linux/fs/jbd2/commit.c
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   1/*
   2 * linux/fs/jbd2/commit.c
   3 *
   4 * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
   5 *
   6 * Copyright 1998 Red Hat corp --- All Rights Reserved
   7 *
   8 * This file is part of the Linux kernel and is made available under
   9 * the terms of the GNU General Public License, version 2, or at your
  10 * option, any later version, incorporated herein by reference.
  11 *
  12 * Journal commit routines for the generic filesystem journaling code;
  13 * part of the ext2fs journaling system.
  14 */
  15
  16#include <linux/time.h>
  17#include <linux/fs.h>
  18#include <linux/jbd2.h>
  19#include <linux/errno.h>
  20#include <linux/slab.h>
  21#include <linux/mm.h>
  22#include <linux/pagemap.h>
  23#include <linux/jiffies.h>
  24#include <linux/crc32.h>
  25#include <linux/writeback.h>
  26#include <linux/backing-dev.h>
  27#include <linux/bio.h>
  28#include <linux/blkdev.h>
  29#include <linux/bitops.h>
  30#include <trace/events/jbd2.h>
  31#include <asm/system.h>
  32
  33/*
  34 * Default IO end handler for temporary BJ_IO buffer_heads.
  35 */
  36static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
  37{
  38        BUFFER_TRACE(bh, "");
  39        if (uptodate)
  40                set_buffer_uptodate(bh);
  41        else
  42                clear_buffer_uptodate(bh);
  43        unlock_buffer(bh);
  44}
  45
  46/*
  47 * When an ext4 file is truncated, it is possible that some pages are not
  48 * successfully freed, because they are attached to a committing transaction.
  49 * After the transaction commits, these pages are left on the LRU, with no
  50 * ->mapping, and with attached buffers.  These pages are trivially reclaimable
  51 * by the VM, but their apparent absence upsets the VM accounting, and it makes
  52 * the numbers in /proc/meminfo look odd.
  53 *
  54 * So here, we have a buffer which has just come off the forget list.  Look to
  55 * see if we can strip all buffers from the backing page.
  56 *
  57 * Called under lock_journal(), and possibly under journal_datalist_lock.  The
  58 * caller provided us with a ref against the buffer, and we drop that here.
  59 */
  60static void release_buffer_page(struct buffer_head *bh)
  61{
  62        struct page *page;
  63
  64        if (buffer_dirty(bh))
  65                goto nope;
  66        if (atomic_read(&bh->b_count) != 1)
  67                goto nope;
  68        page = bh->b_page;
  69        if (!page)
  70                goto nope;
  71        if (page->mapping)
  72                goto nope;
  73
  74        /* OK, it's a truncated page */
  75        if (!trylock_page(page))
  76                goto nope;
  77
  78        page_cache_get(page);
  79        __brelse(bh);
  80        try_to_free_buffers(page);
  81        unlock_page(page);
  82        page_cache_release(page);
  83        return;
  84
  85nope:
  86        __brelse(bh);
  87}
  88
  89/*
  90 * Done it all: now submit the commit record.  We should have
  91 * cleaned up our previous buffers by now, so if we are in abort
  92 * mode we can now just skip the rest of the journal write
  93 * entirely.
  94 *
  95 * Returns 1 if the journal needs to be aborted or 0 on success
  96 */
  97static int journal_submit_commit_record(journal_t *journal,
  98                                        transaction_t *commit_transaction,
  99                                        struct buffer_head **cbh,
 100                                        __u32 crc32_sum)
 101{
 102        struct journal_head *descriptor;
 103        struct commit_header *tmp;
 104        struct buffer_head *bh;
 105        int ret;
 106        struct timespec now = current_kernel_time();
 107
 108        if (is_journal_aborted(journal))
 109                return 0;
 110
 111        descriptor = jbd2_journal_get_descriptor_buffer(journal);
 112        if (!descriptor)
 113                return 1;
 114
 115        bh = jh2bh(descriptor);
 116
 117        tmp = (struct commit_header *)bh->b_data;
 118        tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
 119        tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
 120        tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 121        tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
 122        tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);
 123
 124        if (JBD2_HAS_COMPAT_FEATURE(journal,
 125                                    JBD2_FEATURE_COMPAT_CHECKSUM)) {
 126                tmp->h_chksum_type      = JBD2_CRC32_CHKSUM;
 127                tmp->h_chksum_size      = JBD2_CRC32_CHKSUM_SIZE;
 128                tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
 129        }
 130
 131        JBUFFER_TRACE(descriptor, "submit commit block");
 132        lock_buffer(bh);
 133        clear_buffer_dirty(bh);
 134        set_buffer_uptodate(bh);
 135        bh->b_end_io = journal_end_buffer_io_sync;
 136
 137        if (journal->j_flags & JBD2_BARRIER &&
 138            !JBD2_HAS_INCOMPAT_FEATURE(journal,
 139                                       JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT))
 140                ret = submit_bh(WRITE_SYNC_PLUG | WRITE_FLUSH_FUA, bh);
 141        else
 142                ret = submit_bh(WRITE_SYNC_PLUG, bh);
 143
 144        *cbh = bh;
 145        return ret;
 146}
 147
 148/*
 149 * This function along with journal_submit_commit_record
 150 * allows to write the commit record asynchronously.
