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
  13 typedef unsigned int            tid_t;          /* Unique transaction ID */
  14 typedef struct transaction_s    transaction_t;  /* Compound transaction type */
  15
  16
  17 struct buffer_head;
  18
  19 struct 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         unsigned 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          */
  70         transaction_t *b_transaction;
  71
  72         /*
  73          * Pointer to the running compound transaction which is currently
  74          * modifying the buffer's metadata, if there was already a transaction
  75          * committing it when the new transaction touched it.
  76          * [t_list_lock] [jbd_lock_bh_state()]
  77          */
  78         transaction_t *b_next_transaction;
  79
  80         /*
  81          * Doubly-linked list of buffers on a transaction's data, metadata or
  82          * forget queue. [t_list_lock] [jbd_lock_bh_state()]
  83          */
  84         struct journal_head *b_tnext, *b_tprev;
  85
  86         /*
  87          * Pointer to the compound transaction against which this buffer
  88          * is checkpointed.  Only dirty buffers can be checkpointed.
  89          * [j_list_lock]
  90          */
  91         transaction_t *b_cp_transaction;
  92
  93         /*
  94          * Doubly-linked list of buffers still remaining to be flushed
  95          * before an old transaction can be checkpointed.
  96          * [j_list_lock]
  97          */
  98         struct journal_head *b_cpnext, *b_cpprev;
  99
 100         /* Trigger type */
 101         struct jbd2_buffer_trigger_type *b_triggers;
 102
 103         /* Trigger type for the committing transaction's frozen data */
 104         struct jbd2_buffer_trigger_type *b_frozen_triggers;
 105 };
 106
 107 #endif          /* JOURNAL_HEAD_H_INCLUDED */