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                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 640                 wbuf[bufs++] = jh2bh(new_jh);
 641
 642                 /* Record the new block's tag in the current descriptor
 643                    buffer */
 644
 645                 tag_flag = 0;
 646                 if (flags & 1)
 647                         tag_flag |= JBD2_FLAG_ESCAPE;
 648                 if (!first_tag)
 649                         tag_flag |= JBD2_FLAG_SAME_UUID;
 650
 651                 tag = (journal_block_tag_t *) tagp;
 652                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 653                 tag->t_flags = cpu_to_be32(tag_flag);
 654                 tagp += tag_bytes;
 655                 space_left -= tag_bytes;
 656
 657                 if (first_tag) {
 658                         memcpy (tagp, journal->j_uuid, 16);
 659                         tagp += 16;
 660                         space_left -= 16;
 661                         first_tag = 0;
 662                 }
 663
 664                 /* If there's no more to do, or if the descriptor is full,
 665                    let the IO rip! */
 666
 667                 if (bufs == journal->j_wbufsize ||
 668                     commit_transaction->t_buffers == NULL ||
 669                     space_left < tag_bytes + 16) {
 670
 671                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 672
 673                         /* Write an end-of-descriptor marker before
 674                            submitting the IOs.  "tag" still points to
 675                            the last tag we set up. */
 676
 677                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 678
 679 start_journal_io:
 680                         for (i = 0; i < bufs; i++) {
 681                                 struct buffer_head *bh = wbuf[i];
 682                                 /*
 683                                  * Compute checksum.
 684                                  */
 685                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 686                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 687                                         crc32_sum =
 688                                             jbd2_checksum_data(crc32_sum, bh);
 689                                 }
 690
 691                                 lock_buffer(bh);
 692                                 clear_buffer_dirty(bh);
 693                                 set_buffer_uptodate(bh);
 694                                 bh->b_end_io = journal_end_buffer_io_sync;
 695                                 submit_bh(write_op, bh);
 696                         }
 697                         cond_resched();
 698                         stats.u.run.rs_blocks_logged += bufs;
 699
 700                         /* Force a new descriptor to be generated next
 701                            time round the loop. */
 702                         descriptor = NULL;
 703                         bufs = 0;
 704                 }
 705         }
 706
 707         /* Done it all: now write the commit record asynchronously. */
 708
 709         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 710                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 711                 err = journal_submit_commit_record(journal, commit_transaction,
 712                                                  &cbh, crc32_sum);
 713                 if (err)
 714                         __jbd2_journal_abort_hard(journal);
 715         }
 716
 717         /*
 718          * This is the right place to wait for data buffers both for ASYNC
 719          * and !ASYNC commit. If commit is ASYNC, we need to wait only after
 720          * the commit block went to disk (which happens above). If commit is
 721          * SYNC, we need to wait for data buffers before we start writing
 722          * commit block, which happens below in such setting.
 723          */
 724         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 725         if (err) {
 726                 printk(KERN_WARNING
 727                         "JBD2: Detected IO errors while flushing file data "
 728                        "on %s\n", journal->j_devname);
 729                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 730                         jbd2_journal_abort(journal, err);
 731                 err = 0;
 732         }
 733
 734         /* Lo and behold: we have just managed to send a transaction to
 735            the log.  Before we can commit it, wait for the IO so far to
 736            complete.  Control buffers being written are on the
 737            transaction's t_log_list queue, and metadata buffers are on
 738            the t_iobuf_list queue.
 739
 740            Wait for the buffers in reverse order.  That way we are
 741            less likely to be woken up until all IOs have completed, and
 742            so we incur less scheduling load.
 743         */
 744
 745         jbd_debug(3, "JBD: commit phase 3\n");
 746
 747         /*
 748          * akpm: these are BJ_IO, and j_list_lock is not needed.
 749          * See __journal_try_to_free_buffer.
