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 13 typedef unsigned int tid_t; /* Unique transaction ID */ 14 typedef struct transaction_s transaction_t; /* Compound transaction type */ 15 16 17 struct buffer_head; 18 19 struct 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 */ 34 unsigned b_jlist:4; 35 36 /* 37 * This flag signals the buffer has been modified by 38 * the currently running transaction 39 * [jbd_lock_bh_state()] 40 */ 41 unsigned b_modified:1; 42 43 /* 44 * Copy of the buffer data frozen for writing to the log. 45 * [jbd_lock_bh_state()] 46 */ 47 char *b_frozen_data; 48 49 /* 50 * Pointer to a saved copy of the buffer containing no uncommitted 51 * deallocation references, so that allocations can avoid overwriting 52 * uncommitted deletes. [jbd_lock_bh_state()] 53 */ 54 char *b_committed_data; 55 56 /* 57 * Pointer to the compound transaction which owns this buffer's 58 * metadata: either the running transaction or the committing 59 * transaction (if there is one). Only applies to buffers on a 60 * transaction's data or metadata journaling list. 61 * [j_list_lock] [jbd_lock_bh_state()] 62 * Either of these locks is enough for reading, both are needed for 63 * changes. 64 */ 65 transaction_t *b_transaction; 66 67 /* 68 * Pointer to the running compound transaction which is currently 69 * modifying the buffer's metadata, if there was already a transaction 70 * committing it when the new transaction touched it. 71 * [t_list_lock] [jbd_lock_bh_state()] 72 */ 73 transaction_t *b_next_transaction; 74 75 /* 76 * Doubly-linked list of buffers on a transaction's data, metadata or 77 * forget queue. [t_list_lock] [jbd_lock_bh_state()] 78 */ 79 struct journal_head *b_tnext, *b_tprev; 80 81 /* 82 * Pointer to the compound transaction against which this buffer 83 * is checkpointed. Only dirty buffers can be checkpointed. 84 * [j_list_lock] 85 */ 86 transaction_t *b_cp_transaction; 87 88 /* 89 * Doubly-linked list of buffers still remaining to be flushed 90 * before an old transaction can be checkpointed. 91 * [j_list_lock] 92 */ 93 struct journal_head *b_cpnext, *b_cpprev; 94 95 /* Trigger type */ 96 struct jbd2_buffer_trigger_type *b_triggers; 97 98 /* Trigger type for the committing transaction's frozen data */ 99 struct jbd2_buffer_trigger_type *b_frozen_triggers; 100 }; 101 102 #endif /* JOURNAL_HEAD_H_INCLUDED */ 103