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/smp_lock.h>
  24
  25 /*
  26  * Default IO end handler for temporary BJ_IO buffer_heads.
  27  */
  28 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
  29 {
  30         BUFFER_TRACE(bh, "");
  31         if (uptodate)
  32                 set_buffer_uptodate(bh);
  33         else
  34                 clear_buffer_uptodate(bh);
  35         unlock_buffer(bh);
  36 }
  37
  38 /*
  39  * When an ext3-ordered file is truncated, it is possible that many pages are
  40  * not sucessfully freed, because they are attached to a committing transaction.
  41  * After the transaction commits, these pages are left on the LRU, with no
  42  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
  43  * by the VM, but their apparent absence upsets the VM accounting, and it makes
  44  * the numbers in /proc/meminfo look odd.
  45  *
  46  * So here, we have a buffer which has just come off the forget list.  Look to
  47  * see if we can strip all buffers from the backing page.
  48  *
  49  * Called under lock_journal(), and possibly under journal_datalist_lock.  The
  50  * caller provided us with a ref against the buffer, and we drop that here.
  51  */
  52 static void release_buffer_page(struct buffer_head *bh)
  53 {
  54         struct page *page;
  55
  56         if (buffer_dirty(bh))
  57                 goto nope;
  58         if (atomic_read(&bh->b_count) != 1)
  59                 goto nope;
  60         page = bh->b_page;
  61         if (!page)
  62                 goto nope;
  63         if (page->mapping)
  64                 goto nope;
  65
  66         /* OK, it's a truncated page */
  67         if (TestSetPageLocked(page))
  68                 goto nope;
  69
  70         page_cache_get(page);
  71         __brelse(bh);
  72         try_to_free_buffers(page);
  73         unlock_page(page);
  74         page_cache_release(page);
  75         return;
  76
  77 nope:
  78         __brelse(bh);
  79 }
  80
  81 /*
  82  * Try to acquire jbd_lock_bh_state() against the buffer, when j_list_lock is
  83  * held.  For ranking reasons we must trylock.  If we lose, schedule away and
  84  * return 0.  j_list_lock is dropped in this case.
  85  */
  86 static int inverted_lock(journal_t *journal, struct buffer_head *bh)
  87 {
  88         if (!jbd_trylock_bh_state(bh)) {
  89                 spin_unlock(&journal->j_list_lock);
  90                 schedule();
  91                 return 0;
  92         }
  93         return 1;
  94 }
  95
  96 /* Done it all: now write the commit record.  We should have
  97  * cleaned up our previous buffers by now, so if we are in abort
  98  * mode we can now just skip the rest of the journal write
  99  * entirely.
 100  *
 101  * Returns 1 if the journal needs to be aborted or 0 on success
 102  */
 103 static int journal_write_commit_record(journal_t *journal,
 104                                         transaction_t *commit_transaction)
 105 {
 106         struct journal_head *descriptor;
 107         struct buffer_head *bh;
 108         int i, ret;
 109         int barrier_done = 0;
 110
 111         if (is_journal_aborted(journal))
 112                 return 0;
 113
 114         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 115         if (!descriptor)
 116                 return 1;
 117
 118         bh = jh2bh(descriptor);
 119
 120         /* AKPM: buglet - add `i' to tmp! */
 121         for (i = 0; i < bh->b_size; i += 512) {
 122                 journal_header_t *tmp = (journal_header_t*)bh->b_data;
 123                 tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
 124                 tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
 125                 tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 126         }
 127
 128         JBUFFER_TRACE(descriptor, "write commit block");
 129         set_buffer_dirty(bh);
 130         if (journal->j_flags & JBD2_BARRIER) {
 131                 set_buffer_ordered(bh);
 132                 barrier_done = 1;
 133         }
 134         ret = sync_dirty_buffer(bh);
 135         /* is it possible for another commit to fail at roughly
 136          * the same time as this one?  If so, we don't want to
 137          * trust the barrier flag in the super, but instead want
 138          * to remember if we sent a barrier request
 139          */
 140         if (ret == -EOPNOTSUPP && barrier_done) {
 141                 char b[BDEVNAME_SIZE];
 142
 143                 printk(KERN_WARNING
 144                         "JBD: barrier-based sync failed on %s - "
 145                         "disabling barriers\n",
 146                         bdevname(journal->j_dev, b));
 147                 spin_lock(&journal->j_state_lock);
 148                 journal->j_flags &= ~JBD2_BARRIER;
 149                 spin_unlock(&journal->j_state_lock);
 150
