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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * linux/fs/jbd2/checkpoint.c
  *
  * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
  *
  * Copyright 1999 Red Hat Software --- All Rights Reserved
  *
  * Checkpoint routines for the generic filesystem journaling code.
  * Part of the ext2fs journaling system.
  *
  * Checkpointing is the process of ensuring that a section of the log is
  * committed fully to disk, so that that portion of the log can be
  * reused.
  */
 
 #include <linux/time.h>
 #include <linux/fs.h>
 #include <linux/jbd2.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/blkdev.h>
 #include <trace/events/jbd2.h>
 
 /*
  * Unlink a buffer from a transaction checkpoint list.
  *
  * Called with j_list_lock held.
  */
 static inline void __buffer_unlink_first(struct journal_head *jh)
 {
     transaction_t *transaction = jh->b_cp_transaction;
 
     jh->b_cpnext->b_cpprev = jh->b_cpprev;
     jh->b_cpprev->b_cpnext = jh->b_cpnext;
     if (transaction->t_checkpoint_list == jh) {
         transaction->t_checkpoint_list = jh->b_cpnext;
         if (transaction->t_checkpoint_list == jh)
             transaction->t_checkpoint_list = NULL;
     }
 }
 
 /*
  * Unlink a buffer from a transaction checkpoint(io) list.
  *
  * Called with j_list_lock held.
  */
 static inline void __buffer_unlink(struct journal_head *jh)
 {
     transaction_t *transaction = jh->b_cp_transaction;
 
     __buffer_unlink_first(jh);
     if (transaction->t_checkpoint_io_list == jh) {
         transaction->t_checkpoint_io_list = jh->b_cpnext;
         if (transaction->t_checkpoint_io_list == jh)
             transaction->t_checkpoint_io_list = NULL;
     }
 }
 
 /*
  * Move a buffer from the checkpoint list to the checkpoint io list
  *
  * Called with j_list_lock held
  */
 static inline void __buffer_relink_io(struct journal_head *jh)
 {
     transaction_t *transaction = jh->b_cp_transaction;
 
     __buffer_unlink_first(jh);
 
     if (!transaction->t_checkpoint_io_list) {
         jh->b_cpnext = jh->b_cpprev = jh;
     } else {
         jh->b_cpnext = transaction->t_checkpoint_io_list;
         jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
         jh->b_cpprev->b_cpnext = jh;
         jh->b_cpnext->b_cpprev = jh;
     }
     transaction->t_checkpoint_io_list = jh;
 }
 
 /*
  * Check a checkpoint buffer could be release or not.
  *
  * Requires j_list_lock
  */
 static inline bool __cp_buffer_busy(struct journal_head *jh)
 {
     struct buffer_head *bh = jh2bh(jh);
 
     return (jh->b_transaction || buffer_locked(bh) || buffer_dirty(bh));
 }
 
 /*
  * __jbd2_log_wait_for_space: wait until there is space in the journal.
  *
  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
  * for a checkpoint to free up some space in the log.
  */
 void __jbd2_log_wait_for_space(journal_t *journal)
 __acquires(&journal->j_state_lock)
 __releases(&journal->j_state_lock)
 {
     int nblocks, space_left;
     /* assert_spin_locked(&journal->j_state_lock); */
 
     nblocks = journal->j_max_transaction_buffers;
     while (jbd2_log_space_left(journal) < nblocks) {
         write_unlock(&journal->j_state_lock);
         mutex_lock_io(&journal->j_checkpoint_mutex);
 
         /*
          * Test again, another process may have checkpointed while we
          * were waiting for the checkpoint lock. If there are no
          * transactions ready to be checkpointed, try to recover
          * journal space by calling cleanup_journal_tail(), and if
          * that doesn't work, by waiting for the currently committing
          * transaction to complete.  If there is absolutely no way
          * to make progress, this is either a BUG or corrupted
          * filesystem, so abort the journal and leave a stack
          * trace for forensic evidence.
          */
         write_lock(&journal->j_state_lock);
         if (journal->j_flags & JBD2_ABORT) {
             mutex_unlock(&journal->j_checkpoint_mutex);
             return;
         }
         spin_lock(&journal->j_list_lock);
         space_left = jbd2_log_space_left(journal);
         if (space_left < nblocks) {
             int chkpt = journal->j_checkpoint_transactions != NULL;
             tid_t tid = 0;
 
