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 <trace/events/jbd2.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_PLUG, 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_PLUG, 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_PLUG, 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                 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                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 263                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 264         }
 265         spin_unlock(&journal->j_list_lock);
 266         return ret;
 267 }
 268
 269 /*
 270  * Wait for data submitted for writeout, refile inodes to proper
 271  * transaction if needed.
 272  *
 273  */
 274 static int journal_finish_inode_data_buffers(journal_t *journal,
 275                 transaction_t *commit_transaction)
 276 {
 277         struct jbd2_inode *jinode, *next_i;
 278         int err, ret = 0;
 279
 280         /* For locking, see the comment in journal_submit_data_buffers() */
 281         spin_lock(&journal->j_list_lock);
 282         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 283                 jinode->i_flags |= JI_COMMIT_RUNNING;
 284                 spin_unlock(&journal->j_list_lock);
 285                 err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
 286                 if (err) {
 287                         /*
 288                          * Because AS_EIO is cleared by
 289                          * wait_on_page_writeback_range(), set it again so
 290                          * that user process can get -EIO from fsync().
 291                          */
 292                         set_bit(AS_EIO,
 293                                 &jinode->i_vfs_inode->i_mapping->flags);
 294
 295                         if (!ret)
 296                                 ret = err;
 297                 }
 298                 spin_lock(&journal->j_list_lock);
 299                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 300                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 301         }
 302
 303         /* Now refile inode to proper lists */
 304         list_for_each_entry_safe(jinode, next_i,
 305                                  &commit_transaction->t_inode_list, i_list) {
 306                 list_del(&jinode->i_list);
 307                 if (jinode->i_next_transaction) {
 308                         jinode->i_transaction = jinode->i_next_transaction;
 309                         jinode->i_next_transaction = NULL;
 310                         list_add(&jinode->i_list,
 311                                 &jinode->i_transaction->t_inode_list);
 312                 } else {
 313                         jinode->i_transaction = NULL;
 314                 }
 315         }
 316         spin_unlock(&journal->j_list_lock);
 317
 318         return ret;
 319 }
 320
 321 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 322 {
 323         struct page *page = bh->b_page;
 324         char *addr;
 325         __u32 checksum;
 326
 327         addr = kmap_atomic(page, KM_USER0);
 328         checksum = crc32_be(crc32_sum,
 329                 (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
 330         kunmap_atomic(addr, KM_USER0);
 331
 332         return checksum;
 333 }
 334
 335 static void write_tag_block(int tag_bytes, journal_block_tag_t *tag,
 336                                    unsigned long long block)
 337 {
 338         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
 339         if (tag_bytes > JBD2_TAG_SIZE32)
 340                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
 341 }
 342
 343 /*
 344  * jbd2_journal_commit_transaction
 345  *
 346  * The primary function for committing a transaction to the log.  This
 347  * function is called by the journal thread to begin a complete commit.
 348  */
 349 void jbd2_journal_commit_transaction(journal_t *journal)
 350 {
 351         struct transaction_stats_s stats;
 352         transaction_t *commit_transaction;
 353         struct journal_head *jh, *new_jh, *descriptor;
 354         struct buffer_head **wbuf = journal->j_wbuf;
 355         int bufs;
 356         int flags;
 357         int err;
 358         unsigned long long blocknr;
 359         ktime_t start_time;
 360         u64 commit_time;
 361         char *tagp = NULL;
 362         journal_header_t *header;
 363         journal_block_tag_t *tag = NULL;
 364         int space_left = 0;
 365         int first_tag = 0;
 366         int tag_flag;
 367         int i, to_free = 0;
 368         int tag_bytes = journal_tag_bytes(journal);
 369         struct buffer_head *cbh = NULL; /* For transactional checksums */
 370         __u32 crc32_sum = ~0;
 371         int write_op = WRITE;
 372
 373         /*
 374          * First job: lock down the current transaction and wait for
 375          * all outstanding updates to complete.
