fs/jbd2/commit.c

   1 /*
   2  * linux/fs/jbd2/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/jbd2.h>
  19 #include <linux/errno.h>
  20 #include <linux/slab.h>
  21 #include <linux/mm.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/jiffies.h>
  24 #include <linux/crc32.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 sucessfully 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 lock_journal(), and possibly under journal_datalist_lock.  The
  51  * caller provided us with a ref 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 (TestSetPageLocked(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  * Try to acquire jbd_lock_bh_state() against the buffer, when j_list_lock is
  84  * held.  For ranking reasons we must trylock.  If we lose, schedule away and
  85  * return 0.  j_list_lock is dropped in this case.
  86  */
  87 static int inverted_lock(journal_t *journal, struct buffer_head *bh)
  88 {
  89         if (!jbd_trylock_bh_state(bh)) {
  90                 spin_unlock(&journal->j_list_lock);
  91                 schedule();
  92                 return 0;
  93         }
  94         return 1;
  95 }
  96
  97 /*
  98  * Done it all: now submit the commit record.  We should have
  99  * cleaned up our previous buffers by now, so if we are in abort
 100  * mode we can now just skip the rest of the journal write
 101  * entirely.
 102  *
 103  * Returns 1 if the journal needs to be aborted or 0 on success
 104  */
 105 static int journal_submit_commit_record(journal_t *journal,
 106                                         transaction_t *commit_transaction,
 107                                         struct buffer_head **cbh,
 108                                         __u32 crc32_sum)
 109 {
 110         struct journal_head *descriptor;
 111         struct commit_header *tmp;
 112         struct buffer_head *bh;
 113         int ret;
 114         int barrier_done = 0;
 115
 116         if (is_journal_aborted(journal))
 117                 return 0;
 118
 119         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 120         if (!descriptor)
 121                 return 1;
 122
 123         bh = jh2bh(descriptor);
 124
 125         tmp = (struct commit_header *)bh->b_data;
 126         tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
 127         tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
 128         tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 129
 130         if (JBD2_HAS_COMPAT_FEATURE(journal,
 131                                     JBD2_FEATURE_COMPAT_CHECKSUM)) {
 132                 tmp->h_chksum_type      = JBD2_CRC32_CHKSUM;
 133                 tmp->h_chksum_size      = JBD2_CRC32_CHKSUM_SIZE;
 134                 tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
 135         }
 136
 137         JBUFFER_TRACE(descriptor, "submit commit block");
 138         lock_buffer(bh);
 139         get_bh(bh);
 140         set_buffer_dirty(bh);
 141         set_buffer_uptodate(bh);
 142         bh->b_end_io = journal_end_buffer_io_sync;
 143
 144         if (journal->j_flags & JBD2_BARRIER &&
 145                 !JBD2_HAS_INCOMPAT_FEATURE(journal,
 146                                          JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 147                 set_buffer_ordered(bh);
 148                 barrier_done = 1;
 149         }
 150         ret = submit_bh(WRITE, bh);
 151         if (barrier_done)
 152                 clear_buffer_ordered(bh);
 153
 154         /* is it possible for another commit to fail at roughly
 155          * the same time as this one?  If so, we don't want to
 156          * trust the barrier flag in the super, but instead want
 157          * to remember if we sent a barrier request
 158          */
 159         if (ret == -EOPNOTSUPP && barrier_done) {
 160                 char b[BDEVNAME_SIZE];
 161
 162                 printk(KERN_WARNING
 163                         "JBD: barrier-based sync failed on %s - "
 164                         "disabling barriers\n",
 165                         bdevname(journal->j_dev, b));
 166                 spin_lock(&journal->j_state_lock);
 167                 journal->j_flags &= ~JBD2_BARRIER;
 168                 spin_unlock(&journal->j_state_lock);
 169
 170                 /* And try again, without the barrier */
 171                 set_buffer_uptodate(bh);
 172                 set_buffer_dirty(bh);
 173                 ret = submit_bh(WRITE, bh);
 174         }
 175         *cbh = bh;
 176         return ret;
 177 }
 178
 179 /*
 180  * This function along with journal_submit_commit_record
 181  * allows to write the commit record asynchronously.
 182  */
 183 static int journal_wait_on_commit_record(struct buffer_head *bh)
 184 {
 185         int ret = 0;
 186
 187         clear_buffer_dirty(bh);
 188         wait_on_buffer(bh);
 189
 190         if (unlikely(!buffer_uptodate(bh)))
 191                 ret = -EIO;
 192         put_bh(bh);            /* One for getblk() */
 193         jbd2_journal_put_journal_head(bh2jh(bh));
 194
 195         return ret;
 196 }
 197
 198 /*
 199  * Wait for all submitted IO to complete.
