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

NAME

struct_journal_s - this 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;


  spinlock_t j_state_lock;


  int j_barrier_count;


  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_logspace;


  wait_queue_head_t j_wait_done_commit;


  wait_queue_head_t j_wait_checkpoint;


  wait_queue_head_t j_wait_commit;


  wait_queue_head_t j_wait_updates;


  struct mutex j_checkpoint_mutex;


  unsigned int j_head;


  unsigned int j_tail;


  unsigned int j_free;


  unsigned int j_first;


  unsigned int j_last;


  struct block_device * j_dev;


  int j_blocksize;


  unsigned int j_blk_offset;


  struct block_device * j_fs_dev;


  unsigned int j_maxlen;


  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 jbd_revoke_table_s * j_revoke;


  struct jbd_revoke_table_s * j_revoke_table[2];


  struct buffer_head ** j_wbuf;


  int j_wbufsize;


  pid_t j_last_sync_writer;


  u64 j_average_commit_time;


  void * j_private;
};

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_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_logspace

Wait queue for waiting for checkpointing to complete

j_wait_done_commit

Wait queue for waiting for commit to complete

j_wait_checkpoint

Wait queue to trigger checkpointing

j_wait_commit

Wait queue to trigger commit

j_wait_updates

Wait queue to wait for updates to complete

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_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 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_average_commit_time

the average amount of time in nanoseconds it takes to commit a transaction to the disk.

j_private

An opaque pointer to fs-private information.

AUTHORS

Roger Gammans <rgammans@computer-surgery.co.uk>

Author.

Stephen Tweedie <sct@redhat.com>

Author.

COPYRIGHT

May 2024 Kernel Hackers Manual 2.6.