             if (journal->j_committing_transaction)
                 tid = journal->j_committing_transaction->t_tid;
             spin_unlock(&journal->j_list_lock);
             write_unlock(&journal->j_state_lock);
             if (chkpt) {
                 jbd2_log_do_checkpoint(journal);
             } else if (jbd2_cleanup_journal_tail(journal) == 0) {
                 /* We were able to recover space; yay! */
                 ;
             } else if (tid) {
                 /*
                  * jbd2_journal_commit_transaction() may want
                  * to take the checkpoint_mutex if JBD2_FLUSHED
                  * is set.  So we need to temporarily drop it.
                  */
                 mutex_unlock(&journal->j_checkpoint_mutex);
                 jbd2_log_wait_commit(journal, tid);
                 write_lock(&journal->j_state_lock);
                 continue;
             } else {
                 printk(KERN_ERR "%s: needed %d blocks and "
                        "only had %d space available\n",
                        __func__, nblocks, space_left);
                 printk(KERN_ERR "%s: no way to get more "
                        "journal space in %s\n", __func__,
                        journal->j_devname);
                 WARN_ON(1);
                 jbd2_journal_abort(journal, -EIO);
             }
             write_lock(&journal->j_state_lock);
         } else {
             spin_unlock(&journal->j_list_lock);
         }
         mutex_unlock(&journal->j_checkpoint_mutex);
     }
 }
 
 static void
 __flush_batch(journal_t *journal, int *batch_count)
 {
     int i;
     struct blk_plug plug;
 
     blk_start_plug(&plug);
     for (i = 0; i < *batch_count; i++)
         write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
     blk_finish_plug(&plug);
 
     for (i = 0; i < *batch_count; i++) {
         struct buffer_head *bh = journal->j_chkpt_bhs[i];
         BUFFER_TRACE(bh, "brelse");
         __brelse(bh);
     }
     *batch_count = 0;
 }
 
 /*
  * Perform an actual checkpoint. We take the first transaction on the
  * list of transactions to be checkpointed and send all its buffers
  * to disk. We submit larger chunks of data at once.
  *
  * The journal should be locked before calling this function.
  * Called with j_checkpoint_mutex held.
  */
 int jbd2_log_do_checkpoint(journal_t *journal)
 {
     struct journal_head *jh;
     struct buffer_head  *bh;
     transaction_t       *transaction;
     tid_t           this_tid;
     int         result, batch_count = 0;
 
     jbd2_debug(1, "Start checkpoint\n");
 
     /*
      * First thing: if there are any transactions in the log which
      * don't need checkpointing, just eliminate them from the
      * journal straight away.
      */
     result = jbd2_cleanup_journal_tail(journal);
     trace_jbd2_checkpoint(journal, result);
     jbd2_debug(1, "cleanup_journal_tail returned %d\n", result);
     if (result <= 0)
         return result;
 
     /*
      * OK, we need to start writing disk blocks.  Take one transaction
      * and write it.
      */
     spin_lock(&journal->j_list_lock);
     if (!journal->j_checkpoint_transactions)
         goto out;
     transaction = journal->j_checkpoint_transactions;
     if (transaction->t_chp_stats.cs_chp_time == 0)
         transaction->t_chp_stats.cs_chp_time = jiffies;
     this_tid = transaction->t_tid;
 restart:
     /*
      * If someone cleaned up this transaction while we slept, we're
      * done (maybe it's a new transaction, but it fell at the same
      * address).
      */
     if (journal->j_checkpoint_transactions != transaction ||
         transaction->t_tid != this_tid)
         goto out;
 