 750          */
 751 wait_for_iobuf:
 752         while (commit_transaction->t_iobuf_list != NULL) {
 753                 struct buffer_head *bh;
 754
 755                 jh = commit_transaction->t_iobuf_list->b_tprev;
 756                 bh = jh2bh(jh);
 757                 if (buffer_locked(bh)) {
 758                         wait_on_buffer(bh);
 759                         goto wait_for_iobuf;
 760                 }
 761                 if (cond_resched())
 762                         goto wait_for_iobuf;
 763
 764                 if (unlikely(!buffer_uptodate(bh)))
 765                         err = -EIO;
 766
 767                 clear_buffer_jwrite(bh);
 768
 769                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 770                 jbd2_journal_unfile_buffer(journal, jh);
 771
 772                 /*
 773                  * ->t_iobuf_list should contain only dummy buffer_heads
 774                  * which were created by jbd2_journal_write_metadata_buffer().
 775                  */
 776                 BUFFER_TRACE(bh, "dumping temporary bh");
 777                 jbd2_journal_put_journal_head(jh);
 778                 __brelse(bh);
 779                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 780                 free_buffer_head(bh);
 781
 782                 /* We also have to unlock and free the corresponding
 783                    shadowed buffer */
 784                 jh = commit_transaction->t_shadow_list->b_tprev;
 785                 bh = jh2bh(jh);
 786                 clear_bit(BH_JWrite, &bh->b_state);
 787                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 788
 789                 /* The metadata is now released for reuse, but we need
 790                    to remember it against this transaction so that when
 791                    we finally commit, we can do any checkpointing
 792                    required. */
 793                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 794                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 795                 /* Wake up any transactions which were waiting for this
 796                    IO to complete */
 797                 wake_up_bit(&bh->b_state, BH_Unshadow);
 798                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 799                 __brelse(bh);
 800         }
 801
 802         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 803
 804         jbd_debug(3, "JBD: commit phase 4\n");
 805
 806         /* Here we wait for the revoke record and descriptor record buffers */
 807  wait_for_ctlbuf:
 808         while (commit_transaction->t_log_list != NULL) {
 809                 struct buffer_head *bh;
 810
 811                 jh = commit_transaction->t_log_list->b_tprev;
 812                 bh = jh2bh(jh);
 813                 if (buffer_locked(bh)) {
 814                         wait_on_buffer(bh);
 815                         goto wait_for_ctlbuf;
 816                 }
 817                 if (cond_resched())
 818                         goto wait_for_ctlbuf;
 819
 820                 if (unlikely(!buffer_uptodate(bh)))
 821                         err = -EIO;
 822
 823                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 824                 clear_buffer_jwrite(bh);
 825                 jbd2_journal_unfile_buffer(journal, jh);
 826                 jbd2_journal_put_journal_head(jh);
 827                 __brelse(bh);           /* One for getblk */
 828                 /* AKPM: bforget here */
 829         }
 830
 831         if (err)
 832                 jbd2_journal_abort(journal, err);
 833
 834         jbd_debug(3, "JBD: commit phase 5\n");
 835
 836         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 837                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 838                 err = journal_submit_commit_record(journal, commit_transaction,
 839                                                 &cbh, crc32_sum);
 840                 if (err)
 841                         __jbd2_journal_abort_hard(journal);
 842         }
 843         if (!err && !is_journal_aborted(journal))
 844                 err = journal_wait_on_commit_record(journal, cbh);
 845
 846         if (err)
 847                 jbd2_journal_abort(journal, err);
 848
 849         /* End of a transaction!  Finally, we can do checkpoint
 850            processing: any buffers committed as a result of this
 851            transaction can be removed from any checkpoint list it was on
 852            before. */
 853
 854         jbd_debug(3, "JBD: commit phase 6\n");
 855
 856         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 857         J_ASSERT(commit_transaction->t_buffers == NULL);
 858         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 859         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 860         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 861         J_ASSERT(commit_transaction->t_log_list == NULL);
 862
 863 restart_loop:
 864         /*
 865          * As there are other places (journal_unmap_buffer()) adding buffers
 866          * to this list we have to be careful and hold the j_list_lock.
