1#ifndef _RAID5_H
  2#define _RAID5_H
  3
  4#include <linux/raid/xor.h>
  5#include <linux/dmaengine.h>
  6
  7/*
  8 *
  9 * Each stripe contains one buffer per device.  Each buffer can be in
 10 * one of a number of states stored in "flags".  Changes between
 11 * these states happen *almost* exclusively under the protection of the
 12 * STRIPE_ACTIVE flag.  Some very specific changes can happen in bi_end_io, and
 13 * these are not protected by STRIPE_ACTIVE.
 14 *
 15 * The flag bits that are used to represent these states are:
 16 *   R5_UPTODATE and R5_LOCKED
 17 *
 18 * State Empty == !UPTODATE, !LOCK
 19 *        We have no data, and there is no active request
 20 * State Want == !UPTODATE, LOCK
 21 *        A read request is being submitted for this block
 22 * State Dirty == UPTODATE, LOCK
 23 *        Some new data is in this buffer, and it is being written out
 24 * State Clean == UPTODATE, !LOCK
 25 *        We have valid data which is the same as on disc
 26 *
 27 * The possible state transitions are:
 28 *
 29 *  Empty -> Want   - on read or write to get old data for  parity calc
 30 *  Empty -> Dirty  - on compute_parity to satisfy write/sync request.
 31 *  Empty -> Clean  - on compute_block when computing a block for failed drive
 32 *  Want  -> Empty  - on failed read
 33 *  Want  -> Clean  - on successful completion of read request
 34 *  Dirty -> Clean  - on successful completion of write request
 35 *  Dirty -> Clean  - on failed write
 36 *  Clean -> Dirty  - on compute_parity to satisfy write/sync (RECONSTRUCT or RMW)
 37 *
 38 * The Want->Empty, Want->Clean, Dirty->Clean, transitions
 39 * all happen in b_end_io at interrupt time.
 40 * Each sets the Uptodate bit before releasing the Lock bit.
 41 * This leaves one multi-stage transition:
 42 *    Want->Dirty->Clean
 43 * This is safe because thinking that a Clean buffer is actually dirty
 44 * will at worst delay some action, and the stripe will be scheduled
 45 * for attention after the transition is complete.
 46 *
 47 * There is one possibility that is not covered by these states.  That
 48 * is if one drive has failed and there is a spare being rebuilt.  We
 49 * can't distinguish between a clean block that has been generated
 50 * from parity calculations, and a clean block that has been
 51 * successfully written to the spare ( or to parity when resyncing).
 52 * To distingush these states we have a stripe bit STRIPE_INSYNC that
 53 * is set whenever a write is scheduled to the spare, or to the parity
 54 * disc if there is no spare.  A sync request clears this bit, and
 55 * when we find it set with no buffers locked, we know the sync is
 56 * complete.
 57 *
 58 * Buffers for the md device that arrive via make_request are attached
 59 * to the appropriate stripe in one of two lists linked on b_reqnext.
 60 * One list (bh_read) for read requests, one (bh_write) for write.
 61 * There should never be more than one buffer on the two lists
 62 * together, but we are not guaranteed of that so we allow for more.
 63 *
 64 * If a buffer is on the read list when the associated cache buffer is
 65 * Uptodate, the data is copied into the read buffer and it's b_end_io
 66 * routine is called.  This may happen in the end_request routine only
 67 * if the buffer has just successfully been read.  end_request should
 68 * remove the buffers from the list and then set the Uptodate bit on
 69 * the buffer.  Other threads may do this only if they first check
 70 * that the Uptodate bit is set.  Once they have checked that they may
 71 * take buffers off the read queue.
 72 *
 73 * When a buffer on the write list is committed for write it is copied
 74 * into the cache buffer, which is then marked dirty, and moved onto a
 75 * third list, the written list (bh_written).  Once both the parity
 76 * block and the cached buffer are successfully written, any buffer on
 77 * a written list can be returned with b_end_io.
