summaryrefslogtreecommitdiffstats
path: root/drivers/md/raid5.h
blob: 22bea20eccbdda6a2477ffd0072c0b8b751b6cd8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
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
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _RAID5_H
#define _RAID5_H

#include <linux/raid/xor.h>
#include <linux/dmaengine.h>
#include <linux/local_lock.h>

/*
 *
 * Each stripe contains one buffer per device.  Each buffer can be in
 * one of a number of states stored in "flags".  Changes between
 * these states happen *almost* exclusively under the protection of the
 * STRIPE_ACTIVE flag.  Some very specific changes can happen in bi_end_io, and
 * these are not protected by STRIPE_ACTIVE.
 *
 * The flag bits that are used to represent these states are:
 *   R5_UPTODATE and R5_LOCKED
 *
 * State Empty == !UPTODATE, !LOCK
 *        We have no data, and there is no active request
 * State Want == !UPTODATE, LOCK
 *        A read request is being submitted for this block
 * State Dirty == UPTODATE, LOCK
 *        Some new data is in this buffer, and it is being written out
 * State Clean == UPTODATE, !LOCK
 *        We have valid data which is the same as on disc
 *
 * The possible state transitions are:
 *
 *  Empty -> Want   - on read or write to get old data for  parity calc
 *  Empty -> Dirty  - on compute_parity to satisfy write/sync request.
 *  Empty -> Clean  - on compute_block when computing a block for failed drive
 *  Want  -> Empty  - on failed read
 *  Want  -> Clean  - on successful completion of read request
 *  Dirty -> Clean  - on successful completion of write request
 *  Dirty -> Clean  - on failed write
 *  Clean -> Dirty  - on compute_parity to satisfy write/sync (RECONSTRUCT or RMW)
 *
 * The Want->Empty, Want->Clean, Dirty->Clean, transitions
 * all happen in b_end_io at interrupt time.
 * Each sets the Uptodate bit before releasing the Lock bit.
 * This leaves one multi-stage transition:
 *    Want->Dirty->Clean
 * This is safe because thinking that a Clean buffer is actually dirty
 * will at worst delay some action, and the stripe will be scheduled
 * for attention after the transition is complete.
 *
 * There is one possibility that is not covered by these states.  That
 * is if one drive has failed and there is a spare being rebuilt.  We
 * can't distinguish between a clean block that has been generated
 * from parity calculations, and a clean block that has been
 * successfully written to the spare ( or to parity when resyncing).
 * To distinguish these states we have a stripe bit STRIPE_INSYNC that
 * is set whenever a write is scheduled to the spare, or to the parity
 * disc if there is no spare.  A sync request clears this bit, and
 * when we find it set with no buffers locked, we know the sync is
 * complete.
 *
 * Buffers for the md device that arrive via make_request are attached
 * to the appropriate stripe in one of two lists linked on b_reqnext.
 * One list (bh_read) for read requests, one (bh_write) for write.
 * There should never be more than one buffer on the two lists
 * together, but we are not guaranteed of that so we allow for more.
 *
 * If a buffer is on the read list when the associated cache buffer is
 * Uptodate, the data is copied into the read buffer and it's b_end_io
 * routine is called.  This may happen in the end_request routine only
 * if the buffer has just successfully been read.  end_request should
 * remove the buffers from the list and then set the Uptodate bit on
 * the buffer.  Other threads may do this only if they first check
 * that the Uptodate bit is set.  Once they have checked that they may
 * take buffers off the read queue.
 *
 * When a buffer on the write list is committed for write it is copied
 * into the cache buffer, which is then marked dirty, and moved onto a
 * third list, the written list (bh_written).  Once both the parity
 * block and the cached buffer are successfully written, any buffer on
 * a written list can be returned with b_end_io.
 *
 * The write list and read list both act as fifos.  The read list,
