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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 #include <linux/bio.h>
  29
  30 /*
  31  * Default IO end handler for temporary BJ_IO buffer_heads.
  32  */
  33 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
  34 {
  35         BUFFER_TRACE(bh, "");
  36         if (uptodate)
  37                 set_buffer_uptodate(bh);
  38         else
  39                 clear_buffer_uptodate(bh);
  40         unlock_buffer(bh);
  41 }
  42
  43 /*
  44  * When an ext4 file is truncated, it is possible that some pages are not
  45  * successfully freed, because they are attached to a committing transaction.
  46  * After the transaction commits, these pages are left on the LRU, with no
  47  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
  48  * by the VM, but their apparent absence upsets the VM accounting, and it makes
  49  * the numbers in /proc/meminfo look odd.
  50  *
  51  * So here, we have a buffer which has just come off the forget list.  Look to
  52  * see if we can strip all buffers from the backing page.
  53  *
  54  * Called under lock_journal(), and possibly under journal_datalist_lock.  The
  55  * caller provided us with a ref against the buffer, and we drop that here.
  56  */
  57 static void release_buffer_page(struct buffer_head *bh)
  58 {
  59         struct page *page;
  60
  61         if (buffer_dirty(bh))
  62                 goto nope;
  63         if (atomic_read(&bh->b_count) != 1)
  64                 goto nope;
  65         page = bh->b_page;
  66         if (!page)
  67                 goto nope;
  68         if (page->mapping)
  69                 goto nope;
  70
  71         /* OK, it's a truncated page */
  72         if (!trylock_page(page))
  73                 goto nope;
  74
  75         page_cache_get(page);
  76         __brelse(bh);
  77         try_to_free_buffers(page);
  78         unlock_page(page);
  79         page_cache_release(page);
  80         return;
  81
  82 nope:
  83         __brelse(bh);
  84 }
  85
  86 /*
  87  * Done it all: now submit the commit record.  We should have
  88  * cleaned up our previous buffers by now, so if we are in abort
  89  * mode we can now just skip the rest of the journal write
  90  * entirely.
  91  *
  92  * Returns 1 if the journal needs to be aborted or 0 on success
  93  */
  94 static int journal_submit_commit_record(journal_t *journal,
  95                                         transaction_t *commit_transaction,
  96                                         struct buffer_head **cbh,
  97                                         __u32 crc32_sum)
  98 {
  99         struct journal_head *descriptor;
 100         struct commit_header *tmp;
 101         struct buffer_head *bh;
 102         int ret;
 103         int barrier_done = 0;
 104         struct timespec now = current_kernel_time();
 105
 106         if (is_journal_aborted(journal))
 107                 return 0;
 108
 109         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 110         if (!descriptor)
 111                 return 1;
 112
 113         bh = jh2bh(descriptor);
 114
 115         tmp = (struct commit_header *)bh->b_data;
 116         tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
 117         tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
 118         tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 119         tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
 120         tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);
 121
 122         if (JBD2_HAS_COMPAT_FEATURE(journal,
 123                                     JBD2_FEATURE_COMPAT_CHECKSUM)) {
 124                 tmp->h_chksum_type      = JBD2_CRC32_CHKSUM;
 125                 tmp->h_chksum_size      = JBD2_CRC32_CHKSUM_SIZE;
 126                 tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
 127         }
 128
 129         JBUFFER_TRACE(descriptor, "submit commit block");
 130         lock_buffer(bh);
 131         clear_buffer_dirty(bh);
 132         set_buffer_uptodate(bh);
 133         bh->b_end_io = journal_end_buffer_io_sync;
 134
 135         if (journal->j_flags & JBD2_BARRIER &&
 136                 !JBD2_HAS_INCOMPAT_FEATURE(journal,
 137                                          JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 138                 set_buffer_ordered(bh);
 139                 barrier_done = 1;
 140         }
 141         ret = submit_bh(WRITE_SYNC, bh);
 142         if (barrier_done)
 143                 clear_buffer_ordered(bh);
 144
 145         /* is it possible for another commit to fail at roughly
 146          * the same time as this one?  If so, we don't want to
 147          * trust the barrier flag in the super, but instead want
 148          * to remember if we sent a barrier request
 149          */
 150         if (ret == -EOPNOTSUPP && barrier_done) {
 151                 printk(KERN_WARNING
 152                        "JBD: barrier-based sync failed on %s - "
 153                        "disabling barriers\n", journal->j_devname);
 154                 spin_lock(&journal->j_state_lock);
 155                 journal->j_flags &= ~JBD2_BARRIER;
 156                 spin_unlock(&journal->j_state_lock);
 157
 158                 /* And try again, without the barrier */
 159                 lock_buffer(bh);
 160                 set_buffer_uptodate(bh);
 161                 clear_buffer_dirty(bh);
 162                 ret = submit_bh(WRITE_SYNC, bh);
 163         }
 164         *cbh = bh;
 165         return ret;
 166 }
 167
 168 /*
 169  * This function along with journal_submit_commit_record
 170  * allows to write the commit record asynchronously.
