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_journal_refile_buffer(journal, jh);
 513                         /* If that was the last one, we need to clean up
 514                          * any descriptor buffers which may have been
 515                          * already allocated, even if we are now
 516                          * aborting. */
 517                         if (!commit_transaction->t_buffers)
 518                                 goto start_journal_io;
 519                         continue;
 520                 }
 521
 522                 /* Make sure we have a descriptor block in which to
 523                    record the metadata buffer. */
 524
 525                 if (!descriptor) {
 526                         struct buffer_head *bh;
 527
 528                         J_ASSERT (bufs == 0);
 529
 530                         jbd_debug(4, "JBD: get descriptor\n");
 531
 532                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 533                         if (!descriptor) {
 534                                 jbd2_journal_abort(journal, -EIO);
 535                                 continue;
 536                         }
 537
 538                         bh = jh2bh(descriptor);
 539                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 540                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 541                         header = (journal_header_t *)&bh->b_data[0];
 542                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 543                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 544                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 545
 546                         tagp = &bh->b_data[sizeof(journal_header_t)];
 547                         space_left = bh->b_size - sizeof(journal_header_t);
 548                         first_tag = 1;
 549                         set_buffer_jwrite(bh);
 550                         set_buffer_dirty(bh);
 551                         wbuf[bufs++] = bh;
 552
 553                         /* Record it so that we can wait for IO
 554                            completion later */
 555                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 556                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 557                                         BJ_LogCtl);
 558                 }
 559
 560                 /* Where is the buffer to be written? */
 561
 562                 err = jbd2_journal_next_log_block(journal, &blocknr);
 563                 /* If the block mapping failed, just abandon the buffer
 564                    and repeat this loop: we'll fall into the
 565                    refile-on-abort condition above. */
 566                 if (err) {
 567                         jbd2_journal_abort(journal, err);
 568                         continue;
 569                 }
 570
 571                 /*
 572                  * start_this_handle() uses t_outstanding_credits to determine
 573                  * the free space in the log, but this counter is changed
 574                  * by jbd2_journal_next_log_block() also.
 575                  */
 576                 commit_transaction->t_outstanding_credits--;
 577
 578                 /* Bump b_count to prevent truncate from stumbling over
 579                    the shadowed buffer!  @@@ This can go if we ever get
 580                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 581                 atomic_inc(&jh2bh(jh)->b_count);
 582
 583                 /* Make a temporary IO buffer with which to write it out
 584                    (this will requeue both the metadata buffer and the
 585                    temporary IO buffer). new_bh goes on BJ_IO*/
 586
 587                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 588                 /*
 589                  * akpm: jbd2_journal_write_metadata_buffer() sets
 590                  * new_bh->b_transaction to commit_transaction.
 591                  * We need to clean this up before we release new_bh
 592                  * (which is of type BJ_IO)
 593                  */
 594                 JBUFFER_TRACE(jh, "ph3: write metadata");
 595                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 596                                                       jh, &new_jh, blocknr);
 597                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 598                 wbuf[bufs++] = jh2bh(new_jh);
 599
 600                 /* Record the new block's tag in the current descriptor
 601                    buffer */
 602
 603                 tag_flag = 0;
 604                 if (flags & 1)
 605                         tag_flag |= JBD2_FLAG_ESCAPE;
 606                 if (!first_tag)
 607                         tag_flag |= JBD2_FLAG_SAME_UUID;
 608
 609                 tag = (journal_block_tag_t *) tagp;
 610                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 611                 tag->t_flags = cpu_to_be32(tag_flag);
 612                 tagp += tag_bytes;
 613                 space_left -= tag_bytes;
 614
 615                 if (first_tag) {
 616                         memcpy (tagp, journal->j_uuid, 16);
 617                         tagp += 16;
 618                         space_left -= 16;
 619                         first_tag = 0;
 620                 }
 621
 622                 /* If there's no more to do, or if the descriptor is full,
 623                    let the IO rip! */
 624
 625                 if (bufs == journal->j_wbufsize ||
 626                     commit_transaction->t_buffers == NULL ||
 627                     space_left < tag_bytes + 16) {
 628
 629                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 630
 631                         /* Write an end-of-descriptor marker before
 632                            submitting the IOs.  "tag" still points to
 633                            the last tag we set up. */
 634
 635                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 636
 637 start_journal_io:
 638                         for (i = 0; i < bufs; i++) {
 639                                 struct buffer_head *bh = wbuf[i];
 640                                 /*
 641                                  * Compute checksum.