 200  */
 201 static int journal_wait_on_locked_list(journal_t *journal,
 202                                        transaction_t *commit_transaction)
 203 {
 204         int ret = 0;
 205         struct journal_head *jh;
 206
 207         while (commit_transaction->t_locked_list) {
 208                 struct buffer_head *bh;
 209
 210                 jh = commit_transaction->t_locked_list->b_tprev;
 211                 bh = jh2bh(jh);
 212                 get_bh(bh);
 213                 if (buffer_locked(bh)) {
 214                         spin_unlock(&journal->j_list_lock);
 215                         wait_on_buffer(bh);
 216                         if (unlikely(!buffer_uptodate(bh)))
 217                                 ret = -EIO;
 218                         spin_lock(&journal->j_list_lock);
 219                 }
 220                 if (!inverted_lock(journal, bh)) {
 221                         put_bh(bh);
 222                         spin_lock(&journal->j_list_lock);
 223                         continue;
 224                 }
 225                 if (buffer_jbd(bh) && jh->b_jlist == BJ_Locked) {
 226                         __jbd2_journal_unfile_buffer(jh);
 227                         jbd_unlock_bh_state(bh);
 228                         jbd2_journal_remove_journal_head(bh);
 229                         put_bh(bh);
 230                 } else {
 231                         jbd_unlock_bh_state(bh);
 232                 }
 233                 put_bh(bh);
 234                 cond_resched_lock(&journal->j_list_lock);
 235         }
 236         return ret;
 237   }
 238
 239 static void journal_do_submit_data(struct buffer_head **wbuf, int bufs)
 240 {
 241         int i;
 242
 243         for (i = 0; i < bufs; i++) {
 244                 wbuf[i]->b_end_io = end_buffer_write_sync;
 245                 /* We use-up our safety reference in submit_bh() */
 246                 submit_bh(WRITE, wbuf[i]);
 247         }
 248 }
 249
 250 /*
 251  *  Submit all the data buffers to disk
 252  */
 253 static void journal_submit_data_buffers(journal_t *journal,
 254                                 transaction_t *commit_transaction)
 255 {
 256         struct journal_head *jh;
 257         struct buffer_head *bh;
 258         int locked;
 259         int bufs = 0;
 260         struct buffer_head **wbuf = journal->j_wbuf;
 261
 262         /*
 263          * Whenever we unlock the journal and sleep, things can get added
 264          * onto ->t_sync_datalist, so we have to keep looping back to
 265          * write_out_data until we *know* that the list is empty.
 266          *
 267          * Cleanup any flushed data buffers from the data list.  Even in
 268          * abort mode, we want to flush this out as soon as possible.
 269          */
 270 write_out_data:
 271         cond_resched();
 272         spin_lock(&journal->j_list_lock);
 273
 274         while (commit_transaction->t_sync_datalist) {
 275                 jh = commit_transaction->t_sync_datalist;
 276                 bh = jh2bh(jh);
 277                 locked = 0;
 278
 279                 /* Get reference just to make sure buffer does not disappear
 280                  * when we are forced to drop various locks */
 281                 get_bh(bh);
 282                 /* If the buffer is dirty, we need to submit IO and hence
 283                  * we need the buffer lock. We try to lock the buffer without
 284                  * blocking. If we fail, we need to drop j_list_lock and do
 285                  * blocking lock_buffer().