 171  */
 172 static int journal_wait_on_commit_record(journal_t *journal,
 173                                          struct buffer_head *bh)
 174 {
 175         int ret = 0;
 176
 177 retry:
 178         clear_buffer_dirty(bh);
 179         wait_on_buffer(bh);
 180         if (buffer_eopnotsupp(bh) && (journal->j_flags & JBD2_BARRIER)) {
 181                 printk(KERN_WARNING
 182                        "JBD2: wait_on_commit_record: sync failed on %s - "
 183                        "disabling barriers\n", journal->j_devname);
 184                 spin_lock(&journal->j_state_lock);
 185                 journal->j_flags &= ~JBD2_BARRIER;
 186                 spin_unlock(&journal->j_state_lock);
 187
 188                 lock_buffer(bh);
 189                 clear_buffer_dirty(bh);
 190                 set_buffer_uptodate(bh);
 191                 bh->b_end_io = journal_end_buffer_io_sync;
 192
 193                 ret = submit_bh(WRITE_SYNC, bh);
 194                 if (ret) {
 195                         unlock_buffer(bh);
 196                         return ret;
 197                 }
 198                 goto retry;
 199         }
 200
 201         if (unlikely(!buffer_uptodate(bh)))
 202                 ret = -EIO;
 203         put_bh(bh);            /* One for getblk() */
 204         jbd2_journal_put_journal_head(bh2jh(bh));
 205
 206         return ret;
 207 }
 208
 209 /*
 210  * write the filemap data using writepage() address_space_operations.
 211  * We don't do block allocation here even for delalloc. We don't
 212  * use writepages() because with dealyed allocation we may be doing
 213  * block allocation in writepages().
 214  */
 215 static int journal_submit_inode_data_buffers(struct address_space *mapping)
 216 {
 217         int ret;
 218         struct writeback_control wbc = {
 219                 .sync_mode =  WB_SYNC_ALL,
 220                 .nr_to_write = mapping->nrpages * 2,
 221                 .range_start = 0,
 222                 .range_end = i_size_read(mapping->host),
 223                 .for_writepages = 1,
 224         };
 225
 226         ret = generic_writepages(mapping, &wbc);
 227         return ret;
 228 }
 229
 230 /*
 231  * Submit all the data buffers of inode associated with the transaction to
 232  * disk.
 233  *
 234  * We are in a committing transaction. Therefore no new inode can be added to
 235  * our inode list. We use JI_COMMIT_RUNNING flag to protect inode we currently
 236  * operate on from being released while we write out pages.
 237  */
 238 static int journal_submit_data_buffers(journal_t *journal,
 239                 transaction_t *commit_transaction)
 240 {
 241         struct jbd2_inode *jinode;
 242         int err, ret = 0;
 243         struct address_space *mapping;
 244
 245         spin_lock(&journal->j_list_lock);
 246         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 247                 mapping = jinode->i_vfs_inode->i_mapping;
 248                 jinode->i_flags |= JI_COMMIT_RUNNING;
 249                 spin_unlock(&journal->j_list_lock);
 250                 /*
 251                  * submit the inode data buffers. We use writepage
 252                  * instead of writepages. Because writepages can do
 253                  * block allocation  with delalloc. We need to write
 254                  * only allocated blocks here.
 255                  */
 256                 err = journal_submit_inode_data_buffers(mapping);
 257                 if (!ret)
 258                         ret = err;
 259                 spin_lock(&journal->j_list_lock);
 260                 J_ASSERT(jinode->i_transaction == commit_transaction);
 261                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 262                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 263         }
 264         spin_unlock(&journal->j_list_lock);
 265         return ret;
 266 }
 267
 268 /*
 269  * Wait for data submitted for writeout, refile inodes to proper
 270  * transaction if needed.
 271  *
 272  */
 273 static int journal_finish_inode_data_buffers(journal_t *journal,
 274                 transaction_t *commit_transaction)
 275 {
 276         struct jbd2_inode *jinode, *next_i;
 277         int err, ret = 0;
 278
 279         /* For locking, see the comment in journal_submit_data_buffers() */
 280         spin_lock(&journal->j_list_lock);
 281         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 282                 jinode->i_flags |= JI_COMMIT_RUNNING;
 283                 spin_unlock(&journal->j_list_lock);
 284                 err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
 285                 if (err) {
 286                         /*
 287                          * Because AS_EIO is cleared by
 288                          * wait_on_page_writeback_range(), set it again so
 289                          * that user process can get -EIO from fsync().
