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 16 typedef unsigned int tid_t; /* Unique transaction ID */ 17 typedef struct transaction_s transaction_t; /* Compound transaction type */ 18 19 20 struct buffer_head; 21 22 struct 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