fs/jbd2/commit.c

   1 /*
   2  * linux/fs/jbd2/commit.c
   3  *
   4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
   5  *
   6  * Copyright 1998 Red Hat corp --- All Rights Reserved
   7  *
   8  * This file is part of the Linux kernel and is made available under
   9  * the terms of the GNU General Public License, version 2, or at your
  10  * option, any later version, incorporated herein by reference.
  11  *
  12  * Journal commit routines for the generic filesystem journaling code;
  13  * part of the ext2fs journaling system.
  14  */
  15
  16 #include <linux/time.h>
  17 #include <linux/fs.h>
  18 #include <linux/jbd2.h>
  19 #include <linux/errno.h>
  20 #include <linux/slab.h>
  21 #include <linux/mm.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/jiffies.h>
  24 #include <linux/crc32.h>
  25 #include <linux/writeback.h>
  26 #include <linux/backing-dev.h>
  27 #include <linux/bio.h>
  28 #include <linux/blkdev.h>
  29 #include <trace/events/jbd2.h>
  30
  31 /*
  32  * Default IO end handler for temporary BJ_IO buffer_heads.
  33  */
  34 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
  35 {
  36         BUFFER_TRACE(bh, "");
  37         if (uptodate)
  38                 set_buffer_uptodate(bh);
  39         else
  40                 clear_buffer_uptodate(bh);
  41         unlock_buffer(bh);
  42 }
  43
  44 /*
  45  * When an ext4 file is truncated, it is possible that some pages are not
  46  * successfully freed, because they are attached to a committing transaction.
  47  * After the transaction commits, these pages are left on the LRU, with no
  48  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
  49  * by the VM, but their apparent absence upsets the VM accounting, and it makes
  50  * the numbers in /proc/meminfo look odd.
  51  *
  52  * So here, we have a buffer which has just come off the forget list.  Look to
  53  * see if we can strip all buffers from the backing page.
  54  *
  55  * Called under lock_journal(), and possibly under journal_datalist_lock.  The
  56  * caller provided us with a ref against the buffer, and we drop that here.
  57  */
  58 static void release_buffer_page(struct buffer_head *bh)
  59 {
  60         struct page *page;
  61
  62         if (buffer_dirty(bh))
  63                 goto nope;
  64         if (atomic_read(&bh->b_count) != 1)
  65                 goto nope;
  66         page = bh->b_page;
  67         if (!page)
  68                 goto nope;
  69         if (page->mapping)
  70                 goto nope;
  71
  72         /* OK, it's a truncated page */
  73         if (!trylock_page(page))
  74                 goto nope;
  75
  76         page_cache_get(page);
  77         __brelse(bh);
  78         try_to_free_buffers(page);
  79         unlock_page(page);
  80         page_cache_release(page);
  81         return;
  82
  83 nope:
  84         __brelse(bh);
  85 }
  86
  87 /*
  88  * Done it all: now submit the commit record.  We should have
  89  * cleaned up our previous buffers by now, so if we are in abort
  90  * mode we can now just skip the rest of the journal write
  91  * entirely.
