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   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                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 688                         jbd2_journal_abort(journal, err);
 689                 err = 0;
 690         }
 691
 692         /* Lo and behold: we have just managed to send a transaction to
 693            the log.  Before we can commit it, wait for the IO so far to
 694            complete.  Control buffers being written are on the
 695            transaction's t_log_list queue, and metadata buffers are on
 696            the t_iobuf_list queue.
 697
 698            Wait for the buffers in reverse order.  That way we are
 699            less likely to be woken up until all IOs have completed, and
 700            so we incur less scheduling load.
 701         */
 702
 703         jbd_debug(3, "JBD: commit phase 3\n");
 704
 705         /*
 706          * akpm: these are BJ_IO, and j_list_lock is not needed.
 707          * See __journal_try_to_free_buffer.
 708          */
 709 wait_for_iobuf:
 710         while (commit_transaction->t_iobuf_list != NULL) {
 711                 struct buffer_head *bh;
 712
 713                 jh = commit_transaction->t_iobuf_list->b_tprev;
 714                 bh = jh2bh(jh);
 715                 if (buffer_locked(bh)) {
 716                         wait_on_buffer(bh);
 717                         goto wait_for_iobuf;
 718                 }
 719                 if (cond_resched())
 720                         goto wait_for_iobuf;
 721
 722                 if (unlikely(!buffer_uptodate(bh)))
 723                         err = -EIO;
 724
 725                 clear_buffer_jwrite(bh);
 726
 727                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 728                 jbd2_journal_unfile_buffer(journal, jh);
 729
 730                 /*
 731                  * ->t_iobuf_list should contain only dummy buffer_heads
 732                  * which were created by jbd2_journal_write_metadata_buffer().
 733                  */
 734                 BUFFER_TRACE(bh, "dumping temporary bh");
 735                 jbd2_journal_put_journal_head(jh);
 736                 __brelse(bh);
 737                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 738                 free_buffer_head(bh);
 739
 740                 /* We also have to unlock and free the corresponding
 741                    shadowed buffer */
 742                 jh = commit_transaction->t_shadow_list->b_tprev;
 743                 bh = jh2bh(jh);
 744                 clear_bit(BH_JWrite, &bh->b_state);
 745                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 746
 747                 /* The metadata is now released for reuse, but we need
 748                    to remember it against this transaction so that when
 749                    we finally commit, we can do any checkpointing
 750                    required. */
 751                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 752                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 753                 /* Wake up any transactions which were waiting for this
 754                    IO to complete */
 755                 wake_up_bit(&bh->b_state, BH_Unshadow);
 756                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 757                 __brelse(bh);
 758         }
 759
 760         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 761
 762         jbd_debug(3, "JBD: commit phase 4\n");
 763
 764         /* Here we wait for the revoke record and descriptor record buffers */
 765  wait_for_ctlbuf:
 766         while (commit_transaction->t_log_list != NULL) {
 767                 struct buffer_head *bh;
 768
 769                 jh = commit_transaction->t_log_list->b_tprev;
 770                 bh = jh2bh(jh);
 771                 if (buffer_locked(bh)) {
 772                         wait_on_buffer(bh);
 773                         goto wait_for_ctlbuf;
 774                 }
 775                 if (cond_resched())
 776                         goto wait_for_ctlbuf;
 777
 778                 if (unlikely(!buffer_uptodate(bh)))
 779                         err = -EIO;
 780
 781                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 782                 clear_buffer_jwrite(bh);
 783                 jbd2_journal_unfile_buffer(journal, jh);
 784                 jbd2_journal_put_journal_head(jh);
 785                 __brelse(bh);           /* One for getblk */
 786                 /* AKPM: bforget here */
 787         }
 788
 789         if (err)
 790                 jbd2_journal_abort(journal, err);
 791
 792         jbd_debug(3, "JBD: commit phase 5\n");
 793
 794         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 795                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 796                 err = journal_submit_commit_record(journal, commit_transaction,
 797                                                 &cbh, crc32_sum);
 798                 if (err)
 799                         __jbd2_journal_abort_hard(journal);
 800         }
 801         if (!err && !is_journal_aborted(journal))
 802                 err = journal_wait_on_commit_record(cbh);
 803
 804         if (err)
 805                 jbd2_journal_abort(journal, err);
 806
 807         /* End of a transaction!  Finally, we can do checkpoint
 808            processing: any buffers committed as a result of this
 809            transaction can be removed from any checkpoint list it was on
 810            before. */
 811
 812         jbd_debug(3, "JBD: commit phase 6\n");
 813
 814         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 815         J_ASSERT(commit_transaction->t_buffers == NULL);
 816         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 817         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 818         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 819         J_ASSERT(commit_transaction->t_log_list == NULL);
 820
 821 restart_loop:
 822         /*
 823          * As there are other places (journal_unmap_buffer()) adding buffers
 824          * to this list we have to be careful and hold the j_list_lock.