 151 */
 152static int journal_wait_on_commit_record(journal_t *journal,
 153                                         struct buffer_head *bh)
 154{
 155        int ret = 0;
 156
 157        clear_buffer_dirty(bh);
 158        wait_on_buffer(bh);
 159
 160        if (unlikely(!buffer_uptodate(bh)))
 161                ret = -EIO;
 162        put_bh(bh);            /* One for getblk() */
 163        jbd2_journal_put_journal_head(bh2jh(bh));
 164
 165        return ret;
 166}
 167
 168/*
 169 * write the filemap data using writepage() address_space_operations.
 170 * We don't do block allocation here even for delalloc. We don't
 171 * use writepages() because with dealyed allocation we may be doing
 172 * block allocation in writepages().
 173 */
 174static int journal_submit_inode_data_buffers(struct address_space *mapping)
 175{
 176        int ret;
 177        struct writeback_control wbc = {
 178                .sync_mode =  WB_SYNC_ALL,
 179                .nr_to_write = mapping->nrpages * 2,
 180                .range_start = 0,
 181                .range_end = i_size_read(mapping->host),
 182        };
 183
 184        ret = generic_writepages(mapping, &wbc);
 185        return ret;
 186}
 187
 188/*
 189 * Submit all the data buffers of inode associated with the transaction to
 190 * disk.
 191 *
 192 * We are in a committing transaction. Therefore no new inode can be added to
 193 * our inode list. We use JI_COMMIT_RUNNING flag to protect inode we currently
 194 * operate on from being released while we write out pages.
 195 */
 196static int journal_submit_data_buffers(journal_t *journal,
 197                transaction_t *commit_transaction)
 198{
 199        struct jbd2_inode *jinode;
 200        int err, ret = 0;
 201        struct address_space *mapping;
 202
 203        spin_lock(&journal->j_list_lock);
 204        list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 205                mapping = jinode->i_vfs_inode->i_mapping;
 206                set_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 207                spin_unlock(&journal->j_list_lock);
 208                /*
 209                 * submit the inode data buffers. We use writepage
 210                 * instead of writepages. Because writepages can do
 211                 * block allocation  with delalloc. We need to write
 212                 * only allocated blocks here.
 213                 */
 214                trace_jbd2_submit_inode_data(jinode->i_vfs_inode);
 215                err = journal_submit_inode_data_buffers(mapping);
 216                if (!ret)
 217                        ret = err;
 218                spin_lock(&journal->j_list_lock);
 219                J_ASSERT(jinode->i_transaction == commit_transaction);
 220                commit_transaction->t_flushed_data_blocks = 1;
 221                clear_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 222                smp_mb__after_clear_bit();
 223                wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 224        }
 225        spin_unlock(&journal->j_list_lock);
 226        return ret;
 227}
 228
 229/*
 230 * Wait for data submitted for writeout, refile inodes to proper
 231 * transaction if needed.
 232 *
 233 */
 234static int journal_finish_inode_data_buffers(journal_t *journal,
 235                transaction_t *commit_transaction)
 236{
 237        struct jbd2_inode *jinode, *next_i;
 238        int err, ret = 0;
 239
 240        /* For locking, see the comment in journal_submit_data_buffers() */
 241        spin_lock(&journal->j_list_lock);
 242        list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 243                set_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 244                spin_unlock(&journal->j_list_lock);
 245                err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
 246                if (err) {
 247                        /*
 248                         * Because AS_EIO is cleared by
 249                         * filemap_fdatawait_range(), set it again so
 250                         * that user process can get -EIO from fsync().
 251                         */
 252                        set_bit(AS_EIO,
 253                                &jinode->i_vfs_inode->i_mapping->flags);
 254
 255                        if (!ret)
 256                                ret = err;
 257                }
 258                spin_lock(&journal->j_list_lock);
 259                clear_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 260                smp_mb__after_clear_bit();
 261                wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 262        }
 263
 264        /* Now refile inode to proper lists */
 265        list_for_each_entry_safe(jinode, next_i,
 266                                 &commit_transaction->t_inode_list, i_list) {
 267                list_del(&jinode->i_list);
 268                if (jinode->i_next_transaction) {
 269                        jinode->i_transaction = jinode->i_next_transaction;
 270                        jinode->i_next_transaction = NULL;
 271                        list_add(&jinode->i_list,
 272                                &jinode->i_transaction->t_inode_list);
 273                } else {
 274                        jinode->i_transaction = NULL;
 275                }
 276        }
 277        spin_unlock(&journal->j_list_lock);
 278
 279        return ret;
 280}
 281
 282static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 283{
 284        struct page *page = bh->b_page;
 285        char *addr;
 286        __u32 checksum;
 287
 288        addr = kmap_atomic(page, KM_USER0);
 289        checksum = crc32_be(crc32_sum,
 290                (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
 291        kunmap_atomic(addr, KM_USER0);
 292
 293        return checksum;
 294}
 295
 296static void write_tag_block(int tag_bytes, journal_block_tag_t *tag,
 297                                   unsigned long long block)
 298{
 299        tag->t_blocknr = cpu_to_be32(block & (u32)~0);
 300        if (tag_bytes > JBD2_TAG_SIZE32)
 301                tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
 302}
 303
 304/*
 305 * jbd2_journal_commit_transaction
 306 *
 307 * The primary function for committing a transaction to the log.  This
 308 * function is called by the journal thread to begin a complete commit.
