fs/jbd/commit.c

   1 /*
   2  * linux/fs/jbd/commit.c
   3  *
   4  * Written by Stephen C. Tweedie <[email protected]>, 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/mm.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/bio.h>
  23 #include <linux/blkdev.h>
  24 #include <trace/events/jbd.h>
  25
  26 /*
  27  * Default IO end handler for temporary BJ_IO buffer_heads.
  28  */
  29 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
  30 {
  31         BUFFER_TRACE(bh, "");
  32         if (uptodate)
  33                 set_buffer_uptodate(bh);
  34         else
  35                 clear_buffer_uptodate(bh);
  36         unlock_buffer(bh);
  37 }
  38
  39 /*
  40  * When an ext3-ordered file is truncated, it is possible that many pages are
  41  * not successfully freed, because they are attached to a committing transaction.
  42  * After the transaction commits, these pages are left on the LRU, with no
  43  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
  44  * by the VM, but their apparent absence upsets the VM accounting, and it makes
  45  * the numbers in /proc/meminfo look odd.
  46  *
  47  * So here, we have a buffer which has just come off the forget list.  Look to
  48  * see if we can strip all buffers from the backing page.
  49  *
  50  * Called under journal->j_list_lock.  The caller provided us with a ref
  51  * against the buffer, and we drop that here.
  52  */
  53 static void release_buffer_page(struct buffer_head *bh)
  54 {
  55         struct page *page;
  56
  57         if (buffer_dirty(bh))
  58                 goto nope;
  59         if (atomic_read(&bh->b_count) != 1)
  60                 goto nope;
  61         page = bh->b_page;
  62         if (!page)
  63                 goto nope;
  64         if (page->mapping)
  65                 goto nope;
  66
  67         /* OK, it's a truncated page */
  68         if (!trylock_page(page))
  69                 goto nope;
  70
  71         page_cache_get(page);
  72         __brelse(bh);
  73         try_to_free_buffers(page);
  74         unlock_page(page);
  75         page_cache_release(page);
  76         return;
  77
  78 nope:
  79         __brelse(bh);
  80 }
  81
  82 /*
  83  * Decrement reference counter for data buffer. If it has been marked
  84  * 'BH_Freed', release it and the page to which it belongs if possible.
  85  */
  86 static void release_data_buffer(struct buffer_head *bh)
  87 {
  88         if (buffer_freed(bh)) {
  89                 clear_buffer_freed(bh);
  90                 release_buffer_page(bh);
  91         } else
  92                 put_bh(bh);
  93 }
  94
  95 /*
  96  * Try to acquire jbd_lock_bh_state() against the buffer, when j_list_lock is
  97  * held.  For ranking reasons we must trylock.  If we lose, schedule away and
  98  * return 0.  j_list_lock is dropped in this case.
  99  */
 100 static int inverted_lock(journal_t *journal, struct buffer_head *bh)
 101 {
 102         if (!jbd_trylock_bh_state(bh)) {
 103                 spin_unlock(&journal->j_list_lock);
 104                 schedule();
 105                 return 0;
 106         }
 107         return 1;
 108 }
 109
 110 /* Done it all: now write the commit record.  We should have
 111  * cleaned up our previous buffers by now, so if we are in abort
 112  * mode we can now just skip the rest of the journal write
 113  * entirely.
 114  *
 115  * Returns 1 if the journal needs to be aborted or 0 on success
 116  */
 117 static int journal_write_commit_record(journal_t *journal,
 118                                         transaction_t *commit_transaction)
 119 {
 120         struct journal_head *descriptor;
 121         struct buffer_head *bh;
 122         journal_header_t *header;
 123         int ret;
 124
 125         if (is_journal_aborted(journal))
 126                 return 0;
 127
 128         descriptor = journal_get_descriptor_buffer(journal);
 129         if (!descriptor)
 130                 return 1;
 131
 132         bh = jh2bh(descriptor);
 133
 134         header = (journal_header_t *)(bh->b_data);
 135         header->h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
 136         header->h_blocktype = cpu_to_be32(JFS_COMMIT_BLOCK);
 137         header->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 138
 139         JBUFFER_TRACE(descriptor, "write commit block");
 140         set_buffer_dirty(bh);
 141
 142         if (journal->j_flags & JFS_BARRIER)
 143                 ret = __sync_dirty_buffer(bh, WRITE_SYNC | WRITE_FLUSH_FUA);
 144         else
 145                 ret = sync_dirty_buffer(bh);
 146
 147         put_bh(bh);             /* One for getblk() */
 148         journal_put_journal_head(descriptor);
 149
 150         return (ret == -EIO);
 151 }
 152
 153 static void journal_do_submit_data(struct buffer_head **wbuf, int bufs,
 154                                    int write_op)
 155 {
 156         int i;
 157
 158         for (i = 0; i < bufs; i++) {
 159                 wbuf[i]->b_end_io = end_buffer_write_sync;
 160                 /* We use-up our safety reference in submit_bh() */
 161                 submit_bh(write_op, wbuf[i]);
 162         }
 163 }
 164
 165 /*
 166  *  Submit all the data buffers to disk
 167  */
 168 static int journal_submit_data_buffers(journal_t *journal,
 169                                        transaction_t *commit_transaction,
 170                                        int write_op)
 171 {
 172         struct journal_head *jh;
 173         struct buffer_head *bh;
 174         int locked;
 175         int bufs = 0;
 176         struct buffer_head **wbuf = journal->j_wbuf;
 177         int err = 0;
 178
 179         /*
 180          * Whenever we unlock the journal and sleep, things can get added
 181          * onto ->t_sync_datalist, so we have to keep looping back to
 182          * write_out_data until we *know* that the list is empty.
