fs/jbd2/commit.c

   1 /*
   2  * linux/fs/jbd2/commit.c
   3  *
   4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
   5  *
   6  * Copyright 1998 Red Hat corp --- All Rights Reserved
   7  *
   8  * This file is part of the Linux kernel and is made available under
   9  * the terms of the GNU General Public License, version 2, or at your
  10  * option, any later version, incorporated herein by reference.
  11  *
  12  * Journal commit routines for the generic filesystem journaling code;
  13  * part of the ext2fs journaling system.
  14  */
  15
  16 #include <linux/time.h>
  17 #include <linux/fs.h>
  18 #include <linux/jbd2.h>
  19 #include <linux/errno.h>
  20 #include <linux/slab.h>
  21 #include <linux/mm.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/jiffies.h>
  24 #include <linux/crc32.h>
  25 #include <linux/writeback.h>
  26 #include <linux/backing-dev.h>
  27 #include <linux/bio.h>
  28 #include <linux/blkdev.h>
  29 #include <trace/events/jbd2.h>
  30
  31 /*
  32  * Default IO end handler for temporary BJ_IO buffer_heads.
  33  */
  34 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
  35 {
  36         BUFFER_TRACE(bh, "");
  37         if (uptodate)
  38                 set_buffer_uptodate(bh);
  39         else
  40                 clear_buffer_uptodate(bh);
  41         unlock_buffer(bh);
  42 }
  43
  44 /*
  45  * When an ext4 file is truncated, it is possible that some pages are not
  46  * successfully freed, because they are attached to a committing transaction.
  47  * After the transaction commits, these pages are left on the LRU, with no
  48  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
  49  * by the VM, but their apparent absence upsets the VM accounting, and it makes
  50  * the numbers in /proc/meminfo look odd.
  51  *
  52  * So here, we have a buffer which has just come off the forget list.  Look to
  53  * see if we can strip all buffers from the backing page.
  54  *
  55  * Called under lock_journal(), and possibly under journal_datalist_lock.  The
  56  * caller provided us with a ref against the buffer, and we drop that here.
  57  */
  58 static void release_buffer_page(struct buffer_head *bh)
  59 {
  60         struct page *page;
  61
  62         if (buffer_dirty(bh))
  63                 goto nope;
  64         if (atomic_read(&bh->b_count) != 1)
  65                 goto nope;
  66         page = bh->b_page;
  67         if (!page)
  68                 goto nope;
  69         if (page->mapping)
  70                 goto nope;
  71
  72         /* OK, it's a truncated page */
  73         if (!trylock_page(page))
  74                 goto nope;
  75
  76         page_cache_get(page);
  77         __brelse(bh);
  78         try_to_free_buffers(page);
  79         unlock_page(page);
  80         page_cache_release(page);
  81         return;
  82
  83 nope:
  84         __brelse(bh);
  85 }
  86
  87 /*
  88  * Done it all: now submit the commit record.  We should have
  89  * cleaned up our previous buffers by now, so if we are in abort
  90  * mode we can now just skip the rest of the journal write
  91  * entirely.
  92  *
  93  * Returns 1 if the journal needs to be aborted or 0 on success
  94  */
  95 static int journal_submit_commit_record(journal_t *journal,
  96                                         transaction_t *commit_transaction,
  97                                         struct buffer_head **cbh,
  98                                         __u32 crc32_sum)
  99 {
 100         struct journal_head *descriptor;
 101         struct commit_header *tmp;
 102         struct buffer_head *bh;
 103         int ret;
 104         int barrier_done = 0;
 105         struct timespec now = current_kernel_time();
 106
 107         if (is_journal_aborted(journal))
 108                 return 0;
 109
 110         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 111         if (!descriptor)
 112                 return 1;
 113
 114         bh = jh2bh(descriptor);
 115
 116         tmp = (struct commit_header *)bh->b_data;
 117         tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
 118         tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
 119         tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 120         tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
 121         tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);
 122
 123         if (JBD2_HAS_COMPAT_FEATURE(journal,
 124                                     JBD2_FEATURE_COMPAT_CHECKSUM)) {
 125                 tmp->h_chksum_type      = JBD2_CRC32_CHKSUM;
 126                 tmp->h_chksum_size      = JBD2_CRC32_CHKSUM_SIZE;
 127                 tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
 128         }
 129
 130         JBUFFER_TRACE(descriptor, "submit commit block");
 131         lock_buffer(bh);
 132         clear_buffer_dirty(bh);
 133         set_buffer_uptodate(bh);
 134         bh->b_end_io = journal_end_buffer_io_sync;
 135
 136         if (journal->j_flags & JBD2_BARRIER &&
 137             !JBD2_HAS_INCOMPAT_FEATURE(journal,
 138                                        JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 139                 set_buffer_ordered(bh);
 140                 barrier_done = 1;
 141         }
 142         ret = submit_bh(WRITE_SYNC_PLUG, bh);
 143         if (barrier_done)
 144                 clear_buffer_ordered(bh);
 145
 146         /* is it possible for another commit to fail at roughly
 147          * the same time as this one?  If so, we don't want to
 148          * trust the barrier flag in the super, but instead want
 149          * to remember if we sent a barrier request
 150          */
 151         if (ret == -EOPNOTSUPP && barrier_done) {
 152                 printk(KERN_WARNING
 153                        "JBD: barrier-based sync failed on %s - "
 154                        "disabling barriers\n", journal->j_devname);
 155                 spin_lock(&journal->j_state_lock);
 156                 journal->j_flags &= ~JBD2_BARRIER;
 157                 spin_unlock(&journal->j_state_lock);
 158
 159                 /* And try again, without the barrier */
 160                 lock_buffer(bh);
 161                 set_buffer_uptodate(bh);
 162                 clear_buffer_dirty(bh);
 163                 ret = submit_bh(WRITE_SYNC_PLUG, bh);
 164         }
 165         *cbh = bh;
 166         return ret;
 167 }
 168
 169 /*
 170  * This function along with journal_submit_commit_record
 171  * allows to write the commit record asynchronously.