 376          */
 377
 378 #ifdef COMMIT_STATS
 379         spin_lock(&journal->j_list_lock);
 380         summarise_journal_usage(journal);
 381         spin_unlock(&journal->j_list_lock);
 382 #endif
 383
 384         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 385         if (journal->j_flags & JBD2_FLUSHED) {
 386                 jbd_debug(3, "super block updated\n");
 387                 jbd2_journal_update_superblock(journal, 1);
 388         } else {
 389                 jbd_debug(3, "superblock not updated\n");
 390         }
 391
 392         J_ASSERT(journal->j_running_transaction != NULL);
 393         J_ASSERT(journal->j_committing_transaction == NULL);
 394
 395         commit_transaction = journal->j_running_transaction;
 396         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 397
 398         trace_jbd2_start_commit(journal, commit_transaction);
 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         /*
 406          * Use plugged writes here, since we want to submit several before
 407          * we unplug the device. We don't do explicit unplugging in here,
 408          * instead we rely on sync_buffer() doing the unplug for us.
 409          */
 410         if (commit_transaction->t_synchronous_commit)
 411                 write_op = WRITE_SYNC_PLUG;
 412         trace_jbd2_commit_locking(journal, commit_transaction);
 413         stats.u.run.rs_wait = commit_transaction->t_max_wait;
 414         stats.u.run.rs_locked = jiffies;
 415         stats.u.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 416                                                 stats.u.run.rs_locked);
 417
 418         spin_lock(&commit_transaction->t_handle_lock);
 419         while (commit_transaction->t_updates) {
 420                 DEFINE_WAIT(wait);
 421
 422                 prepare_to_wait(&journal->j_wait_updates, &wait,
 423                                         TASK_UNINTERRUPTIBLE);
 424                 if (commit_transaction->t_updates) {
 425                         spin_unlock(&commit_transaction->t_handle_lock);
 426                         spin_unlock(&journal->j_state_lock);
 427                         schedule();
 428                         spin_lock(&journal->j_state_lock);
 429                         spin_lock(&commit_transaction->t_handle_lock);
 430                 }
 431                 finish_wait(&journal->j_wait_updates, &wait);
 432         }
 433         spin_unlock(&commit_transaction->t_handle_lock);
 434
 435         J_ASSERT (commit_transaction->t_outstanding_credits <=
 436                         journal->j_max_transaction_buffers);
 437
 438         /*
 439          * First thing we are allowed to do is to discard any remaining
 440          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 441          * that there are no such buffers: if a large filesystem
 442          * operation like a truncate needs to split itself over multiple
 443          * transactions, then it may try to do a jbd2_journal_restart() while
 444          * there are still BJ_Reserved buffers outstanding.  These must
 445          * be released cleanly from the current transaction.
 446          *
 447          * In this case, the filesystem must still reserve write access
 448          * again before modifying the buffer in the new transaction, but
 449          * we do not require it to remember exactly which old buffers it
 450          * has reserved.  This is consistent with the existing behaviour
 451          * that multiple jbd2_journal_get_write_access() calls to the same
 452          * buffer are perfectly permissable.
 453          */
 454         while (commit_transaction->t_reserved_list) {
 455                 jh = commit_transaction->t_reserved_list;
 456                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 457                 /*
 458                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 459                  * leave undo-committed data.
 460                  */
 461                 if (jh->b_committed_data) {
 462                         struct buffer_head *bh = jh2bh(jh);
 463
 464                         jbd_lock_bh_state(bh);
 465                         jbd2_free(jh->b_committed_data, bh->b_size);
 466                         jh->b_committed_data = NULL;
 467                         jbd_unlock_bh_state(bh);
 468                 }
 469                 jbd2_journal_refile_buffer(journal, jh);
 470         }
 471
 472         /*
 473          * Now try to drop any written-back buffers from the journal's
 474          * checkpoint lists.  We do this *before* commit because it potentially
 475          * frees some memory
 476          */
 477         spin_lock(&journal->j_list_lock);
 478         __jbd2_journal_clean_checkpoint_list(journal);
 479         spin_unlock(&journal->j_list_lock);
 480
 481         jbd_debug (3, "JBD: commit phase 1\n");
 482
 483         /*
 484          * Switch to a new revoke table.