 151                 /* And try again, without the barrier */
 152                 clear_buffer_ordered(bh);
 153                 set_buffer_uptodate(bh);
 154                 set_buffer_dirty(bh);
 155                 ret = sync_dirty_buffer(bh);
 156         }
 157         put_bh(bh);             /* One for getblk() */
 158         jbd2_journal_put_journal_head(descriptor);
 159
 160         return (ret == -EIO);
 161 }
 162
 163 static void journal_do_submit_data(struct buffer_head **wbuf, int bufs)
 164 {
 165         int i;
 166
 167         for (i = 0; i < bufs; i++) {
 168                 wbuf[i]->b_end_io = end_buffer_write_sync;
 169                 /* We use-up our safety reference in submit_bh() */
 170                 submit_bh(WRITE, wbuf[i]);
 171         }
 172 }
 173
 174 /*
 175  *  Submit all the data buffers to disk
 176  */
 177 static void journal_submit_data_buffers(journal_t *journal,
 178                                 transaction_t *commit_transaction)
 179 {
 180         struct journal_head *jh;
 181         struct buffer_head *bh;
 182         int locked;
 183         int bufs = 0;
 184         struct buffer_head **wbuf = journal->j_wbuf;
 185
 186         /*
 187          * Whenever we unlock the journal and sleep, things can get added
 188          * onto ->t_sync_datalist, so we have to keep looping back to
 189          * write_out_data until we *know* that the list is empty.
 190          *
 191          * Cleanup any flushed data buffers from the data list.  Even in
 192          * abort mode, we want to flush this out as soon as possible.
 193          */
 194 write_out_data:
 195         cond_resched();
 196         spin_lock(&journal->j_list_lock);
 197
 198         while (commit_transaction->t_sync_datalist) {
 199                 jh = commit_transaction->t_sync_datalist;
 200                 bh = jh2bh(jh);
 201                 locked = 0;
 202
 203                 /* Get reference just to make sure buffer does not disappear
 204                  * when we are forced to drop various locks */
 205                 get_bh(bh);
 206                 /* If the buffer is dirty, we need to submit IO and hence
 207                  * we need the buffer lock. We try to lock the buffer without
 208                  * blocking. If we fail, we need to drop j_list_lock and do
 209                  * blocking lock_buffer().
 210                  */
 211                 if (buffer_dirty(bh)) {
 212                         if (test_set_buffer_locked(bh)) {
 213                                 BUFFER_TRACE(bh, "needs blocking lock");
 214                                 spin_unlock(&journal->j_list_lock);
 215                                 /* Write out all data to prevent deadlocks */
 216                                 journal_do_submit_data(wbuf, bufs);
 217                                 bufs = 0;
 218                                 lock_buffer(bh);
 219                                 spin_lock(&journal->j_list_lock);
 220                         }
 221                         locked = 1;
 222                 }
 223                 /* We have to get bh_state lock. Again out of order, sigh. */
 224                 if (!inverted_lock(journal, bh)) {
 225                         jbd_lock_bh_state(bh);
 226                         spin_lock(&journal->j_list_lock);
 227                 }
 228                 /* Someone already cleaned up the buffer? */
 229                 if (!buffer_jbd(bh)
 230                         || jh->b_transaction != commit_transaction
 231                         || jh->b_jlist != BJ_SyncData) {
 232                         jbd_unlock_bh_state(bh);
 233                         if (locked)
 234                                 unlock_buffer(bh);
 235                         BUFFER_TRACE(bh, "already cleaned up");
 236                         put_bh(bh);
 237                         continue;
 238                 }
 239                 if (locked && test_clear_buffer_dirty(bh)) {
 240                         BUFFER_TRACE(bh, "needs writeout, adding to array");
 241                         wbuf[bufs++] = bh;
 242                         __jbd2_journal_file_buffer(jh, commit_transaction,
 243                                                 BJ_Locked);
 244                         jbd_unlock_bh_state(bh);
 245                         if (bufs == journal->j_wbufsize) {
 246                                 spin_unlock(&journal->j_list_lock);
 247                                 journal_do_submit_data(wbuf, bufs);
 248                                 bufs = 0;
 249                                 goto write_out_data;
 250                         }
 251                 } else if (!locked && buffer_locked(bh)) {
 252                         __jbd2_journal_file_buffer(jh, commit_transaction,
 253                                                 BJ_Locked);
 254                         jbd_unlock_bh_state(bh);