 172  */
 173 static int journal_wait_on_commit_record(journal_t *journal,
 174                                          struct buffer_head *bh)
 175 {
 176         int ret = 0;
 177
 178 retry:
 179         clear_buffer_dirty(bh);
 180         wait_on_buffer(bh);
 181         if (buffer_eopnotsupp(bh) && (journal->j_flags & JBD2_BARRIER)) {
 182                 printk(KERN_WARNING
 183                        "JBD2: wait_on_commit_record: sync failed on %s - "
 184                        "disabling barriers\n", journal->j_devname);
 185                 spin_lock(&journal->j_state_lock);
 186                 journal->j_flags &= ~JBD2_BARRIER;
 187                 spin_unlock(&journal->j_state_lock);
 188
 189                 lock_buffer(bh);
 190                 clear_buffer_dirty(bh);
 191                 set_buffer_uptodate(bh);
 192                 bh->b_end_io = journal_end_buffer_io_sync;
 193
 194                 ret = submit_bh(WRITE_SYNC_PLUG, bh);
 195                 if (ret) {
 196                         unlock_buffer(bh);
 197                         return ret;
 198                 }
 199                 goto retry;
 200         }
 201
 202         if (unlikely(!buffer_uptodate(bh)))
 203                 ret = -EIO;
 204         put_bh(bh);            /* One for getblk() */
 205         jbd2_journal_put_journal_head(bh2jh(bh));
 206
 207         return ret;
 208 }
 209
 210 /*
 211  * write the filemap data using writepage() address_space_operations.
 212  * We don't do block allocation here even for delalloc. We don't
 213  * use writepages() because with dealyed allocation we may be doing
 214  * block allocation in writepages().
 215  */
 216 static int journal_submit_inode_data_buffers(struct address_space *mapping)
 217 {
 218         int ret;
 219         struct writeback_control wbc = {
 220                 .sync_mode =  WB_SYNC_ALL,
 221                 .nr_to_write = mapping->nrpages * 2,
 222                 .range_start = 0,
 223                 .range_end = i_size_read(mapping->host),
 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                 trace_jbd2_submit_inode_data(jinode->i_vfs_inode);
 257                 err = journal_submit_inode_data_buffers(mapping);
 258                 if (!ret)
 259                         ret = err;
 260                 spin_lock(&journal->j_list_lock);
 261                 J_ASSERT(jinode->i_transaction == commit_transaction);
 262                 commit_transaction->t_flushed_data_blocks = 1;
 263                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 264                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 265         }
 266         spin_unlock(&journal->j_list_lock);
 267         return ret;
 268 }
 269
 270 /*
 271  * Wait for data submitted for writeout, refile inodes to proper
 272  * transaction if needed.
 273  *
 274  */
 275 static int journal_finish_inode_data_buffers(journal_t *journal,
 276                 transaction_t *commit_transaction)
 277 {
 278         struct jbd2_inode *jinode, *next_i;
 279         int err, ret = 0;
 280
 281         /* For locking, see the comment in journal_submit_data_buffers() */
 282         spin_lock(&journal->j_list_lock);
 283         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 284                 jinode->i_flags |= JI_COMMIT_RUNNING;
 285                 spin_unlock(&journal->j_list_lock);
 286                 err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
 287                 if (err) {
 288                         /*
 289                          * Because AS_EIO is cleared by
 290                          * filemap_fdatawait_range(), set it again so
 291                          * that user process can get -EIO from fsync().
