aboutsummaryrefslogblamecommitdiffstats
path: root/include/linux/jbd.h
blob: ff853b3173c6545a189da4c1ddd04a055c5218a0 (plain) (tree)
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917





























                                                                             
                               





















































































































































































































































































































































































































































































































































































































































































































































































































































































































                                                                                                               



















                                                                             
                                                         































































































































































                                                                               
/*
 * linux/include/linux/jbd.h
 * 
 * Written by Stephen C. Tweedie <sct@redhat.com>
 *
 * Copyright 1998-2000 Red Hat, Inc --- All Rights Reserved
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * Definitions for transaction data structures for the buffer cache
 * filesystem journaling support.
 */

#ifndef _LINUX_JBD_H
#define _LINUX_JBD_H

#if defined(CONFIG_JBD) || defined(CONFIG_JBD_MODULE) || !defined(__KERNEL__)

/* Allow this file to be included directly into e2fsprogs */
#ifndef __KERNEL__
#include "jfs_compat.h"
#define JFS_DEBUG
#define jfs_debug jbd_debug
#else

#include <linux/buffer_head.h>
#include <linux/journal-head.h>
#include <linux/stddef.h>
#include <linux/bit_spinlock.h>
#include <asm/semaphore.h>
#endif

#define journal_oom_retry 1

/*
 * Define JBD_PARANIOD_IOFAIL to cause a kernel BUG() if ext3 finds
 * certain classes of error which can occur due to failed IOs.  Under
 * normal use we want ext3 to continue after such errors, because
 * hardware _can_ fail, but for debugging purposes when running tests on
 * known-good hardware we may want to trap these errors.
 */
#undef JBD_PARANOID_IOFAIL

/*
 * The default maximum commit age, in seconds.
 */
#define JBD_DEFAULT_MAX_COMMIT_AGE 5

#ifdef CONFIG_JBD_DEBUG
/*
 * Define JBD_EXPENSIVE_CHECKING to enable more expensive internal
 * consistency checks.  By default we don't do this unless
 * CONFIG_JBD_DEBUG is on.
 */
#define JBD_EXPENSIVE_CHECKING
extern int journal_enable_debug;

#define jbd_debug(n, f, a...)						\
	do {								\
		if ((n) <= journal_enable_debug) {			\
			printk (KERN_DEBUG "(%s, %d): %s: ",		\
				__FILE__, __LINE__, __FUNCTION__);	\
		  	printk (f, ## a);				\
		}							\
	} while (0)
#else
#define jbd_debug(f, a...)	/**/
#endif

extern void * __jbd_kmalloc (const char *where, size_t size, int flags, int retry);
#define jbd_kmalloc(size, flags) \
	__jbd_kmalloc(__FUNCTION__, (size), (flags), journal_oom_retry)
#define jbd_rep_kmalloc(size, flags) \
	__jbd_kmalloc(__FUNCTION__, (size), (flags), 1)

#define JFS_MIN_JOURNAL_BLOCKS 1024

#ifdef __KERNEL__

/**
 * typedef handle_t - The handle_t type represents a single atomic update being performed by some process.
 *
 * All filesystem modifications made by the process go
 * through this handle.  Recursive operations (such as quota operations)
 * are gathered into a single update.
 *
 * The buffer credits field is used to account for journaled buffers
 * being modified by the running process.  To ensure that there is
 * enough log space for all outstanding operations, we need to limit the
 * number of outstanding buffers possible at any time.  When the
 * operation completes, any buffer credits not used are credited back to
 * the transaction, so that at all times we know how many buffers the
 * outstanding updates on a transaction might possibly touch. 
 * 
 * This is an opaque datatype.
 **/
typedef struct handle_s		handle_t;	/* Atomic operation type */


/**
 * typedef journal_t - The journal_t maintains all of the journaling state information for a single filesystem.
 *
 * journal_t is linked to from the fs superblock structure.
 * 
 * We use the journal_t to keep track of all outstanding transaction
 * activity on the filesystem, and to manage the state of the log
 * writing process.
 *
 * This is an opaque datatype.
 **/
typedef struct journal_s	journal_t;	/* Journal control structure */
#endif

/*
 * Internal structures used by the logging mechanism:
 */

#define JFS_MAGIC_NUMBER 0xc03b3998U /* The first 4 bytes of /dev/random! */

/*
 * On-disk structures
 */

/* 
 * Descriptor block types:
 */

#define JFS_DESCRIPTOR_BLOCK	1
#define JFS_COMMIT_BLOCK	2
#define JFS_SUPERBLOCK_V1	3
#define JFS_SUPERBLOCK_V2	4
#define JFS_REVOKE_BLOCK	5

/*
 * Standard header for all descriptor blocks:
 */
typedef struct journal_header_s
{
	__be32		h_magic;
	__be32		h_blocktype;
	__be32		h_sequence;
} journal_header_t;


