fs/jbd2/checkpoint.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * linux/fs/jbd2/checkpoint.c
   4  *
   5  * Written by Stephen C. Tweedie <[email protected]>, 1999
   6  *
   7  * Copyright 1999 Red Hat Software --- All Rights Reserved
   8  *
   9  * Checkpoint routines for the generic filesystem journaling code.
  10  * Part of the ext2fs journaling system.
  11  *
  12  * Checkpointing is the process of ensuring that a section of the log is
  13  * committed fully to disk, so that that portion of the log can be
  14  * reused.
  15  */
  16
  17 #include <linux/time.h>
  18 #include <linux/fs.h>
  19 #include <linux/jbd2.h>
  20 #include <linux/errno.h>
  21 #include <linux/slab.h>
  22 #include <linux/blkdev.h>
  23 #include <trace/events/jbd2.h>
  24
  25 /*
  26  * Unlink a buffer from a transaction checkpoint list.
  27  *
  28  * Called with j_list_lock held.
  29  */
  30 static inline void __buffer_unlink_first(struct journal_head *jh)
  31 {
  32         transaction_t *transaction = jh->b_cp_transaction;
  33
  34         jh->b_cpnext->b_cpprev = jh->b_cpprev;
  35         jh->b_cpprev->b_cpnext = jh->b_cpnext;
  36         if (transaction->t_checkpoint_list == jh) {
  37                 transaction->t_checkpoint_list = jh->b_cpnext;
  38                 if (transaction->t_checkpoint_list == jh)
  39                         transaction->t_checkpoint_list = NULL;
  40         }
  41 }
  42
  43 /*
  44  * Unlink a buffer from a transaction checkpoint(io) list.
  45  *
  46  * Called with j_list_lock held.
  47  */
  48 static inline void __buffer_unlink(struct journal_head *jh)
  49 {
  50         transaction_t *transaction = jh->b_cp_transaction;
  51
  52         __buffer_unlink_first(jh);
  53         if (transaction->t_checkpoint_io_list == jh) {
  54                 transaction->t_checkpoint_io_list = jh->b_cpnext;
  55                 if (transaction->t_checkpoint_io_list == jh)
  56                         transaction->t_checkpoint_io_list = NULL;
  57         }
  58 }
  59
  60 /*
  61  * Move a buffer from the checkpoint list to the checkpoint io list
  62  *
  63  * Called with j_list_lock held
  64  */
  65 static inline void __buffer_relink_io(struct journal_head *jh)
  66 {
  67         transaction_t *transaction = jh->b_cp_transaction;
  68
  69         __buffer_unlink_first(jh);
  70
  71         if (!transaction->t_checkpoint_io_list) {
  72                 jh->b_cpnext = jh->b_cpprev = jh;
  73         } else {
  74                 jh->b_cpnext = transaction->t_checkpoint_io_list;
  75                 jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
  76                 jh->b_cpprev->b_cpnext = jh;
  77                 jh->b_cpnext->b_cpprev = jh;
  78         }
  79         transaction->t_checkpoint_io_list = jh;
  80 }
  81
  82 /*
  83  * Check a checkpoint buffer could be release or not.
  84  *
  85  * Requires j_list_lock
  86  */
  87 static inline bool __cp_buffer_busy(struct journal_head *jh)
  88 {
  89         struct buffer_head *bh = jh2bh(jh);
  90
  91         return (jh->b_transaction || buffer_locked(bh) || buffer_dirty(bh));
  92 }
  93
  94 /*
  95  * __jbd2_log_wait_for_space: wait until there is space in the journal.
  96  *
  97  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
  98  * for a checkpoint to free up some space in the log.
  99  */
 100 void __jbd2_log_wait_for_space(journal_t *journal)
 101 __acquires(&journal->j_state_lock)
 102 __releases(&journal->j_state_lock)
 103 {
 104         int nblocks, space_left;
 105         /* assert_spin_locked(&journal->j_state_lock); */
 106
 107         nblocks = journal->j_max_transaction_buffers;
 108         while (jbd2_log_space_left(journal) < nblocks) {
 109                 write_unlock(&journal->j_state_lock);
 110                 mutex_lock_io(&journal->j_checkpoint_mutex);
 111
 112                 /*
 113                  * Test again, another process may have checkpointed while we
 114                  * were waiting for the checkpoint lock. If there are no
 115                  * transactions ready to be checkpointed, try to recover
 116                  * journal space by calling cleanup_journal_tail(), and if
 117                  * that doesn't work, by waiting for the currently committing
 118                  * transaction to complete.  If there is absolutely no way
 119                  * to make progress, this is either a BUG or corrupted
 120                  * filesystem, so abort the journal and leave a stack
 121                  * trace for forensic evidence.