 286                  */
 287                 if (buffer_dirty(bh)) {
 288                         if (test_set_buffer_locked(bh)) {
 289                                 BUFFER_TRACE(bh, "needs blocking lock");
 290                                 spin_unlock(&journal->j_list_lock);
 291                                 /* Write out all data to prevent deadlocks */
 292                                 journal_do_submit_data(wbuf, bufs);
 293                                 bufs = 0;
 294                                 lock_buffer(bh);
 295                                 spin_lock(&journal->j_list_lock);
 296                         }
 297                         locked = 1;
 298                 }
 299                 /* We have to get bh_state lock. Again out of order, sigh. */
 300                 if (!inverted_lock(journal, bh)) {
 301                         jbd_lock_bh_state(bh);
 302                         spin_lock(&journal->j_list_lock);
 303                 }
 304                 /* Someone already cleaned up the buffer? */
 305                 if (!buffer_jbd(bh)
 306                         || jh->b_transaction != commit_transaction
 307                         || jh->b_jlist != BJ_SyncData) {
 308                         jbd_unlock_bh_state(bh);
 309                         if (locked)
 310                                 unlock_buffer(bh);
 311                         BUFFER_TRACE(bh, "already cleaned up");
 312                         put_bh(bh);
 313                         continue;
 314                 }
 315                 if (locked && test_clear_buffer_dirty(bh)) {
 316                         BUFFER_TRACE(bh, "needs writeout, adding to array");
 317                         wbuf[bufs++] = bh;
 318                         __jbd2_journal_file_buffer(jh, commit_transaction,
 319                                                 BJ_Locked);
 320                         jbd_unlock_bh_state(bh);
 321                         if (bufs == journal->j_wbufsize) {
 322                                 spin_unlock(&journal->j_list_lock);
 323                                 journal_do_submit_data(wbuf, bufs);
 324                                 bufs = 0;
 325                                 goto write_out_data;
 326                         }
 327                 } else if (!locked && buffer_locked(bh)) {
 328                         __jbd2_journal_file_buffer(jh, commit_transaction,
 329                                                 BJ_Locked);
 330                         jbd_unlock_bh_state(bh);
 331                         put_bh(bh);
 332                 } else {
 333                         BUFFER_TRACE(bh, "writeout complete: unfile");
 334                         __jbd2_journal_unfile_buffer(jh);
 335                         jbd_unlock_bh_state(bh);
 336                         if (locked)
 337                                 unlock_buffer(bh);
 338                         jbd2_journal_remove_journal_head(bh);
 339                         /* Once for our safety reference, once for
 340                          * jbd2_journal_remove_journal_head() */
 341                         put_bh(bh);
 342                         put_bh(bh);
 343                 }
 344
 345                 if (need_resched() || spin_needbreak(&journal->j_list_lock)) {
 346                         spin_unlock(&journal->j_list_lock);
 347                         goto write_out_data;
 348                 }
 349         }
 350         spin_unlock(&journal->j_list_lock);
 351         journal_do_submit_data(wbuf, bufs);
 352 }
 353
 354 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 355 {
 356         struct page *page = bh->b_page;
 357         char *addr;
 358         __u32 checksum;
 359
 360         addr = kmap_atomic(page, KM_USER0);
 361         checksum = crc32_be(crc32_sum,
 362                 (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
 363         kunmap_atomic(addr, KM_USER0);
 364
 365         return checksum;
 366 }
 367
 368 static void write_tag_block(int tag_bytes, journal_block_tag_t *tag,
 369                                    unsigned long long block)
 370 {
 371         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
 372         if (tag_bytes > JBD2_TAG_SIZE32)
 373                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
 374 }
 375
 376 /*
 377  * jbd2_journal_commit_transaction
 378  *
 379  * The primary function for committing a transaction to the log.  This
 380  * function is called by the journal thread to begin a complete commit.
 381  */
 382 void jbd2_journal_commit_transaction(journal_t *journal)
 383 {
 384         struct transaction_stats_s stats;
 385         transaction_t *commit_transaction;
 386         struct journal_head *jh, *new_jh, *descriptor;
 387         struct buffer_head **wbuf = journal->j_wbuf;
 388         int bufs;
 389         int flags;
 390         int err;
 391         unsigned long long blocknr;
 392         char *tagp = NULL;
 393         journal_header_t *header;
 394         journal_block_tag_t *tag = NULL;
 395         int space_left = 0;
 396         int first_tag = 0;
 397         int tag_flag;
 398         int i;
 399         int tag_bytes = journal_tag_bytes(journal);
 400         struct buffer_head *cbh = NULL; /* For transactional checksums */
 401         __u32 crc32_sum = ~0;
 402
 403         /*
 404          * First job: lock down the current transaction and wait for
 405          * all outstanding updates to complete.