 309 */
 310void jbd2_journal_commit_transaction(journal_t *journal)
 311{
 312        struct transaction_stats_s stats;
 313        transaction_t *commit_transaction;
 314        struct journal_head *jh, *new_jh, *descriptor;
 315        struct buffer_head **wbuf = journal->j_wbuf;
 316        int bufs;
 317        int flags;
 318        int err;
 319        unsigned long long blocknr;
 320        ktime_t start_time;
 321        u64 commit_time;
 322        char *tagp = NULL;
 323        journal_header_t *header;
 324        journal_block_tag_t *tag = NULL;
 325        int space_left = 0;
 326        int first_tag = 0;
 327        int tag_flag;
 328        int i, to_free = 0;
 329        int tag_bytes = journal_tag_bytes(journal);
 330        struct buffer_head *cbh = NULL; /* For transactional checksums */
 331        __u32 crc32_sum = ~0;
 332        int write_op = WRITE_SYNC;
 333
 334        /*
 335         * First job: lock down the current transaction and wait for
 336         * all outstanding updates to complete.
 337         */
 338
 339#ifdef COMMIT_STATS
 340        spin_lock(&journal->j_list_lock);
 341        summarise_journal_usage(journal);
 342        spin_unlock(&journal->j_list_lock);
 343#endif
 344
 345        /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 346        if (journal->j_flags & JBD2_FLUSHED) {
 347                jbd_debug(3, "super block updated\n");
 348                jbd2_journal_update_superblock(journal, 1);
 349        } else {
 350                jbd_debug(3, "superblock not updated\n");
 351        }
 352
 353        J_ASSERT(journal->j_running_transaction != NULL);
 354        J_ASSERT(journal->j_committing_transaction == NULL);
 355
 356        commit_transaction = journal->j_running_transaction;
 357        J_ASSERT(commit_transaction->t_state == T_RUNNING);
 358
 359        trace_jbd2_start_commit(journal, commit_transaction);
 360        jbd_debug(1, "JBD: starting commit of transaction %d\n",
 361                        commit_transaction->t_tid);
 362
 363        write_lock(&journal->j_state_lock);
 364        commit_transaction->t_state = T_LOCKED;
 365
 366        /*
 367         * Use plugged writes here, since we want to submit several before
 368         * we unplug the device. We don't do explicit unplugging in here,
 369         * instead we rely on sync_buffer() doing the unplug for us.
 370         */
 371        if (commit_transaction->t_synchronous_commit)
 372                write_op = WRITE_SYNC_PLUG;
 373        trace_jbd2_commit_locking(journal, commit_transaction);
 374        stats.run.rs_wait = commit_transaction->t_max_wait;
 375        stats.run.rs_locked = jiffies;
 376        stats.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 377                                              stats.run.rs_locked);
 378
 379        spin_lock(&commit_transaction->t_handle_lock);
 380        while (atomic_read(&commit_transaction->t_updates)) {
 381                DEFINE_WAIT(wait);
 382
 383                prepare_to_wait(&journal->j_wait_updates, &wait,
 384                                        TASK_UNINTERRUPTIBLE);
 385                if (atomic_read(&commit_transaction->t_updates)) {
 386                        spin_unlock(&commit_transaction->t_handle_lock);
 387                        write_unlock(&journal->j_state_lock);
 388                        schedule();
 389                        write_lock(&journal->j_state_lock);
 390                        spin_lock(&commit_transaction->t_handle_lock);
 391                }
 392                finish_wait(&journal->j_wait_updates, &wait);
 393        }
 394        spin_unlock(&commit_transaction->t_handle_lock);
 395
 396        J_ASSERT (atomic_read(&commit_transaction->t_outstanding_credits) <=
 397                        journal->j_max_transaction_buffers);
 398
 399        /*
 400         * First thing we are allowed to do is to discard any remaining
 401         * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 402         * that there are no such buffers: if a large filesystem
 403         * operation like a truncate needs to split itself over multiple
 404         * transactions, then it may try to do a jbd2_journal_restart() while
 405         * there are still BJ_Reserved buffers outstanding.  These must
 406         * be released cleanly from the current transaction.
