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         };
 224
 225         ret = generic_writepages(mapping, &wbc);
 226         return ret;
 227 }
 228
 229 /*
 230  * Submit all the data buffers of inode associated with the transaction to
 231  * disk.
 232  *
 233  * We are in a committing transaction. Therefore no new inode can be added to
 234  * our inode list. We use JI_COMMIT_RUNNING flag to protect inode we currently
 235  * operate on from being released while we write out pages.
 236  */
 237 static int journal_submit_data_buffers(journal_t *journal,
 238                 transaction_t *commit_transaction)
 239 {
 240         struct jbd2_inode *jinode;
 241         int err, ret = 0;
 242         struct address_space *mapping;
 243
 244         spin_lock(&journal->j_list_lock);
 245         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 246                 mapping = jinode->i_vfs_inode->i_mapping;
 247                 jinode->i_flags |= JI_COMMIT_RUNNING;
 248                 spin_unlock(&journal->j_list_lock);
 249                 /*
 250                  * submit the inode data buffers. We use writepage
 251                  * instead of writepages. Because writepages can do
 252                  * block allocation  with delalloc. We need to write
 253                  * only allocated blocks here.
 254                  */
 255                 trace_jbd2_submit_inode_data(jinode->i_vfs_inode);
 256                 err = journal_submit_inode_data_buffers(mapping);
 257                 if (!ret)
 258                         ret = err;
 259                 spin_lock(&journal->j_list_lock);
 260                 J_ASSERT(jinode->i_transaction == commit_transaction);
 261                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 262                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 263         }
 264         spin_unlock(&journal->j_list_lock);
 265         return ret;
 266 }
 267
 268 /*
 269  * Wait for data submitted for writeout, refile inodes to proper
 270  * transaction if needed.
 271  *
 272  */
 273 static int journal_finish_inode_data_buffers(journal_t *journal,
 274                 transaction_t *commit_transaction)
 275 {
 276         struct jbd2_inode *jinode, *next_i;
 277         int err, ret = 0;
 278
 279         /* For locking, see the comment in journal_submit_data_buffers() */
 280         spin_lock(&journal->j_list_lock);
 281         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 282                 jinode->i_flags |= JI_COMMIT_RUNNING;
 283                 spin_unlock(&journal->j_list_lock);
 284                 err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
 285                 if (err) {
 286                         /*
 287                          * Because AS_EIO is cleared by
 288                          * wait_on_page_writeback_range(), set it again so
 289                          * that user process can get -EIO from fsync().
 290                          */
 291                         set_bit(AS_EIO,
 292                                 &jinode->i_vfs_inode->i_mapping->flags);
 293
 294                         if (!ret)
 295                                 ret = err;
 296                 }
 297                 spin_lock(&journal->j_list_lock);
 298                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
 299                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 300         }
 301
 302         /* Now refile inode to proper lists */
 303         list_for_each_entry_safe(jinode, next_i,
 304                                  &commit_transaction->t_inode_list, i_list) {
 305                 list_del(&jinode->i_list);
 306                 if (jinode->i_next_transaction) {
 307                         jinode->i_transaction = jinode->i_next_transaction;
 308                         jinode->i_next_transaction = NULL;
 309                         list_add(&jinode->i_list,
 310                                 &jinode->i_transaction->t_inode_list);
 311                 } else {
 312                         jinode->i_transaction = NULL;
 313                 }
 314         }
 315         spin_unlock(&journal->j_list_lock);
 316
 317         return ret;
 318 }
 319
 320 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 321 {
 322         struct page *page = bh->b_page;
 323         char *addr;
 324         __u32 checksum;
 325
 326         addr = kmap_atomic(page, KM_USER0);
 327         checksum = crc32_be(crc32_sum,
 328                 (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
 329         kunmap_atomic(addr, KM_USER0);
 330
 331         return checksum;
 332 }
 333
 334 static void write_tag_block(int tag_bytes, journal_block_tag_t *tag,
 335                                    unsigned long long block)
 336 {
 337         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
 338         if (tag_bytes > JBD2_TAG_SIZE32)
 339                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
 340 }
 341
 342 /*
 343  * jbd2_journal_commit_transaction
 344  *
 345  * The primary function for committing a transaction to the log.  This
 346  * function is called by the journal thread to begin a complete commit.