 292                          */
 293                         set_bit(AS_EIO,
 294                                 &jinode->i_vfs_inode->i_mapping->flags);
 295
 296                         if (!ret)
 297                                 ret = err;
 298                 }
 299                 spin_lock(&journal->j_list_lock);
 300                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 301                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 302         }
 303
 304         /* Now refile inode to proper lists */
 305         list_for_each_entry_safe(jinode, next_i,
 306                                  &commit_transaction->t_inode_list, i_list) {
 307                 list_del(&jinode->i_list);
 308                 if (jinode->i_next_transaction) {
 309                         jinode->i_transaction = jinode->i_next_transaction;
 310                         jinode->i_next_transaction = NULL;
 311                         list_add(&jinode->i_list,
 312                                 &jinode->i_transaction->t_inode_list);
 313                 } else {
 314                         jinode->i_transaction = NULL;
 315                 }
 316         }
 317         spin_unlock(&journal->j_list_lock);
 318
 319         return ret;
 320 }
 321
 322 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 323 {
 324         struct page *page = bh->b_page;
 325         char *addr;
 326         __u32 checksum;
 327
 328         addr = kmap_atomic(page, KM_USER0);
 329         checksum = crc32_be(crc32_sum,
 330                 (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
 331         kunmap_atomic(addr, KM_USER0);
 332
 333         return checksum;
 334 }
 335
 336 static void write_tag_block(int tag_bytes, journal_block_tag_t *tag,
 337                                    unsigned long long block)
 338 {
 339         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
 340         if (tag_bytes > JBD2_TAG_SIZE32)
 341                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
 342 }
 343
 344 /*
 345  * jbd2_journal_commit_transaction
 346  *
 347  * The primary function for committing a transaction to the log.  This
 348  * function is called by the journal thread to begin a complete commit.
 349  */
 350 void jbd2_journal_commit_transaction(journal_t *journal)
 351 {
 352         struct transaction_stats_s stats;
 353         transaction_t *commit_transaction;
 354         struct journal_head *jh, *new_jh, *descriptor;
 355         struct buffer_head **wbuf = journal->j_wbuf;
 356         int bufs;
 357         int flags;
 358         int err;
 359         unsigned long long blocknr;
 360         ktime_t start_time;
 361         u64 commit_time;
 362         char *tagp = NULL;
 363         journal_header_t *header;
 364         journal_block_tag_t *tag = NULL;
 365         int space_left = 0;
 366         int first_tag = 0;
 367         int tag_flag;
 368         int i, to_free = 0;
 369         int tag_bytes = journal_tag_bytes(journal);
 370         struct buffer_head *cbh = NULL; /* For transactional checksums */
 371         __u32 crc32_sum = ~0;
 372         int write_op = WRITE;
 373
 374         /*
 375          * First job: lock down the current transaction and wait for
 376          * all outstanding updates to complete.
 377          */
 378
 379 #ifdef COMMIT_STATS
 380         spin_lock(&journal->j_list_lock);
 381         summarise_journal_usage(journal);
 382         spin_unlock(&journal->j_list_lock);
 383 #endif
 384
 385         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 386         if (journal->j_flags & JBD2_FLUSHED) {
 387                 jbd_debug(3, "super block updated\n");
 388                 jbd2_journal_update_superblock(journal, 1);
 389         } else {
 390                 jbd_debug(3, "superblock not updated\n");
 391         }
 392
 393         J_ASSERT(journal->j_running_transaction != NULL);
 394         J_ASSERT(journal->j_committing_transaction == NULL);
 395
 396         commit_transaction = journal->j_running_transaction;
 397         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 398
 399         trace_jbd2_start_commit(journal, commit_transaction);
 400         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 401                         commit_transaction->t_tid);
 402
 403         spin_lock(&journal->j_state_lock);
 404         commit_transaction->t_state = T_LOCKED;
 405
 406         /*
 407          * Use plugged writes here, since we want to submit several before
 408          * we unplug the device. We don't do explicit unplugging in here,
 409          * instead we rely on sync_buffer() doing the unplug for us.
 410          */
 411         if (commit_transaction->t_synchronous_commit)
 412                 write_op = WRITE_SYNC_PLUG;
 413         trace_jbd2_commit_locking(journal, commit_transaction);
 414         stats.run.rs_wait = commit_transaction->t_max_wait;
 415         stats.run.rs_locked = jiffies;
 416         stats.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 417                                               stats.run.rs_locked);
 418
 419         spin_lock(&commit_transaction->t_handle_lock);
 420         while (commit_transaction->t_updates) {
 421                 DEFINE_WAIT(wait);
 422
 423                 prepare_to_wait(&journal->j_wait_updates, &wait,
 424                                         TASK_UNINTERRUPTIBLE);
 425                 if (commit_transaction->t_updates) {
 426                         spin_unlock(&commit_transaction->t_handle_lock);
 427                         spin_unlock(&journal->j_state_lock);
 428                         schedule();
 429                         spin_lock(&journal->j_state_lock);
 430                         spin_lock(&commit_transaction->t_handle_lock);
 431                 }
 432                 finish_wait(&journal->j_wait_updates, &wait);
 433         }
 434         spin_unlock(&commit_transaction->t_handle_lock);
 435
 436         J_ASSERT (commit_transaction->t_outstanding_credits <=
 437                         journal->j_max_transaction_buffers);
 438
 439         /*
 440          * First thing we are allowed to do is to discard any remaining
 441          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 442          * that there are no such buffers: if a large filesystem
 443          * operation like a truncate needs to split itself over multiple
 444          * transactions, then it may try to do a jbd2_journal_restart() while
 445          * there are still BJ_Reserved buffers outstanding.  These must
 446          * be released cleanly from the current transaction.