 407         *
 408         * In this case, the filesystem must still reserve write access
 409         * again before modifying the buffer in the new transaction, but
 410         * we do not require it to remember exactly which old buffers it
 411         * has reserved.  This is consistent with the existing behaviour
 412         * that multiple jbd2_journal_get_write_access() calls to the same
 413         * buffer are perfectly permissable.
 414         */
 415        while (commit_transaction->t_reserved_list) {
 416                jh = commit_transaction->t_reserved_list;
 417                JBUFFER_TRACE(jh, "reserved, unused: refile");
 418                /*
 419                 * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 420                 * leave undo-committed data.
 421                 */
 422                if (jh->b_committed_data) {
 423                        struct buffer_head *bh = jh2bh(jh);
 424
 425                        jbd_lock_bh_state(bh);
 426                        jbd2_free(jh->b_committed_data, bh->b_size);
 427                        jh->b_committed_data = NULL;
 428                        jbd_unlock_bh_state(bh);
 429                }
 430                jbd2_journal_refile_buffer(journal, jh);
 431        }
 432
 433        /*
 434         * Now try to drop any written-back buffers from the journal's
 435         * checkpoint lists.  We do this *before* commit because it potentially
 436         * frees some memory
 437         */
 438        spin_lock(&journal->j_list_lock);
 439        __jbd2_journal_clean_checkpoint_list(journal);
 440        spin_unlock(&journal->j_list_lock);
 441
 442        jbd_debug (3, "JBD: commit phase 1\n");
 443
 444        /*
 445         * Switch to a new revoke table.
 446         */
 447        jbd2_journal_switch_revoke_table(journal);
 448
 449        trace_jbd2_commit_flushing(journal, commit_transaction);
 450        stats.run.rs_flushing = jiffies;
 451        stats.run.rs_locked = jbd2_time_diff(stats.run.rs_locked,
 452                                             stats.run.rs_flushing);
 453
 454        commit_transaction->t_state = T_FLUSH;
 455        journal->j_committing_transaction = commit_transaction;
 456        journal->j_running_transaction = NULL;
 457        start_time = ktime_get();
 458        commit_transaction->t_log_start = journal->j_head;
 459        wake_up(&journal->j_wait_transaction_locked);
 460        write_unlock(&journal->j_state_lock);
 461
 462        jbd_debug (3, "JBD: commit phase 2\n");
 463
 464        /*
 465         * Now start flushing things to disk, in the order they appear
 466         * on the transaction lists.  Data blocks go first.
 467         */
 468        err = journal_submit_data_buffers(journal, commit_transaction);
 469        if (err)
 470                jbd2_journal_abort(journal, err);
 471
 472        jbd2_journal_write_revoke_records(journal, commit_transaction,
 473                                          write_op);
 474
 475        jbd_debug(3, "JBD: commit phase 2\n");
 476
 477        /*
 478         * Way to go: we have now written out all of the data for a
 479         * transaction!  Now comes the tricky part: we need to write out
 480         * metadata.  Loop over the transaction's entire buffer list:
 481         */
 482        write_lock(&journal->j_state_lock);
 483        commit_transaction->t_state = T_COMMIT;
 484        write_unlock(&journal->j_state_lock);
 485
 486        trace_jbd2_commit_logging(journal, commit_transaction);
 487        stats.run.rs_logging = jiffies;
 488        stats.run.rs_flushing = jbd2_time_diff(stats.run.rs_flushing,
 489                                               stats.run.rs_logging);
 490        stats.run.rs_blocks =
 491                atomic_read(&commit_transaction->t_outstanding_credits);
 492        stats.run.rs_blocks_logged = 0;
 493
 494        J_ASSERT(commit_transaction->t_nr_buffers <=
 495                 atomic_read(&commit_transaction->t_outstanding_credits));
 496
 497        err = 0;
 498        descriptor = NULL;
 499        bufs = 0;
 500        while (commit_transaction->t_buffers) {
 501
 502                /* Find the next buffer to be journaled... */
 503
 504                jh = commit_transaction->t_buffers;
 505
 506                /* If we're in abort mode, we just un-journal the buffer and
 507                   release it. */
 508
 509                if (is_journal_aborted(journal)) {
 510                        clear_buffer_jbddirty(jh2bh(jh));
 511                        JBUFFER_TRACE(jh, "journal is aborting: refile");
 512                        jbd2_buffer_abort_trigger(jh,
 513                                                  jh->b_frozen_data ?