 183          *
 184          * Cleanup any flushed data buffers from the data list.  Even in
 185          * abort mode, we want to flush this out as soon as possible.
 186          */
 187 write_out_data:
 188         cond_resched();
 189         spin_lock(&journal->j_list_lock);
 190
 191         while (commit_transaction->t_sync_datalist) {
 192                 jh = commit_transaction->t_sync_datalist;
 193                 bh = jh2bh(jh);
 194                 locked = 0;
 195
 196                 /* Get reference just to make sure buffer does not disappear
 197                  * when we are forced to drop various locks */
 198                 get_bh(bh);
 199                 /* If the buffer is dirty, we need to submit IO and hence
 200                  * we need the buffer lock. We try to lock the buffer without
 201                  * blocking. If we fail, we need to drop j_list_lock and do
 202                  * blocking lock_buffer().
 203                  */
 204                 if (buffer_dirty(bh)) {
 205                         if (!trylock_buffer(bh)) {
 206                                 BUFFER_TRACE(bh, "needs blocking lock");
 207                                 spin_unlock(&journal->j_list_lock);
 208                                 trace_jbd_do_submit_data(journal,
 209                                                      commit_transaction);
 210                                 /* Write out all data to prevent deadlocks */
 211                                 journal_do_submit_data(wbuf, bufs, write_op);
 212                                 bufs = 0;
 213                                 lock_buffer(bh);
 214                                 spin_lock(&journal->j_list_lock);
 215                         }
 216                         locked = 1;
 217                 }
 218                 /* We have to get bh_state lock. Again out of order, sigh. */
 219                 if (!inverted_lock(journal, bh)) {
 220                         jbd_lock_bh_state(bh);
 221                         spin_lock(&journal->j_list_lock);
 222                 }
 223                 /* Someone already cleaned up the buffer? */
 224                 if (!buffer_jbd(bh) || bh2jh(bh) != jh
 225                         || jh->b_transaction != commit_transaction
 226                         || jh->b_jlist != BJ_SyncData) {
 227                         jbd_unlock_bh_state(bh);
 228                         if (locked)
 229                                 unlock_buffer(bh);
 230                         BUFFER_TRACE(bh, "already cleaned up");
 231                         release_data_buffer(bh);
 232                         continue;
 233                 }
 234                 if (locked && test_clear_buffer_dirty(bh)) {
 235                         BUFFER_TRACE(bh, "needs writeout, adding to array");
 236                         wbuf[bufs++] = bh;
 237                         __journal_file_buffer(jh, commit_transaction,
 238                                                 BJ_Locked);
 239                         jbd_unlock_bh_state(bh);
 240                         if (bufs == journal->j_wbufsize) {
 241                                 spin_unlock(&journal->j_list_lock);
 242                                 trace_jbd_do_submit_data(journal,
 243                                                      commit_transaction);
 244                                 journal_do_submit_data(wbuf, bufs, write_op);
 245                                 bufs = 0;
 246                                 goto write_out_data;
 247                         }
 248                 } else if (!locked && buffer_locked(bh)) {
 249                         __journal_file_buffer(jh, commit_transaction,
 250                                                 BJ_Locked);
 251                         jbd_unlock_bh_state(bh);
 252                         put_bh(bh);
 253                 } else {
 254                         BUFFER_TRACE(bh, "writeout complete: unfile");
 255                         if (unlikely(!buffer_uptodate(bh)))
 256                                 err = -EIO;
 257                         __journal_unfile_buffer(jh);
 258                         jbd_unlock_bh_state(bh);
 259                         if (locked)
 260                                 unlock_buffer(bh);
 261                         release_data_buffer(bh);
 262                 }
 263
 264                 if (need_resched() || spin_needbreak(&journal->j_list_lock)) {
 265                         spin_unlock(&journal->j_list_lock);
 266                         goto write_out_data;
 267                 }
 268         }
 269         spin_unlock(&journal->j_list_lock);
 270         trace_jbd_do_submit_data(journal, commit_transaction);
 271         journal_do_submit_data(wbuf, bufs, write_op);
 272
 273         return err;
 274 }
 275
 276 /*
 277  * journal_commit_transaction
 278  *
 279  * The primary function for committing a transaction to the log.  This
 280  * function is called by the journal thread to begin a complete commit.