 347  */
 348 void jbd2_journal_commit_transaction(journal_t *journal)
 349 {
 350         struct transaction_stats_s stats;
 351         transaction_t *commit_transaction;
 352         struct journal_head *jh, *new_jh, *descriptor;
 353         struct buffer_head **wbuf = journal->j_wbuf;
 354         int bufs;
 355         int flags;
 356         int err;
 357         unsigned long long blocknr;
 358         ktime_t start_time;
 359         u64 commit_time;
 360         char *tagp = NULL;
 361         journal_header_t *header;
 362         journal_block_tag_t *tag = NULL;
 363         int space_left = 0;
 364         int first_tag = 0;
 365         int tag_flag;
 366         int i, to_free = 0;
 367         int tag_bytes = journal_tag_bytes(journal);
 368         struct buffer_head *cbh = NULL; /* For transactional checksums */
 369         __u32 crc32_sum = ~0;
 370         int write_op = WRITE;
 371
 372         /*
 373          * First job: lock down the current transaction and wait for
 374          * all outstanding updates to complete.
 375          */
 376
 377 #ifdef COMMIT_STATS
 378         spin_lock(&journal->j_list_lock);
 379         summarise_journal_usage(journal);
 380         spin_unlock(&journal->j_list_lock);
 381 #endif
 382
 383         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 384         if (journal->j_flags & JBD2_FLUSHED) {
 385                 jbd_debug(3, "super block updated\n");
 386                 jbd2_journal_update_superblock(journal, 1);
 387         } else {
 388                 jbd_debug(3, "superblock not updated\n");
 389         }
 390
 391         J_ASSERT(journal->j_running_transaction != NULL);
 392         J_ASSERT(journal->j_committing_transaction == NULL);
 393
 394         commit_transaction = journal->j_running_transaction;
 395         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 396
 397         trace_jbd2_start_commit(journal, commit_transaction);
 398         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 399                         commit_transaction->t_tid);
 400
 401         spin_lock(&journal->j_state_lock);
 402         commit_transaction->t_state = T_LOCKED;
 403
 404         /*
 405          * Use plugged writes here, since we want to submit several before
 406          * we unplug the device. We don't do explicit unplugging in here,
 407          * instead we rely on sync_buffer() doing the unplug for us.
 408          */
 409         if (commit_transaction->t_synchronous_commit)
 410                 write_op = WRITE_SYNC_PLUG;
 411         trace_jbd2_commit_locking(journal, commit_transaction);
 412         stats.u.run.rs_wait = commit_transaction->t_max_wait;
 413         stats.u.run.rs_locked = jiffies;
 414         stats.u.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 415                                                 stats.u.run.rs_locked);
 416
 417         spin_lock(&commit_transaction->t_handle_lock);
 418         while (commit_transaction->t_updates) {
 419                 DEFINE_WAIT(wait);
 420
 421                 prepare_to_wait(&journal->j_wait_updates, &wait,
 422                                         TASK_UNINTERRUPTIBLE);
 423                 if (commit_transaction->t_updates) {
 424                         spin_unlock(&commit_transaction->t_handle_lock);
 425                         spin_unlock(&journal->j_state_lock);
 426                         schedule();
 427                         spin_lock(&journal->j_state_lock);
 428                         spin_lock(&commit_transaction->t_handle_lock);
 429                 }
 430                 finish_wait(&journal->j_wait_updates, &wait);
 431         }
 432         spin_unlock(&commit_transaction->t_handle_lock);
 433
 434         J_ASSERT (commit_transaction->t_outstanding_credits <=
 435                         journal->j_max_transaction_buffers);
 436
 437         /*
 438          * First thing we are allowed to do is to discard any remaining
 439          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 440          * that there are no such buffers: if a large filesystem
 441          * operation like a truncate needs to split itself over multiple
 442          * transactions, then it may try to do a jbd2_journal_restart() while
 443          * there are still BJ_Reserved buffers outstanding.  These must
 444          * be released cleanly from the current transaction.