 642                                  */
 643                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 644                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 645                                         crc32_sum =
 646                                             jbd2_checksum_data(crc32_sum, bh);
 647                                 }
 648
 649                                 lock_buffer(bh);
 650                                 clear_buffer_dirty(bh);
 651                                 set_buffer_uptodate(bh);
 652                                 bh->b_end_io = journal_end_buffer_io_sync;
 653                                 submit_bh(WRITE, bh);
 654                         }
 655                         cond_resched();
 656                         stats.u.run.rs_blocks_logged += bufs;
 657
 658                         /* Force a new descriptor to be generated next
 659                            time round the loop. */
 660                         descriptor = NULL;
 661                         bufs = 0;
 662                 }
 663         }
 664
 665         /* Done it all: now write the commit record asynchronously. */
 666
 667         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 668                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 669                 err = journal_submit_commit_record(journal, commit_transaction,
 670                                                  &cbh, crc32_sum);
 671                 if (err)
 672                         __jbd2_journal_abort_hard(journal);
 673         }
 674
 675         /*
 676          * This is the right place to wait for data buffers both for ASYNC
 677          * and !ASYNC commit. If commit is ASYNC, we need to wait only after
 678          * the commit block went to disk (which happens above). If commit is
 679          * SYNC, we need to wait for data buffers before we start writing
 680          * commit block, which happens below in such setting.
 681          */
 682         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 683         if (err) {
 684                 printk(KERN_WARNING
 685                         "JBD2: Detected IO errors while flushing file data "
 686                        "on %s\n", journal->j_devname);
 687                 err = 0;
 688         }
 689
 690         /* Lo and behold: we have just managed to send a transaction to
 691            the log.  Before we can commit it, wait for the IO so far to
 692            complete.  Control buffers being written are on the
 693            transaction's t_log_list queue, and metadata buffers are on
 694            the t_iobuf_list queue.
 695
 696            Wait for the buffers in reverse order.  That way we are
 697            less likely to be woken up until all IOs have completed, and
 698            so we incur less scheduling load.
 699         */
 700
 701         jbd_debug(3, "JBD: commit phase 3\n");
 702
 703         /*
 704          * akpm: these are BJ_IO, and j_list_lock is not needed.
 705          * See __journal_try_to_free_buffer.
 706          */
 707 wait_for_iobuf:
 708         while (commit_transaction->t_iobuf_list != NULL) {
 709                 struct buffer_head *bh;
 710
 711                 jh = commit_transaction->t_iobuf_list->b_tprev;
 712                 bh = jh2bh(jh);
 713                 if (buffer_locked(bh)) {
 714                         wait_on_buffer(bh);
 715                         goto wait_for_iobuf;
 716                 }
 717                 if (cond_resched())
 718                         goto wait_for_iobuf;
 719
 720                 if (unlikely(!buffer_uptodate(bh)))
 721                         err = -EIO;
 722
 723                 clear_buffer_jwrite(bh);
 724
 725                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 726                 jbd2_journal_unfile_buffer(journal, jh);
 727
 728                 /*
 729                  * ->t_iobuf_list should contain only dummy buffer_heads
 730                  * which were created by jbd2_journal_write_metadata_buffer().