 281  */
 282 void journal_commit_transaction(journal_t *journal)
 283 {
 284         transaction_t *commit_transaction;
 285         struct journal_head *jh, *new_jh, *descriptor;
 286         struct buffer_head **wbuf = journal->j_wbuf;
 287         int bufs;
 288         int flags;
 289         int err;
 290         unsigned int blocknr;
 291         ktime_t start_time;
 292         u64 commit_time;
 293         char *tagp = NULL;
 294         journal_header_t *header;
 295         journal_block_tag_t *tag = NULL;
 296         int space_left = 0;
 297         int first_tag = 0;
 298         int tag_flag;
 299         int i;
 300         struct blk_plug plug;
 301         int write_op = WRITE;
 302
 303         /*
 304          * First job: lock down the current transaction and wait for
 305          * all outstanding updates to complete.
 306          */
 307
 308         /* Do we need to erase the effects of a prior journal_flush? */
 309         if (journal->j_flags & JFS_FLUSHED) {
 310                 jbd_debug(3, "super block updated\n");
 311                 mutex_lock(&journal->j_checkpoint_mutex);
 312                 /*
 313                  * We hold j_checkpoint_mutex so tail cannot change under us.
 314                  * We don't need any special data guarantees for writing sb
 315                  * since journal is empty and it is ok for write to be
 316                  * flushed only with transaction commit.
 317                  */
 318                 journal_update_sb_log_tail(journal, journal->j_tail_sequence,
 319                                            journal->j_tail, WRITE_SYNC);
 320                 mutex_unlock(&journal->j_checkpoint_mutex);
 321         } else {
 322                 jbd_debug(3, "superblock not updated\n");
 323         }
 324
 325         J_ASSERT(journal->j_running_transaction != NULL);
 326         J_ASSERT(journal->j_committing_transaction == NULL);
 327
 328         commit_transaction = journal->j_running_transaction;
 329         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 330
 331         trace_jbd_start_commit(journal, commit_transaction);
 332         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 333                         commit_transaction->t_tid);
 334
 335         spin_lock(&journal->j_state_lock);
 336         commit_transaction->t_state = T_LOCKED;
 337
 338         trace_jbd_commit_locking(journal, commit_transaction);
 339         spin_lock(&commit_transaction->t_handle_lock);
 340         while (commit_transaction->t_updates) {
 341                 DEFINE_WAIT(wait);
 342
 343                 prepare_to_wait(&journal->j_wait_updates, &wait,
 344                                         TASK_UNINTERRUPTIBLE);
 345                 if (commit_transaction->t_updates) {
 346                         spin_unlock(&commit_transaction->t_handle_lock);
 347                         spin_unlock(&journal->j_state_lock);
 348                         schedule();
 349                         spin_lock(&journal->j_state_lock);
 350                         spin_lock(&commit_transaction->t_handle_lock);
 351                 }
 352                 finish_wait(&journal->j_wait_updates, &wait);
 353         }
 354         spin_unlock(&commit_transaction->t_handle_lock);
 355
 356         J_ASSERT (commit_transaction->t_outstanding_credits <=
 357                         journal->j_max_transaction_buffers);
 358
 359         /*
 360          * First thing we are allowed to do is to discard any remaining
 361          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 362          * that there are no such buffers: if a large filesystem
 363          * operation like a truncate needs to split itself over multiple
 364          * transactions, then it may try to do a journal_restart() while
 365          * there are still BJ_Reserved buffers outstanding.  These must
 366          * be released cleanly from the current transaction.
 367          *
 368          * In this case, the filesystem must still reserve write access
 369          * again before modifying the buffer in the new transaction, but
 370          * we do not require it to remember exactly which old buffers it
 371          * has reserved.  This is consistent with the existing behaviour
 372          * that multiple journal_get_write_access() calls to the same
 373          * buffer are perfectly permissible.
 374          */
 375         while (commit_transaction->t_reserved_list) {
 376                 jh = commit_transaction->t_reserved_list;
 377                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 378                 /*
 379                  * A journal_get_undo_access()+journal_release_buffer() may
 380                  * leave undo-committed data.