     /* checkpoint all of the transaction's buffers */
     while (transaction->t_checkpoint_list) {
         jh = transaction->t_checkpoint_list;
         bh = jh2bh(jh);
 
         if (buffer_locked(bh)) {
             get_bh(bh);
             spin_unlock(&journal->j_list_lock);
             wait_on_buffer(bh);
             /* the journal_head may have gone by now */
             BUFFER_TRACE(bh, "brelse");
             __brelse(bh);
             goto retry;
         }
         if (jh->b_transaction != NULL) {
             transaction_t *t = jh->b_transaction;
             tid_t tid = t->t_tid;
 
             transaction->t_chp_stats.cs_forced_to_close++;
             spin_unlock(&journal->j_list_lock);
             if (unlikely(journal->j_flags & JBD2_UNMOUNT))
                 /*
                  * The journal thread is dead; so
                  * starting and waiting for a commit
                  * to finish will cause us to wait for
                  * a _very_ long time.
                  */
                 printk(KERN_ERR
         "JBD2: %s: Waiting for Godot: block %llu\n",
         journal->j_devname, (unsigned long long) bh->b_blocknr);
 
             if (batch_count)
                 __flush_batch(journal, &batch_count);
             jbd2_log_start_commit(journal, tid);
             /*
              * jbd2_journal_commit_transaction() may want
              * to take the checkpoint_mutex if JBD2_FLUSHED
              * is set, jbd2_update_log_tail() called by
              * jbd2_journal_commit_transaction() may also take
              * checkpoint_mutex.  So we need to temporarily
              * drop it.
              */
             mutex_unlock(&journal->j_checkpoint_mutex);
             jbd2_log_wait_commit(journal, tid);
             mutex_lock_io(&journal->j_checkpoint_mutex);
             spin_lock(&journal->j_list_lock);
             goto restart;
         }
         if (!buffer_dirty(bh)) {
             BUFFER_TRACE(bh, "remove from checkpoint");
             if (__jbd2_journal_remove_checkpoint(jh))
                 /* The transaction was released; we're done */
                 goto out;
             continue;
         }
         /*
          * Important: we are about to write the buffer, and
          * possibly block, while still holding the journal
          * lock.  We cannot afford to let the transaction
          * logic start messing around with this buffer before
          * we write it to disk, as that would break
          * recoverability.
          */
         BUFFER_TRACE(bh, "queue");
         get_bh(bh);
         J_ASSERT_BH(bh, !buffer_jwrite(bh));
         journal->j_chkpt_bhs[batch_count++] = bh;
         __buffer_relink_io(jh);
         transaction->t_chp_stats.cs_written++;
         if ((batch_count == JBD2_NR_BATCH) ||
             need_resched() ||
             spin_needbreak(&journal->j_list_lock))
             goto unlock_and_flush;
     }
 
     if (batch_count) {
         unlock_and_flush:
             spin_unlock(&journal->j_list_lock);
         retry:
             if (batch_count)
                 __flush_batch(journal, &batch_count);
             spin_lock(&journal->j_list_lock);
             goto restart;
     }
 
     /*
      * Now we issued all of the transaction's buffers, let's deal
      * with the buffers that are out for I/O.
      */
 restart2:
     /* Did somebody clean up the transaction in the meanwhile? */
     if (journal->j_checkpoint_transactions != transaction ||
         transaction->t_tid != this_tid)
         goto out;
 
     while (transaction->t_checkpoint_io_list) {
         jh = transaction->t_checkpoint_io_list;
         bh = jh2bh(jh);
         if (buffer_locked(bh)) {
             get_bh(bh);
             spin_unlock(&journal->j_list_lock);
             wait_on_buffer(bh);
             /* the journal_head may have gone by now */
             BUFFER_TRACE(bh, "brelse");
             __brelse(bh);
             spin_lock(&journal->j_list_lock);
             goto restart2;
         }
 
         /*
          * Now in whatever state the buffer currently is, we
          * know that it has been written out and so we can
          * drop it from the list
          */
         if (__jbd2_journal_remove_checkpoint(jh))
             break;
     }
 out:
     spin_unlock(&journal->j_list_lock);
     result = jbd2_cleanup_journal_tail(journal);
 
     return (result < 0) ? result : 0;
 }
 
 /*
  * Check the list of checkpoint transactions for the journal to see if
  * we have already got rid of any since the last update of the log tail
  * in the journal superblock.  If so, we can instantly roll the
  * superblock forward to remove those transactions from the log.
  *
  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
  *
  * Called with the journal lock held.
  *
  * This is the only part of the journaling code which really needs to be
  * aware of transaction aborts.  Checkpointing involves writing to the
  * main filesystem area rather than to the journal, so it can proceed
  * even in abort state, but we must not update the super block if
  * checkpointing may have failed.  Otherwise, we would lose some metadata
  * buffers which should be written-back to the filesystem.
  */
 
 int jbd2_cleanup_journal_tail(journal_t *journal)
 {
     tid_t       first_tid;
     unsigned long   blocknr;
 
     if (is_journal_aborted(journal))
         return -EIO;
 
     if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
         return 1;
     J_ASSERT(blocknr != 0);
 