 867          */
 868         spin_lock(&journal->j_list_lock);
 869         while (commit_transaction->t_forget) {
 870                 transaction_t *cp_transaction;
 871                 struct buffer_head *bh;
 872
 873                 jh = commit_transaction->t_forget;
 874                 spin_unlock(&journal->j_list_lock);
 875                 bh = jh2bh(jh);
 876                 jbd_lock_bh_state(bh);
 877                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 878                         jh->b_transaction == journal->j_running_transaction);
 879
 880                 /*
 881                  * If there is undo-protected committed data against
 882                  * this buffer, then we can remove it now.  If it is a
 883                  * buffer needing such protection, the old frozen_data
 884                  * field now points to a committed version of the
 885                  * buffer, so rotate that field to the new committed
 886                  * data.
 887                  *
 888                  * Otherwise, we can just throw away the frozen data now.
 889                  *
 890                  * We also know that the frozen data has already fired
 891                  * its triggers if they exist, so we can clear that too.
 892                  */
 893                 if (jh->b_committed_data) {
 894                         jbd2_free(jh->b_committed_data, bh->b_size);
 895                         jh->b_committed_data = NULL;
 896                         if (jh->b_frozen_data) {
 897                                 jh->b_committed_data = jh->b_frozen_data;
 898                                 jh->b_frozen_data = NULL;
 899                                 jh->b_frozen_triggers = NULL;
 900                         }
 901                 } else if (jh->b_frozen_data) {
 902                         jbd2_free(jh->b_frozen_data, bh->b_size);
 903                         jh->b_frozen_data = NULL;
 904                         jh->b_frozen_triggers = NULL;
 905                 }
 906
 907                 spin_lock(&journal->j_list_lock);
 908                 cp_transaction = jh->b_cp_transaction;
 909                 if (cp_transaction) {
 910                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 911                         cp_transaction->t_chp_stats.cs_dropped++;
 912                         __jbd2_journal_remove_checkpoint(jh);
 913                 }
 914
 915                 /* Only re-checkpoint the buffer_head if it is marked
 916                  * dirty.  If the buffer was added to the BJ_Forget list
 917                  * by jbd2_journal_forget, it may no longer be dirty and
 918                  * there's no point in keeping a checkpoint record for
 919                  * it. */
 920
 921                 /* A buffer which has been freed while still being
 922                  * journaled by a previous transaction may end up still
 923                  * being dirty here, but we want to avoid writing back
 924                  * that buffer in the future now that the last use has
 925                  * been committed.  That's not only a performance gain,
 926                  * it also stops aliasing problems if the buffer is left
 927                  * behind for writeback and gets reallocated for another
 928                  * use in a different page. */
 929                 if (buffer_freed(bh)) {
 930                         clear_buffer_freed(bh);
 931                         clear_buffer_jbddirty(bh);
 932                 }
 933
 934                 if (buffer_jbddirty(bh)) {
 935                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 936                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 937                         if (is_journal_aborted(journal))
 938                                 clear_buffer_jbddirty(bh);
 939                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 940                         __jbd2_journal_refile_buffer(jh);
 941                         jbd_unlock_bh_state(bh);
 942                 } else {
 943                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 944                         /* The buffer on BJ_Forget list and not jbddirty means
 945                          * it has been freed by this transaction and hence it
 946                          * could not have been reallocated until this
 947                          * transaction has committed. *BUT* it could be
 948                          * reallocated once we have written all the data to
 949                          * disk and before we process the buffer on BJ_Forget
 950                          * list. */
 951                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 952                         __jbd2_journal_refile_buffer(jh);
 953                         if (!jh->b_transaction) {
 954                                 jbd_unlock_bh_state(bh);
 955                                  /* needs a brelse */
 956                                 jbd2_journal_remove_journal_head(bh);
 957                                 release_buffer_page(bh);
 958                         } else
 959                                 jbd_unlock_bh_state(bh);
 960                 }
 961                 cond_resched_lock(&journal->j_list_lock);
 962         }
 963         spin_unlock(&journal->j_list_lock);
 964         /*
 965          * This is a bit sleazy.  We use j_list_lock to protect transition
 966          * of a transaction into T_FINISHED state and calling
 967          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 968          * other checkpointing code processing the transaction...