 447          *
 448          * In this case, the filesystem must still reserve write access
 449          * again before modifying the buffer in the new transaction, but
 450          * we do not require it to remember exactly which old buffers it
 451          * has reserved.  This is consistent with the existing behaviour
 452          * that multiple jbd2_journal_get_write_access() calls to the same
 453          * buffer are perfectly permissable.
 454          */
 455         while (commit_transaction->t_reserved_list) {
 456                 jh = commit_transaction->t_reserved_list;
 457                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 458                 /*
 459                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 460                  * leave undo-committed data.
 461                  */
 462                 if (jh->b_committed_data) {
 463                         struct buffer_head *bh = jh2bh(jh);
 464
 465                         jbd_lock_bh_state(bh);
 466                         jbd2_free(jh->b_committed_data, bh->b_size);
 467                         jh->b_committed_data = NULL;
 468                         jbd_unlock_bh_state(bh);
 469                 }
 470                 jbd2_journal_refile_buffer(journal, jh);
 471         }
 472
 473         /*
 474          * Now try to drop any written-back buffers from the journal's
 475          * checkpoint lists.  We do this *before* commit because it potentially
 476          * frees some memory
 477          */
 478         spin_lock(&journal->j_list_lock);
 479         __jbd2_journal_clean_checkpoint_list(journal);
 480         spin_unlock(&journal->j_list_lock);
 481
 482         jbd_debug (3, "JBD: commit phase 1\n");
 483
 484         /*
 485          * Switch to a new revoke table.
 486          */
 487         jbd2_journal_switch_revoke_table(journal);
 488
 489         trace_jbd2_commit_flushing(journal, commit_transaction);
 490         stats.run.rs_flushing = jiffies;
 491         stats.run.rs_locked = jbd2_time_diff(stats.run.rs_locked,
 492                                              stats.run.rs_flushing);
 493
 494         commit_transaction->t_state = T_FLUSH;
 495         journal->j_committing_transaction = commit_transaction;
 496         journal->j_running_transaction = NULL;
 497         start_time = ktime_get();
 498         commit_transaction->t_log_start = journal->j_head;
 499         wake_up(&journal->j_wait_transaction_locked);
 500         spin_unlock(&journal->j_state_lock);
 501
 502         jbd_debug (3, "JBD: commit phase 2\n");
 503
 504         /*
 505          * Now start flushing things to disk, in the order they appear
 506          * on the transaction lists.  Data blocks go first.
 507          */
 508         err = journal_submit_data_buffers(journal, commit_transaction);
 509         if (err)
 510                 jbd2_journal_abort(journal, err);
 511
 512         jbd2_journal_write_revoke_records(journal, commit_transaction,
 513                                           write_op);
 514
 515         jbd_debug(3, "JBD: commit phase 2\n");
 516
 517         /*
 518          * Way to go: we have now written out all of the data for a
 519          * transaction!  Now comes the tricky part: we need to write out
 520          * metadata.  Loop over the transaction's entire buffer list:
 521          */
 522         spin_lock(&journal->j_state_lock);
 523         commit_transaction->t_state = T_COMMIT;
 524         spin_unlock(&journal->j_state_lock);
 525
 526         trace_jbd2_commit_logging(journal, commit_transaction);
 527         stats.run.rs_logging = jiffies;
 528         stats.run.rs_flushing = jbd2_time_diff(stats.run.rs_flushing,
 529                                                stats.run.rs_logging);
 530         stats.run.rs_blocks = commit_transaction->t_outstanding_credits;
 531         stats.run.rs_blocks_logged = 0;
 532
 533         J_ASSERT(commit_transaction->t_nr_buffers <=
 534                  commit_transaction->t_outstanding_credits);
 535
 536         err = 0;
 537         descriptor = NULL;
 538         bufs = 0;
 539         while (commit_transaction->t_buffers) {
 540
 541                 /* Find the next buffer to be journaled... */
 542
 543                 jh = commit_transaction->t_buffers;
 544
 545                 /* If we're in abort mode, we just un-journal the buffer and
 546                    release it. */
 547
 548                 if (is_journal_aborted(journal)) {
 549                         clear_buffer_jbddirty(jh2bh(jh));
 550                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 551                         jbd2_buffer_abort_trigger(jh,
 552                                                   jh->b_frozen_data ?