 122                  */
 123                 write_lock(&journal->j_state_lock);
 124                 if (journal->j_flags & JBD2_ABORT) {
 125                         mutex_unlock(&journal->j_checkpoint_mutex);
 126                         return;
 127                 }
 128                 spin_lock(&journal->j_list_lock);
 129                 space_left = jbd2_log_space_left(journal);
 130                 if (space_left < nblocks) {
 131                         int chkpt = journal->j_checkpoint_transactions != NULL;
 132                         tid_t tid = 0;
 133
 134                         if (journal->j_committing_transaction)
 135                                 tid = journal->j_committing_transaction->t_tid;
 136                         spin_unlock(&journal->j_list_lock);
 137                         write_unlock(&journal->j_state_lock);
 138                         if (chkpt) {
 139                                 jbd2_log_do_checkpoint(journal);
 140                         } else if (jbd2_cleanup_journal_tail(journal) == 0) {
 141                                 /* We were able to recover space; yay! */
 142                                 ;
 143                         } else if (tid) {
 144                                 /*
 145                                  * jbd2_journal_commit_transaction() may want
 146                                  * to take the checkpoint_mutex if JBD2_FLUSHED
 147                                  * is set.  So we need to temporarily drop it.
 148                                  */
 149                                 mutex_unlock(&journal->j_checkpoint_mutex);
 150                                 jbd2_log_wait_commit(journal, tid);
 151                                 write_lock(&journal->j_state_lock);
 152                                 continue;
 153                         } else {
 154                                 printk(KERN_ERR "%s: needed %d blocks and "
 155                                        "only had %d space available\n",
 156                                        __func__, nblocks, space_left);
 157                                 printk(KERN_ERR "%s: no way to get more "
 158                                        "journal space in %s\n", __func__,
 159                                        journal->j_devname);
 160                                 WARN_ON(1);
 161                                 jbd2_journal_abort(journal, -EIO);
 162                         }
 163                         write_lock(&journal->j_state_lock);
 164                 } else {
 165                         spin_unlock(&journal->j_list_lock);
 166                 }
 167                 mutex_unlock(&journal->j_checkpoint_mutex);
 168         }
 169 }
 170
 171 static void
 172 __flush_batch(journal_t *journal, int *batch_count)
 173 {
 174         int i;
 175         struct blk_plug plug;
 176
 177         blk_start_plug(&plug);
 178         for (i = 0; i < *batch_count; i++)
 179                 write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
 180         blk_finish_plug(&plug);
 181
 182         for (i = 0; i < *batch_count; i++) {
 183                 struct buffer_head *bh = journal->j_chkpt_bhs[i];
 184                 BUFFER_TRACE(bh, "brelse");
 185                 __brelse(bh);
 186         }
 187         *batch_count = 0;
 188 }
 189
 190 /*
 191  * Perform an actual checkpoint. We take the first transaction on the
 192  * list of transactions to be checkpointed and send all its buffers
 193  * to disk. We submit larger chunks of data at once.
 194  *
 195  * The journal should be locked before calling this function.
 196  * Called with j_checkpoint_mutex held.
 197  */
 198 int jbd2_log_do_checkpoint(journal_t *journal)
 199 {
 200         struct journal_head     *jh;
 201         struct buffer_head      *bh;
 202         transaction_t           *transaction;
 203         tid_t                   this_tid;
 204         int                     result, batch_count = 0;
 205
 206         jbd_debug(1, "Start checkpoint\n");
 207
 208         /*
 209          * First thing: if there are any transactions in the log which
 210          * don't need checkpointing, just eliminate them from the
 211          * journal straight away.
 212          */
 213         result = jbd2_cleanup_journal_tail(journal);
 214         trace_jbd2_checkpoint(journal, result);
 215         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 216         if (result <= 0)
 217                 return result;
 218
 219         /*
 220          * OK, we need to start writing disk blocks.  Take one transaction
 221          * and write it.
