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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         int write_op = WRITE;
 371
 372         /*
 373          * First job: lock down the current transaction and wait for
 374          * all outstanding updates to complete.
 375          */
 376
 377 #ifdef COMMIT_STATS
 378         spin_lock(&journal->j_list_lock);
 379         summarise_journal_usage(journal);
 380         spin_unlock(&journal->j_list_lock);
 381 #endif
 382
 383         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 384         if (journal->j_flags & JBD2_FLUSHED) {
 385                 jbd_debug(3, "super block updated\n");
 386                 jbd2_journal_update_superblock(journal, 1);
 387         } else {
 388                 jbd_debug(3, "superblock not updated\n");
 389         }
 390
 391         J_ASSERT(journal->j_running_transaction != NULL);
 392         J_ASSERT(journal->j_committing_transaction == NULL);
 393
 394         commit_transaction = journal->j_running_transaction;
 395         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 396
 397         trace_mark(jbd2_start_commit, "dev %s transaction %d",
 398                    journal->j_devname, commit_transaction->t_tid);
 399         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 400                         commit_transaction->t_tid);
 401
 402         spin_lock(&journal->j_state_lock);
 403         commit_transaction->t_state = T_LOCKED;
 404
 405         if (commit_transaction->t_synchronous_commit)
 406                 write_op = WRITE_SYNC;
 407         stats.u.run.rs_wait = commit_transaction->t_max_wait;
 408         stats.u.run.rs_locked = jiffies;
 409         stats.u.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 410                                                 stats.u.run.rs_locked);
 411
 412         spin_lock(&commit_transaction->t_handle_lock);
 413         while (commit_transaction->t_updates) {
 414                 DEFINE_WAIT(wait);
 415
 416                 prepare_to_wait(&journal->j_wait_updates, &wait,
 417                                         TASK_UNINTERRUPTIBLE);
 418                 if (commit_transaction->t_updates) {
 419                         spin_unlock(&commit_transaction->t_handle_lock);
 420                         spin_unlock(&journal->j_state_lock);
 421                         schedule();
 422                         spin_lock(&journal->j_state_lock);
 423                         spin_lock(&commit_transaction->t_handle_lock);
 424                 }
 425                 finish_wait(&journal->j_wait_updates, &wait);
 426         }
 427         spin_unlock(&commit_transaction->t_handle_lock);
 428
 429         J_ASSERT (commit_transaction->t_outstanding_credits <=
 430                         journal->j_max_transaction_buffers);
 431
 432         /*
 433          * First thing we are allowed to do is to discard any remaining
 434          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 435          * that there are no such buffers: if a large filesystem
 436          * operation like a truncate needs to split itself over multiple
 437          * transactions, then it may try to do a jbd2_journal_restart() while
 438          * there are still BJ_Reserved buffers outstanding.  These must
 439          * be released cleanly from the current transaction.
 440          *
 441          * In this case, the filesystem must still reserve write access
 442          * again before modifying the buffer in the new transaction, but
 443          * we do not require it to remember exactly which old buffers it
 444          * has reserved.  This is consistent with the existing behaviour
 445          * that multiple jbd2_journal_get_write_access() calls to the same
 446          * buffer are perfectly permissable.
 447          */
 448         while (commit_transaction->t_reserved_list) {
 449                 jh = commit_transaction->t_reserved_list;
 450                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 451                 /*
 452                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 453                  * leave undo-committed data.
 454                  */
 455                 if (jh->b_committed_data) {
 456                         struct buffer_head *bh = jh2bh(jh);
 457
 458                         jbd_lock_bh_state(bh);
 459                         jbd2_free(jh->b_committed_data, bh->b_size);
 460                         jh->b_committed_data = NULL;
 461                         jbd_unlock_bh_state(bh);
 462                 }
 463                 jbd2_journal_refile_buffer(journal, jh);
 464         }
 465
 466         /*
 467          * Now try to drop any written-back buffers from the journal's
 468          * checkpoint lists.  We do this *before* commit because it potentially
 469          * frees some memory
 470          */
 471         spin_lock(&journal->j_list_lock);
 472         __jbd2_journal_clean_checkpoint_list(journal);
 473         spin_unlock(&journal->j_list_lock);
 474
 475         jbd_debug (3, "JBD: commit phase 1\n");
 476
 477         /*
 478          * Switch to a new revoke table.