 * write list and written list are protected by the device_lock.
 * The device_lock is only for list manipulations and will only be
 * held for a very short time.  It can be claimed from interrupts.
 *
 *
 * Stripes in the stripe cache can be on one of two lists (or on
 * neither).  The "inactive_list" contains stripes which are not
 * currently being used for any request.  They can freely be reused
 * for another stripe.  The "handle_list" contains stripes that need
 * to be handled in some way.  Both of these are fifo queues.  Each
 * stripe is also (potentially) linked to a hash bucket in the hash
 * table so that it can be found by sector number.  Stripes that are
 * not hashed must be on the inactive_list, and will normally be at
 * the front.  All stripes start life this way.
 *
 * The inactive_list, handle_list and hash bucket lists are all protected by the
 * device_lock.
 *  - stripes have a reference counter. If count==0, they are on a list.
 *  - If a stripe might need handling, STRIPE_HANDLE is set.
 *  - When refcount reaches zero, then if STRIPE_HANDLE it is put on
 *    handle_list else inactive_list
 *
 * This, combined with the fact that STRIPE_HANDLE is only ever
 * cleared while a stripe has a non-zero count means that if the
 * refcount is 0 and STRIPE_HANDLE is set, then it is on the
 * handle_list and if recount is 0 and STRIPE_HANDLE is not set, then
 * the stripe is on inactive_list.
 *
 * The possible transitions are:
 *  activate an unhashed/inactive stripe (get_active_stripe())
 *     lockdev check-hash unlink-stripe cnt++ clean-stripe hash-stripe unlockdev
 *  activate a hashed, possibly active stripe (get_active_stripe())
 *     lockdev check-hash if(!cnt++)unlink-stripe unlockdev
 *  attach a request to an active stripe (add_stripe_bh())
 *     lockdev attach-buffer unlockdev
 *  handle a stripe (handle_stripe())
 *     setSTRIPE_ACTIVE,  clrSTRIPE_HANDLE ...
 *		(lockdev check-buffers unlockdev) ..
 *		change-state ..
 *		record io/ops needed clearSTRIPE_ACTIVE schedule io/ops
 *  release an active stripe (release_stripe())
 *     lockdev if (!--cnt) { if  STRIPE_HANDLE, add to handle_list else add to inactive-list } unlockdev
 *
 * The refcount counts each thread that have activated the stripe,
 * plus raid5d if it is handling it, plus one for each active request
 * on a cached buffer, and plus one if the stripe is undergoing stripe
 * operations.
 *
 * The stripe operations are:
 * -copying data between the stripe cache and user application buffers
 * -computing blocks to save a disk access, or to recover a missing block
 * -updating the parity on a write operation (reconstruct write and
 *  read-modify-write)
 * -checking parity correctness
 * -running i/o to disk
 * These operations are carried out by raid5_run_ops which uses the async_tx
 * api to (optionally) offload operations to dedicated hardware engines.
 * When requesting an operation handle_stripe sets the pending bit for the
 * operation and increments the count.  raid5_run_ops is then run whenever
 * the count is non-zero.
 * There are some critical dependencies between the operations that prevent some
 * from being requested while another is in flight.
 * 1/ Parity check operations destroy the in cache version of the parity block,
 *    so we prevent parity dependent operations like writes and compute_blocks
 *    from starting while a check is in progress.  Some dma engines can perform
 *    the check without damaging the parity block, in these cases the parity
 *    block is re-marked up to date (assuming the check was successful) and is
 *    not re-read from disk.
 * 2/ When a write operation is requested we immediately lock the affected
 *    blocks, and mark them as not up to date.  This causes new read requests
 *    to be held off, as well as parity checks and compute block operations.
 * 3/ Once a compute block operation has been requested handle_stripe treats
 *    that block as if it is up to date.  raid5_run_ops guaruntees that any
 *    operation that is dependent on the compute block result is initiated after
 *    the compute block completes.
 */