 255                         put_bh(bh);
 256                 } else {
 257                         BUFFER_TRACE(bh, "writeout complete: unfile");
 258                         __jbd2_journal_unfile_buffer(jh);
 259                         jbd_unlock_bh_state(bh);
 260                         if (locked)
 261                                 unlock_buffer(bh);
 262                         jbd2_journal_remove_journal_head(bh);
 263                         /* Once for our safety reference, once for
 264                          * jbd2_journal_remove_journal_head() */
 265                         put_bh(bh);
 266                         put_bh(bh);
 267                 }
 268
 269                 if (lock_need_resched(&journal->j_list_lock)) {
 270                         spin_unlock(&journal->j_list_lock);
 271                         goto write_out_data;
 272                 }
 273         }
 274         spin_unlock(&journal->j_list_lock);
 275         journal_do_submit_data(wbuf, bufs);
 276 }
 277
 278 static inline void write_tag_block(int tag_bytes, journal_block_tag_t *tag,
 279                                    unsigned long long block)
 280 {
 281         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
 282         if (tag_bytes > JBD_TAG_SIZE32)
 283                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
 284 }
 285
 286 /*
 287  * jbd2_journal_commit_transaction
 288  *
 289  * The primary function for committing a transaction to the log.  This
 290  * function is called by the journal thread to begin a complete commit.
 291  */
 292 void jbd2_journal_commit_transaction(journal_t *journal)
 293 {
 294         transaction_t *commit_transaction;
 295         struct journal_head *jh, *new_jh, *descriptor;
 296         struct buffer_head **wbuf = journal->j_wbuf;
 297         int bufs;
 298         int flags;
 299         int err;
 300         unsigned long long blocknr;
 301         char *tagp = NULL;
 302         journal_header_t *header;
 303         journal_block_tag_t *tag = NULL;
 304         int space_left = 0;
 305         int first_tag = 0;
 306         int tag_flag;
 307         int i;
 308         int tag_bytes = journal_tag_bytes(journal);
 309
 310         /*
 311          * First job: lock down the current transaction and wait for
 312          * all outstanding updates to complete.
 313          */
 314
 315 #ifdef COMMIT_STATS
 316         spin_lock(&journal->j_list_lock);
 317         summarise_journal_usage(journal);
 318         spin_unlock(&journal->j_list_lock);
 319 #endif
 320
 321         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 322         if (journal->j_flags & JBD2_FLUSHED) {
 323                 jbd_debug(3, "super block updated\n");
 324                 jbd2_journal_update_superblock(journal, 1);
 325         } else {
 326                 jbd_debug(3, "superblock not updated\n");
 327         }
 328
 329         J_ASSERT(journal->j_running_transaction != NULL);
 330         J_ASSERT(journal->j_committing_transaction == NULL);
 331
 332         commit_transaction = journal->j_running_transaction;
 333         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 334
 335         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 336                         commit_transaction->t_tid);
 337
 338         spin_lock(&journal->j_state_lock);
 339         commit_transaction->t_state = T_LOCKED;
 340
 341         spin_lock(&commit_transaction->t_handle_lock);
 342         while (commit_transaction->t_updates) {
 343                 DEFINE_WAIT(wait);
 344
 345                 prepare_to_wait(&journal->j_wait_updates, &wait,
 346                                         TASK_UNINTERRUPTIBLE);
 347                 if (commit_transaction->t_updates) {
 348                         spin_unlock(&commit_transaction->t_handle_lock);
 349                         spin_unlock(&journal->j_state_lock);
 350                         schedule();
 351                         spin_lock(&journal->j_state_lock);
 352                         spin_lock(&commit_transaction->t_handle_lock);
 353                 }
 354                 finish_wait(&journal->j_wait_updates, &wait);
 355         }
 356         spin_unlock(&commit_transaction->t_handle_lock);
 357
 358         J_ASSERT (commit_transaction->t_outstanding_credits <=
 359                         journal->j_max_transaction_buffers);
 360
 361         /*
 362          * First thing we are allowed to do is to discard any remaining
 363          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 364          * that there are no such buffers: if a large filesystem
 365          * operation like a truncate needs to split itself over multiple
 366          * transactions, then it may try to do a jbd2_journal_restart() while
 367          * there are still BJ_Reserved buffers outstanding.  These must
 368          * be released cleanly from the current transaction.