 290                          */
 291                         set_bit(AS_EIO,
 292                                 &jinode->i_vfs_inode->i_mapping->flags);
 293
 294                         if (!ret)
 295                                 ret = err;
 296                 }
 297                 spin_lock(&journal->j_list_lock);
 298                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 299                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 300         }
 301
 302         /* Now refile inode to proper lists */
 303         list_for_each_entry_safe(jinode, next_i,
 304                                  &commit_transaction->t_inode_list, i_list) {
 305                 list_del(&jinode->i_list);
 306                 if (jinode->i_next_transaction) {
 307                         jinode->i_transaction = jinode->i_next_transaction;
 308                         jinode->i_next_transaction = NULL;
 309                         list_add(&jinode->i_list,
 310                                 &jinode->i_transaction->t_inode_list);
 311                 } else {
 312                         jinode->i_transaction = NULL;
 313                 }
 314         }
 315         spin_unlock(&journal->j_list_lock);
 316
 317         return ret;
 318 }
 319
 320 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 321 {
 322         struct page *page = bh->b_page;
 323         char *addr;
 324         __u32 checksum;
 325
 326         addr = kmap_atomic(page, KM_USER0);
 327         checksum = crc32_be(crc32_sum,
 328                 (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
 329         kunmap_atomic(addr, KM_USER0);
 330
 331         return checksum;
 332 }
 333
 334 static void write_tag_block(int tag_bytes, journal_block_tag_t *tag,
 335                                    unsigned long long block)
 336 {
 337         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
 338         if (tag_bytes > JBD2_TAG_SIZE32)
 339                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
 340 }
 341
 342 /*
 343  * jbd2_journal_commit_transaction
 344  *
 345  * The primary function for committing a transaction to the log.  This
 346  * function is called by the journal thread to begin a complete commit.
 347  */
 348 void jbd2_journal_commit_transaction(journal_t *journal)
 349 {
 350         struct transaction_stats_s stats;
 351         transaction_t *commit_transaction;
 352         struct journal_head *jh, *new_jh, *descriptor;
 353         struct buffer_head **wbuf = journal->j_wbuf;
 354         int bufs;
 355         int flags;
 356         int err;
 357         unsigned long long blocknr;
 358         ktime_t start_time;
 359         u64 commit_time;
 360         char *tagp = NULL;
 361         journal_header_t *header;
 362         journal_block_tag_t *tag = NULL;
 363         int space_left = 0;
 364         int first_tag = 0;
 365         int tag_flag;
 366         int i, to_free = 0;
 367         int tag_bytes = journal_tag_bytes(journal);
 368         struct buffer_head *cbh = NULL; /* For transactional checksums */
 369         __u32 crc32_sum = ~0;
 370
 371         /*
 372          * First job: lock down the current transaction and wait for
 373          * all outstanding updates to complete.
 374          */
 375
 376 #ifdef COMMIT_STATS
 377         spin_lock(&journal->j_list_lock);
 378         summarise_journal_usage(journal);
 379         spin_unlock(&journal->j_list_lock);
 380 #endif
 381
 382         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 383         if (journal->j_flags & JBD2_FLUSHED) {
 384                 jbd_debug(3, "super block updated\n");
 385                 jbd2_journal_update_superblock(journal, 1);
 386         } else {
 387                 jbd_debug(3, "superblock not updated\n");
 388         }
 389
 390         J_ASSERT(journal->j_running_transaction != NULL);
 391         J_ASSERT(journal->j_committing_transaction == NULL);
 392
 393         commit_transaction = journal->j_running_transaction;
 394         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 395
 396         trace_mark(jbd2_start_commit, "dev %s transaction %d",
 397                    journal->j_devname, commit_transaction->t_tid);
 398         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 399                         commit_transaction->t_tid);
 400
 401         spin_lock(&journal->j_state_lock);
 402         commit_transaction->t_state = T_LOCKED;
 403
 404         stats.u.run.rs_wait = commit_transaction->t_max_wait;
 405         stats.u.run.rs_locked = jiffies;
 406         stats.u.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 407                                                 stats.u.run.rs_locked);
 408
 409         spin_lock(&commit_transaction->t_handle_lock);
 410         while (commit_transaction->t_updates) {
 411                 DEFINE_WAIT(wait);
 412
 413                 prepare_to_wait(&journal->j_wait_updates, &wait,
 414                                         TASK_UNINTERRUPTIBLE);
 415                 if (commit_transaction->t_updates) {
 416                         spin_unlock(&commit_transaction->t_handle_lock);
 417                         spin_unlock(&journal->j_state_lock);
 418                         schedule();
 419                         spin_lock(&journal->j_state_lock);
 420                         spin_lock(&commit_transaction->t_handle_lock);
 421                 }
 422                 finish_wait(&journal->j_wait_updates, &wait);
 423         }
 424         spin_unlock(&commit_transaction->t_handle_lock);
 425
 426         J_ASSERT (commit_transaction->t_outstanding_credits <=
 427                         journal->j_max_transaction_buffers);
 428
 429         /*
 430          * First thing we are allowed to do is to discard any remaining
 431          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 432          * that there are no such buffers: if a large filesystem
 433          * operation like a truncate needs to split itself over multiple
 434          * transactions, then it may try to do a jbd2_journal_restart() while
 435          * there are still BJ_Reserved buffers outstanding.  These must
 436          * be released cleanly from the current transaction.