 445          *
 446          * In this case, the filesystem must still reserve write access
 447          * again before modifying the buffer in the new transaction, but
 448          * we do not require it to remember exactly which old buffers it
 449          * has reserved.  This is consistent with the existing behaviour
 450          * that multiple jbd2_journal_get_write_access() calls to the same
 451          * buffer are perfectly permissable.
 452          */
 453         while (commit_transaction->t_reserved_list) {
 454                 jh = commit_transaction->t_reserved_list;
 455                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 456                 /*
 457                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 458                  * leave undo-committed data.
 459                  */
 460                 if (jh->b_committed_data) {
 461                         struct buffer_head *bh = jh2bh(jh);
 462
 463                         jbd_lock_bh_state(bh);
 464                         jbd2_free(jh->b_committed_data, bh->b_size);
 465                         jh->b_committed_data = NULL;
 466                         jbd_unlock_bh_state(bh);
 467                 }
 468                 jbd2_journal_refile_buffer(journal, jh);
 469         }
 470
 471         /*
 472          * Now try to drop any written-back buffers from the journal's
 473          * checkpoint lists.  We do this *before* commit because it potentially
 474          * frees some memory
 475          */
 476         spin_lock(&journal->j_list_lock);
 477         __jbd2_journal_clean_checkpoint_list(journal);
 478         spin_unlock(&journal->j_list_lock);
 479
 480         jbd_debug (3, "JBD: commit phase 1\n");
 481
 482         /*
 483          * Switch to a new revoke table.
 484          */
 485         jbd2_journal_switch_revoke_table(journal);
 486
 487         trace_jbd2_commit_flushing(journal, commit_transaction);
 488         stats.u.run.rs_flushing = jiffies;
 489         stats.u.run.rs_locked = jbd2_time_diff(stats.u.run.rs_locked,
 490                                                stats.u.run.rs_flushing);
 491
 492         commit_transaction->t_state = T_FLUSH;
 493         journal->j_committing_transaction = commit_transaction;
 494         journal->j_running_transaction = NULL;
 495         start_time = ktime_get();
 496         commit_transaction->t_log_start = journal->j_head;
 497         wake_up(&journal->j_wait_transaction_locked);
 498         spin_unlock(&journal->j_state_lock);
 499
 500         jbd_debug (3, "JBD: commit phase 2\n");
 501
 502         /*
 503          * Now start flushing things to disk, in the order they appear
 504          * on the transaction lists.  Data blocks go first.
 505          */
 506         err = journal_submit_data_buffers(journal, commit_transaction);
 507         if (err)
 508                 jbd2_journal_abort(journal, err);
 509
 510         jbd2_journal_write_revoke_records(journal, commit_transaction,
 511                                           write_op);
 512
 513         jbd_debug(3, "JBD: commit phase 2\n");
 514
 515         /*
 516          * Way to go: we have now written out all of the data for a
 517          * transaction!  Now comes the tricky part: we need to write out
 518          * metadata.  Loop over the transaction's entire buffer list:
 519          */
 520         spin_lock(&journal->j_state_lock);
 521         commit_transaction->t_state = T_COMMIT;
 522         spin_unlock(&journal->j_state_lock);
 523
 524         trace_jbd2_commit_logging(journal, commit_transaction);
 525         stats.u.run.rs_logging = jiffies;
 526         stats.u.run.rs_flushing = jbd2_time_diff(stats.u.run.rs_flushing,
 527                                                  stats.u.run.rs_logging);
 528         stats.u.run.rs_blocks = commit_transaction->t_outstanding_credits;
 529         stats.u.run.rs_blocks_logged = 0;
 530
 531         J_ASSERT(commit_transaction->t_nr_buffers <=
 532                  commit_transaction->t_outstanding_credits);
 533
 534         err = 0;
 535         descriptor = NULL;
 536         bufs = 0;
 537         while (commit_transaction->t_buffers) {
 538
 539                 /* Find the next buffer to be journaled... */
 540
 541                 jh = commit_transaction->t_buffers;
 542
 543                 /* If we're in abort mode, we just un-journal the buffer and
 544                    release it. */
 545
 546                 if (is_journal_aborted(journal)) {
 547                         clear_buffer_jbddirty(jh2bh(jh));
 548                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 549                         jbd2_buffer_abort_trigger(jh,
 550                                                   jh->b_frozen_data ?