 222          */
 223         spin_lock(&journal->j_list_lock);
 224         if (!journal->j_checkpoint_transactions)
 225                 goto out;
 226         transaction = journal->j_checkpoint_transactions;
 227         if (transaction->t_chp_stats.cs_chp_time == 0)
 228                 transaction->t_chp_stats.cs_chp_time = jiffies;
 229         this_tid = transaction->t_tid;
 230 restart:
 231         /*
 232          * If someone cleaned up this transaction while we slept, we're
 233          * done (maybe it's a new transaction, but it fell at the same
 234          * address).
 235          */
 236         if (journal->j_checkpoint_transactions != transaction ||
 237             transaction->t_tid != this_tid)
 238                 goto out;
 239
 240         /* checkpoint all of the transaction's buffers */
 241         while (transaction->t_checkpoint_list) {
 242                 jh = transaction->t_checkpoint_list;
 243                 bh = jh2bh(jh);
 244
 245                 if (buffer_locked(bh)) {
 246                         get_bh(bh);
 247                         spin_unlock(&journal->j_list_lock);
 248                         wait_on_buffer(bh);
 249                         /* the journal_head may have gone by now */
 250                         BUFFER_TRACE(bh, "brelse");
 251                         __brelse(bh);
 252                         goto retry;
 253                 }
 254                 if (jh->b_transaction != NULL) {
 255                         transaction_t *t = jh->b_transaction;
 256                         tid_t tid = t->t_tid;
 257
 258                         transaction->t_chp_stats.cs_forced_to_close++;
 259                         spin_unlock(&journal->j_list_lock);
 260                         if (unlikely(journal->j_flags & JBD2_UNMOUNT))
 261                                 /*
 262                                  * The journal thread is dead; so
 263                                  * starting and waiting for a commit
 264                                  * to finish will cause us to wait for
 265                                  * a _very_ long time.
 266                                  */
 267                                 printk(KERN_ERR
 268                 "JBD2: %s: Waiting for Godot: block %llu\n",
 269                 journal->j_devname, (unsigned long long) bh->b_blocknr);
 270
 271                         if (batch_count)
 272                                 __flush_batch(journal, &batch_count);
 273                         jbd2_log_start_commit(journal, tid);
 274                         /*
 275                          * jbd2_journal_commit_transaction() may want
 276                          * to take the checkpoint_mutex if JBD2_FLUSHED
 277                          * is set, jbd2_update_log_tail() called by
 278                          * jbd2_journal_commit_transaction() may also take
 279                          * checkpoint_mutex.  So we need to temporarily
 280                          * drop it.
 281                          */
 282                         mutex_unlock(&journal->j_checkpoint_mutex);
 283                         jbd2_log_wait_commit(journal, tid);
 284                         mutex_lock_io(&journal->j_checkpoint_mutex);
 285                         spin_lock(&journal->j_list_lock);
 286                         goto restart;
 287                 }
 288                 if (!buffer_dirty(bh)) {
 289                         BUFFER_TRACE(bh, "remove from checkpoint");
 290                         if (__jbd2_journal_remove_checkpoint(jh))
 291                                 /* The transaction was released; we're done */
 292                                 goto out;
 293                         continue;
 294                 }
 295                 /*
 296                  * Important: we are about to write the buffer, and
 297                  * possibly block, while still holding the journal
 298                  * lock.  We cannot afford to let the transaction
 299                  * logic start messing around with this buffer before
 300                  * we write it to disk, as that would break
 301                  * recoverability.
 302                  */
 303                 BUFFER_TRACE(bh, "queue");
 304                 get_bh(bh);
 305                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 306                 journal->j_chkpt_bhs[batch_count++] = bh;
 307                 __buffer_relink_io(jh);
 308                 transaction->t_chp_stats.cs_written++;
 309                 if ((batch_count == JBD2_NR_BATCH) ||
 310                     need_resched() ||
 311                     spin_needbreak(&journal->j_list_lock))
 312                         goto unlock_and_flush;
 313         }
 314
 315         if (batch_count) {
 316                 unlock_and_flush:
 317                         spin_unlock(&journal->j_list_lock);
 318                 retry:
 319                         if (batch_count)
 320                                 __flush_batch(journal, &batch_count);
 321                         spin_lock(&journal->j_list_lock);
 322                         goto restart;
 323         }
 324
 325         /*
 326          * Now we issued all of the transaction's buffers, let's deal
 327          * with the buffers that are out for I/O.