 485          */
 486         jbd2_journal_switch_revoke_table(journal);
 487
 488         trace_jbd2_commit_flushing(journal, commit_transaction);
 489         stats.u.run.rs_flushing = jiffies;
 490         stats.u.run.rs_locked = jbd2_time_diff(stats.u.run.rs_locked,
 491                                                stats.u.run.rs_flushing);
 492
 493         commit_transaction->t_state = T_FLUSH;
 494         journal->j_committing_transaction = commit_transaction;
 495         journal->j_running_transaction = NULL;
 496         start_time = ktime_get();
 497         commit_transaction->t_log_start = journal->j_head;
 498         wake_up(&journal->j_wait_transaction_locked);
 499         spin_unlock(&journal->j_state_lock);
 500
 501         jbd_debug (3, "JBD: commit phase 2\n");
 502
 503         /*
 504          * Now start flushing things to disk, in the order they appear
 505          * on the transaction lists.  Data blocks go first.
 506          */
 507         err = journal_submit_data_buffers(journal, commit_transaction);
 508         if (err)
 509                 jbd2_journal_abort(journal, err);
 510
 511         jbd2_journal_write_revoke_records(journal, commit_transaction,
 512                                           write_op);
 513
 514         jbd_debug(3, "JBD: commit phase 2\n");
 515
 516         /*
 517          * Way to go: we have now written out all of the data for a
 518          * transaction!  Now comes the tricky part: we need to write out
 519          * metadata.  Loop over the transaction's entire buffer list:
 520          */
 521         spin_lock(&journal->j_state_lock);
 522         commit_transaction->t_state = T_COMMIT;
 523         spin_unlock(&journal->j_state_lock);
 524
 525         trace_jbd2_commit_logging(journal, commit_transaction);
 526         stats.u.run.rs_logging = jiffies;
 527         stats.u.run.rs_flushing = jbd2_time_diff(stats.u.run.rs_flushing,
 528                                                  stats.u.run.rs_logging);
 529         stats.u.run.rs_blocks = commit_transaction->t_outstanding_credits;
 530         stats.u.run.rs_blocks_logged = 0;
 531
 532         J_ASSERT(commit_transaction->t_nr_buffers <=
 533                  commit_transaction->t_outstanding_credits);
 534
 535         err = 0;
 536         descriptor = NULL;
 537         bufs = 0;
 538         while (commit_transaction->t_buffers) {
 539
 540                 /* Find the next buffer to be journaled... */
 541
 542                 jh = commit_transaction->t_buffers;
 543
 544                 /* If we're in abort mode, we just un-journal the buffer and
 545                    release it. */
 546
 547                 if (is_journal_aborted(journal)) {
 548                         clear_buffer_jbddirty(jh2bh(jh));
 549                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 550                         jbd2_buffer_abort_trigger(jh,
 551                                                   jh->b_frozen_data ?
 552                                                   jh->b_frozen_triggers :
 553                                                   jh->b_triggers);
 554                         jbd2_journal_refile_buffer(journal, jh);
 555                         /* If that was the last one, we need to clean up
 556                          * any descriptor buffers which may have been
 557                          * already allocated, even if we are now
 558                          * aborting. */
 559                         if (!commit_transaction->t_buffers)
 560                                 goto start_journal_io;
 561                         continue;
 562                 }
 563
 564                 /* Make sure we have a descriptor block in which to
 565                    record the metadata buffer. */
 566
 567                 if (!descriptor) {
 568                         struct buffer_head *bh;
 569
 570                         J_ASSERT (bufs == 0);
 571
 572                         jbd_debug(4, "JBD: get descriptor\n");
 573
 574                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 575                         if (!descriptor) {
 576                                 jbd2_journal_abort(journal, -EIO);
 577                                 continue;
 578                         }
 579
 580                         bh = jh2bh(descriptor);
 581                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 582                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 583                         header = (journal_header_t *)&bh->b_data[0];
 584                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 585                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 586                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 587
 588                         tagp = &bh->b_data[sizeof(journal_header_t)];
 589                         space_left = bh->b_size - sizeof(journal_header_t);
 590                         first_tag = 1;
 591                         set_buffer_jwrite(bh);
 592                         set_buffer_dirty(bh);
 593                         wbuf[bufs++] = bh;
 594
 595                         /* Record it so that we can wait for IO
 596                            completion later */
 597                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 598                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 599                                         BJ_LogCtl);
 600                 }
 601
 602                 /* Where is the buffer to be written? */
 603
 604                 err = jbd2_journal_next_log_block(journal, &blocknr);
 605                 /* If the block mapping failed, just abandon the buffer
 606                    and repeat this loop: we'll fall into the
 607                    refile-on-abort condition above. */
 608                 if (err) {
 609                         jbd2_journal_abort(journal, err);
 610                         continue;
 611                 }
 612
 613                 /*
 614                  * start_this_handle() uses t_outstanding_credits to determine
 615                  * the free space in the log, but this counter is changed
 616                  * by jbd2_journal_next_log_block() also.