 78 *
 79 * The write list and read list both act as fifos.  The read list,
 80 * write list and written list are protected by the device_lock.
 81 * The device_lock is only for list manipulations and will only be
 82 * held for a very short time.  It can be claimed from interrupts.
 83 *
 84 *
 85 * Stripes in the stripe cache can be on one of two lists (or on
 86 * neither).  The "inactive_list" contains stripes which are not
 87 * currently being used for any request.  They can freely be reused
 88 * for another stripe.  The "handle_list" contains stripes that need
 89 * to be handled in some way.  Both of these are fifo queues.  Each
 90 * stripe is also (potentially) linked to a hash bucket in the hash
 91 * table so that it can be found by sector number.  Stripes that are
 92 * not hashed must be on the inactive_list, and will normally be at
 93 * the front.  All stripes start life this way.
 94 *
 95 * The inactive_list, handle_list and hash bucket lists are all protected by the
 96 * device_lock.
 97 *  - stripes have a reference counter. If count==0, they are on a list.
 98 *  - If a stripe might need handling, STRIPE_HANDLE is set.
 99 *  - When refcount reaches zero, then if STRIPE_HANDLE it is put on
100 *    handle_list else inactive_list
101 *
102 * This, combined with the fact that STRIPE_HANDLE is only ever
103 * cleared while a stripe has a non-zero count means that if the
104 * refcount is 0 and STRIPE_HANDLE is set, then it is on the
105 * handle_list and if recount is 0 and STRIPE_HANDLE is not set, then
106 * the stripe is on inactive_list.
107 *
108 * The possible transitions are:
109 *  activate an unhashed/inactive stripe (get_active_stripe())
110 *     lockdev check-hash unlink-stripe cnt++ clean-stripe hash-stripe unlockdev
111 *  activate a hashed, possibly active stripe (get_active_stripe())
112 *     lockdev check-hash if(!cnt++)unlink-stripe unlockdev
113 *  attach a request to an active stripe (add_stripe_bh())
114 *     lockdev attach-buffer unlockdev
115 *  handle a stripe (handle_stripe())
116 *     setSTRIPE_ACTIVE,  clrSTRIPE_HANDLE ...
117 *		(lockdev check-buffers unlockdev) ..
118 *		change-state ..
119 *		record io/ops needed clearSTRIPE_ACTIVE schedule io/ops
120 *  release an active stripe (release_stripe())
121 *     lockdev if (!--cnt) { if  STRIPE_HANDLE, add to handle_list else add to inactive-list } unlockdev
122 *
123 * The refcount counts each thread that have activated the stripe,
124 * plus raid5d if it is handling it, plus one for each active request
125 * on a cached buffer, and plus one if the stripe is undergoing stripe
126 * operations.
127 *
128 * The stripe operations are:
129 * -copying data between the stripe cache and user application buffers
130 * -computing blocks to save a disk access, or to recover a missing block
131 * -updating the parity on a write operation (reconstruct write and
132 *  read-modify-write)
133 * -checking parity correctness
134 * -running i/o to disk
135 * These operations are carried out by raid5_run_ops which uses the async_tx
136 * api to (optionally) offload operations to dedicated hardware engines.
137 * When requesting an operation handle_stripe sets the pending bit for the
138 * operation and increments the count.  raid5_run_ops is then run whenever
139 * the count is non-zero.
140 * There are some critical dependencies between the operations that prevent some
141 * from being requested while another is in flight.
142 * 1/ Parity check operations destroy the in cache version of the parity block,
143 *    so we prevent parity dependent operations like writes and compute_blocks
144 *    from starting while a check is in progress.  Some dma engines can perform
145 *    the check without damaging the parity block, in these cases the parity
146 *    block is re-marked up to date (assuming the check was successful) and is
147 *    not re-read from disk.
148 * 2/ When a write operation is requested we immediately lock the affected
149 *    blocks, and mark them as not up to date.  This causes new read requests
150 *    to be held off, as well as parity checks and compute block operations.