 553                                                   jh->b_frozen_triggers :
 554                                                   jh->b_triggers);
 555                         jbd2_journal_refile_buffer(journal, jh);
 556                         /* If that was the last one, we need to clean up
 557                          * any descriptor buffers which may have been
 558                          * already allocated, even if we are now
 559                          * aborting. */
 560                         if (!commit_transaction->t_buffers)
 561                                 goto start_journal_io;
 562                         continue;
 563                 }
 564
 565                 /* Make sure we have a descriptor block in which to
 566                    record the metadata buffer. */
 567
 568                 if (!descriptor) {
 569                         struct buffer_head *bh;
 570
 571                         J_ASSERT (bufs == 0);
 572
 573                         jbd_debug(4, "JBD: get descriptor\n");
 574
 575                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 576                         if (!descriptor) {
 577                                 jbd2_journal_abort(journal, -EIO);
 578                                 continue;
 579                         }
 580
 581                         bh = jh2bh(descriptor);
 582                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 583                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 584                         header = (journal_header_t *)&bh->b_data[0];
 585                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 586                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 587                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 588
 589                         tagp = &bh->b_data[sizeof(journal_header_t)];
 590                         space_left = bh->b_size - sizeof(journal_header_t);
 591                         first_tag = 1;
 592                         set_buffer_jwrite(bh);
 593                         set_buffer_dirty(bh);
 594                         wbuf[bufs++] = bh;
 595
 596                         /* Record it so that we can wait for IO
 597                            completion later */
 598                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 599                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 600                                         BJ_LogCtl);
 601                 }
 602
 603                 /* Where is the buffer to be written? */
 604
 605                 err = jbd2_journal_next_log_block(journal, &blocknr);
 606                 /* If the block mapping failed, just abandon the buffer
 607                    and repeat this loop: we'll fall into the
 608                    refile-on-abort condition above. */
 609                 if (err) {
 610                         jbd2_journal_abort(journal, err);
 611                         continue;
 612                 }
 613
 614                 /*
 615                  * start_this_handle() uses t_outstanding_credits to determine
 616                  * the free space in the log, but this counter is changed
 617                  * by jbd2_journal_next_log_block() also.
 618                  */
 619                 commit_transaction->t_outstanding_credits--;
 620
 621                 /* Bump b_count to prevent truncate from stumbling over
 622                    the shadowed buffer!  @@@ This can go if we ever get
 623                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 624                 atomic_inc(&jh2bh(jh)->b_count);
 625
 626                 /* Make a temporary IO buffer with which to write it out
 627                    (this will requeue both the metadata buffer and the
 628                    temporary IO buffer). new_bh goes on BJ_IO*/
 629
 630                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 631                 /*
 632                  * akpm: jbd2_journal_write_metadata_buffer() sets
 633                  * new_bh->b_transaction to commit_transaction.
 634                  * We need to clean this up before we release new_bh
 635                  * (which is of type BJ_IO)
 636                  */
 637                 JBUFFER_TRACE(jh, "ph3: write metadata");
 638                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 639                                                       jh, &new_jh, blocknr);
 640                 if (flags < 0) {
 641                         jbd2_journal_abort(journal, flags);
 642                         continue;
 643                 }
 644                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 645                 wbuf[bufs++] = jh2bh(new_jh);
 646
 647                 /* Record the new block's tag in the current descriptor
 648                    buffer */
 649
 650                 tag_flag = 0;
 651                 if (flags & 1)
 652                         tag_flag |= JBD2_FLAG_ESCAPE;
 653                 if (!first_tag)
 654                         tag_flag |= JBD2_FLAG_SAME_UUID;
 655
 656                 tag = (journal_block_tag_t *) tagp;
 657                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 658                 tag->t_flags = cpu_to_be32(tag_flag);
 659                 tagp += tag_bytes;
 660                 space_left -= tag_bytes;
 661
 662                 if (first_tag) {
 663                         memcpy (tagp, journal->j_uuid, 16);
 664                         tagp += 16;
 665                         space_left -= 16;
 666                         first_tag = 0;
 667                 }
 668
 669                 /* If there's no more to do, or if the descriptor is full,
 670                    let the IO rip! */
 671
 672                 if (bufs == journal->j_wbufsize ||
 673                     commit_transaction->t_buffers == NULL ||
 674                     space_left < tag_bytes + 16) {
 675
 676                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 677
 678                         /* Write an end-of-descriptor marker before
 679                            submitting the IOs.  "tag" still points to
 680                            the last tag we set up. */
 681
 682                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 683
 684 start_journal_io:
 685                         for (i = 0; i < bufs; i++) {
 686                                 struct buffer_head *bh = wbuf[i];
 687                                 /*
 688                                  * Compute checksum.