     /*
      * We need to make sure that any blocks that were recently written out
      * --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
      * we drop the transactions from the journal. It's unlikely this will
      * be necessary, especially with an appropriately sized journal, but we
      * need this to guarantee correctness.  Fortunately
      * jbd2_cleanup_journal_tail() doesn't get called all that often.
      */
     if (journal->j_flags & JBD2_BARRIER)
         blkdev_issue_flush(journal->j_fs_dev);
 
     return __jbd2_update_log_tail(journal, first_tid, blocknr);
 }
 
 
 /* Checkpoint list management */
 
 /*
  * journal_clean_one_cp_list
  *
  * Find all the written-back checkpoint buffers in the given list and
  * release them. If 'destroy' is set, clean all buffers unconditionally.
  *
  * Called with j_list_lock held.
  * Returns 1 if we freed the transaction, 0 otherwise.
  */
 static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
 {
     struct journal_head *last_jh;
     struct journal_head *next_jh = jh;
 
     if (!jh)
         return 0;
 
     last_jh = jh->b_cpprev;
     do {
         jh = next_jh;
         next_jh = jh->b_cpnext;
 
         if (!destroy && __cp_buffer_busy(jh))
             return 0;
 
         if (__jbd2_journal_remove_checkpoint(jh))
             return 1;
         /*
          * This function only frees up some memory
          * if possible so we dont have an obligation
          * to finish processing. Bail out if preemption
          * requested:
          */
         if (need_resched())
             return 0;
     } while (jh != last_jh);
 
     return 0;
 }
 
 /*
  * journal_shrink_one_cp_list
  *
  * Find 'nr_to_scan' written-back checkpoint buffers in the given list
  * and try to release them. If the whole transaction is released, set
  * the 'released' parameter. Return the number of released checkpointed
  * buffers.
  *
  * Called with j_list_lock held.
  */
 static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
                         unsigned long *nr_to_scan,
                         bool *released)
 {
     struct journal_head *last_jh;
     struct journal_head *next_jh = jh;
     unsigned long nr_freed = 0;
     int ret;
 
     if (!jh || *nr_to_scan == 0)
         return 0;
 
     last_jh = jh->b_cpprev;
     do {
         jh = next_jh;
         next_jh = jh->b_cpnext;
 
         (*nr_to_scan)--;
         if (__cp_buffer_busy(jh))
             continue;
 
         nr_freed++;
         ret = __jbd2_journal_remove_checkpoint(jh);
         if (ret) {
             *released = true;
             break;
         }
 
         if (need_resched())
             break;
     } while (jh != last_jh && *nr_to_scan);
 
     return nr_freed;
 }
 
 /*
  * jbd2_journal_shrink_checkpoint_list
  *
  * Find 'nr_to_scan' written-back checkpoint buffers in the journal
  * and try to release them. Return the number of released checkpointed
  * buffers.
  *
  * Called with j_list_lock held.
  */
 unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
                           unsigned long *nr_to_scan)
 {
     transaction_t *transaction, *last_transaction, *next_transaction;
     bool released;
     tid_t first_tid = 0, last_tid = 0, next_tid = 0;
     tid_t tid = 0;
     unsigned long nr_freed = 0;
     unsigned long nr_scanned = *nr_to_scan;
 
 again:
     spin_lock(&journal->j_list_lock);
     if (!journal->j_checkpoint_transactions) {
         spin_unlock(&journal->j_list_lock);
         goto out;
     }
 