151 * 3/ Once a compute block operation has been requested handle_stripe treats
152 *    that block as if it is up to date.  raid5_run_ops guaruntees that any
153 *    operation that is dependent on the compute block result is initiated after
154 *    the compute block completes.
155 */
156
157/*
158 * Operations state - intermediate states that are visible outside of 
159 *   STRIPE_ACTIVE.
160 * In general _idle indicates nothing is running, _run indicates a data
161 * processing operation is active, and _result means the data processing result
162 * is stable and can be acted upon.  For simple operations like biofill and
163 * compute that only have an _idle and _run state they are indicated with
164 * sh->state flags (STRIPE_BIOFILL_RUN and STRIPE_COMPUTE_RUN)
165 */
166/**
167 * enum check_states - handles syncing / repairing a stripe
168 * @check_state_idle - check operations are quiesced
169 * @check_state_run - check operation is running
170 * @check_state_result - set outside lock when check result is valid
171 * @check_state_compute_run - check failed and we are repairing
172 * @check_state_compute_result - set outside lock when compute result is valid
173 */
174enum check_states {
175	check_state_idle = 0,
176	check_state_run, /* xor parity check */
177	check_state_run_q, /* q-parity check */
178	check_state_run_pq, /* pq dual parity check */
179	check_state_check_result,
180	check_state_compute_run, /* parity repair */
181	check_state_compute_result,
182};
183
184/**
185 * enum reconstruct_states - handles writing or expanding a stripe
186 */
187enum reconstruct_states {
188	reconstruct_state_idle = 0,
189	reconstruct_state_prexor_drain_run,	/* prexor-write */
190	reconstruct_state_drain_run,		/* write */
191	reconstruct_state_run,			/* expand */
192	reconstruct_state_prexor_drain_result,
193	reconstruct_state_drain_result,
194	reconstruct_state_result,
195};
196
197struct stripe_head {
198	struct hlist_node	hash;
199	struct list_head	lru;	      /* inactive_list or handle_list */
200	struct r5conf		*raid_conf;
201	short			generation;	/* increments with every
202						 * reshape */
203	sector_t		sector;		/* sector of this row */
204	short			pd_idx;		/* parity disk index */
205	short			qd_idx;		/* 'Q' disk index for raid6 */
206	short			ddf_layout;/* use DDF ordering to calculate Q */
207	unsigned long		state;		/* state flags */
208	atomic_t		count;	      /* nr of active thread/requests */
209	int			bm_seq;	/* sequence number for bitmap flushes */
210	int			disks;		/* disks in stripe */
211	enum check_states	check_state;
212	enum reconstruct_states reconstruct_state;
213	/**
214	 * struct stripe_operations
215	 * @target - STRIPE_OP_COMPUTE_BLK target
216	 * @target2 - 2nd compute target in the raid6 case
217	 * @zero_sum_result - P and Q verification flags
218	 * @request - async service request flags for raid_run_ops
219	 */
220	struct stripe_operations {
221		int 		     target, target2;
222		enum sum_check_flags zero_sum_result;
223		#ifdef CONFIG_MULTICORE_RAID456
224		unsigned long	     request;
225		wait_queue_head_t    wait_for_ops;
226		#endif
227	} ops;
228	struct r5dev {
229		/* rreq and rvec are used for the replacement device when
230		 * writing data to both devices.
231		 */
232		struct bio	req, rreq;
233		struct bio_vec	vec, rvec;
234		struct page	*page;
235		struct bio	*toread, *read, *towrite, *written;
236		sector_t	sector;			/* sector of this page */
237		unsigned long	flags;
238	} dev[1]; /* allocated with extra space depending of RAID geometry */
239};
240
241/* stripe_head_state - collects and tracks the dynamic state of a stripe_head
242 *     for handle_stripe.
243 */
244struct stripe_head_state {
245	/* 'syncing' means that we need to read all devices, either
246	 * to check/correct parity, or to reconstruct a missing device.
