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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 for background writing. */
 508
 509                 if (is_journal_aborted(journal)) {
 510                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 511                         jbd2_journal_refile_buffer(journal, jh);
 512                         /* If that was the last one, we need to clean up
 513                          * any descriptor buffers which may have been
 514                          * already allocated, even if we are now
 515                          * aborting. */
 516                         if (!commit_transaction->t_buffers)
 517                                 goto start_journal_io;
 518                         continue;
 519                 }
 520
 521                 /* Make sure we have a descriptor block in which to
 522                    record the metadata buffer. */
 523
 524                 if (!descriptor) {
 525                         struct buffer_head *bh;
 526
 527                         J_ASSERT (bufs == 0);
 528
 529                         jbd_debug(4, "JBD: get descriptor\n");
 530
 531                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 532                         if (!descriptor) {
 533                                 jbd2_journal_abort(journal, -EIO);
 534                                 continue;
 535                         }
 536
 537                         bh = jh2bh(descriptor);
 538                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 539                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 540                         header = (journal_header_t *)&bh->b_data[0];
 541                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 542                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 543                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 544
 545                         tagp = &bh->b_data[sizeof(journal_header_t)];
 546                         space_left = bh->b_size - sizeof(journal_header_t);
 547                         first_tag = 1;
 548                         set_buffer_jwrite(bh);
 549                         set_buffer_dirty(bh);
 550                         wbuf[bufs++] = bh;
 551
 552                         /* Record it so that we can wait for IO
 553                            completion later */
 554                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 555                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 556                                         BJ_LogCtl);
 557                 }
 558
 559                 /* Where is the buffer to be written? */
 560
 561                 err = jbd2_journal_next_log_block(journal, &blocknr);
 562                 /* If the block mapping failed, just abandon the buffer
 563                    and repeat this loop: we'll fall into the
 564                    refile-on-abort condition above. */
 565                 if (err) {
 566                         jbd2_journal_abort(journal, err);
 567                         continue;
 568                 }
 569
 570                 /*
 571                  * start_this_handle() uses t_outstanding_credits to determine
 572                  * the free space in the log, but this counter is changed
 573                  * by jbd2_journal_next_log_block() also.
 574                  */
 575                 commit_transaction->t_outstanding_credits--;
 576
 577                 /* Bump b_count to prevent truncate from stumbling over
 578                    the shadowed buffer!  @@@ This can go if we ever get
 579                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 580                 atomic_inc(&jh2bh(jh)->b_count);
 581
 582                 /* Make a temporary IO buffer with which to write it out
 583                    (this will requeue both the metadata buffer and the
 584                    temporary IO buffer). new_bh goes on BJ_IO*/
 585
 586                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 587                 /*
 588                  * akpm: jbd2_journal_write_metadata_buffer() sets
 589                  * new_bh->b_transaction to commit_transaction.
 590                  * We need to clean this up before we release new_bh
 591                  * (which is of type BJ_IO)
 592                  */
 593                 JBUFFER_TRACE(jh, "ph3: write metadata");
 594                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 595                                                       jh, &new_jh, blocknr);
 596                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 597                 wbuf[bufs++] = jh2bh(new_jh);
 598
 599                 /* Record the new block's tag in the current descriptor
 600                    buffer */
 601
 602                 tag_flag = 0;
 603                 if (flags & 1)
 604                         tag_flag |= JBD2_FLAG_ESCAPE;
 605                 if (!first_tag)
 606                         tag_flag |= JBD2_FLAG_SAME_UUID;
 607
 608                 tag = (journal_block_tag_t *) tagp;
 609                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 610                 tag->t_flags = cpu_to_be32(tag_flag);
 611                 tagp += tag_bytes;
 612                 space_left -= tag_bytes;
 613
 614                 if (first_tag) {
 615                         memcpy (tagp, journal->j_uuid, 16);
 616                         tagp += 16;
 617                         space_left -= 16;
 618                         first_tag = 0;
 619                 }
 620
 621                 /* If there's no more to do, or if the descriptor is full,
 622                    let the IO rip! */
 623
 624                 if (bufs == journal->j_wbufsize ||
 625                     commit_transaction->t_buffers == NULL ||
 626                     space_left < tag_bytes + 16) {
 627
 628                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 629
 630                         /* Write an end-of-descriptor marker before
 631                            submitting the IOs.  "tag" still points to
 632                            the last tag we set up. */
 633
 634                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 635
 636 start_journal_io:
 637                         for (i = 0; i < bufs; i++) {
 638                                 struct buffer_head *bh = wbuf[i];
 639                                 /*
 640                                  * Compute checksum.