/*
 * Operations state - intermediate states that are visible outside of
 *   STRIPE_ACTIVE.
 * In general _idle indicates nothing is running, _run indicates a data
 * processing operation is active, and _result means the data processing result
 * is stable and can be acted upon.  For simple operations like biofill and
 * compute that only have an _idle and _run state they are indicated with
 * sh->state flags (STRIPE_BIOFILL_RUN and STRIPE_COMPUTE_RUN)
 */
/**
 * enum check_states - handles syncing / repairing a stripe
 * @check_state_idle - check operations are quiesced
 * @check_state_run - check operation is running
 * @check_state_result - set outside lock when check result is valid
 * @check_state_compute_run - check failed and we are repairing
 * @check_state_compute_result - set outside lock when compute result is valid
 */
enum check_states {
	check_state_idle = 0,
	check_state_run, /* xor parity check */
	check_state_run_q, /* q-parity check */
	check_state_run_pq, /* pq dual parity check */
	check_state_check_result,
	check_state_compute_run, /* parity repair */
	check_state_compute_result,
};

/**
 * enum reconstruct_states - handles writing or expanding a stripe
 */
enum reconstruct_states {
	reconstruct_state_idle = 0,
	reconstruct_state_prexor_drain_run,	/* prexor-write */
	reconstruct_state_drain_run,		/* write */
	reconstruct_state_run,			/* expand */
	reconstruct_state_prexor_drain_result,
	reconstruct_state_drain_result,
	reconstruct_state_result,
};

#define DEFAULT_STRIPE_SIZE	4096
struct stripe_head {
	struct hlist_node	hash;
	struct list_head	lru;	      /* inactive_list or handle_list */
	struct llist_node	release_list;
	struct r5conf		*raid_conf;
	short			generation;	/* increments with every
						 * reshape */
	sector_t		sector;		/* sector of this row */
	short			pd_idx;		/* parity disk index */
	short			qd_idx;		/* 'Q' disk index for raid6 */
	short			ddf_layout;/* use DDF ordering to calculate Q */
	short			hash_lock_index;
	unsigned long		state;		/* state flags */
	atomic_t		count;	      /* nr of active thread/requests */
	int			bm_seq;	/* sequence number for bitmap flushes */
	int			disks;		/* disks in stripe */
	int			overwrite_disks; /* total overwrite disks in stripe,
						  * this is only checked when stripe
						  * has STRIPE_BATCH_READY
						  */
	enum check_states	check_state;
	enum reconstruct_states reconstruct_state;
	spinlock_t		stripe_lock;
	int			cpu;
	struct r5worker_group	*group;

	struct stripe_head	*batch_head; /* protected by stripe lock */
	spinlock_t		batch_lock; /* only header's lock is useful */
	struct list_head	batch_list; /* protected by head's batch lock*/

	union {
		struct r5l_io_unit	*log_io;
		struct ppl_io_unit	*ppl_io;
	};

	struct list_head	log_list;
	sector_t		log_start; /* first meta block on the journal */
	struct list_head	r5c; /* for r5c_cache->stripe_in_journal */

	struct page		*ppl_page; /* partial parity of this stripe */
	/**
	 * struct stripe_operations
	 * @target - STRIPE_OP_COMPUTE_BLK target
	 * @target2 - 2nd compute target in the raid6 case
	 * @zero_sum_result - P and Q verification flags
	 * @request - async service request flags for raid_run_ops
	 */
	struct stripe_operations {
		int 		     target, target2;
		enum sum_check_flags zero_sum_result;
	} ops;

#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
	/* These pages will be used by bios in dev[i] */
	struct page	**pages;
	int	nr_pages;	/* page array size */
	int	stripes_per_page;
#endif
	struct r5dev {
		/* rreq and rvec are used for the replacement device when
		 * writing data to both devices.
		 */
		struct bio	req, rreq;
		struct bio_vec	vec, rvec;
		struct page	*page, *orig_page;
		unsigned int    offset;     /* offset of the page */
		struct bio	*toread, *read, *towrite, *written;
		sector_t	sector;			/* sector of this page */
		unsigned long	flags;
		u32		log_checksum;
		unsigned short	write_hint;
	} dev[]; /* allocated depending of RAID geometry ("disks" member) */
};

/* stripe_head_state - collects and tracks the dynamic state of a stripe_head
 *     for handle_stripe.
 */
struct stripe_head_state {
	/* 'syncing' means that we need to read all devices, either
	 * to check/correct parity, or to reconstruct a missing device.
	 * 'replacing' means we are replacing one or more drives and
	 * the source is valid at this point so we don't need to
	 * read all devices, just the replacement targets.
	 */
	int syncing, expanding, expanded, replacing;
	int locked, uptodate, to_read, to_write, failed, written;
	int to_fill, compute, req_compute, non_overwrite;
	int injournal, just_cached;
	int failed_num[2];
	int p_failed, q_failed;
	int dec_preread_active;
	unsigned long ops_request;

	struct md_rdev *blocked_rdev;
	int handle_bad_blocks;
	int log_failed;
	int waiting_extra_page;
};