 369          *
 370          * In this case, the filesystem must still reserve write access
 371          * again before modifying the buffer in the new transaction, but
 372          * we do not require it to remember exactly which old buffers it
 373          * has reserved.  This is consistent with the existing behaviour
 374          * that multiple jbd2_journal_get_write_access() calls to the same
 375          * buffer are perfectly permissable.
 376          */
 377         while (commit_transaction->t_reserved_list) {
 378                 jh = commit_transaction->t_reserved_list;
 379                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 380                 /*
 381                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 382                  * leave undo-committed data.
 383                  */
 384                 if (jh->b_committed_data) {
 385                         struct buffer_head *bh = jh2bh(jh);
 386
 387                         jbd_lock_bh_state(bh);
 388                         jbd2_slab_free(jh->b_committed_data, bh->b_size);
 389                         jh->b_committed_data = NULL;
 390                         jbd_unlock_bh_state(bh);
 391                 }
 392                 jbd2_journal_refile_buffer(journal, jh);
 393         }
 394
 395         /*
 396          * Now try to drop any written-back buffers from the journal's
 397          * checkpoint lists.  We do this *before* commit because it potentially
 398          * frees some memory
 399          */
 400         spin_lock(&journal->j_list_lock);
 401         __jbd2_journal_clean_checkpoint_list(journal);
 402         spin_unlock(&journal->j_list_lock);
 403
 404         jbd_debug (3, "JBD: commit phase 1\n");
 405
 406         /*
 407          * Switch to a new revoke table.
 408          */
 409         jbd2_journal_switch_revoke_table(journal);
 410
 411         commit_transaction->t_state = T_FLUSH;
 412         journal->j_committing_transaction = commit_transaction;
 413         journal->j_running_transaction = NULL;
 414         commit_transaction->t_log_start = journal->j_head;
 415         wake_up(&journal->j_wait_transaction_locked);
 416         spin_unlock(&journal->j_state_lock);
 417
 418         jbd_debug (3, "JBD: commit phase 2\n");
 419
 420         /*
 421          * First, drop modified flag: all accesses to the buffers
 422          * will be tracked for a new trasaction only -bzzz
 423          */
 424         spin_lock(&journal->j_list_lock);
 425         if (commit_transaction->t_buffers) {
 426                 new_jh = jh = commit_transaction->t_buffers->b_tnext;
 427                 do {
 428                         J_ASSERT_JH(new_jh, new_jh->b_modified == 1 ||
 429                                         new_jh->b_modified == 0);
 430                         new_jh->b_modified = 0;
 431                         new_jh = new_jh->b_tnext;
 432                 } while (new_jh != jh);
 433         }
 434         spin_unlock(&journal->j_list_lock);
 435
 436         /*
 437          * Now start flushing things to disk, in the order they appear
 438          * on the transaction lists.  Data blocks go first.
 439          */
 440         err = 0;
 441         journal_submit_data_buffers(journal, commit_transaction);
 442
 443         /*
 444          * Wait for all previously submitted IO to complete.
 445          */
 446         spin_lock(&journal->j_list_lock);
 447         while (commit_transaction->t_locked_list) {
 448                 struct buffer_head *bh;
 449
 450                 jh = commit_transaction->t_locked_list->b_tprev;
 451                 bh = jh2bh(jh);
 452                 get_bh(bh);
 453                 if (buffer_locked(bh)) {
 454                         spin_unlock(&journal->j_list_lock);
 455                         wait_on_buffer(bh);
 456                         if (unlikely(!buffer_uptodate(bh)))
 457                                 err = -EIO;
 458                         spin_lock(&journal->j_list_lock);
 459                 }
 460                 if (!inverted_lock(journal, bh)) {
 461                         put_bh(bh);
 462                         spin_lock(&journal->j_list_lock);
 463                         continue;
 464                 }
 465                 if (buffer_jbd(bh) && jh->b_jlist == BJ_Locked) {
 466                         __jbd2_journal_unfile_buffer(jh);
 467                         jbd_unlock_bh_state(bh);
 468                         jbd2_journal_remove_journal_head(bh);
 469                         put_bh(bh);
 470                 } else {
 471                         jbd_unlock_bh_state(bh);
 472                 }
 473                 put_bh(bh);
 474                 cond_resched_lock(&journal->j_list_lock);
 475         }
 476         spin_unlock(&journal->j_list_lock);
 477
 478         if (err)
 479                 __jbd2_journal_abort_hard(journal);
 480
 481         jbd2_journal_write_revoke_records(journal, commit_transaction);
 482
 483         jbd_debug(3, "JBD: commit phase 2\n");
 484
 485         /*
 486          * If we found any dirty or locked buffers, then we should have
 487          * looped back up to the write_out_data label.  If there weren't
 488          * any then journal_clean_data_list should have wiped the list
 489          * clean by now, so check that it is in fact empty.