/* 
 * The block tag: used to describe a single buffer in the journal 
 */
typedef struct journal_block_tag_s
{
	__be32		t_blocknr;	/* The on-disk block number */
	__be32		t_flags;	/* See below */
} journal_block_tag_t;

/* 
 * The revoke descriptor: used on disk to describe a series of blocks to
 * be revoked from the log 
 */
typedef struct journal_revoke_header_s
{
	journal_header_t r_header;
	__be32		 r_count;	/* Count of bytes used in the block */
} journal_revoke_header_t;


/* Definitions for the journal tag flags word: */
#define JFS_FLAG_ESCAPE		1	/* on-disk block is escaped */
#define JFS_FLAG_SAME_UUID	2	/* block has same uuid as previous */
#define JFS_FLAG_DELETED	4	/* block deleted by this transaction */
#define JFS_FLAG_LAST_TAG	8	/* last tag in this descriptor block */


/*
 * The journal superblock.  All fields are in big-endian byte order.
 */
typedef struct journal_superblock_s
{
/* 0x0000 */
	journal_header_t s_header;

/* 0x000C */
	/* Static information describing the journal */
	__be32	s_blocksize;		/* journal device blocksize */
	__be32	s_maxlen;		/* total blocks in journal file */
	__be32	s_first;		/* first block of log information */

/* 0x0018 */
	/* Dynamic information describing the current state of the log */
	__be32	s_sequence;		/* first commit ID expected in log */
	__be32	s_start;		/* blocknr of start of log */

/* 0x0020 */
	/* Error value, as set by journal_abort(). */
	__be32	s_errno;

/* 0x0024 */
	/* Remaining fields are only valid in a version-2 superblock */
	__be32	s_feature_compat; 	/* compatible feature set */
	__be32	s_feature_incompat; 	/* incompatible feature set */
	__be32	s_feature_ro_compat; 	/* readonly-compatible feature set */
/* 0x0030 */
	__u8	s_uuid[16];		/* 128-bit uuid for journal */

/* 0x0040 */
	__be32	s_nr_users;		/* Nr of filesystems sharing log */

	__be32	s_dynsuper;		/* Blocknr of dynamic superblock copy*/

/* 0x0048 */
	__be32	s_max_transaction;	/* Limit of journal blocks per trans.*/
	__be32	s_max_trans_data;	/* Limit of data blocks per trans. */

/* 0x0050 */
	__u32	s_padding[44];

/* 0x0100 */
	__u8	s_users[16*48];		/* ids of all fs'es sharing the log */
/* 0x0400 */
} journal_superblock_t;

#define JFS_HAS_COMPAT_FEATURE(j,mask)					\
	((j)->j_format_version >= 2 &&					\
	 ((j)->j_superblock->s_feature_compat & cpu_to_be32((mask))))
#define JFS_HAS_RO_COMPAT_FEATURE(j,mask)				\
	((j)->j_format_version >= 2 &&					\
	 ((j)->j_superblock->s_feature_ro_compat & cpu_to_be32((mask))))
#define JFS_HAS_INCOMPAT_FEATURE(j,mask)				\
	((j)->j_format_version >= 2 &&					\
	 ((j)->j_superblock->s_feature_incompat & cpu_to_be32((mask))))

#define JFS_FEATURE_INCOMPAT_REVOKE	0x00000001

/* Features known to this kernel version: */
#define JFS_KNOWN_COMPAT_FEATURES	0
#define JFS_KNOWN_ROCOMPAT_FEATURES	0
#define JFS_KNOWN_INCOMPAT_FEATURES	JFS_FEATURE_INCOMPAT_REVOKE

#ifdef __KERNEL__

#include <linux/fs.h>
#include <linux/sched.h>
#include <asm/bug.h>

#define JBD_ASSERTIONS
#ifdef JBD_ASSERTIONS
#define J_ASSERT(assert)						\
do {									\
	if (!(assert)) {						\
		printk (KERN_EMERG					\
			"Assertion failure in %s() at %s:%d: \"%s\"\n",	\
			__FUNCTION__, __FILE__, __LINE__, # assert);	\
		BUG();							\
	}								\
} while (0)

#if defined(CONFIG_BUFFER_DEBUG)
void buffer_assertion_failure(struct buffer_head *bh);
#define J_ASSERT_BH(bh, expr)						\
	do {								\
		if (!(expr))						\
			buffer_assertion_failure(bh);			\
		J_ASSERT(expr);						\
	} while (0)
#define J_ASSERT_JH(jh, expr)	J_ASSERT_BH(jh2bh(jh), expr)
#else
#define J_ASSERT_BH(bh, expr)	J_ASSERT(expr)
#define J_ASSERT_JH(jh, expr)	J_ASSERT(expr)
#endif