/* Flags for struct r5dev.flags */
enum r5dev_flags {
	R5_UPTODATE,	/* page contains current data */
	R5_LOCKED,	/* IO has been submitted on "req" */
	R5_DOUBLE_LOCKED,/* Cannot clear R5_LOCKED until 2 writes complete */
	R5_OVERWRITE,	/* towrite covers whole page */
/* and some that are internal to handle_stripe */
	R5_Insync,	/* rdev && rdev->in_sync at start */
	R5_Wantread,	/* want to schedule a read */
	R5_Wantwrite,
	R5_Overlap,	/* There is a pending overlapping request
			 * on this block */
	R5_ReadNoMerge, /* prevent bio from merging in block-layer */
	R5_ReadError,	/* seen a read error here recently */
	R5_ReWrite,	/* have tried to over-write the readerror */

	R5_Expanded,	/* This block now has post-expand data */
	R5_Wantcompute,	/* compute_block in progress treat as
			 * uptodate
			 */
	R5_Wantfill,	/* dev->toread contains a bio that needs
			 * filling
			 */
	R5_Wantdrain,	/* dev->towrite needs to be drained */
	R5_WantFUA,	/* Write should be FUA */
	R5_SyncIO,	/* The IO is sync */
	R5_WriteError,	/* got a write error - need to record it */
	R5_MadeGood,	/* A bad block has been fixed by writing to it */
	R5_ReadRepl,	/* Will/did read from replacement rather than orig */
	R5_MadeGoodRepl,/* A bad block on the replacement device has been
			 * fixed by writing to it */
	R5_NeedReplace,	/* This device has a replacement which is not
			 * up-to-date at this stripe. */
	R5_WantReplace, /* We need to update the replacement, we have read
			 * data in, and now is a good time to write it out.
			 */
	R5_Discard,	/* Discard the stripe */
	R5_SkipCopy,	/* Don't copy data from bio to stripe cache */
	R5_InJournal,	/* data being written is in the journal device.
			 * if R5_InJournal is set for parity pd_idx, all the
			 * data and parity being written are in the journal
			 * device
			 */
	R5_OrigPageUPTDODATE,	/* with write back cache, we read old data into
				 * dev->orig_page for prexor. When this flag is
				 * set, orig_page contains latest data in the
				 * raid disk.
				 */
};

/*
 * Stripe state
 */
enum {
	STRIPE_ACTIVE,
	STRIPE_HANDLE,
	STRIPE_SYNC_REQUESTED,
	STRIPE_SYNCING,
	STRIPE_INSYNC,
	STRIPE_REPLACED,
	STRIPE_PREREAD_ACTIVE,
	STRIPE_DELAYED,
	STRIPE_DEGRADED,
	STRIPE_BIT_DELAY,
	STRIPE_EXPANDING,
	STRIPE_EXPAND_SOURCE,
	STRIPE_EXPAND_READY,
	STRIPE_IO_STARTED,	/* do not count towards 'bypass_count' */
	STRIPE_FULL_WRITE,	/* all blocks are set to be overwritten */
	STRIPE_BIOFILL_RUN,
	STRIPE_COMPUTE_RUN,
	STRIPE_ON_UNPLUG_LIST,
	STRIPE_DISCARD,
	STRIPE_ON_RELEASE_LIST,
	STRIPE_BATCH_READY,
	STRIPE_BATCH_ERR,
	STRIPE_BITMAP_PENDING,	/* Being added to bitmap, don't add
				 * to batch yet.
				 */
	STRIPE_LOG_TRAPPED,	/* trapped into log (see raid5-cache.c)
				 * this bit is used in two scenarios:
				 *
				 * 1. write-out phase
				 *  set in first entry of r5l_write_stripe
				 *  clear in second entry of r5l_write_stripe
				 *  used to bypass logic in handle_stripe
				 *
				 * 2. caching phase
				 *  set in r5c_try_caching_write()
				 *  clear when journal write is done
				 *  used to initiate r5c_cache_data()
				 *  also used to bypass logic in handle_stripe
				 */
	STRIPE_R5C_CACHING,	/* the stripe is in caching phase
				 * see more detail in the raid5-cache.c
				 */
	STRIPE_R5C_PARTIAL_STRIPE,	/* in r5c cache (to-be/being handled or
					 * in conf->r5c_partial_stripe_list)
					 */
	STRIPE_R5C_FULL_STRIPE,	/* in r5c cache (to-be/being handled or
				 * in conf->r5c_full_stripe_list)
				 */
	STRIPE_R5C_PREFLUSH,	/* need to flush journal device */
};