 689                                  */
 690                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 691                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 692                                         crc32_sum =
 693                                             jbd2_checksum_data(crc32_sum, bh);
 694                                 }
 695
 696                                 lock_buffer(bh);
 697                                 clear_buffer_dirty(bh);
 698                                 set_buffer_uptodate(bh);
 699                                 bh->b_end_io = journal_end_buffer_io_sync;
 700                                 submit_bh(write_op, bh);
 701                         }
 702                         cond_resched();
 703                         stats.run.rs_blocks_logged += bufs;
 704
 705                         /* Force a new descriptor to be generated next
 706                            time round the loop. */
 707                         descriptor = NULL;
 708                         bufs = 0;
 709                 }
 710         }
 711
 712         /*
 713          * If the journal is not located on the file system device,
 714          * then we must flush the file system device before we issue
 715          * the commit record
 716          */
 717         if (commit_transaction->t_flushed_data_blocks &&
 718             (journal->j_fs_dev != journal->j_dev) &&
 719             (journal->j_flags & JBD2_BARRIER))
 720                 blkdev_issue_flush(journal->j_fs_dev, NULL);
 721
 722         /* Done it all: now write the commit record asynchronously. */
 723         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 724                                       JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 725                 err = journal_submit_commit_record(journal, commit_transaction,
 726                                                  &cbh, crc32_sum);
 727                 if (err)
 728                         __jbd2_journal_abort_hard(journal);
 729                 if (journal->j_flags & JBD2_BARRIER)
 730                         blkdev_issue_flush(journal->j_dev, NULL);
 731         }
 732
 733         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 734         if (err) {
 735                 printk(KERN_WARNING
 736                         "JBD2: Detected IO errors while flushing file data "
 737                        "on %s\n", journal->j_devname);
 738                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 739                         jbd2_journal_abort(journal, err);
 740                 err = 0;
 741         }
 742
 743         /* Lo and behold: we have just managed to send a transaction to
 744            the log.  Before we can commit it, wait for the IO so far to
 745            complete.  Control buffers being written are on the
 746            transaction's t_log_list queue, and metadata buffers are on
 747            the t_iobuf_list queue.
 748
 749            Wait for the buffers in reverse order.  That way we are
 750            less likely to be woken up until all IOs have completed, and
 751            so we incur less scheduling load.
 752         */
 753
 754         jbd_debug(3, "JBD: commit phase 3\n");
 755
 756         /*
 757          * akpm: these are BJ_IO, and j_list_lock is not needed.
 758          * See __journal_try_to_free_buffer.
 759          */
 760 wait_for_iobuf:
 761         while (commit_transaction->t_iobuf_list != NULL) {
 762                 struct buffer_head *bh;
 763
 764                 jh = commit_transaction->t_iobuf_list->b_tprev;
 765                 bh = jh2bh(jh);
 766                 if (buffer_locked(bh)) {
 767                         wait_on_buffer(bh);
 768                         goto wait_for_iobuf;
 769                 }
 770                 if (cond_resched())
 771                         goto wait_for_iobuf;
 772
 773                 if (unlikely(!buffer_uptodate(bh)))
 774                         err = -EIO;
 775
 776                 clear_buffer_jwrite(bh);
 777
 778                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 779                 jbd2_journal_unfile_buffer(journal, jh);
 780
 781                 /*
 782                  * ->t_iobuf_list should contain only dummy buffer_heads
 783                  * which were created by jbd2_journal_write_metadata_buffer().
 784                  */
 785                 BUFFER_TRACE(bh, "dumping temporary bh");
 786                 jbd2_journal_put_journal_head(jh);
 787                 __brelse(bh);
 788                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 789                 free_buffer_head(bh);
 790
 791                 /* We also have to unlock and free the corresponding
 792                    shadowed buffer */
 793                 jh = commit_transaction->t_shadow_list->b_tprev;
 794                 bh = jh2bh(jh);
 795                 clear_bit(BH_JWrite, &bh->b_state);
 796                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 797
 798                 /* The metadata is now released for reuse, but we need
 799                    to remember it against this transaction so that when
 800                    we finally commit, we can do any checkpointing
 801                    required. */
 802                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 803                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 804                 /* Wake up any transactions which were waiting for this
 805                    IO to complete */
 806                 wake_up_bit(&bh->b_state, BH_Unshadow);
 807                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 808                 __brelse(bh);
 809         }
 810
 811         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 812
 813         jbd_debug(3, "JBD: commit phase 4\n");
 814
 815         /* Here we wait for the revoke record and descriptor record buffers */
 816  wait_for_ctlbuf:
 817         while (commit_transaction->t_log_list != NULL) {
 818                 struct buffer_head *bh;
 819
 820                 jh = commit_transaction->t_log_list->b_tprev;
 821                 bh = jh2bh(jh);
 822                 if (buffer_locked(bh)) {
 823                         wait_on_buffer(bh);
 824                         goto wait_for_ctlbuf;
 825                 }
 826                 if (cond_resched())
 827                         goto wait_for_ctlbuf;
 828
 829                 if (unlikely(!buffer_uptodate(bh)))
 830                         err = -EIO;
 831
 832                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 833                 clear_buffer_jwrite(bh);
 834                 jbd2_journal_unfile_buffer(journal, jh);
 835                 jbd2_journal_put_journal_head(jh);
 836                 __brelse(bh);           /* One for getblk */
 837                 /* AKPM: bforget here */
 838         }
 839
 840         if (err)
 841                 jbd2_journal_abort(journal, err);
 842
 843         jbd_debug(3, "JBD: commit phase 5\n");
 844