 551                                                   jh->b_frozen_triggers :
 552                                                   jh->b_triggers);
 553                         jbd2_journal_refile_buffer(journal, jh);
 554                         /* If that was the last one, we need to clean up
 555                          * any descriptor buffers which may have been
 556                          * already allocated, even if we are now
 557                          * aborting. */
 558                         if (!commit_transaction->t_buffers)
 559                                 goto start_journal_io;
 560                         continue;
 561                 }
 562
 563                 /* Make sure we have a descriptor block in which to
 564                    record the metadata buffer. */
 565
 566                 if (!descriptor) {
 567                         struct buffer_head *bh;
 568
 569                         J_ASSERT (bufs == 0);
 570
 571                         jbd_debug(4, "JBD: get descriptor\n");
 572
 573                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 574                         if (!descriptor) {
 575                                 jbd2_journal_abort(journal, -EIO);
 576                                 continue;
 577                         }
 578
 579                         bh = jh2bh(descriptor);
 580                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 581                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 582                         header = (journal_header_t *)&bh->b_data[0];
 583                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 584                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 585                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 586
 587                         tagp = &bh->b_data[sizeof(journal_header_t)];
 588                         space_left = bh->b_size - sizeof(journal_header_t);
 589                         first_tag = 1;
 590                         set_buffer_jwrite(bh);
 591                         set_buffer_dirty(bh);
 592                         wbuf[bufs++] = bh;
 593
 594                         /* Record it so that we can wait for IO
 595                            completion later */
 596                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 597                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 598                                         BJ_LogCtl);
 599                 }
 600
 601                 /* Where is the buffer to be written? */
 602
 603                 err = jbd2_journal_next_log_block(journal, &blocknr);
 604                 /* If the block mapping failed, just abandon the buffer
 605                    and repeat this loop: we'll fall into the
 606                    refile-on-abort condition above. */
 607                 if (err) {
 608                         jbd2_journal_abort(journal, err);
 609                         continue;
 610                 }
 611
 612                 /*
 613                  * start_this_handle() uses t_outstanding_credits to determine
 614                  * the free space in the log, but this counter is changed
 615                  * by jbd2_journal_next_log_block() also.
 616                  */
 617                 commit_transaction->t_outstanding_credits--;
 618
 619                 /* Bump b_count to prevent truncate from stumbling over
 620                    the shadowed buffer!  @@@ This can go if we ever get
 621                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 622                 atomic_inc(&jh2bh(jh)->b_count);
 623
 624                 /* Make a temporary IO buffer with which to write it out
 625                    (this will requeue both the metadata buffer and the
 626                    temporary IO buffer). new_bh goes on BJ_IO*/
 627
 628                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 629                 /*
 630                  * akpm: jbd2_journal_write_metadata_buffer() sets
 631                  * new_bh->b_transaction to commit_transaction.
