include/linux/raid/raid5.h - arm/linux-arm64-legacy - Git at Google

 #ifndef _RAID5_H
 #define _RAID5_H

 #include <linux/raid/md.h>
 #include <linux/raid/xor.h>

 /*
  *
  * Each stripe contains one buffer per disc.  Each buffer can be in
  * one of a number of states stored in "flags".  Changes between
  * these states happen *almost* exclusively under a per-stripe
  * spinlock.  Some very specific changes can happen in bi_end_io, and
  * these are not protected by the spin lock.
  *
  * 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.(RECONSTRUCT_WRITE)
  *  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 distingush 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 is
  * protected by the device_lock.  The write and written lists are
  * protected by the stripe lock.  The device_lock, which can be
  * claimed while the stipe lock is held, 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 on the inactive_list never have their stripe_lock held.
  *  - 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())
  *     lockstripe clrSTRIPE_HANDLE ... (lockdev check-buffers unlockdev) .. change-state .. record io needed unlockstripe schedule io
  *  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.
  */

 struct stripe_head {
 	struct stripe_head	*hash_next, **hash_pprev; /* hash pointers */
 	struct list_head	lru;			/* inactive_list or handle_list */
 	struct raid5_private_data	*raid_conf;
 	sector_t		sector;			/* sector of this row */
 	int			pd_idx;			/* parity disk index */
 	unsigned long		state;			/* state flags */
 	atomic_t		count;			/* nr of active thread/requests */
 	spinlock_t		lock;
 	int			bm_seq;	/* sequence number for bitmap flushes */
 	struct r5dev {
 		struct bio	req;
 		struct bio_vec	vec;
 		struct page	*page;
 		struct bio	*toread, *towrite, *written;
 		sector_t	sector;			/* sector of this page */
 		unsigned long	flags;
 	} dev[1]; /* allocated with extra space depending of RAID geometry */
 };
 /* Flags */
 #define	R5_UPTODATE	0	/* page contains current data */
 #define	R5_LOCKED	1	/* IO has been submitted on "req" */
 #define	R5_OVERWRITE	2	/* towrite covers whole page */
 /* and some that are internal to handle_stripe */
 #define	R5_Insync	3	/* rdev && rdev->in_sync at start */
 #define	R5_Wantread	4	/* want to schedule a read */
 #define	R5_Wantwrite	5
 #define	R5_Syncio	6	/* this io need to be accounted as resync io */
 #define	R5_Overlap	7	/* There is a pending overlapping request on this block */
 #define	R5_ReadError	8	/* seen a read error here recently */
 #define	R5_ReWrite	9	/* have tried to over-write the readerror */

 /*
  * Write method
  */
 #define RECONSTRUCT_WRITE	1
 #define READ_MODIFY_WRITE	2
 /* not a write method, but a compute_parity mode */
 #define	CHECK_PARITY		3

 /*
  * Stripe state
  */
 #define STRIPE_HANDLE		2
 #define	STRIPE_SYNCING		3
 #define	STRIPE_INSYNC		4
 #define	STRIPE_PREREAD_ACTIVE	5
 #define	STRIPE_DELAYED		6
 #define	STRIPE_DEGRADED		7
 #define	STRIPE_BIT_DELAY	8

 /*
  * 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 delayed 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 leave nothing locked.
  */


 struct disk_info {
 	mdk_rdev_t	*rdev;
 };

 struct raid5_private_data {
 	struct stripe_head	**stripe_hashtbl;
 	mddev_t			*mddev;
 	struct disk_info	*spare;
 	int			chunk_size, level, algorithm;
 	int			raid_disks, working_disks, failed_disks;
 	int			max_nr_stripes;

 	struct list_head	handle_list; /* stripes needing handling */
 	struct list_head	delayed_list; /* stripes that have plugged requests */
 	struct list_head	bitmap_list; /* stripes delaying awaiting bitmap update */
 	atomic_t		preread_active_stripes; /* stripes with scheduled io */

 	char			cache_name[20];
 	kmem_cache_t		*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.
 					    */