 490          */
 491         J_ASSERT (commit_transaction->t_sync_datalist == NULL);
 492
 493         jbd_debug (3, "JBD: commit phase 3\n");
 494
 495         /*
 496          * Way to go: we have now written out all of the data for a
 497          * transaction!  Now comes the tricky part: we need to write out
 498          * metadata.  Loop over the transaction's entire buffer list:
 499          */
 500         commit_transaction->t_state = T_COMMIT;
 501
 502         descriptor = NULL;
 503         bufs = 0;
 504         while (commit_transaction->t_buffers) {
 505
 506                 /* Find the next buffer to be journaled... */
 507
 508                 jh = commit_transaction->t_buffers;
 509
 510                 /* If we're in abort mode, we just un-journal the buffer and
 511                    release it for background writing. */
 512
 513                 if (is_journal_aborted(journal)) {
 514                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 515                         jbd2_journal_refile_buffer(journal, jh);
 516                         /* If that was the last one, we need to clean up
 517                          * any descriptor buffers which may have been
 518                          * already allocated, even if we are now
 519                          * aborting. */
 520                         if (!commit_transaction->t_buffers)
 521                                 goto start_journal_io;
 522                         continue;
 523                 }
 524
 525                 /* Make sure we have a descriptor block in which to
 526                    record the metadata buffer. */
 527
 528                 if (!descriptor) {
 529                         struct buffer_head *bh;
 530
 531                         J_ASSERT (bufs == 0);
 532
 533                         jbd_debug(4, "JBD: get descriptor\n");
 534
 535                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 536                         if (!descriptor) {
 537                                 __jbd2_journal_abort_hard(journal);
 538                                 continue;
 539                         }
 540
 541                         bh = jh2bh(descriptor);
 542                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 543                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 544                         header = (journal_header_t *)&bh->b_data[0];
 545                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 546                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 547                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 548
 549                         tagp = &bh->b_data[sizeof(journal_header_t)];
 550                         space_left = bh->b_size - sizeof(journal_header_t);
 551                         first_tag = 1;
 552                         set_buffer_jwrite(bh);
 553                         set_buffer_dirty(bh);
 554                         wbuf[bufs++] = bh;
 555
 556                         /* Record it so that we can wait for IO
 557                            completion later */
 558                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 559                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 560                                         BJ_LogCtl);
 561                 }
 562
 563                 /* Where is the buffer to be written? */
 564
 565                 err = jbd2_journal_next_log_block(journal, &blocknr);
 566                 /* If the block mapping failed, just abandon the buffer
 567                    and repeat this loop: we'll fall into the
 568                    refile-on-abort condition above. */
 569                 if (err) {
 570                         __jbd2_journal_abort_hard(journal);
 571                         continue;
 572                 }
 573
 574                 /*
 575                  * start_this_handle() uses t_outstanding_credits to determine
 576                  * the free space in the log, but this counter is changed
 577                  * by jbd2_journal_next_log_block() also.
 578                  */
 579                 commit_transaction->t_outstanding_credits--;
 580
 581                 /* Bump b_count to prevent truncate from stumbling over
 582                    the shadowed buffer!  @@@ This can go if we ever get
 583                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 584                 atomic_inc(&jh2bh(jh)->b_count);
 585
 586                 /* Make a temporary IO buffer with which to write it out
 587                    (this will requeue both the metadata buffer and the
 588                    temporary IO buffer). new_bh goes on BJ_IO*/
 589
 590                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 591                 /*
 592                  * akpm: jbd2_journal_write_metadata_buffer() sets
 593                  * new_bh->b_transaction to commit_transaction.