 328          */
 329 restart2:
 330         /* Did somebody clean up the transaction in the meanwhile? */
 331         if (journal->j_checkpoint_transactions != transaction ||
 332             transaction->t_tid != this_tid)
 333                 goto out;
 334
 335         while (transaction->t_checkpoint_io_list) {
 336                 jh = transaction->t_checkpoint_io_list;
 337                 bh = jh2bh(jh);
 338                 if (buffer_locked(bh)) {
 339                         get_bh(bh);
 340                         spin_unlock(&journal->j_list_lock);
 341                         wait_on_buffer(bh);
 342                         /* the journal_head may have gone by now */
 343                         BUFFER_TRACE(bh, "brelse");
 344                         __brelse(bh);
 345                         spin_lock(&journal->j_list_lock);
 346                         goto restart2;
 347                 }
 348
 349                 /*
 350                  * Now in whatever state the buffer currently is, we
 351                  * know that it has been written out and so we can
 352                  * drop it from the list
 353                  */
 354                 if (__jbd2_journal_remove_checkpoint(jh))
 355                         break;
 356         }
 357 out:
 358         spin_unlock(&journal->j_list_lock);
 359         result = jbd2_cleanup_journal_tail(journal);
 360
 361         return (result < 0) ? result : 0;
 362 }
 363
 364 /*
 365  * Check the list of checkpoint transactions for the journal to see if
 366  * we have already got rid of any since the last update of the log tail
 367  * in the journal superblock.  If so, we can instantly roll the
 368  * superblock forward to remove those transactions from the log.
 369  *
 370  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 371  *
 372  * Called with the journal lock held.
 373  *
 374  * This is the only part of the journaling code which really needs to be
 375  * aware of transaction aborts.  Checkpointing involves writing to the
 376  * main filesystem area rather than to the journal, so it can proceed
 377  * even in abort state, but we must not update the super block if
 378  * checkpointing may have failed.  Otherwise, we would lose some metadata
 379  * buffers which should be written-back to the filesystem.
 380  */
 381
 382 int jbd2_cleanup_journal_tail(journal_t *journal)
 383 {
 384         tid_t           first_tid;
 385         unsigned long   blocknr;
 386
 387         if (is_journal_aborted(journal))
 388                 return -EIO;
 389
 390         if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
 391                 return 1;
 392         J_ASSERT(blocknr != 0);
 393
 394         /*
 395          * We need to make sure that any blocks that were recently written out
 396          * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
 397          * we drop the transactions from the journal. It's unlikely this will
 398          * be necessary, especially with an appropriately sized journal, but we
 399          * need this to guarantee correctness.  Fortunately
 400          * jbd2_cleanup_journal_tail() doesn't get called all that often.
 401          */
 402         if (journal->j_flags & JBD2_BARRIER)
 403                 blkdev_issue_flush(journal->j_fs_dev);
 404
 405         return __jbd2_update_log_tail(journal, first_tid, blocknr);
 406 }
 407
 408
 409 /* Checkpoint list management */
 410
 411 /*
 412  * journal_clean_one_cp_list
 413  *
 414  * Find all the written-back checkpoint buffers in the given list and
 415  * release them. If 'destroy' is set, clean all buffers unconditionally.
 416  *
 417  * Called with j_list_lock held.
 418  * Returns 1 if we freed the transaction, 0 otherwise.
 419  */
 420 static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
 421 {
 422         struct journal_head *last_jh;
 423         struct journal_head *next_jh = jh;
 424
 425         if (!jh)
 426                 return 0;
 427
 428         last_jh = jh->b_cpprev;
 429         do {
 430                 jh = next_jh;
 431                 next_jh = jh->b_cpnext;
 432
 433                 if (!destroy && __cp_buffer_busy(jh))
 434                         return 0;
 435
 436                 if (__jbd2_journal_remove_checkpoint(jh))
 437                         return 1;
 438                 /*
 439                  * This function only frees up some memory
 440                  * if possible so we dont have an obligation
 441                  * to finish processing. Bail out if preemption
 442                  * requested:
 443                  */
 444                 if (need_resched())
 445                         return 0;
 446         } while (jh != last_jh);
 447
 448         return 0;
 449 }
 450
 451 /*
 452  * journal_shrink_one_cp_list
 453  *
 454  * Find 'nr_to_scan' written-back checkpoint buffers in the given list
 455  * and try to release them. If the whole transaction is released, set
 456  * the 'released' parameter. Return the number of released checkpointed
 457  * buffers.