 381                  */
 382                 if (jh->b_committed_data) {
 383                         struct buffer_head *bh = jh2bh(jh);
 384
 385                         jbd_lock_bh_state(bh);
 386                         jbd_free(jh->b_committed_data, bh->b_size);
 387                         jh->b_committed_data = NULL;
 388                         jbd_unlock_bh_state(bh);
 389                 }
 390                 journal_refile_buffer(journal, jh);
 391         }
 392
 393         /*
 394          * Now try to drop any written-back buffers from the journal's
 395          * checkpoint lists.  We do this *before* commit because it potentially
 396          * frees some memory
 397          */
 398         spin_lock(&journal->j_list_lock);
 399         __journal_clean_checkpoint_list(journal);
 400         spin_unlock(&journal->j_list_lock);
 401
 402         jbd_debug (3, "JBD: commit phase 1\n");
 403
 404         /*
 405          * Clear revoked flag to reflect there is no revoked buffers
 406          * in the next transaction which is going to be started.
 407          */
 408         journal_clear_buffer_revoked_flags(journal);
 409
 410         /*
 411          * Switch to a new revoke table.
 412          */
 413         journal_switch_revoke_table(journal);
 414
 415         trace_jbd_commit_flushing(journal, commit_transaction);
 416         commit_transaction->t_state = T_FLUSH;
 417         journal->j_committing_transaction = commit_transaction;
 418         journal->j_running_transaction = NULL;
 419         start_time = ktime_get();
 420         commit_transaction->t_log_start = journal->j_head;
 421         wake_up(&journal->j_wait_transaction_locked);
 422         spin_unlock(&journal->j_state_lock);
 423
 424         jbd_debug (3, "JBD: commit phase 2\n");
 425
 426         if (tid_geq(journal->j_commit_waited, commit_transaction->t_tid))
 427                 write_op = WRITE_SYNC;
 428
 429         /*
 430          * Now start flushing things to disk, in the order they appear
 431          * on the transaction lists.  Data blocks go first.
 432          */
 433         blk_start_plug(&plug);
 434         err = journal_submit_data_buffers(journal, commit_transaction,
 435                                           write_op);
 436         blk_finish_plug(&plug);
 437
 438         /*
 439          * Wait for all previously submitted IO to complete.
 440          */
 441         spin_lock(&journal->j_list_lock);
 442         while (commit_transaction->t_locked_list) {
 443                 struct buffer_head *bh;
 444
 445                 jh = commit_transaction->t_locked_list->b_tprev;
 446                 bh = jh2bh(jh);
 447                 get_bh(bh);
 448                 if (buffer_locked(bh)) {
 449                         spin_unlock(&journal->j_list_lock);
 450                         wait_on_buffer(bh);
 451                         spin_lock(&journal->j_list_lock);
 452                 }
 453                 if (unlikely(!buffer_uptodate(bh))) {
 454                         if (!trylock_page(bh->b_page)) {
 455                                 spin_unlock(&journal->j_list_lock);
 456                                 lock_page(bh->b_page);
 457                                 spin_lock(&journal->j_list_lock);
 458                         }
 459                         if (bh->b_page->mapping)
 460                                 set_bit(AS_EIO, &bh->b_page->mapping->flags);
 461
 462                         unlock_page(bh->b_page);
 463                         SetPageError(bh->b_page);
 464                         err = -EIO;
 465                 }
 466                 if (!inverted_lock(journal, bh)) {
 467                         put_bh(bh);
 468                         spin_lock(&journal->j_list_lock);
 469                         continue;
 470                 }
 471                 if (buffer_jbd(bh) && bh2jh(bh) == jh &&
 472                     jh->b_transaction == commit_transaction &&
 473                     jh->b_jlist == BJ_Locked)
 474                         __journal_unfile_buffer(jh);
 475                 jbd_unlock_bh_state(bh);
 476                 release_data_buffer(bh);
 477                 cond_resched_lock(&journal->j_list_lock);
 478         }
 479         spin_unlock(&journal->j_list_lock);
 480
 481         if (err) {
 482                 char b[BDEVNAME_SIZE];
 483
 484                 printk(KERN_WARNING
 485                         "JBD: Detected IO errors while flushing file data "
 486                         "on %s\n", bdevname(journal->j_fs_dev, b));
 487                 if (journal->j_flags & JFS_ABORT_ON_SYNCDATA_ERR)
 488                         journal_abort(journal, err);
 489                 err = 0;
 490         }
 491
 492         blk_start_plug(&plug);
 493
 494         journal_write_revoke_records(journal, commit_transaction, write_op);
 495
 496         /*
 497          * If we found any dirty or locked buffers, then we should have
 498          * looped back up to the write_out_data label.  If there weren't
 499          * any then journal_clean_data_list should have wiped the list
 500          * clean by now, so check that it is in fact empty.