 479          */
 480         jbd2_journal_switch_revoke_table(journal);
 481
 482         stats.u.run.rs_flushing = jiffies;
 483         stats.u.run.rs_locked = jbd2_time_diff(stats.u.run.rs_locked,
 484                                                stats.u.run.rs_flushing);
 485
 486         commit_transaction->t_state = T_FLUSH;
 487         journal->j_committing_transaction = commit_transaction;
 488         journal->j_running_transaction = NULL;
 489         start_time = ktime_get();
 490         commit_transaction->t_log_start = journal->j_head;
 491         wake_up(&journal->j_wait_transaction_locked);
 492         spin_unlock(&journal->j_state_lock);
 493
 494         jbd_debug (3, "JBD: commit phase 2\n");
 495
 496         /*
 497          * Now start flushing things to disk, in the order they appear
 498          * on the transaction lists.  Data blocks go first.
 499          */
 500         err = journal_submit_data_buffers(journal, commit_transaction);
 501         if (err)
 502                 jbd2_journal_abort(journal, err);
 503
 504         jbd2_journal_write_revoke_records(journal, commit_transaction);
 505
 506         jbd_debug(3, "JBD: commit phase 2\n");
 507
 508         /*
 509          * Way to go: we have now written out all of the data for a
 510          * transaction!  Now comes the tricky part: we need to write out
 511          * metadata.  Loop over the transaction's entire buffer list:
 512          */
 513         spin_lock(&journal->j_state_lock);
 514         commit_transaction->t_state = T_COMMIT;
 515         spin_unlock(&journal->j_state_lock);
 516
 517         stats.u.run.rs_logging = jiffies;
 518         stats.u.run.rs_flushing = jbd2_time_diff(stats.u.run.rs_flushing,
 519                                                  stats.u.run.rs_logging);
 520         stats.u.run.rs_blocks = commit_transaction->t_outstanding_credits;
 521         stats.u.run.rs_blocks_logged = 0;
 522
 523         J_ASSERT(commit_transaction->t_nr_buffers <=
 524                  commit_transaction->t_outstanding_credits);
 525
 526         err = 0;
 527         descriptor = NULL;
 528         bufs = 0;
 529         while (commit_transaction->t_buffers) {
 530
 531                 /* Find the next buffer to be journaled... */
 532
 533                 jh = commit_transaction->t_buffers;
 534
 535                 /* If we're in abort mode, we just un-journal the buffer and
 536                    release it. */
 537
 538                 if (is_journal_aborted(journal)) {
 539                         clear_buffer_jbddirty(jh2bh(jh));
 540                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 541                         jbd2_buffer_abort_trigger(jh,
 542                                                   jh->b_frozen_data ?
 543                                                   jh->b_frozen_triggers :
 544                                                   jh->b_triggers);
 545                         jbd2_journal_refile_buffer(journal, jh);
 546                         /* If that was the last one, we need to clean up
 547                          * any descriptor buffers which may have been
 548                          * already allocated, even if we are now
 549                          * aborting. */
 550                         if (!commit_transaction->t_buffers)
 551                                 goto start_journal_io;
 552                         continue;
 553                 }
 554
 555                 /* Make sure we have a descriptor block in which to
 556                    record the metadata buffer. */
 557
 558                 if (!descriptor) {
 559                         struct buffer_head *bh;
 560
 561                         J_ASSERT (bufs == 0);
 562
 563                         jbd_debug(4, "JBD: get descriptor\n");
 564
 565                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 566                         if (!descriptor) {
 567                                 jbd2_journal_abort(journal, -EIO);
 568                                 continue;
 569                         }
 570
 571                         bh = jh2bh(descriptor);
 572                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 573                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 574                         header = (journal_header_t *)&bh->b_data[0];
 575                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 576                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 577                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 578
 579                         tagp = &bh->b_data[sizeof(journal_header_t)];
 580                         space_left = bh->b_size - sizeof(journal_header_t);
 581                         first_tag = 1;
 582                         set_buffer_jwrite(bh);
 583                         set_buffer_dirty(bh);
 584                         wbuf[bufs++] = bh;
 585
 586                         /* Record it so that we can wait for IO
 587                            completion later */
 588                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 589                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 590                                         BJ_LogCtl);
 591                 }
 592
 593                 /* Where is the buffer to be written? */
 594
 595                 err = jbd2_journal_next_log_block(journal, &blocknr);
 596                 /* If the block mapping failed, just abandon the buffer
 597                    and repeat this loop: we'll fall into the
 598                    refile-on-abort condition above. */
 599                 if (err) {
 600                         jbd2_journal_abort(journal, err);
 601                         continue;
 602                 }
 603
 604                 /*
 605                  * start_this_handle() uses t_outstanding_credits to determine
 606                  * the free space in the log, but this counter is changed
 607                  * by jbd2_journal_next_log_block() also.