#else
#define J_ASSERT(assert)	do { } while (0)
#endif		/* JBD_ASSERTIONS */

#if defined(JBD_PARANOID_IOFAIL)
#define J_EXPECT(expr, why...)		J_ASSERT(expr)
#define J_EXPECT_BH(bh, expr, why...)	J_ASSERT_BH(bh, expr)
#define J_EXPECT_JH(jh, expr, why...)	J_ASSERT_JH(jh, expr)
#else
#define __journal_expect(expr, why...)					     \
	({								     \
		int val = (expr);					     \
		if (!val) {						     \
			printk(KERN_ERR					     \
				"EXT3-fs unexpected failure: %s;\n",# expr); \
			printk(KERN_ERR why "\n");			     \
		}							     \
		val;							     \
	})
#define J_EXPECT(expr, why...)		__journal_expect(expr, ## why)
#define J_EXPECT_BH(bh, expr, why...)	__journal_expect(expr, ## why)
#define J_EXPECT_JH(jh, expr, why...)	__journal_expect(expr, ## why)
#endif

enum jbd_state_bits {
	BH_JBD			/* Has an attached ext3 journal_head */
	  = BH_PrivateStart,
	BH_JWrite,		/* Being written to log (@@@ DEBUGGING) */
	BH_Freed,		/* Has been freed (truncated) */
	BH_Revoked,		/* Has been revoked from the log */
	BH_RevokeValid,		/* Revoked flag is valid */
	BH_JBDDirty,		/* Is dirty but journaled */
	BH_State,		/* Pins most journal_head state */
	BH_JournalHead,		/* Pins bh->b_private and jh->b_bh */
	BH_Unshadow,		/* Dummy bit, for BJ_Shadow wakeup filtering */
};

BUFFER_FNS(JBD, jbd)
BUFFER_FNS(JWrite, jwrite)
BUFFER_FNS(JBDDirty, jbddirty)
TAS_BUFFER_FNS(JBDDirty, jbddirty)
BUFFER_FNS(Revoked, revoked)
TAS_BUFFER_FNS(Revoked, revoked)
BUFFER_FNS(RevokeValid, revokevalid)
TAS_BUFFER_FNS(RevokeValid, revokevalid)
BUFFER_FNS(Freed, freed)

static inline struct buffer_head *jh2bh(struct journal_head *jh)
{
	return jh->b_bh;
}

static inline struct journal_head *bh2jh(struct buffer_head *bh)
{
	return bh->b_private;
}

static inline void jbd_lock_bh_state(struct buffer_head *bh)
{
	bit_spin_lock(BH_State, &bh->b_state);
}

static inline int jbd_trylock_bh_state(struct buffer_head *bh)
{
	return bit_spin_trylock(BH_State, &bh->b_state);
}

static inline int jbd_is_locked_bh_state(struct buffer_head *bh)
{
	return bit_spin_is_locked(BH_State, &bh->b_state);
}

static inline void jbd_unlock_bh_state(struct buffer_head *bh)
{
	bit_spin_unlock(BH_State, &bh->b_state);
}

static inline void jbd_lock_bh_journal_head(struct buffer_head *bh)
{
	bit_spin_lock(BH_JournalHead, &bh->b_state);
}

static inline void jbd_unlock_bh_journal_head(struct buffer_head *bh)
{
	bit_spin_unlock(BH_JournalHead, &bh->b_state);
}

struct jbd_revoke_table_s;

/**
 * struct handle_s - The handle_s type is the concrete type associated with
 *     handle_t.
 * @h_transaction: Which compound transaction is this update a part of?
 * @h_buffer_credits: Number of remaining buffers we are allowed to dirty.
 * @h_ref: Reference count on this handle
 * @h_err: Field for caller's use to track errors through large fs operations
 * @h_sync: flag for sync-on-close
 * @h_jdata: flag to force data journaling
 * @h_aborted: flag indicating fatal error on handle
 **/

/* Docbook can't yet cope with the bit fields, but will leave the documentation
 * in so it can be fixed later. 
 */

struct handle_s 
{
	/* Which compound transaction is this update a part of? */
	transaction_t		*h_transaction;

	/* Number of remaining buffers we are allowed to dirty: */
	int			h_buffer_credits;

	/* Reference count on this handle */
	int			h_ref;

	/* Field for caller's use to track errors through large fs */
	/* operations */
	int			h_err;

	/* Flags [no locking] */
	unsigned int	h_sync:		1;	/* sync-on-close */
	unsigned int	h_jdata:	1;	/* force data journaling */
	unsigned int	h_aborted:	1;	/* fatal error on handle */
};