247	 * 'replacing' means we are replacing one or more drives and
248	 * the source is valid at this point so we don't need to
249	 * read all devices, just the replacement targets.
250	 */
251	int syncing, expanding, expanded, replacing;
252	int locked, uptodate, to_read, to_write, failed, written;
253	int to_fill, compute, req_compute, non_overwrite;
254	int failed_num[2];
255	int p_failed, q_failed;
256	int dec_preread_active;
257	unsigned long ops_request;
258
259	struct bio *return_bi;
260	struct md_rdev *blocked_rdev;
261	int handle_bad_blocks;
262};
263
264/* Flags for struct r5dev.flags */
265enum r5dev_flags {
266	R5_UPTODATE,	/* page contains current data */
267	R5_LOCKED,	/* IO has been submitted on "req" */
268	R5_DOUBLE_LOCKED,/* Cannot clear R5_LOCKED until 2 writes complete */
269	R5_OVERWRITE,	/* towrite covers whole page */
270/* and some that are internal to handle_stripe */
271	R5_Insync,	/* rdev && rdev->in_sync at start */
272	R5_Wantread,	/* want to schedule a read */
273	R5_Wantwrite,
274	R5_Overlap,	/* There is a pending overlapping request
275			 * on this block */
276	R5_ReadError,	/* seen a read error here recently */
277	R5_ReWrite,	/* have tried to over-write the readerror */
278
279	R5_Expanded,	/* This block now has post-expand data */
280	R5_Wantcompute,	/* compute_block in progress treat as
281			 * uptodate
282			 */
283	R5_Wantfill,	/* dev->toread contains a bio that needs
284			 * filling
285			 */
286	R5_Wantdrain,	/* dev->towrite needs to be drained */
287	R5_WantFUA,	/* Write should be FUA */
288	R5_SyncIO,	/* The IO is sync */
289	R5_WriteError,	/* got a write error - need to record it */
290	R5_MadeGood,	/* A bad block has been fixed by writing to it */
291	R5_ReadRepl,	/* Will/did read from replacement rather than orig */
292	R5_MadeGoodRepl,/* A bad block on the replacement device has been
293			 * fixed by writing to it */
294	R5_NeedReplace,	/* This device has a replacement which is not
295			 * up-to-date at this stripe. */
296	R5_WantReplace, /* We need to update the replacement, we have read
297			 * data in, and now is a good time to write it out.
298			 */
299};
300
301/*
302 * Stripe state
303 */
304enum {
305	STRIPE_ACTIVE,
306	STRIPE_HANDLE,
307	STRIPE_SYNC_REQUESTED,
308	STRIPE_SYNCING,
309	STRIPE_INSYNC,
310	STRIPE_PREREAD_ACTIVE,
311	STRIPE_DELAYED,
312	STRIPE_DEGRADED,
313	STRIPE_BIT_DELAY,
314	STRIPE_EXPANDING,
315	STRIPE_EXPAND_SOURCE,
316	STRIPE_EXPAND_READY,
317	STRIPE_IO_STARTED,	/* do not count towards 'bypass_count' */
318	STRIPE_FULL_WRITE,	/* all blocks are set to be overwritten */
319	STRIPE_BIOFILL_RUN,
320	STRIPE_COMPUTE_RUN,
321	STRIPE_OPS_REQ_PENDING,
322};
323
324/*
325 * Operation request flags
326 */
327enum {
328	STRIPE_OP_BIOFILL,
329	STRIPE_OP_COMPUTE_BLK,
330	STRIPE_OP_PREXOR,
331	STRIPE_OP_BIODRAIN,
332	STRIPE_OP_RECONSTRUCT,
333	STRIPE_OP_CHECK,
334};
335/*
336 * Plugging:
337 *
338 * To improve write throughput, we need to delay the handling of some
339 * stripes until there has been a chance that several write requests
340 * for the one stripe have all been collected.