#define STRIPE_EXPAND_SYNC_FLAGS \
	((1 << STRIPE_EXPAND_SOURCE) |\
	(1 << STRIPE_EXPAND_READY) |\
	(1 << STRIPE_EXPANDING) |\
	(1 << STRIPE_SYNC_REQUESTED))
/*
 * Operation request flags
 */
enum {
	STRIPE_OP_BIOFILL,
	STRIPE_OP_COMPUTE_BLK,
	STRIPE_OP_PREXOR,
	STRIPE_OP_BIODRAIN,
	STRIPE_OP_RECONSTRUCT,
	STRIPE_OP_CHECK,
	STRIPE_OP_PARTIAL_PARITY,
};

/*
 * RAID parity calculation preferences
 */
enum {
	PARITY_DISABLE_RMW = 0,
	PARITY_ENABLE_RMW,
	PARITY_PREFER_RMW,
};

/*
 * Pages requested from set_syndrome_sources()
 */
enum {
	SYNDROME_SRC_ALL,
	SYNDROME_SRC_WANT_DRAIN,
	SYNDROME_SRC_WRITTEN,
};
/*
 * Plugging:
 *
 * To improve write throughput, we need to delay the handling of some
 * stripes until there has been a chance that several write requests
 * for the one stripe have all been collected.
 * In particular, any write request that would require pre-reading
 * is put on a "delayed" queue until there are no stripes currently
 * in a pre-read phase.  Further, if the "delayed" queue is empty when
 * a stripe is put on it then we "plug" the queue and do not process it
 * until an unplug call is made. (the unplug_io_fn() is called).
 *
 * When preread is initiated on a stripe, we set PREREAD_ACTIVE and add
 * it to the count of prereading stripes.
 * When write is initiated, or the stripe refcnt == 0 (just in case) we
 * clear the PREREAD_ACTIVE flag and decrement the count
 * Whenever the 'handle' queue is empty and the device is not plugged, we
 * move any strips from delayed to handle and clear the DELAYED flag and set
 * PREREAD_ACTIVE.
 * In stripe_handle, if we find pre-reading is necessary, we do it if
 * PREREAD_ACTIVE is set, else we set DELAYED which will send it to the delayed queue.
 * HANDLE gets cleared if stripe_handle leaves nothing locked.
 */

/* Note: disk_info.rdev can be set to NULL asynchronously by raid5_remove_disk.
 * There are three safe ways to access disk_info.rdev.
 * 1/ when holding mddev->reconfig_mutex
 * 2/ when resync/recovery/reshape is known to be happening - i.e. in code that
 *    is called as part of performing resync/recovery/reshape.
 * 3/ while holding rcu_read_lock(), use rcu_dereference to get the pointer
 *    and if it is non-NULL, increment rdev->nr_pending before dropping the RCU
 *    lock.
 * When .rdev is set to NULL, the nr_pending count checked again and if
 * it has been incremented, the pointer is put back in .rdev.
 */

struct disk_info {
	struct md_rdev	__rcu *rdev;
	struct md_rdev  __rcu *replacement;
	struct page	*extra_page; /* extra page to use in prexor */
};

/*
 * Stripe cache
 */

#define NR_STRIPES		256

#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
#define STRIPE_SIZE		PAGE_SIZE
#define STRIPE_SHIFT		(PAGE_SHIFT - 9)
#define STRIPE_SECTORS		(STRIPE_SIZE>>9)
#endif

#define	IO_THRESHOLD		1
#define BYPASS_THRESHOLD	1
#define NR_HASH			(PAGE_SIZE / sizeof(struct hlist_head))
#define HASH_MASK		(NR_HASH - 1)
#define MAX_STRIPE_BATCH	8