  92  *
  93  * Returns 1 if the journal needs to be aborted or 0 on success
  94  */
  95 static int journal_submit_commit_record(journal_t *journal,
  96                                         transaction_t *commit_transaction,
  97                                         struct buffer_head **cbh,
  98                                         __u32 crc32_sum)
  99 {
 100         struct journal_head *descriptor;
 101         struct commit_header *tmp;
 102         struct buffer_head *bh;
 103         int ret;
 104         int barrier_done = 0;
 105         struct timespec now = current_kernel_time();
 106
 107         if (is_journal_aborted(journal))
 108                 return 0;
 109
 110         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 111         if (!descriptor)
 112                 return 1;
 113
 114         bh = jh2bh(descriptor);
 115
 116         tmp = (struct commit_header *)bh->b_data;
 117         tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
 118         tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
 119         tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 120         tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
 121         tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);
 122
 123         if (JBD2_HAS_COMPAT_FEATURE(journal,
 124                                     JBD2_FEATURE_COMPAT_CHECKSUM)) {
 125                 tmp->h_chksum_type      = JBD2_CRC32_CHKSUM;
 126                 tmp->h_chksum_size      = JBD2_CRC32_CHKSUM_SIZE;
 127                 tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
 128         }
 129
 130         JBUFFER_TRACE(descriptor, "submit commit block");
 131         lock_buffer(bh);
 132         clear_buffer_dirty(bh);
 133         set_buffer_uptodate(bh);
 134         bh->b_end_io = journal_end_buffer_io_sync;
 135
 136         if (journal->j_flags & JBD2_BARRIER &&
 137             !JBD2_HAS_INCOMPAT_FEATURE(journal,
 138                                        JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 139                 set_buffer_ordered(bh);
 140                 barrier_done = 1;
 141         }
 142         ret = submit_bh(WRITE_SYNC_PLUG, bh);
 143         if (barrier_done)
 144                 clear_buffer_ordered(bh);
 145
 146         /* is it possible for another commit to fail at roughly
 147          * the same time as this one?  If so, we don't want to
 148          * trust the barrier flag in the super, but instead want
 149          * to remember if we sent a barrier request
 150          */
 151         if (ret == -EOPNOTSUPP && barrier_done) {
 152                 printk(KERN_WARNING
 153                        "JBD: barrier-based sync failed on %s - "
 154                        "disabling barriers\n", journal->j_devname);
 155                 spin_lock(&journal->j_state_lock);
 156                 journal->j_flags &= ~JBD2_BARRIER;
 157                 spin_unlock(&journal->j_state_lock);
 158
 159                 /* And try again, without the barrier */
 160                 lock_buffer(bh);
 161                 set_buffer_uptodate(bh);
 162                 clear_buffer_dirty(bh);
 163                 ret = submit_bh(WRITE_SYNC_PLUG, bh);
 164         }
 165         *cbh = bh;
 166         return ret;
 167 }
 168
 169 /*
 170  * This function along with journal_submit_commit_record
 171  * allows to write the commit record asynchronously.
 172  */
 173 static int journal_wait_on_commit_record(journal_t *journal,
 174                                          struct buffer_head *bh)
 175 {
 176         int ret = 0;
 177
 178 retry:
 179         clear_buffer_dirty(bh);
 180         wait_on_buffer(bh);
 181         if (buffer_eopnotsupp(bh) && (journal->j_flags & JBD2_BARRIER)) {
 182                 printk(KERN_WARNING
 183                        "JBD2: wait_on_commit_record: sync failed on %s - "
 184                        "disabling barriers\n", journal->j_devname);
 185                 spin_lock(&journal->j_state_lock);
 186                 journal->j_flags &= ~JBD2_BARRIER;
 187                 spin_unlock(&journal->j_state_lock);
 188
 189                 lock_buffer(bh);
 190                 clear_buffer_dirty(bh);
 191                 set_buffer_uptodate(bh);
 192                 bh->b_end_io = journal_end_buffer_io_sync;
 193
 194                 ret = submit_bh(WRITE_SYNC_PLUG, bh);
 195                 if (ret) {
 196                         unlock_buffer(bh);
 197                         return ret;
 198                 }
 199                 goto retry;
 200         }
 201
 202         if (unlikely(!buffer_uptodate(bh)))
 203                 ret = -EIO;
 204         put_bh(bh);            /* One for getblk() */
 205         jbd2_journal_put_journal_head(bh2jh(bh));
 206
 207         return ret;
 208 }
 209
 210 /*
 211  * write the filemap data using writepage() address_space_operations.
 212  * We don't do block allocation here even for delalloc. We don't
 213  * use writepages() because with dealyed allocation we may be doing
 214  * block allocation in writepages().
 215  */
 216 static int journal_submit_inode_data_buffers(struct address_space *mapping)
 217 {
 218         int ret;
 219         struct writeback_control wbc = {
 220                 .sync_mode =  WB_SYNC_ALL,
 221                 .nr_to_write = mapping->nrpages * 2,
 222                 .range_start = 0,
 223                 .range_end = i_size_read(mapping->host),
 224         };
 225
 226         ret = generic_writepages(mapping, &wbc);
 227         return ret;
 228 }
 229
 230 /*
 231  * Submit all the data buffers of inode associated with the transaction to
 232  * disk.
 233  *
 234  * We are in a committing transaction. Therefore no new inode can be added to
 235  * our inode list. We use JI_COMMIT_RUNNING flag to protect inode we currently
 236  * operate on from being released while we write out pages.