 632                  * We need to clean this up before we release new_bh
 633                  * (which is of type BJ_IO)
 634                  */
 635                 JBUFFER_TRACE(jh, "ph3: write metadata");
 636                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 637                                                       jh, &new_jh, blocknr);
 638                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 639                 wbuf[bufs++] = jh2bh(new_jh);
 640
 641                 /* Record the new block's tag in the current descriptor
 642                    buffer */
 643
 644                 tag_flag = 0;
 645                 if (flags & 1)
 646                         tag_flag |= JBD2_FLAG_ESCAPE;
 647                 if (!first_tag)
 648                         tag_flag |= JBD2_FLAG_SAME_UUID;
 649
 650                 tag = (journal_block_tag_t *) tagp;
 651                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 652                 tag->t_flags = cpu_to_be32(tag_flag);
 653                 tagp += tag_bytes;
 654                 space_left -= tag_bytes;
 655
 656                 if (first_tag) {
 657                         memcpy (tagp, journal->j_uuid, 16);
 658                         tagp += 16;
 659                         space_left -= 16;
 660                         first_tag = 0;
 661                 }
 662
 663                 /* If there's no more to do, or if the descriptor is full,
 664                    let the IO rip! */
 665
 666                 if (bufs == journal->j_wbufsize ||
 667                     commit_transaction->t_buffers == NULL ||
 668                     space_left < tag_bytes + 16) {
 669
 670                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 671
 672                         /* Write an end-of-descriptor marker before
 673                            submitting the IOs.  "tag" still points to
 674                            the last tag we set up. */
 675
 676                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 677
 678 start_journal_io:
 679                         for (i = 0; i < bufs; i++) {
 680                                 struct buffer_head *bh = wbuf[i];
 681                                 /*
 682                                  * Compute checksum.
 683                                  */
 684                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 685                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 686                                         crc32_sum =
 687                                             jbd2_checksum_data(crc32_sum, bh);
 688                                 }
 689
 690                                 lock_buffer(bh);
 691                                 clear_buffer_dirty(bh);
 692                                 set_buffer_uptodate(bh);
 693                                 bh->b_end_io = journal_end_buffer_io_sync;
 694                                 submit_bh(write_op, bh);
 695                         }
 696                         cond_resched();
 697                         stats.u.run.rs_blocks_logged += bufs;
 698
 699                         /* Force a new descriptor to be generated next
 700                            time round the loop. */
 701                         descriptor = NULL;
 702                         bufs = 0;
 703                 }
 704         }
 705
 706         /* Done it all: now write the commit record asynchronously. */
 707
 708         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 709                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 710                 err = journal_submit_commit_record(journal, commit_transaction,
 711                                                  &cbh, crc32_sum);
 712                 if (err)
 713                         __jbd2_journal_abort_hard(journal);
 714         }
 715
 716         /*
 717          * This is the right place to wait for data buffers both for ASYNC
 718          * and !ASYNC commit. If commit is ASYNC, we need to wait only after
 719          * the commit block went to disk (which happens above). If commit is
 720          * SYNC, we need to wait for data buffers before we start writing
 721          * commit block, which happens below in such setting.
 722          */
 723         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 724         if (err) {
 725                 printk(KERN_WARNING
 726                         "JBD2: Detected IO errors while flushing file data "
 727                        "on %s\n", journal->j_devname);
 728                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 729                         jbd2_journal_abort(journal, err);
 730                 err = 0;
 731         }
 732
 733         /* Lo and behold: we have just managed to send a transaction to
 734            the log.  Before we can commit it, wait for the IO so far to
 735            complete.  Control buffers being written are on the
 736            transaction's t_log_list queue, and metadata buffers are on
 737            the t_iobuf_list queue.
 738
 739            Wait for the buffers in reverse order.  That way we are
 740            less likely to be woken up until all IOs have completed, and
 741            so we incur less scheduling load.
 742         */
 743
 744         jbd_debug(3, "JBD: commit phase 3\n");
 745
 746         /*
 747          * akpm: these are BJ_IO, and j_list_lock is not needed.
 748          * See __journal_try_to_free_buffer.