 406          */
 407
 408 #ifdef COMMIT_STATS
 409         spin_lock(&journal->j_list_lock);
 410         summarise_journal_usage(journal);
 411         spin_unlock(&journal->j_list_lock);
 412 #endif
 413
 414         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 415         if (journal->j_flags & JBD2_FLUSHED) {
 416                 jbd_debug(3, "super block updated\n");
 417                 jbd2_journal_update_superblock(journal, 1);
 418         } else {
 419                 jbd_debug(3, "superblock not updated\n");
 420         }
 421
 422         J_ASSERT(journal->j_running_transaction != NULL);
 423         J_ASSERT(journal->j_committing_transaction == NULL);
 424
 425         commit_transaction = journal->j_running_transaction;
 426         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 427
 428         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 429                         commit_transaction->t_tid);
 430
 431         spin_lock(&journal->j_state_lock);
 432         commit_transaction->t_state = T_LOCKED;
 433
 434         stats.u.run.rs_wait = commit_transaction->t_max_wait;
 435         stats.u.run.rs_locked = jiffies;
 436         stats.u.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 437                                                 stats.u.run.rs_locked);
 438
 439         spin_lock(&commit_transaction->t_handle_lock);
 440         while (commit_transaction->t_updates) {
 441                 DEFINE_WAIT(wait);
 442
 443                 prepare_to_wait(&journal->j_wait_updates, &wait,
 444                                         TASK_UNINTERRUPTIBLE);
 445                 if (commit_transaction->t_updates) {
 446                         spin_unlock(&commit_transaction->t_handle_lock);
 447                         spin_unlock(&journal->j_state_lock);
 448                         schedule();
 449                         spin_lock(&journal->j_state_lock);
 450                         spin_lock(&commit_transaction->t_handle_lock);
 451                 }
 452                 finish_wait(&journal->j_wait_updates, &wait);
 453         }
 454         spin_unlock(&commit_transaction->t_handle_lock);
 455
 456         J_ASSERT (commit_transaction->t_outstanding_credits <=
 457                         journal->j_max_transaction_buffers);
 458
 459         /*
 460          * First thing we are allowed to do is to discard any remaining
 461          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 462          * that there are no such buffers: if a large filesystem
 463          * operation like a truncate needs to split itself over multiple
 464          * transactions, then it may try to do a jbd2_journal_restart() while
 465          * there are still BJ_Reserved buffers outstanding.  These must
 466          * be released cleanly from the current transaction.
 467          *
 468          * In this case, the filesystem must still reserve write access
 469          * again before modifying the buffer in the new transaction, but
 470          * we do not require it to remember exactly which old buffers it
 471          * has reserved.  This is consistent with the existing behaviour
 472          * that multiple jbd2_journal_get_write_access() calls to the same
 473          * buffer are perfectly permissable.
 474          */
 475         while (commit_transaction->t_reserved_list) {
 476                 jh = commit_transaction->t_reserved_list;
 477                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 478                 /*
 479                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 480                  * leave undo-committed data.
 481                  */
 482                 if (jh->b_committed_data) {
 483                         struct buffer_head *bh = jh2bh(jh);
 484
 485                         jbd_lock_bh_state(bh);
 486                         jbd2_free(jh->b_committed_data, bh->b_size);
 487                         jh->b_committed_data = NULL;
 488                         jbd_unlock_bh_state(bh);
 489                 }
 490                 jbd2_journal_refile_buffer(journal, jh);
 491         }
 492
 493         /*
 494          * Now try to drop any written-back buffers from the journal's
 495          * checkpoint lists.  We do this *before* commit because it potentially
 496          * frees some memory
 497          */
 498         spin_lock(&journal->j_list_lock);
 499         __jbd2_journal_clean_checkpoint_list(journal);
 500         spin_unlock(&journal->j_list_lock);
 501
 502         jbd_debug (3, "JBD: commit phase 1\n");
 503
 504         /*
 505          * Switch to a new revoke table.
 506          */
 507         jbd2_journal_switch_revoke_table(journal);
 508
 509         stats.u.run.rs_flushing = jiffies;
 510         stats.u.run.rs_locked = jbd2_time_diff(stats.u.run.rs_locked,
 511                                                stats.u.run.rs_flushing);
 512
 513         commit_transaction->t_state = T_FLUSH;
 514         journal->j_committing_transaction = commit_transaction;
 515         journal->j_running_transaction = NULL;
 516         commit_transaction->t_log_start = journal->j_head;
 517         wake_up(&journal->j_wait_transaction_locked);
 518         spin_unlock(&journal->j_state_lock);
 519
 520         jbd_debug (3, "JBD: commit phase 2\n");
 521
 522         /*
 523          * Now start flushing things to disk, in the order they appear
 524          * on the transaction lists.  Data blocks go first.
 525          */
 526         err = 0;
 527         journal_submit_data_buffers(journal, commit_transaction);
 528
 529         /*
 530          * Wait for all previously submitted IO to complete if commit
 531          * record is to be written synchronously.
 532          */
 533         spin_lock(&journal->j_list_lock);
 534         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 535                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT))
 536                 err = journal_wait_on_locked_list(journal,
 537                                                 commit_transaction);
 538
 539         spin_unlock(&journal->j_list_lock);
 540
 541         if (err)
 542                 jbd2_journal_abort(journal, err);
 543
 544         jbd2_journal_write_revoke_records(journal, commit_transaction);
 545
 546         jbd_debug(3, "JBD: commit phase 2\n");
 547
 548         /*
 549          * If we found any dirty or locked buffers, then we should have
 550          * looped back up to the write_out_data label.  If there weren't
 551          * any then journal_clean_data_list should have wiped the list
 552          * clean by now, so check that it is in fact empty.