 501          */
 502         J_ASSERT (commit_transaction->t_sync_datalist == NULL);
 503
 504         jbd_debug (3, "JBD: commit phase 3\n");
 505
 506         /*
 507          * Way to go: we have now written out all of the data for a
 508          * transaction!  Now comes the tricky part: we need to write out
 509          * metadata.  Loop over the transaction's entire buffer list:
 510          */
 511         spin_lock(&journal->j_state_lock);
 512         commit_transaction->t_state = T_COMMIT;
 513         spin_unlock(&journal->j_state_lock);
 514
 515         trace_jbd_commit_logging(journal, commit_transaction);
 516         J_ASSERT(commit_transaction->t_nr_buffers <=
 517                  commit_transaction->t_outstanding_credits);
 518
 519         descriptor = NULL;
 520         bufs = 0;
 521         while (commit_transaction->t_buffers) {
 522
 523                 /* Find the next buffer to be journaled... */
 524
 525                 jh = commit_transaction->t_buffers;
 526
 527                 /* If we're in abort mode, we just un-journal the buffer and
 528                    release it. */
 529
 530                 if (is_journal_aborted(journal)) {
 531                         clear_buffer_jbddirty(jh2bh(jh));
 532                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 533                         journal_refile_buffer(journal, jh);
 534                         /* If that was the last one, we need to clean up
 535                          * any descriptor buffers which may have been
 536                          * already allocated, even if we are now
 537                          * aborting. */
 538                         if (!commit_transaction->t_buffers)
 539                                 goto start_journal_io;
 540                         continue;
 541                 }
 542
 543                 /* Make sure we have a descriptor block in which to
 544                    record the metadata buffer. */
 545
 546                 if (!descriptor) {
 547                         struct buffer_head *bh;
 548
 549                         J_ASSERT (bufs == 0);
 550
 551                         jbd_debug(4, "JBD: get descriptor\n");
 552
 553                         descriptor = journal_get_descriptor_buffer(journal);
 554                         if (!descriptor) {
 555                                 journal_abort(journal, -EIO);
 556                                 continue;
 557                         }
 558
 559                         bh = jh2bh(descriptor);
 560                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 561                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 562                         header = (journal_header_t *)&bh->b_data[0];
 563                         header->h_magic     = cpu_to_be32(JFS_MAGIC_NUMBER);
 564                         header->h_blocktype = cpu_to_be32(JFS_DESCRIPTOR_BLOCK);
 565                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 566
 567                         tagp = &bh->b_data[sizeof(journal_header_t)];
 568                         space_left = bh->b_size - sizeof(journal_header_t);
 569                         first_tag = 1;
 570                         set_buffer_jwrite(bh);
 571                         set_buffer_dirty(bh);
 572                         wbuf[bufs++] = bh;
 573
 574                         /* Record it so that we can wait for IO
 575                            completion later */
 576                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 577                         journal_file_buffer(descriptor, commit_transaction,
 578                                         BJ_LogCtl);
 579                 }
 580
 581                 /* Where is the buffer to be written? */
 582
 583                 err = journal_next_log_block(journal, &blocknr);
 584                 /* If the block mapping failed, just abandon the buffer
 585                    and repeat this loop: we'll fall into the
 586                    refile-on-abort condition above. */
 587                 if (err) {
 588                         journal_abort(journal, err);
 589                         continue;
 590                 }
 591
 592                 /*
 593                  * start_this_handle() uses t_outstanding_credits to determine
 594                  * the free space in the log, but this counter is changed
 595                  * by journal_next_log_block() also.
 596                  */
 597                 commit_transaction->t_outstanding_credits--;
 598
 599                 /* Bump b_count to prevent truncate from stumbling over
 600                    the shadowed buffer!  @@@ This can go if we ever get
 601                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 602                 get_bh(jh2bh(jh));
 603
 604                 /* Make a temporary IO buffer with which to write it out
 605                    (this will requeue both the metadata buffer and the
 606                    temporary IO buffer). new_bh goes on BJ_IO*/
 607
 608                 set_buffer_jwrite(jh2bh(jh));
 609                 /*
 610                  * akpm: journal_write_metadata_buffer() sets
 611                  * new_bh->b_transaction to commit_transaction.