 458  *
 459  * Called with j_list_lock held.
 460  */
 461 static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
 462                                                 unsigned long *nr_to_scan,
 463                                                 bool *released)
 464 {
 465         struct journal_head *last_jh;
 466         struct journal_head *next_jh = jh;
 467         unsigned long nr_freed = 0;
 468         int ret;
 469
 470         if (!jh || *nr_to_scan == 0)
 471                 return 0;
 472
 473         last_jh = jh->b_cpprev;
 474         do {
 475                 jh = next_jh;
 476                 next_jh = jh->b_cpnext;
 477
 478                 (*nr_to_scan)--;
 479                 if (__cp_buffer_busy(jh))
 480                         continue;
 481
 482                 nr_freed++;
 483                 ret = __jbd2_journal_remove_checkpoint(jh);
 484                 if (ret) {
 485                         *released = true;
 486                         break;
 487                 }
 488
 489                 if (need_resched())
 490                         break;
 491         } while (jh != last_jh && *nr_to_scan);
 492
 493         return nr_freed;
 494 }
 495
 496 /*
 497  * jbd2_journal_shrink_checkpoint_list
 498  *
 499  * Find 'nr_to_scan' written-back checkpoint buffers in the journal
 500  * and try to release them. Return the number of released checkpointed
 501  * buffers.
 502  *
 503  * Called with j_list_lock held.
 504  */
 505 unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
 506                                                   unsigned long *nr_to_scan)
 507 {
 508         transaction_t *transaction, *last_transaction, *next_transaction;
 509         bool released;
 510         tid_t first_tid = 0, last_tid = 0, next_tid = 0;
 511         tid_t tid = 0;
 512         unsigned long nr_freed = 0;
 513         unsigned long nr_scanned = *nr_to_scan;
 514
 515 again:
 516         spin_lock(&journal->j_list_lock);
 517         if (!journal->j_checkpoint_transactions) {
 518                 spin_unlock(&journal->j_list_lock);
 519                 goto out;
 520         }
 521
 522         /*
 523          * Get next shrink transaction, resume previous scan or start
 524          * over again. If some others do checkpoint and drop transaction
 525          * from the checkpoint list, we ignore saved j_shrink_transaction
 526          * and start over unconditionally.
 527          */
 528         if (journal->j_shrink_transaction)
 529                 transaction = journal->j_shrink_transaction;
 530         else
 531                 transaction = journal->j_checkpoint_transactions;
 532
 533         if (!first_tid)
 534                 first_tid = transaction->t_tid;
 535         last_transaction = journal->j_checkpoint_transactions->t_cpprev;
 536         next_transaction = transaction;
 537         last_tid = last_transaction->t_tid;
 538         do {
 539                 transaction = next_transaction;
 540                 next_transaction = transaction->t_cpnext;
 541                 tid = transaction->t_tid;
 542                 released = false;
 543
 544                 nr_freed += journal_shrink_one_cp_list(transaction->t_checkpoint_list,
 545                                                        nr_to_scan, &released);
 546                 if (*nr_to_scan == 0)
 547                         break;
 548                 if (need_resched() || spin_needbreak(&journal->j_list_lock))
 549                         break;
 550                 if (released)
 551                         continue;
 552
 553                 nr_freed += journal_shrink_one_cp_list(transaction->t_checkpoint_io_list,
 554                                                        nr_to_scan, &released);
 555                 if (*nr_to_scan == 0)
 556                         break;
 557                 if (need_resched() || spin_needbreak(&journal->j_list_lock))
 558                         break;
 559         } while (transaction != last_transaction);
 560
 561         if (transaction != last_transaction) {
 562                 journal->j_shrink_transaction = next_transaction;
 563                 next_tid = next_transaction->t_tid;
 564         } else {
 565                 journal->j_shrink_transaction = NULL;
 566                 next_tid = 0;
 567         }
 568
 569         spin_unlock(&journal->j_list_lock);
 570         cond_resched();
 571
 572         if (*nr_to_scan && next_tid)
 573                 goto again;
 574 out:
 575         nr_scanned -= *nr_to_scan;
 576         trace_jbd2_shrink_checkpoint_list(journal, first_tid, tid, last_tid,
 577                                           nr_freed, nr_scanned, next_tid);
 578
 579         return nr_freed;
 580 }
 581
 582 /*
 583  * journal_clean_checkpoint_list
 584  *
 585  * Find all the written-back checkpoint buffers in the journal and release them.