341 * In particular, any write request that would require pre-reading
342 * is put on a "delayed" queue until there are no stripes currently
343 * in a pre-read phase.  Further, if the "delayed" queue is empty when
344 * a stripe is put on it then we "plug" the queue and do not process it
345 * until an unplug call is made. (the unplug_io_fn() is called).
346 *
347 * When preread is initiated on a stripe, we set PREREAD_ACTIVE and add
348 * it to the count of prereading stripes.
349 * When write is initiated, or the stripe refcnt == 0 (just in case) we
350 * clear the PREREAD_ACTIVE flag and decrement the count
351 * Whenever the 'handle' queue is empty and the device is not plugged, we
352 * move any strips from delayed to handle and clear the DELAYED flag and set
353 * PREREAD_ACTIVE.
354 * In stripe_handle, if we find pre-reading is necessary, we do it if
355 * PREREAD_ACTIVE is set, else we set DELAYED which will send it to the delayed queue.
356 * HANDLE gets cleared if stripe_handle leaves nothing locked.
357 */
358
359
360struct disk_info {
361	struct md_rdev	*rdev, *replacement;
362};
363
364struct r5conf {
365	struct hlist_head	*stripe_hashtbl;
366	struct mddev		*mddev;
367	int			chunk_sectors;
368	int			level, algorithm;
369	int			max_degraded;
370	int			raid_disks;
371	int			max_nr_stripes;
372
373	/* reshape_progress is the leading edge of a 'reshape'
374	 * It has value MaxSector when no reshape is happening
375	 * If delta_disks < 0, it is the last sector we started work on,
376	 * else is it the next sector to work on.
377	 */
378	sector_t		reshape_progress;
379	/* reshape_safe is the trailing edge of a reshape.  We know that
380	 * before (or after) this address, all reshape has completed.
381	 */
382	sector_t		reshape_safe;
383	int			previous_raid_disks;
384	int			prev_chunk_sectors;
385	int			prev_algo;
386	short			generation; /* increments with every reshape */
387	unsigned long		reshape_checkpoint; /* Time we last updated
388						     * metadata */
389	long long		min_offset_diff; /* minimum difference between
390						  * data_offset and
391						  * new_data_offset across all
392						  * devices.  May be negative,
393						  * but is closest to zero.
394						  */
395
396	struct list_head	handle_list; /* stripes needing handling */
397	struct list_head	hold_list; /* preread ready stripes */
398	struct list_head	delayed_list; /* stripes that have plugged requests */
399	struct list_head	bitmap_list; /* stripes delaying awaiting bitmap update */
400	struct bio		*retry_read_aligned; /* currently retrying aligned bios   */
401	struct bio		*retry_read_aligned_list; /* aligned bios retry list  */
402	atomic_t		preread_active_stripes; /* stripes with scheduled io */
403	atomic_t		active_aligned_reads;
404	atomic_t		pending_full_writes; /* full write backlog */
405	int			bypass_count; /* bypassed prereads */
406	int			bypass_threshold; /* preread nice */
407	struct list_head	*last_hold; /* detect hold_list promotions */
408
409	atomic_t		reshape_stripes; /* stripes with pending writes for reshape */
410	/* unfortunately we need two cache names as we temporarily have
411	 * two caches.
412	 */
413	int			active_name;
414	char			cache_name[2][32];
415	struct kmem_cache		*slab_cache; /* for allocating stripes */
416
417	int			seq_flush, seq_write;
418	int			quiesce;
419
420	int			fullsync;  /* set to 1 if a full sync is needed,
421					    * (fresh device added).
422					    * Cleared when a sync completes.
