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/marker.h>
  20 #include <linux/errno.h>
  21 #include <linux/slab.h>
  22 #include <linux/mm.h>
  23 #include <linux/pagemap.h>
  24 #include <linux/jiffies.h>
  25 #include <linux/crc32.h>
  26 #include <linux/writeback.h>
  27 #include <linux/backing-dev.h>
  28
  29 /*
  30  * Default IO end handler for temporary BJ_IO buffer_heads.
  31  */
  32 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
  33 {
  34         BUFFER_TRACE(bh, "");
  35         if (uptodate)
  36                 set_buffer_uptodate(bh);
  37         else
  38                 clear_buffer_uptodate(bh);
  39         unlock_buffer(bh);
  40 }
  41
  42 /*
  43  * When an ext4 file is truncated, it is possible that some pages are not
  44  * successfully freed, because they are attached to a committing transaction.
  45  * After the transaction commits, these pages are left on the LRU, with no
  46  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
  47  * by the VM, but their apparent absence upsets the VM accounting, and it makes
  48  * the numbers in /proc/meminfo look odd.
  49  *
  50  * So here, we have a buffer which has just come off the forget list.  Look to
  51  * see if we can strip all buffers from the backing page.
  52  *
  53  * Called under lock_journal(), and possibly under journal_datalist_lock.  The
  54  * caller provided us with a ref against the buffer, and we drop that here.
  55  */
  56 static void release_buffer_page(struct buffer_head *bh)
  57 {
  58         struct page *page;
  59
  60         if (buffer_dirty(bh))
  61                 goto nope;
  62         if (atomic_read(&bh->b_count) != 1)
  63                 goto nope;
  64         page = bh->b_page;
  65         if (!page)
  66                 goto nope;
  67         if (page->mapping)
  68                 goto nope;
  69
  70         /* OK, it's a truncated page */
  71         if (!trylock_page(page))
  72                 goto nope;
  73
  74         page_cache_get(page);
  75         __brelse(bh);
  76         try_to_free_buffers(page);
  77         unlock_page(page);
  78         page_cache_release(page);
  79         return;
  80
  81 nope:
  82         __brelse(bh);
  83 }
  84
  85 /*
  86  * Done it all: now submit the commit record.  We should have
  87  * cleaned up our previous buffers by now, so if we are in abort
  88  * mode we can now just skip the rest of the journal write
  89  * entirely.
  90  *
  91  * Returns 1 if the journal needs to be aborted or 0 on success
  92  */
  93 static int journal_submit_commit_record(journal_t *journal,
  94                                         transaction_t *commit_transaction,
  95                                         struct buffer_head **cbh,
  96                                         __u32 crc32_sum)
  97 {
  98         struct journal_head *descriptor;
  99         struct commit_header *tmp;
 100         struct buffer_head *bh;
 101         int ret;
 102         int barrier_done = 0;
 103         struct timespec now = current_kernel_time();
 104
 105         if (is_journal_aborted(journal))
 106                 return 0;
 107
 108         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 109         if (!descriptor)
 110                 return 1;
 111
 112         bh = jh2bh(descriptor);
 113
 114         tmp = (struct commit_header *)bh->b_data;
 115         tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
 116         tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
 117         tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 118         tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
 119         tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);
 120
 121         if (JBD2_HAS_COMPAT_FEATURE(journal,
 122                                     JBD2_FEATURE_COMPAT_CHECKSUM)) {
 123                 tmp->h_chksum_type      = JBD2_CRC32_CHKSUM;
 124                 tmp->h_chksum_size      = JBD2_CRC32_CHKSUM_SIZE;
 125                 tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
 126         }
 127
 128         JBUFFER_TRACE(descriptor, "submit commit block");
 129         lock_buffer(bh);
 130         clear_buffer_dirty(bh);
 131         set_buffer_uptodate(bh);
 132         bh->b_end_io = journal_end_buffer_io_sync;
 133
 134         if (journal->j_flags & JBD2_BARRIER &&
 135                 !JBD2_HAS_INCOMPAT_FEATURE(journal,
 136                                          JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 137                 set_buffer_ordered(bh);
 138                 barrier_done = 1;
 139         }
 140         ret = submit_bh(WRITE, bh);
 141         if (barrier_done)
 142                 clear_buffer_ordered(bh);
 143
 144         /* is it possible for another commit to fail at roughly
 145          * the same time as this one?  If so, we don't want to
 146          * trust the barrier flag in the super, but instead want
 147          * to remember if we sent a barrier request
 148          */
 149         if (ret == -EOPNOTSUPP && barrier_done) {
 150                 printk(KERN_WARNING
 151                        "JBD: barrier-based sync failed on %s - "
 152                        "disabling barriers\n", journal->j_devname);
 153                 spin_lock(&journal->j_state_lock);
 154                 journal->j_flags &= ~JBD2_BARRIER;
 155                 spin_unlock(&journal->j_state_lock);
 156
 157                 /* And try again, without the barrier */
 158                 lock_buffer(bh);
 159                 set_buffer_uptodate(bh);
 160                 clear_buffer_dirty(bh);
 161                 ret = submit_bh(WRITE, bh);
 162         }
 163         *cbh = bh;
 164         return ret;
 165 }
 166
 167 /*
 168  * This function along with journal_submit_commit_record
 169  * allows to write the commit record asynchronously.