 237  */
 238 static int journal_submit_data_buffers(journal_t *journal,
 239                 transaction_t *commit_transaction)
 240 {
 241         struct jbd2_inode *jinode;
 242         int err, ret = 0;
 243         struct address_space *mapping;
 244
 245         spin_lock(&journal->j_list_lock);
 246         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 247                 mapping = jinode->i_vfs_inode->i_mapping;
 248                 jinode->i_flags |= JI_COMMIT_RUNNING;
 249                 spin_unlock(&journal->j_list_lock);
 250                 /*
 251                  * submit the inode data buffers. We use writepage
 252                  * instead of writepages. Because writepages can do
 253                  * block allocation  with delalloc. We need to write
 254                  * only allocated blocks here.
 255                  */
 256                 trace_jbd2_submit_inode_data(jinode->i_vfs_inode);
 257                 err = journal_submit_inode_data_buffers(mapping);
 258                 if (!ret)
 259                         ret = err;
 260                 spin_lock(&journal->j_list_lock);
 261                 J_ASSERT(jinode->i_transaction == commit_transaction);
 262                 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.run.rs_wait = commit_transaction->t_max_wait;
 414         stats.run.rs_locked = jiffies;
 415         stats.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 416                                               stats.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.run.rs_flushing = jiffies;
 490         stats.run.rs_locked = jbd2_time_diff(stats.run.rs_locked,
 491                                              stats.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.run.rs_logging = jiffies;
 527         stats.run.rs_flushing = jbd2_time_diff(stats.run.rs_flushing,
 528                                                stats.run.rs_logging);
 529         stats.run.rs_blocks = commit_transaction->t_outstanding_credits;
 530         stats.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.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                 if (journal->j_flags & JBD2_BARRIER)
 716                         blkdev_issue_flush(journal->j_dev, NULL);
 717         }
 718
 719         /*
 720          * This is the right place to wait for data buffers both for ASYNC
 721          * and !ASYNC commit. If commit is ASYNC, we need to wait only after
 722          * the commit block went to disk (which happens above). If commit is
 723          * SYNC, we need to wait for data buffers before we start writing
 724          * commit block, which happens below in such setting.
 725          */
 726         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 727         if (err) {
 728                 printk(KERN_WARNING
 729                         "JBD2: Detected IO errors while flushing file data "
 730                        "on %s\n", journal->j_devname);
 731                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 732                         jbd2_journal_abort(journal, err);
 733                 err = 0;
 734         }
 735
 736         /* Lo and behold: we have just managed to send a transaction to
 737            the log.  Before we can commit it, wait for the IO so far to
 738            complete.  Control buffers being written are on the
 739            transaction's t_log_list queue, and metadata buffers are on
 740            the t_iobuf_list queue.
 741
 742            Wait for the buffers in reverse order.  That way we are
 743            less likely to be woken up until all IOs have completed, and
 744            so we incur less scheduling load.
 745         */
 746
 747         jbd_debug(3, "JBD: commit phase 3\n");
 748
 749         /*
 750          * akpm: these are BJ_IO, and j_list_lock is not needed.
 751          * See __journal_try_to_free_buffer.
 752          */
 753 wait_for_iobuf:
 754         while (commit_transaction->t_iobuf_list != NULL) {
 755                 struct buffer_head *bh;
 756
 757                 jh = commit_transaction->t_iobuf_list->b_tprev;
 758                 bh = jh2bh(jh);
 759                 if (buffer_locked(bh)) {
 760                         wait_on_buffer(bh);
 761                         goto wait_for_iobuf;
 762                 }
 763                 if (cond_resched())
 764                         goto wait_for_iobuf;
 765
 766                 if (unlikely(!buffer_uptodate(bh)))
 767                         err = -EIO;
 768
 769                 clear_buffer_jwrite(bh);
 770
 771                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 772                 jbd2_journal_unfile_buffer(journal, jh);
 773
 774                 /*
 775                  * ->t_iobuf_list should contain only dummy buffer_heads
 776                  * which were created by jbd2_journal_write_metadata_buffer().