 437          *
 438          * In this case, the filesystem must still reserve write access
 439          * again before modifying the buffer in the new transaction, but
 440          * we do not require it to remember exactly which old buffers it
 441          * has reserved.  This is consistent with the existing behaviour
 442          * that multiple jbd2_journal_get_write_access() calls to the same
 443          * buffer are perfectly permissable.
 444          */
 445         while (commit_transaction->t_reserved_list) {
 446                 jh = commit_transaction->t_reserved_list;
 447                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 448                 /*
 449                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 450                  * leave undo-committed data.
 451                  */
 452                 if (jh->b_committed_data) {
 453                         struct buffer_head *bh = jh2bh(jh);
 454
 455                         jbd_lock_bh_state(bh);
 456                         jbd2_free(jh->b_committed_data, bh->b_size);
 457                         jh->b_committed_data = NULL;
 458                         jbd_unlock_bh_state(bh);
 459                 }
 460                 jbd2_journal_refile_buffer(journal, jh);
 461         }
 462
 463         /*
 464          * Now try to drop any written-back buffers from the journal's
 465          * checkpoint lists.  We do this *before* commit because it potentially
 466          * frees some memory
 467          */
 468         spin_lock(&journal->j_list_lock);
 469         __jbd2_journal_clean_checkpoint_list(journal);
 470         spin_unlock(&journal->j_list_lock);
 471
 472         jbd_debug (3, "JBD: commit phase 1\n");
 473
 474         /*
 475          * Switch to a new revoke table.
 476          */
 477         jbd2_journal_switch_revoke_table(journal);
 478
 479         stats.u.run.rs_flushing = jiffies;
 480         stats.u.run.rs_locked = jbd2_time_diff(stats.u.run.rs_locked,
 481                                                stats.u.run.rs_flushing);
 482
 483         commit_transaction->t_state = T_FLUSH;
 484         journal->j_committing_transaction = commit_transaction;
 485         journal->j_running_transaction = NULL;
 486         start_time = ktime_get();
 487         commit_transaction->t_log_start = journal->j_head;
 488         wake_up(&journal->j_wait_transaction_locked);
 489         spin_unlock(&journal->j_state_lock);
 490
 491         jbd_debug (3, "JBD: commit phase 2\n");
 492
 493         /*
 494          * Now start flushing things to disk, in the order they appear
 495          * on the transaction lists.  Data blocks go first.
 496          */
 497         err = journal_submit_data_buffers(journal, commit_transaction);
 498         if (err)
 499                 jbd2_journal_abort(journal, err);
 500
 501         jbd2_journal_write_revoke_records(journal, commit_transaction);
 502
 503         jbd_debug(3, "JBD: commit phase 2\n");
 504
 505         /*
 506          * Way to go: we have now written out all of the data for a
 507          * transaction!  Now comes the tricky part: we need to write out
 508          * metadata.  Loop over the transaction's entire buffer list:
 509          */
 510         spin_lock(&journal->j_state_lock);
 511         commit_transaction->t_state = T_COMMIT;
 512         spin_unlock(&journal->j_state_lock);
 513
 514         stats.u.run.rs_logging = jiffies;
 515         stats.u.run.rs_flushing = jbd2_time_diff(stats.u.run.rs_flushing,
 516                                                  stats.u.run.rs_logging);
 517         stats.u.run.rs_blocks = commit_transaction->t_outstanding_credits;
 518         stats.u.run.rs_blocks_logged = 0;
 519
 520         J_ASSERT(commit_transaction->t_nr_buffers <=
 521                  commit_transaction->t_outstanding_credits);
 522
 523         err = 0;
 524         descriptor = NULL;
 525         bufs = 0;
 526         while (commit_transaction->t_buffers) {
 527
 528                 /* Find the next buffer to be journaled... */
 529
 530                 jh = commit_transaction->t_buffers;
 531
 532                 /* If we're in abort mode, we just un-journal the buffer and
 533                    release it. */
 534
 535                 if (is_journal_aborted(journal)) {
 536                         clear_buffer_jbddirty(jh2bh(jh));
 537                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 538                         jbd2_buffer_abort_trigger(jh,
 539                                                   jh->b_frozen_data ?