 170  */
 171 static int journal_wait_on_commit_record(struct buffer_head *bh)
 172 {
 173         int ret = 0;
 174
 175         clear_buffer_dirty(bh);
 176         wait_on_buffer(bh);
 177
 178         if (unlikely(!buffer_uptodate(bh)))
 179                 ret = -EIO;
 180         put_bh(bh);            /* One for getblk() */
 181         jbd2_journal_put_journal_head(bh2jh(bh));
 182
 183         return ret;
 184 }
 185
 186 /*
 187  * write the filemap data using writepage() address_space_operations.
 188  * We don't do block allocation here even for delalloc. We don't
 189  * use writepages() because with dealyed allocation we may be doing
 190  * block allocation in writepages().
 191  */
 192 static int journal_submit_inode_data_buffers(struct address_space *mapping)
 193 {
 194         int ret;
 195         struct writeback_control wbc = {
 196                 .sync_mode =  WB_SYNC_ALL,
 197                 .nr_to_write = mapping->nrpages * 2,
 198                 .range_start = 0,
 199                 .range_end = i_size_read(mapping->host),
 200                 .for_writepages = 1,
 201         };
 202
 203         ret = generic_writepages(mapping, &wbc);
 204         return ret;
 205 }
 206
 207 /*
 208  * Submit all the data buffers of inode associated with the transaction to
 209  * disk.
 210  *
 211  * We are in a committing transaction. Therefore no new inode can be added to
 212  * our inode list. We use JI_COMMIT_RUNNING flag to protect inode we currently
 213  * operate on from being released while we write out pages.
 214  */
 215 static int journal_submit_data_buffers(journal_t *journal,
 216                 transaction_t *commit_transaction)
 217 {
 218         struct jbd2_inode *jinode;
 219         int err, ret = 0;
 220         struct address_space *mapping;
 221
 222         spin_lock(&journal->j_list_lock);
 223         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 224                 mapping = jinode->i_vfs_inode->i_mapping;
 225                 jinode->i_flags |= JI_COMMIT_RUNNING;
 226                 spin_unlock(&journal->j_list_lock);
 227                 /*
 228                  * submit the inode data buffers. We use writepage
 229                  * instead of writepages. Because writepages can do
 230                  * block allocation  with delalloc. We need to write
 231                  * only allocated blocks here.
 232                  */
 233                 err = journal_submit_inode_data_buffers(mapping);
 234                 if (!ret)
 235                         ret = err;
 236                 spin_lock(&journal->j_list_lock);
 237                 J_ASSERT(jinode->i_transaction == commit_transaction);
 238                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 239                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 240         }
 241         spin_unlock(&journal->j_list_lock);
 242         return ret;
 243 }
 244
 245 /*
 246  * Wait for data submitted for writeout, refile inodes to proper
 247  * transaction if needed.
 248  *
 249  */
 250 static int journal_finish_inode_data_buffers(journal_t *journal,
 251                 transaction_t *commit_transaction)
 252 {
 253         struct jbd2_inode *jinode, *next_i;
 254         int err, ret = 0;
 255
 256         /* For locking, see the comment in journal_submit_data_buffers() */
 257         spin_lock(&journal->j_list_lock);
 258         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 259                 jinode->i_flags |= JI_COMMIT_RUNNING;
 260                 spin_unlock(&journal->j_list_lock);
 261                 err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
 262                 if (err) {
 263                         /*
 264                          * Because AS_EIO is cleared by
 265                          * wait_on_page_writeback_range(), set it again so
 266                          * that user process can get -EIO from fsync().