/* The transaction_t type is the guts of the journaling mechanism.  It
 * tracks a compound transaction through its various states:
 *
 * RUNNING:	accepting new updates
 * LOCKED:	Updates still running but we don't accept new ones
 * RUNDOWN:	Updates are tidying up but have finished requesting
 *		new buffers to modify (state not used for now)
 * FLUSH:       All updates complete, but we are still writing to disk
 * COMMIT:      All data on disk, writing commit record
 * FINISHED:	We still have to keep the transaction for checkpointing.
 *
 * The transaction keeps track of all of the buffers modified by a
 * running transaction, and all of the buffers committed but not yet
 * flushed to home for finished transactions.
 */

/*
 * Lock ranking:
 *
 *    j_list_lock
 *      ->jbd_lock_bh_journal_head()	(This is "innermost")
 *
 *    j_state_lock
 *    ->jbd_lock_bh_state()
 *
 *    jbd_lock_bh_state()
 *    ->j_list_lock
 *
 *    j_state_lock
 *    ->t_handle_lock
 *
 *    j_state_lock
 *    ->j_list_lock			(journal_unmap_buffer)
 *
 */

struct transaction_s 
{
	/* Pointer to the journal for this transaction. [no locking] */
	journal_t		*t_journal;

	/* Sequence number for this transaction [no locking] */
	tid_t			t_tid;

	/*
	 * Transaction's current state
	 * [no locking - only kjournald alters this]
	 * FIXME: needs barriers
	 * KLUDGE: [use j_state_lock]
	 */
	enum {
		T_RUNNING,
		T_LOCKED,
		T_RUNDOWN,
		T_FLUSH,
		T_COMMIT,
		T_FINISHED 
	}			t_state;

	/*
	 * Where in the log does this transaction's commit start? [no locking]
	 */
	unsigned long		t_log_start;

	/* Number of buffers on the t_buffers list [j_list_lock] */
	int			t_nr_buffers;

	/*
	 * Doubly-linked circular list of all buffers reserved but not yet
	 * modified by this transaction [j_list_lock]
	 */
	struct journal_head	*t_reserved_list;

	/*
	 * Doubly-linked circular list of all buffers under writeout during
	 * commit [j_list_lock]
	 */
	struct journal_head	*t_locked_list;

	/*
	 * Doubly-linked circular list of all metadata buffers owned by this
	 * transaction [j_list_lock]
	 */
	struct journal_head	*t_buffers;

	/*
	 * Doubly-linked circular list of all data buffers still to be
	 * flushed before this transaction can be committed [j_list_lock]
	 */
	struct journal_head	*t_sync_datalist;

	/*
	 * Doubly-linked circular list of all forget buffers (superseded
	 * buffers which we can un-checkpoint once this transaction commits)
	 * [j_list_lock]
	 */
	struct journal_head	*t_forget;

	/*
	 * Doubly-linked circular list of all buffers still to be flushed before
	 * this transaction can be checkpointed. [j_list_lock]
	 */
	struct journal_head	*t_checkpoint_list;

	/*
	 * Doubly-linked circular list of temporary buffers currently undergoing
	 * IO in the log [j_list_lock]
	 */
	struct journal_head	*t_iobuf_list;

	/*
	 * Doubly-linked circular list of metadata buffers being shadowed by log
	 * IO.  The IO buffers on the iobuf list and the shadow buffers on this
	 * list match each other one for one at all times. [j_list_lock]
	 */
	struct journal_head	*t_shadow_list;

	/*
	 * Doubly-linked circular list of control buffers being written to the
	 * log. [j_list_lock]
	 */
	struct journal_head	*t_log_list;

	/*
	 * Protects info related to handles
	 */
	spinlock_t		t_handle_lock;

	/*
	 * Number of outstanding updates running on this transaction
	 * [t_handle_lock]
	 */
	int			t_updates;

	/*
	 * Number of buffers reserved for use by all handles in this transaction
	 * handle but not yet modified. [t_handle_lock]
	 */
	int			t_outstanding_credits;

	/*
	 * Forward and backward links for the circular list of all transactions
	 * awaiting checkpoint. [j_list_lock]
	 */
	transaction_t		*t_cpnext, *t_cpprev;

	/*
	 * When will the transaction expire (become due for commit), in jiffies?
	 * [no locking]
	 */
	unsigned long		t_expires;

	/*
	 * How many handles used this transaction? [t_handle_lock]
	 */
	int t_handle_count;

};

