = jh->b_frozen_data;
 752                                 jh->b_frozen_data = NULL;
 753                         }
 754                 } else if (jh->b_frozen_data) {
 755                         kfree(jh->b_frozen_data);
 756                         jh->b_frozen_data = NULL;
 757                 }
 758
 759                 spin_lock(&journal->j_list_lock);
 760                 cp_transaction = jh->b_cp_transaction;
 761                 if (cp_transaction) {
 762                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 763                         __journal_remove_checkpoint(jh);
 764                 }
 765
 766                 /* Only re-checkpoint the buffer_head if it is marked
 767                  * dirty.  If the buffer was added to the BJ_Forget list
 768                  * by journal_forget, it may no longer be dirty and
 769                  * there's no point in keeping a checkpoint record for
 770                  * it. */
 771
 772                 /* A buffer which has been freed while still being
 773                  * journaled by a previous transaction may end up still
 774                  * being dirty here, but we want to avoid writing back
 775                  * that buffer in the future now that the last use has
 776                  * been committed.  That's not only a performance gain,
 777                  * it also stops aliasing problems if the buffer is left
 778                  * behind for writeback and gets reallocated for another
 779                  * use in a different page. */
 780                 if (buffer_freed(bh)) {
 781                         clear_buffer_freed(bh);
 782                         clear_buffer_jbddirty(bh);
 783                 }
 784
 785                 if (buffer_jbddirty(bh)) {
 786                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 787                         __journal_insert_checkpoint(jh, commit_transaction);
 788                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 789                         __journal_refile_buffer(jh);
 790                         jbd_unlock_bh_state(bh);
 791                 } else {
 792                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 793                         J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
 794                         __journal_unfile_buffer(jh);
 795                         jbd_unlock_bh_state(bh);
 796                         journal_remove_journal_head(bh);  /* needs a brelse */
 797                         release_buffer_page(bh);
 798                 }
 799                 cond_resched_lock(&journal->j_list_lock);
 800         }
 801         spin_unlock(&journal->j_list_lock);
 802         /*
 803          * This is a bit sleazy.  We borrow j_list_lock to protect
 804          * journal->j_committing_transaction in __journal_remove_checkpoint.
 805          * Really, __journal_remove_checkpoint should be using j_state_lock but
 806          * it's a bit hassle to hold that across __journal_remove_checkpoint
 807          */
 808         spin_lock(&journal->j_state_lock);
 809         spin_lock(&journal->j_list_lock);
 810         /*
 811          * Now recheck if some buffers did not get attached to the transaction
 812          * while the lock was dropped...
 813          */
 814         if (commit_transaction->t_forget) {
 815                 spin_unlock(&journal->j_list_lock);
 816                 spin_unlock(&journal->j_state_lock);
 817                 goto restart_loop;
 818         }
 819
 820         /* Done with this transaction! */
 821
 822         jbd_debug(3, "JBD: commit phase 8\n");
 823
 824         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 825
 826         commit_transaction->t_state = T_FINISHED;
 827         J_ASSERT(commit_transaction == journal->j_committing_transaction);
 828         journal->j_commit_sequence = commit_transaction->t_tid;
 829         journal->j_committing_transaction = NULL;
 830         spin_unlock(&journal->j_state_lock);
 831
 832         if (commit_transaction->t_checkpoint_list == NULL) {
 833                 __journal_drop_transaction(journal, commit_transaction);
 834         } else {
 835                 if (journal->j_checkpoint_transactions == NULL) {
 836                         journal->j_checkpoint_transactions = commit_transaction;
 837                         commit_transaction->t_cpnext = commit_transaction;
 838                         commit_transaction->t_cpprev = commit_transaction;
 839                 } else {
 840                         commit_transaction->t_cpnext =
 841                                 journal->j_checkpoint_transactions;
 842                         commit_transaction->t_cpprev =
 843                                 commit_transaction->t_cpnext->t_cpprev;
 844                         commit_transaction->t_cpnext->t_cpprev =
 845                                 commit_transaction;
 846                         commit_transaction->t_cpprev->t_cpnext =
 847                                 commit_transaction;
 848                 }
 849         }
 850         spin_unlock(&journal->j_list_lock);
 851
 852         jbd_debug(1, "JBD: commit %d complete, head %d\n",
 853                   journal->j_commit_sequence, journal->j_tail_sequence);
 854
 855         wake_up(&journal->j_wait_done_commit);
 856 }