 586  * If 'destroy' is set, release all buffers unconditionally.
 587  *
 588  * Called with j_list_lock held.
 589  */
 590 void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
 591 {
 592         transaction_t *transaction, *last_transaction, *next_transaction;
 593         int ret;
 594
 595         transaction = journal->j_checkpoint_transactions;
 596         if (!transaction)
 597                 return;
 598
 599         last_transaction = transaction->t_cpprev;
 600         next_transaction = transaction;
 601         do {
 602                 transaction = next_transaction;
 603                 next_transaction = transaction->t_cpnext;
 604                 ret = journal_clean_one_cp_list(transaction->t_checkpoint_list,
 605                                                 destroy);
 606                 /*
 607                  * This function only frees up some memory if possible so we
 608                  * dont have an obligation to finish processing. Bail out if
 609                  * preemption requested:
 610                  */
 611                 if (need_resched())
 612                         return;
 613                 if (ret)
 614                         continue;
 615                 /*
 616                  * It is essential that we are as careful as in the case of
 617                  * t_checkpoint_list with removing the buffer from the list as
 618                  * we can possibly see not yet submitted buffers on io_list
 619                  */
 620                 ret = journal_clean_one_cp_list(transaction->
 621                                 t_checkpoint_io_list, destroy);
 622                 if (need_resched())
 623                         return;
 624                 /*
 625                  * Stop scanning if we couldn't free the transaction. This
 626                  * avoids pointless scanning of transactions which still
 627                  * weren't checkpointed.
 628                  */
 629                 if (!ret)
 630                         return;
 631         } while (transaction != last_transaction);
 632 }
 633
 634 /*
 635  * Remove buffers from all checkpoint lists as journal is aborted and we just
 636  * need to free memory
 637  */
 638 void jbd2_journal_destroy_checkpoint(journal_t *journal)
 639 {
 640         /*
 641          * We loop because __jbd2_journal_clean_checkpoint_list() may abort
 642          * early due to a need of rescheduling.
 643          */
 644         while (1) {
 645                 spin_lock(&journal->j_list_lock);
 646                 if (!journal->j_checkpoint_transactions) {
 647                         spin_unlock(&journal->j_list_lock);
 648                         break;
 649                 }
 650                 __jbd2_journal_clean_checkpoint_list(journal, true);
 651                 spin_unlock(&journal->j_list_lock);
 652                 cond_resched();
 653         }
 654 }
 655
 656 /*
 657  * journal_remove_checkpoint: called after a buffer has been committed
 658  * to disk (either by being write-back flushed to disk, or being
 659  * committed to the log).
 660  *
 661  * We cannot safely clean a transaction out of the log until all of the
 662  * buffer updates committed in that transaction have safely been stored
 663  * elsewhere on disk.  To achieve this, all of the buffers in a
 664  * transaction need to be maintained on the transaction's checkpoint
 665  * lists until they have been rewritten, at which point this function is
 666  * called to remove the buffer from the existing transaction's
 667  * checkpoint lists.
 668  *
 669  * The function returns 1 if it frees the transaction, 0 otherwise.
 670  * The function can free jh and bh.
 671  *
 672  * This function is called with j_list_lock held.
 673  */
 674 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 675 {
 676         struct transaction_chp_stats_s *stats;
 677         transaction_t *transaction;
 678         journal_t *journal;
 679         struct buffer_head *bh = jh2bh(jh);
 680
 681         JBUFFER_TRACE(jh, "entry");
 682
 683         transaction = jh->b_cp_transaction;
 684         if (!transaction) {
 685                 JBUFFER_TRACE(jh, "not on transaction");
 686                 return 0;
 687         }
 688         journal = transaction->t_journal;
 689
 690         JBUFFER_TRACE(jh, "removing from transaction");
 691
 692         /*
 693          * If we have failed to write the buffer out to disk, the filesystem
 694          * may become inconsistent. We cannot abort the journal here since
 695          * we hold j_list_lock and we have to be careful about races with
 696          * jbd2_journal_destroy(). So mark the writeback IO error in the
 697          * journal here and we abort the journal later from a better context.