/**
 * struct journal_s - The journal_s type is the concrete type associated with
 *     journal_t.
 * @j_flags:  General journaling state flags
 * @j_errno:  Is there an outstanding uncleared error on the journal (from a
 *     prior abort)? 
 * @j_sb_buffer: First part of superblock buffer
 * @j_superblock: Second part of superblock buffer
 * @j_format_version: Version of the superblock format
 * @j_state_lock: Protect the various scalars in the journal
 * @j_barrier_count:  Number of processes waiting to create a barrier lock
 * @j_barrier: The barrier lock itself
 * @j_running_transaction: The current running transaction..
 * @j_committing_transaction: the transaction we are pushing to disk
 * @j_checkpoint_transactions: a linked circular list of all transactions
 *  waiting for checkpointing
 * @j_wait_transaction_locked: Wait queue for waiting for a locked transaction
 *  to start committing, or for a barrier lock to be released
 * @j_wait_logspace: Wait queue for waiting for checkpointing to complete
 * @j_wait_done_commit: Wait queue for waiting for commit to complete 
 * @j_wait_checkpoint:  Wait queue to trigger checkpointing
 * @j_wait_commit: Wait queue to trigger commit
 * @j_wait_updates: Wait queue to wait for updates to complete
 * @j_checkpoint_sem: Semaphore for locking against concurrent checkpoints
 * @j_head: Journal head - identifies the first unused block in the journal
 * @j_tail: Journal tail - identifies the oldest still-used block in the
 *  journal.
 * @j_free: Journal free - how many free blocks are there in the journal?
 * @j_first: The block number of the first usable block 
 * @j_last: The block number one beyond the last usable block
 * @j_dev: Device where we store the journal
 * @j_blocksize: blocksize for the location where we store the journal.
 * @j_blk_offset: starting block offset for into the device where we store the
 *     journal
 * @j_fs_dev: Device which holds the client fs.  For internal journal this will
 *     be equal to j_dev
 * @j_maxlen: Total maximum capacity of the journal region on disk.
 * @j_list_lock: Protects the buffer lists and internal buffer state.
 * @j_inode: Optional inode where we store the journal.  If present, all journal
 *     block numbers are mapped into this inode via bmap().
 * @j_tail_sequence:  Sequence number of the oldest transaction in the log 
 * @j_transaction_sequence: Sequence number of the next transaction to grant
 * @j_commit_sequence: Sequence number of the most recently committed
 *  transaction
 * @j_commit_request: Sequence number of the most recent transaction wanting
 *     commit 
 * @j_uuid: Uuid of client object.
 * @j_task: Pointer to the current commit thread for this journal
 * @j_max_transaction_buffers:  Maximum number of metadata buffers to allow in a
 *     single compound commit transaction
 * @j_commit_interval: What is the maximum transaction lifetime before we begin
 *  a commit?
 * @j_commit_timer:  The timer used to wakeup the commit thread
 * @j_revoke_lock: Protect the revoke table
 * @j_revoke: The revoke table - maintains the list of revoked blocks in the
 *     current transaction.
 * @j_revoke_table: alternate revoke tables for j_revoke
 * @j_private: An opaque pointer to fs-private information.
 */

struct journal_s
{
	/* General journaling state flags [j_state_lock] */
	unsigned long		j_flags;

	/*
	 * Is there an outstanding uncleared error on the journal (from a prior
	 * abort)? [j_state_lock]
	 */
	int			j_errno;

	/* The superblock buffer */
	struct buffer_head	*j_sb_buffer;
	journal_superblock_t	*j_superblock;

	/* Version of the superblock format */
	int			j_format_version;

	/*
	 * Protect the various scalars in the journal
	 */
	spinlock_t		j_state_lock;

	/*
	 * Number of processes waiting to create a barrier lock [j_state_lock]
	 */
	int			j_barrier_count;

	/* The barrier lock itself */
	struct semaphore	j_barrier;

	/*
	 * Transactions: The current running transaction...
	 * [j_state_lock] [caller holding open handle]
	 */
	transaction_t		*j_running_transaction;

	/*
	 * the transaction we are pushing to disk
	 * [j_state_lock] [caller holding open handle]
	 */
	transaction_t		*j_committing_transaction;

	/*
	 * ... and a linked circular list of all transactions waiting for
	 * checkpointing. [j_list_lock]
	 */
	transaction_t		*j_checkpoint_transactions;

	/*
	 * Wait queue for waiting for a locked transaction to start committing,
	 * or for a barrier lock to be released
	 */
	wait_queue_head_t	j_wait_transaction_locked;

	/* Wait queue for waiting for checkpointing to complete */
	wait_queue_head_t	j_wait_logspace;

	/* Wait queue for waiting for commit to complete */
	wait_queue_head_t	j_wait_done_commit;

	/* Wait queue to trigger checkpointing */
	wait_queue_head_t	j_wait_checkpoint;

	/* Wait queue to trigger commit */
	wait_queue_head_t	j_wait_commit;

	/* Wait queue to wait for updates to complete */
	wait_queue_head_t	j_wait_updates;

	/* Semaphore for locking against concurrent checkpoints */
	struct semaphore 	j_checkpoint_sem;

