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STRUCT JOURNAL_S(9) The Linux Journalling API STRUCT JOURNAL_S(9)

NAME

struct_journal_s - The journal_s type is the concrete type associated with journal_t.

SYNOPSIS

struct journal_s {
  unsigned long j_flags;
  int j_errno;
  struct buffer_head * j_sb_buffer;
  journal_superblock_t * j_superblock;
  int j_format_version;
  rwlock_t j_state_lock;
  int j_barrier_count;
  struct mutex j_barrier;
  transaction_t * j_running_transaction;
  transaction_t * j_committing_transaction;
  transaction_t * j_checkpoint_transactions;
  wait_queue_head_t j_wait_transaction_locked;
  wait_queue_head_t j_wait_done_commit;
  wait_queue_head_t j_wait_commit;
  wait_queue_head_t j_wait_updates;
  wait_queue_head_t j_wait_reserved;
  struct mutex j_checkpoint_mutex;
  unsigned long j_head;
  unsigned long j_tail;
  unsigned long j_free;
  unsigned long j_first;
  unsigned long j_last;
  struct block_device * j_dev;
  int j_blocksize;
  unsigned long long j_blk_offset;
  struct block_device * j_fs_dev;
  unsigned int j_maxlen;
  atomic_t j_reserved_credits;
  spinlock_t j_list_lock;
  struct inode * j_inode;
  tid_t j_tail_sequence;
  tid_t j_transaction_sequence;
  tid_t j_commit_sequence;
  tid_t j_commit_request;
  __u8 j_uuid[16];
  struct task_struct * j_task;
  int j_max_transaction_buffers;
  unsigned long j_commit_interval;
  struct timer_list j_commit_timer;
  spinlock_t j_revoke_lock;
  struct jbd2_revoke_table_s * j_revoke;
  struct jbd2_revoke_table_s * j_revoke_table[2];
  struct buffer_head ** j_wbuf;
  int j_wbufsize;
  pid_t j_last_sync_writer;
  spinlock_t j_history_lock;
  struct proc_dir_entry * j_proc_entry;
  struct transaction_stats_s j_stats;
  void * j_private;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
  struct lockdep_map j_trans_commit_map;
#endif
};

MEMBERS

j_flags
General journaling state flags
j_errno
Is there an outstanding uncleared error on the journal (from a prior abort)?
j_sb_buffer
First part of superblock buffer
j_superblock
Second part of superblock buffer
j_format_version
Version of the superblock format
j_state_lock
Protect the various scalars in the journal
j_barrier_count
Number of processes waiting to create a barrier lock
j_barrier
The barrier lock itself
j_running_transaction
The current running transaction..
j_committing_transaction
the transaction we are pushing to disk
j_checkpoint_transactions
a linked circular list of all transactions waiting for checkpointing
j_wait_transaction_locked
Wait queue for waiting for a locked transaction to start committing, or for a barrier lock to be released
j_wait_done_commit
Wait queue for waiting for commit to complete
j_wait_commit
Wait queue to trigger commit
j_wait_updates
Wait queue to wait for updates to complete
j_wait_reserved
Wait queue to wait for reserved buffer credits to drop
j_checkpoint_mutex
Mutex for locking against concurrent checkpoints
j_head
Journal head - identifies the first unused block in the journal
j_tail
Journal tail - identifies the oldest still-used block in the journal.
j_free
Journal free - how many free blocks are there in the journal?
j_first
The block number of the first usable block
j_last
The block number one beyond the last usable block
j_dev
Device where we store the journal
j_blocksize
blocksize for the location where we store the journal.
j_blk_offset
starting block offset for into the device where we store the journal
j_fs_dev
Device which holds the client fs. For internal journal this will be equal to j_dev
j_maxlen
Total maximum capacity of the journal region on disk.
j_reserved_credits
Number of buffers reserved from the running transaction
j_list_lock
Protects the buffer lists and internal buffer state.
j_inode
Optional inode where we store the journal. If present, all journal block numbers are mapped into this inode via bmap.
j_tail_sequence
Sequence number of the oldest transaction in the log
j_transaction_sequence
Sequence number of the next transaction to grant
j_commit_sequence
Sequence number of the most recently committed transaction
j_commit_request
Sequence number of the most recent transaction wanting commit
j_uuid[16]
Uuid of client object.
j_task
Pointer to the current commit thread for this journal
j_max_transaction_buffers
Maximum number of metadata buffers to allow in a single compound commit transaction
j_commit_interval
What is the maximum transaction lifetime before we begin a commit?
j_commit_timer
The timer used to wakeup the commit thread
j_revoke_lock
Protect the revoke table
j_revoke
The revoke table - maintains the list of revoked blocks in the current transaction.
j_revoke_table[2]
alternate revoke tables for j_revoke
j_wbuf
array of buffer_heads for jbd2_journal_commit_transaction
j_wbufsize
maximum number of buffer_heads allowed in j_wbuf, the number that will fit in j_blocksize
j_last_sync_writer
most recent pid which did a synchronous write
j_history_lock
Protect the transactions statistics history
j_proc_entry
procfs entry for the jbd statistics directory
j_stats
Overall statistics
j_private
An opaque pointer to fs-private information.
j_trans_commit_map
Lockdep entity to track transaction commit dependencies

AUTHORS

Roger Gammans <rgammans@computer-surgery.co.uk>
Author.
Stephen Tweedie <sct@redhat.com>
Author.

COPYRIGHT

January 2017 Kernel Hackers Manual 4.8.