#ifndef _RAID5_H
  #define _RAID5_H
  
  #include <linux/raid/xor.h>
  #include <linux/dmaengine.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,
  };
  
  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 */
  	enum check_states	check_state;
  	enum reconstruct_states reconstruct_state;
  	spinlock_t		stripe_lock;
  	int			cpu;
  	struct r5worker_group	*group;
  	/**
  	 * 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;
  	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;
  		struct bio	*toread, *read, *towrite, *written;
  		sector_t	sector;			/* sector of this page */
  		unsigned long	flags;
  	} dev[1]; /* allocated with extra space depending of RAID geometry */
  };
  
  /* 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 failed_num[2];
  	int p_failed, q_failed;
  	int dec_preread_active;
  	unsigned long ops_request;
  
  	struct bio *return_bi;
  	struct md_rdev *blocked_rdev;
  	int handle_bad_blocks;
  };
  
  /* 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 */
  };
  
  /*
   * 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_OPS_REQ_PENDING,
  	STRIPE_ON_UNPLUG_LIST,
  	STRIPE_DISCARD,
  	STRIPE_ON_RELEASE_LIST,
  };
  
  /*
   * Operation request flags
   */
  enum {
  	STRIPE_OP_BIOFILL,
  	STRIPE_OP_COMPUTE_BLK,
  	STRIPE_OP_PREXOR,
  	STRIPE_OP_BIODRAIN,
  	STRIPE_OP_RECONSTRUCT,
  	STRIPE_OP_CHECK,
  };
  /*
   * 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.
   */
  
  
  struct disk_info {
  	struct md_rdev	*rdev, *replacement;
  };
  
  /* 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 r5conf *conf;
  	struct r5worker *workers;
  	int stripes_cnt;
  };
  
  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;
  	int			max_degraded;
  	int			raid_disks;
  	int			max_nr_stripes;
  
  	/* 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_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	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   */
  	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 */
  	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 */
  
  	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 {
  		struct page	*spare_page; /* Used when checking P/Q in raid6 */
  		void		*scribble;   /* space for constructing buffer
  					      * lists and performing address
  					      * conversions
  					      */
  	} __percpu *percpu;
  	size_t			scribble_len; /* size of scribble region must be
  					       * associated with conf to handle
  					       * cpu hotplug while reshaping
  					       */
  #ifdef CONFIG_HOTPLUG_CPU
  	struct notifier_block	cpu_notify;
  #endif
  
  	/*
  	 * Free stripes pool
  	 */
  	atomic_t		active_stripes;
  	struct list_head	inactive_list[NR_STRIPE_HASH_LOCKS];
  	atomic_t		empty_inactive_list_nr;
  	struct llist_head	released_stripes;
  	wait_queue_head_t	wait_for_stripe;
  	wait_queue_head_t	wait_for_overlap;
  	int			inactive_blocked;	/* release of inactive stripes blocked,
  							 * waiting for 25% to be free
  							 */
  	int			pool_size; /* number of disks in stripeheads in pool */
  	spinlock_t		device_lock;
  	struct disk_info	*disks;
  
  	/* When taking over an array from a different personality, we store
  	 * the new thread here until we fully activate the array.
  	 */
  	struct md_thread	*thread;
  	struct list_head	temp_inactive_list[NR_STRIPE_HASH_LOCKS];
  	struct r5worker_group	*worker_groups;
  	int			group_cnt;
  	int			worker_cnt_per_group;
  };
  
  /*
   * 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;
  }
  
  extern int md_raid5_congested(struct mddev *mddev, int bits);
  extern void md_raid5_kick_device(struct r5conf *conf);
  extern int raid5_set_cache_size(struct mddev *mddev, int size);
  #endif