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

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 * include/linux/journal-head.h
   4 *
   5 * buffer_head fields for JBD
   6 *
   7 * 27 May 2001 Andrew Morton
   8 *      Created - pulled out of fs.h
   9 */
  10
  11#ifndef JOURNAL_HEAD_H_INCLUDED
  12#define JOURNAL_HEAD_H_INCLUDED
  13
  14#include <linux/spinlock.h>
  15
  16typedef unsigned int            tid_t;          /* Unique transaction ID */
  17typedef struct transaction_s    transaction_t;  /* Compound transaction type */
  18
  19
  20struct buffer_head;
  21
  22struct journal_head {
  23        /*
  24         * Points back to our buffer_head. [jbd_lock_bh_journal_head()]
  25         */
  26        struct buffer_head *b_bh;
  27
  28        /*
  29         * Protect the buffer head state
  30         */
  31        spinlock_t b_state_lock;
  32
  33        /*
  34         * Reference count - see description in journal.c
  35         * [jbd_lock_bh_journal_head()]
  36         */
  37        int b_jcount;
  38
  39        /*
  40         * Journalling list for this buffer [b_state_lock]
  41         * NOTE: We *cannot* combine this with b_modified into a bitfield
  42         * as gcc would then (which the C standard allows but which is
  43         * very unuseful) make 64-bit accesses to the bitfield and clobber
  44         * b_jcount if its update races with bitfield modification.
  45         */
  46        unsigned b_jlist;
  47
  48        /*
  49         * This flag signals the buffer has been modified by
  50         * the currently running transaction
  51         * [b_state_lock]
  52         */
  53        unsigned b_modified;
  54
  55        /*
  56         * Copy of the buffer data frozen for writing to the log.
  57         * [b_state_lock]
  58         */
  59        char *b_frozen_data;
  60
  61        /*
  62         * Pointer to a saved copy of the buffer containing no uncommitted
  63         * deallocation references, so that allocations can avoid overwriting
  64         * uncommitted deletes. [b_state_lock]
  65         */
  66        char *b_committed_data;
  67
  68        /*
  69         * Pointer to the compound transaction which owns this buffer's
  70         * metadata: either the running transaction or the committing
  71         * transaction (if there is one).  Only applies to buffers on a
  72         * transaction's data or metadata journaling list.
  73         * [j_list_lock] [b_state_lock]
  74         * Either of these locks is enough for reading, both are needed for
  75         * changes.
  76         */
  77        transaction_t *b_transaction;
  78
  79        /*
  80         * Pointer to the running compound transaction which is currently
  81         * modifying the buffer's metadata, if there was already a transaction
  82         * committing it when the new transaction touched it.
  83         * [t_list_lock] [b_state_lock]
  84         */
  85        transaction_t *b_next_transaction;
  86
  87        /*
  88         * Doubly-linked list of buffers on a transaction's data, metadata or
  89         * forget queue. [t_list_lock] [b_state_lock]
  90         */
  91        struct journal_head *b_tnext, *b_tprev;
  92
  93        /*
  94         * Pointer to the compound transaction against which this buffer
  95         * is checkpointed.  Only dirty buffers can be checkpointed.
  96         * [j_list_lock]
  97         */
  98        transaction_t *b_cp_transaction;
  99
 100        /*
 101         * Doubly-linked list of buffers still remaining to be flushed
 102         * before an old transaction can be checkpointed.
 103         * [j_list_lock]
 104         */
 105        struct journal_head *b_cpnext, *b_cpprev;
 106
 107        /* Trigger type */
 108        struct jbd2_buffer_trigger_type *b_triggers;
 109
 110        /* Trigger type for the committing transaction's frozen data */
 111        struct jbd2_buffer_trigger_type *b_frozen_triggers;
 112};
 113
 114#endif          /* JOURNAL_HEAD_H_INCLUDED */
 115