 969          */
 970         spin_lock(&journal->j_state_lock);
 971         spin_lock(&journal->j_list_lock);
 972         /*
 973          * Now recheck if some buffers did not get attached to the transaction
 974          * while the lock was dropped...
 975          */
 976         if (commit_transaction->t_forget) {
 977                 spin_unlock(&journal->j_list_lock);
 978                 spin_unlock(&journal->j_state_lock);
 979                 goto restart_loop;
 980         }
 981
 982         /* Done with this transaction! */
 983
 984         jbd_debug(3, "JBD: commit phase 7\n");
 985
 986         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 987
 988         commit_transaction->t_start = jiffies;
 989         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
 990                                                 commit_transaction->t_start);
 991
 992         /*
 993          * File the transaction for history
 994          */
 995         stats.ts_type = JBD2_STATS_RUN;
 996         stats.ts_tid = commit_transaction->t_tid;
 997         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
 998         spin_lock(&journal->j_history_lock);
 999         memcpy(journal->j_history + journal->j_history_cur, &stats,
1000                         sizeof(stats));
1001         if (++journal->j_history_cur == journal->j_history_max)
1002                 journal->j_history_cur = 0;
1003
1004         /*
1005          * Calculate overall stats
1006          */
1007         journal->j_stats.ts_tid++;
1008         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
1009         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
1010         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
1011         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
1012         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
1013         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
1014         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
1015         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
1016         spin_unlock(&journal->j_history_lock);
1017
1018         commit_transaction->t_state = T_FINISHED;
1019         J_ASSERT(commit_transaction == journal->j_committing_transaction);
1020         journal->j_commit_sequence = commit_transaction->t_tid;
1021         journal->j_committing_transaction = NULL;
1022         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1023
1024         /*
1025          * weight the commit time higher than the average time so we don't
1026          * react too strongly to vast changes in the commit time
1027          */
1028         if (likely(journal->j_average_commit_time))
1029                 journal->j_average_commit_time = (commit_time +
1030                                 journal->j_average_commit_time*3) / 4;
1031         else
1032                 journal->j_average_commit_time = commit_time;
1033         spin_unlock(&journal->j_state_lock);
1034
1035         if (commit_transaction->t_checkpoint_list == NULL &&
1036             commit_transaction->t_checkpoint_io_list == NULL) {
1037                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1038                 to_free = 1;
1039         } else {
1040                 if (journal->j_checkpoint_transactions == NULL) {
1041                         journal->j_checkpoint_transactions = commit_transaction;
1042                         commit_transaction->t_cpnext = commit_transaction;
1043                         commit_transaction->t_cpprev = commit_transaction;
1044                 } else {
1045                         commit_transaction->t_cpnext =
1046                                 journal->j_checkpoint_transactions;
1047                         commit_transaction->t_cpprev =
1048                                 commit_transaction->t_cpnext->t_cpprev;
1049                         commit_transaction->t_cpnext->t_cpprev =
1050                                 commit_transaction;
1051                         commit_transaction->t_cpprev->t_cpnext =
1052                                 commit_transaction;
1053                 }
1054         }
1055         spin_unlock(&journal->j_list_lock);
1056
1057         if (journal->j_commit_callback)
1058                 journal->j_commit_callback(journal, commit_transaction);
1059
1060         trace_jbd2_end_commit(journal, commit_transaction);
1061         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1062                   journal->j_commit_sequence, journal->j_tail_sequence);
1063         if (to_free)
1064                 kfree(commit_transaction);
1065
1066         wake_up(&journal->j_wait_done_commit);
1067 }