 540                                                   jh->b_frozen_triggers :
 541                                                   jh->b_triggers);
 542                         jbd2_journal_refile_buffer(journal, jh);
 543                         /* If that was the last one, we need to clean up
 544                          * any descriptor buffers which may have been
 545                          * already allocated, even if we are now
 546                          * aborting. */
 547                         if (!commit_transaction->t_buffers)
 548                                 goto start_journal_io;
 549                         continue;
 550                 }
 551
 552                 /* Make sure we have a descriptor block in which to
 553                    record the metadata buffer. */
 554
 555                 if (!descriptor) {
 556                         struct buffer_head *bh;
 557
 558                         J_ASSERT (bufs == 0);
 559
 560                         jbd_debug(4, "JBD: get descriptor\n");
 561
 562                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 563                         if (!descriptor) {
 564                                 jbd2_journal_abort(journal, -EIO);
 565                                 continue;
 566                         }
 567
 568                         bh = jh2bh(descriptor);
 569                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 570                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 571                         header = (journal_header_t *)&bh->b_data[0];
 572                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 573                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 574                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 575
 576                         tagp = &bh->b_data[sizeof(journal_header_t)];
 577                         space_left = bh->b_size - sizeof(journal_header_t);
 578                         first_tag = 1;
 579                         set_buffer_jwrite(bh);
 580                         set_buffer_dirty(bh);
 581                         wbuf[bufs++] = bh;
 582
 583                         /* Record it so that we can wait for IO
 584                            completion later */
 585                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 586                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 587                                         BJ_LogCtl);
 588                 }
 589
 590                 /* Where is the buffer to be written? */
 591
 592                 err = jbd2_journal_next_log_block(journal, &blocknr);
 593                 /* If the block mapping failed, just abandon the buffer
 594                    and repeat this loop: we'll fall into the
 595                    refile-on-abort condition above. */
 596                 if (err) {
 597                         jbd2_journal_abort(journal, err);
 598                         continue;
 599                 }
 600
 601                 /*
 602                  * start_this_handle() uses t_outstanding_credits to determine
 603                  * the free space in the log, but this counter is changed
 604                  * by jbd2_journal_next_log_block() also.
 605                  */
 606                 commit_transaction->t_outstanding_credits--;
 607
 608                 /* Bump b_count to prevent truncate from stumbling over
 609                    the shadowed buffer!  @@@ This can go if we ever get
 610                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 611                 atomic_inc(&jh2bh(jh)->b_count);
 612
 613                 /* Make a temporary IO buffer with which to write it out
 614                    (this will requeue both the metadata buffer and the
 615                    temporary IO buffer). new_bh goes on BJ_IO*/
 616
 617                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 618                 /*
 619                  * akpm: jbd2_journal_write_metadata_buffer() sets
 620                  * new_bh->b_transaction to commit_transaction.
 621                  * We need to clean this up before we release new_bh
 622                  * (which is of type BJ_IO)
 623                  */
 624                 JBUFFER_TRACE(jh, "ph3: write metadata");
 625                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 626                                                       jh, &new_jh, blocknr);
 627                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 628                 wbuf[bufs++] = jh2bh(new_jh);
 629
 630                 /* Record the new block's tag in the current descriptor
 631                    buffer */
 632
 633                 tag_flag = 0;
 634                 if (flags & 1)
 635                         tag_flag |= JBD2_FLAG_ESCAPE;
 636                 if (!first_tag)
 637                         tag_flag |= JBD2_FLAG_SAME_UUID;
 638
 639                 tag = (journal_block_tag_t *) tagp;
 640                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 641                 tag->t_flags = cpu_to_be32(tag_flag);
 642                 tagp += tag_bytes;
 643                 space_left -= tag_bytes;
 644
 645                 if (first_tag) {
 646                         memcpy (tagp, journal->j_uuid, 16);
 647                         tagp += 16;
 648                         space_left -= 16;
 649                         first_tag = 0;
 650                 }
 651
 652                 /* If there's no more to do, or if the descriptor is full,
 653                    let the IO rip! */
 654
 655                 if (bufs == journal->j_wbufsize ||
 656                     commit_transaction->t_buffers == NULL ||
 657                     space_left < tag_bytes + 16) {
 658
 659                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 660
 661                         /* Write an end-of-descriptor marker before
 662                            submitting the IOs.  "tag" still points to
 663                            the last tag we set up. */
 664
 665                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 666
 667 start_journal_io:
 668                         for (i = 0; i < bufs; i++) {
 669                                 struct buffer_head *bh = wbuf[i];
 670                                 /*
 671                                  * Compute checksum.