 641                                  */
 642                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 643                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 644                                         crc32_sum =
 645                                             jbd2_checksum_data(crc32_sum, bh);
 646                                 }
 647
 648                                 lock_buffer(bh);
 649                                 clear_buffer_dirty(bh);
 650                                 set_buffer_uptodate(bh);
 651                                 bh->b_end_io = journal_end_buffer_io_sync;
 652                                 submit_bh(WRITE, bh);
 653                         }
 654                         cond_resched();
 655                         stats.u.run.rs_blocks_logged += bufs;
 656
 657                         /* Force a new descriptor to be generated next
 658                            time round the loop. */
 659                         descriptor = NULL;
 660                         bufs = 0;
 661                 }
 662         }
 663
 664         /* Done it all: now write the commit record asynchronously. */
 665
 666         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 667                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 668                 err = journal_submit_commit_record(journal, commit_transaction,
 669                                                  &cbh, crc32_sum);
 670                 if (err)
 671                         __jbd2_journal_abort_hard(journal);
 672         }
 673
 674         /*
 675          * This is the right place to wait for data buffers both for ASYNC
 676          * and !ASYNC commit. If commit is ASYNC, we need to wait only after
 677          * the commit block went to disk (which happens above). If commit is
 678          * SYNC, we need to wait for data buffers before we start writing
 679          * commit block, which happens below in such setting.
 680          */
 681         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 682         if (err) {
 683                 printk(KERN_WARNING
 684                         "JBD2: Detected IO errors while flushing file data "
 685                        "on %s\n", journal->j_devname);
 686                 err = 0;
 687         }
 688
 689         /* Lo and behold: we have just managed to send a transaction to
 690            the log.  Before we can commit it, wait for the IO so far to
 691            complete.  Control buffers being written are on the
 692            transaction's t_log_list queue, and metadata buffers are on
 693            the t_iobuf_list queue.
 694
 695            Wait for the buffers in reverse order.  That way we are
 696            less likely to be woken up until all IOs have completed, and
 697            so we incur less scheduling load.
 698         */
 699
 700         jbd_debug(3, "JBD: commit phase 3\n");
 701
 702         /*
 703          * akpm: these are BJ_IO, and j_list_lock is not needed.
 704          * See __journal_try_to_free_buffer.
 705          */
 706 wait_for_iobuf:
 707         while (commit_transaction->t_iobuf_list != NULL) {
 708                 struct buffer_head *bh;
 709
 710                 jh = commit_transaction->t_iobuf_list->b_tprev;
 711                 bh = jh2bh(jh);
 712                 if (buffer_locked(bh)) {
 713                         wait_on_buffer(bh);
 714                         goto wait_for_iobuf;
 715                 }
 716                 if (cond_resched())
 717                         goto wait_for_iobuf;
 718
 719                 if (unlikely(!buffer_uptodate(bh)))
 720                         err = -EIO;
 721
 722                 clear_buffer_jwrite(bh);
 723
 724                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 725                 jbd2_journal_unfile_buffer(journal, jh);
 726
 727                 /*
 728                  * ->t_iobuf_list should contain only dummy buffer_heads
 729                  * which were created by jbd2_journal_write_metadata_buffer().