 825          */
 826         spin_lock(&journal->j_list_lock);
 827         while (commit_transaction->t_forget) {
 828                 transaction_t *cp_transaction;
 829                 struct buffer_head *bh;
 830
 831                 jh = commit_transaction->t_forget;
 832                 spin_unlock(&journal->j_list_lock);
 833                 bh = jh2bh(jh);
 834                 jbd_lock_bh_state(bh);
 835                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 836                         jh->b_transaction == journal->j_running_transaction);
 837
 838                 /*
 839                  * If there is undo-protected committed data against
 840                  * this buffer, then we can remove it now.  If it is a
 841                  * buffer needing such protection, the old frozen_data
 842                  * field now points to a committed version of the
 843                  * buffer, so rotate that field to the new committed
 844                  * data.
 845                  *
 846                  * Otherwise, we can just throw away the frozen data now.
 847                  */
 848                 if (jh->b_committed_data) {
 849                         jbd2_free(jh->b_committed_data, bh->b_size);
 850                         jh->b_committed_data = NULL;
 851                         if (jh->b_frozen_data) {
 852                                 jh->b_committed_data = jh->b_frozen_data;
 853                                 jh->b_frozen_data = NULL;
 854                         }
 855                 } else if (jh->b_frozen_data) {
 856                         jbd2_free(jh->b_frozen_data, bh->b_size);
 857                         jh->b_frozen_data = NULL;
 858                 }
 859
 860                 spin_lock(&journal->j_list_lock);
 861                 cp_transaction = jh->b_cp_transaction;
 862                 if (cp_transaction) {
 863                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 864                         cp_transaction->t_chp_stats.cs_dropped++;
 865                         __jbd2_journal_remove_checkpoint(jh);
 866                 }
 867
 868                 /* Only re-checkpoint the buffer_head if it is marked
 869                  * dirty.  If the buffer was added to the BJ_Forget list
 870                  * by jbd2_journal_forget, it may no longer be dirty and
 871                  * there's no point in keeping a checkpoint record for
 872                  * it. */
 873
 874                 /* A buffer which has been freed while still being
 875                  * journaled by a previous transaction may end up still
 876                  * being dirty here, but we want to avoid writing back
 877                  * that buffer in the future now that the last use has
 878                  * been committed.  That's not only a performance gain,
 879                  * it also stops aliasing problems if the buffer is left
 880                  * behind for writeback and gets reallocated for another
 881                  * use in a different page. */
 882                 if (buffer_freed(bh)) {
 883                         clear_buffer_freed(bh);
 884                         clear_buffer_jbddirty(bh);
 885                 }
 886
 887                 if (buffer_jbddirty(bh)) {
 888                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 889                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 890                         if (is_journal_aborted(journal))
 891                                 clear_buffer_jbddirty(bh);
 892                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 893                         __jbd2_journal_refile_buffer(jh);
 894                         jbd_unlock_bh_state(bh);
 895                 } else {
 896                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 897                         /* The buffer on BJ_Forget list and not jbddirty means
 898                          * it has been freed by this transaction and hence it
 899                          * could not have been reallocated until this
 900                          * transaction has committed. *BUT* it could be
 901                          * reallocated once we have written all the data to
 902                          * disk and before we process the buffer on BJ_Forget
 903                          * list. */
 904                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 905                         __jbd2_journal_refile_buffer(jh);
 906                         if (!jh->b_transaction) {
 907                                 jbd_unlock_bh_state(bh);
 908                                  /* needs a brelse */
 909                                 jbd2_journal_remove_journal_head(bh);
 910                                 release_buffer_page(bh);
 911                         } else
 912                                 jbd_unlock_bh_state(bh);
 913                 }
 914                 cond_resched_lock(&journal->j_list_lock);
 915         }
 916         spin_unlock(&journal->j_list_lock);
 917         /*
 918          * This is a bit sleazy.  We use j_list_lock to protect transition
 919          * of a transaction into T_FINISHED state and calling
 920          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 921          * other checkpointing code processing the transaction...