 672                                  */
 673                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 674                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 675                                         crc32_sum =
 676                                             jbd2_checksum_data(crc32_sum, bh);
 677                                 }
 678
 679                                 lock_buffer(bh);
 680                                 clear_buffer_dirty(bh);
 681                                 set_buffer_uptodate(bh);
 682                                 bh->b_end_io = journal_end_buffer_io_sync;
 683                                 submit_bh(WRITE, bh);
 684                         }
 685                         cond_resched();
 686                         stats.u.run.rs_blocks_logged += bufs;
 687
 688                         /* Force a new descriptor to be generated next
 689                            time round the loop. */
 690                         descriptor = NULL;
 691                         bufs = 0;
 692                 }
 693         }
 694
 695         /* Done it all: now write the commit record asynchronously. */
 696
 697         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 698                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 699                 err = journal_submit_commit_record(journal, commit_transaction,
 700                                                  &cbh, crc32_sum);
 701                 if (err)
 702                         __jbd2_journal_abort_hard(journal);
 703         }
 704
 705         /*
 706          * This is the right place to wait for data buffers both for ASYNC
 707          * and !ASYNC commit. If commit is ASYNC, we need to wait only after
 708          * the commit block went to disk (which happens above). If commit is
 709          * SYNC, we need to wait for data buffers before we start writing
 710          * commit block, which happens below in such setting.
 711          */
 712         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 713         if (err) {
 714                 printk(KERN_WARNING
 715                         "JBD2: Detected IO errors while flushing file data "
 716                        "on %s\n", journal->j_devname);
 717                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 718                         jbd2_journal_abort(journal, err);
 719                 err = 0;
 720         }
 721
 722         /* Lo and behold: we have just managed to send a transaction to
 723            the log.  Before we can commit it, wait for the IO so far to
 724            complete.  Control buffers being written are on the
 725            transaction's t_log_list queue, and metadata buffers are on
 726            the t_iobuf_list queue.
 727
 728            Wait for the buffers in reverse order.  That way we are
 729            less likely to be woken up until all IOs have completed, and
 730            so we incur less scheduling load.
 731         */
 732
 733         jbd_debug(3, "JBD: commit phase 3\n");
 734
 735         /*
 736          * akpm: these are BJ_IO, and j_list_lock is not needed.
 737          * See __journal_try_to_free_buffer.
 738          */
 739 wait_for_iobuf:
 740         while (commit_transaction->t_iobuf_list != NULL) {
 741                 struct buffer_head *bh;
 742
 743                 jh = commit_transaction->t_iobuf_list->b_tprev;
 744                 bh = jh2bh(jh);
 745                 if (buffer_locked(bh)) {
 746                         wait_on_buffer(bh);
 747                         goto wait_for_iobuf;
 748                 }
 749                 if (cond_resched())
 750                         goto wait_for_iobuf;
 751
 752                 if (unlikely(!buffer_uptodate(bh)))
 753                         err = -EIO;
 754
 755                 clear_buffer_jwrite(bh);
 756
 757                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 758                 jbd2_journal_unfile_buffer(journal, jh);
 759
 760                 /*
 761                  * ->t_iobuf_list should contain only dummy buffer_heads
 762                  * which were created by jbd2_journal_write_metadata_buffer().
 763                  */
 764                 BUFFER_TRACE(bh, "dumping temporary bh");
 765                 jbd2_journal_put_journal_head(jh);
 766                 __brelse(bh);
 767                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 768                 free_buffer_head(bh);
 769
 770                 /* We also have to unlock and free the corresponding
 771                    shadowed buffer */
 772                 jh = commit_transaction->t_shadow_list->b_tprev;
 773                 bh = jh2bh(jh);
 774                 clear_bit(BH_JWrite, &bh->b_state);
 775                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 776
 777                 /* The metadata is now released for reuse, but we need
 778                    to remember it against this transaction so that when
 779                    we finally commit, we can do any checkpointing
 780                    required. */
 781                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 782                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 783                 /* Wake up any transactions which were waiting for this
 784                    IO to complete */
 785                 wake_up_bit(&bh->b_state, BH_Unshadow);
 786                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 787                 __brelse(bh);
 788         }
 789
 790         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 791
 792         jbd_debug(3, "JBD: commit phase 4\n");
 793
 794         /* Here we wait for the revoke record and descriptor record buffers */
 795  wait_for_ctlbuf:
 796         while (commit_transaction->t_log_list != NULL) {
 797                 struct buffer_head *bh;
 798
 799                 jh = commit_transaction->t_log_list->b_tprev;
 800                 bh = jh2bh(jh);
 801                 if (buffer_locked(bh)) {
 802                         wait_on_buffer(bh);
 803                         goto wait_for_ctlbuf;
 804                 }
 805                 if (cond_resched())
 806                         goto wait_for_ctlbuf;
 807
 808                 if (unlikely(!buffer_uptodate(bh)))
 809                         err = -EIO;
 810
 811                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 812                 clear_buffer_jwrite(bh);
 813                 jbd2_journal_unfile_buffer(journal, jh);
 814                 jbd2_journal_put_journal_head(jh);
 815                 __brelse(bh);           /* One for getblk */
 816                 /* AKPM: bforget here */
 817         }
 818
 819         if (err)
 820                 jbd2_journal_abort(journal, err);
 821
 822         jbd_debug(3, "JBD: commit phase 5\n");
 823
 824         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 825                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 826                 err = journal_submit_commit_record(journal, commit_transaction,