 514                                                  jh->b_frozen_triggers :
 515                                                  jh->b_triggers);
 516                        jbd2_journal_refile_buffer(journal, jh);
 517                        /* If that was the last one, we need to clean up
 518                         * any descriptor buffers which may have been
 519                         * already allocated, even if we are now
 520                         * aborting. */
 521                        if (!commit_transaction->t_buffers)
 522                                goto start_journal_io;
 523                        continue;
 524                }
 525
 526                /* Make sure we have a descriptor block in which to
 527                   record the metadata buffer. */
 528
 529                if (!descriptor) {
 530                        struct buffer_head *bh;
 531
 532                        J_ASSERT (bufs == 0);
 533
 534                        jbd_debug(4, "JBD: get descriptor\n");
 535
 536                        descriptor = jbd2_journal_get_descriptor_buffer(journal);
 537                        if (!descriptor) {
 538                                jbd2_journal_abort(journal, -EIO);
 539                                continue;
 540                        }
 541
 542                        bh = jh2bh(descriptor);
 543                        jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 544                                (unsigned long long)bh->b_blocknr, bh->b_data);
 545                        header = (journal_header_t *)&bh->b_data[0];
 546                        header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 547                        header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 548                        header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 549
 550                        tagp = &bh->b_data[sizeof(journal_header_t)];
 551                        space_left = bh->b_size - sizeof(journal_header_t);
 552                        first_tag = 1;
 553                        set_buffer_jwrite(bh);
 554                        set_buffer_dirty(bh);
 555                        wbuf[bufs++] = bh;
 556
 557                        /* Record it so that we can wait for IO
 558                           completion later */
 559                        BUFFER_TRACE(bh, "ph3: file as descriptor");
 560                        jbd2_journal_file_buffer(descriptor, commit_transaction,
 561                                        BJ_LogCtl);
 562                }
 563
 564                /* Where is the buffer to be written? */
 565
 566                err = jbd2_journal_next_log_block(journal, &blocknr);
 567                /* If the block mapping failed, just abandon the buffer
 568                   and repeat this loop: we'll fall into the
 569                   refile-on-abort condition above. */
 570                if (err) {
 571                        jbd2_journal_abort(journal, err);
 572                        continue;
 573                }
 574
 575                /*
 576                 * start_this_handle() uses t_outstanding_credits to determine
 577                 * the free space in the log, but this counter is changed
 578                 * by jbd2_journal_next_log_block() also.
 579                 */
 580                atomic_dec(&commit_transaction->t_outstanding_credits);
 581
 582                /* Bump b_count to prevent truncate from stumbling over
 583                   the shadowed buffer!  @@@ This can go if we ever get
 584                   rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 585                atomic_inc(&jh2bh(jh)->b_count);
 586
 587                /* Make a temporary IO buffer with which to write it out
 588                   (this will requeue both the metadata buffer and the
 589                   temporary IO buffer). new_bh goes on BJ_IO*/
 590
 591                set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 592                /*
 593                 * akpm: jbd2_journal_write_metadata_buffer() sets
 594                 * new_bh->b_transaction to commit_transaction.
 595                 * We need to clean this up before we release new_bh
 596                 * (which is of type BJ_IO)
 597                 */
 598                JBUFFER_TRACE(jh, "ph3: write metadata");
 599                flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 600                                                      jh, &new_jh, blocknr);
 601                if (flags < 0) {
 602                        jbd2_journal_abort(journal, flags);
 603                        continue;
 604                }
 605                set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 606                wbuf[bufs++] = jh2bh(new_jh);
 607
 608                /* Record the new block's tag in the current descriptor
 609                   buffer */
 610
 611                tag_flag = 0;
 612                if (flags & 1)
 613                        tag_flag |= JBD2_FLAG_ESCAPE;
 614                if (!first_tag)
 615                        tag_flag |= JBD2_FLAG_SAME_UUID;
 616
 617                tag = (journal_block_tag_t *) tagp;
 618                write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 619                tag->t_flags = cpu_to_be32(tag_flag);
 620                tagp += tag_bytes;
 621                space_left -= tag_bytes;
 622
 623                if (first_tag) {
 624                        memcpy (tagp, journal->j_uuid, 16);
 625                        tagp += 16;
 626                        space_left -= 16;
 627                        first_tag = 0;
 628                }
 629
 630                /* If there's no more to do, or if the descriptor is full,
 631                   let the IO rip! */
 632
 633                if (bufs == journal->j_wbufsize ||
 634                    commit_transaction->t_buffers == NULL ||
 635                    space_left < tag_bytes + 16) {
 636
 637                        jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 638
 639                        /* Write an end-of-descriptor marker before
 640                           submitting the IOs.  "tag" still points to
 641                           the last tag we set up. */
 642
 643                        tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 644
 645start_journal_io:
 646                        for (i = 0; i < bufs; i++) {
 647                                struct buffer_head *bh = wbuf[i];
 648                                /*
 649                                 * Compute checksum.