 777                  */
 778                 BUFFER_TRACE(bh, "dumping temporary bh");
 779                 jbd2_journal_put_journal_head(jh);
 780                 __brelse(bh);
 781                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 782                 free_buffer_head(bh);
 783
 784                 /* We also have to unlock and free the corresponding
 785                    shadowed buffer */
 786                 jh = commit_transaction->t_shadow_list->b_tprev;
 787                 bh = jh2bh(jh);
 788                 clear_bit(BH_JWrite, &bh->b_state);
 789                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 790
 791                 /* The metadata is now released for reuse, but we need
 792                    to remember it against this transaction so that when
 793                    we finally commit, we can do any checkpointing
 794                    required. */
 795                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 796                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 797                 /* Wake up any transactions which were waiting for this
 798                    IO to complete */
 799                 wake_up_bit(&bh->b_state, BH_Unshadow);
 800                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 801                 __brelse(bh);
 802         }
 803
 804         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 805
 806         jbd_debug(3, "JBD: commit phase 4\n");
 807
 808         /* Here we wait for the revoke record and descriptor record buffers */
 809  wait_for_ctlbuf:
 810         while (commit_transaction->t_log_list != NULL) {
 811                 struct buffer_head *bh;
 812
 813                 jh = commit_transaction->t_log_list->b_tprev;
 814                 bh = jh2bh(jh);
 815                 if (buffer_locked(bh)) {
 816                         wait_on_buffer(bh);
 817                         goto wait_for_ctlbuf;
 818                 }
 819                 if (cond_resched())
 820                         goto wait_for_ctlbuf;
 821
 822                 if (unlikely(!buffer_uptodate(bh)))
 823                         err = -EIO;
 824
 825                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 826                 clear_buffer_jwrite(bh);
 827                 jbd2_journal_unfile_buffer(journal, jh);
 828                 jbd2_journal_put_journal_head(jh);
 829                 __brelse(bh);           /* One for getblk */
 830                 /* AKPM: bforget here */
 831         }
 832
 833         if (err)
 834                 jbd2_journal_abort(journal, err);
 835
 836         jbd_debug(3, "JBD: commit phase 5\n");
 837
 838         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 839                                        JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 840                 err = journal_submit_commit_record(journal, commit_transaction,
 841                                                 &cbh, crc32_sum);
 842                 if (err)
 843                         __jbd2_journal_abort_hard(journal);
 844         }
 845         if (!err && !is_journal_aborted(journal))
 846                 err = journal_wait_on_commit_record(journal, cbh);
 847
 848         if (err)
 849                 jbd2_journal_abort(journal, err);
 850
 851         /* End of a transaction!  Finally, we can do checkpoint
 852            processing: any buffers committed as a result of this
 853            transaction can be removed from any checkpoint list it was on
 854            before. */
 855
 856         jbd_debug(3, "JBD: commit phase 6\n");
 857
 858         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 859         J_ASSERT(commit_transaction->t_buffers == NULL);
 860         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 861         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 862         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 863         J_ASSERT(commit_transaction->t_log_list == NULL);
 864
 865 restart_loop:
 866         /*
 867          * As there are other places (journal_unmap_buffer()) adding buffers
 868          * to this list we have to be careful and hold the j_list_lock.
 869          */
 870         spin_lock(&journal->j_list_lock);
 871         while (commit_transaction->t_forget) {
 872                 transaction_t *cp_transaction;
 873                 struct buffer_head *bh;
 874
 875                 jh = commit_transaction->t_forget;
 876                 spin_unlock(&journal->j_list_lock);
 877                 bh = jh2bh(jh);
 878                 jbd_lock_bh_state(bh);
 879                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 880                         jh->b_transaction == journal->j_running_transaction);
 881
 882                 /*
 883                  * If there is undo-protected committed data against
 884                  * this buffer, then we can remove it now.  If it is a
 885                  * buffer needing such protection, the old frozen_data
 886                  * field now points to a committed version of the
 887                  * buffer, so rotate that field to the new committed
 888                  * data.
 889                  *
 890                  * Otherwise, we can just throw away the frozen data now.
 891                  *
 892                  * We also know that the frozen data has already fired
 893                  * its triggers if they exist, so we can clear that too.