 594                  * We need to clean this up before we release new_bh
 595                  * (which is of type BJ_IO)
 596                  */
 597                 JBUFFER_TRACE(jh, "ph3: write metadata");
 598                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 599                                                       jh, &new_jh, blocknr);
 600                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 601                 wbuf[bufs++] = jh2bh(new_jh);
 602
 603                 /* Record the new block's tag in the current descriptor
 604                    buffer */
 605
 606                 tag_flag = 0;
 607                 if (flags & 1)
 608                         tag_flag |= JBD2_FLAG_ESCAPE;
 609                 if (!first_tag)
 610                         tag_flag |= JBD2_FLAG_SAME_UUID;
 611
 612                 tag = (journal_block_tag_t *) tagp;
 613                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 614                 tag->t_flags = cpu_to_be32(tag_flag);
 615                 tagp += tag_bytes;
 616                 space_left -= tag_bytes;
 617
 618                 if (first_tag) {
 619                         memcpy (tagp, journal->j_uuid, 16);
 620                         tagp += 16;
 621                         space_left -= 16;
 622                         first_tag = 0;
 623                 }
 624
 625                 /* If there's no more to do, or if the descriptor is full,
 626                    let the IO rip! */
 627
 628                 if (bufs == journal->j_wbufsize ||
 629                     commit_transaction->t_buffers == NULL ||
 630                     space_left < tag_bytes + 16) {
 631
 632                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 633
 634                         /* Write an end-of-descriptor marker before
 635                            submitting the IOs.  "tag" still points to
 636                            the last tag we set up. */
 637
 638                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 639
 640 start_journal_io:
 641                         for (i = 0; i < bufs; i++) {
 642                                 struct buffer_head *bh = wbuf[i];
 643                                 lock_buffer(bh);
 644                                 clear_buffer_dirty(bh);
 645                                 set_buffer_uptodate(bh);
 646                                 bh->b_end_io = journal_end_buffer_io_sync;
 647                                 submit_bh(WRITE, bh);
 648                         }
 649                         cond_resched();
 650
 651                         /* Force a new descriptor to be generated next
 652                            time round the loop. */
 653                         descriptor = NULL;
 654                         bufs = 0;
 655                 }
 656         }
 657
 658         /* Lo and behold: we have just managed to send a transaction to
 659            the log.  Before we can commit it, wait for the IO so far to
 660            complete.  Control buffers being written are on the
 661            transaction's t_log_list queue, and metadata buffers are on
 662            the t_iobuf_list queue.
 663
 664            Wait for the buffers in reverse order.  That way we are
 665            less likely to be woken up until all IOs have completed, and
 666            so we incur less scheduling load.
 667         */
 668
 669         jbd_debug(3, "JBD: commit phase 4\n");
 670
 671         /*
 672          * akpm: these are BJ_IO, and j_list_lock is not needed.
 673          * See __journal_try_to_free_buffer.
 674          */
 675 wait_for_iobuf:
 676         while (commit_transaction->t_iobuf_list != NULL) {
 677                 struct buffer_head *bh;
 678
 679                 jh = commit_transaction->t_iobuf_list->b_tprev;
 680                 bh = jh2bh(jh);
 681                 if (buffer_locked(bh)) {
 682                         wait_on_buffer(bh);
 683                         goto wait_for_iobuf;
 684                 }
 685                 if (cond_resched())
 686                         goto wait_for_iobuf;
 687
 688                 if (unlikely(!buffer_uptodate(bh)))
 689                         err = -EIO;
 690
 691                 clear_buffer_jwrite(bh);
 692
 693                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 694                 jbd2_journal_unfile_buffer(journal, jh);
 695
 696                 /*
 697                  * ->t_iobuf_list should contain only dummy buffer_heads
 698                  * which were created by jbd2_journal_write_metadata_buffer().