 267                          */
 268                         set_bit(AS_EIO,
 269                                 &jinode->i_vfs_inode->i_mapping->flags);
 270
 271                         if (!ret)
 272                                 ret = err;
 273                 }
 274                 spin_lock(&journal->j_list_lock);
 275                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 276                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 277         }
 278
 279         /* Now refile inode to proper lists */
 280         list_for_each_entry_safe(jinode, next_i,
 281                                  &commit_transaction->t_inode_list, i_list) {
 282                 list_del(&jinode->i_list);
 283                 if (jinode->i_next_transaction) {
 284                         jinode->i_transaction = jinode->i_next_transaction;
 285                         jinode->i_next_transaction = NULL;
 286                         list_add(&jinode->i_list,
 287                                 &jinode->i_transaction->t_inode_list);
 288                 } else {
 289                         jinode->i_transaction = NULL;
 290                 }
 291         }
 292         spin_unlock(&journal->j_list_lock);
 293
 294         return ret;
 295 }
 296
 297 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 298 {
 299         struct page *page = bh->b_page;
 300         char *addr;
 301         __u32 checksum;
 302
 303         addr = kmap_atomic(page, KM_USER0);
 304         checksum = crc32_be(crc32_sum,
 305                 (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
 306         kunmap_atomic(addr, KM_USER0);
 307
 308         return checksum;
 309 }
 310
 311 static void write_tag_block(int tag_bytes, journal_block_tag_t *tag,
 312                                    unsigned long long block)
 313 {
 314         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
 315         if (tag_bytes > JBD2_TAG_SIZE32)
 316                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
 317 }
 318
 319 /*
 320  * jbd2_journal_commit_transaction
 321  *
 322  * The primary function for committing a transaction to the log.  This
 323  * function is called by the journal thread to begin a complete commit.
 324  */
 325 void jbd2_journal_commit_transaction(journal_t *journal)
 326 {
 327         struct transaction_stats_s stats;
 328         transaction_t *commit_transaction;
 329         struct journal_head *jh, *new_jh, *descriptor;
 330         struct buffer_head **wbuf = journal->j_wbuf;
 331         int bufs;
 332         int flags;
 333         int err;
 334         unsigned long long blocknr;
 335         char *tagp = NULL;
 336         journal_header_t *header;
 337         journal_block_tag_t *tag = NULL;
 338         int space_left = 0;
 339         int first_tag = 0;
 340         int tag_flag;
 341         int i;
 342         int tag_bytes = journal_tag_bytes(journal);
 343         struct buffer_head *cbh = NULL; /* For transactional checksums */
 344         __u32 crc32_sum = ~0;
 345
 346         /*
 347          * First job: lock down the current transaction and wait for
 348          * all outstanding updates to complete.
 349          */
 350
 351 #ifdef COMMIT_STATS
 352         spin_lock(&journal->j_list_lock);
 353         summarise_journal_usage(journal);
 354         spin_unlock(&journal->j_list_lock);
 355 #endif
 356
 357         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 358         if (journal->j_flags & JBD2_FLUSHED) {
 359                 jbd_debug(3, "super block updated\n");
 360                 jbd2_journal_update_superblock(journal, 1);
 361         } else {
 362                 jbd_debug(3, "superblock not updated\n");
 363         }
 364
 365         J_ASSERT(journal->j_running_transaction != NULL);
 366         J_ASSERT(journal->j_committing_transaction == NULL);
 367
 368         commit_transaction = journal->j_running_transaction;
 369         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 370
 371         trace_mark(jbd2_start_commit, "dev %s transaction %d",
 372                    journal->j_devname, commit_transaction->t_tid);
 373         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 374                         commit_transaction->t_tid);
 375
 376         spin_lock(&journal->j_state_lock);
 377         commit_transaction->t_state = T_LOCKED;
 378
 379         stats.u.run.rs_wait = commit_transaction->t_max_wait;
 380         stats.u.run.rs_locked = jiffies;
 381         stats.u.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 382                                                 stats.u.run.rs_locked);
 383
 384         spin_lock(&commit_transaction->t_handle_lock);
 385         while (commit_transaction->t_updates) {
 386                 DEFINE_WAIT(wait);
 387
 388                 prepare_to_wait(&journal->j_wait_updates, &wait,
 389                                         TASK_UNINTERRUPTIBLE);
 390                 if (commit_transaction->t_updates) {
 391                         spin_unlock(&commit_transaction->t_handle_lock);
 392                         spin_unlock(&journal->j_state_lock);
 393                         schedule();
 394                         spin_lock(&journal->j_state_lock);
 395                         spin_lock(&commit_transaction->t_handle_lock);
 396                 }
 397                 finish_wait(&journal->j_wait_updates, &wait);
 398         }
 399         spin_unlock(&commit_transaction->t_handle_lock);
 400
 401         J_ASSERT (commit_transaction->t_outstanding_credits <=
 402                         journal->j_max_transaction_buffers);
 403
 404         /*
 405          * First thing we are allowed to do is to discard any remaining
 406          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 407          * that there are no such buffers: if a large filesystem
 408          * operation like a truncate needs to split itself over multiple
 409          * transactions, then it may try to do a jbd2_journal_restart() while
 410          * there are still BJ_Reserved buffers outstanding.  These must
 411          * be released cleanly from the current transaction.
