linux/fs/jbd/transaction.c
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   1/*
   2 * linux/fs/jbd/transaction.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 * Generic filesystem transaction handling code; part of the ext2fs
  13 * journaling system.
  14 *
  15 * This file manages transactions (compound commits managed by the
  16 * journaling code) and handles (individual atomic operations by the
  17 * filesystem).
  18 */
  19
  20#include <linux/time.h>
  21#include <linux/fs.h>
  22#include <linux/jbd.h>
  23#include <linux/errno.h>
  24#include <linux/slab.h>
  25#include <linux/timer.h>
  26#include <linux/mm.h>
  27#include <linux/highmem.h>
  28#include <linux/hrtimer.h>
  29
  30static void __journal_temp_unlink_buffer(struct journal_head *jh);
  31
  32/*
  33 * get_transaction: obtain a new transaction_t object.
  34 *
  35 * Simply allocate and initialise a new transaction.  Create it in
  36 * RUNNING state and add it to the current journal (which should not
  37 * have an existing running transaction: we only make a new transaction
  38 * once we have started to commit the old one).
  39 *
  40 * Preconditions:
  41 *      The journal MUST be locked.  We don't perform atomic mallocs on the
  42 *      new transaction and we can't block without protecting against other
  43 *      processes trying to touch the journal while it is in transition.
  44 *
  45 * Called under j_state_lock
  46 */
  47
  48static transaction_t *
  49get_transaction(journal_t *journal, transaction_t *transaction)
  50{
  51        transaction->t_journal = journal;
  52        transaction->t_state = T_RUNNING;
  53        transaction->t_start_time = ktime_get();
  54        transaction->t_tid = journal->j_transaction_sequence++;
  55        transaction->t_expires = jiffies + journal->j_commit_interval;
  56        spin_lock_init(&transaction->t_handle_lock);
  57
  58        /* Set up the commit timer for the new transaction. */
  59        journal->j_commit_timer.expires =
  60                                round_jiffies_up(transaction->t_expires);
  61        add_timer(&journal->j_commit_timer);
  62
  63        J_ASSERT(journal->j_running_transaction == NULL);
  64        journal->j_running_transaction = transaction;
  65
  66        return transaction;
  67}
  68
  69/*
  70 * Handle management.
  71 *
  72 * A handle_t is an object which represents a single atomic update to a
  73 * filesystem, and which tracks all of the modifications which form part
  74 * of that one update.
  75 */
  76
  77/*
  78 * start_this_handle: Given a handle, deal with any locking or stalling
  79 * needed to make sure that there is enough journal space for the handle
  80 * to begin.  Attach the handle to a transaction and set up the
  81 * transaction's buffer credits.
  82 */
  83
  84static int start_this_handle(journal_t *journal, handle_t *handle)
  85{
  86        transaction_t *transaction;
  87        int needed;
  88        int nblocks = handle->h_buffer_credits;
  89        transaction_t *new_transaction = NULL;
  90        int ret = 0;
  91
  92        if (nblocks > journal->j_max_transaction_buffers) {
  93                printk(KERN_ERR "JBD: %s wants too many credits (%d > %d)\n",
  94                       current->comm, nblocks,
  95                       journal->j_max_transaction_buffers);
  96                ret = -ENOSPC;
  97                goto out;
  98        }
  99
 100alloc_transaction:
 101        if (!journal->j_running_transaction) {
 102                new_transaction = kzalloc(sizeof(*new_transaction),
 103                                                GFP_NOFS|__GFP_NOFAIL);
 104                if (!new_transaction) {
 105                        ret = -ENOMEM;
 106                        goto out;
 107                }
 108        }
 109
 110        jbd_debug(3, "New handle %p going live.\n", handle);
 111
 112repeat:
 113
 114        /*
 115         * We need to hold j_state_lock until t_updates has been incremented,
 116         * for proper journal barrier handling
 117         */
 118        spin_lock(&journal->j_state_lock);
 119repeat_locked:
 120        if (is_journal_aborted(journal) ||
 121            (journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) {
 122                spin_unlock(&journal->j_state_lock);
 123                ret = -EROFS;
 124                goto out;
 125        }
 126
 127        /* Wait on the journal's transaction barrier if necessary */
 128        if (journal->j_barrier_count) {
 129                spin_unlock(&journal->j_state_lock);
 130                wait_event(journal->j_wait_transaction_locked,
 131                                journal->j_barrier_count == 0);
 132                goto repeat;
 133        }
 134
 135        if (!journal->j_running_transaction) {
 136                if (!new_transaction) {
 137                        spin_unlock(&journal->j_state_lock);
 138                        goto alloc_transaction;
 139                }
 140                get_transaction(journal, new_transaction);
 141                new_transaction = NULL;
 142        }
 143
 144        transaction = journal->j_running_transaction;
 145
 146        /*
 147         * If the current transaction is locked down for commit, wait for the
 148         * lock to be released.
 149         */
 150        if (transaction->t_state == T_LOCKED) {
 151                DEFINE_WAIT(wait);
 152
 153                prepare_to_wait(&journal->j_wait_transaction_locked,
 154                                        &wait, TASK_UNINTERRUPTIBLE);
 155                spin_unlock(&journal->j_state_lock);
 156                schedule();
 157                finish_wait(&journal->j_wait_transaction_locked, &wait);
 158                goto repeat;
 159        }
 160
 161        /*
 162         * If there is not enough space left in the log to write all potential
 163         * buffers requested by this operation, we need to stall pending a log
 164         * checkpoint to free some more log space.
 165         */
 166        spin_lock(&transaction->t_handle_lock);
 167        needed = transaction->t_outstanding_credits + nblocks;
 168
 169        if (needed > journal->j_max_transaction_buffers) {
 170                /*
 171                 * If the current transaction is already too large, then start
 172                 * to commit it: we can then go back and attach this handle to
 173                 * a new transaction.
 174                 */
 175                DEFINE_WAIT(wait);
 176
 177                jbd_debug(2, "Handle %p starting new commit...\n", handle);
 178                spin_unlock(&transaction->t_handle_lock);
 179                prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
 180                                TASK_UNINTERRUPTIBLE);
 181                __log_start_commit(journal, transaction->t_tid);
 182                spin_unlock(&journal->j_state_lock);
 183                schedule();
 184                finish_wait(&journal->j_wait_transaction_locked, &wait);
 185                goto repeat;
 186        }
 187
 188        /*
 189         * The commit code assumes that it can get enough log space
 190         * without forcing a checkpoint.  This is *critical* for
 191         * correctness: a checkpoint of a buffer which is also
 192         * associated with a committing transaction creates a deadlock,
 193         * so commit simply cannot force through checkpoints.
 194         *
 195         * We must therefore ensure the necessary space in the journal
 196         * *before* starting to dirty potentially checkpointed buffers
 197         * in the new transaction.
 198         *
 199         * The worst part is, any transaction currently committing can
 200         * reduce the free space arbitrarily.  Be careful to account for
 201         * those buffers when checkpointing.
 202         */
 203
 204        /*
 205         * @@@ AKPM: This seems rather over-defensive.  We're giving commit
 206         * a _lot_ of headroom: 1/4 of the journal plus the size of
 207         * the committing transaction.  Really, we only need to give it
 208         * committing_transaction->t_outstanding_credits plus "enough" for
 209         * the log control blocks.
 210         * Also, this test is inconsitent with the matching one in
 211         * journal_extend().
 212         */
 213        if (__log_space_left(journal) < jbd_space_needed(journal)) {
 214                jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
 215                spin_unlock(&transaction->t_handle_lock);
 216                __log_wait_for_space(journal);
 217                goto repeat_locked;
 218        }
 219
 220        /* OK, account for the buffers that this operation expects to
 221         * use and add the handle to the running transaction. */
 222
 223        handle->h_transaction = transaction;
 224        transaction->t_outstanding_credits += nblocks;
 225        transaction->t_updates++;
 226        transaction->t_handle_count++;
 227        jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
 228                  handle, nblocks, transaction->t_outstanding_credits,
 229                  __log_space_left(journal));
 230        spin_unlock(&transaction->t_handle_lock);
 231        spin_unlock(&journal->j_state_lock);
 232
 233        lock_map_acquire(&handle->h_lockdep_map);
 234out:
 235        if (unlikely(new_transaction))          /* It's usually NULL */
 236                kfree(new_transaction);
 237        return ret;
 238}
 239
 240static struct lock_class_key jbd_handle_key;
 241
 242/* Allocate a new handle.  This should probably be in a slab... */
 243static handle_t *new_handle(int nblocks)
 244{
 245        handle_t *handle = jbd_alloc_handle(GFP_NOFS);
 246        if (!handle)
 247                return NULL;
 248        memset(handle, 0, sizeof(*handle));
 249        handle->h_buffer_credits = nblocks;
 250        handle->h_ref = 1;
 251
 252        lockdep_init_map(&handle->h_lockdep_map, "jbd_handle", &jbd_handle_key, 0);
 253
 254        return handle;
 255}
 256
 257/**
 258 * handle_t *journal_start() - Obtain a new handle.
 259 * @journal: Journal to start transaction on.
 260 * @nblocks: number of block buffer we might modify
 261 *
 262 * We make sure that the transaction can guarantee at least nblocks of
 263 * modified buffers in the log.  We block until the log can guarantee
 264 * that much space.
 265 *
 266 * This function is visible to journal users (like ext3fs), so is not
 267 * called with the journal already locked.
 268 *
 269 * Return a pointer to a newly allocated handle, or NULL on failure
 270 */
 271handle_t *journal_start(journal_t *journal, int nblocks)
 272{
 273        handle_t *handle = journal_current_handle();
 274        int err;
 275
 276        if (!journal)
 277                return ERR_PTR(-EROFS);
 278
 279        if (handle) {
 280                J_ASSERT(handle->h_transaction->t_journal == journal);
 281                handle->h_ref++;
 282                return handle;
 283        }
 284
 285        handle = new_handle(nblocks);
 286        if (!handle)
 287                return ERR_PTR(-ENOMEM);
 288
 289        current->journal_info = handle;
 290
 291        err = start_this_handle(journal, handle);
 292        if (err < 0) {
 293                jbd_free_handle(handle);
 294                current->journal_info = NULL;
 295                handle = ERR_PTR(err);
 296        }
 297        return handle;
 298}
 299
 300/**
 301 * int journal_extend() - extend buffer credits.