 553          */
 554         J_ASSERT (commit_transaction->t_sync_datalist == NULL);
 555
 556         jbd_debug (3, "JBD: commit phase 3\n");
 557
 558         /*
 559          * Way to go: we have now written out all of the data for a
 560          * transaction!  Now comes the tricky part: we need to write out
 561          * metadata.  Loop over the transaction's entire buffer list:
 562          */
 563         commit_transaction->t_state = T_COMMIT;
 564
 565         stats.u.run.rs_logging = jiffies;
 566         stats.u.run.rs_flushing = jbd2_time_diff(stats.u.run.rs_flushing,
 567                                                  stats.u.run.rs_logging);
 568         stats.u.run.rs_blocks = commit_transaction->t_outstanding_credits;
 569         stats.u.run.rs_blocks_logged = 0;
 570
 571         J_ASSERT(commit_transaction->t_nr_buffers <=
 572                  commit_transaction->t_outstanding_credits);
 573
 574         descriptor = NULL;
 575         bufs = 0;
 576         while (commit_transaction->t_buffers) {
 577
 578                 /* Find the next buffer to be journaled... */
 579
 580                 jh = commit_transaction->t_buffers;
 581
 582                 /* If we're in abort mode, we just un-journal the buffer and
 583                    release it for background writing. */
 584
 585                 if (is_journal_aborted(journal)) {
 586                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 587                         jbd2_journal_refile_buffer(journal, jh);
 588                         /* If that was the last one, we need to clean up
 589                          * any descriptor buffers which may have been
 590                          * already allocated, even if we are now
 591                          * aborting. */
 592                         if (!commit_transaction->t_buffers)
 593                                 goto start_journal_io;
 594                         continue;
 595                 }
 596
 597                 /* Make sure we have a descriptor block in which to
 598                    record the metadata buffer. */
 599
 600                 if (!descriptor) {
 601                         struct buffer_head *bh;
 602
 603                         J_ASSERT (bufs == 0);
 604
 605                         jbd_debug(4, "JBD: get descriptor\n");
 606
 607                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 608                         if (!descriptor) {
 609                                 jbd2_journal_abort(journal, -EIO);
 610                                 continue;
 611                         }
 612
 613                         bh = jh2bh(descriptor);
 614                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 615                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 616                         header = (journal_header_t *)&bh->b_data[0];
 617                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 618                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 619                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 620
 621                         tagp = &bh->b_data[sizeof(journal_header_t)];
 622                         space_left = bh->b_size - sizeof(journal_header_t);
 623                         first_tag = 1;
 624                         set_buffer_jwrite(bh);
 625                         set_buffer_dirty(bh);
 626                         wbuf[bufs++] = bh;
 627
 628                         /* Record it so that we can wait for IO
 629                            completion later */
 630                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 631                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 632                                         BJ_LogCtl);
 633                 }
 634
 635                 /* Where is the buffer to be written? */
 636
 637                 err = jbd2_journal_next_log_block(journal, &blocknr);
 638                 /* If the block mapping failed, just abandon the buffer
 639                    and repeat this loop: we'll fall into the
 640                    refile-on-abort condition above. */
 641                 if (err) {
 642                         jbd2_journal_abort(journal, err);
 643                         continue;
 644                 }
 645
 646                 /*
 647                  * start_this_handle() uses t_outstanding_credits to determine
 648                  * the free space in the log, but this counter is changed
 649                  * by jbd2_journal_next_log_block() also.
 650                  */
 651                 commit_transaction->t_outstanding_credits--;
 652
 653                 /* Bump b_count to prevent truncate from stumbling over
 654                    the shadowed buffer!  @@@ This can go if we ever get
 655                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 656                 atomic_inc(&jh2bh(jh)->b_count);
 657
 658                 /* Make a temporary IO buffer with which to write it out
 659                    (this will requeue both the metadata buffer and the
 660                    temporary IO buffer). new_bh goes on BJ_IO*/
 661
 662                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 663                 /*
 664                  * akpm: jbd2_journal_write_metadata_buffer() sets
 665                  * new_bh->b_transaction to commit_transaction.
