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