 412          *
 413          * In this case, the filesystem must still reserve write access
 414          * again before modifying the buffer in the new transaction, but
 415          * we do not require it to remember exactly which old buffers it
 416          * has reserved.  This is consistent with the existing behaviour
 417          * that multiple jbd2_journal_get_write_access() calls to the same
 418          * buffer are perfectly permissable.
 419          */
 420         while (commit_transaction->t_reserved_list) {
 421                 jh = commit_transaction->t_reserved_list;
 422                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 423                 /*
 424                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 425                  * leave undo-committed data.
 426                  */
 427                 if (jh->b_committed_data) {
 428                         struct buffer_head *bh = jh2bh(jh);
 429
 430                         jbd_lock_bh_state(bh);
 431                         jbd2_free(jh->b_committed_data, bh->b_size);
 432                         jh->b_committed_data = NULL;
 433                         jbd_unlock_bh_state(bh);
 434                 }
 435                 jbd2_journal_refile_buffer(journal, jh);
 436         }
 437
 438         /*
 439          * Now try to drop any written-back buffers from the journal's
 440          * checkpoint lists.  We do this *before* commit because it potentially
 441          * frees some memory
 442          */
 443         spin_lock(&journal->j_list_lock);
 444         __jbd2_journal_clean_checkpoint_list(journal);
 445         spin_unlock(&journal->j_list_lock);
 446
 447         jbd_debug (3, "JBD: commit phase 1\n");
 448
 449         /*
 450          * Switch to a new revoke table.
 451          */
 452         jbd2_journal_switch_revoke_table(journal);
 453
 454         stats.u.run.rs_flushing = jiffies;
 455         stats.u.run.rs_locked = jbd2_time_diff(stats.u.run.rs_locked,
 456                                                stats.u.run.rs_flushing);
 457
 458         commit_transaction->t_state = T_FLUSH;
 459         journal->j_committing_transaction = commit_transaction;
 460         journal->j_running_transaction = NULL;
 461         commit_transaction->t_log_start = journal->j_head;
 462         wake_up(&journal->j_wait_transaction_locked);
 463         spin_unlock(&journal->j_state_lock);
 464
 465         jbd_debug (3, "JBD: commit phase 2\n");
 466
 467         /*
 468          * Now start flushing things to disk, in the order they appear
 469          * on the transaction lists.  Data blocks go first.
 470          */
 471         err = journal_submit_data_buffers(journal, commit_transaction);
 472         if (err)
 473                 jbd2_journal_abort(journal, err);
 474
 475         jbd2_journal_write_revoke_records(journal, commit_transaction);
 476
 477         jbd_debug(3, "JBD: commit phase 2\n");
 478
 479         /*
 480          * Way to go: we have now written out all of the data for a
 481          * transaction!  Now comes the tricky part: we need to write out
 482          * metadata.  Loop over the transaction's entire buffer list:
 483          */
 484         spin_lock(&journal->j_state_lock);
 485         commit_transaction->t_state = T_COMMIT;
 486         spin_unlock(&journal->j_state_lock);
 487
 488         stats.u.run.rs_logging = jiffies;
 489         stats.u.run.rs_flushing = jbd2_time_diff(stats.u.run.rs_flushing,
 490                                                  stats.u.run.rs_logging);
 491         stats.u.run.rs_blocks = commit_transaction->t_outstanding_credits;
 492         stats.u.run.rs_blocks_logged = 0;
 493
 494         J_ASSERT(commit_transaction->t_nr_buffers <=
 495                  commit_transaction->t_outstanding_credits);
 496
 497         err = 0;
 498         descriptor = NULL;
 499         bufs = 0;
 500         while (commit_transaction->t_buffers) {
 501
 502                 /* Find the next buffer to be journaled... */
 503
 504                 jh = commit_transaction->t_buffers;
 505
 506                 /* If we're in abort mode, we just un-journal the buffer and
 507                    release it. */
 508
 509                 if (is_journal_aborted(journal)) {
 510                         clear_buffer_jbddirty(jh2bh(jh));
 511                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 512                         jbd2_buffer_abort_trigger(jh,
 513                                                   jh->b_frozen_data ?