 845         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 846                                        JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 847                 err = journal_submit_commit_record(journal, commit_transaction,
 848                                                 &cbh, crc32_sum);
 849                 if (err)
 850                         __jbd2_journal_abort_hard(journal);
 851         }
 852         if (!err && !is_journal_aborted(journal))
 853                 err = journal_wait_on_commit_record(journal, cbh);
 854
 855         if (err)
 856                 jbd2_journal_abort(journal, err);
 857
 858         /* End of a transaction!  Finally, we can do checkpoint
 859            processing: any buffers committed as a result of this
 860            transaction can be removed from any checkpoint list it was on
 861            before. */
 862
 863         jbd_debug(3, "JBD: commit phase 6\n");
 864
 865         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 866         J_ASSERT(commit_transaction->t_buffers == NULL);
 867         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 868         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 869         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 870         J_ASSERT(commit_transaction->t_log_list == NULL);
 871
 872 restart_loop:
 873         /*
 874          * As there are other places (journal_unmap_buffer()) adding buffers
 875          * to this list we have to be careful and hold the j_list_lock.
 876          */
 877         spin_lock(&journal->j_list_lock);
 878         while (commit_transaction->t_forget) {
 879                 transaction_t *cp_transaction;
 880                 struct buffer_head *bh;
 881
 882                 jh = commit_transaction->t_forget;
 883                 spin_unlock(&journal->j_list_lock);
 884                 bh = jh2bh(jh);
 885                 jbd_lock_bh_state(bh);
 886                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 887                         jh->b_transaction == journal->j_running_transaction);
 888
 889                 /*
 890                  * If there is undo-protected committed data against
 891                  * this buffer, then we can remove it now.  If it is a
 892                  * buffer needing such protection, the old frozen_data
 893                  * field now points to a committed version of the
 894                  * buffer, so rotate that field to the new committed
 895                  * data.
 896                  *
 897                  * Otherwise, we can just throw away the frozen data now.
 898                  *
 899                  * We also know that the frozen data has already fired
 900                  * its triggers if they exist, so we can clear that too.
 901                  */
 902                 if (jh->b_committed_data) {
 903                         jbd2_free(jh->b_committed_data, bh->b_size);
 904                         jh->b_committed_data = NULL;
 905                         if (jh->b_frozen_data) {
 906                                 jh->b_committed_data = jh->b_frozen_data;
 907                                 jh->b_frozen_data = NULL;
 908                                 jh->b_frozen_triggers = NULL;
 909                         }
 910                 } else if (jh->b_frozen_data) {
 911                         jbd2_free(jh->b_frozen_data, bh->b_size);
 912                         jh->b_frozen_data = NULL;
 913                         jh->b_frozen_triggers = NULL;
 914                 }
 915
 916                 spin_lock(&journal->j_list_lock);
 917                 cp_transaction = jh->b_cp_transaction;
 918                 if (cp_transaction) {
 919                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 920                         cp_transaction->t_chp_stats.cs_dropped++;
 921                         __jbd2_journal_remove_checkpoint(jh);
 922                 }
 923
 924                 /* Only re-checkpoint the buffer_head if it is marked
 925                  * dirty.  If the buffer was added to the BJ_Forget list
 926                  * by jbd2_journal_forget, it may no longer be dirty and
 927                  * there's no point in keeping a checkpoint record for
 928                  * it. */
 929
 930                 /* A buffer which has been freed while still being
 931                  * journaled by a previous transaction may end up still
 932                  * being dirty here, but we want to avoid writing back
 933                  * that buffer in the future now that the last use has
 934                  * been committed.  That's not only a performance gain,
 935                  * it also stops aliasing problems if the buffer is left
 936                  * behind for writeback and gets reallocated for another
 937                  * use in a different page. */
 938                 if (buffer_freed(bh)) {
 939                         clear_buffer_freed(bh);
 940                         clear_buffer_jbddirty(bh);
 941                 }
 942
 943                 if (buffer_jbddirty(bh)) {
 944                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 945                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 946                         if (is_journal_aborted(journal))
 947                                 clear_buffer_jbddirty(bh);
 948                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 949                         __jbd2_journal_refile_buffer(jh);
 950                         jbd_unlock_bh_state(bh);
 951                 } else {
 952                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 953                         /* The buffer on BJ_Forget list and not jbddirty means
 954                          * it has been freed by this transaction and hence it
 955                          * could not have been reallocated until this
 956                          * transaction has committed. *BUT* it could be
 957                          * reallocated once we have written all the data to
 958                          * disk and before we process the buffer on BJ_Forget
 959                          * list. */
 960                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 961                         __jbd2_journal_refile_buffer(jh);
 962                         if (!jh->b_transaction) {
 963                                 jbd_unlock_bh_state(bh);
 964                                  /* needs a brelse */
 965                                 jbd2_journal_remove_journal_head(bh);
 966                                 release_buffer_page(bh);
 967                         } else
 968                                 jbd_unlock_bh_state(bh);
 969                 }
 970                 cond_resched_lock(&journal->j_list_lock);
 971         }
 972         spin_unlock(&journal->j_list_lock);
 973         /*
 974          * This is a bit sleazy.  We use j_list_lock to protect transition
 975          * of a transaction into T_FINISHED state and calling
 976          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 977          * other checkpointing code processing the transaction...
