LXR linux/include/linux/journal-head.h

   1/*
   2 * include/linux/journal-head.h
   3 *
   4 * buffer_head fields for JBD
   5 *
   6 * 27 May 2001 Andrew Morton
   7 *      Created - pulled out of fs.h
   8 */
   9
  10#ifndef JOURNAL_HEAD_H_INCLUDED
  11#define JOURNAL_HEAD_H_INCLUDED
  12
  13typedef unsigned int            tid_t;          /* Unique transaction ID */
  14typedef struct transaction_s    transaction_t;  /* Compound transaction type */
  15
  16
  17struct buffer_head;
  18
  19struct journal_head {
  20        /*
  21         * Points back to our buffer_head. [jbd_lock_bh_journal_head()]
  22         */
  23        struct buffer_head *b_bh;
  24
  25        /*
  26         * Reference count - see description in journal.c
  27         * [jbd_lock_bh_journal_head()]
  28         */
  29        int b_jcount;
  30
  31        /*
  32         * Journalling list for this buffer [jbd_lock_bh_state()]
  33         */
  34        unsigned b_jlist;
  35
  36        /*
  37         * This flag signals the buffer has been modified by
  38         * the currently running transaction
  39         * [jbd_lock_bh_state()]
  40         */
  41        unsigned b_modified;
  42
  43        /*
  44         * This feild tracks the last transaction id in which this buffer
  45         * has been cowed
  46         * [jbd_lock_bh_state()]
  47         */
  48        tid_t b_cow_tid;
  49
  50        /*
  51         * Copy of the buffer data frozen for writing to the log.
  52         * [jbd_lock_bh_state()]
  53         */
  54        char *b_frozen_data;
  55
  56        /*
  57         * Pointer to a saved copy of the buffer containing no uncommitted
  58         * deallocation references, so that allocations can avoid overwriting
  59         * uncommitted deletes. [jbd_lock_bh_state()]
  60         */
  61        char *b_committed_data;
  62
  63        /*
  64         * Pointer to the compound transaction which owns this buffer's
  65         * metadata: either the running transaction or the committing
  66         * transaction (if there is one).  Only applies to buffers on a
  67         * transaction's data or metadata journaling list.
  68         * [j_list_lock] [jbd_lock_bh_state()]
  69         * Either of these locks is enough for reading, both are needed for
  70         * changes.
  71         */
  72        transaction_t *b_transaction;
  73
  74        /*
  75         * Pointer to the running compound transaction which is currently
  76         * modifying the buffer's metadata, if there was already a transaction
  77         * committing it when the new transaction touched it.
  78         * [t_list_lock] [jbd_lock_bh_state()]
  79         */
  80        transaction_t *b_next_transaction;
  81
  82        /*
  83         * Doubly-linked list of buffers on a transaction's data, metadata or
  84         * forget queue. [t_list_lock] [jbd_lock_bh_state()]
  85         */
  86        struct journal_head *b_tnext, *b_tprev;
  87
  88        /*
  89         * Pointer to the compound transaction against which this buffer
  90         * is checkpointed.  Only dirty buffers can be checkpointed.
  91         * [j_list_lock]
  92         */
  93        transaction_t *b_cp_transaction;
  94
  95        /*
  96         * Doubly-linked list of buffers still remaining to be flushed
  97         * before an old transaction can be checkpointed.
  98         * [j_list_lock]
  99         */
 100        struct journal_head *b_cpnext, *b_cpprev;
 101
 102        /* Trigger type */
 103        struct jbd2_buffer_trigger_type *b_triggers;
 104
 105        /* Trigger type for the committing transaction's frozen data */
 106        struct jbd2_buffer_trigger_type *b_frozen_triggers;
 107};
 108
 109#endif          /* JOURNAL_HEAD_H_INCLUDED */
 110