	/*
	 * Journal head: identifies the first unused block in the journal.
	 * [j_state_lock]
	 */
	unsigned long		j_head;

	/*
	 * Journal tail: identifies the oldest still-used block in the journal.
	 * [j_state_lock]
	 */
	unsigned long		j_tail;

	/*
	 * Journal free: how many free blocks are there in the journal?
	 * [j_state_lock]
	 */
	unsigned long		j_free;

	/*
	 * Journal start and end: the block numbers of the first usable block
	 * and one beyond the last usable block in the journal. [j_state_lock]
	 */
	unsigned long		j_first;
	unsigned long		j_last;

	/*
	 * Device, blocksize and starting block offset for the location where we
	 * store the journal.
	 */
	struct block_device	*j_dev;
	int			j_blocksize;
	unsigned int		j_blk_offset;

	/*
	 * Device which holds the client fs.  For internal journal this will be
	 * equal to j_dev.
	 */
	struct block_device	*j_fs_dev;

	/* Total maximum capacity of the journal region on disk. */
	unsigned int		j_maxlen;

	/*
	 * Protects the buffer lists and internal buffer state.
	 */
	spinlock_t		j_list_lock;

	/* Optional inode where we store the journal.  If present, all */
	/* journal block numbers are mapped into this inode via */
	/* bmap(). */
	struct inode		*j_inode;

	/*
	 * Sequence number of the oldest transaction in the log [j_state_lock]
	 */
	tid_t			j_tail_sequence;

	/*
	 * Sequence number of the next transaction to grant [j_state_lock]
	 */
	tid_t			j_transaction_sequence;

	/*
	 * Sequence number of the most recently committed transaction
	 * [j_state_lock].
	 */
	tid_t			j_commit_sequence;

	/*
	 * Sequence number of the most recent transaction wanting commit
	 * [j_state_lock]
	 */
	tid_t			j_commit_request;

	/*
	 * Journal uuid: identifies the object (filesystem, LVM volume etc)
	 * backed by this journal.  This will eventually be replaced by an array
	 * of uuids, allowing us to index multiple devices within a single
	 * journal and to perform atomic updates across them.
	 */
	__u8			j_uuid[16];

	/* Pointer to the current commit thread for this journal */
	struct task_struct	*j_task;

	/*
	 * Maximum number of metadata buffers to allow in a single compound
	 * commit transaction
	 */
	int			j_max_transaction_buffers;

	/*
	 * What is the maximum transaction lifetime before we begin a commit?
	 */
	unsigned long		j_commit_interval;

	/* The timer used to wakeup the commit thread: */
	struct timer_list	*j_commit_timer;

	/*
	 * The revoke table: maintains the list of revoked blocks in the
	 * current transaction.  [j_revoke_lock]
	 */
	spinlock_t		j_revoke_lock;
	struct jbd_revoke_table_s *j_revoke;
	struct jbd_revoke_table_s *j_revoke_table[2];

	/*
	 * array of bhs for journal_commit_transaction
	 */
	struct buffer_head	**j_wbuf;
	int			j_wbufsize;

	/*
	 * An opaque pointer to fs-private information.  ext3 puts its
	 * superblock pointer here
	 */
	void *j_private;
};

/* 
 * Journal flag definitions 
 */
#define JFS_UNMOUNT	0x001	/* Journal thread is being destroyed */
#define JFS_ABORT	0x002	/* Journaling has been aborted for errors. */
#define JFS_ACK_ERR	0x004	/* The errno in the sb has been acked */
#define JFS_FLUSHED	0x008	/* The journal superblock has been flushed */
#define JFS_LOADED	0x010	/* The journal superblock has been loaded */
#define JFS_BARRIER	0x020	/* Use IDE barriers */

/* 
 * Function declarations for the journaling transaction and buffer
 * management
 */

/* Filing buffers */
extern void __journal_temp_unlink_buffer(struct journal_head *jh);
extern void journal_unfile_buffer(journal_t *, struct journal_head *);
extern void __journal_unfile_buffer(struct journal_head *);
extern void __journal_refile_buffer(struct journal_head *);
extern void journal_refile_buffer(journal_t *, struct journal_head *);
extern void __journal_file_buffer(struct journal_head *, transaction_t *, int);
extern void __journal_free_buffer(struct journal_head *bh);
extern void journal_file_buffer(struct journal_head *, transaction_t *, int);
extern void __journal_clean_data_list(transaction_t *transaction);

/* Log buffer allocation */
extern struct journal_head * journal_get_descriptor_buffer(journal_t *);
int journal_next_log_block(journal_t *, unsigned long *);

/* Commit management */
extern void journal_commit_transaction(journal_t *);