 608                  */
 609                 commit_transaction->t_outstanding_credits--;
 610
 611                 /* Bump b_count to prevent truncate from stumbling over
 612                    the shadowed buffer!  @@@ This can go if we ever get
 613                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 614                 atomic_inc(&jh2bh(jh)->b_count);
 615
 616                 /* Make a temporary IO buffer with which to write it out
 617                    (this will requeue both the metadata buffer and the
 618                    temporary IO buffer). new_bh goes on BJ_IO*/
 619
 620                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 621                 /*
 622                  * akpm: jbd2_journal_write_metadata_buffer() sets
 623                  * new_bh->b_transaction to commit_transaction.
 624                  * We need to clean this up before we release new_bh
 625                  * (which is of type BJ_IO)
 626                  */
 627                 JBUFFER_TRACE(jh, "ph3: write metadata");
 628                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 629                                                       jh, &new_jh, blocknr);
 630                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 631                 wbuf[bufs++] = jh2bh(new_jh);
 632
 633                 /* Record the new block's tag in the current descriptor
 634                    buffer */
 635
 636                 tag_flag = 0;
 637                 if (flags & 1)
 638                         tag_flag |= JBD2_FLAG_ESCAPE;
 639                 if (!first_tag)
 640                         tag_flag |= JBD2_FLAG_SAME_UUID;
 641
 642                 tag = (journal_block_tag_t *) tagp;
 643                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 644                 tag->t_flags = cpu_to_be32(tag_flag);
 645                 tagp += tag_bytes;
 646                 space_left -= tag_bytes;
 647
 648                 if (first_tag) {
 649                         memcpy (tagp, journal->j_uuid, 16);
 650                         tagp += 16;
 651                         space_left -= 16;
 652                         first_tag = 0;
 653                 }
 654
 655                 /* If there's no more to do, or if the descriptor is full,
 656                    let the IO rip! */
 657
 658                 if (bufs == journal->j_wbufsize ||
 659                     commit_transaction->t_buffers == NULL ||
 660                     space_left < tag_bytes + 16) {
 661
 662                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 663
 664                         /* Write an end-of-descriptor marker before
 665                            submitting the IOs.  "tag" still points to
 666                            the last tag we set up. */
 667
 668                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 669
 670 start_journal_io:
 671                         for (i = 0; i < bufs; i++) {
 672                                 struct buffer_head *bh = wbuf[i];
 673                                 /*
 674                                  * Compute checksum.
 675                                  */
 676                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 677                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 678                                         crc32_sum =
 679                                             jbd2_checksum_data(crc32_sum, bh);
 680                                 }
 681
 682                                 lock_buffer(bh);
 683                                 clear_buffer_dirty(bh);
 684                                 set_buffer_uptodate(bh);
 685                                 bh->b_end_io = journal_end_buffer_io_sync;
 686                                 submit_bh(write_op, bh);
 687                         }
 688                         cond_resched();
 689                         stats.u.run.rs_blocks_logged += bufs;
 690
 691                         /* Force a new descriptor to be generated next
 692                            time round the loop. */
 693                         descriptor = NULL;
 694                         bufs = 0;
 695                 }
 696         }
 697
 698         /* Done it all: now write the commit record asynchronously. */
 699
 700         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 701                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 702                 err = journal_submit_commit_record(journal, commit_transaction,
 703                                                  &cbh, crc32_sum);
 704                 if (err)
 705                         __jbd2_journal_abort_hard(journal);
 706         }
 707
 708         /*
 709          * This is the right place to wait for data buffers both for ASYNC
 710          * and !ASYNC commit. If commit is ASYNC, we need to wait only after
 711          * the commit block went to disk (which happens above). If commit is
 712          * SYNC, we need to wait for data buffers before we start writing
 713          * commit block, which happens below in such setting.