423					    */
424	int			recovery_disabled;
425	/* per cpu variables */
426	struct raid5_percpu {
427		struct page	*spare_page; /* Used when checking P/Q in raid6 */
428		void		*scribble;   /* space for constructing buffer
429					      * lists and performing address
430					      * conversions
431					      */
432	} __percpu *percpu;
433	size_t			scribble_len; /* size of scribble region must be
434					       * associated with conf to handle
435					       * cpu hotplug while reshaping
436					       */
437#ifdef CONFIG_HOTPLUG_CPU
438	struct notifier_block	cpu_notify;
439#endif
440
441	/*
442	 * Free stripes pool
443	 */
444	atomic_t		active_stripes;
445	struct list_head	inactive_list;
446	wait_queue_head_t	wait_for_stripe;
447	wait_queue_head_t	wait_for_overlap;
448	int			inactive_blocked;	/* release of inactive stripes blocked,
449							 * waiting for 25% to be free
450							 */
451	int			pool_size; /* number of disks in stripeheads in pool */
452	spinlock_t		device_lock;
453	struct disk_info	*disks;
454
455	/* When taking over an array from a different personality, we store
456	 * the new thread here until we fully activate the array.
457	 */
458	struct md_thread	*thread;
459};
460
461/*
462 * Our supported algorithms
463 */
464#define ALGORITHM_LEFT_ASYMMETRIC	0 /* Rotating Parity N with Data Restart */
465#define ALGORITHM_RIGHT_ASYMMETRIC	1 /* Rotating Parity 0 with Data Restart */
466#define ALGORITHM_LEFT_SYMMETRIC	2 /* Rotating Parity N with Data Continuation */
467#define ALGORITHM_RIGHT_SYMMETRIC	3 /* Rotating Parity 0 with Data Continuation */
468
469/* Define non-rotating (raid4) algorithms.  These allow
470 * conversion of raid4 to raid5.
471 */
472#define ALGORITHM_PARITY_0		4 /* P or P,Q are initial devices */
473#define ALGORITHM_PARITY_N		5 /* P or P,Q are final devices. */
474
475/* DDF RAID6 layouts differ from md/raid6 layouts in two ways.
476 * Firstly, the exact positioning of the parity block is slightly
477 * different between the 'LEFT_*' modes of md and the "_N_*" modes
478 * of DDF.
479 * Secondly, or order of datablocks over which the Q syndrome is computed
480 * is different.
481 * Consequently we have different layouts for DDF/raid6 than md/raid6.
482 * These layouts are from the DDFv1.2 spec.
483 * Interestingly DDFv1.2-Errata-A does not specify N_CONTINUE but
484 * leaves RLQ=3 as 'Vendor Specific'
485 */
486
487#define ALGORITHM_ROTATING_ZERO_RESTART	8 /* DDF PRL=6 RLQ=1 */
488#define ALGORITHM_ROTATING_N_RESTART	9 /* DDF PRL=6 RLQ=2 */
489#define ALGORITHM_ROTATING_N_CONTINUE	10 /*DDF PRL=6 RLQ=3 */
490
491
492/* For every RAID5 algorithm we define a RAID6 algorithm
493 * with exactly the same layout for data and parity, and
494 * with the Q block always on the last device (N-1).
495 * This allows trivial conversion from RAID5 to RAID6
496 */
497#define ALGORITHM_LEFT_ASYMMETRIC_6	16
498#define ALGORITHM_RIGHT_ASYMMETRIC_6	17
499#define ALGORITHM_LEFT_SYMMETRIC_6	18
500#define ALGORITHM_RIGHT_SYMMETRIC_6	19
501#define ALGORITHM_PARITY_0_6		20
502#define ALGORITHM_PARITY_N_6		ALGORITHM_PARITY_N
503
504static inline int algorithm_valid_raid5(int layout)
505{
506	return (layout >= 0) &&
507		(layout <= 5);
508}
509static inline int algorithm_valid_raid6(int layout)
510{
511	return (layout >= 0 && layout <= 5)
512		||
513		(layout >= 8 && layout <= 10)
514		||
515		(layout >= 16 && layout <= 20);
516}
517
518static inline int algorithm_is_DDF(int layout)
519{
520	return layout >= 8 && layout <= 10;
521}
522
523extern int md_raid5_congested(struct mddev *mddev, int bits);
524extern void md_raid5_kick_device(struct r5conf *conf);
525extern int raid5_set_cache_size(struct mddev *mddev, int size);
526#endif