/* Checkpoint list management */
int __journal_clean_checkpoint_list(journal_t *journal);
void __journal_remove_checkpoint(struct journal_head *);
void __journal_insert_checkpoint(struct journal_head *, transaction_t *);

/* Buffer IO */
extern int 
journal_write_metadata_buffer(transaction_t	  *transaction,
			      struct journal_head  *jh_in,
			      struct journal_head **jh_out,
			      int		   blocknr);

/* Transaction locking */
extern void		__wait_on_journal (journal_t *);

/*
 * Journal locking.
 *
 * We need to lock the journal during transaction state changes so that nobody
 * ever tries to take a handle on the running transaction while we are in the
 * middle of moving it to the commit phase.  j_state_lock does this.
 *
 * Note that the locking is completely interrupt unsafe.  We never touch
 * journal structures from interrupts.
 */

static inline handle_t *journal_current_handle(void)
{
	return current->journal_info;
}

/* The journaling code user interface:
 *
 * Create and destroy handles
 * Register buffer modifications against the current transaction. 
 */

extern handle_t *journal_start(journal_t *, int nblocks);
extern int	 journal_restart (handle_t *, int nblocks);
extern int	 journal_extend (handle_t *, int nblocks);
extern int	 journal_get_write_access(handle_t *, struct buffer_head *);
extern int	 journal_get_create_access (handle_t *, struct buffer_head *);
extern int	 journal_get_undo_access(handle_t *, struct buffer_head *);
extern int	 journal_dirty_data (handle_t *, struct buffer_head *);
extern int	 journal_dirty_metadata (handle_t *, struct buffer_head *);
extern void	 journal_release_buffer (handle_t *, struct buffer_head *);
extern int	 journal_forget (handle_t *, struct buffer_head *);
extern void	 journal_sync_buffer (struct buffer_head *);
extern int	 journal_invalidatepage(journal_t *,
				struct page *, unsigned long);
extern int	 journal_try_to_free_buffers(journal_t *, struct page *, int);
extern int	 journal_stop(handle_t *);
extern int	 journal_flush (journal_t *);
extern void	 journal_lock_updates (journal_t *);
extern void	 journal_unlock_updates (journal_t *);

extern journal_t * journal_init_dev(struct block_device *bdev,
				struct block_device *fs_dev,
				int start, int len, int bsize);
extern journal_t * journal_init_inode (struct inode *);
extern int	   journal_update_format (journal_t *);
extern int	   journal_check_used_features 
		   (journal_t *, unsigned long, unsigned long, unsigned long);
extern int	   journal_check_available_features 
		   (journal_t *, unsigned long, unsigned long, unsigned long);
extern int	   journal_set_features 
		   (journal_t *, unsigned long, unsigned long, unsigned long);
extern int	   journal_create     (journal_t *);
extern int	   journal_load       (journal_t *journal);
extern void	   journal_destroy    (journal_t *);
extern int	   journal_recover    (journal_t *journal);
extern int	   journal_wipe       (journal_t *, int);
extern int	   journal_skip_recovery	(journal_t *);
extern void	   journal_update_superblock	(journal_t *, int);
extern void	   __journal_abort_hard	(journal_t *);
extern void	   journal_abort      (journal_t *, int);
extern int	   journal_errno      (journal_t *);
extern void	   journal_ack_err    (journal_t *);
extern int	   journal_clear_err  (journal_t *);
extern int	   journal_bmap(journal_t *, unsigned long, unsigned long *);
extern int	   journal_force_commit(journal_t *);

/*
 * journal_head management
 */
struct journal_head *journal_add_journal_head(struct buffer_head *bh);
struct journal_head *journal_grab_journal_head(struct buffer_head *bh);
void journal_remove_journal_head(struct buffer_head *bh);
void journal_put_journal_head(struct journal_head *jh);

/*
 * handle management
 */
extern kmem_cache_t *jbd_handle_cache;

static inline handle_t *jbd_alloc_handle(gfp_t gfp_flags)
{
	return kmem_cache_alloc(jbd_handle_cache, gfp_flags);
}

static inline void jbd_free_handle(handle_t *handle)
{
	kmem_cache_free(jbd_handle_cache, handle);
}

/* Primary revoke support */
#define JOURNAL_REVOKE_DEFAULT_HASH 256
extern int	   journal_init_revoke(journal_t *, int);
extern void	   journal_destroy_revoke_caches(void);
extern int	   journal_init_revoke_caches(void);

extern void	   journal_destroy_revoke(journal_t *);
extern int	   journal_revoke (handle_t *,
				unsigned long, struct buffer_head *);
extern int	   journal_cancel_revoke(handle_t *, struct journal_head *);
extern void	   journal_write_revoke_records(journal_t *, transaction_t *);