/* NOTE NR_STRIPE_HASH_LOCKS must remain below 64.
 * This is because we sometimes take all the spinlocks
 * and creating that much locking depth can cause
 * problems.
 */
#define NR_STRIPE_HASH_LOCKS 8
#define STRIPE_HASH_LOCKS_MASK (NR_STRIPE_HASH_LOCKS - 1)

struct r5worker {
	struct work_struct work;
	struct r5worker_group *group;
	struct list_head temp_inactive_list[NR_STRIPE_HASH_LOCKS];
	bool working;
};

struct r5worker_group {
	struct list_head handle_list;
	struct list_head loprio_list;
	struct r5conf *conf;
	struct r5worker *workers;
	int stripes_cnt;
};

/*
 * r5c journal modes of the array: write-back or write-through.
 * write-through mode has identical behavior as existing log only
 * implementation.
 */
enum r5c_journal_mode {
	R5C_JOURNAL_MODE_WRITE_THROUGH = 0,
	R5C_JOURNAL_MODE_WRITE_BACK = 1,
};

enum r5_cache_state {
	R5_INACTIVE_BLOCKED,	/* release of inactive stripes blocked,
				 * waiting for 25% to be free
				 */
	R5_ALLOC_MORE,		/* It might help to allocate another
				 * stripe.
				 */
	R5_DID_ALLOC,		/* A stripe was allocated, don't allocate
				 * more until at least one has been
				 * released.  This avoids flooding
				 * the cache.
				 */
	R5C_LOG_TIGHT,		/* log device space tight, need to
				 * prioritize stripes at last_checkpoint
				 */
	R5C_LOG_CRITICAL,	/* log device is running out of space,
				 * only process stripes that are already
				 * occupying the log
				 */
	R5C_EXTRA_PAGE_IN_USE,	/* a stripe is using disk_info.extra_page
				 * for prexor
				 */
};

#define PENDING_IO_MAX 512
#define PENDING_IO_ONE_FLUSH 128
struct r5pending_data {
	struct list_head sibling;
	sector_t sector; /* stripe sector */
	struct bio_list bios;
};

struct raid5_percpu {
	struct page	*spare_page; /* Used when checking P/Q in raid6 */
	void		*scribble;  /* space for constructing buffer
				     * lists and performing address
				     * conversions
				     */
	int             scribble_obj_size;
	local_lock_t    lock;
};

struct r5conf {
	struct hlist_head	*stripe_hashtbl;
	/* only protect corresponding hash list and inactive_list */
	spinlock_t		hash_locks[NR_STRIPE_HASH_LOCKS];
	struct mddev		*mddev;
	int			chunk_sectors;
	int			level, algorithm, rmw_level;
	int			max_degraded;
	int			raid_disks;
	int			max_nr_stripes;
	int			min_nr_stripes;
#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
	unsigned long	stripe_size;
	unsigned int	stripe_shift;
	unsigned long	stripe_sectors;
#endif

	/* reshape_progress is the leading edge of a 'reshape'
	 * It has value MaxSector when no reshape is happening
	 * If delta_disks < 0, it is the last sector we started work on,
	 * else is it the next sector to work on.
	 */
	sector_t		reshape_progress;
	/* reshape_safe is the trailing edge of a reshape.  We know that
	 * before (or after) this address, all reshape has completed.
	 */
	sector_t		reshape_safe;
	int			previous_raid_disks;
	int			prev_chunk_sectors;
	int			prev_algo;
	short			generation; /* increments with every reshape */
	seqcount_spinlock_t	gen_lock;	/* lock against generation changes */
	unsigned long		reshape_checkpoint; /* Time we last updated
						     * metadata */
	long long		min_offset_diff; /* minimum difference between
						  * data_offset and
						  * new_data_offset across all
						  * devices.  May be negative,
						  * but is closest to zero.
						  */

	struct list_head	handle_list; /* stripes needing handling */
	struct list_head	loprio_list; /* low priority stripes */
	struct list_head	hold_list; /* preread ready stripes */
	struct list_head	delayed_list; /* stripes that have plugged requests */
	struct list_head	bitmap_list; /* stripes delaying awaiting bitmap update */
	struct bio		*retry_read_aligned; /* currently retrying aligned bios   */
	unsigned int		retry_read_offset; /* sector offset into retry_read_aligned */
	struct bio		*retry_read_aligned_list; /* aligned bios retry list  */
	atomic_t		preread_active_stripes; /* stripes with scheduled io */
	atomic_t		active_aligned_reads;
	atomic_t		pending_full_writes; /* full write backlog */
	int			bypass_count; /* bypassed prereads */
	int			bypass_threshold; /* preread nice */
	int			skip_copy; /* Don't copy data from bio to stripe cache */
	struct list_head	*last_hold; /* detect hold_list promotions */