 666                  * We need to clean this up before we release new_bh
 667                  * (which is of type BJ_IO)
 668                  */
 669                 JBUFFER_TRACE(jh, "ph3: write metadata");
 670                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 671                                                       jh, &new_jh, blocknr);
 672                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 673                 wbuf[bufs++] = jh2bh(new_jh);
 674
 675                 /* Record the new block's tag in the current descriptor
 676                    buffer */
 677
 678                 tag_flag = 0;
 679                 if (flags & 1)
 680                         tag_flag |= JBD2_FLAG_ESCAPE;
 681                 if (!first_tag)
 682                         tag_flag |= JBD2_FLAG_SAME_UUID;
 683
 684                 tag = (journal_block_tag_t *) tagp;
 685                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 686                 tag->t_flags = cpu_to_be32(tag_flag);
 687                 tagp += tag_bytes;
 688                 space_left -= tag_bytes;
 689
 690                 if (first_tag) {
 691                         memcpy (tagp, journal->j_uuid, 16);
 692                         tagp += 16;
 693                         space_left -= 16;
 694                         first_tag = 0;
 695                 }
 696
 697                 /* If there's no more to do, or if the descriptor is full,
 698                    let the IO rip! */
 699
 700                 if (bufs == journal->j_wbufsize ||
 701                     commit_transaction->t_buffers == NULL ||
 702                     space_left < tag_bytes + 16) {
 703
 704                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 705
 706                         /* Write an end-of-descriptor marker before
 707                            submitting the IOs.  "tag" still points to
 708                            the last tag we set up. */
 709
 710                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 711
 712 start_journal_io:
 713                         for (i = 0; i < bufs; i++) {
 714                                 struct buffer_head *bh = wbuf[i];
 715                                 /*
 716                                  * Compute checksum.
 717                                  */
 718                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 719                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 720                                         crc32_sum =
 721                                             jbd2_checksum_data(crc32_sum, bh);
 722                                 }
 723
 724                                 lock_buffer(bh);
 725                                 clear_buffer_dirty(bh);
 726                                 set_buffer_uptodate(bh);
 727                                 bh->b_end_io = journal_end_buffer_io_sync;
 728                                 submit_bh(WRITE, bh);
 729                         }
 730                         cond_resched();
 731                         stats.u.run.rs_blocks_logged += bufs;
 732
 733                         /* Force a new descriptor to be generated next
 734                            time round the loop. */
 735                         descriptor = NULL;
 736                         bufs = 0;
 737                 }
 738         }
 739
 740         /* Done it all: now write the commit record asynchronously. */
 741
 742         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 743                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 744                 err = journal_submit_commit_record(journal, commit_transaction,
 745                                                  &cbh, crc32_sum);
 746                 if (err)
 747                         __jbd2_journal_abort_hard(journal);
 748
 749                 spin_lock(&journal->j_list_lock);
 750                 err = journal_wait_on_locked_list(journal,
 751                                                 commit_transaction);
 752                 spin_unlock(&journal->j_list_lock);
 753                 if (err)
 754                         __jbd2_journal_abort_hard(journal);
 755         }
 756
 757         /* Lo and behold: we have just managed to send a transaction to
 758            the log.  Before we can commit it, wait for the IO so far to
 759            complete.  Control buffers being written are on the
 760            transaction's t_log_list queue, and metadata buffers are on
 761            the t_iobuf_list queue.
 762
 763            Wait for the buffers in reverse order.  That way we are
 764            less likely to be woken up until all IOs have completed, and
 765            so we incur less scheduling load.
 766         */
 767
 768         jbd_debug(3, "JBD: commit phase 4\n");
 769
 770         /*
 771          * akpm: these are BJ_IO, and j_list_lock is not needed.
 772          * See __journal_try_to_free_buffer.
 773          */
 774 wait_for_iobuf:
 775         while (commit_transaction->t_iobuf_list != NULL) {
 776                 struct buffer_head *bh;
 777
 778                 jh = commit_transaction->t_iobuf_list->b_tprev;
 779                 bh = jh2bh(jh);
 780                 if (buffer_locked(bh)) {
 781                         wait_on_buffer(bh);
 782                         goto wait_for_iobuf;
 783                 }
 784                 if (cond_resched())
 785                         goto wait_for_iobuf;
 786
 787                 if (unlikely(!buffer_uptodate(bh)))
 788                         err = -EIO;
 789
 790                 clear_buffer_jwrite(bh);
 791
 792                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 793                 jbd2_journal_unfile_buffer(journal, jh);
 794
 795                 /*
 796                  * ->t_iobuf_list should contain only dummy buffer_heads
 797                  * which were created by jbd2_journal_write_metadata_buffer().