 617                  */
 618                 commit_transaction->t_outstanding_credits--;
 619
 620                 /* Bump b_count to prevent truncate from stumbling over
 621                    the shadowed buffer!  @@@ This can go if we ever get
 622                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 623                 atomic_inc(&jh2bh(jh)->b_count);
 624
 625                 /* Make a temporary IO buffer with which to write it out
 626                    (this will requeue both the metadata buffer and the
 627                    temporary IO buffer). new_bh goes on BJ_IO*/
 628
 629                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 630                 /*
 631                  * akpm: jbd2_journal_write_metadata_buffer() sets
 632                  * new_bh->b_transaction to commit_transaction.
 633                  * We need to clean this up before we release new_bh
 634                  * (which is of type BJ_IO)
 635                  */
 636                 JBUFFER_TRACE(jh, "ph3: write metadata");
 637                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 638                                                       jh, &new_jh, blocknr);
 639                 if (flags < 0) {
 640                         jbd2_journal_abort(journal, flags);
 641                         continue;
 642                 }
 643                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 644                 wbuf[bufs++] = jh2bh(new_jh);
 645
 646                 /* Record the new block's tag in the current descriptor
 647                    buffer */
 648
 649                 tag_flag = 0;
 650                 if (flags & 1)
 651                         tag_flag |= JBD2_FLAG_ESCAPE;
 652                 if (!first_tag)
 653                         tag_flag |= JBD2_FLAG_SAME_UUID;
 654
 655                 tag = (journal_block_tag_t *) tagp;
 656                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 657                 tag->t_flags = cpu_to_be32(tag_flag);
 658                 tagp += tag_bytes;
 659                 space_left -= tag_bytes;
 660
 661                 if (first_tag) {
 662                         memcpy (tagp, journal->j_uuid, 16);
 663                         tagp += 16;
 664                         space_left -= 16;
 665                         first_tag = 0;
 666                 }
 667
 668                 /* If there's no more to do, or if the descriptor is full,
 669                    let the IO rip! */
 670
 671                 if (bufs == journal->j_wbufsize ||
 672                     commit_transaction->t_buffers == NULL ||
 673                     space_left < tag_bytes + 16) {
 674
 675                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 676
 677                         /* Write an end-of-descriptor marker before
 678                            submitting the IOs.  "tag" still points to
 679                            the last tag we set up. */
 680
 681                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 682
 683 start_journal_io:
 684                         for (i = 0; i < bufs; i++) {
 685                                 struct buffer_head *bh = wbuf[i];
 686                                 /*
 687                                  * Compute checksum.
 688                                  */
 689                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 690                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 691                                         crc32_sum =
 692                                             jbd2_checksum_data(crc32_sum, bh);
 693                                 }
 694
 695                                 lock_buffer(bh);
 696                                 clear_buffer_dirty(bh);
 697                                 set_buffer_uptodate(bh);
 698                                 bh->b_end_io = journal_end_buffer_io_sync;
 699                                 submit_bh(write_op, bh);
 700                         }
 701                         cond_resched();
 702                         stats.u.run.rs_blocks_logged += bufs;
 703
 704                         /* Force a new descriptor to be generated next
 705                            time round the loop. */
 706                         descriptor = NULL;
 707                         bufs = 0;
 708                 }
 709         }
 710
 711         /* Done it all: now write the commit record asynchronously. */
 712
 713         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 714                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 715                 err = journal_submit_commit_record(journal, commit_transaction,
 716                                                  &cbh, crc32_sum);
 717                 if (err)
 718                         __jbd2_journal_abort_hard(journal);
 719         }
 720
 721         /*
 722          * This is the right place to wait for data buffers both for ASYNC
 723          * and !ASYNC commit. If commit is ASYNC, we need to wait only after
 724          * the commit block went to disk (which happens above). If commit is
 725          * SYNC, we need to wait for data buffers before we start writing
 726          * commit block, which happens below in such setting.