 650                                 */
 651                                if (JBD2_HAS_COMPAT_FEATURE(journal,
 652                                        JBD2_FEATURE_COMPAT_CHECKSUM)) {
 653                                        crc32_sum =
 654                                            jbd2_checksum_data(crc32_sum, bh);
 655                                }
 656
 657                                lock_buffer(bh);
 658                                clear_buffer_dirty(bh);
 659                                set_buffer_uptodate(bh);
 660                                bh->b_end_io = journal_end_buffer_io_sync;
 661                                submit_bh(write_op, bh);
 662                        }
 663                        cond_resched();
 664                        stats.run.rs_blocks_logged += bufs;
 665
 666                        /* Force a new descriptor to be generated next
 667                           time round the loop. */
 668                        descriptor = NULL;
 669                        bufs = 0;
 670                }
 671        }
 672
 673        err = journal_finish_inode_data_buffers(journal, commit_transaction);
 674        if (err) {
 675                printk(KERN_WARNING
 676                        "JBD2: Detected IO errors while flushing file data "
 677                       "on %s\n", journal->j_devname);
 678                if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 679                        jbd2_journal_abort(journal, err);
 680                err = 0;
 681        }
 682
 683        /* 
 684         * If the journal is not located on the file system device,
 685         * then we must flush the file system device before we issue
 686         * the commit record
 687         */
 688        if (commit_transaction->t_flushed_data_blocks &&
 689            (journal->j_fs_dev != journal->j_dev) &&
 690            (journal->j_flags & JBD2_BARRIER))
 691                blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
 692
 693        /* Done it all: now write the commit record asynchronously. */
 694        if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 695                                      JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 696                err = journal_submit_commit_record(journal, commit_transaction,
 697                                                 &cbh, crc32_sum);
 698                if (err)
 699                        __jbd2_journal_abort_hard(journal);
 700        }
 701
 702        /* Lo and behold: we have just managed to send a transaction to
 703           the log.  Before we can commit it, wait for the IO so far to
 704           complete.  Control buffers being written are on the
 705           transaction's t_log_list queue, and metadata buffers are on
 706           the t_iobuf_list queue.
 707
 708           Wait for the buffers in reverse order.  That way we are
 709           less likely to be woken up until all IOs have completed, and
 710           so we incur less scheduling load.
 711        */
 712
 713        jbd_debug(3, "JBD: commit phase 3\n");
 714
 715        /*
 716         * akpm: these are BJ_IO, and j_list_lock is not needed.
 717         * See __journal_try_to_free_buffer.
 718         */
 719wait_for_iobuf:
 720        while (commit_transaction->t_iobuf_list != NULL) {
 721                struct buffer_head *bh;
 722
 723                jh = commit_transaction->t_iobuf_list->b_tprev;
 724                bh = jh2bh(jh);
 725                if (buffer_locked(bh)) {
 726                        wait_on_buffer(bh);
 727                        goto wait_for_iobuf;
 728                }
 729                if (cond_resched())
 730                        goto wait_for_iobuf;
 731
 732                if (unlikely(!buffer_uptodate(bh)))
 733                        err = -EIO;
 734
 735                clear_buffer_jwrite(bh);
 736
 737                JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 738                jbd2_journal_unfile_buffer(journal, jh);
 739
 740                /*
 741                 * ->t_iobuf_list should contain only dummy buffer_heads
 742                 * which were created by jbd2_journal_write_metadata_buffer().
 743                 */
 744                BUFFER_TRACE(bh, "dumping temporary bh");
 745                jbd2_journal_put_journal_head(jh);
 746                __brelse(bh);
 747                J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 748                free_buffer_head(bh);
 749
 750                /* We also have to unlock and free the corresponding
 751                   shadowed buffer */
 752                jh = commit_transaction->t_shadow_list->b_tprev;
 753                bh = jh2bh(jh);
 754                clear_bit(BH_JWrite, &bh->b_state);
 755                J_ASSERT_BH(bh, buffer_jbddirty(bh));
 756
 757                /* The metadata is now released for reuse, but we need
 758                   to remember it against this transaction so that when
 759                   we finally commit, we can do any checkpointing
 760                   required. */
 761                JBUFFER_TRACE(jh, "file as BJ_Forget");
 762                jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 763                /* Wake up any transactions which were waiting for this
 764                   IO to complete */
 765                wake_up_bit(&bh->b_state, BH_Unshadow);
 766                JBUFFER_TRACE(jh, "brelse shadowed buffer");
 767                __brelse(bh);
 768        }
 769
 770        J_ASSERT (commit_transaction->t_shadow_list == NULL);
 771
 772        jbd_debug(3, "JBD: commit phase 4\n");
 773
 774        /* Here we wait for the revoke record and descriptor record buffers */
 775 wait_for_ctlbuf:
 776        while (commit_transaction->t_log_list != NULL) {
 777                struct buffer_head *bh;
 778
 779                jh = commit_transaction->t_log_list->b_tprev;
 780                bh = jh2bh(jh);
 781                if (buffer_locked(bh)) {
 782                        wait_on_buffer(bh);
 783                        goto wait_for_ctlbuf;
 784                }
 785                if (cond_resched())
 786                        goto wait_for_ctlbuf;
 787
 788                if (unlikely(!buffer_uptodate(bh)))
 789                        err = -EIO;
 790
 791                BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 792                clear_buffer_jwrite(bh);
 793                jbd2_journal_unfile_buffer(journal, jh);
 794                jbd2_journal_put_journal_head(jh);
 795                __brelse(bh);           /* One for getblk */
 796                /* AKPM: bforget here */
 797        }
 798
 799        if (err)
 800                jbd2_journal_abort(journal, err);
 801
 802        jbd_debug(3, "JBD: commit phase 5\n");
 803
 804        if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 805                                       JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 806                err = journal_submit_commit_record(journal, commit_transaction,
 807                                                &cbh, crc32_sum);
 808                if (err)
 809                        __jbd2_journal_abort_hard(journal);
 810        }
 811        if (!err && !is_journal_aborted(journal))
 812                err = journal_wait_on_commit_record(journal, cbh);
 813        if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 814                                      JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT) &&
 815            journal->j_flags & JBD2_BARRIER) {
 816                blkdev_issue_flush(journal->j_dev, GFP_KERNEL, NULL);
 817        }
 818
 819        if (err)
 820                jbd2_journal_abort(journal, err);
 821
 822        /* End of a transaction!  Finally, we can do checkpoint
 823           processing: any buffers committed as a result of this
 824           transaction can be removed from any checkpoint list it was on
 825           before. */
 826
 827        jbd_debug(3, "JBD: commit phase 6\n");
 828
 829        J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 830        J_ASSERT(commit_transaction->t_buffers == NULL);
 831        J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 832        J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 833        J_ASSERT(commit_transaction->t_shadow_list == NULL);
 834        J_ASSERT(commit_transaction->t_log_list == NULL);
 835
 836restart_loop:
 837        /*
 838         * As there are other places (journal_unmap_buffer()) adding buffers
 839         * to this list we have to be careful and hold the j_list_lock.