 302 * @handle:  handle to 'extend'
 303 * @nblocks: nr blocks to try to extend by.
 304 *
 305 * Some transactions, such as large extends and truncates, can be done
 306 * atomically all at once or in several stages.  The operation requests
 307 * a credit for a number of buffer modications in advance, but can
 308 * extend its credit if it needs more.
 309 *
 310 * journal_extend tries to give the running handle more buffer credits.
 311 * It does not guarantee that allocation - this is a best-effort only.
 312 * The calling process MUST be able to deal cleanly with a failure to
 313 * extend here.
 314 *
 315 * Return 0 on success, non-zero on failure.
 316 *
 317 * return code < 0 implies an error
 318 * return code > 0 implies normal transaction-full status.
 319 */
 320int journal_extend(handle_t *handle, int nblocks)
 321{
 322        transaction_t *transaction = handle->h_transaction;
 323        journal_t *journal = transaction->t_journal;
 324        int result;
 325        int wanted;
 326
 327        result = -EIO;
 328        if (is_handle_aborted(handle))
 329                goto out;
 330
 331        result = 1;
 332
 333        spin_lock(&journal->j_state_lock);
 334
 335        /* Don't extend a locked-down transaction! */
 336        if (handle->h_transaction->t_state != T_RUNNING) {
 337                jbd_debug(3, "denied handle %p %d blocks: "
 338                          "transaction not running\n", handle, nblocks);
 339                goto error_out;
 340        }
 341
 342        spin_lock(&transaction->t_handle_lock);
 343        wanted = transaction->t_outstanding_credits + nblocks;
 344
 345        if (wanted > journal->j_max_transaction_buffers) {
 346                jbd_debug(3, "denied handle %p %d blocks: "
 347                          "transaction too large\n", handle, nblocks);
 348                goto unlock;
 349        }
 350
 351        if (wanted > __log_space_left(journal)) {
 352                jbd_debug(3, "denied handle %p %d blocks: "
 353                          "insufficient log space\n", handle, nblocks);
 354                goto unlock;
 355        }
 356
 357        handle->h_buffer_credits += nblocks;
 358        transaction->t_outstanding_credits += nblocks;
 359        result = 0;
 360
 361        jbd_debug(3, "extended handle %p by %d\n", handle, nblocks);
 362unlock:
 363        spin_unlock(&transaction->t_handle_lock);
 364error_out:
 365        spin_unlock(&journal->j_state_lock);
 366out:
 367        return result;
 368}
 369
 370
 371/**
 372 * int journal_restart() - restart a handle.
 373 * @handle:  handle to restart
 374 * @nblocks: nr credits requested
 375 *
 376 * Restart a handle for a multi-transaction filesystem
 377 * operation.
 378 *
 379 * If the journal_extend() call above fails to grant new buffer credits
 380 * to a running handle, a call to journal_restart will commit the
 381 * handle's transaction so far and reattach the handle to a new
 382 * transaction capabable of guaranteeing the requested number of
 383 * credits.
 384 */
 385
 386int journal_restart(handle_t *handle, int nblocks)
 387{
 388        transaction_t *transaction = handle->h_transaction;
 389        journal_t *journal = transaction->t_journal;
 390        int ret;
 391
 392        /* If we've had an abort of any type, don't even think about
 393         * actually doing the restart! */
 394        if (is_handle_aborted(handle))
 395                return 0;
 396
 397        /*
 398         * First unlink the handle from its current transaction, and start the
 399         * commit on that.
 400         */
 401        J_ASSERT(transaction->t_updates > 0);
 402        J_ASSERT(journal_current_handle() == handle);
 403
 404        spin_lock(&journal->j_state_lock);
 405        spin_lock(&transaction->t_handle_lock);
 406        transaction->t_outstanding_credits -= handle->h_buffer_credits;
 407        transaction->t_updates--;
 408
 409        if (!transaction->t_updates)
 410                wake_up(&journal->j_wait_updates);
 411        spin_unlock(&transaction->t_handle_lock);
 412
 413        jbd_debug(2, "restarting handle %p\n", handle);
 414        __log_start_commit(journal, transaction->t_tid);
 415        spin_unlock(&journal->j_state_lock);
 416
 417        lock_map_release(&handle->h_lockdep_map);
 418        handle->h_buffer_credits = nblocks;
 419        ret = start_this_handle(journal, handle);
 420        return ret;
 421}
 422
 423
 424/**
 425 * void journal_lock_updates () - establish a transaction barrier.
 426 * @journal:  Journal to establish a barrier on.
 427 *
 428 * This locks out any further updates from being started, and blocks
 429 * until all existing updates have completed, returning only once the
 430 * journal is in a quiescent state with no updates running.
 431 *
 432 * The journal lock should not be held on entry.
 433 */
 434void journal_lock_updates(journal_t *journal)
 435{
 436        DEFINE_WAIT(wait);
 437
 438        spin_lock(&journal->j_state_lock);
 439        ++journal->j_barrier_count;
 440
 441        /* Wait until there are no running updates */
 442        while (1) {
 443                transaction_t *transaction = journal->j_running_transaction;
 444
 445                if (!transaction)
 446                        break;
 447
 448                spin_lock(&transaction->t_handle_lock);
 449                if (!transaction->t_updates) {
 450                        spin_unlock(&transaction->t_handle_lock);
 451                        break;
 452                }
 453                prepare_to_wait(&journal->j_wait_updates, &wait,
 454                                TASK_UNINTERRUPTIBLE);
 455                spin_unlock(&transaction->t_handle_lock);
 456                spin_unlock(&journal->j_state_lock);
 457                schedule();
 458                finish_wait(&journal->j_wait_updates, &wait);
 459                spin_lock(&journal->j_state_lock);
 460        }
 461        spin_unlock(&journal->j_state_lock);
 462
 463        /*
 464         * We have now established a barrier against other normal updates, but
 465         * we also need to barrier against other journal_lock_updates() calls
 466         * to make sure that we serialise special journal-locked operations
 467         * too.
 468         */
 469        mutex_lock(&journal->j_barrier);
 470}
 471
 472/**
 473 * void journal_unlock_updates (journal_t* journal) - release barrier
 474 * @journal:  Journal to release the barrier on.
 475 *
 476 * Release a transaction barrier obtained with journal_lock_updates().
 477 *
 478 * Should be called without the journal lock held.
 479 */
 480void journal_unlock_updates (journal_t *journal)
 481{
 482        J_ASSERT(journal->j_barrier_count != 0);
 483
 484        mutex_unlock(&journal->j_barrier);
 485        spin_lock(&journal->j_state_lock);
 486        --journal->j_barrier_count;
 487        spin_unlock(&journal->j_state_lock);
 488        wake_up(&journal->j_wait_transaction_locked);
 489}
 490
 491static void warn_dirty_buffer(struct buffer_head *bh)
 492{
 493        char b[BDEVNAME_SIZE];
 494
 495        printk(KERN_WARNING
 496               "JBD: Spotted dirty metadata buffer (dev = %s, blocknr = %llu). "
 497               "There's a risk of filesystem corruption in case of system "
 498               "crash.\n",
 499               bdevname(bh->b_bdev, b), (unsigned long long)bh->b_blocknr);
 500}
 501
 502/*
 503 * If the buffer is already part of the current transaction, then there
 504 * is nothing we need to do.  If it is already part of a prior
 505 * transaction which we are still committing to disk, then we need to
 506 * make sure that we do not overwrite the old copy: we do copy-out to
 507 * preserve the copy going to disk.  We also account the buffer against
 508 * the handle's metadata buffer credits (unless the buffer is already
 509 * part of the transaction, that is).
 510 *
 511 */
 512static int
 513do_get_write_access(handle_t *handle, struct journal_head *jh,
 514                        int force_copy)
 515{
 516        struct buffer_head *bh;
 517        transaction_t *transaction;
 518        journal_t *journal;
 519        int error;
 520        char *frozen_buffer = NULL;
 521        int need_copy = 0;
 522
 523        if (is_handle_aborted(handle))
 524                return -EROFS;
 525
 526        transaction = handle->h_transaction;
 527        journal = transaction->t_journal;
 528
 529        jbd_debug(5, "journal_head %p, force_copy %d\n", jh, force_copy);
 530
 531        JBUFFER_TRACE(jh, "entry");
 532repeat:
 533        bh = jh2bh(jh);
 534
 535        /* @@@ Need to check for errors here at some point. */
 536
 537        lock_buffer(bh);
 538        jbd_lock_bh_state(bh);
 539
 540        /* We now hold the buffer lock so it is safe to query the buffer
 541         * state.  Is the buffer dirty?
 542         *
 543         * If so, there are two possibilities.  The buffer may be
 544         * non-journaled, and undergoing a quite legitimate writeback.
 545         * Otherwise, it is journaled, and we don't expect dirty buffers
 546         * in that state (the buffers should be marked JBD_Dirty
 547         * instead.)  So either the IO is being done under our own
 548         * control and this is a bug, or it's a third party IO such as
 549         * dump(8) (which may leave the buffer scheduled for read ---
 550         * ie. locked but not dirty) or tune2fs (which may actually have
 551         * the buffer dirtied, ugh.)  */
 552
 553        if (buffer_dirty(bh)) {
 554                /*
 555                 * First question: is this buffer already part of the current
 556                 * transaction or the existing committing transaction?
 557                 */
 558                if (jh->b_transaction) {
 559                        J_ASSERT_JH(jh,
 560                                jh->b_transaction == transaction ||
 561                                jh->b_transaction ==
 562                                        journal->j_committing_transaction);
 563                        if (jh->b_next_transaction)
 564                                J_ASSERT_JH(jh, jh->b_next_transaction ==
 565                                                        transaction);
 566                        warn_dirty_buffer(bh);
 567                }
 568                /*
 569                 * In any case we need to clean the dirty flag and we must
 570                 * do it under the buffer lock to be sure we don't race
 571                 * with running write-out.