 699                  */
 700                 BUFFER_TRACE(bh, "dumping temporary bh");
 701                 jbd2_journal_put_journal_head(jh);
 702                 __brelse(bh);
 703                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 704                 free_buffer_head(bh);
 705
 706                 /* We also have to unlock and free the corresponding
 707                    shadowed buffer */
 708                 jh = commit_transaction->t_shadow_list->b_tprev;
 709                 bh = jh2bh(jh);
 710                 clear_bit(BH_JWrite, &bh->b_state);
 711                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 712
 713                 /* The metadata is now released for reuse, but we need
 714                    to remember it against this transaction so that when
 715                    we finally commit, we can do any checkpointing
 716                    required. */
 717                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 718                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 719                 /* Wake up any transactions which were waiting for this
 720                    IO to complete */
 721                 wake_up_bit(&bh->b_state, BH_Unshadow);
 722                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 723                 __brelse(bh);
 724         }
 725
 726         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 727
 728         jbd_debug(3, "JBD: commit phase 5\n");
 729
 730         /* Here we wait for the revoke record and descriptor record buffers */
 731  wait_for_ctlbuf:
 732         while (commit_transaction->t_log_list != NULL) {
 733                 struct buffer_head *bh;
 734
 735                 jh = commit_transaction->t_log_list->b_tprev;
 736                 bh = jh2bh(jh);
 737                 if (buffer_locked(bh)) {
 738                         wait_on_buffer(bh);
 739                         goto wait_for_ctlbuf;
 740                 }
 741                 if (cond_resched())
 742                         goto wait_for_ctlbuf;
 743
 744                 if (unlikely(!buffer_uptodate(bh)))
 745                         err = -EIO;
 746
 747                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 748                 clear_buffer_jwrite(bh);
 749                 jbd2_journal_unfile_buffer(journal, jh);
 750                 jbd2_journal_put_journal_head(jh);
 751                 __brelse(bh);           /* One for getblk */
 752                 /* AKPM: bforget here */
 753         }
 754
 755         jbd_debug(3, "JBD: commit phase 6\n");
 756
 757         if (journal_write_commit_record(journal, commit_transaction))
 758                 err = -EIO;
 759
 760         if (err)
 761                 __jbd2_journal_abort_hard(journal);
 762
 763         /* End of a transaction!  Finally, we can do checkpoint
 764            processing: any buffers committed as a result of this
 765            transaction can be removed from any checkpoint list it was on
 766            before. */
 767
 768         jbd_debug(3, "JBD: commit phase 7\n");
 769
 770         J_ASSERT(commit_transaction->t_sync_datalist == NULL);
 771         J_ASSERT(commit_transaction->t_buffers == NULL);
 772         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 773         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 774         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 775         J_ASSERT(commit_transaction->t_log_list == NULL);
 776
 777 restart_loop:
 778         /*
 779          * As there are other places (journal_unmap_buffer()) adding buffers
 780          * to this list we have to be careful and hold the j_list_lock.
 781          */
 782         spin_lock(&journal->j_list_lock);
 783         while (commit_transaction->t_forget) {
 784                 transaction_t *cp_transaction;
 785                 struct buffer_head *bh;
 786
 787                 jh = commit_transaction->t_forget;
 788                 spin_unlock(&journal->j_list_lock);
 789                 bh = jh2bh(jh);
 790                 jbd_lock_bh_state(bh);
 791                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
 792                         jh->b_transaction == journal->j_running_transaction);
 793
 794                 /*
 795                  * If there is undo-protected committed data against
 796                  * this buffer, then we can remove it now.  If it is a
 797                  * buffer needing such protection, the old frozen_data
 798                  * field now points to a committed version of the
 799                  * buffer, so rotate that field to the new committed
 800                  * data.
 801                  *
 802                  * Otherwise, we can just throw away the frozen data now.