 798                  */
 799                 BUFFER_TRACE(bh, "dumping temporary bh");
 800                 jbd2_journal_put_journal_head(jh);
 801                 __brelse(bh);
 802                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 803                 free_buffer_head(bh);
 804
 805                 /* We also have to unlock and free the corresponding
 806                    shadowed buffer */
 807                 jh = commit_transaction->t_shadow_list->b_tprev;
 808                 bh = jh2bh(jh);
 809                 clear_bit(BH_JWrite, &bh->b_state);
 810                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 811
 812                 /* The metadata is now released for reuse, but we need
 813                    to remember it against this transaction so that when
 814                    we finally commit, we can do any checkpointing
 815                    required. */
 816                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 817                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 818                 /* Wake up any transactions which were waiting for this
 819                    IO to complete */
 820                 wake_up_bit(&bh->b_state, BH_Unshadow);
 821                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 822                 __brelse(bh);
 823         }
 824
 825         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 826
 827         jbd_debug(3, "JBD: commit phase 5\n");
 828
 829         /* Here we wait for the revoke record and descriptor record buffers */
 830  wait_for_ctlbuf:
 831         while (commit_transaction->t_log_list != NULL) {
 832                 struct buffer_head *bh;
 833
 834                 jh = commit_transaction->t_log_list->b_tprev;
 835                 bh = jh2bh(jh);
 836                 if (buffer_locked(bh)) {
 837                         wait_on_buffer(bh);
 838                         goto wait_for_ctlbuf;
 839                 }
 840                 if (cond_resched())
 841                         goto wait_for_ctlbuf;
 842
 843                 if (unlikely(!buffer_uptodate(bh)))
 844                         err = -EIO;
 845
 846                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 847                 clear_buffer_jwrite(bh);
 848                 jbd2_journal_unfile_buffer(journal, jh);
 849                 jbd2_journal_put_journal_head(jh);
 850                 __brelse(bh);           /* One for getblk */
 851                 /* AKPM: bforget here */
 852         }
 853
 854         jbd_debug(3, "JBD: commit phase 6\n");
 855
 856         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 857                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 858                 err = journal_submit_commit_record(journal, commit_transaction,
 859                                                 &cbh, crc32_sum);
 860                 if (err)
 861                         __jbd2_journal_abort_hard(journal);
 862         }
 863         if (!err && !is_journal_aborted(journal))
 864                 err = journal_wait_on_commit_record(cbh);
 865
 866         if (err)
 867                 jbd2_journal_abort(journal, err);
 868
 869         /* End of a transaction!  Finally, we can do checkpoint
 870            processing: any buffers committed as a result of this
 871            transaction can be removed from any checkpoint list it was on
 872            before. */
 873
 874         jbd_debug(3, "JBD: commit phase 7\n");
 875
 876         J_ASSERT(commit_transaction->t_sync_datalist == NULL);
 877         J_ASSERT(commit_transaction->t_buffers == NULL);
 878         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 879         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 880         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 881         J_ASSERT(commit_transaction->t_log_list == NULL);
 882
 883 restart_loop:
 884         /*
 885          * As there are other places (journal_unmap_buffer()) adding buffers
 886          * to this list we have to be careful and hold the j_list_lock.
 887          */
 888         spin_lock(&journal->j_list_lock);
 889         while (commit_transaction->t_forget) {
 890                 transaction_t *cp_transaction;
 891                 struct buffer_head *bh;
 892
 893                 jh = commit_transaction->t_forget;
 894                 spin_unlock(&journal->j_list_lock);
 895                 bh = jh2bh(jh);
 896                 jbd_lock_bh_state(bh);
 897                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 898                         jh->b_transaction == journal->j_running_transaction);
 899
 900                 /*
 901                  * If there is undo-protected committed data against
 902                  * this buffer, then we can remove it now.  If it is a
 903                  * buffer needing such protection, the old frozen_data
 904                  * field now points to a committed version of the
 905                  * buffer, so rotate that field to the new committed
 906                  * data.
 907                  *
 908                  * Otherwise, we can just throw away the frozen data now.