 714          */
 715         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 716         if (err) {
 717                 printk(KERN_WARNING
 718                         "JBD2: Detected IO errors while flushing file data "
 719                        "on %s\n", journal->j_devname);
 720                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 721                         jbd2_journal_abort(journal, err);
 722                 err = 0;
 723         }
 724
 725         /* Lo and behold: we have just managed to send a transaction to
 726            the log.  Before we can commit it, wait for the IO so far to
 727            complete.  Control buffers being written are on the
 728            transaction's t_log_list queue, and metadata buffers are on
 729            the t_iobuf_list queue.
 730
 731            Wait for the buffers in reverse order.  That way we are
 732            less likely to be woken up until all IOs have completed, and
 733            so we incur less scheduling load.
 734         */
 735
 736         jbd_debug(3, "JBD: commit phase 3\n");
 737
 738         /*
 739          * akpm: these are BJ_IO, and j_list_lock is not needed.
 740          * See __journal_try_to_free_buffer.
 741          */
 742 wait_for_iobuf:
 743         while (commit_transaction->t_iobuf_list != NULL) {
 744                 struct buffer_head *bh;
 745
 746                 jh = commit_transaction->t_iobuf_list->b_tprev;
 747                 bh = jh2bh(jh);
 748                 if (buffer_locked(bh)) {
 749                         wait_on_buffer(bh);
 750                         goto wait_for_iobuf;
 751                 }
 752                 if (cond_resched())
 753                         goto wait_for_iobuf;
 754
 755                 if (unlikely(!buffer_uptodate(bh)))
 756                         err = -EIO;
 757
 758                 clear_buffer_jwrite(bh);
 759
 760                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 761                 jbd2_journal_unfile_buffer(journal, jh);
 762
 763                 /*
 764                  * ->t_iobuf_list should contain only dummy buffer_heads
 765                  * which were created by jbd2_journal_write_metadata_buffer().
 766                  */
 767                 BUFFER_TRACE(bh, "dumping temporary bh");
 768                 jbd2_journal_put_journal_head(jh);
 769                 __brelse(bh);
 770                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 771                 free_buffer_head(bh);
 772
 773                 /* We also have to unlock and free the corresponding
 774                    shadowed buffer */
 775                 jh = commit_transaction->t_shadow_list->b_tprev;
 776                 bh = jh2bh(jh);
 777                 clear_bit(BH_JWrite, &bh->b_state);
 778                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 779
 780                 /* The metadata is now released for reuse, but we need
 781                    to remember it against this transaction so that when
 782                    we finally commit, we can do any checkpointing
 783                    required. */
 784                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 785                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 786                 /* Wake up any transactions which were waiting for this
 787                    IO to complete */
 788                 wake_up_bit(&bh->b_state, BH_Unshadow);
 789                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 790                 __brelse(bh);
 791         }
 792
 793         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 794
 795         jbd_debug(3, "JBD: commit phase 4\n");
 796
 797         /* Here we wait for the revoke record and descriptor record buffers */
 798  wait_for_ctlbuf:
 799         while (commit_transaction->t_log_list != NULL) {
 800                 struct buffer_head *bh;
 801
 802                 jh = commit_transaction->t_log_list->b_tprev;
 803                 bh = jh2bh(jh);
 804                 if (buffer_locked(bh)) {
 805                         wait_on_buffer(bh);
 806                         goto wait_for_ctlbuf;
 807                 }
 808                 if (cond_resched())
 809                         goto wait_for_ctlbuf;
 810
 811                 if (unlikely(!buffer_uptodate(bh)))
 812                         err = -EIO;
 813
 814                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 815                 clear_buffer_jwrite(bh);
 816                 jbd2_journal_unfile_buffer(journal, jh);
 817                 jbd2_journal_put_journal_head(jh);
 818                 __brelse(bh);           /* One for getblk */
 819                 /* AKPM: bforget here */
 820         }
 821
 822         if (err)
 823                 jbd2_journal_abort(journal, err);
 824
 825         jbd_debug(3, "JBD: commit phase 5\n");
 826
 827         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 828                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 829                 err = journal_submit_commit_record(journal, commit_transaction,
 830                                                 &cbh, crc32_sum);
 831                 if (err)
 832                         __jbd2_journal_abort_hard(journal);
 833         }
 834         if (!err && !is_journal_aborted(journal))
 835                 err = journal_wait_on_commit_record(journal, cbh);
 836
 837         if (err)
 838                 jbd2_journal_abort(journal, err);
 839
 840         /* End of a transaction!  Finally, we can do checkpoint
 841            processing: any buffers committed as a result of this
 842            transaction can be removed from any checkpoint list it was on
 843            before. */
 844
 845         jbd_debug(3, "JBD: commit phase 6\n");
 846
 847         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 848         J_ASSERT(commit_transaction->t_buffers == NULL);
 849         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 850         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 851         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 852         J_ASSERT(commit_transaction->t_log_list == NULL);
 853
 854 restart_loop:
 855         /*
 856          * As there are other places (journal_unmap_buffer()) adding buffers
 857          * to this list we have to be careful and hold the j_list_lock.