 922          */
 923         spin_lock(&journal->j_state_lock);
 924         spin_lock(&journal->j_list_lock);
 925         /*
 926          * Now recheck if some buffers did not get attached to the transaction
 927          * while the lock was dropped...
 928          */
 929         if (commit_transaction->t_forget) {
 930                 spin_unlock(&journal->j_list_lock);
 931                 spin_unlock(&journal->j_state_lock);
 932                 goto restart_loop;
 933         }
 934
 935         /* Done with this transaction! */
 936
 937         jbd_debug(3, "JBD: commit phase 7\n");
 938
 939         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 940
 941         commit_transaction->t_start = jiffies;
 942         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
 943                                                 commit_transaction->t_start);
 944
 945         /*
 946          * File the transaction for history
 947          */
 948         stats.ts_type = JBD2_STATS_RUN;
 949         stats.ts_tid = commit_transaction->t_tid;
 950         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
 951         spin_lock(&journal->j_history_lock);
 952         memcpy(journal->j_history + journal->j_history_cur, &stats,
 953                         sizeof(stats));
 954         if (++journal->j_history_cur == journal->j_history_max)
 955                 journal->j_history_cur = 0;
 956
 957         /*
 958          * Calculate overall stats
 959          */
 960         journal->j_stats.ts_tid++;
 961         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
 962         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
 963         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
 964         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
 965         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
 966         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
 967         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
 968         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
 969         spin_unlock(&journal->j_history_lock);
 970
 971         commit_transaction->t_state = T_FINISHED;
 972         J_ASSERT(commit_transaction == journal->j_committing_transaction);
 973         journal->j_commit_sequence = commit_transaction->t_tid;
 974         journal->j_committing_transaction = NULL;
 975         spin_unlock(&journal->j_state_lock);
 976
 977         if (journal->j_commit_callback)
 978                 journal->j_commit_callback(journal, commit_transaction);
 979
 980         if (commit_transaction->t_checkpoint_list == NULL &&
 981             commit_transaction->t_checkpoint_io_list == NULL) {
 982                 __jbd2_journal_drop_transaction(journal, commit_transaction);
 983         } else {
 984                 if (journal->j_checkpoint_transactions == NULL) {
 985                         journal->j_checkpoint_transactions = commit_transaction;
 986                         commit_transaction->t_cpnext = commit_transaction;
 987                         commit_transaction->t_cpprev = commit_transaction;
 988                 } else {
 989                         commit_transaction->t_cpnext =
 990                                 journal->j_checkpoint_transactions;
 991                         commit_transaction->t_cpprev =
 992                                 commit_transaction->t_cpnext->t_cpprev;
 993                         commit_transaction->t_cpnext->t_cpprev =
 994                                 commit_transaction;
 995                         commit_transaction->t_cpprev->t_cpnext =
 996                                 commit_transaction;
 997                 }
 998         }
 999         spin_unlock(&journal->j_list_lock);
1000
1001         trace_mark(jbd2_end_commit, "dev %s transaction %d head %d",
1002                    journal->j_devname, journal->j_commit_sequence,
1003                    journal->j_tail_sequence);
1004         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1005                   journal->j_commit_sequence, journal->j_tail_sequence);
1006
1007         wake_up(&journal->j_wait_done_commit);
1008 }