 840         */
 841        spin_lock(&journal->j_list_lock);
 842        while (commit_transaction->t_forget) {
 843                transaction_t *cp_transaction;
 844                struct buffer_head *bh;
 845
 846                jh = commit_transaction->t_forget;
 847                spin_unlock(&journal->j_list_lock);
 848                bh = jh2bh(jh);
 849                jbd_lock_bh_state(bh);
 850                J_ASSERT_JH(jh, jh->b_transaction == commit_transaction);
 851
 852                /*
 853                 * If there is undo-protected committed data against
 854                 * this buffer, then we can remove it now.  If it is a
 855                 * buffer needing such protection, the old frozen_data
 856                 * field now points to a committed version of the
 857                 * buffer, so rotate that field to the new committed
 858                 * data.
 859                 *
 860                 * Otherwise, we can just throw away the frozen data now.
 861                 *
 862                 * We also know that the frozen data has already fired
 863                 * its triggers if they exist, so we can clear that too.
 864                 */
 865                if (jh->b_committed_data) {
 866                        jbd2_free(jh->b_committed_data, bh->b_size);
 867                        jh->b_committed_data = NULL;
 868                        if (jh->b_frozen_data) {
 869                                jh->b_committed_data = jh->b_frozen_data;
 870                                jh->b_frozen_data = NULL;
 871                                jh->b_frozen_triggers = NULL;
 872                        }
 873                } else if (jh->b_frozen_data) {
 874                        jbd2_free(jh->b_frozen_data, bh->b_size);
 875                        jh->b_frozen_data = NULL;
 876                        jh->b_frozen_triggers = NULL;
 877                }
 878
 879                spin_lock(&journal->j_list_lock);
 880                cp_transaction = jh->b_cp_transaction;
 881                if (cp_transaction) {
 882                        JBUFFER_TRACE(jh, "remove from old cp transaction");
 883                        cp_transaction->t_chp_stats.cs_dropped++;
 884                        __jbd2_journal_remove_checkpoint(jh);
 885                }
 886
 887                /* Only re-checkpoint the buffer_head if it is marked
 888                 * dirty.  If the buffer was added to the BJ_Forget list
 889                 * by jbd2_journal_forget, it may no longer be dirty and
 890                 * there's no point in keeping a checkpoint record for
 891                 * it. */
 892
 893                /* A buffer which has been freed while still being
 894                 * journaled by a previous transaction may end up still
 895                 * being dirty here, but we want to avoid writing back
 896                 * that buffer in the future after the "add to orphan"
 897                 * operation been committed,  That's not only a performance
 898                 * gain, it also stops aliasing problems if the buffer is
 899                 * left behind for writeback and gets reallocated for another
 900                 * use in a different page. */
 901                if (buffer_freed(bh) && !jh->b_next_transaction) {
 902                        clear_buffer_freed(bh);
 903                        clear_buffer_jbddirty(bh);
 904                }
 905
 906                if (buffer_jbddirty(bh)) {
 907                        JBUFFER_TRACE(jh, "add to new checkpointing trans");
 908                        __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 909                        if (is_journal_aborted(journal))
 910                                clear_buffer_jbddirty(bh);
 911                        JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 912                        __jbd2_journal_refile_buffer(jh);
 913                        jbd_unlock_bh_state(bh);
 914                } else {
 915                        J_ASSERT_BH(bh, !buffer_dirty(bh));
 916                        /* The buffer on BJ_Forget list and not jbddirty means
 917                         * it has been freed by this transaction and hence it
 918                         * could not have been reallocated until this
 919                         * transaction has committed. *BUT* it could be
 920                         * reallocated once we have written all the data to
 921                         * disk and before we process the buffer on BJ_Forget
 922                         * list. */
 923                        JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 924                        __jbd2_journal_refile_buffer(jh);
 925                        if (!jh->b_transaction) {
 926                                jbd_unlock_bh_state(bh);
 927                                 /* needs a brelse */
 928                                jbd2_journal_remove_journal_head(bh);
 929                                release_buffer_page(bh);
 930                        } else
 931                                jbd_unlock_bh_state(bh);
 932                }
 933                cond_resched_lock(&journal->j_list_lock);
 934        }
 935        spin_unlock(&journal->j_list_lock);
 936        /*
 937         * This is a bit sleazy.  We use j_list_lock to protect transition
 938         * of a transaction into T_FINISHED state and calling
 939         * __jbd2_journal_drop_transaction(). Otherwise we could race with
 940         * other checkpointing code processing the transaction...