 858          */
 859         spin_lock(&journal->j_list_lock);
 860         while (commit_transaction->t_forget) {
 861                 transaction_t *cp_transaction;
 862                 struct buffer_head *bh;
 863
 864                 jh = commit_transaction->t_forget;
 865                 spin_unlock(&journal->j_list_lock);
 866                 bh = jh2bh(jh);
 867                 jbd_lock_bh_state(bh);
 868                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 869                         jh->b_transaction == journal->j_running_transaction);
 870
 871                 /*
 872                  * If there is undo-protected committed data against
 873                  * this buffer, then we can remove it now.  If it is a
 874                  * buffer needing such protection, the old frozen_data
 875                  * field now points to a committed version of the
 876                  * buffer, so rotate that field to the new committed
 877                  * data.
 878                  *
 879                  * Otherwise, we can just throw away the frozen data now.
 880                  *
 881                  * We also know that the frozen data has already fired
 882                  * its triggers if they exist, so we can clear that too.
 883                  */
 884                 if (jh->b_committed_data) {
 885                         jbd2_free(jh->b_committed_data, bh->b_size);
 886                         jh->b_committed_data = NULL;
 887                         if (jh->b_frozen_data) {
 888                                 jh->b_committed_data = jh->b_frozen_data;
 889                                 jh->b_frozen_data = NULL;
 890                                 jh->b_frozen_triggers = NULL;
 891                         }
 892                 } else if (jh->b_frozen_data) {
 893                         jbd2_free(jh->b_frozen_data, bh->b_size);
 894                         jh->b_frozen_data = NULL;
 895                         jh->b_frozen_triggers = NULL;
 896                 }
 897
 898                 spin_lock(&journal->j_list_lock);
 899                 cp_transaction = jh->b_cp_transaction;
 900                 if (cp_transaction) {
 901                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 902                         cp_transaction->t_chp_stats.cs_dropped++;
 903                         __jbd2_journal_remove_checkpoint(jh);
 904                 }
 905
 906                 /* Only re-checkpoint the buffer_head if it is marked
 907                  * dirty.  If the buffer was added to the BJ_Forget list
 908                  * by jbd2_journal_forget, it may no longer be dirty and
 909                  * there's no point in keeping a checkpoint record for
 910                  * it. */
 911
 912                 /* A buffer which has been freed while still being
 913                  * journaled by a previous transaction may end up still
 914                  * being dirty here, but we want to avoid writing back
 915                  * that buffer in the future now that the last use has
 916                  * been committed.  That's not only a performance gain,
 917                  * it also stops aliasing problems if the buffer is left
 918                  * behind for writeback and gets reallocated for another
 919                  * use in a different page. */
 920                 if (buffer_freed(bh)) {
 921                         clear_buffer_freed(bh);
 922                         clear_buffer_jbddirty(bh);
 923                 }
 924
 925                 if (buffer_jbddirty(bh)) {
 926                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 927                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 928                         if (is_journal_aborted(journal))
 929                                 clear_buffer_jbddirty(bh);
 930                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 931                         __jbd2_journal_refile_buffer(jh);
 932                         jbd_unlock_bh_state(bh);
 933                 } else {
 934                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 935                         /* The buffer on BJ_Forget list and not jbddirty means
 936                          * it has been freed by this transaction and hence it
 937                          * could not have been reallocated until this
 938                          * transaction has committed. *BUT* it could be
 939                          * reallocated once we have written all the data to
 940                          * disk and before we process the buffer on BJ_Forget
 941                          * list. */
 942                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 943                         __jbd2_journal_refile_buffer(jh);
 944                         if (!jh->b_transaction) {
 945                                 jbd_unlock_bh_state(bh);
 946                                  /* needs a brelse */
 947                                 jbd2_journal_remove_journal_head(bh);
 948                                 release_buffer_page(bh);
 949                         } else
 950                                 jbd_unlock_bh_state(bh);
 951                 }
 952                 cond_resched_lock(&journal->j_list_lock);
 953         }
 954         spin_unlock(&journal->j_list_lock);
 955         /*
 956          * This is a bit sleazy.  We use j_list_lock to protect transition
 957          * of a transaction into T_FINISHED state and calling
 958          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 959          * other checkpointing code processing the transaction...