 572                 */
 573                JBUFFER_TRACE(jh, "Journalling dirty buffer");
 574                clear_buffer_dirty(bh);
 575                set_buffer_jbddirty(bh);
 576        }
 577
 578        unlock_buffer(bh);
 579
 580        error = -EROFS;
 581        if (is_handle_aborted(handle)) {
 582                jbd_unlock_bh_state(bh);
 583                goto out;
 584        }
 585        error = 0;
 586
 587        /*
 588         * The buffer is already part of this transaction if b_transaction or
 589         * b_next_transaction points to it
 590         */
 591        if (jh->b_transaction == transaction ||
 592            jh->b_next_transaction == transaction)
 593                goto done;
 594
 595        /*
 596         * this is the first time this transaction is touching this buffer,
 597         * reset the modified flag
 598         */
 599        jh->b_modified = 0;
 600
 601        /*
 602         * If there is already a copy-out version of this buffer, then we don't
 603         * need to make another one
 604         */
 605        if (jh->b_frozen_data) {
 606                JBUFFER_TRACE(jh, "has frozen data");
 607                J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
 608                jh->b_next_transaction = transaction;
 609                goto done;
 610        }
 611
 612        /* Is there data here we need to preserve? */
 613
 614        if (jh->b_transaction && jh->b_transaction != transaction) {
 615                JBUFFER_TRACE(jh, "owned by older transaction");
 616                J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
 617                J_ASSERT_JH(jh, jh->b_transaction ==
 618                                        journal->j_committing_transaction);
 619
 620                /* There is one case we have to be very careful about.
 621                 * If the committing transaction is currently writing
 622                 * this buffer out to disk and has NOT made a copy-out,
 623                 * then we cannot modify the buffer contents at all
 624                 * right now.  The essence of copy-out is that it is the
 625                 * extra copy, not the primary copy, which gets
 626                 * journaled.  If the primary copy is already going to
 627                 * disk then we cannot do copy-out here. */
 628
 629                if (jh->b_jlist == BJ_Shadow) {
 630                        DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Unshadow);
 631                        wait_queue_head_t *wqh;
 632
 633                        wqh = bit_waitqueue(&bh->b_state, BH_Unshadow);
 634
 635                        JBUFFER_TRACE(jh, "on shadow: sleep");
 636                        jbd_unlock_bh_state(bh);
 637                        /* commit wakes up all shadow buffers after IO */
 638                        for ( ; ; ) {
 639                                prepare_to_wait(wqh, &wait.wait,
 640                                                TASK_UNINTERRUPTIBLE);
 641                                if (jh->b_jlist != BJ_Shadow)
 642                                        break;
 643                                schedule();
 644                        }
 645                        finish_wait(wqh, &wait.wait);
 646                        goto repeat;
 647                }
 648
 649                /* Only do the copy if the currently-owning transaction
 650                 * still needs it.  If it is on the Forget list, the
 651                 * committing transaction is past that stage.  The
 652                 * buffer had better remain locked during the kmalloc,
 653                 * but that should be true --- we hold the journal lock
 654                 * still and the buffer is already on the BUF_JOURNAL
 655                 * list so won't be flushed.
 656                 *
 657                 * Subtle point, though: if this is a get_undo_access,
 658                 * then we will be relying on the frozen_data to contain
 659                 * the new value of the committed_data record after the
 660                 * transaction, so we HAVE to force the frozen_data copy
 661                 * in that case. */
 662
 663                if (jh->b_jlist != BJ_Forget || force_copy) {
 664                        JBUFFER_TRACE(jh, "generate frozen data");
 665                        if (!frozen_buffer) {
 666                                JBUFFER_TRACE(jh, "allocate memory for buffer");
 667                                jbd_unlock_bh_state(bh);
 668                                frozen_buffer =
 669                                        jbd_alloc(jh2bh(jh)->b_size,
 670                                                         GFP_NOFS);
 671                                if (!frozen_buffer) {
 672                                        printk(KERN_EMERG
 673                                               "%s: OOM for frozen_buffer\n",
 674                                               __func__);
 675                                        JBUFFER_TRACE(jh, "oom!");
 676                                        error = -ENOMEM;
 677                                        jbd_lock_bh_state(bh);
 678                                        goto done;
 679                                }
 680                                goto repeat;
 681                        }
 682                        jh->b_frozen_data = frozen_buffer;
 683                        frozen_buffer = NULL;
 684                        need_copy = 1;
 685                }
 686                jh->b_next_transaction = transaction;
 687        }
 688
 689
 690        /*
 691         * Finally, if the buffer is not journaled right now, we need to make
 692         * sure it doesn't get written to disk before the caller actually
 693         * commits the new data
 694         */
 695        if (!jh->b_transaction) {
 696                JBUFFER_TRACE(jh, "no transaction");
 697                J_ASSERT_JH(jh, !jh->b_next_transaction);
 698                jh->b_transaction = transaction;
 699                JBUFFER_TRACE(jh, "file as BJ_Reserved");
 700                spin_lock(&journal->j_list_lock);
 701                __journal_file_buffer(jh, transaction, BJ_Reserved);
 702                spin_unlock(&journal->j_list_lock);
 703        }
 704
 705done:
 706        if (need_copy) {
 707                struct page *page;
 708                int offset;
 709                char *source;
 710
 711                J_EXPECT_JH(jh, buffer_uptodate(jh2bh(jh)),
 712                            "Possible IO failure.\n");
 713                page = jh2bh(jh)->b_page;
 714                offset = offset_in_page(jh2bh(jh)->b_data);
 715                source = kmap_atomic(page, KM_USER0);
 716                memcpy(jh->b_frozen_data, source+offset, jh2bh(jh)->b_size);
 717                kunmap_atomic(source, KM_USER0);
 718        }
 719        jbd_unlock_bh_state(bh);
 720
 721        /*
 722         * If we are about to journal a buffer, then any revoke pending on it is
 723         * no longer valid
 724         */
 725        journal_cancel_revoke(handle, jh);
 726
 727out:
 728        if (unlikely(frozen_buffer))    /* It's usually NULL */
 729                jbd_free(frozen_buffer, bh->b_size);
 730
 731        JBUFFER_TRACE(jh, "exit");
 732        return error;
 733}
 734
 735/**
 736 * int journal_get_write_access() - notify intent to modify a buffer for metadata (not data) update.
 737 * @handle: transaction to add buffer modifications to
 738 * @bh:     bh to be used for metadata writes
 739 *
 740 * Returns an error code or 0 on success.
 741 *
 742 * In full data journalling mode the buffer may be of type BJ_AsyncData,
 743 * because we're write()ing a buffer which is also part of a shared mapping.
 744 */
 745
 746int journal_get_write_access(handle_t *handle, struct buffer_head *bh)
 747{
 748        struct journal_head *jh = journal_add_journal_head(bh);
 749        int rc;
 750
 751        /* We do not want to get caught playing with fields which the
 752         * log thread also manipulates.  Make sure that the buffer
 753         * completes any outstanding IO before proceeding. */
 754        rc = do_get_write_access(handle, jh, 0);
 755        journal_put_journal_head(jh);
 756        return rc;
 757}
 758
 759
 760/*
 761 * When the user wants to journal a newly created buffer_head
 762 * (ie. getblk() returned a new buffer and we are going to populate it
 763 * manually rather than reading off disk), then we need to keep the
 764 * buffer_head locked until it has been completely filled with new
 765 * data.  In this case, we should be able to make the assertion that
 766 * the bh is not already part of an existing transaction.
 767 *
 768 * The buffer should already be locked by the caller by this point.
 769 * There is no lock ranking violation: it was a newly created,
 770 * unlocked buffer beforehand. */
 771
 772/**
 773 * int journal_get_create_access () - notify intent to use newly created bh
 774 * @handle: transaction to new buffer to
 775 * @bh: new buffer.
 776 *
 777 * Call this if you create a new bh.
 778 */
 779int journal_get_create_access(handle_t *handle, struct buffer_head *bh)
 780{
 781        transaction_t *transaction = handle->h_transaction;
 782        journal_t *journal = transaction->t_journal;
 783        struct journal_head *jh = journal_add_journal_head(bh);
 784        int err;
 785
 786        jbd_debug(5, "journal_head %p\n", jh);
 787        err = -EROFS;
 788        if (is_handle_aborted(handle))
 789                goto out;
 790        err = 0;
 791
 792        JBUFFER_TRACE(jh, "entry");
 793        /*
 794         * The buffer may already belong to this transaction due to pre-zeroing
 795         * in the filesystem's new_block code.  It may also be on the previous,
 796         * committing transaction's lists, but it HAS to be in Forget state in
 797         * that case: the transaction must have deleted the buffer for it to be
 798         * reused here.
 799         */
 800        jbd_lock_bh_state(bh);
 801        spin_lock(&journal->j_list_lock);
 802        J_ASSERT_JH(jh, (jh->b_transaction == transaction ||
 803                jh->b_transaction == NULL ||
 804                (jh->b_transaction == journal->j_committing_transaction &&
 805                          jh->b_jlist == BJ_Forget)));
 806
 807        J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
 808        J_ASSERT_JH(jh, buffer_locked(jh2bh(jh)));
 809
 810        if (jh->b_transaction == NULL) {
 811                /*
 812                 * Previous journal_forget() could have left the buffer
 813                 * with jbddirty bit set because it was being committed. When
 814                 * the commit finished, we've filed the buffer for
 815                 * checkpointing and marked it dirty. Now we are reallocating
 816                 * the buffer so the transaction freeing it must have
 817                 * committed and so it's safe to clear the dirty bit.
 818                 */
 819                clear_buffer_dirty(jh2bh(jh));
 820                jh->b_transaction = transaction;
 821
 822                /* first access by this transaction */
 823                jh->b_modified = 0;
 824
 825                JBUFFER_TRACE(jh, "file as BJ_Reserved");
 826                __journal_file_buffer(jh, transaction, BJ_Reserved);
 827        } else if (jh->b_transaction == journal->j_committing_transaction) {
 828                /* first access by this transaction */
 829                jh->b_modified = 0;
 830
 831                JBUFFER_TRACE(jh, "set next transaction");
 832                jh->b_next_transaction = transaction;
 833        }
 834        spin_unlock(&journal->j_list_lock);
 835        jbd_unlock_bh_state(bh);
 836
 837        /*
 838         * akpm: I added this.  ext3_alloc_branch can pick up new indirect
 839         * blocks which contain freed but then revoked metadata.  We need
 840         * to cancel the revoke in case we end up freeing it yet again
 841         * and the reallocating as data - this would cause a second revoke,
 842         * which hits an assertion error.