 941         */
 942        write_lock(&journal->j_state_lock);
 943        spin_lock(&journal->j_list_lock);
 944        /*
 945         * Now recheck if some buffers did not get attached to the transaction
 946         * while the lock was dropped...
 947         */
 948        if (commit_transaction->t_forget) {
 949                spin_unlock(&journal->j_list_lock);
 950                write_unlock(&journal->j_state_lock);
 951                goto restart_loop;
 952        }
 953
 954        /* Done with this transaction! */
 955
 956        jbd_debug(3, "JBD: commit phase 7\n");
 957
 958        J_ASSERT(commit_transaction->t_state == T_COMMIT);
 959
 960        commit_transaction->t_start = jiffies;
 961        stats.run.rs_logging = jbd2_time_diff(stats.run.rs_logging,
 962                                              commit_transaction->t_start);
 963
 964        /*
 965         * File the transaction statistics
 966         */
 967        stats.ts_tid = commit_transaction->t_tid;
 968        stats.run.rs_handle_count =
 969                atomic_read(&commit_transaction->t_handle_count);
 970        trace_jbd2_run_stats(journal->j_fs_dev->bd_dev,
 971                             commit_transaction->t_tid, &stats.run);
 972
 973        /*
 974         * Calculate overall stats
 975         */
 976        spin_lock(&journal->j_history_lock);
 977        journal->j_stats.ts_tid++;
 978        journal->j_stats.run.rs_wait += stats.run.rs_wait;
 979        journal->j_stats.run.rs_running += stats.run.rs_running;
 980        journal->j_stats.run.rs_locked += stats.run.rs_locked;
 981        journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
 982        journal->j_stats.run.rs_logging += stats.run.rs_logging;
 983        journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
 984        journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
 985        journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
 986        spin_unlock(&journal->j_history_lock);
 987
 988        commit_transaction->t_state = T_FINISHED;
 989        J_ASSERT(commit_transaction == journal->j_committing_transaction);
 990        journal->j_commit_sequence = commit_transaction->t_tid;
 991        journal->j_committing_transaction = NULL;
 992        commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
 993
 994        /*
 995         * weight the commit time higher than the average time so we don't
 996         * react too strongly to vast changes in the commit time
 997         */
 998        if (likely(journal->j_average_commit_time))
 999                journal->j_average_commit_time = (commit_time +
1000                                journal->j_average_commit_time*3) / 4;
1001        else
1002                journal->j_average_commit_time = commit_time;
1003        write_unlock(&journal->j_state_lock);
1004
1005        if (commit_transaction->t_checkpoint_list == NULL &&
1006            commit_transaction->t_checkpoint_io_list == NULL) {
1007                __jbd2_journal_drop_transaction(journal, commit_transaction);
1008                to_free = 1;
1009        } else {
1010                if (journal->j_checkpoint_transactions == NULL) {
1011                        journal->j_checkpoint_transactions = commit_transaction;
1012                        commit_transaction->t_cpnext = commit_transaction;
1013                        commit_transaction->t_cpprev = commit_transaction;
1014                } else {
1015                        commit_transaction->t_cpnext =
1016                                journal->j_checkpoint_transactions;
1017                        commit_transaction->t_cpprev =
1018                                commit_transaction->t_cpnext->t_cpprev;
1019                        commit_transaction->t_cpnext->t_cpprev =
1020                                commit_transaction;
1021                        commit_transaction->t_cpprev->t_cpnext =
1022                                commit_transaction;
1023                }
1024        }
1025        spin_unlock(&journal->j_list_lock);
1026
1027        if (journal->j_commit_callback)
1028                journal->j_commit_callback(journal, commit_transaction);
1029
1030        trace_jbd2_end_commit(journal, commit_transaction);
1031        jbd_debug(1, "JBD: commit %d complete, head %d\n",
1032                  journal->j_commit_sequence, journal->j_tail_sequence);
1033        if (to_free)
1034                kfree(commit_transaction);
1035
1036        wake_up(&journal->j_wait_done_commit);
1037}
1038