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 * NOTE: We *cannot* combine this with b_modified into a bitfield 34 * as gcc would then (which the C standard allows but which is 35 * very unuseful) make 64-bit accesses to the bitfield and clobber 36 * b_jcount if its update races with bitfield modification. 37 */ 38 unsigned b_jlist; 39 40 /* 41 * This flag signals the buffer has been modified by 42 * the currently running transaction 43 * [jbd_lock_bh_state()] 44 */ 45 unsigned b_modified; 46 47 /* 48 * Copy of the buffer data frozen for writing to the log. 49 * [jbd_lock_bh_state()] 50 */ 51 char *b_frozen_data; 52 53 /* 54 * Pointer to a saved copy of the buffer containing no uncommitted 55 * deallocation references, so that allocations can avoid overwriting 56 * uncommitted deletes. [jbd_lock_bh_state()] 57 */ 58 char *b_committed_data; 59 60 /* 61 * Pointer to the compound transaction which owns this buffer's 62 * metadata: either the running transaction or the committing 63 * transaction (if there is one). Only applies to buffers on a 64 * transaction's data or metadata journaling list. 65 * [j_list_lock] [jbd_lock_bh_state()] 66 * Either of these locks is enough for reading, both are needed for 67 * changes. 68 */ 69 transaction_t *b_transaction; 70 71 /* 72 * Pointer to the running compound transaction which is currently 73 * modifying the buffer's metadata, if there was already a transaction 74 * committing it when the new transaction touched it. 75 * [t_list_lock] [jbd_lock_bh_state()] 76 */ 77 transaction_t *b_next_transaction; 78 79 /* 80 * Doubly-linked list of buffers on a transaction's data, metadata or 81 * forget queue. [t_list_lock] [jbd_lock_bh_state()] 82 */ 83 struct journal_head *b_tnext, *b_tprev; 84 85 /* 86 * Pointer to the compound transaction against which this buffer 87 * is checkpointed. Only dirty buffers can be checkpointed. 88 * [j_list_lock] 89 */ 90 transaction_t *b_cp_transaction; 91 92 /* 93 * Doubly-linked list of buffers still remaining to be flushed 94 * before an old transaction can be checkpointed. 95 * [j_list_lock] 96 */ 97 struct journal_head *b_cpnext, *b_cpprev; 98 99 /* Trigger type */ 100 struct jbd2_buffer_trigger_type *b_triggers; 101 102 /* Trigger type for the committing transaction's frozen data */ 103 struct jbd2_buffer_trigger_type *b_frozen_triggers; 104 }; 105 106 #endif /* JOURNAL_HEAD_H_INCLUDED */ 107