 843         */
 844        JBUFFER_TRACE(jh, "cancelling revoke");
 845        journal_cancel_revoke(handle, jh);
 846        journal_put_journal_head(jh);
 847out:
 848        return err;
 849}
 850
 851/**
 852 * int journal_get_undo_access() - Notify intent to modify metadata with non-rewindable consequences
 853 * @handle: transaction
 854 * @bh: buffer to undo
 855 *
 856 * Sometimes there is a need to distinguish between metadata which has
 857 * been committed to disk and that which has not.  The ext3fs code uses
 858 * this for freeing and allocating space, we have to make sure that we
 859 * do not reuse freed space until the deallocation has been committed,
 860 * since if we overwrote that space we would make the delete
 861 * un-rewindable in case of a crash.
 862 *
 863 * To deal with that, journal_get_undo_access requests write access to a
 864 * buffer for parts of non-rewindable operations such as delete
 865 * operations on the bitmaps.  The journaling code must keep a copy of
 866 * the buffer's contents prior to the undo_access call until such time
 867 * as we know that the buffer has definitely been committed to disk.
 868 *
 869 * We never need to know which transaction the committed data is part
 870 * of, buffers touched here are guaranteed to be dirtied later and so
 871 * will be committed to a new transaction in due course, at which point
 872 * we can discard the old committed data pointer.
 873 *
 874 * Returns error number or 0 on success.
 875 */
 876int journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
 877{
 878        int err;
 879        struct journal_head *jh = journal_add_journal_head(bh);
 880        char *committed_data = NULL;
 881
 882        JBUFFER_TRACE(jh, "entry");
 883
 884        /*
 885         * Do this first --- it can drop the journal lock, so we want to
 886         * make sure that obtaining the committed_data is done
 887         * atomically wrt. completion of any outstanding commits.
 888         */
 889        err = do_get_write_access(handle, jh, 1);
 890        if (err)
 891                goto out;
 892
 893repeat:
 894        if (!jh->b_committed_data) {
 895                committed_data = jbd_alloc(jh2bh(jh)->b_size, GFP_NOFS);
 896                if (!committed_data) {
 897                        printk(KERN_EMERG "%s: No memory for committed data\n",
 898                                __func__);
 899                        err = -ENOMEM;
 900                        goto out;
 901                }
 902        }
 903
 904        jbd_lock_bh_state(bh);
 905        if (!jh->b_committed_data) {
 906                /* Copy out the current buffer contents into the
 907                 * preserved, committed copy. */
 908                JBUFFER_TRACE(jh, "generate b_committed data");
 909                if (!committed_data) {
 910                        jbd_unlock_bh_state(bh);
 911                        goto repeat;
 912                }
 913
 914                jh->b_committed_data = committed_data;
 915                committed_data = NULL;
 916                memcpy(jh->b_committed_data, bh->b_data, bh->b_size);
 917        }
 918        jbd_unlock_bh_state(bh);
 919out:
 920        journal_put_journal_head(jh);
 921        if (unlikely(committed_data))
 922                jbd_free(committed_data, bh->b_size);
 923        return err;
 924}
 925
 926/**
 927 * int journal_dirty_data() - mark a buffer as containing dirty data to be flushed
 928 * @handle: transaction
 929 * @bh: bufferhead to mark
 930 *
 931 * Description:
 932 * Mark a buffer as containing dirty data which needs to be flushed before
 933 * we can commit the current transaction.
 934 *
 935 * The buffer is placed on the transaction's data list and is marked as
 936 * belonging to the transaction.
 937 *
 938 * Returns error number or 0 on success.
 939 *
 940 * journal_dirty_data() can be called via page_launder->ext3_writepage
 941 * by kswapd.
 942 */
 943int journal_dirty_data(handle_t *handle, struct buffer_head *bh)
 944{
 945        journal_t *journal = handle->h_transaction->t_journal;
 946        int need_brelse = 0;
 947        struct journal_head *jh;
 948        int ret = 0;
 949
 950        if (is_handle_aborted(handle))
 951                return ret;
 952
 953        jh = journal_add_journal_head(bh);
 954        JBUFFER_TRACE(jh, "entry");
 955
 956        /*
 957         * The buffer could *already* be dirty.  Writeout can start
 958         * at any time.
 959         */
 960        jbd_debug(4, "jh: %p, tid:%d\n", jh, handle->h_transaction->t_tid);
 961
 962        /*
 963         * What if the buffer is already part of a running transaction?
 964         *
 965         * There are two cases:
 966         * 1) It is part of the current running transaction.  Refile it,
 967         *    just in case we have allocated it as metadata, deallocated
 968         *    it, then reallocated it as data.
 969         * 2) It is part of the previous, still-committing transaction.
 970         *    If all we want to do is to guarantee that the buffer will be
 971         *    written to disk before this new transaction commits, then
 972         *    being sure that the *previous* transaction has this same
 973         *    property is sufficient for us!  Just leave it on its old
 974         *    transaction.
 975         *
 976         * In case (2), the buffer must not already exist as metadata
 977         * --- that would violate write ordering (a transaction is free
 978         * to write its data at any point, even before the previous
 979         * committing transaction has committed).  The caller must
 980         * never, ever allow this to happen: there's nothing we can do
 981         * about it in this layer.
 982         */
 983        jbd_lock_bh_state(bh);
 984        spin_lock(&journal->j_list_lock);
 985
 986        /* Now that we have bh_state locked, are we really still mapped? */
 987        if (!buffer_mapped(bh)) {
 988                JBUFFER_TRACE(jh, "unmapped buffer, bailing out");
 989                goto no_journal;
 990        }
 991
 992        if (jh->b_transaction) {
 993                JBUFFER_TRACE(jh, "has transaction");
 994                if (jh->b_transaction != handle->h_transaction) {
 995                        JBUFFER_TRACE(jh, "belongs to older transaction");
 996                        J_ASSERT_JH(jh, jh->b_transaction ==
 997                                        journal->j_committing_transaction);
 998
 999                        /* @@@ IS THIS TRUE  ? */
1000                        /*
1001                         * Not any more.  Scenario: someone does a write()
1002                         * in data=journal mode.  The buffer's transaction has
1003                         * moved into commit.  Then someone does another
1004                         * write() to the file.  We do the frozen data copyout
1005                         * and set b_next_transaction to point to j_running_t.
1006                         * And while we're in that state, someone does a
1007                         * writepage() in an attempt to pageout the same area
1008                         * of the file via a shared mapping.  At present that
1009                         * calls journal_dirty_data(), and we get right here.
1010                         * It may be too late to journal the data.  Simply
1011                         * falling through to the next test will suffice: the
1012                         * data will be dirty and wil be checkpointed.  The
1013                         * ordering comments in the next comment block still
1014                         * apply.
1015                         */
1016                        //J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
1017
1018                        /*
1019                         * If we're journalling data, and this buffer was
1020                         * subject to a write(), it could be metadata, forget
1021                         * or shadow against the committing transaction.  Now,
1022                         * someone has dirtied the same darn page via a mapping
1023                         * and it is being writepage()'d.
1024                         * We *could* just steal the page from commit, with some
1025                         * fancy locking there.  Instead, we just skip it -
1026                         * don't tie the page's buffers to the new transaction
1027                         * at all.
1028                         * Implication: if we crash before the writepage() data
1029                         * is written into the filesystem, recovery will replay
1030                         * the write() data.
1031                         */
1032                        if (jh->b_jlist != BJ_None &&
1033                                        jh->b_jlist != BJ_SyncData &&
1034                                        jh->b_jlist != BJ_Locked) {
1035                                JBUFFER_TRACE(jh, "Not stealing");
1036                                goto no_journal;
1037                        }
1038
1039                        /*
1040                         * This buffer may be undergoing writeout in commit.  We
1041                         * can't return from here and let the caller dirty it
1042                         * again because that can cause the write-out loop in
1043                         * commit to never terminate.
1044                         */
1045                        if (buffer_dirty(bh)) {
1046                                get_bh(bh);
1047                                spin_unlock(&journal->j_list_lock);
1048                                jbd_unlock_bh_state(bh);
1049                                need_brelse = 1;
1050                                sync_dirty_buffer(bh);
1051                                jbd_lock_bh_state(bh);
1052                                spin_lock(&journal->j_list_lock);
1053                                /* Since we dropped the lock... */
1054                                if (!buffer_mapped(bh)) {
1055                                        JBUFFER_TRACE(jh, "buffer got unmapped");
1056                                        goto no_journal;
1057                                }
1058                                /* The buffer may become locked again at any
1059                                   time if it is redirtied */
1060                        }
1061
1062                        /*
1063                         * We cannot remove the buffer with io error from the
1064                         * committing transaction, because otherwise it would
1065                         * miss the error and the commit would not abort.
1066                         */
1067                        if (unlikely(!buffer_uptodate(bh))) {
1068                                ret = -EIO;
1069                                goto no_journal;
1070                        }
1071
1072                        if (jh->b_transaction != NULL) {
1073                                JBUFFER_TRACE(jh, "unfile from commit");
1074                                __journal_temp_unlink_buffer(jh);
1075                                /* It still points to the committing
1076                                 * transaction; move it to this one so
1077                                 * that the refile assert checks are
1078                                 * happy. */
1079                                jh->b_transaction = handle->h_transaction;
1080                        }
1081                        /* The buffer will be refiled below */
1082
1083                }
1084                /*
1085                 * Special case --- the buffer might actually have been
1086                 * allocated and then immediately deallocated in the previous,
1087                 * committing transaction, so might still be left on that
1088                 * transaction's metadata lists.
