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
  14typedef unsigned int            tid_t;          /* Unique transaction ID */
  15typedef struct transaction_s    transaction_t;  /* Compound transaction type */
  16
  17
  18struct buffer_head;
  19
  20struct journal_head {
  21        /*
  22         * Points back to our buffer_head. [jbd_lock_bh_journal_head()]
  23         */
  24        struct buffer_head *b_bh;
  25
  26        /*
  27         * Reference count - see description in journal.c
  28         * [jbd_lock_bh_journal_head()]
  29         */
  30        int b_jcount;
  31
  32        /*
  33         * Journalling list for this buffer [jbd_lock_bh_state()]
  34         * NOTE: We *cannot* combine this with b_modified into a bitfield
  35         * as gcc would then (which the C standard allows but which is
  36         * very unuseful) make 64-bit accesses to the bitfield and clobber
  37         * b_jcount if its update races with bitfield modification.
  38         */
  39        unsigned b_jlist;
  40
  41        /*
  42         * This flag signals the buffer has been modified by
  43         * the currently running transaction
  44         * [jbd_lock_bh_state()]
  45         */
  46        unsigned b_modified;
  47
  48        /*
  49         * Copy of the buffer data frozen for writing to the log.
  50         * [jbd_lock_bh_state()]
  51         */
  52        char *b_frozen_data;
  53
  54        /*
  55         * Pointer to a saved copy of the buffer containing no uncommitted
  56         * deallocation references, so that allocations can avoid overwriting
  57         * uncommitted deletes. [jbd_lock_bh_state()]
  58         */
  59        char *b_committed_data;
  60
  61        /*
  62         * Pointer to the compound transaction which owns this buffer's
  63         * metadata: either the running transaction or the committing
  64         * transaction (if there is one).  Only applies to buffers on a
  65         * transaction's data or metadata journaling list.
  66         * [j_list_lock] [jbd_lock_bh_state()]
  67         * Either of these locks is enough for reading, both are needed for
  68         * changes.
  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 */
 108