 612                  * We need to clean this up before we release new_bh
 613                  * (which is of type BJ_IO)
 614                  */
 615                 JBUFFER_TRACE(jh, "ph3: write metadata");
 616                 flags = journal_write_metadata_buffer(commit_transaction,
 617                                                       jh, &new_jh, blocknr);
 618                 set_buffer_jwrite(jh2bh(new_jh));
 619                 wbuf[bufs++] = jh2bh(new_jh);
 620
 621                 /* Record the new block's tag in the current descriptor
 622                    buffer */
 623
 624                 tag_flag = 0;
 625                 if (flags & 1)
 626                         tag_flag |= JFS_FLAG_ESCAPE;
 627                 if (!first_tag)
 628                         tag_flag |= JFS_FLAG_SAME_UUID;
 629
 630                 tag = (journal_block_tag_t *) tagp;
 631                 tag->t_blocknr = cpu_to_be32(jh2bh(jh)->b_blocknr);
 632                 tag->t_flags = cpu_to_be32(tag_flag);
 633                 tagp += sizeof(journal_block_tag_t);
 634                 space_left -= sizeof(journal_block_tag_t);
 635
 636                 if (first_tag) {
 637                         memcpy (tagp, journal->j_uuid, 16);
 638                         tagp += 16;
 639                         space_left -= 16;
 640                         first_tag = 0;
 641                 }
 642
 643                 /* If there's no more to do, or if the descriptor is full,
 644                    let the IO rip! */
 645
 646                 if (bufs == journal->j_wbufsize ||
 647                     commit_transaction->t_buffers == NULL ||
 648                     space_left < sizeof(journal_block_tag_t) + 16) {
 649
 650                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 651
 652                         /* Write an end-of-descriptor marker before
 653                            submitting the IOs.  "tag" still points to
 654                            the last tag we set up. */
 655
 656                         tag->t_flags |= cpu_to_be32(JFS_FLAG_LAST_TAG);
 657
 658 start_journal_io:
 659                         for (i = 0; i < bufs; i++) {
 660                                 struct buffer_head *bh = wbuf[i];
 661                                 lock_buffer(bh);
 662                                 clear_buffer_dirty(bh);
 663                                 set_buffer_uptodate(bh);
 664                                 bh->b_end_io = journal_end_buffer_io_sync;
 665                                 submit_bh(write_op, bh);
 666                         }
 667                         cond_resched();
 668
 669                         /* Force a new descriptor to be generated next
 670                            time round the loop. */
 671                         descriptor = NULL;
 672                         bufs = 0;
 673                 }
 674         }
 675
 676         blk_finish_plug(&plug);
 677
 678         /* Lo and behold: we have just managed to send a transaction to
 679            the log.  Before we can commit it, wait for the IO so far to
 680            complete.  Control buffers being written are on the
 681            transaction's t_log_list queue, and metadata buffers are on
 682            the t_iobuf_list queue.
 683
 684            Wait for the buffers in reverse order.  That way we are
 685            less likely to be woken up until all IOs have completed, and
 686            so we incur less scheduling load.
 687         */
 688
 689         jbd_debug(3, "JBD: commit phase 4\n");
 690
 691         /*
 692          * akpm: these are BJ_IO, and j_list_lock is not needed.
 693          * See __journal_try_to_free_buffer.
 694          */
 695 wait_for_iobuf:
 696         while (commit_transaction->t_iobuf_list != NULL) {
 697                 struct buffer_head *bh;
 698
 699                 jh = commit_transaction->t_iobuf_list->b_tprev;
 700                 bh = jh2bh(jh);
 701                 if (buffer_locked(bh)) {
 702                         wait_on_buffer(bh);
 703                         goto wait_for_iobuf;
 704                 }
 705                 if (cond_resched())
 706                         goto wait_for_iobuf;
 707
 708                 if (unlikely(!buffer_uptodate(bh)))
 709                         err = -EIO;
 710
 711                 clear_buffer_jwrite(bh);
 712
 713                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 714                 journal_unfile_buffer(journal, jh);
 715
 716                 /*
 717                  * ->t_iobuf_list should contain only dummy buffer_heads
 718                  * which were created by journal_write_metadata_buffer().
 719                  */
 720                 BUFFER_TRACE(bh, "dumping temporary bh");
 721                 journal_put_journal_head(jh);
 722                 __brelse(bh);
 723                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 724                 free_buffer_head(bh);
 725
 726                 /* We also have to unlock and free the corresponding
 727                    shadowed buffer */
 728                 jh = commit_transaction->t_shadow_list->b_tprev;
 729                 bh = jh2bh(jh);
 730                 clear_buffer_jwrite(bh);
 731                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 732
 733                 /* The metadata is now released for reuse, but we need
 734                    to remember it against this transaction so that when
 735                    we finally commit, we can do any checkpointing
 736                    required. */
 737                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 738                 journal_file_buffer(jh, commit_transaction, BJ_Forget);
 739                 /*
 740                  * Wake up any transactions which were waiting for this
 741                  * IO to complete. The barrier must be here so that changes
 742                  * by journal_file_buffer() take effect before wake_up_bit()
 743                  * does the waitqueue check.