 730                  */
 731                 BUFFER_TRACE(bh, "dumping temporary bh");
 732                 jbd2_journal_put_journal_head(jh);
 733                 __brelse(bh);
 734                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 735                 free_buffer_head(bh);
 736
 737                 /* We also have to unlock and free the corresponding
 738                    shadowed buffer */
 739                 jh = commit_transaction->t_shadow_list->b_tprev;
 740                 bh = jh2bh(jh);
 741                 clear_bit(BH_JWrite, &bh->b_state);
 742                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 743
 744                 /* The metadata is now released for reuse, but we need
 745                    to remember it against this transaction so that when
 746                    we finally commit, we can do any checkpointing
 747                    required. */
 748                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 749                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 750                 /* Wake up any transactions which were waiting for this
 751                    IO to complete */
 752                 wake_up_bit(&bh->b_state, BH_Unshadow);
 753                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 754                 __brelse(bh);
 755         }
 756
 757         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 758
 759         jbd_debug(3, "JBD: commit phase 4\n");
 760
 761         /* Here we wait for the revoke record and descriptor record buffers */
 762  wait_for_ctlbuf:
 763         while (commit_transaction->t_log_list != NULL) {
 764                 struct buffer_head *bh;
 765
 766                 jh = commit_transaction->t_log_list->b_tprev;
 767                 bh = jh2bh(jh);
 768                 if (buffer_locked(bh)) {
 769                         wait_on_buffer(bh);
 770                         goto wait_for_ctlbuf;
 771                 }
 772                 if (cond_resched())
 773                         goto wait_for_ctlbuf;
 774
 775                 if (unlikely(!buffer_uptodate(bh)))
 776                         err = -EIO;
 777
 778                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 779                 clear_buffer_jwrite(bh);
 780                 jbd2_journal_unfile_buffer(journal, jh);
 781                 jbd2_journal_put_journal_head(jh);
 782                 __brelse(bh);           /* One for getblk */
 783                 /* AKPM: bforget here */
 784         }
 785
 786         if (err)
 787                 jbd2_journal_abort(journal, err);
 788
 789         jbd_debug(3, "JBD: commit phase 5\n");
 790
 791         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 792                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 793                 err = journal_submit_commit_record(journal, commit_transaction,
 794                                                 &cbh, crc32_sum);
 795                 if (err)
 796                         __jbd2_journal_abort_hard(journal);
 797         }
 798         if (!err && !is_journal_aborted(journal))
 799                 err = journal_wait_on_commit_record(cbh);
 800
 801         if (err)
 802                 jbd2_journal_abort(journal, err);
 803
 804         /* End of a transaction!  Finally, we can do checkpoint
 805            processing: any buffers committed as a result of this
 806            transaction can be removed from any checkpoint list it was on
 807            before. */
 808
 809         jbd_debug(3, "JBD: commit phase 6\n");
 810
 811         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 812         J_ASSERT(commit_transaction->t_buffers == NULL);
 813         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 814         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 815         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 816         J_ASSERT(commit_transaction->t_log_list == NULL);
 817
 818 restart_loop:
 819         /*
 820          * As there are other places (journal_unmap_buffer()) adding buffers
 821          * to this list we have to be careful and hold the j_list_lock.
 822          */
 823         spin_lock(&journal->j_list_lock);
 824         while (commit_transaction->t_forget) {
 825                 transaction_t *cp_transaction;
 826                 struct buffer_head *bh;
 827
 828                 jh = commit_transaction->t_forget;
 829                 spin_unlock(&journal->j_list_lock);
 830                 bh = jh2bh(jh);
 831                 jbd_lock_bh_state(bh);
 832                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 833                         jh->b_transaction == journal->j_running_transaction);
 834
 835                 /*
 836                  * If there is undo-protected committed data against
 837                  * this buffer, then we can remove it now.  If it is a
 838                  * buffer needing such protection, the old frozen_data
 839                  * field now points to a committed version of the
 840                  * buffer, so rotate that field to the new committed
 841                  * data.
 842                  *
 843                  * Otherwise, we can just throw away the frozen data now.
 844                  */
 845                 if (jh->b_committed_data) {
 846                         jbd2_free(jh->b_committed_data, bh->b_size);
 847                         jh->b_committed_data = NULL;
 848                         if (jh->b_frozen_data) {
 849                                 jh->b_committed_data = jh->b_frozen_data;
 850                                 jh->b_frozen_data = NULL;
 851                         }
 852                 } else if (jh->b_frozen_data) {
 853                         jbd2_free(jh->b_frozen_data, bh->b_size);
 854                         jh->b_frozen_data = NULL;
 855                 }
 856
 857                 spin_lock(&journal->j_list_lock);
 858                 cp_transaction = jh->b_cp_transaction;
 859                 if (cp_transaction) {
 860                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 861                         cp_transaction->t_chp_stats.cs_dropped++;
 862                         __jbd2_journal_remove_checkpoint(jh);
 863                 }
 864
 865                 /* Only re-checkpoint the buffer_head if it is marked
 866                  * dirty.  If the buffer was added to the BJ_Forget list
 867                  * by jbd2_journal_forget, it may no longer be dirty and
 868                  * there's no point in keeping a checkpoint record for
 869                  * it. */
 870
 871                 /* A buffer which has been freed while still being
 872                  * journaled by a previous transaction may end up still
 873                  * being dirty here, but we want to avoid writing back
 874                  * that buffer in the future now that the last use has
 875                  * been committed.  That's not only a performance gain,
 876                  * it also stops aliasing problems if the buffer is left
 877                  * behind for writeback and gets reallocated for another
 878                  * use in a different page. */
 879                 if (buffer_freed(bh)) {
 880                         clear_buffer_freed(bh);
 881                         clear_buffer_jbddirty(bh);
 882                 }
 883
 884                 if (buffer_jbddirty(bh)) {
 885                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 886                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 887                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 888                         __jbd2_journal_refile_buffer(jh);
 889                         jbd_unlock_bh_state(bh);
 890                 } else {
 891                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 892                         /* The buffer on BJ_Forget list and not jbddirty means
 893                          * it has been freed by this transaction and hence it
 894                          * could not have been reallocated until this
 895                          * transaction has committed. *BUT* it could be
 896                          * reallocated once we have written all the data to
 897                          * disk and before we process the buffer on BJ_Forget
 898                          * list. */
 899                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 900                         __jbd2_journal_refile_buffer(jh);
 901                         if (!jh->b_transaction) {
 902                                 jbd_unlock_bh_state(bh);
 903                                  /* needs a brelse */
 904                                 jbd2_journal_remove_journal_head(bh);
 905                                 release_buffer_page(bh);
 906                         } else
 907                                 jbd_unlock_bh_state(bh);
 908                 }
 909                 cond_resched_lock(&journal->j_list_lock);
 910         }
 911         spin_unlock(&journal->j_list_lock);
 912         /*
 913          * This is a bit sleazy.  We use j_list_lock to protect transition
 914          * of a transaction into T_FINISHED state and calling
 915          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 916          * other checkpointing code processing the transaction...