 731                  */
 732                 BUFFER_TRACE(bh, "dumping temporary bh");
 733                 jbd2_journal_put_journal_head(jh);
 734                 __brelse(bh);
 735                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 736                 free_buffer_head(bh);
 737
 738                 /* We also have to unlock and free the corresponding
 739                    shadowed buffer */
 740                 jh = commit_transaction->t_shadow_list->b_tprev;
 741                 bh = jh2bh(jh);
 742                 clear_bit(BH_JWrite, &bh->b_state);
 743                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 744
 745                 /* The metadata is now released for reuse, but we need
 746                    to remember it against this transaction so that when
 747                    we finally commit, we can do any checkpointing
 748                    required. */
 749                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 750                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 751                 /* Wake up any transactions which were waiting for this
 752                    IO to complete */
 753                 wake_up_bit(&bh->b_state, BH_Unshadow);
 754                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 755                 __brelse(bh);
 756         }
 757
 758         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 759
 760         jbd_debug(3, "JBD: commit phase 4\n");
 761
 762         /* Here we wait for the revoke record and descriptor record buffers */
 763  wait_for_ctlbuf:
 764         while (commit_transaction->t_log_list != NULL) {
 765                 struct buffer_head *bh;
 766
 767                 jh = commit_transaction->t_log_list->b_tprev;
 768                 bh = jh2bh(jh);
 769                 if (buffer_locked(bh)) {
 770                         wait_on_buffer(bh);
 771                         goto wait_for_ctlbuf;
 772                 }
 773                 if (cond_resched())
 774                         goto wait_for_ctlbuf;
 775
 776                 if (unlikely(!buffer_uptodate(bh)))
 777                         err = -EIO;
 778
 779                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 780                 clear_buffer_jwrite(bh);
 781                 jbd2_journal_unfile_buffer(journal, jh);
 782                 jbd2_journal_put_journal_head(jh);
 783                 __brelse(bh);           /* One for getblk */
 784                 /* AKPM: bforget here */
 785         }
 786
 787         if (err)
 788                 jbd2_journal_abort(journal, err);
 789
 790         jbd_debug(3, "JBD: commit phase 5\n");
 791
 792         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 793                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 794                 err = journal_submit_commit_record(journal, commit_transaction,
 795                                                 &cbh, crc32_sum);
 796                 if (err)
 797                         __jbd2_journal_abort_hard(journal);
 798         }
 799         if (!err && !is_journal_aborted(journal))
 800                 err = journal_wait_on_commit_record(cbh);
 801
 802         if (err)
 803                 jbd2_journal_abort(journal, err);
 804
 805         /* End of a transaction!  Finally, we can do checkpoint
 806            processing: any buffers committed as a result of this
 807            transaction can be removed from any checkpoint list it was on
 808            before. */
 809
 810         jbd_debug(3, "JBD: commit phase 6\n");
 811
 812         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 813         J_ASSERT(commit_transaction->t_buffers == NULL);
 814         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 815         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 816         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 817         J_ASSERT(commit_transaction->t_log_list == NULL);
 818
 819 restart_loop:
 820         /*
 821          * As there are other places (journal_unmap_buffer()) adding buffers
 822          * to this list we have to be careful and hold the j_list_lock.
 823          */
 824         spin_lock(&journal->j_list_lock);
 825         while (commit_transaction->t_forget) {
 826                 transaction_t *cp_transaction;
 827                 struct buffer_head *bh;
 828
 829                 jh = commit_transaction->t_forget;
 830                 spin_unlock(&journal->j_list_lock);
 831                 bh = jh2bh(jh);
 832                 jbd_lock_bh_state(bh);
 833                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 834                         jh->b_transaction == journal->j_running_transaction);
 835
 836                 /*
 837                  * If there is undo-protected committed data against
 838                  * this buffer, then we can remove it now.  If it is a
 839                  * buffer needing such protection, the old frozen_data
 840                  * field now points to a committed version of the
 841                  * buffer, so rotate that field to the new committed
 842                  * data.
 843                  *
 844                  * Otherwise, we can just throw away the frozen data now.
 845                  */
 846                 if (jh->b_committed_data) {
 847                         jbd2_free(jh->b_committed_data, bh->b_size);
 848                         jh->b_committed_data = NULL;
 849                         if (jh->b_frozen_data) {
 850                                 jh->b_committed_data = jh->b_frozen_data;
 851                                 jh->b_frozen_data = NULL;
 852                         }
 853                 } else if (jh->b_frozen_data) {
 854                         jbd2_free(jh->b_frozen_data, bh->b_size);
 855                         jh->b_frozen_data = NULL;
 856                 }
 857
 858                 spin_lock(&journal->j_list_lock);
 859                 cp_transaction = jh->b_cp_transaction;
 860                 if (cp_transaction) {
 861                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 862                         cp_transaction->t_chp_stats.cs_dropped++;
 863                         __jbd2_journal_remove_checkpoint(jh);
 864                 }
 865
 866                 /* Only re-checkpoint the buffer_head if it is marked
 867                  * dirty.  If the buffer was added to the BJ_Forget list
 868                  * by jbd2_journal_forget, it may no longer be dirty and
 869                  * there's no point in keeping a checkpoint record for
 870                  * it. */
 871
 872                 /* A buffer which has been freed while still being
 873                  * journaled by a previous transaction may end up still