     /*
      * Get next shrink transaction, resume previous scan or start
      * over again. If some others do checkpoint and drop transaction
      * from the checkpoint list, we ignore saved j_shrink_transaction
      * and start over unconditionally.
      */
     if (journal->j_shrink_transaction)
         transaction = journal->j_shrink_transaction;
     else
         transaction = journal->j_checkpoint_transactions;
 
     if (!first_tid)
         first_tid = transaction->t_tid;
     last_transaction = journal->j_checkpoint_transactions->t_cpprev;
     next_transaction = transaction;
     last_tid = last_transaction->t_tid;
     do {
         transaction = next_transaction;
         next_transaction = transaction->t_cpnext;
         tid = transaction->t_tid;
         released = false;
 
         nr_freed += journal_shrink_one_cp_list(transaction->t_checkpoint_list,
                                nr_to_scan, &released);
         if (*nr_to_scan == 0)
             break;
         if (need_resched() || spin_needbreak(&journal->j_list_lock))
             break;
         if (released)
             continue;
 
         nr_freed += journal_shrink_one_cp_list(transaction->t_checkpoint_io_list,
                                nr_to_scan, &released);
         if (*nr_to_scan == 0)
             break;
         if (need_resched() || spin_needbreak(&journal->j_list_lock))
             break;
     } while (transaction != last_transaction);
 
     if (transaction != last_transaction) {
         journal->j_shrink_transaction = next_transaction;
         next_tid = next_transaction->t_tid;
     } else {
         journal->j_shrink_transaction = NULL;
         next_tid = 0;
     }
 
     spin_unlock(&journal->j_list_lock);
     cond_resched();
 
     if (*nr_to_scan && next_tid)
         goto again;
 out:
     nr_scanned -= *nr_to_scan;
     trace_jbd2_shrink_checkpoint_list(journal, first_tid, tid, last_tid,
                       nr_freed, nr_scanned, next_tid);
 
     return nr_freed;
 }
 
 /*
  * journal_clean_checkpoint_list
  *
  * Find all the written-back checkpoint buffers in the journal and release them.
  * If 'destroy' is set, release all buffers unconditionally.
  *
  * Called with j_list_lock held.
  */
 void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
 {
     transaction_t *transaction, *last_transaction, *next_transaction;
     int ret;
 
     transaction = journal->j_checkpoint_transactions;
     if (!transaction)
         return;
 
     last_transaction = transaction->t_cpprev;
     next_transaction = transaction;
     do {
         transaction = next_transaction;
         next_transaction = transaction->t_cpnext;
         ret = journal_clean_one_cp_list(transaction->t_checkpoint_list,
                         destroy);
         /*
          * This function only frees up some memory if possible so we
          * dont have an obligation to finish processing. Bail out if
          * preemption requested:
          */
         if (need_resched())
             return;
         if (ret)
             continue;
         /*
          * It is essential that we are as careful as in the case of
          * t_checkpoint_list with removing the buffer from the list as
          * we can possibly see not yet submitted buffers on io_list
          */
         ret = journal_clean_one_cp_list(transaction->
                 t_checkpoint_io_list, destroy);
         if (need_resched())
             return;
         /*
          * Stop scanning if we couldn't free the transaction. This
          * avoids pointless scanning of transactions which still
          * weren't checkpointed.
          */
         if (!ret)
             return;
     } while (transaction != last_transaction);
 }
 
 /*
  * Remove buffers from all checkpoint lists as journal is aborted and we just
  * need to free memory
  */
 void jbd2_journal_destroy_checkpoint(journal_t *journal)
 {
     /*
      * We loop because __jbd2_journal_clean_checkpoint_list() may abort
      * early due to a need of rescheduling.
      */
     while (1) {
         spin_lock(&journal->j_list_lock);
         if (!journal->j_checkpoint_transactions) {
             spin_unlock(&journal->j_list_lock);
             break;
         }
         __jbd2_journal_clean_checkpoint_list(journal, true);
         spin_unlock(&journal->j_list_lock);
         cond_resched();
     }
 }
 
 /*
  * journal_remove_checkpoint: called after a buffer has been committed
  * to disk (either by being write-back flushed to disk, or being
  * committed to the log).
  *
  * We cannot safely clean a transaction out of the log until all of the
  * buffer updates committed in that transaction have safely been stored
  * elsewhere on disk.  To achieve this, all of the buffers in a
  * transaction need to be maintained on the transaction's checkpoint
  * lists until they have been rewritten, at which point this function is
  * called to remove the buffer from the existing transaction's
  * checkpoint lists.
  *
  * The function returns 1 if it frees the transaction, 0 otherwise.
  * The function can free jh and bh.
  *
  * This function is called with j_list_lock held.
  */
 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 {
     struct transaction_chp_stats_s *stats;
     transaction_t *transaction;
     journal_t *journal;
     struct buffer_head *bh = jh2bh(jh);
 