	atomic_t		reshape_stripes; /* stripes with pending writes for reshape */
	/* unfortunately we need two cache names as we temporarily have
	 * two caches.
	 */
	int			active_name;
	char			cache_name[2][32];
	struct kmem_cache	*slab_cache; /* for allocating stripes */
	struct mutex		cache_size_mutex; /* Protect changes to cache size */

	int			seq_flush, seq_write;
	int			quiesce;

	int			fullsync;  /* set to 1 if a full sync is needed,
					    * (fresh device added).
					    * Cleared when a sync completes.
					    */
	int			recovery_disabled;
	/* per cpu variables */
	struct raid5_percpu __percpu *percpu;
	int scribble_disks;
	int scribble_sectors;
	struct hlist_node node;

	/*
	 * Free stripes pool
	 */
	atomic_t		active_stripes;
	struct list_head	inactive_list[NR_STRIPE_HASH_LOCKS];

	atomic_t		r5c_cached_full_stripes;
	struct list_head	r5c_full_stripe_list;
	atomic_t		r5c_cached_partial_stripes;
	struct list_head	r5c_partial_stripe_list;
	atomic_t		r5c_flushing_full_stripes;
	atomic_t		r5c_flushing_partial_stripes;

	atomic_t		empty_inactive_list_nr;
	struct llist_head	released_stripes;
	wait_queue_head_t	wait_for_quiescent;
	wait_queue_head_t	wait_for_stripe;
	wait_queue_head_t	wait_for_overlap;
	unsigned long		cache_state;
	struct shrinker		*shrinker;
	int			pool_size; /* number of disks in stripeheads in pool */
	spinlock_t		device_lock;
	struct disk_info	*disks;
	struct bio_set		bio_split;

	/* When taking over an array from a different personality, we store
	 * the new thread here until we fully activate the array.
	 */
	struct md_thread __rcu	*thread;
	struct list_head	temp_inactive_list[NR_STRIPE_HASH_LOCKS];
	struct r5worker_group	*worker_groups;
	int			group_cnt;
	int			worker_cnt_per_group;
	struct r5l_log		*log;
	void			*log_private;

	spinlock_t		pending_bios_lock;
	bool			batch_bio_dispatch;
	struct r5pending_data	*pending_data;
	struct list_head	free_list;
	struct list_head	pending_list;
	int			pending_data_cnt;
	struct r5pending_data	*next_pending_data;
};

#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
#define RAID5_STRIPE_SIZE(conf)	STRIPE_SIZE
#define RAID5_STRIPE_SHIFT(conf)	STRIPE_SHIFT
#define RAID5_STRIPE_SECTORS(conf)	STRIPE_SECTORS
#else
#define RAID5_STRIPE_SIZE(conf)	((conf)->stripe_size)
#define RAID5_STRIPE_SHIFT(conf)	((conf)->stripe_shift)
#define RAID5_STRIPE_SECTORS(conf)	((conf)->stripe_sectors)
#endif

/* bio's attached to a stripe+device for I/O are linked together in bi_sector
 * order without overlap.  There may be several bio's per stripe+device, and
 * a bio could span several devices.
 * When walking this list for a particular stripe+device, we must never proceed
 * beyond a bio that extends past this device, as the next bio might no longer
 * be valid.
 * This function is used to determine the 'next' bio in the list, given the
 * sector of the current stripe+device
 */
static inline struct bio *r5_next_bio(struct r5conf *conf, struct bio *bio, sector_t sector)
{
	if (bio_end_sector(bio) < sector + RAID5_STRIPE_SECTORS(conf))
		return bio->bi_next;
	else
		return NULL;
}