 874                  * being dirty here, but we want to avoid writing back
 875                  * that buffer in the future now that the last use has
 876                  * been committed.  That's not only a performance gain,
 877                  * it also stops aliasing problems if the buffer is left
 878                  * behind for writeback and gets reallocated for another
 879                  * use in a different page. */
 880                 if (buffer_freed(bh)) {
 881                         clear_buffer_freed(bh);
 882                         clear_buffer_jbddirty(bh);
 883                 }
 884
 885                 if (buffer_jbddirty(bh)) {
 886                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 887                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 888                         if (is_journal_aborted(journal))
 889                                 clear_buffer_jbddirty(bh);
 890                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 891                         __jbd2_journal_refile_buffer(jh);
 892                         jbd_unlock_bh_state(bh);
 893                 } else {
 894                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 895                         /* The buffer on BJ_Forget list and not jbddirty means
 896                          * it has been freed by this transaction and hence it
 897                          * could not have been reallocated until this
 898                          * transaction has committed. *BUT* it could be
 899                          * reallocated once we have written all the data to
 900                          * disk and before we process the buffer on BJ_Forget
 901                          * list. */
 902                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 903                         __jbd2_journal_refile_buffer(jh);
 904                         if (!jh->b_transaction) {
 905                                 jbd_unlock_bh_state(bh);
 906                                  /* needs a brelse */
 907                                 jbd2_journal_remove_journal_head(bh);
 908                                 release_buffer_page(bh);
 909                         } else
 910                                 jbd_unlock_bh_state(bh);
 911                 }
 912                 cond_resched_lock(&journal->j_list_lock);
 913         }
 914         spin_unlock(&journal->j_list_lock);
 915         /*
 916          * This is a bit sleazy.  We use j_list_lock to protect transition
 917          * of a transaction into T_FINISHED state and calling
 918          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 919          * other checkpointing code processing the transaction...
 920          */
 921         spin_lock(&journal->j_state_lock);
 922         spin_lock(&journal->j_list_lock);
 923         /*
 924          * Now recheck if some buffers did not get attached to the transaction
 925          * while the lock was dropped...
 926          */
 927         if (commit_transaction->t_forget) {
 928                 spin_unlock(&journal->j_list_lock);
 929                 spin_unlock(&journal->j_state_lock);
 930                 goto restart_loop;
 931         }
 932
 933         /* Done with this transaction! */
 934
 935         jbd_debug(3, "JBD: commit phase 7\n");
 936
 937         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 938
 939         commit_transaction->t_start = jiffies;
 940         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
 941                                                 commit_transaction->t_start);
 942
 943         /*
 944          * File the transaction for history
 945          */
 946         stats.ts_type = JBD2_STATS_RUN;
 947         stats.ts_tid = commit_transaction->t_tid;
 948         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
 949         spin_lock(&journal->j_history_lock);
 950         memcpy(journal->j_history + journal->j_history_cur, &stats,
 951                         sizeof(stats));
 952         if (++journal->j_history_cur == journal->j_history_max)
 953                 journal->j_history_cur = 0;
 954
 955         /*
 956          * Calculate overall stats
 957          */
 958         journal->j_stats.ts_tid++;
 959         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
 960         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
 961         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
 962         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
 963         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
 964         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
 965         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
 966         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
 967         spin_unlock(&journal->j_history_lock);
 968
 969         commit_transaction->t_state = T_FINISHED;
 970         J_ASSERT(commit_transaction == journal->j_committing_transaction);
 971         journal->j_commit_sequence = commit_transaction->t_tid;
 972         journal->j_committing_transaction = NULL;
 973         spin_unlock(&journal->j_state_lock);
 974
 975         if (commit_transaction->t_checkpoint_list == NULL &&
 976             commit_transaction->t_checkpoint_io_list == NULL) {
 977                 __jbd2_journal_drop_transaction(journal, commit_transaction);
 978         } else {
 979                 if (journal->j_checkpoint_transactions == NULL) {
 980                         journal->j_checkpoint_transactions = commit_transaction;
 981                         commit_transaction->t_cpnext = commit_transaction;
 982                         commit_transaction->t_cpprev = commit_transaction;
 983                 } else {
 984                         commit_transaction->t_cpnext =
 985                                 journal->j_checkpoint_transactions;
 986                         commit_transaction->t_cpprev =
 987                                 commit_transaction->t_cpnext->t_cpprev;
 988                         commit_transaction->t_cpnext->t_cpprev =
 989                                 commit_transaction;
 990                         commit_transaction->t_cpprev->t_cpnext =
 991                                 commit_transaction;
 992                 }
 993         }
 994         spin_unlock(&journal->j_list_lock);
 995
 996         trace_mark(jbd2_end_commit, "dev %s transaction %d head %d",
 997                    journal->j_devname, commit_transaction->t_tid,
 998                    journal->j_tail_sequence);
 999         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1000                   journal->j_commit_sequence, journal->j_tail_sequence);
1001
1002         wake_up(&journal->j_wait_done_commit);
1003 }