 744                  */
 745                 smp_mb();
 746                 wake_up_bit(&bh->b_state, BH_Unshadow);
 747                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 748                 __brelse(bh);
 749         }
 750
 751         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 752
 753         jbd_debug(3, "JBD: commit phase 5\n");
 754
 755         /* Here we wait for the revoke record and descriptor record buffers */
 756  wait_for_ctlbuf:
 757         while (commit_transaction->t_log_list != NULL) {
 758                 struct buffer_head *bh;
 759
 760                 jh = commit_transaction->t_log_list->b_tprev;
 761                 bh = jh2bh(jh);
 762                 if (buffer_locked(bh)) {
 763                         wait_on_buffer(bh);
 764                         goto wait_for_ctlbuf;
 765                 }
 766                 if (cond_resched())
 767                         goto wait_for_ctlbuf;
 768
 769                 if (unlikely(!buffer_uptodate(bh)))
 770                         err = -EIO;
 771
 772                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 773                 clear_buffer_jwrite(bh);
 774                 journal_unfile_buffer(journal, jh);
 775                 journal_put_journal_head(jh);
 776                 __brelse(bh);           /* One for getblk */
 777                 /* AKPM: bforget here */
 778         }
 779
 780         if (err)
 781                 journal_abort(journal, err);
 782
 783         jbd_debug(3, "JBD: commit phase 6\n");
 784
 785         /* All metadata is written, now write commit record and do cleanup */
 786         spin_lock(&journal->j_state_lock);
 787         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 788         commit_transaction->t_state = T_COMMIT_RECORD;
 789         spin_unlock(&journal->j_state_lock);
 790
 791         if (journal_write_commit_record(journal, commit_transaction))
 792                 err = -EIO;
 793
 794         if (err)
 795                 journal_abort(journal, err);
 796
 797         /* End of a transaction!  Finally, we can do checkpoint
 798            processing: any buffers committed as a result of this
 799            transaction can be removed from any checkpoint list it was on
 800            before. */
 801
 802         jbd_debug(3, "JBD: commit phase 7\n");
 803
 804         J_ASSERT(commit_transaction->t_sync_datalist == NULL);
 805         J_ASSERT(commit_transaction->t_buffers == NULL);
 806         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 807         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 808         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 809         J_ASSERT(commit_transaction->t_log_list == NULL);
 810
 811 restart_loop:
 812         /*
 813          * As there are other places (journal_unmap_buffer()) adding buffers
 814          * to this list we have to be careful and hold the j_list_lock.
 815          */
 816         spin_lock(&journal->j_list_lock);
 817         while (commit_transaction->t_forget) {
 818                 transaction_t *cp_transaction;
 819                 struct buffer_head *bh;
 820                 int try_to_free = 0;
 821
 822                 jh = commit_transaction->t_forget;
 823                 spin_unlock(&journal->j_list_lock);
 824                 bh = jh2bh(jh);
 825                 /*
 826                  * Get a reference so that bh cannot be freed before we are
 827                  * done with it.
 828                  */
 829                 get_bh(bh);
 830                 jbd_lock_bh_state(bh);
 831                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 832                         jh->b_transaction == journal->j_running_transaction);
 833
 834                 /*
 835                  * If there is undo-protected committed data against
 836                  * this buffer, then we can remove it now.  If it is a
 837                  * buffer needing such protection, the old frozen_data
 838                  * field now points to a committed version of the
 839                  * buffer, so rotate that field to the new committed
 840                  * data.
 841                  *
 842                  * Otherwise, we can just throw away the frozen data now.