 960          */
 961         spin_lock(&journal->j_state_lock);
 962         spin_lock(&journal->j_list_lock);
 963         /*
 964          * Now recheck if some buffers did not get attached to the transaction
 965          * while the lock was dropped...
 966          */
 967         if (commit_transaction->t_forget) {
 968                 spin_unlock(&journal->j_list_lock);
 969                 spin_unlock(&journal->j_state_lock);
 970                 goto restart_loop;
 971         }
 972
 973         /* Done with this transaction! */
 974
 975         jbd_debug(3, "JBD: commit phase 7\n");
 976
 977         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 978
 979         commit_transaction->t_start = jiffies;
 980         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
 981                                                 commit_transaction->t_start);
 982
 983         /*
 984          * File the transaction for history
 985          */
 986         stats.ts_type = JBD2_STATS_RUN;
 987         stats.ts_tid = commit_transaction->t_tid;
 988         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
 989         spin_lock(&journal->j_history_lock);
 990         memcpy(journal->j_history + journal->j_history_cur, &stats,
 991                         sizeof(stats));
 992         if (++journal->j_history_cur == journal->j_history_max)
 993                 journal->j_history_cur = 0;
 994
 995         /*
 996          * Calculate overall stats
 997          */
 998         journal->j_stats.ts_tid++;
 999         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
1000         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
1001         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
1002         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
1003         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
1004         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
1005         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
1006         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
1007         spin_unlock(&journal->j_history_lock);
1008
1009         commit_transaction->t_state = T_FINISHED;
1010         J_ASSERT(commit_transaction == journal->j_committing_transaction);
1011         journal->j_commit_sequence = commit_transaction->t_tid;
1012         journal->j_committing_transaction = NULL;
1013         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1014
1015         /*
1016          * weight the commit time higher than the average time so we don't
1017          * react too strongly to vast changes in the commit time
1018          */
1019         if (likely(journal->j_average_commit_time))
1020                 journal->j_average_commit_time = (commit_time +
1021                                 journal->j_average_commit_time*3) / 4;
1022         else
1023                 journal->j_average_commit_time = commit_time;
1024         spin_unlock(&journal->j_state_lock);
1025
1026         if (commit_transaction->t_checkpoint_list == NULL &&
1027             commit_transaction->t_checkpoint_io_list == NULL) {
1028                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1029                 to_free = 1;
1030         } else {
1031                 if (journal->j_checkpoint_transactions == NULL) {
1032                         journal->j_checkpoint_transactions = commit_transaction;
1033                         commit_transaction->t_cpnext = commit_transaction;
1034                         commit_transaction->t_cpprev = commit_transaction;
1035                 } else {
1036                         commit_transaction->t_cpnext =
1037                                 journal->j_checkpoint_transactions;
1038                         commit_transaction->t_cpprev =
1039                                 commit_transaction->t_cpnext->t_cpprev;
1040                         commit_transaction->t_cpnext->t_cpprev =
1041                                 commit_transaction;
1042                         commit_transaction->t_cpprev->t_cpnext =
1043                                 commit_transaction;
1044                 }
1045         }
1046         spin_unlock(&journal->j_list_lock);
1047
1048         if (journal->j_commit_callback)
1049                 journal->j_commit_callback(journal, commit_transaction);
1050
1051         trace_mark(jbd2_end_commit, "dev %s transaction %d head %d",
1052                    journal->j_devname, commit_transaction->t_tid,
1053                    journal->j_tail_sequence);
1054         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1055                   journal->j_commit_sequence, journal->j_tail_sequence);
1056         if (to_free)
1057                 kfree(commit_transaction);
1058
1059         wake_up(&journal->j_wait_done_commit);
1060 }