 727          */
 728         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 729         if (err) {
 730                 printk(KERN_WARNING
 731                         "JBD2: Detected IO errors while flushing file data "
 732                        "on %s\n", journal->j_devname);
 733                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 734                         jbd2_journal_abort(journal, err);
 735                 err = 0;
 736         }
 737
 738         /* Lo and behold: we have just managed to send a transaction to
 739            the log.  Before we can commit it, wait for the IO so far to
 740            complete.  Control buffers being written are on the
 741            transaction's t_log_list queue, and metadata buffers are on
 742            the t_iobuf_list queue.
 743
 744            Wait for the buffers in reverse order.  That way we are
 745            less likely to be woken up until all IOs have completed, and
 746            so we incur less scheduling load.
 747         */
 748
 749         jbd_debug(3, "JBD: commit phase 3\n");
 750
 751         /*
 752          * akpm: these are BJ_IO, and j_list_lock is not needed.
 753          * See __journal_try_to_free_buffer.
 754          */
 755 wait_for_iobuf:
 756         while (commit_transaction->t_iobuf_list != NULL) {
 757                 struct buffer_head *bh;
 758
 759                 jh = commit_transaction->t_iobuf_list->b_tprev;
 760                 bh = jh2bh(jh);
 761                 if (buffer_locked(bh)) {
 762                         wait_on_buffer(bh);
 763                         goto wait_for_iobuf;
 764                 }
 765                 if (cond_resched())
 766                         goto wait_for_iobuf;
 767
 768                 if (unlikely(!buffer_uptodate(bh)))
 769                         err = -EIO;
 770
 771                 clear_buffer_jwrite(bh);
 772
 773                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 774                 jbd2_journal_unfile_buffer(journal, jh);
 775
 776                 /*
 777                  * ->t_iobuf_list should contain only dummy buffer_heads
 778                  * which were created by jbd2_journal_write_metadata_buffer().
 779                  */
 780                 BUFFER_TRACE(bh, "dumping temporary bh");
 781                 jbd2_journal_put_journal_head(jh);
 782                 __brelse(bh);
 783                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 784                 free_buffer_head(bh);
 785
 786                 /* We also have to unlock and free the corresponding
 787                    shadowed buffer */
 788                 jh = commit_transaction->t_shadow_list->b_tprev;
 789                 bh = jh2bh(jh);
 790                 clear_bit(BH_JWrite, &bh->b_state);
 791                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 792
 793                 /* The metadata is now released for reuse, but we need
 794                    to remember it against this transaction so that when
 795                    we finally commit, we can do any checkpointing
 796                    required. */
 797                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 798                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 799                 /* Wake up any transactions which were waiting for this
 800                    IO to complete */
 801                 wake_up_bit(&bh->b_state, BH_Unshadow);
 802                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 803                 __brelse(bh);
 804         }
 805
 806         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 807
 808         jbd_debug(3, "JBD: commit phase 4\n");
 809
 810         /* Here we wait for the revoke record and descriptor record buffers */
 811  wait_for_ctlbuf:
 812         while (commit_transaction->t_log_list != NULL) {
 813                 struct buffer_head *bh;
 814
 815                 jh = commit_transaction->t_log_list->b_tprev;
 816                 bh = jh2bh(jh);
 817                 if (buffer_locked(bh)) {
 818                         wait_on_buffer(bh);
 819                         goto wait_for_ctlbuf;
 820                 }
 821                 if (cond_resched())
 822                         goto wait_for_ctlbuf;
 823
 824                 if (unlikely(!buffer_uptodate(bh)))
 825                         err = -EIO;
 826
 827                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 828                 clear_buffer_jwrite(bh);
 829                 jbd2_journal_unfile_buffer(journal, jh);
 830                 jbd2_journal_put_journal_head(jh);
 831                 __brelse(bh);           /* One for getblk */
 832                 /* AKPM: bforget here */
 833         }
 834
 835         if (err)
 836                 jbd2_journal_abort(journal, err);
 837
 838         jbd_debug(3, "JBD: commit phase 5\n");
 839
 840         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 841                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 842                 err = journal_submit_commit_record(journal, commit_transaction,
 843                                                 &cbh, crc32_sum);
 844                 if (err)
 845                         __jbd2_journal_abort_hard(journal);
 846         }
 847         if (!err && !is_journal_aborted(journal))
 848                 err = journal_wait_on_commit_record(journal, cbh);
 849
 850         if (err)
 851                 jbd2_journal_abort(journal, err);
 852
 853         /* End of a transaction!  Finally, we can do checkpoint
 854            processing: any buffers committed as a result of this
 855            transaction can be removed from any checkpoint list it was on
 856            before. */
 857
 858         jbd_debug(3, "JBD: commit phase 6\n");
 859
 860         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 861         J_ASSERT(commit_transaction->t_buffers == NULL);
 862         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 863         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 864         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 865         J_ASSERT(commit_transaction->t_log_list == NULL);
 866
 867 restart_loop:
 868         /*
 869          * As there are other places (journal_unmap_buffer()) adding buffers
 870          * to this list we have to be careful and hold the j_list_lock.
