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 struct buffer_head;
  16
  17 struct journal_head {
  18         /*
  19          * Points back to our buffer_head. [jbd_lock_bh_journal_head()]
  20          */
  21         struct buffer_head *b_bh;
  22
  23         /*
  24          * Reference count - see description in journal.c
  25          * [jbd_lock_bh_journal_head()]
  26          */
  27         int b_jcount;
  28
  29         /*
  30          * Journalling list for this buffer [jbd_lock_bh_state()]
  31          */
  32         unsigned b_jlist;
  33
  34         /*
  35          * This flag signals the buffer has been modified by
  36          * the currently running transaction
  37          * [jbd_lock_bh_state()]
  38          */
  39         unsigned b_modified;
  40
  41         /*
  42          * Copy of the buffer data frozen for writing to the log.
  43          * [jbd_lock_bh_state()]
  44          */
  45         char *b_frozen_data;
  46
  47         /*
  48          * Pointer to a saved copy of the buffer containing no uncommitted
  49          * deallocation references, so that allocations can avoid overwriting
  50          * uncommitted deletes. [jbd_lock_bh_state()]
  51          */
  52         char *b_committed_data;
  53
  54         /*
  55          * Pointer to the compound transaction which owns this buffer's
  56          * metadata: either the running transaction or the committing
  57          * transaction (if there is one).  Only applies to buffers on a
  58          * transaction's data or metadata journaling list.
  59          * [j_list_lock] [jbd_lock_bh_state()]
  60          */
  61         transaction_t *b_transaction;
  62
  63         /*
  64          * Pointer to the running compound transaction which is currently
  65          * modifying the buffer's metadata, if there was already a transaction
  66          * committing it when the new transaction touched it.
  67          * [t_list_lock] [jbd_lock_bh_state()]
  68          */
  69         transaction_t *b_next_transaction;
  70
  71         /*
  72          * Doubly-linked list of buffers on a transaction's data, metadata or
  73          * forget queue. [t_list_lock] [jbd_lock_bh_state()]
  74          */
  75         struct journal_head *b_tnext, *b_tprev;
  76
  77         /*
  78          * Pointer to the compound transaction against which this buffer
  79          * is checkpointed.  Only dirty buffers can be checkpointed.
  80          * [j_list_lock]
  81          */
  82         transaction_t *b_cp_transaction;
  83
  84         /*
  85          * Doubly-linked list of buffers still remaining to be flushed
  86          * before an old transaction can be checkpointed.
  87          * [j_list_lock]
  88          */
  89         struct journal_head *b_cpnext, *b_cpprev;
  90 };
  91
  92 #endif          /* JOURNAL_HEAD_H_INCLUDED */