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         * NOTE: We *cannot* combine this with b_modified into a bitfield
  34         * as gcc would then (which the C standard allows but which is
  35         * very unuseful) make 64-bit accesses to the bitfield and clobber
  36         * b_jcount if its update races with bitfield modification.
  37         */
  38        unsigned b_jlist;
  39
  40        /*
  41         * This flag signals the buffer has been modified by
  42         * the currently running transaction
  43         * [jbd_lock_bh_state()]
  44         */
  45        unsigned b_modified;
  46
  47        /*
  48         * Copy of the buffer data frozen for writing to the log.
  49         * [jbd_lock_bh_state()]
  50         */
  51        char *b_frozen_data;
  52
  53        /*
  54         * Pointer to a saved copy of the buffer containing no uncommitted
  55         * deallocation references, so that allocations can avoid overwriting
  56         * uncommitted deletes. [jbd_lock_bh_state()]
  57         */
  58        char *b_committed_data;
  59
  60        /*
  61         * Pointer to the compound transaction which owns this buffer's
  62         * metadata: either the running transaction or the committing
  63         * transaction (if there is one).  Only applies to buffers on a
  64         * transaction's data or metadata journaling list.
  65         * [j_list_lock] [jbd_lock_bh_state()]
  66         * Either of these locks is enough for reading, both are needed for
  67         * changes.
  68         */
  69        transaction_t *b_transaction;
  70
  71        /*
  72         * Pointer to the running compound transaction which is currently
  73         * modifying the buffer's metadata, if there was already a transaction
  74         * committing it when the new transaction touched it.
  75         * [t_list_lock] [jbd_lock_bh_state()]
  76         */
  77        transaction_t *b_next_transaction;
  78
  79        /*
  80         * Doubly-linked list of buffers on a transaction's data, metadata or
  81         * forget queue. [t_list_lock] [jbd_lock_bh_state()]
  82         */
  83        struct journal_head *b_tnext, *b_tprev;
  84
  85        /*
  86         * Pointer to the compound transaction against which this buffer
  87         * is checkpointed.  Only dirty buffers can be checkpointed.
  88         * [j_list_lock]
  89         */
  90        transaction_t *b_cp_transaction;
  91
  92        /*
  93         * Doubly-linked list of buffers still remaining to be flushed
  94         * before an old transaction can be checkpointed.
  95         * [j_list_lock]
  96         */
  97        struct journal_head *b_cpnext, *b_cpprev;
  98
  99        /* Trigger type */
 100        struct jbd2_buffer_trigger_type *b_triggers;
 101
 102        /* Trigger type for the committing transaction's frozen data */
 103        struct jbd2_buffer_trigger_type *b_frozen_triggers;
 104};
 105
 106#endif          /* JOURNAL_HEAD_H_INCLUDED */
 107