 909                  */
 910                 if (jh->b_committed_data) {
 911                         jbd2_free(jh->b_committed_data, bh->b_size);
 912                         jh->b_committed_data = NULL;
 913                         if (jh->b_frozen_data) {
 914                                 jh->b_committed_data = jh->b_frozen_data;
 915                                 jh->b_frozen_data = NULL;
 916                         }
 917                 } else if (jh->b_frozen_data) {
 918                         jbd2_free(jh->b_frozen_data, bh->b_size);
 919                         jh->b_frozen_data = NULL;
 920                 }
 921
 922                 spin_lock(&journal->j_list_lock);
 923                 cp_transaction = jh->b_cp_transaction;
 924                 if (cp_transaction) {
 925                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 926                         cp_transaction->t_chp_stats.cs_dropped++;
 927                         __jbd2_journal_remove_checkpoint(jh);
 928                 }
 929
 930                 /* Only re-checkpoint the buffer_head if it is marked
 931                  * dirty.  If the buffer was added to the BJ_Forget list
 932                  * by jbd2_journal_forget, it may no longer be dirty and
 933                  * there's no point in keeping a checkpoint record for
 934                  * it. */
 935
 936                 /* A buffer which has been freed while still being
 937                  * journaled by a previous transaction may end up still
 938                  * being dirty here, but we want to avoid writing back
 939                  * that buffer in the future now that the last use has
 940                  * been committed.  That's not only a performance gain,
 941                  * it also stops aliasing problems if the buffer is left
 942                  * behind for writeback and gets reallocated for another
 943                  * use in a different page. */
 944                 if (buffer_freed(bh)) {
 945                         clear_buffer_freed(bh);
 946                         clear_buffer_jbddirty(bh);
 947                 }
 948
 949                 if (buffer_jbddirty(bh)) {
 950                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 951                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 952                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 953                         __jbd2_journal_refile_buffer(jh);
 954                         jbd_unlock_bh_state(bh);
 955                 } else {
 956                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 957                         /* The buffer on BJ_Forget list and not jbddirty means
 958                          * it has been freed by this transaction and hence it
 959                          * could not have been reallocated until this
 960                          * transaction has committed. *BUT* it could be
 961                          * reallocated once we have written all the data to
 962                          * disk and before we process the buffer on BJ_Forget
 963                          * list. */
 964                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 965                         __jbd2_journal_refile_buffer(jh);
 966                         if (!jh->b_transaction) {
 967                                 jbd_unlock_bh_state(bh);
 968                                  /* needs a brelse */
 969                                 jbd2_journal_remove_journal_head(bh);
 970                                 release_buffer_page(bh);
 971                         } else
 972                                 jbd_unlock_bh_state(bh);
 973                 }
 974                 cond_resched_lock(&journal->j_list_lock);
 975         }
 976         spin_unlock(&journal->j_list_lock);
 977         /*
 978          * This is a bit sleazy.  We use j_list_lock to protect transition
 979          * of a transaction into T_FINISHED state and calling
 980          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 981          * other checkpointing code processing the transaction...
 982          */
 983         spin_lock(&journal->j_state_lock);
 984         spin_lock(&journal->j_list_lock);
 985         /*
 986          * Now recheck if some buffers did not get attached to the transaction
 987          * while the lock was dropped...
 988          */
 989         if (commit_transaction->t_forget) {
 990                 spin_unlock(&journal->j_list_lock);
 991                 spin_unlock(&journal->j_state_lock);
 992                 goto restart_loop;
 993         }
 994
 995         /* Done with this transaction! */
 996
 997         jbd_debug(3, "JBD: commit phase 8\n");
 998
 999         J_ASSERT(commit_transaction->t_state == T_COMMIT);
1000
1001         commit_transaction->t_start = jiffies;
1002         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
1003                                                 commit_transaction->t_start);
1004
1005         /*
1006          * File the transaction for history
1007          */
1008         stats.ts_type = JBD2_STATS_RUN;
1009         stats.ts_tid = commit_transaction->t_tid;
1010         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
1011         spin_lock(&journal->j_history_lock);
1012         memcpy(journal->j_history + journal->j_history_cur, &stats,
1013                         sizeof(stats));
1014         if (++journal->j_history_cur == journal->j_history_max)
1015                 journal->j_history_cur = 0;
1016
1017         /*
1018          * Calculate overall stats
1019          */
1020         journal->j_stats.ts_tid++;
1021         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
1022         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
1023         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
1024         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
1025         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
1026         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
1027         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
1028         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
1029         spin_unlock(&journal->j_history_lock);
1030
1031         commit_transaction->t_state = T_FINISHED;
1032         J_ASSERT(commit_transaction == journal->j_committing_transaction);
1033         journal->j_commit_sequence = commit_transaction->t_tid;
1034         journal->j_committing_transaction = NULL;
1035         spin_unlock(&journal->j_state_lock);
1036
1037         if (commit_transaction->t_checkpoint_list == NULL &&
1038             commit_transaction->t_checkpoint_io_list == NULL) {
1039                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1040         } else {
1041                 if (journal->j_checkpoint_transactions == NULL) {
1042                         journal->j_checkpoint_transactions = commit_transaction;
1043                         commit_transaction->t_cpnext = commit_transaction;
1044                         commit_transaction->t_cpprev = commit_transaction;
1045                 } else {
1046                         commit_transaction->t_cpnext =
1047                                 journal->j_checkpoint_transactions;
1048                         commit_transaction->t_cpprev =
1049                                 commit_transaction->t_cpnext->t_cpprev;
1050                         commit_transaction->t_cpnext->t_cpprev =
1051                                 commit_transaction;
1052                         commit_transaction->t_cpprev->t_cpnext =
1053                                 commit_transaction;
1054                 }
1055         }
1056         spin_unlock(&journal->j_list_lock);
1057
1058         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1059                   journal->j_commit_sequence, journal->j_tail_sequence);
1060
1061         wake_up(&journal->j_wait_done_commit);
1062 }