 827                                                 &cbh, crc32_sum);
 828                 if (err)
 829                         __jbd2_journal_abort_hard(journal);
 830         }
 831         if (!err && !is_journal_aborted(journal))
 832                 err = journal_wait_on_commit_record(journal, cbh);
 833
 834         if (err)
 835                 jbd2_journal_abort(journal, err);
 836
 837         /* End of a transaction!  Finally, we can do checkpoint
 838            processing: any buffers committed as a result of this
 839            transaction can be removed from any checkpoint list it was on
 840            before. */
 841
 842         jbd_debug(3, "JBD: commit phase 6\n");
 843
 844         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 845         J_ASSERT(commit_transaction->t_buffers == NULL);
 846         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 847         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 848         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 849         J_ASSERT(commit_transaction->t_log_list == NULL);
 850
 851 restart_loop:
 852         /*
 853          * As there are other places (journal_unmap_buffer()) adding buffers
 854          * to this list we have to be careful and hold the j_list_lock.
 855          */
 856         spin_lock(&journal->j_list_lock);
 857         while (commit_transaction->t_forget) {
 858                 transaction_t *cp_transaction;
 859                 struct buffer_head *bh;
 860
 861                 jh = commit_transaction->t_forget;
 862                 spin_unlock(&journal->j_list_lock);
 863                 bh = jh2bh(jh);
 864                 jbd_lock_bh_state(bh);
 865                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 866                         jh->b_transaction == journal->j_running_transaction);
 867
 868                 /*
 869                  * If there is undo-protected committed data against
 870                  * this buffer, then we can remove it now.  If it is a
 871                  * buffer needing such protection, the old frozen_data
 872                  * field now points to a committed version of the
 873                  * buffer, so rotate that field to the new committed
 874                  * data.
 875                  *
 876                  * Otherwise, we can just throw away the frozen data now.
 877                  *
 878                  * We also know that the frozen data has already fired
 879                  * its triggers if they exist, so we can clear that too.
 880                  */
 881                 if (jh->b_committed_data) {
 882                         jbd2_free(jh->b_committed_data, bh->b_size);
 883                         jh->b_committed_data = NULL;
 884                         if (jh->b_frozen_data) {
 885                                 jh->b_committed_data = jh->b_frozen_data;
 886                                 jh->b_frozen_data = NULL;
 887                                 jh->b_frozen_triggers = NULL;
 888                         }
 889                 } else if (jh->b_frozen_data) {
 890                         jbd2_free(jh->b_frozen_data, bh->b_size);
 891                         jh->b_frozen_data = NULL;
 892                         jh->b_frozen_triggers = NULL;
 893                 }
 894
 895                 spin_lock(&journal->j_list_lock);
 896                 cp_transaction = jh->b_cp_transaction;
 897                 if (cp_transaction) {
 898                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 899                         cp_transaction->t_chp_stats.cs_dropped++;
 900                         __jbd2_journal_remove_checkpoint(jh);
 901                 }
 902
 903                 /* Only re-checkpoint the buffer_head if it is marked
 904                  * dirty.  If the buffer was added to the BJ_Forget list
 905                  * by jbd2_journal_forget, it may no longer be dirty and
 906                  * there's no point in keeping a checkpoint record for
 907                  * it. */
 908
 909                 /* A buffer which has been freed while still being
 910                  * journaled by a previous transaction may end up still
 911                  * being dirty here, but we want to avoid writing back
 912                  * that buffer in the future now that the last use has
 913                  * been committed.  That's not only a performance gain,
 914                  * it also stops aliasing problems if the buffer is left
 915                  * behind for writeback and gets reallocated for another
 916                  * use in a different page. */
 917                 if (buffer_freed(bh)) {
 918                         clear_buffer_freed(bh);
 919                         clear_buffer_jbddirty(bh);
 920                 }
 921
 922                 if (buffer_jbddirty(bh)) {
 923                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 924                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 925                         if (is_journal_aborted(journal))
 926                                 clear_buffer_jbddirty(bh);
 927                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 928                         __jbd2_journal_refile_buffer(jh);
 929                         jbd_unlock_bh_state(bh);
 930                 } else {
 931                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 932                         /* The buffer on BJ_Forget list and not jbddirty means
 933                          * it has been freed by this transaction and hence it
 934                          * could not have been reallocated until this
 935                          * transaction has committed. *BUT* it could be
 936                          * reallocated once we have written all the data to
 937                          * disk and before we process the buffer on BJ_Forget
 938                          * list. */
 939                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 940                         __jbd2_journal_refile_buffer(jh);
 941                         if (!jh->b_transaction) {
 942                                 jbd_unlock_bh_state(bh);
 943                                  /* needs a brelse */
 944                                 jbd2_journal_remove_journal_head(bh);
 945                                 release_buffer_page(bh);
 946                         } else
 947                                 jbd_unlock_bh_state(bh);
 948                 }
 949                 cond_resched_lock(&journal->j_list_lock);
 950         }
 951         spin_unlock(&journal->j_list_lock);
 952         /*
 953          * This is a bit sleazy.  We use j_list_lock to protect transition
 954          * of a transaction into T_FINISHED state and calling
 955          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 956          * other checkpointing code processing the transaction...