 698          */
 699         if (buffer_write_io_error(bh))
 700                 set_bit(JBD2_CHECKPOINT_IO_ERROR, &journal->j_atomic_flags);
 701
 702         __buffer_unlink(jh);
 703         jh->b_cp_transaction = NULL;
 704         percpu_counter_dec(&journal->j_checkpoint_jh_count);
 705         jbd2_journal_put_journal_head(jh);
 706
 707         /* Is this transaction empty? */
 708         if (transaction->t_checkpoint_list || transaction->t_checkpoint_io_list)
 709                 return 0;
 710
 711         /*
 712          * There is one special case to worry about: if we have just pulled the
 713          * buffer off a running or committing transaction's checkpoing list,
 714          * then even if the checkpoint list is empty, the transaction obviously
 715          * cannot be dropped!
 716          *
 717          * The locking here around t_state is a bit sleazy.
 718          * See the comment at the end of jbd2_journal_commit_transaction().
 719          */
 720         if (transaction->t_state != T_FINISHED)
 721                 return 0;
 722
 723         /*
 724          * OK, that was the last buffer for the transaction, we can now
 725          * safely remove this transaction from the log.
 726          */
 727         stats = &transaction->t_chp_stats;
 728         if (stats->cs_chp_time)
 729                 stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
 730                                                     jiffies);
 731         trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
 732                                     transaction->t_tid, stats);
 733
 734         __jbd2_journal_drop_transaction(journal, transaction);
 735         jbd2_journal_free_transaction(transaction);
 736         return 1;
 737 }
 738
 739 /*
 740  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 741  * list so that we know when it is safe to clean the transaction out of
 742  * the log.
 743  *
 744  * Called with the journal locked.
 745  * Called with j_list_lock held.
 746  */
 747 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
 748                                transaction_t *transaction)
 749 {
 750         JBUFFER_TRACE(jh, "entry");
 751         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 752         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 753
 754         /* Get reference for checkpointing transaction */
 755         jbd2_journal_grab_journal_head(jh2bh(jh));
 756         jh->b_cp_transaction = transaction;
 757
 758         if (!transaction->t_checkpoint_list) {
 759                 jh->b_cpnext = jh->b_cpprev = jh;
 760         } else {
 761                 jh->b_cpnext = transaction->t_checkpoint_list;
 762                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 763                 jh->b_cpprev->b_cpnext = jh;
 764                 jh->b_cpnext->b_cpprev = jh;
 765         }
 766         transaction->t_checkpoint_list = jh;
 767         percpu_counter_inc(&transaction->t_journal->j_checkpoint_jh_count);
 768 }
 769
 770 /*
 771  * We've finished with this transaction structure: adios...
 772  *
 773  * The transaction must have no links except for the checkpoint by this
 774  * point.
 775  *
 776  * Called with the journal locked.
 777  * Called with j_list_lock held.
 778  */
 779
 780 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 781 {
 782         assert_spin_locked(&journal->j_list_lock);
 783
 784         journal->j_shrink_transaction = NULL;
 785         if (transaction->t_cpnext) {
 786                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 787                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 788                 if (journal->j_checkpoint_transactions == transaction)
 789                         journal->j_checkpoint_transactions =
 790                                 transaction->t_cpnext;
 791                 if (journal->j_checkpoint_transactions == transaction)
 792                         journal->j_checkpoint_transactions = NULL;
 793         }
 794
 795         J_ASSERT(transaction->t_state == T_FINISHED);
 796         J_ASSERT(transaction->t_buffers == NULL);
 797         J_ASSERT(transaction->t_forget == NULL);
 798         J_ASSERT(transaction->t_shadow_list == NULL);
 799         J_ASSERT(transaction->t_checkpoint_list == NULL);
 800         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 801         J_ASSERT(atomic_read(&transaction->t_updates) == 0);
 802         J_ASSERT(journal->j_committing_transaction != transaction);
 803         J_ASSERT(journal->j_running_transaction != transaction);
 804
 805         trace_jbd2_drop_transaction(journal, transaction);
 806
 807         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 808 }