/*
 * Our supported algorithms
 */
#define ALGORITHM_LEFT_ASYMMETRIC	0 /* Rotating Parity N with Data Restart */
#define ALGORITHM_RIGHT_ASYMMETRIC	1 /* Rotating Parity 0 with Data Restart */
#define ALGORITHM_LEFT_SYMMETRIC	2 /* Rotating Parity N with Data Continuation */
#define ALGORITHM_RIGHT_SYMMETRIC	3 /* Rotating Parity 0 with Data Continuation */

/* Define non-rotating (raid4) algorithms.  These allow
 * conversion of raid4 to raid5.
 */
#define ALGORITHM_PARITY_0		4 /* P or P,Q are initial devices */
#define ALGORITHM_PARITY_N		5 /* P or P,Q are final devices. */

/* DDF RAID6 layouts differ from md/raid6 layouts in two ways.
 * Firstly, the exact positioning of the parity block is slightly
 * different between the 'LEFT_*' modes of md and the "_N_*" modes
 * of DDF.
 * Secondly, or order of datablocks over which the Q syndrome is computed
 * is different.
 * Consequently we have different layouts for DDF/raid6 than md/raid6.
 * These layouts are from the DDFv1.2 spec.
 * Interestingly DDFv1.2-Errata-A does not specify N_CONTINUE but
 * leaves RLQ=3 as 'Vendor Specific'
 */

#define ALGORITHM_ROTATING_ZERO_RESTART	8 /* DDF PRL=6 RLQ=1 */
#define ALGORITHM_ROTATING_N_RESTART	9 /* DDF PRL=6 RLQ=2 */
#define ALGORITHM_ROTATING_N_CONTINUE	10 /*DDF PRL=6 RLQ=3 */

/* For every RAID5 algorithm we define a RAID6 algorithm
 * with exactly the same layout for data and parity, and
 * with the Q block always on the last device (N-1).
 * This allows trivial conversion from RAID5 to RAID6
 */
#define ALGORITHM_LEFT_ASYMMETRIC_6	16
#define ALGORITHM_RIGHT_ASYMMETRIC_6	17
#define ALGORITHM_LEFT_SYMMETRIC_6	18
#define ALGORITHM_RIGHT_SYMMETRIC_6	19
#define ALGORITHM_PARITY_0_6		20
#define ALGORITHM_PARITY_N_6		ALGORITHM_PARITY_N

static inline int algorithm_valid_raid5(int layout)
{
	return (layout >= 0) &&
		(layout <= 5);
}
static inline int algorithm_valid_raid6(int layout)
{
	return (layout >= 0 && layout <= 5)
		||
		(layout >= 8 && layout <= 10)
		||
		(layout >= 16 && layout <= 20);
}

static inline int algorithm_is_DDF(int layout)
{
	return layout >= 8 && layout <= 10;
}

#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
/*
 * Return offset of the corresponding page for r5dev.
 */
static inline int raid5_get_page_offset(struct stripe_head *sh, int disk_idx)
{
	return (disk_idx % sh->stripes_per_page) * RAID5_STRIPE_SIZE(sh->raid_conf);
}

/*
 * Return corresponding page address for r5dev.
 */
static inline struct page *
raid5_get_dev_page(struct stripe_head *sh, int disk_idx)
{
	return sh->pages[disk_idx / sh->stripes_per_page];
}
#endif

void md_raid5_kick_device(struct r5conf *conf);
int raid5_set_cache_size(struct mddev *mddev, int size);
sector_t raid5_compute_blocknr(struct stripe_head *sh, int i, int previous);
void raid5_release_stripe(struct stripe_head *sh);
sector_t raid5_compute_sector(struct r5conf *conf, sector_t r_sector,
		int previous, int *dd_idx, struct stripe_head *sh);

struct stripe_request_ctx;
/* get stripe from previous generation (when reshaping) */
#define R5_GAS_PREVIOUS		(1 << 0)
/* do not block waiting for a free stripe */
#define R5_GAS_NOBLOCK		(1 << 1)
/* do not block waiting for quiesce to be released */
#define R5_GAS_NOQUIESCE	(1 << 2)
struct stripe_head *raid5_get_active_stripe(struct r5conf *conf,
		struct stripe_request_ctx *ctx, sector_t sector,
		unsigned int flags);

int raid5_calc_degraded(struct r5conf *conf);
int r5c_journal_mode_set(struct mddev *mddev, int journal_mode);
#endif