 514                                                   jh->b_frozen_triggers :
 515                                                   jh->b_triggers);
 516                         jbd2_journal_refile_buffer(journal, jh);
 517                         /* If that was the last one, we need to clean up
 518                          * any descriptor buffers which may have been
 519                          * already allocated, even if we are now
 520                          * aborting. */
 521                         if (!commit_transaction->t_buffers)
 522                                 goto start_journal_io;
 523                         continue;
 524                 }
 525
 526                 /* Make sure we have a descriptor block in which to
 527                    record the metadata buffer. */
 528
 529                 if (!descriptor) {
 530                         struct buffer_head *bh;
 531
 532                         J_ASSERT (bufs == 0);
 533
 534                         jbd_debug(4, "JBD: get descriptor\n");
 535
 536                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 537                         if (!descriptor) {
 538                                 jbd2_journal_abort(journal, -EIO);
 539                                 continue;
 540                         }
 541
 542                         bh = jh2bh(descriptor);
 543                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 544                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 545                         header = (journal_header_t *)&bh->b_data[0];
 546                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 547                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 548                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 549
 550                         tagp = &bh->b_data[sizeof(journal_header_t)];
 551                         space_left = bh->b_size - sizeof(journal_header_t);
 552                         first_tag = 1;
 553                         set_buffer_jwrite(bh);
 554                         set_buffer_dirty(bh);
 555                         wbuf[bufs++] = bh;
 556
 557                         /* Record it so that we can wait for IO
 558                            completion later */
 559                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 560                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 561                                         BJ_LogCtl);
 562                 }
 563
 564                 /* Where is the buffer to be written? */
 565
 566                 err = jbd2_journal_next_log_block(journal, &blocknr);
 567                 /* If the block mapping failed, just abandon the buffer
 568                    and repeat this loop: we'll fall into the
 569                    refile-on-abort condition above. */
 570                 if (err) {
 571                         jbd2_journal_abort(journal, err);
 572                         continue;
 573                 }
 574
 575                 /*
 576                  * start_this_handle() uses t_outstanding_credits to determine
 577                  * the free space in the log, but this counter is changed
 578                  * by jbd2_journal_next_log_block() also.
 579                  */
 580                 commit_transaction->t_outstanding_credits--;
 581
 582                 /* Bump b_count to prevent truncate from stumbling over
 583                    the shadowed buffer!  @@@ This can go if we ever get
 584                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 585                 atomic_inc(&jh2bh(jh)->b_count);
 586
 587                 /* Make a temporary IO buffer with which to write it out
 588                    (this will requeue both the metadata buffer and the
 589                    temporary IO buffer). new_bh goes on BJ_IO*/
 590
 591                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 592                 /*
 593                  * akpm: jbd2_journal_write_metadata_buffer() sets
 594                  * new_bh->b_transaction to commit_transaction.
 595                  * We need to clean this up before we release new_bh
 596                  * (which is of type BJ_IO)
 597                  */
 598                 JBUFFER_TRACE(jh, "ph3: write metadata");
 599                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 600                                                       jh, &new_jh, blocknr);
 601                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 602                 wbuf[bufs++] = jh2bh(new_jh);
 603
 604                 /* Record the new block's tag in the current descriptor
 605                    buffer */
 606
 607                 tag_flag = 0;
 608                 if (flags & 1)
 609                         tag_flag |= JBD2_FLAG_ESCAPE;
 610                 if (!first_tag)
 611                         tag_flag |= JBD2_FLAG_SAME_UUID;
 612
 613                 tag = (journal_block_tag_t *) tagp;
 614                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 615                 tag->t_flags = cpu_to_be32(tag_flag);
 616                 tagp += tag_bytes;
 617                 space_left -= tag_bytes;
 618
 619                 if (first_tag) {
 620                         memcpy (tagp, journal->j_uuid, 16);
 621                         tagp += 16;
 622                         space_left -= 16;
 623                         first_tag = 0;
 624                 }
 625
 626                 /* If there's no more to do, or if the descriptor is full,
 627                    let the IO rip! */
 628
 629                 if (bufs == journal->j_wbufsize ||
 630                     commit_transaction->t_buffers == NULL ||
 631                     space_left < tag_bytes + 16) {
 632
 633                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 634
 635                         /* Write an end-of-descriptor marker before
 636                            submitting the IOs.  "tag" still points to
 637                            the last tag we set up. */
 638
 639                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 640
 641 start_journal_io:
 642                         for (i = 0; i < bufs; i++) {
 643                                 struct buffer_head *bh = wbuf[i];
 644                                 /*
 645                                  * Compute checksum.
