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 AT computer-surgery.uk>
           Author.

       Stephen Tweedie <sct AT redhat.com>
           Author.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                       STRUCT JOURNAL_S(9)