1089                 */
1090                if (jh->b_jlist != BJ_SyncData && jh->b_jlist != BJ_Locked) {
1091                        JBUFFER_TRACE(jh, "not on correct data list: unfile");
1092                        J_ASSERT_JH(jh, jh->b_jlist != BJ_Shadow);
1093                        __journal_temp_unlink_buffer(jh);
1094                        jh->b_transaction = handle->h_transaction;
1095                        JBUFFER_TRACE(jh, "file as data");
1096                        __journal_file_buffer(jh, handle->h_transaction,
1097                                                BJ_SyncData);
1098                }
1099        } else {
1100                JBUFFER_TRACE(jh, "not on a transaction");
1101                __journal_file_buffer(jh, handle->h_transaction, BJ_SyncData);
1102        }
1103no_journal:
1104        spin_unlock(&journal->j_list_lock);
1105        jbd_unlock_bh_state(bh);
1106        if (need_brelse) {
1107                BUFFER_TRACE(bh, "brelse");
1108                __brelse(bh);
1109        }
1110        JBUFFER_TRACE(jh, "exit");
1111        journal_put_journal_head(jh);
1112        return ret;
1113}
1114
1115/**
1116 * int journal_dirty_metadata() - mark a buffer as containing dirty metadata
1117 * @handle: transaction to add buffer to.
1118 * @bh: buffer to mark
1119 *
1120 * Mark dirty metadata which needs to be journaled as part of the current
1121 * transaction.
1122 *
1123 * The buffer is placed on the transaction's metadata list and is marked
1124 * as belonging to the transaction.
1125 *
1126 * Returns error number or 0 on success.
1127 *
1128 * Special care needs to be taken if the buffer already belongs to the
1129 * current committing transaction (in which case we should have frozen
1130 * data present for that commit).  In that case, we don't relink the
1131 * buffer: that only gets done when the old transaction finally
1132 * completes its commit.
1133 */
1134int journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
1135{
1136        transaction_t *transaction = handle->h_transaction;
1137        journal_t *journal = transaction->t_journal;
1138        struct journal_head *jh = bh2jh(bh);
1139
1140        jbd_debug(5, "journal_head %p\n", jh);
1141        JBUFFER_TRACE(jh, "entry");
1142        if (is_handle_aborted(handle))
1143                goto out;
1144
1145        jbd_lock_bh_state(bh);
1146
1147        if (jh->b_modified == 0) {
1148                /*
1149                 * This buffer's got modified and becoming part
1150                 * of the transaction. This needs to be done
1151                 * once a transaction -bzzz
1152                 */
1153                jh->b_modified = 1;
1154                J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
1155                handle->h_buffer_credits--;
1156        }
1157
1158        /*
1159         * fastpath, to avoid expensive locking.  If this buffer is already
1160         * on the running transaction's metadata list there is nothing to do.
1161         * Nobody can take it off again because there is a handle open.
1162         * I _think_ we're OK here with SMP barriers - a mistaken decision will
1163         * result in this test being false, so we go in and take the locks.
1164         */
1165        if (jh->b_transaction == transaction && jh->b_jlist == BJ_Metadata) {
1166                JBUFFER_TRACE(jh, "fastpath");
1167                J_ASSERT_JH(jh, jh->b_transaction ==
1168                                        journal->j_running_transaction);
1169                goto out_unlock_bh;
1170        }
1171
1172        set_buffer_jbddirty(bh);
1173
1174        /*
1175         * Metadata already on the current transaction list doesn't
1176         * need to be filed.  Metadata on another transaction's list must
1177         * be committing, and will be refiled once the commit completes:
1178         * leave it alone for now.
1179         */
1180        if (jh->b_transaction != transaction) {
1181                JBUFFER_TRACE(jh, "already on other transaction");
1182                J_ASSERT_JH(jh, jh->b_transaction ==
1183                                        journal->j_committing_transaction);
1184                J_ASSERT_JH(jh, jh->b_next_transaction == transaction);
1185                /* And this case is illegal: we can't reuse another
1186                 * transaction's data buffer, ever. */
1187                goto out_unlock_bh;
1188        }
1189
1190        /* That test should have eliminated the following case: */
1191        J_ASSERT_JH(jh, jh->b_frozen_data == NULL);
1192
1193        JBUFFER_TRACE(jh, "file as BJ_Metadata");
1194        spin_lock(&journal->j_list_lock);
1195        __journal_file_buffer(jh, handle->h_transaction, BJ_Metadata);
1196        spin_unlock(&journal->j_list_lock);
1197out_unlock_bh:
1198        jbd_unlock_bh_state(bh);
1199out:
1200        JBUFFER_TRACE(jh, "exit");
1201        return 0;
1202}
1203
1204/*
1205 * journal_release_buffer: undo a get_write_access without any buffer
1206 * updates, if the update decided in the end that it didn't need access.
1207 *
1208 */
1209void
1210journal_release_buffer(handle_t *handle, struct buffer_head *bh)
1211{
1212        BUFFER_TRACE(bh, "entry");
1213}
1214
1215/**
1216 * void journal_forget() - bforget() for potentially-journaled buffers.
1217 * @handle: transaction handle
1218 * @bh:     bh to 'forget'
1219 *
1220 * We can only do the bforget if there are no commits pending against the
1221 * buffer.  If the buffer is dirty in the current running transaction we
1222 * can safely unlink it.
1223 *
1224 * bh may not be a journalled buffer at all - it may be a non-JBD
1225 * buffer which came off the hashtable.  Check for this.
1226 *
1227 * Decrements bh->b_count by one.
1228 *
1229 * Allow this call even if the handle has aborted --- it may be part of
1230 * the caller's cleanup after an abort.
1231 */
1232int journal_forget (handle_t *handle, struct buffer_head *bh)
1233{
1234        transaction_t *transaction = handle->h_transaction;
1235        journal_t *journal = transaction->t_journal;
1236        struct journal_head *jh;
1237        int drop_reserve = 0;
1238        int err = 0;
1239        int was_modified = 0;
1240
1241        BUFFER_TRACE(bh, "entry");
1242
1243        jbd_lock_bh_state(bh);
1244        spin_lock(&journal->j_list_lock);
1245
1246        if (!buffer_jbd(bh))
1247                goto not_jbd;
1248        jh = bh2jh(bh);
1249
1250        /* Critical error: attempting to delete a bitmap buffer, maybe?
1251         * Don't do any jbd operations, and return an error. */
1252        if (!J_EXPECT_JH(jh, !jh->b_committed_data,
1253                         "inconsistent data on disk")) {
1254                err = -EIO;
1255                goto not_jbd;
1256        }
1257
1258        /* keep track of wether or not this transaction modified us */
1259        was_modified = jh->b_modified;
1260
1261        /*
1262         * The buffer's going from the transaction, we must drop
1263         * all references -bzzz
1264         */
1265        jh->b_modified = 0;
1266
1267        if (jh->b_transaction == handle->h_transaction) {
1268                J_ASSERT_JH(jh, !jh->b_frozen_data);
1269
1270                /* If we are forgetting a buffer which is already part
1271                 * of this transaction, then we can just drop it from
1272                 * the transaction immediately. */
1273                clear_buffer_dirty(bh);
1274                clear_buffer_jbddirty(bh);
1275
1276                JBUFFER_TRACE(jh, "belongs to current transaction: unfile");
1277
1278                /*
1279                 * we only want to drop a reference if this transaction
1280                 * modified the buffer
1281                 */
1282                if (was_modified)
1283                        drop_reserve = 1;
1284
1285                /*
1286                 * We are no longer going to journal this buffer.
1287                 * However, the commit of this transaction is still
1288                 * important to the buffer: the delete that we are now
1289                 * processing might obsolete an old log entry, so by
1290                 * committing, we can satisfy the buffer's checkpoint.
1291                 *
1292                 * So, if we have a checkpoint on the buffer, we should
1293                 * now refile the buffer on our BJ_Forget list so that
1294                 * we know to remove the checkpoint after we commit.
1295                 */
1296
1297                if (jh->b_cp_transaction) {
1298                        __journal_temp_unlink_buffer(jh);
1299                        __journal_file_buffer(jh, transaction, BJ_Forget);
1300                } else {
1301                        __journal_unfile_buffer(jh);
1302                        journal_remove_journal_head(bh);
1303                        __brelse(bh);
1304                        if (!buffer_jbd(bh)) {
1305                                spin_unlock(&journal->j_list_lock);
1306                                jbd_unlock_bh_state(bh);
1307                                __bforget(bh);
1308                                goto drop;
1309                        }
1310                }
1311        } else if (jh->b_transaction) {
1312                J_ASSERT_JH(jh, (jh->b_transaction ==
1313                                 journal->j_committing_transaction));
1314                /* However, if the buffer is still owned by a prior
1315                 * (committing) transaction, we can't drop it yet... */
1316                JBUFFER_TRACE(jh, "belongs to older transaction");
1317                /* ... but we CAN drop it from the new transaction if we
1318                 * have also modified it since the original commit. */
1319
1320                if (jh->b_next_transaction) {
1321                        J_ASSERT(jh->b_next_transaction == transaction);
1322                        jh->b_next_transaction = NULL;
1323
1324                        /*
1325                         * only drop a reference if this transaction modified
1326                         * the buffer
1327                         */
1328                        if (was_modified)
1329                                drop_reserve = 1;
1330                }
1331        }
1332
1333not_jbd:
1334        spin_unlock(&journal->j_list_lock);
1335        jbd_unlock_bh_state(bh);
1336        __brelse(bh);
1337drop:
1338        if (drop_reserve) {
1339                /* no need to reserve log space for this block -bzzz */
1340                handle->h_buffer_credits++;
1341        }
1342        return err;
1343}
1344
1345/**
1346 * int journal_stop() - complete a transaction
1347 * @handle: tranaction to complete.
1348 *
1349 * All done for a particular handle.
1350 *
1351 * There is not much action needed here.  We just return any remaining
1352 * buffer credits to the transaction and remove the handle.  The only
1353 * complication is that we need to start a commit operation if the
1354 * filesystem is marked for synchronous update.
1355 *
1356 * journal_stop itself will not usually return an error, but it may
1357 * do so in unusual circumstances.  In particular, expect it to
1358 * return -EIO if a journal_abort has been executed since the
1359 * transaction began.
1360 */
1361int journal_stop(handle_t *handle)
1362{
1363        transaction_t *transaction = handle->h_transaction;
1364        journal_t *journal = transaction->t_journal;
1365        int err;
1366        pid_t pid;
1367
1368        J_ASSERT(journal_current_handle() == handle);
1369
1370        if (is_handle_aborted(handle))
1371                err = -EIO;
1372        else {
1373                J_ASSERT(transaction->t_updates > 0);
1374                err = 0;
1375        }
1376
1377        if (--handle->h_ref > 0) {
1378                jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1,
1379                          handle->h_ref);
1380                return err;
1381        }
1382
1383        jbd_debug(4, "Handle %p going down\n", handle);
1384
1385        /*
1386         * Implement synchronous transaction batching.  If the handle
1387         * was synchronous, don't force a commit immediately.  Let's
1388         * yield and let another thread piggyback onto this transaction.