 917          */
 918         spin_lock(&journal->j_state_lock);
 919         spin_lock(&journal->j_list_lock);
 920         /*
 921          * Now recheck if some buffers did not get attached to the transaction
 922          * while the lock was dropped...
 923          */
 924         if (commit_transaction->t_forget) {
 925                 spin_unlock(&journal->j_list_lock);
 926                 spin_unlock(&journal->j_state_lock);
 927                 goto restart_loop;
 928         }
 929
 930         /* Done with this transaction! */
 931
 932         jbd_debug(3, "JBD: commit phase 7\n");
 933
 934         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 935
 936         commit_transaction->t_start = jiffies;
 937         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
 938                                                 commit_transaction->t_start);
 939
 940         /*
 941          * File the transaction for history
 942          */
 943         stats.ts_type = JBD2_STATS_RUN;
 944         stats.ts_tid = commit_transaction->t_tid;
 945         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
 946         spin_lock(&journal->j_history_lock);
 947         memcpy(journal->j_history + journal->j_history_cur, &stats,
 948                         sizeof(stats));
 949         if (++journal->j_history_cur == journal->j_history_max)
 950                 journal->j_history_cur = 0;
 951
 952         /*
 953          * Calculate overall stats
 954          */
 955         journal->j_stats.ts_tid++;
 956         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
 957         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
 958         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
 959         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
 960         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
 961         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
 962         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
 963         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
 964         spin_unlock(&journal->j_history_lock);
 965
 966         commit_transaction->t_state = T_FINISHED;
 967         J_ASSERT(commit_transaction == journal->j_committing_transaction);
 968         journal->j_commit_sequence = commit_transaction->t_tid;
 969         journal->j_committing_transaction = NULL;
 970         spin_unlock(&journal->j_state_lock);
 971
 972         if (commit_transaction->t_checkpoint_list == NULL &&
 973             commit_transaction->t_checkpoint_io_list == NULL) {
 974                 __jbd2_journal_drop_transaction(journal, commit_transaction);
 975         } else {
 976                 if (journal->j_checkpoint_transactions == NULL) {
 977                         journal->j_checkpoint_transactions = commit_transaction;
 978                         commit_transaction->t_cpnext = commit_transaction;
 979                         commit_transaction->t_cpprev = commit_transaction;
 980                 } else {
 981                         commit_transaction->t_cpnext =
 982                                 journal->j_checkpoint_transactions;
 983                         commit_transaction->t_cpprev =
 984                                 commit_transaction->t_cpnext->t_cpprev;
 985                         commit_transaction->t_cpnext->t_cpprev =
 986                                 commit_transaction;
 987                         commit_transaction->t_cpprev->t_cpnext =
 988                                 commit_transaction;
 989                 }
 990         }
 991         spin_unlock(&journal->j_list_lock);
 992
 993         trace_mark(jbd2_end_commit, "dev %s transaction %d head %d",
 994                    journal->j_devname, commit_transaction->t_tid,
 995                    journal->j_tail_sequence);
 996         jbd_debug(1, "JBD: commit %d complete, head %d\n",
 997                   journal->j_commit_sequence, journal->j_tail_sequence);
 998
 999         wake_up(&journal->j_wait_done_commit);
1000 }