/* Recovery revoke support */
extern int	journal_set_revoke(journal_t *, unsigned long, tid_t);
extern int	journal_test_revoke(journal_t *, unsigned long, tid_t);
extern void	journal_clear_revoke(journal_t *);
extern void	journal_brelse_array(struct buffer_head *b[], int n);
extern void	journal_switch_revoke_table(journal_t *journal);

/*
 * The log thread user interface:
 *
 * Request space in the current transaction, and force transaction commit
 * transitions on demand.
 */

int __log_space_left(journal_t *); /* Called with journal locked */
int log_start_commit(journal_t *journal, tid_t tid);
int __log_start_commit(journal_t *journal, tid_t tid);
int journal_start_commit(journal_t *journal, tid_t *tid);
int journal_force_commit_nested(journal_t *journal);
int log_wait_commit(journal_t *journal, tid_t tid);
int log_do_checkpoint(journal_t *journal);

void __log_wait_for_space(journal_t *journal);
extern void	__journal_drop_transaction(journal_t *, transaction_t *);
extern int	cleanup_journal_tail(journal_t *);

/* Debugging code only: */

#define jbd_ENOSYS() \
do {								           \
	printk (KERN_ERR "JBD unimplemented function %s\n", __FUNCTION__); \
	current->state = TASK_UNINTERRUPTIBLE;			           \
	schedule();						           \
} while (1)

/*
 * is_journal_abort
 *
 * Simple test wrapper function to test the JFS_ABORT state flag.  This
 * bit, when set, indicates that we have had a fatal error somewhere,
 * either inside the journaling layer or indicated to us by the client
 * (eg. ext3), and that we and should not commit any further
 * transactions.  
 */

static inline int is_journal_aborted(journal_t *journal)
{
	return journal->j_flags & JFS_ABORT;
}

static inline int is_handle_aborted(handle_t *handle)
{
	if (handle->h_aborted)
		return 1;
	return is_journal_aborted(handle->h_transaction->t_journal);
}

static inline void journal_abort_handle(handle_t *handle)
{
	handle->h_aborted = 1;
}

#endif /* __KERNEL__   */

/* Comparison functions for transaction IDs: perform comparisons using
 * modulo arithmetic so that they work over sequence number wraps. */

static inline int tid_gt(tid_t x, tid_t y)
{
	int difference = (x - y);
	return (difference > 0);
}

static inline int tid_geq(tid_t x, tid_t y)
{
	int difference = (x - y);
	return (difference >= 0);
}

extern int journal_blocks_per_page(struct inode *inode);

/*
 * Return the minimum number of blocks which must be free in the journal
 * before a new transaction may be started.  Must be called under j_state_lock.
 */
static inline int jbd_space_needed(journal_t *journal)
{
	int nblocks = journal->j_max_transaction_buffers;
	if (journal->j_committing_transaction)
		nblocks += journal->j_committing_transaction->
					t_outstanding_credits;
	return nblocks;
}

/*
 * Definitions which augment the buffer_head layer
 */

/* journaling buffer types */
#define BJ_None		0	/* Not journaled */
#define BJ_SyncData	1	/* Normal data: flush before commit */
#define BJ_Metadata	2	/* Normal journaled metadata */
#define BJ_Forget	3	/* Buffer superseded by this transaction */
#define BJ_IO		4	/* Buffer is for temporary IO use */
#define BJ_Shadow	5	/* Buffer contents being shadowed to the log */
#define BJ_LogCtl	6	/* Buffer contains log descriptors */
#define BJ_Reserved	7	/* Buffer is reserved for access by journal */
#define BJ_Locked	8	/* Locked for I/O during commit */
#define BJ_Types	9
 
extern int jbd_blocks_per_page(struct inode *inode);

#ifdef __KERNEL__

#define buffer_trace_init(bh)	do {} while (0)
#define print_buffer_fields(bh)	do {} while (0)
#define print_buffer_trace(bh)	do {} while (0)
#define BUFFER_TRACE(bh, info)	do {} while (0)
#define BUFFER_TRACE2(bh, bh2, info)	do {} while (0)
#define JBUFFER_TRACE(jh, info)	do {} while (0)

#endif	/* __KERNEL__ */

#endif	/* CONFIG_JBD || CONFIG_JBD_MODULE || !__KERNEL__ */

/*
 * Compatibility no-ops which allow the kernel to compile without CONFIG_JBD
 * go here.
 */

#if defined(__KERNEL__) && !(defined(CONFIG_JBD) || defined(CONFIG_JBD_MODULE))

#define J_ASSERT(expr)			do {} while (0)
#define J_ASSERT_BH(bh, expr)		do {} while (0)
#define buffer_jbd(bh)			0
#define journal_buffer_journal_lru(bh)	0

#endif	/* defined(__KERNEL__) && !defined(CONFIG_JBD) */
#endif	/* _LINUX_JBD_H */