1389         * Keep doing that while new threads continue to arrive.
1390         * It doesn't cost much - we're about to run a commit and sleep
1391         * on IO anyway.  Speeds up many-threaded, many-dir operations
1392         * by 30x or more...
1393         *
1394         * We try and optimize the sleep time against what the underlying disk
1395         * can do, instead of having a static sleep time.  This is usefull for
1396         * the case where our storage is so fast that it is more optimal to go
1397         * ahead and force a flush and wait for the transaction to be committed
1398         * than it is to wait for an arbitrary amount of time for new writers to
1399         * join the transaction.  We achieve this by measuring how long it takes
1400         * to commit a transaction, and compare it with how long this
1401         * transaction has been running, and if run time < commit time then we
1402         * sleep for the delta and commit.  This greatly helps super fast disks
1403         * that would see slowdowns as more threads started doing fsyncs.
1404         *
1405         * But don't do this if this process was the most recent one to
1406         * perform a synchronous write.  We do this to detect the case where a
1407         * single process is doing a stream of sync writes.  No point in waiting
1408         * for joiners in that case.
1409         */
1410        pid = current->pid;
1411        if (handle->h_sync && journal->j_last_sync_writer != pid) {
1412                u64 commit_time, trans_time;
1413
1414                journal->j_last_sync_writer = pid;
1415
1416                spin_lock(&journal->j_state_lock);
1417                commit_time = journal->j_average_commit_time;
1418                spin_unlock(&journal->j_state_lock);
1419
1420                trans_time = ktime_to_ns(ktime_sub(ktime_get(),
1421                                                   transaction->t_start_time));
1422
1423                commit_time = min_t(u64, commit_time,
1424                                    1000*jiffies_to_usecs(1));
1425
1426                if (trans_time < commit_time) {
1427                        ktime_t expires = ktime_add_ns(ktime_get(),
1428                                                       commit_time);
1429                        set_current_state(TASK_UNINTERRUPTIBLE);
1430                        schedule_hrtimeout(&expires, HRTIMER_MODE_ABS);
1431                }
1432        }
1433
1434        if (handle->h_sync)
1435                transaction->t_synchronous_commit = 1;
1436        current->journal_info = NULL;
1437        spin_lock(&journal->j_state_lock);
1438        spin_lock(&transaction->t_handle_lock);
1439        transaction->t_outstanding_credits -= handle->h_buffer_credits;
1440        transaction->t_updates--;
1441        if (!transaction->t_updates) {
1442                wake_up(&journal->j_wait_updates);
1443                if (journal->j_barrier_count)
1444                        wake_up(&journal->j_wait_transaction_locked);
1445        }
1446
1447        /*
1448         * If the handle is marked SYNC, we need to set another commit
1449         * going!  We also want to force a commit if the current
1450         * transaction is occupying too much of the log, or if the
1451         * transaction is too old now.
1452         */
1453        if (handle->h_sync ||
1454                        transaction->t_outstanding_credits >
1455                                journal->j_max_transaction_buffers ||
1456                        time_after_eq(jiffies, transaction->t_expires)) {
1457                /* Do this even for aborted journals: an abort still
1458                 * completes the commit thread, it just doesn't write
1459                 * anything to disk. */
1460                tid_t tid = transaction->t_tid;
1461
1462                spin_unlock(&transaction->t_handle_lock);
1463                jbd_debug(2, "transaction too old, requesting commit for "
1464                                        "handle %p\n", handle);
1465                /* This is non-blocking */
1466                __log_start_commit(journal, transaction->t_tid);
1467                spin_unlock(&journal->j_state_lock);
1468
1469                /*
1470                 * Special case: JFS_SYNC synchronous updates require us
1471                 * to wait for the commit to complete.
1472                 */
1473                if (handle->h_sync && !(current->flags & PF_MEMALLOC))
1474                        err = log_wait_commit(journal, tid);
1475        } else {
1476                spin_unlock(&transaction->t_handle_lock);
1477                spin_unlock(&journal->j_state_lock);
1478        }
1479
1480        lock_map_release(&handle->h_lockdep_map);
1481
1482        jbd_free_handle(handle);
1483        return err;
1484}
1485
1486/**
1487 * int journal_force_commit() - force any uncommitted transactions
1488 * @journal: journal to force
1489 *
1490 * For synchronous operations: force any uncommitted transactions
1491 * to disk.  May seem kludgy, but it reuses all the handle batching
1492 * code in a very simple manner.
1493 */
1494int journal_force_commit(journal_t *journal)
1495{
1496        handle_t *handle;
1497        int ret;
1498
1499        handle = journal_start(journal, 1);
1500        if (IS_ERR(handle)) {
1501                ret = PTR_ERR(handle);
1502        } else {
1503                handle->h_sync = 1;
1504                ret = journal_stop(handle);
1505        }
1506        return ret;
1507}
1508
1509/*
1510 *
1511 * List management code snippets: various functions for manipulating the
1512 * transaction buffer lists.
1513 *
1514 */
1515
1516/*
1517 * Append a buffer to a transaction list, given the transaction's list head
1518 * pointer.
1519 *
1520 * j_list_lock is held.
1521 *
1522 * jbd_lock_bh_state(jh2bh(jh)) is held.
1523 */
1524
1525static inline void
1526__blist_add_buffer(struct journal_head **list, struct journal_head *jh)
1527{
1528        if (!*list) {
1529                jh->b_tnext = jh->b_tprev = jh;
1530                *list = jh;
1531        } else {
1532                /* Insert at the tail of the list to preserve order */
1533                struct journal_head *first = *list, *last = first->b_tprev;
1534                jh->b_tprev = last;
1535                jh->b_tnext = first;
1536                last->b_tnext = first->b_tprev = jh;
1537        }
1538}
1539
1540/*
1541 * Remove a buffer from a transaction list, given the transaction's list
1542 * head pointer.
1543 *
1544 * Called with j_list_lock held, and the journal may not be locked.
1545 *
1546 * jbd_lock_bh_state(jh2bh(jh)) is held.
1547 */
1548
1549static inline void
1550__blist_del_buffer(struct journal_head **list, struct journal_head *jh)
1551{
1552        if (*list == jh) {
1553                *list = jh->b_tnext;
1554                if (*list == jh)
1555                        *list = NULL;
1556        }
1557        jh->b_tprev->b_tnext = jh->b_tnext;
1558        jh->b_tnext->b_tprev = jh->b_tprev;
1559}
1560
1561/*
1562 * Remove a buffer from the appropriate transaction list.
1563 *
1564 * Note that this function can *change* the value of
1565 * bh->b_transaction->t_sync_datalist, t_buffers, t_forget,
1566 * t_iobuf_list, t_shadow_list, t_log_list or t_reserved_list.  If the caller
1567 * is holding onto a copy of one of thee pointers, it could go bad.
1568 * Generally the caller needs to re-read the pointer from the transaction_t.
1569 *
1570 * Called under j_list_lock.  The journal may not be locked.
1571 */
1572static void __journal_temp_unlink_buffer(struct journal_head *jh)
1573{
1574        struct journal_head **list = NULL;
1575        transaction_t *transaction;
1576        struct buffer_head *bh = jh2bh(jh);
1577
1578        J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
1579        transaction = jh->b_transaction;
1580        if (transaction)
1581                assert_spin_locked(&transaction->t_journal->j_list_lock);
1582
1583        J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
1584        if (jh->b_jlist != BJ_None)
1585                J_ASSERT_JH(jh, transaction != NULL);
1586
1587        switch (jh->b_jlist) {
1588        case BJ_None:
1589                return;
1590        case BJ_SyncData:
1591                list = &transaction->t_sync_datalist;
1592                break;
1593        case BJ_Metadata:
1594                transaction->t_nr_buffers--;
1595                J_ASSERT_JH(jh, transaction->t_nr_buffers >= 0);
1596                list = &transaction->t_buffers;
1597                break;
1598        case BJ_Forget:
1599                list = &transaction->t_forget;
1600                break;
1601        case BJ_IO:
1602                list = &transaction->t_iobuf_list;
1603                break;
1604        case BJ_Shadow:
1605                list = &transaction->t_shadow_list;
1606                break;
1607        case BJ_LogCtl:
1608                list = &transaction->t_log_list;
1609                break;
1610        case BJ_Reserved:
1611                list = &transaction->t_reserved_list;
1612                break;
1613        case BJ_Locked:
1614                list = &transaction->t_locked_list;
1615                break;
1616        }
1617
1618        __blist_del_buffer(list, jh);
1619        jh->b_jlist = BJ_None;
1620        if (test_clear_buffer_jbddirty(bh))
1621                mark_buffer_dirty(bh);  /* Expose it to the VM */
1622}
1623
1624void __journal_unfile_buffer(struct journal_head *jh)
1625{
1626        __journal_temp_unlink_buffer(jh);
1627        jh->b_transaction = NULL;
1628}
1629
1630void journal_unfile_buffer(journal_t *journal, struct journal_head *jh)
1631{
1632        jbd_lock_bh_state(jh2bh(jh));
1633        spin_lock(&journal->j_list_lock);
1634        __journal_unfile_buffer(jh);
1635        spin_unlock(&journal->j_list_lock);
1636        jbd_unlock_bh_state(jh2bh(jh));
1637}
1638
1639/*
1640 * Called from journal_try_to_free_buffers().