 871          */
 872         spin_lock(&journal->j_list_lock);
 873         while (commit_transaction->t_forget) {
 874                 transaction_t *cp_transaction;
 875                 struct buffer_head *bh;
 876
 877                 jh = commit_transaction->t_forget;
 878                 spin_unlock(&journal->j_list_lock);
 879                 bh = jh2bh(jh);
 880                 jbd_lock_bh_state(bh);
 881                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 882                         jh->b_transaction == journal->j_running_transaction);
 883
 884                 /*
 885                  * If there is undo-protected committed data against
 886                  * this buffer, then we can remove it now.  If it is a
 887                  * buffer needing such protection, the old frozen_data
 888                  * field now points to a committed version of the
 889                  * buffer, so rotate that field to the new committed
 890                  * data.
 891                  *
 892                  * Otherwise, we can just throw away the frozen data now.
 893                  *
 894                  * We also know that the frozen data has already fired
 895                  * its triggers if they exist, so we can clear that too.
 896                  */
 897                 if (jh->b_committed_data) {
 898                         jbd2_free(jh->b_committed_data, bh->b_size);
 899                         jh->b_committed_data = NULL;
 900                         if (jh->b_frozen_data) {
 901                                 jh->b_committed_data = jh->b_frozen_data;
 902                                 jh->b_frozen_data = NULL;
 903                                 jh->b_frozen_triggers = NULL;
 904                         }
 905                 } else if (jh->b_frozen_data) {
 906                         jbd2_free(jh->b_frozen_data, bh->b_size);
 907                         jh->b_frozen_data = NULL;
 908                         jh->b_frozen_triggers = NULL;
 909                 }
 910
 911                 spin_lock(&journal->j_list_lock);
 912                 cp_transaction = jh->b_cp_transaction;
 913                 if (cp_transaction) {
 914                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 915                         cp_transaction->t_chp_stats.cs_dropped++;
 916                         __jbd2_journal_remove_checkpoint(jh);
 917                 }
 918
 919                 /* Only re-checkpoint the buffer_head if it is marked
 920                  * dirty.  If the buffer was added to the BJ_Forget list
 921                  * by jbd2_journal_forget, it may no longer be dirty and
 922                  * there's no point in keeping a checkpoint record for
 923                  * it. */
 924
 925                 /* A buffer which has been freed while still being
 926                  * journaled by a previous transaction may end up still
 927                  * being dirty here, but we want to avoid writing back
 928                  * that buffer in the future now that the last use has
 929                  * been committed.  That's not only a performance gain,
 930                  * it also stops aliasing problems if the buffer is left
 931                  * behind for writeback and gets reallocated for another
 932                  * use in a different page. */
 933                 if (buffer_freed(bh)) {
 934                         clear_buffer_freed(bh);
 935                         clear_buffer_jbddirty(bh);
 936                 }
 937
 938                 if (buffer_jbddirty(bh)) {
 939                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 940                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 941                         if (is_journal_aborted(journal))
 942                                 clear_buffer_jbddirty(bh);
 943                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 944                         __jbd2_journal_refile_buffer(jh);
 945                         jbd_unlock_bh_state(bh);
 946                 } else {
 947                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 948                         /* The buffer on BJ_Forget list and not jbddirty means
 949                          * it has been freed by this transaction and hence it
 950                          * could not have been reallocated until this
 951                          * transaction has committed. *BUT* it could be
 952                          * reallocated once we have written all the data to
 953                          * disk and before we process the buffer on BJ_Forget
 954                          * list. */
 955                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 956                         __jbd2_journal_refile_buffer(jh);
 957                         if (!jh->b_transaction) {
 958                                 jbd_unlock_bh_state(bh);
 959                                  /* needs a brelse */
 960                                 jbd2_journal_remove_journal_head(bh);
 961                                 release_buffer_page(bh);
 962                         } else
 963                                 jbd_unlock_bh_state(bh);
 964                 }
 965                 cond_resched_lock(&journal->j_list_lock);
 966         }
 967         spin_unlock(&journal->j_list_lock);
 968         /*
 969          * This is a bit sleazy.  We use j_list_lock to protect transition
 970          * of a transaction into T_FINISHED state and calling
 971          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 972          * other checkpointing code processing the transaction...