 749          */
 750 wait_for_iobuf:
 751         while (commit_transaction->t_iobuf_list != NULL) {
 752                 struct buffer_head *bh;
 753
 754                 jh = commit_transaction->t_iobuf_list->b_tprev;
 755                 bh = jh2bh(jh);
 756                 if (buffer_locked(bh)) {
 757                         wait_on_buffer(bh);
 758                         goto wait_for_iobuf;
 759                 }
 760                 if (cond_resched())
 761                         goto wait_for_iobuf;
 762
 763                 if (unlikely(!buffer_uptodate(bh)))
 764                         err = -EIO;
 765
 766                 clear_buffer_jwrite(bh);
 767
 768                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 769                 jbd2_journal_unfile_buffer(journal, jh);
 770
 771                 /*
 772                  * ->t_iobuf_list should contain only dummy buffer_heads
 773                  * which were created by jbd2_journal_write_metadata_buffer().
 774                  */
 775                 BUFFER_TRACE(bh, "dumping temporary bh");
 776                 jbd2_journal_put_journal_head(jh);
 777                 __brelse(bh);
 778                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 779                 free_buffer_head(bh);
 780
 781                 /* We also have to unlock and free the corresponding
 782                    shadowed buffer */
 783                 jh = commit_transaction->t_shadow_list->b_tprev;
 784                 bh = jh2bh(jh);
 785                 clear_bit(BH_JWrite, &bh->b_state);
 786                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 787
 788                 /* The metadata is now released for reuse, but we need
 789                    to remember it against this transaction so that when
 790                    we finally commit, we can do any checkpointing
 791                    required. */
 792                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 793                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 794                 /* Wake up any transactions which were waiting for this
 795                    IO to complete */
 796                 wake_up_bit(&bh->b_state, BH_Unshadow);
 797                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 798                 __brelse(bh);
 799         }
 800
 801         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 802
 803         jbd_debug(3, "JBD: commit phase 4\n");
 804
 805         /* Here we wait for the revoke record and descriptor record buffers */
 806  wait_for_ctlbuf:
 807         while (commit_transaction->t_log_list != NULL) {
 808                 struct buffer_head *bh;
 809
 810                 jh = commit_transaction->t_log_list->b_tprev;
 811                 bh = jh2bh(jh);
 812                 if (buffer_locked(bh)) {
 813                         wait_on_buffer(bh);
 814                         goto wait_for_ctlbuf;
 815                 }
 816                 if (cond_resched())
 817                         goto wait_for_ctlbuf;
 818
 819                 if (unlikely(!buffer_uptodate(bh)))
 820                         err = -EIO;
 821
 822                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 823                 clear_buffer_jwrite(bh);
 824                 jbd2_journal_unfile_buffer(journal, jh);
 825                 jbd2_journal_put_journal_head(jh);
 826                 __brelse(bh);           /* One for getblk */
 827                 /* AKPM: bforget here */
 828         }
 829
 830         if (err)
 831                 jbd2_journal_abort(journal, err);
 832
 833         jbd_debug(3, "JBD: commit phase 5\n");
 834
 835         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 836                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 837                 err = journal_submit_commit_record(journal, commit_transaction,
 838                                                 &cbh, crc32_sum);
 839                 if (err)
 840                         __jbd2_journal_abort_hard(journal);
 841         }
 842         if (!err && !is_journal_aborted(journal))
 843                 err = journal_wait_on_commit_record(journal, cbh);
 844
 845         if (err)
 846                 jbd2_journal_abort(journal, err);
 847
 848         /* End of a transaction!  Finally, we can do checkpoint
 849            processing: any buffers committed as a result of this
 850            transaction can be removed from any checkpoint list it was on
 851            before. */
 852
 853         jbd_debug(3, "JBD: commit phase 6\n");
 854
 855         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 856         J_ASSERT(commit_transaction->t_buffers == NULL);
 857         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 858         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 859         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 860         J_ASSERT(commit_transaction->t_log_list == NULL);
 861
 862 restart_loop:
 863         /*
 864          * As there are other places (journal_unmap_buffer()) adding buffers
 865          * to this list we have to be careful and hold the j_list_lock.