 843                  */
 844                 if (jh->b_committed_data) {
 845                         jbd_free(jh->b_committed_data, bh->b_size);
 846                         jh->b_committed_data = NULL;
 847                         if (jh->b_frozen_data) {
 848                                 jh->b_committed_data = jh->b_frozen_data;
 849                                 jh->b_frozen_data = NULL;
 850                         }
 851                 } else if (jh->b_frozen_data) {
 852                         jbd_free(jh->b_frozen_data, bh->b_size);
 853                         jh->b_frozen_data = NULL;
 854                 }
 855
 856                 spin_lock(&journal->j_list_lock);
 857                 cp_transaction = jh->b_cp_transaction;
 858                 if (cp_transaction) {
 859                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 860                         __journal_remove_checkpoint(jh);
 861                 }
 862
 863                 /* Only re-checkpoint the buffer_head if it is marked
 864                  * dirty.  If the buffer was added to the BJ_Forget list
 865                  * by journal_forget, it may no longer be dirty and
 866                  * there's no point in keeping a checkpoint record for
 867                  * it. */
 868
 869                 /* A buffer which has been freed while still being
 870                  * journaled by a previous transaction may end up still
 871                  * being dirty here, but we want to avoid writing back
 872                  * that buffer in the future after the "add to orphan"
 873                  * operation been committed,  That's not only a performance
 874                  * gain, it also stops aliasing problems if the buffer is
 875                  * left behind for writeback and gets reallocated for another
 876                  * use in a different page. */
 877                 if (buffer_freed(bh) && !jh->b_next_transaction) {
 878                         clear_buffer_freed(bh);
 879                         clear_buffer_jbddirty(bh);
 880                 }
 881
 882                 if (buffer_jbddirty(bh)) {
 883                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 884                         __journal_insert_checkpoint(jh, commit_transaction);
 885                         if (is_journal_aborted(journal))
 886                                 clear_buffer_jbddirty(bh);
 887                 } else {
 888                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 889                         /*
 890                          * The buffer on BJ_Forget list and not jbddirty means
 891                          * it has been freed by this transaction and hence it
 892                          * could not have been reallocated until this
 893                          * transaction has committed. *BUT* it could be
 894                          * reallocated once we have written all the data to
 895                          * disk and before we process the buffer on BJ_Forget
 896                          * list.
 897                          */
 898                         if (!jh->b_next_transaction)
 899                                 try_to_free = 1;
 900                 }
 901                 JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 902                 __journal_refile_buffer(jh);
 903                 jbd_unlock_bh_state(bh);
 904                 if (try_to_free)
 905                         release_buffer_page(bh);
 906                 else
 907                         __brelse(bh);
 908                 cond_resched_lock(&journal->j_list_lock);
 909         }
 910         spin_unlock(&journal->j_list_lock);
 911         /*
 912          * This is a bit sleazy.  We use j_list_lock to protect transition
 913          * of a transaction into T_FINISHED state and calling
 914          * __journal_drop_transaction(). Otherwise we could race with
 915          * other checkpointing code processing the transaction...
 916          */
 917         spin_lock(&journal->j_state_lock);
 918         spin_lock(&journal->j_list_lock);
 919         /*
 920          * Now recheck if some buffers did not get attached to the transaction
 921          * while the lock was dropped...
 922          */
 923         if (commit_transaction->t_forget) {
 924                 spin_unlock(&journal->j_list_lock);
 925                 spin_unlock(&journal->j_state_lock);
 926                 goto restart_loop;
 927         }
 928
 929         /* Done with this transaction! */
 930
 931         jbd_debug(3, "JBD: commit phase 8\n");
 932
 933         J_ASSERT(commit_transaction->t_state == T_COMMIT_RECORD);
 934
 935         commit_transaction->t_state = T_FINISHED;
 936         J_ASSERT(commit_transaction == journal->j_committing_transaction);
 937         journal->j_commit_sequence = commit_transaction->t_tid;
 938         journal->j_committing_transaction = NULL;
 939         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
 940
 941         /*
 942          * weight the commit time higher than the average time so we don't
 943          * react too strongly to vast changes in commit time
 944          */
 945         if (likely(journal->j_average_commit_time))
 946                 journal->j_average_commit_time = (commit_time*3 +
 947                                 journal->j_average_commit_time) / 4;
 948         else
 949                 journal->j_average_commit_time = commit_time;
 950
 951         spin_unlock(&journal->j_state_lock);
 952
 953         if (commit_transaction->t_checkpoint_list == NULL &&
 954             commit_transaction->t_checkpoint_io_list == NULL) {
 955                 __journal_drop_transaction(journal, commit_transaction);
 956         } else {
 957                 if (journal->j_checkpoint_transactions == NULL) {
 958                         journal->j_checkpoint_transactions = commit_transaction;
 959                         commit_transaction->t_cpnext = commit_transaction;
 960                         commit_transaction->t_cpprev = commit_transaction;
 961                 } else {
 962                         commit_transaction->t_cpnext =
 963                                 journal->j_checkpoint_transactions;
 964                         commit_transaction->t_cpprev =
 965                                 commit_transaction->t_cpnext->t_cpprev;
 966                         commit_transaction->t_cpnext->t_cpprev =
 967                                 commit_transaction;
 968                         commit_transaction->t_cpprev->t_cpnext =
 969                                 commit_transaction;
 970                 }
 971         }
 972         spin_unlock(&journal->j_list_lock);
 973
 974         trace_jbd_end_commit(journal, commit_transaction);
 975         jbd_debug(1, "JBD: commit %d complete, head %d\n",
 976                   journal->j_commit_sequence, journal->j_tail_sequence);
 977
 978         wake_up(&journal->j_wait_done_commit);
 979 }