 803                  */
 804                 if (jh->b_committed_data) {
 805                         jbd2_slab_free(jh->b_committed_data, bh->b_size);
 806                         jh->b_committed_data = NULL;
 807                         if (jh->b_frozen_data) {
 808                                 jh->b_committed_data = jh->b_frozen_data;
 809                                 jh->b_frozen_data = NULL;
 810                         }
 811                 } else if (jh->b_frozen_data) {
 812                         jbd2_slab_free(jh->b_frozen_data, bh->b_size);
 813                         jh->b_frozen_data = NULL;
 814                 }
 815
 816                 spin_lock(&journal->j_list_lock);
 817                 cp_transaction = jh->b_cp_transaction;
 818                 if (cp_transaction) {
 819                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 820                         __jbd2_journal_remove_checkpoint(jh);
 821                 }
 822
 823                 /* Only re-checkpoint the buffer_head if it is marked
 824                  * dirty.  If the buffer was added to the BJ_Forget list
 825                  * by jbd2_journal_forget, it may no longer be dirty and
 826                  * there's no point in keeping a checkpoint record for
 827                  * it. */
 828
 829                 /* A buffer which has been freed while still being
 830                  * journaled by a previous transaction may end up still
 831                  * being dirty here, but we want to avoid writing back
 832                  * that buffer in the future now that the last use has
 833                  * been committed.  That's not only a performance gain,
 834                  * it also stops aliasing problems if the buffer is left
 835                  * behind for writeback and gets reallocated for another
 836                  * use in a different page. */
 837                 if (buffer_freed(bh)) {
 838                         clear_buffer_freed(bh);
 839                         clear_buffer_jbddirty(bh);
 840                 }
 841
 842                 if (buffer_jbddirty(bh)) {
 843                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 844                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 845                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 846                         __jbd2_journal_refile_buffer(jh);
 847                         jbd_unlock_bh_state(bh);
 848                 } else {
 849                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 850                         /* The buffer on BJ_Forget list and not jbddirty means
 851                          * it has been freed by this transaction and hence it
 852                          * could not have been reallocated until this
 853                          * transaction has committed. *BUT* it could be
 854                          * reallocated once we have written all the data to
 855                          * disk and before we process the buffer on BJ_Forget
 856                          * list. */
 857                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 858                         __jbd2_journal_refile_buffer(jh);
 859                         if (!jh->b_transaction) {
 860                                 jbd_unlock_bh_state(bh);
 861                                  /* needs a brelse */
 862                                 jbd2_journal_remove_journal_head(bh);
 863                                 release_buffer_page(bh);
 864                         } else
 865                                 jbd_unlock_bh_state(bh);
 866                 }
 867                 cond_resched_lock(&journal->j_list_lock);
 868         }
 869         spin_unlock(&journal->j_list_lock);
 870         /*
 871          * This is a bit sleazy.  We borrow j_list_lock to protect
 872          * journal->j_committing_transaction in __jbd2_journal_remove_checkpoint.
 873          * Really, __jbd2_journal_remove_checkpoint should be using j_state_lock but
 874          * it's a bit hassle to hold that across __jbd2_journal_remove_checkpoint
 875          */
 876         spin_lock(&journal->j_state_lock);
 877         spin_lock(&journal->j_list_lock);
 878         /*
 879          * Now recheck if some buffers did not get attached to the transaction
 880          * while the lock was dropped...
 881          */
 882         if (commit_transaction->t_forget) {
 883                 spin_unlock(&journal->j_list_lock);
 884                 spin_unlock(&journal->j_state_lock);
 885                 goto restart_loop;
 886         }
 887
 888         /* Done with this transaction! */
 889
 890         jbd_debug(3, "JBD: commit phase 8\n");
 891
 892         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 893
 894         commit_transaction->t_state = T_FINISHED;
 895         J_ASSERT(commit_transaction == journal->j_committing_transaction);
 896         journal->j_commit_sequence = commit_transaction->t_tid;
 897         journal->j_committing_transaction = NULL;
 898         spin_unlock(&journal->j_state_lock);
 899
 900         if (commit_transaction->t_checkpoint_list == NULL) {
 901                 __jbd2_journal_drop_transaction(journal, commit_transaction);
 902         } else {
 903                 if (journal->j_checkpoint_transactions == NULL) {
 904                         journal->j_checkpoint_transactions = commit_transaction;
 905                         commit_transaction->t_cpnext = commit_transaction;
 906                         commit_transaction->t_cpprev = commit_transaction;
 907                 } else {
 908                         commit_transaction->t_cpnext =
 909                                 journal->j_checkpoint_transactions;
 910                         commit_transaction->t_cpprev =
 911                                 commit_transaction->t_cpnext->t_cpprev;
 912                         commit_transaction->t_cpnext->t_cpprev =
 913                                 commit_transaction;
 914                         commit_transaction->t_cpprev->t_cpnext =
 915                                 commit_transaction;
 916                 }
 917         }
 918         spin_unlock(&journal->j_list_lock);
 919
 920         jbd_debug(1, "JBD: commit %d complete, head %d\n",
 921                   journal->j_commit_sequence, journal->j_tail_sequence);
 922
 923         wake_up(&journal->j_wait_done_commit);
 924 }