 866          */
 867         spin_lock(&journal->j_list_lock);
 868         while (commit_transaction->t_forget) {
 869                 transaction_t *cp_transaction;
 870                 struct buffer_head *bh;
 871
 872                 jh = commit_transaction->t_forget;
 873                 spin_unlock(&journal->j_list_lock);
 874                 bh = jh2bh(jh);
 875                 jbd_lock_bh_state(bh);
 876                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 877                         jh->b_transaction == journal->j_running_transaction);
 878
 879                 /*
 880                  * If there is undo-protected committed data against
 881                  * this buffer, then we can remove it now.  If it is a
 882                  * buffer needing such protection, the old frozen_data
 883                  * field now points to a committed version of the
 884                  * buffer, so rotate that field to the new committed
 885                  * data.
 886                  *
 887                  * Otherwise, we can just throw away the frozen data now.
 888                  *
 889                  * We also know that the frozen data has already fired
 890                  * its triggers if they exist, so we can clear that too.
 891                  */
 892                 if (jh->b_committed_data) {
 893                         jbd2_free(jh->b_committed_data, bh->b_size);
 894                         jh->b_committed_data = NULL;
 895                         if (jh->b_frozen_data) {
 896                                 jh->b_committed_data = jh->b_frozen_data;
 897                                 jh->b_frozen_data = NULL;
 898                                 jh->b_frozen_triggers = NULL;
 899                         }
 900                 } else if (jh->b_frozen_data) {
 901                         jbd2_free(jh->b_frozen_data, bh->b_size);
 902                         jh->b_frozen_data = NULL;
 903                         jh->b_frozen_triggers = NULL;
 904                 }
 905
 906                 spin_lock(&journal->j_list_lock);
 907                 cp_transaction = jh->b_cp_transaction;
 908                 if (cp_transaction) {
 909                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 910                         cp_transaction->t_chp_stats.cs_dropped++;
 911                         __jbd2_journal_remove_checkpoint(jh);
 912                 }
 913
 914                 /* Only re-checkpoint the buffer_head if it is marked
 915                  * dirty.  If the buffer was added to the BJ_Forget list
 916                  * by jbd2_journal_forget, it may no longer be dirty and
 917                  * there's no point in keeping a checkpoint record for
 918                  * it. */
 919
 920                 /* A buffer which has been freed while still being
 921                  * journaled by a previous transaction may end up still
 922                  * being dirty here, but we want to avoid writing back
 923                  * that buffer in the future now that the last use has
 924                  * been committed.  That's not only a performance gain,
 925                  * it also stops aliasing problems if the buffer is left
 926                  * behind for writeback and gets reallocated for another
 927                  * use in a different page. */
 928                 if (buffer_freed(bh)) {
 929                         clear_buffer_freed(bh);
 930                         clear_buffer_jbddirty(bh);
 931                 }
 932
 933                 if (buffer_jbddirty(bh)) {
 934                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 935                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 936                         if (is_journal_aborted(journal))
 937                                 clear_buffer_jbddirty(bh);
 938                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 939                         __jbd2_journal_refile_buffer(jh);
 940                         jbd_unlock_bh_state(bh);
 941                 } else {
 942                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 943                         /* The buffer on BJ_Forget list and not jbddirty means
 944                          * it has been freed by this transaction and hence it
 945                          * could not have been reallocated until this
 946                          * transaction has committed. *BUT* it could be
 947                          * reallocated once we have written all the data to
 948                          * disk and before we process the buffer on BJ_Forget
 949                          * list. */
 950                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 951                         __jbd2_journal_refile_buffer(jh);
 952                         if (!jh->b_transaction) {
 953                                 jbd_unlock_bh_state(bh);
 954                                  /* needs a brelse */
 955                                 jbd2_journal_remove_journal_head(bh);
 956                                 release_buffer_page(bh);
 957                         } else
 958                                 jbd_unlock_bh_state(bh);
 959                 }
 960                 cond_resched_lock(&journal->j_list_lock);
 961         }
 962         spin_unlock(&journal->j_list_lock);
 963         /*
 964          * This is a bit sleazy.  We use j_list_lock to protect transition
 965          * of a transaction into T_FINISHED state and calling
 966          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 967          * other checkpointing code processing the transaction...