 646                                  */
 647                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 648                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 649                                         crc32_sum =
 650                                             jbd2_checksum_data(crc32_sum, bh);
 651                                 }
 652
 653                                 lock_buffer(bh);
 654                                 clear_buffer_dirty(bh);
 655                                 set_buffer_uptodate(bh);
 656                                 bh->b_end_io = journal_end_buffer_io_sync;
 657                                 submit_bh(WRITE, bh);
 658                         }
 659                         cond_resched();
 660                         stats.u.run.rs_blocks_logged += bufs;
 661
 662                         /* Force a new descriptor to be generated next
 663                            time round the loop. */
 664                         descriptor = NULL;
 665                         bufs = 0;
 666                 }
 667         }
 668
 669         /* Done it all: now write the commit record asynchronously. */
 670
 671         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 672                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 673                 err = journal_submit_commit_record(journal, commit_transaction,
 674                                                  &cbh, crc32_sum);
 675                 if (err)
 676                         __jbd2_journal_abort_hard(journal);
 677         }
 678
 679         /*
 680          * This is the right place to wait for data buffers both for ASYNC
 681          * and !ASYNC commit. If commit is ASYNC, we need to wait only after
 682          * the commit block went to disk (which happens above). If commit is
 683          * SYNC, we need to wait for data buffers before we start writing
 684          * commit block, which happens below in such setting.
 685          */
 686         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 687         if (err) {
 688                 printk(KERN_WARNING
 689                         "JBD2: Detected IO errors while flushing file data "
 690                        "on %s\n", journal->j_devname);
 691                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 692                         jbd2_journal_abort(journal, err);
 693                 err = 0;
 694         }
 695
 696         /* Lo and behold: we have just managed to send a transaction to
 697            the log.  Before we can commit it, wait for the IO so far to
 698            complete.  Control buffers being written are on the
 699            transaction's t_log_list queue, and metadata buffers are on
 700            the t_iobuf_list queue.
 701
 702            Wait for the buffers in reverse order.  That way we are
 703            less likely to be woken up until all IOs have completed, and
 704            so we incur less scheduling load.
 705         */
 706
 707         jbd_debug(3, "JBD: commit phase 3\n");
 708
 709         /*
 710          * akpm: these are BJ_IO, and j_list_lock is not needed.
 711          * See __journal_try_to_free_buffer.
 712          */
 713 wait_for_iobuf:
 714         while (commit_transaction->t_iobuf_list != NULL) {
 715                 struct buffer_head *bh;
 716
 717                 jh = commit_transaction->t_iobuf_list->b_tprev;
 718                 bh = jh2bh(jh);
 719                 if (buffer_locked(bh)) {
 720                         wait_on_buffer(bh);
 721                         goto wait_for_iobuf;
 722                 }
 723                 if (cond_resched())
 724                         goto wait_for_iobuf;
 725
 726                 if (unlikely(!buffer_uptodate(bh)))
 727                         err = -EIO;
 728
 729                 clear_buffer_jwrite(bh);
 730
 731                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 732                 jbd2_journal_unfile_buffer(journal, jh);
 733
 734                 /*
 735                  * ->t_iobuf_list should contain only dummy buffer_heads
 736                  * which were created by jbd2_journal_write_metadata_buffer().
 737                  */
 738                 BUFFER_TRACE(bh, "dumping temporary bh");
 739                 jbd2_journal_put_journal_head(jh);
 740                 __brelse(bh);
 741                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 742                 free_buffer_head(bh);
 743
 744                 /* We also have to unlock and free the corresponding
 745                    shadowed buffer */
 746                 jh = commit_transaction->t_shadow_list->b_tprev;
 747                 bh = jh2bh(jh);
 748                 clear_bit(BH_JWrite, &bh->b_state);
 749                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 750
 751                 /* The metadata is now released for reuse, but we need
 752                    to remember it against this transaction so that when
 753                    we finally commit, we can do any checkpointing
 754                    required. */
 755                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 756                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 757                 /* Wake up any transactions which were waiting for this
 758                    IO to complete */
 759                 wake_up_bit(&bh->b_state, BH_Unshadow);
 760                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 761                 __brelse(bh);
 762         }
 763
 764         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 765
 766         jbd_debug(3, "JBD: commit phase 4\n");
 767
 768         /* Here we wait for the revoke record and descriptor record buffers */
 769  wait_for_ctlbuf:
 770         while (commit_transaction->t_log_list != NULL) {
 771                 struct buffer_head *bh;
 772
 773                 jh = commit_transaction->t_log_list->b_tprev;
 774                 bh = jh2bh(jh);
 775                 if (buffer_locked(bh)) {
 776                         wait_on_buffer(bh);
 777                         goto wait_for_ctlbuf;
 778                 }
 779                 if (cond_resched())
 780                         goto wait_for_ctlbuf;
 781
 782                 if (unlikely(!buffer_uptodate(bh)))
 783                         err = -EIO;
 784
 785                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 786                 clear_buffer_jwrite(bh);
 787                 jbd2_journal_unfile_buffer(journal, jh);
 788                 jbd2_journal_put_journal_head(jh);
 789                 __brelse(bh);           /* One for getblk */
 790                 /* AKPM: bforget here */
 791         }
 792
 793         if (err)
 794                 jbd2_journal_abort(journal, err);
 795
 796         jbd_debug(3, "JBD: commit phase 5\n");
 797
 798         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 799                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 800                 err = journal_submit_commit_record(journal, commit_transaction,