 894                  */
 895                 if (jh->b_committed_data) {
 896                         jbd2_free(jh->b_committed_data, bh->b_size);
 897                         jh->b_committed_data = NULL;
 898                         if (jh->b_frozen_data) {
 899                                 jh->b_committed_data = jh->b_frozen_data;
 900                                 jh->b_frozen_data = NULL;
 901                                 jh->b_frozen_triggers = NULL;
 902                         }
 903                 } else if (jh->b_frozen_data) {
 904                         jbd2_free(jh->b_frozen_data, bh->b_size);
 905                         jh->b_frozen_data = NULL;
 906                         jh->b_frozen_triggers = NULL;
 907                 }
 908
 909                 spin_lock(&journal->j_list_lock);
 910                 cp_transaction = jh->b_cp_transaction;
 911                 if (cp_transaction) {
 912                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 913                         cp_transaction->t_chp_stats.cs_dropped++;
 914                         __jbd2_journal_remove_checkpoint(jh);
 915                 }
 916
 917                 /* Only re-checkpoint the buffer_head if it is marked
 918                  * dirty.  If the buffer was added to the BJ_Forget list
 919                  * by jbd2_journal_forget, it may no longer be dirty and
 920                  * there's no point in keeping a checkpoint record for
 921                  * it. */
 922
 923                 /* A buffer which has been freed while still being
 924                  * journaled by a previous transaction may end up still
 925                  * being dirty here, but we want to avoid writing back
 926                  * that buffer in the future now that the last use has
 927                  * been committed.  That's not only a performance gain,
 928                  * it also stops aliasing problems if the buffer is left
 929                  * behind for writeback and gets reallocated for another
 930                  * use in a different page. */
 931                 if (buffer_freed(bh)) {
 932                         clear_buffer_freed(bh);
 933                         clear_buffer_jbddirty(bh);
 934                 }
 935
 936                 if (buffer_jbddirty(bh)) {
 937                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 938                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 939                         if (is_journal_aborted(journal))
 940                                 clear_buffer_jbddirty(bh);
 941                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 942                         __jbd2_journal_refile_buffer(jh);
 943                         jbd_unlock_bh_state(bh);
 944                 } else {
 945                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 946                         /* The buffer on BJ_Forget list and not jbddirty means
 947                          * it has been freed by this transaction and hence it
 948                          * could not have been reallocated until this
 949                          * transaction has committed. *BUT* it could be
 950                          * reallocated once we have written all the data to
 951                          * disk and before we process the buffer on BJ_Forget
 952                          * list. */
 953                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 954                         __jbd2_journal_refile_buffer(jh);
 955                         if (!jh->b_transaction) {
 956                                 jbd_unlock_bh_state(bh);
 957                                  /* needs a brelse */
 958                                 jbd2_journal_remove_journal_head(bh);
 959                                 release_buffer_page(bh);
 960                         } else
 961                                 jbd_unlock_bh_state(bh);
 962                 }
 963                 cond_resched_lock(&journal->j_list_lock);
 964         }
 965         spin_unlock(&journal->j_list_lock);
 966         /*
 967          * This is a bit sleazy.  We use j_list_lock to protect transition
 968          * of a transaction into T_FINISHED state and calling
 969          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 970          * other checkpointing code processing the transaction...
 971          */
 972         spin_lock(&journal->j_state_lock);
 973         spin_lock(&journal->j_list_lock);
 974         /*
 975          * Now recheck if some buffers did not get attached to the transaction
 976          * while the lock was dropped...
 977          */
 978         if (commit_transaction->t_forget) {
 979                 spin_unlock(&journal->j_list_lock);
 980                 spin_unlock(&journal->j_state_lock);
 981                 goto restart_loop;
 982         }
 983
 984         /* Done with this transaction! */
 985
 986         jbd_debug(3, "JBD: commit phase 7\n");
 987
 988         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 989
 990         commit_transaction->t_start = jiffies;
 991         stats.run.rs_logging = jbd2_time_diff(stats.run.rs_logging,
 992                                               commit_transaction->t_start);
 993
 994         /*
 995          * File the transaction statistics
 996          */
 997         stats.ts_tid = commit_transaction->t_tid;
 998         stats.run.rs_handle_count = commit_transaction->t_handle_count;
 999         trace_jbd2_run_stats(journal->j_fs_dev->bd_dev,
1000                              commit_transaction->t_tid, &stats.run);
1001
1002         /*
1003          * Calculate overall stats
1004          */
1005         spin_lock(&journal->j_history_lock);
1006         journal->j_stats.ts_tid++;
1007         journal->j_stats.run.rs_wait += stats.run.rs_wait;
1008         journal->j_stats.run.rs_running += stats.run.rs_running;
1009         journal->j_stats.run.rs_locked += stats.run.rs_locked;
1010         journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
1011         journal->j_stats.run.rs_logging += stats.run.rs_logging;
1012         journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
1013         journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
1014         journal->j_stats.run.rs_blocks_logged += stats.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 }