 968          */
 969         spin_lock(&journal->j_state_lock);
 970         spin_lock(&journal->j_list_lock);
 971         /*
 972          * Now recheck if some buffers did not get attached to the transaction
 973          * while the lock was dropped...
 974          */
 975         if (commit_transaction->t_forget) {
 976                 spin_unlock(&journal->j_list_lock);
 977                 spin_unlock(&journal->j_state_lock);
 978                 goto restart_loop;
 979         }
 980
 981         /* Done with this transaction! */
 982
 983         jbd_debug(3, "JBD: commit phase 7\n");
 984
 985         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 986
 987         commit_transaction->t_start = jiffies;
 988         stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
 989                                                 commit_transaction->t_start);
 990
 991         /*
 992          * File the transaction for history
 993          */
 994         stats.ts_type = JBD2_STATS_RUN;
 995         stats.ts_tid = commit_transaction->t_tid;
 996         stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
 997         spin_lock(&journal->j_history_lock);
 998         memcpy(journal->j_history + journal->j_history_cur, &stats,
 999                         sizeof(stats));
1000         if (++journal->j_history_cur == journal->j_history_max)
1001                 journal->j_history_cur = 0;
1002
1003         /*
1004          * Calculate overall stats
1005          */
1006         journal->j_stats.ts_tid++;
1007         journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
1008         journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
1009         journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
1010         journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
1011         journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
1012         journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
1013         journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
1014         journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
1015         spin_unlock(&journal->j_history_lock);
1016
1017         commit_transaction->t_state = T_FINISHED;
1018         J_ASSERT(commit_transaction == journal->j_committing_transaction);
1019         journal->j_commit_sequence = commit_transaction->t_tid;
1020         journal->j_committing_transaction = NULL;
1021         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1022
1023         /*
1024          * weight the commit time higher than the average time so we don't
1025          * react too strongly to vast changes in the commit time
1026          */
1027         if (likely(journal->j_average_commit_time))
1028                 journal->j_average_commit_time = (commit_time +
1029                                 journal->j_average_commit_time*3) / 4;
1030         else
1031                 journal->j_average_commit_time = commit_time;
1032         spin_unlock(&journal->j_state_lock);
1033
1034         if (commit_transaction->t_checkpoint_list == NULL &&
1035             commit_transaction->t_checkpoint_io_list == NULL) {
1036                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1037                 to_free = 1;
1038         } else {
1039                 if (journal->j_checkpoint_transactions == NULL) {
1040                         journal->j_checkpoint_transactions = commit_transaction;
1041                         commit_transaction->t_cpnext = commit_transaction;
1042                         commit_transaction->t_cpprev = commit_transaction;
1043                 } else {
1044                         commit_transaction->t_cpnext =
1045                                 journal->j_checkpoint_transactions;
1046                         commit_transaction->t_cpprev =
1047                                 commit_transaction->t_cpnext->t_cpprev;
1048                         commit_transaction->t_cpnext->t_cpprev =
1049                                 commit_transaction;
1050                         commit_transaction->t_cpprev->t_cpnext =
1051                                 commit_transaction;
1052                 }
1053         }
1054         spin_unlock(&journal->j_list_lock);
1055
1056         if (journal->j_commit_callback)
1057                 journal->j_commit_callback(journal, commit_transaction);
1058
1059         trace_jbd2_end_commit(journal, commit_transaction);
1060         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1061                   journal->j_commit_sequence, journal->j_tail_sequence);
1062         if (to_free)
1063                 kfree(commit_transaction);
1064
1065         wake_up(&journal->j_wait_done_commit);
1066 }