1641 *
1642 * Called under jbd_lock_bh_state(bh)
1643 */
1644static void
1645__journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
1646{
1647        struct journal_head *jh;
1648
1649        jh = bh2jh(bh);
1650
1651        if (buffer_locked(bh) || buffer_dirty(bh))
1652                goto out;
1653
1654        if (jh->b_next_transaction != NULL)
1655                goto out;
1656
1657        spin_lock(&journal->j_list_lock);
1658        if (jh->b_transaction != NULL && jh->b_cp_transaction == NULL) {
1659                if (jh->b_jlist == BJ_SyncData || jh->b_jlist == BJ_Locked) {
1660                        /* A written-back ordered data buffer */
1661                        JBUFFER_TRACE(jh, "release data");
1662                        __journal_unfile_buffer(jh);
1663                        journal_remove_journal_head(bh);
1664                        __brelse(bh);
1665                }
1666        } else if (jh->b_cp_transaction != NULL && jh->b_transaction == NULL) {
1667                /* written-back checkpointed metadata buffer */
1668                if (jh->b_jlist == BJ_None) {
1669                        JBUFFER_TRACE(jh, "remove from checkpoint list");
1670                        __journal_remove_checkpoint(jh);
1671                        journal_remove_journal_head(bh);
1672                        __brelse(bh);
1673                }
1674        }
1675        spin_unlock(&journal->j_list_lock);
1676out:
1677        return;
1678}
1679
1680/**
1681 * int journal_try_to_free_buffers() - try to free page buffers.
1682 * @journal: journal for operation
1683 * @page: to try and free
1684 * @gfp_mask: we use the mask to detect how hard should we try to release
1685 * buffers. If __GFP_WAIT and __GFP_FS is set, we wait for commit code to
1686 * release the buffers.
1687 *
1688 *
1689 * For all the buffers on this page,
1690 * if they are fully written out ordered data, move them onto BUF_CLEAN
1691 * so try_to_free_buffers() can reap them.
1692 *
1693 * This function returns non-zero if we wish try_to_free_buffers()
1694 * to be called. We do this if the page is releasable by try_to_free_buffers().
1695 * We also do it if the page has locked or dirty buffers and the caller wants
1696 * us to perform sync or async writeout.
1697 *
1698 * This complicates JBD locking somewhat.  We aren't protected by the
1699 * BKL here.  We wish to remove the buffer from its committing or
1700 * running transaction's ->t_datalist via __journal_unfile_buffer.
1701 *
1702 * This may *change* the value of transaction_t->t_datalist, so anyone
1703 * who looks at t_datalist needs to lock against this function.
1704 *
1705 * Even worse, someone may be doing a journal_dirty_data on this
1706 * buffer.  So we need to lock against that.  journal_dirty_data()
1707 * will come out of the lock with the buffer dirty, which makes it
1708 * ineligible for release here.
1709 *
1710 * Who else is affected by this?  hmm...  Really the only contender
1711 * is do_get_write_access() - it could be looking at the buffer while
1712 * journal_try_to_free_buffer() is changing its state.  But that
1713 * cannot happen because we never reallocate freed data as metadata
1714 * while the data is part of a transaction.  Yes?
1715 *
1716 * Return 0 on failure, 1 on success
1717 */
1718int journal_try_to_free_buffers(journal_t *journal,
1719                                struct page *page, gfp_t gfp_mask)
1720{
1721        struct buffer_head *head;
1722        struct buffer_head *bh;
1723        int ret = 0;
1724
1725        J_ASSERT(PageLocked(page));
1726
1727        head = page_buffers(page);
1728        bh = head;
1729        do {
1730                struct journal_head *jh;
1731
1732                /*
1733                 * We take our own ref against the journal_head here to avoid
1734                 * having to add tons of locking around each instance of
1735                 * journal_remove_journal_head() and journal_put_journal_head().
1736                 */
1737                jh = journal_grab_journal_head(bh);
1738                if (!jh)
1739                        continue;
1740
1741                jbd_lock_bh_state(bh);
1742                __journal_try_to_free_buffer(journal, bh);
1743                journal_put_journal_head(jh);
1744                jbd_unlock_bh_state(bh);
1745                if (buffer_jbd(bh))
1746                        goto busy;
1747        } while ((bh = bh->b_this_page) != head);
1748
1749        ret = try_to_free_buffers(page);
1750
1751busy:
1752        return ret;
1753}
1754
1755/*
1756 * This buffer is no longer needed.  If it is on an older transaction's
1757 * checkpoint list we need to record it on this transaction's forget list
1758 * to pin this buffer (and hence its checkpointing transaction) down until
1759 * this transaction commits.  If the buffer isn't on a checkpoint list, we
1760 * release it.
1761 * Returns non-zero if JBD no longer has an interest in the buffer.
1762 *
1763 * Called under j_list_lock.
1764 *
1765 * Called under jbd_lock_bh_state(bh).
1766 */
1767static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
1768{
1769        int may_free = 1;
1770        struct buffer_head *bh = jh2bh(jh);
1771
1772        __journal_unfile_buffer(jh);
1773
1774        if (jh->b_cp_transaction) {
1775                JBUFFER_TRACE(jh, "on running+cp transaction");
1776                /*
1777                 * We don't want to write the buffer anymore, clear the
1778                 * bit so that we don't confuse checks in
1779                 * __journal_file_buffer
1780                 */
1781                clear_buffer_dirty(bh);
1782                __journal_file_buffer(jh, transaction, BJ_Forget);
1783                may_free = 0;
1784        } else {
1785                JBUFFER_TRACE(jh, "on running transaction");
1786                journal_remove_journal_head(bh);
1787                __brelse(bh);
1788        }
1789        return may_free;
1790}
1791
1792/*
1793 * journal_invalidatepage
1794 *
1795 * This code is tricky.  It has a number of cases to deal with.
1796 *
1797 * There are two invariants which this code relies on:
1798 *
1799 * i_size must be updated on disk before we start calling invalidatepage on the
1800 * data.
1801 *
1802 *  This is done in ext3 by defining an ext3_setattr method which
1803 *  updates i_size before truncate gets going.  By maintaining this
1804 *  invariant, we can be sure that it is safe to throw away any buffers
1805 *  attached to the current transaction: once the transaction commits,
1806 *  we know that the data will not be needed.
1807 *
1808 *  Note however that we can *not* throw away data belonging to the
1809 *  previous, committing transaction!
1810 *
1811 * Any disk blocks which *are* part of the previous, committing
1812 * transaction (and which therefore cannot be discarded immediately) are
1813 * not going to be reused in the new running transaction
1814 *
1815 *  The bitmap committed_data images guarantee this: any block which is
1816 *  allocated in one transaction and removed in the next will be marked
1817 *  as in-use in the committed_data bitmap, so cannot be reused until
1818 *  the next transaction to delete the block commits.  This means that
1819 *  leaving committing buffers dirty is quite safe: the disk blocks
1820 *  cannot be reallocated to a different file and so buffer aliasing is
1821 *  not possible.
1822 *
1823 *
1824 * The above applies mainly to ordered data mode.  In writeback mode we
1825 * don't make guarantees about the order in which data hits disk --- in
1826 * particular we don't guarantee that new dirty data is flushed before
1827 * transaction commit --- so it is always safe just to discard data
1828 * immediately in that mode.  --sct
1829 */
1830
1831/*
1832 * The journal_unmap_buffer helper function returns zero if the buffer
1833 * concerned remains pinned as an anonymous buffer belonging to an older
1834 * transaction.
1835 *
1836 * We're outside-transaction here.  Either or both of j_running_transaction
1837 * and j_committing_transaction may be NULL.
1838 */
1839static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
1840{
1841        transaction_t *transaction;
1842        struct journal_head *jh;
1843        int may_free = 1;
1844        int ret;
1845
1846        BUFFER_TRACE(bh, "entry");
1847
1848        /*
1849         * It is safe to proceed here without the j_list_lock because the
1850         * buffers cannot be stolen by try_to_free_buffers as long as we are
1851         * holding the page lock. --sct
1852         */
1853
1854        if (!buffer_jbd(bh))
1855                goto zap_buffer_unlocked;
1856
1857        spin_lock(&journal->j_state_lock);
1858        jbd_lock_bh_state(bh);
1859        spin_lock(&journal->j_list_lock);
1860
1861        jh = journal_grab_journal_head(bh);
1862        if (!jh)
1863                goto zap_buffer_no_jh;
1864
1865        /*
1866         * We cannot remove the buffer from checkpoint lists until the
1867         * transaction adding inode to orphan list (let's call it T)
1868         * is committed.  Otherwise if the transaction changing the
1869         * buffer would be cleaned from the journal before T is
1870         * committed, a crash will cause that the correct contents of
1871         * the buffer will be lost.  On the other hand we have to
1872         * clear the buffer dirty bit at latest at the moment when the
1873         * transaction marking the buffer as freed in the filesystem
1874         * structures is committed because from that moment on the
1875         * buffer can be reallocated and used by a different page.
1876         * Since the block hasn't been freed yet but the inode has
1877         * already been added to orphan list, it is safe for us to add
1878         * the buffer to BJ_Forget list of the newest transaction.
1879         */
1880        transaction = jh->b_transaction;
1881        if (transaction == NULL) {
1882                /* First case: not on any transaction.  If it
1883                 * has no checkpoint link, then we can zap it:
1884                 * it's a writeback-mode buffer so we don't care
1885                 * if it hits disk safely. */
1886                if (!jh->b_cp_transaction) {
1887                        JBUFFER_TRACE(jh, "not on any transaction: zap");
1888                        goto zap_buffer;
1889                }
1890
1891                if (!buffer_dirty(bh)) {
1892                        /* bdflush has written it.  We can drop it now */
1893                        goto zap_buffer;
1894                }
1895
1896                /* OK, it must be in the journal but still not
1897                 * written fully to disk: it's metadata or
1898                 * journaled data... */
1899
1900                if (journal->j_running_transaction) {
1901                        /* ... and once the current transaction has
1902                         * committed, the buffer won't be needed any
1903                         * longer. */
1904                        JBUFFER_TRACE(jh, "checkpointed: add to BJ_Forget");
1905                        ret = __dispose_buffer(jh,
1906                                        journal->j_running_transaction);
1907                        journal_put_journal_head(jh);
1908                        spin_unlock(&journal->j_list_lock);
1909                        jbd_unlock_bh_state(bh);
1910                        spin_unlock(&journal->j_state_lock);
1911                        return ret;
1912                } else {
1913                        /* There is no currently-running transaction. So the
1914                         * orphan record which we wrote for this file must have
1915                         * passed into commit.  We must attach this buffer to
1916                         * the committing transaction, if it exists. */
1917                        if (journal->j_committing_transaction) {
1918                                JBUFFER_TRACE(jh, "give to committing trans");
1919                                ret = __dispose_buffer(jh,
1920                                        journal->j_committing_transaction);
1921                                journal_put_journal_head(jh);
1922                                spin_unlock(&journal->j_list_lock);
1923                                jbd_unlock_bh_state(bh);
1924                                spin_unlock(&journal->j_state_lock);
1925                                return ret;
1926                        } else {
1927                                /* The orphan record's transaction has
1928                                 * committed.  We can cleanse this buffer */
1929                                clear_buffer_jbddirty(bh);
1930                                goto zap_buffer;
1931                        }
1932                }
1933        } else if (transaction == journal->j_committing_transaction) {
1934                JBUFFER_TRACE(jh, "on committing transaction");
1935                if (jh->b_jlist == BJ_Locked) {
1936                        /*
1937                         * The buffer is on the committing transaction's locked
1938                         * list.  We have the buffer locked, so I/O has
1939                         * completed.  So we can nail the buffer now.
