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 typedef unsigned int tid_t; /* Unique transaction ID */ 15 typedef struct transaction_s transaction_t; /* Compound transaction type */ 16 17 18 struct buffer_head; 19 20 struct 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