 957          */
 958         spin_lock(&journal->j_state_lock);
 959         spin_lock(&journal->j_list_lock);
 960         /*
 961          * Now recheck if some buffers did not get attached to the transaction
 962          * while the lock was dropped...
 963          */
 964         if (commit_transaction->t_forget) {
 965                 spin_unlock(&journal->j_list_lock);
 966                 spin_unlock(&journal->j_state_lock);
 967                 goto restart_loop;
 968         }
 969
 970         /* Done with this transaction! */
 971
 972         jbd_debug(3, "JBD: commit phase 7\n");
 973
 974         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 975
 976         commit_transaction->t_start = jiffies;
 977         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
 978                                                 commit_transaction->t_start);
 979
 980         /*
 981          * File the transaction for history
 982          */
 983         stats.ts_type = JBD2_STATS_RUN;
 984         stats.ts_tid = commit_transaction->t_tid;
 985         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
 986         spin_lock(&journal->j_history_lock);
 987         memcpy(journal->j_history + journal->j_history_cur, &stats,
 988                         sizeof(stats));
 989         if (++journal->j_history_cur == journal->j_history_max)
 990                 journal->j_history_cur = 0;
 991
 992         /*
 993          * Calculate overall stats
 994          */
 995         journal->j_stats.ts_tid++;
 996         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
 997         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
 998         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
 999         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
1000         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
1001         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
1002         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
1003         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
1004         spin_unlock(&journal->j_history_lock);
1005
1006         commit_transaction->t_state = T_FINISHED;
1007         J_ASSERT(commit_transaction == journal->j_committing_transaction);
1008         journal->j_commit_sequence = commit_transaction->t_tid;
1009         journal->j_committing_transaction = NULL;
1010         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1011
1012         /*
1013          * weight the commit time higher than the average time so we don't
1014          * react too strongly to vast changes in the commit time
1015          */
1016         if (likely(journal->j_average_commit_time))
1017                 journal->j_average_commit_time = (commit_time +
1018                                 journal->j_average_commit_time*3) / 4;
1019         else
1020                 journal->j_average_commit_time = commit_time;
1021         spin_unlock(&journal->j_state_lock);
1022
1023         if (commit_transaction->t_checkpoint_list == NULL &&
1024             commit_transaction->t_checkpoint_io_list == NULL) {
1025                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1026                 to_free = 1;
1027         } else {
1028                 if (journal->j_checkpoint_transactions == NULL) {
1029                         journal->j_checkpoint_transactions = commit_transaction;
1030                         commit_transaction->t_cpnext = commit_transaction;
1031                         commit_transaction->t_cpprev = commit_transaction;
1032                 } else {
1033                         commit_transaction->t_cpnext =
1034                                 journal->j_checkpoint_transactions;
1035                         commit_transaction->t_cpprev =
1036                                 commit_transaction->t_cpnext->t_cpprev;
1037                         commit_transaction->t_cpnext->t_cpprev =
1038                                 commit_transaction;
1039                         commit_transaction->t_cpprev->t_cpnext =
1040                                 commit_transaction;
1041                 }
1042         }
1043         spin_unlock(&journal->j_list_lock);
1044
1045         if (journal->j_commit_callback)
1046                 journal->j_commit_callback(journal, commit_transaction);
1047
1048         trace_mark(jbd2_end_commit, "dev %s transaction %d head %d",
1049                    journal->j_devname, commit_transaction->t_tid,
1050                    journal->j_tail_sequence);
1051         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1052                   journal->j_commit_sequence, journal->j_tail_sequence);
1053         if (to_free)
1054                 kfree(commit_transaction);
1055
1056         wake_up(&journal->j_wait_done_commit);
1057 }