 801                                                 &cbh, crc32_sum);
 802                 if (err)
 803                         __jbd2_journal_abort_hard(journal);
 804         }
 805         if (!err && !is_journal_aborted(journal))
 806                 err = journal_wait_on_commit_record(cbh);
 807
 808         if (err)
 809                 jbd2_journal_abort(journal, err);
 810
 811         /* End of a transaction!  Finally, we can do checkpoint
 812            processing: any buffers committed as a result of this
 813            transaction can be removed from any checkpoint list it was on
 814            before. */
 815
 816         jbd_debug(3, "JBD: commit phase 6\n");
 817
 818         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 819         J_ASSERT(commit_transaction->t_buffers == NULL);
 820         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 821         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 822         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 823         J_ASSERT(commit_transaction->t_log_list == NULL);
 824
 825 restart_loop:
 826         /*
 827          * As there are other places (journal_unmap_buffer()) adding buffers
 828          * to this list we have to be careful and hold the j_list_lock.
 829          */
 830         spin_lock(&journal->j_list_lock);
 831         while (commit_transaction->t_forget) {
 832                 transaction_t *cp_transaction;
 833                 struct buffer_head *bh;
 834
 835                 jh = commit_transaction->t_forget;
 836                 spin_unlock(&journal->j_list_lock);
 837                 bh = jh2bh(jh);
 838                 jbd_lock_bh_state(bh);
 839                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 840                         jh->b_transaction == journal->j_running_transaction);
 841
 842                 /*
 843                  * If there is undo-protected committed data against
 844                  * this buffer, then we can remove it now.  If it is a
 845                  * buffer needing such protection, the old frozen_data
 846                  * field now points to a committed version of the
 847                  * buffer, so rotate that field to the new committed
 848                  * data.
 849                  *
 850                  * Otherwise, we can just throw away the frozen data now.
 851                  *
 852                  * We also know that the frozen data has already fired
 853                  * its triggers if they exist, so we can clear that too.
 854                  */
 855                 if (jh->b_committed_data) {
 856                         jbd2_free(jh->b_committed_data, bh->b_size);
 857                         jh->b_committed_data = NULL;
 858                         if (jh->b_frozen_data) {
 859                                 jh->b_committed_data = jh->b_frozen_data;
 860                                 jh->b_frozen_data = NULL;
 861                                 jh->b_frozen_triggers = NULL;
 862                         }
 863                 } else if (jh->b_frozen_data) {
 864                         jbd2_free(jh->b_frozen_data, bh->b_size);
 865                         jh->b_frozen_data = NULL;
 866                         jh->b_frozen_triggers = NULL;
 867                 }
 868
 869                 spin_lock(&journal->j_list_lock);
 870                 cp_transaction = jh->b_cp_transaction;
 871                 if (cp_transaction) {
 872                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 873                         cp_transaction->t_chp_stats.cs_dropped++;
 874                         __jbd2_journal_remove_checkpoint(jh);
 875                 }
 876
 877                 /* Only re-checkpoint the buffer_head if it is marked
 878                  * dirty.  If the buffer was added to the BJ_Forget list
 879                  * by jbd2_journal_forget, it may no longer be dirty and
 880                  * there's no point in keeping a checkpoint record for
 881                  * it. */
 882
 883                 /* A buffer which has been freed while still being
 884                  * journaled by a previous transaction may end up still
 885                  * being dirty here, but we want to avoid writing back
 886                  * that buffer in the future now that the last use has
 887                  * been committed.  That's not only a performance gain,
 888                  * it also stops aliasing problems if the buffer is left
 889                  * behind for writeback and gets reallocated for another
 890                  * use in a different page. */
 891                 if (buffer_freed(bh)) {
 892                         clear_buffer_freed(bh);
 893                         clear_buffer_jbddirty(bh);
 894                 }
 895
 896                 if (buffer_jbddirty(bh)) {
 897                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 898                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 899                         if (is_journal_aborted(journal))
 900                                 clear_buffer_jbddirty(bh);
 901                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 902                         __jbd2_journal_refile_buffer(jh);
 903                         jbd_unlock_bh_state(bh);
 904                 } else {
 905                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 906                         /* The buffer on BJ_Forget list and not jbddirty means
 907                          * it has been freed by this transaction and hence it
 908                          * could not have been reallocated until this
 909                          * transaction has committed. *BUT* it could be
 910                          * reallocated once we have written all the data to
 911                          * disk and before we process the buffer on BJ_Forget
 912                          * list. */
 913                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 914                         __jbd2_journal_refile_buffer(jh);
 915                         if (!jh->b_transaction) {
 916                                 jbd_unlock_bh_state(bh);
 917                                  /* needs a brelse */
 918                                 jbd2_journal_remove_journal_head(bh);
 919                                 release_buffer_page(bh);
 920                         } else
 921                                 jbd_unlock_bh_state(bh);
 922                 }
 923                 cond_resched_lock(&journal->j_list_lock);
 924         }
 925         spin_unlock(&journal->j_list_lock);
 926         /*
 927          * This is a bit sleazy.  We use j_list_lock to protect transition
 928          * of a transaction into T_FINISHED state and calling
 929          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 930          * other checkpointing code processing the transaction...