 973          */
 974         spin_lock(&journal->j_state_lock);
 975         spin_lock(&journal->j_list_lock);
 976         /*
 977          * Now recheck if some buffers did not get attached to the transaction
 978          * while the lock was dropped...
 979          */
 980         if (commit_transaction->t_forget) {
 981                 spin_unlock(&journal->j_list_lock);
 982                 spin_unlock(&journal->j_state_lock);
 983                 goto restart_loop;
 984         }
 985
 986         /* Done with this transaction! */
 987
 988         jbd_debug(3, "JBD: commit phase 7\n");
 989
 990         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 991
 992         commit_transaction->t_start = jiffies;
 993         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
 994                                                 commit_transaction->t_start);
 995
 996         /*
 997          * File the transaction for history
 998          */
 999         stats.ts_type = JBD2_STATS_RUN;
1000         stats.ts_tid = commit_transaction->t_tid;
1001         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
1002         spin_lock(&journal->j_history_lock);
1003         memcpy(journal->j_history + journal->j_history_cur, &stats,
1004                         sizeof(stats));
1005         if (++journal->j_history_cur == journal->j_history_max)
1006                 journal->j_history_cur = 0;
1007
1008         /*
1009          * Calculate overall stats
1010          */
1011         journal->j_stats.ts_tid++;
1012         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
1013         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
1014         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
1015         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
1016         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
1017         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
1018         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
1019         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
1020         spin_unlock(&journal->j_history_lock);
1021
1022         commit_transaction->t_state = T_FINISHED;
1023         J_ASSERT(commit_transaction == journal->j_committing_transaction);
1024         journal->j_commit_sequence = commit_transaction->t_tid;
1025         journal->j_committing_transaction = NULL;
1026         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1027
1028         /*
1029          * weight the commit time higher than the average time so we don't
1030          * react too strongly to vast changes in the commit time
1031          */
1032         if (likely(journal->j_average_commit_time))
1033                 journal->j_average_commit_time = (commit_time +
1034                                 journal->j_average_commit_time*3) / 4;
1035         else
1036                 journal->j_average_commit_time = commit_time;
1037         spin_unlock(&journal->j_state_lock);
1038
1039         if (commit_transaction->t_checkpoint_list == NULL &&
1040             commit_transaction->t_checkpoint_io_list == NULL) {
1041                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1042                 to_free = 1;
1043         } else {
1044                 if (journal->j_checkpoint_transactions == NULL) {
1045                         journal->j_checkpoint_transactions = commit_transaction;
1046                         commit_transaction->t_cpnext = commit_transaction;
1047                         commit_transaction->t_cpprev = commit_transaction;
1048                 } else {
1049                         commit_transaction->t_cpnext =
1050                                 journal->j_checkpoint_transactions;
1051                         commit_transaction->t_cpprev =
1052                                 commit_transaction->t_cpnext->t_cpprev;
1053                         commit_transaction->t_cpnext->t_cpprev =
1054                                 commit_transaction;
1055                         commit_transaction->t_cpprev->t_cpnext =
1056                                 commit_transaction;
1057                 }
1058         }
1059         spin_unlock(&journal->j_list_lock);
1060
1061         if (journal->j_commit_callback)
1062                 journal->j_commit_callback(journal, commit_transaction);
1063
1064         trace_jbd2_end_commit(journal, commit_transaction);
1065         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1066                   journal->j_commit_sequence, journal->j_tail_sequence);
1067         if (to_free)
1068                 kfree(commit_transaction);
1069
1070         wake_up(&journal->j_wait_done_commit);
1071 }