 978          */
 979         spin_lock(&journal->j_state_lock);
 980         spin_lock(&journal->j_list_lock);
 981         /*
 982          * Now recheck if some buffers did not get attached to the transaction
 983          * while the lock was dropped...
 984          */
 985         if (commit_transaction->t_forget) {
 986                 spin_unlock(&journal->j_list_lock);
 987                 spin_unlock(&journal->j_state_lock);
 988                 goto restart_loop;
 989         }
 990
 991         /* Done with this transaction! */
 992
 993         jbd_debug(3, "JBD: commit phase 7\n");
 994
 995         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 996
 997         commit_transaction->t_start = jiffies;
 998         stats.run.rs_logging = jbd2_time_diff(stats.run.rs_logging,
 999                                               commit_transaction->t_start);
1000
1001         /*
1002          * File the transaction statistics
1003          */
1004         stats.ts_tid = commit_transaction->t_tid;
1005         stats.run.rs_handle_count = commit_transaction->t_handle_count;
1006         trace_jbd2_run_stats(journal->j_fs_dev->bd_dev,
1007                              commit_transaction->t_tid, &stats.run);
1008
1009         /*
1010          * Calculate overall stats
1011          */
1012         spin_lock(&journal->j_history_lock);
1013         journal->j_stats.ts_tid++;
1014         journal->j_stats.run.rs_wait += stats.run.rs_wait;
1015         journal->j_stats.run.rs_running += stats.run.rs_running;
1016         journal->j_stats.run.rs_locked += stats.run.rs_locked;
1017         journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
1018         journal->j_stats.run.rs_logging += stats.run.rs_logging;
1019         journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
1020         journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
1021         journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
1022         spin_unlock(&journal->j_history_lock);
1023
1024         commit_transaction->t_state = T_FINISHED;
1025         J_ASSERT(commit_transaction == journal->j_committing_transaction);
1026         journal->j_commit_sequence = commit_transaction->t_tid;
1027         journal->j_committing_transaction = NULL;
1028         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1029
1030         /*
1031          * weight the commit time higher than the average time so we don't
1032          * react too strongly to vast changes in the commit time
1033          */
1034         if (likely(journal->j_average_commit_time))
1035                 journal->j_average_commit_time = (commit_time +
1036                                 journal->j_average_commit_time*3) / 4;
1037         else
1038                 journal->j_average_commit_time = commit_time;
1039         spin_unlock(&journal->j_state_lock);
1040
1041         if (commit_transaction->t_checkpoint_list == NULL &&
1042             commit_transaction->t_checkpoint_io_list == NULL) {
1043                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1044                 to_free = 1;
1045         } else {
1046                 if (journal->j_checkpoint_transactions == NULL) {
1047                         journal->j_checkpoint_transactions = commit_transaction;
1048                         commit_transaction->t_cpnext = commit_transaction;
1049                         commit_transaction->t_cpprev = commit_transaction;
1050                 } else {
1051                         commit_transaction->t_cpnext =
1052                                 journal->j_checkpoint_transactions;
1053                         commit_transaction->t_cpprev =
1054                                 commit_transaction->t_cpnext->t_cpprev;
1055                         commit_transaction->t_cpnext->t_cpprev =
1056                                 commit_transaction;
1057                         commit_transaction->t_cpprev->t_cpnext =
1058                                 commit_transaction;
1059                 }
1060         }
1061         spin_unlock(&journal->j_list_lock);
1062
1063         if (journal->j_commit_callback)
1064                 journal->j_commit_callback(journal, commit_transaction);
1065
1066         trace_jbd2_end_commit(journal, commit_transaction);
1067         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1068                   journal->j_commit_sequence, journal->j_tail_sequence);
1069         if (to_free)
1070                 kfree(commit_transaction);
1071
1072         wake_up(&journal->j_wait_done_commit);
1073 }