 931          */
 932         spin_lock(&journal->j_state_lock);
 933         spin_lock(&journal->j_list_lock);
 934         /*
 935          * Now recheck if some buffers did not get attached to the transaction
 936          * while the lock was dropped...
 937          */
 938         if (commit_transaction->t_forget) {
 939                 spin_unlock(&journal->j_list_lock);
 940                 spin_unlock(&journal->j_state_lock);
 941                 goto restart_loop;
 942         }
 943
 944         /* Done with this transaction! */
 945
 946         jbd_debug(3, "JBD: commit phase 7\n");
 947
 948         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 949
 950         commit_transaction->t_start = jiffies;
 951         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
 952                                                 commit_transaction->t_start);
 953
 954         /*
 955          * File the transaction for history
 956          */
 957         stats.ts_type = JBD2_STATS_RUN;
 958         stats.ts_tid = commit_transaction->t_tid;
 959         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
 960         spin_lock(&journal->j_history_lock);
 961         memcpy(journal->j_history + journal->j_history_cur, &stats,
 962                         sizeof(stats));
 963         if (++journal->j_history_cur == journal->j_history_max)
 964                 journal->j_history_cur = 0;
 965
 966         /*
 967          * Calculate overall stats
 968          */
 969         journal->j_stats.ts_tid++;
 970         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
 971         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
 972         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
 973         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
 974         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
 975         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
 976         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
 977         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
 978         spin_unlock(&journal->j_history_lock);
 979
 980         commit_transaction->t_state = T_FINISHED;
 981         J_ASSERT(commit_transaction == journal->j_committing_transaction);
 982         journal->j_commit_sequence = commit_transaction->t_tid;
 983         journal->j_committing_transaction = NULL;
 984         spin_unlock(&journal->j_state_lock);
 985
 986         if (journal->j_commit_callback)
 987                 journal->j_commit_callback(journal, commit_transaction);
 988
 989         if (commit_transaction->t_checkpoint_list == NULL &&
 990             commit_transaction->t_checkpoint_io_list == NULL) {
 991                 __jbd2_journal_drop_transaction(journal, commit_transaction);
 992         } else {
 993                 if (journal->j_checkpoint_transactions == NULL) {
 994                         journal->j_checkpoint_transactions = commit_transaction;
 995                         commit_transaction->t_cpnext = commit_transaction;
 996                         commit_transaction->t_cpprev = commit_transaction;
 997                 } else {
 998                         commit_transaction->t_cpnext =
 999                                 journal->j_checkpoint_transactions;
1000                         commit_transaction->t_cpprev =
1001                                 commit_transaction->t_cpnext->t_cpprev;
1002                         commit_transaction->t_cpnext->t_cpprev =
1003                                 commit_transaction;
1004                         commit_transaction->t_cpprev->t_cpnext =
1005                                 commit_transaction;
1006                 }
1007         }
1008         spin_unlock(&journal->j_list_lock);
1009
1010         trace_mark(jbd2_end_commit, "dev %s transaction %d head %d",
1011                    journal->j_devname, journal->j_commit_sequence,
1012                    journal->j_tail_sequence);
1013         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1014                   journal->j_commit_sequence, journal->j_tail_sequence);
1015
1016         wake_up(&journal->j_wait_done_commit);
1017 }