     JBUFFER_TRACE(jh, "entry");
 
     transaction = jh->b_cp_transaction;
     if (!transaction) {
         JBUFFER_TRACE(jh, "not on transaction");
         return 0;
     }
     journal = transaction->t_journal;
 
     JBUFFER_TRACE(jh, "removing from transaction");
 
     /*
      * If we have failed to write the buffer out to disk, the filesystem
      * may become inconsistent. We cannot abort the journal here since
      * we hold j_list_lock and we have to be careful about races with
      * jbd2_journal_destroy(). So mark the writeback IO error in the
      * journal here and we abort the journal later from a better context.
      */
     if (buffer_write_io_error(bh))
         set_bit(JBD2_CHECKPOINT_IO_ERROR, &journal->j_atomic_flags);
 
     __buffer_unlink(jh);
     jh->b_cp_transaction = NULL;
     percpu_counter_dec(&journal->j_checkpoint_jh_count);
     jbd2_journal_put_journal_head(jh);
 
     /* Is this transaction empty? */
     if (transaction->t_checkpoint_list || transaction->t_checkpoint_io_list)
         return 0;
 
     /*
      * There is one special case to worry about: if we have just pulled the
      * buffer off a running or committing transaction's checkpoing list,
      * then even if the checkpoint list is empty, the transaction obviously
      * cannot be dropped!
      *
      * The locking here around t_state is a bit sleazy.
      * See the comment at the end of jbd2_journal_commit_transaction().
      */
     if (transaction->t_state != T_FINISHED)
         return 0;
 
     /*
      * OK, that was the last buffer for the transaction, we can now
      * safely remove this transaction from the log.
      */
     stats = &transaction->t_chp_stats;
     if (stats->cs_chp_time)
         stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
                             jiffies);
     trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
                     transaction->t_tid, stats);
 
     __jbd2_journal_drop_transaction(journal, transaction);
     jbd2_journal_free_transaction(transaction);
     return 1;
 }
 
 /*
  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
  * list so that we know when it is safe to clean the transaction out of
  * the log.
  *
  * Called with the journal locked.
  * Called with j_list_lock held.
  */
 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
                    transaction_t *transaction)
 {
     JBUFFER_TRACE(jh, "entry");
     J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
     J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 
     /* Get reference for checkpointing transaction */
     jbd2_journal_grab_journal_head(jh2bh(jh));
     jh->b_cp_transaction = transaction;
 
     if (!transaction->t_checkpoint_list) {
         jh->b_cpnext = jh->b_cpprev = jh;
     } else {
         jh->b_cpnext = transaction->t_checkpoint_list;
         jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
         jh->b_cpprev->b_cpnext = jh;
         jh->b_cpnext->b_cpprev = jh;
     }
     transaction->t_checkpoint_list = jh;
     percpu_counter_inc(&transaction->t_journal->j_checkpoint_jh_count);
 }
 
 /*
  * We've finished with this transaction structure: adios...
  *
  * The transaction must have no links except for the checkpoint by this
  * point.
  *
  * Called with the journal locked.
  * Called with j_list_lock held.
  */
 
 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 {
     assert_spin_locked(&journal->j_list_lock);
 
     journal->j_shrink_transaction = NULL;
     if (transaction->t_cpnext) {
         transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
         transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
         if (journal->j_checkpoint_transactions == transaction)
             journal->j_checkpoint_transactions =
                 transaction->t_cpnext;
         if (journal->j_checkpoint_transactions == transaction)
             journal->j_checkpoint_transactions = NULL;
     }
 
     J_ASSERT(transaction->t_state == T_FINISHED);
     J_ASSERT(transaction->t_buffers == NULL);
     J_ASSERT(transaction->t_forget == NULL);
     J_ASSERT(transaction->t_shadow_list == NULL);
     J_ASSERT(transaction->t_checkpoint_list == NULL);
     J_ASSERT(transaction->t_checkpoint_io_list == NULL);
     J_ASSERT(atomic_read(&transaction->t_updates) == 0);
     J_ASSERT(journal->j_committing_transaction != transaction);
     J_ASSERT(journal->j_running_transaction != transaction);
 
     trace_jbd2_drop_transaction(journal, transaction);
 
     jbd2_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 }

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