1940                         */
1941                        may_free = __dispose_buffer(jh, transaction);
1942                        goto zap_buffer;
1943                }
1944                /*
1945                 * The buffer is committing, we simply cannot touch
1946                 * it. So we just set j_next_transaction to the
1947                 * running transaction (if there is one) and mark
1948                 * buffer as freed so that commit code knows it should
1949                 * clear dirty bits when it is done with the buffer.
1950                 */
1951                set_buffer_freed(bh);
1952                if (journal->j_running_transaction && buffer_jbddirty(bh))
1953                        jh->b_next_transaction = journal->j_running_transaction;
1954                journal_put_journal_head(jh);
1955                spin_unlock(&journal->j_list_lock);
1956                jbd_unlock_bh_state(bh);
1957                spin_unlock(&journal->j_state_lock);
1958                return 0;
1959        } else {
1960                /* Good, the buffer belongs to the running transaction.
1961                 * We are writing our own transaction's data, not any
1962                 * previous one's, so it is safe to throw it away
1963                 * (remember that we expect the filesystem to have set
1964                 * i_size already for this truncate so recovery will not
1965                 * expose the disk blocks we are discarding here.) */
1966                J_ASSERT_JH(jh, transaction == journal->j_running_transaction);
1967                JBUFFER_TRACE(jh, "on running transaction");
1968                may_free = __dispose_buffer(jh, transaction);
1969        }
1970
1971zap_buffer:
1972        journal_put_journal_head(jh);
1973zap_buffer_no_jh:
1974        spin_unlock(&journal->j_list_lock);
1975        jbd_unlock_bh_state(bh);
1976        spin_unlock(&journal->j_state_lock);
1977zap_buffer_unlocked:
1978        clear_buffer_dirty(bh);
1979        J_ASSERT_BH(bh, !buffer_jbddirty(bh));
1980        clear_buffer_mapped(bh);
1981        clear_buffer_req(bh);
1982        clear_buffer_new(bh);
1983        bh->b_bdev = NULL;
1984        return may_free;
1985}
1986
1987/**
1988 * void journal_invalidatepage() - invalidate a journal page
1989 * @journal: journal to use for flush
1990 * @page:    page to flush
1991 * @offset:  length of page to invalidate.
1992 *
1993 * Reap page buffers containing data after offset in page.
1994 */
1995void journal_invalidatepage(journal_t *journal,
1996                      struct page *page,
1997                      unsigned long offset)
1998{
1999        struct buffer_head *head, *bh, *next;
2000        unsigned int curr_off = 0;
2001        int may_free = 1;
2002
2003        if (!PageLocked(page))
2004                BUG();
2005        if (!page_has_buffers(page))
2006                return;
2007
2008        /* We will potentially be playing with lists other than just the
2009         * data lists (especially for journaled data mode), so be
2010         * cautious in our locking. */
2011
2012        head = bh = page_buffers(page);
2013        do {
2014                unsigned int next_off = curr_off + bh->b_size;
2015                next = bh->b_this_page;
2016
2017                if (offset <= curr_off) {
2018                        /* This block is wholly outside the truncation point */
2019                        lock_buffer(bh);
2020                        may_free &= journal_unmap_buffer(journal, bh);
2021                        unlock_buffer(bh);
2022                }
2023                curr_off = next_off;
2024                bh = next;
2025
2026        } while (bh != head);
2027
2028        if (!offset) {
2029                if (may_free && try_to_free_buffers(page))
2030                        J_ASSERT(!page_has_buffers(page));
2031        }
2032}
2033
2034/*
2035 * File a buffer on the given transaction list.
2036 */
2037void __journal_file_buffer(struct journal_head *jh,
2038                        transaction_t *transaction, int jlist)
2039{
2040        struct journal_head **list = NULL;
2041        int was_dirty = 0;
2042        struct buffer_head *bh = jh2bh(jh);
2043
2044        J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
2045        assert_spin_locked(&transaction->t_journal->j_list_lock);
2046
2047        J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
2048        J_ASSERT_JH(jh, jh->b_transaction == transaction ||
2049                                jh->b_transaction == NULL);
2050
2051        if (jh->b_transaction && jh->b_jlist == jlist)
2052                return;
2053
2054        if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
2055            jlist == BJ_Shadow || jlist == BJ_Forget) {
2056                /*
2057                 * For metadata buffers, we track dirty bit in buffer_jbddirty
2058                 * instead of buffer_dirty. We should not see a dirty bit set
2059                 * here because we clear it in do_get_write_access but e.g.
2060                 * tune2fs can modify the sb and set the dirty bit at any time
2061                 * so we try to gracefully handle that.
2062                 */
2063                if (buffer_dirty(bh))
2064                        warn_dirty_buffer(bh);
2065                if (test_clear_buffer_dirty(bh) ||
2066                    test_clear_buffer_jbddirty(bh))
2067                        was_dirty = 1;
2068        }
2069
2070        if (jh->b_transaction)
2071                __journal_temp_unlink_buffer(jh);
2072        jh->b_transaction = transaction;
2073
2074        switch (jlist) {
2075        case BJ_None:
2076                J_ASSERT_JH(jh, !jh->b_committed_data);
2077                J_ASSERT_JH(jh, !jh->b_frozen_data);
2078                return;
2079        case BJ_SyncData:
2080                list = &transaction->t_sync_datalist;
2081                break;
2082        case BJ_Metadata:
2083                transaction->t_nr_buffers++;
2084                list = &transaction->t_buffers;
2085                break;
2086        case BJ_Forget:
2087                list = &transaction->t_forget;
2088                break;
2089        case BJ_IO:
2090                list = &transaction->t_iobuf_list;
2091                break;
2092        case BJ_Shadow:
2093                list = &transaction->t_shadow_list;
2094                break;
2095        case BJ_LogCtl:
2096                list = &transaction->t_log_list;
2097                break;
2098        case BJ_Reserved:
2099                list = &transaction->t_reserved_list;
2100                break;
2101        case BJ_Locked:
2102                list =  &transaction->t_locked_list;
2103                break;
2104        }
2105
2106        __blist_add_buffer(list, jh);
2107        jh->b_jlist = jlist;
2108
2109        if (was_dirty)
2110                set_buffer_jbddirty(bh);
2111}
2112
2113void journal_file_buffer(struct journal_head *jh,
2114                                transaction_t *transaction, int jlist)
2115{
2116        jbd_lock_bh_state(jh2bh(jh));
2117        spin_lock(&transaction->t_journal->j_list_lock);
2118        __journal_file_buffer(jh, transaction, jlist);
2119        spin_unlock(&transaction->t_journal->j_list_lock);
2120        jbd_unlock_bh_state(jh2bh(jh));
2121}
2122
2123/*
2124 * Remove a buffer from its current buffer list in preparation for
2125 * dropping it from its current transaction entirely.  If the buffer has
2126 * already started to be used by a subsequent transaction, refile the
2127 * buffer on that transaction's metadata list.
2128 *
2129 * Called under journal->j_list_lock
2130 *
2131 * Called under jbd_lock_bh_state(jh2bh(jh))
2132 */
2133void __journal_refile_buffer(struct journal_head *jh)
2134{
2135        int was_dirty, jlist;
2136        struct buffer_head *bh = jh2bh(jh);
2137
2138        J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
2139        if (jh->b_transaction)
2140                assert_spin_locked(&jh->b_transaction->t_journal->j_list_lock);
2141
2142        /* If the buffer is now unused, just drop it. */
2143        if (jh->b_next_transaction == NULL) {
2144                __journal_unfile_buffer(jh);
2145                return;
2146        }
2147
2148        /*
2149         * It has been modified by a later transaction: add it to the new
2150         * transaction's metadata list.
2151         */
2152
2153        was_dirty = test_clear_buffer_jbddirty(bh);
2154        __journal_temp_unlink_buffer(jh);
2155        jh->b_transaction = jh->b_next_transaction;
2156        jh->b_next_transaction = NULL;
2157        if (buffer_freed(bh))
2158                jlist = BJ_Forget;
2159        else if (jh->b_modified)
2160                jlist = BJ_Metadata;
2161        else
2162                jlist = BJ_Reserved;
2163        __journal_file_buffer(jh, jh->b_transaction, jlist);
2164        J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING);
2165
2166        if (was_dirty)
2167                set_buffer_jbddirty(bh);
2168}
2169
2170/*
2171 * For the unlocked version of this call, also make sure that any
2172 * hanging journal_head is cleaned up if necessary.
2173 *
2174 * __journal_refile_buffer is usually called as part of a single locked
2175 * operation on a buffer_head, in which the caller is probably going to
2176 * be hooking the journal_head onto other lists.  In that case it is up
2177 * to the caller to remove the journal_head if necessary.  For the
2178 * unlocked journal_refile_buffer call, the caller isn't going to be
2179 * doing anything else to the buffer so we need to do the cleanup
2180 * ourselves to avoid a jh leak.
2181 *
2182 * *** The journal_head may be freed by this call! ***
2183 */
2184void journal_refile_buffer(journal_t *journal, struct journal_head *jh)
2185{
2186        struct buffer_head *bh = jh2bh(jh);
2187
2188        jbd_lock_bh_state(bh);
2189        spin_lock(&journal->j_list_lock);
2190
2191        __journal_refile_buffer(jh);
2192        jbd_unlock_bh_state(bh);
2193        journal_remove_journal_head(bh);
2194
2195        spin_unlock(&journal->j_list_lock);
2196        __brelse(bh);
2197}
2198
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