 	/*
 	 * Free stripes pool
 	 */
 	atomic_t		active_stripes;
 	struct list_head	inactive_list;
 	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
 							 */
 	spinlock_t		device_lock;
 	struct disk_info	disks[0];
 };

 typedef struct raid5_private_data raid5_conf_t;

 #define mddev_to_conf(mddev) ((raid5_conf_t *) mddev->private)

 /*
  * Our supported algorithms
  */
 #define ALGORITHM_LEFT_ASYMMETRIC	0
 #define ALGORITHM_RIGHT_ASYMMETRIC	1
 #define ALGORITHM_LEFT_SYMMETRIC	2
 #define ALGORITHM_RIGHT_SYMMETRIC	3

 #endif
	#ifndef _RAID5_H
	#define _RAID5_H

	#include <linux/raid/md.h>
	#include <linux/raid/xor.h>

	/*
	*
	* Each stripe contains one buffer per disc. Each buffer can be in
	* one of a number of states stored in "flags". Changes between
	* these states happen almost exclusively under a per-stripe
	* spinlock. Some very specific changes can happen in bi_end_io, and
	* these are not protected by the spin lock.
	*
	* 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.(RECONSTRUCT_WRITE)
	* 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 distingush 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 is
	* protected by the device_lock. The write and written lists are
	* protected by the stripe lock. The device_lock, which can be
	* claimed while the stipe lock is held, 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 on the inactive_list never have their stripe_lock held.
	* - 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())
	* lockstripe clrSTRIPE_HANDLE ... (lockdev check-buffers unlockdev) .. change-state .. record io needed unlockstripe schedule io
	* 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.
	*/

	struct stripe_head {
	struct stripe_head hash_next, hash_pprev; / hash pointers */
	struct list_head lru; /* inactive_list or handle_list */
	struct raid5_private_data *raid_conf;
	sector_t sector; /* sector of this row */
	int pd_idx; /* parity disk index */
	unsigned long state; /* state flags */
	atomic_t count; /* nr of active thread/requests */
	spinlock_t lock;
	int bm_seq; /* sequence number for bitmap flushes */
	struct r5dev {
	struct bio req;
	struct bio_vec vec;
	struct page *page;
	struct bio toread, towrite, *written;
	sector_t sector; /* sector of this page */
	unsigned long flags;
	} dev[1]; /* allocated with extra space depending of RAID geometry */
	};
	/* Flags */
	#define R5_UPTODATE 0 /* page contains current data */
	#define R5_LOCKED 1 /* IO has been submitted on "req" */
	#define R5_OVERWRITE 2 /* towrite covers whole page */
	/* and some that are internal to handle_stripe */
	#define R5_Insync 3 /* rdev && rdev->in_sync at start */
	#define R5_Wantread 4 /* want to schedule a read */
	#define R5_Wantwrite 5
	#define R5_Syncio 6 /* this io need to be accounted as resync io */
	#define R5_Overlap 7 /* There is a pending overlapping request on this block */
	#define R5_ReadError 8 /* seen a read error here recently */
	#define R5_ReWrite 9 /* have tried to over-write the readerror */

	/*
	* Write method
	*/
	#define RECONSTRUCT_WRITE 1
	#define READ_MODIFY_WRITE 2
	/* not a write method, but a compute_parity mode */
	#define CHECK_PARITY 3

	/*
	* Stripe state
	*/
	#define STRIPE_HANDLE 2
	#define STRIPE_SYNCING 3
	#define STRIPE_INSYNC 4
	#define STRIPE_PREREAD_ACTIVE 5
	#define STRIPE_DELAYED 6
	#define STRIPE_DEGRADED 7
	#define STRIPE_BIT_DELAY 8

	/*
	* 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 delayed 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 leave nothing locked.
	*/


	struct disk_info {
	mdk_rdev_t *rdev;
	};

	struct raid5_private_data {
	struct stripe_head **stripe_hashtbl;
	mddev_t *mddev;
	struct disk_info *spare;
	int chunk_size, level, algorithm;
	int raid_disks, working_disks, failed_disks;
	int max_nr_stripes;

	struct list_head handle_list; /* stripes needing handling */
	struct list_head delayed_list; /* stripes that have plugged requests */
	struct list_head bitmap_list; /* stripes delaying awaiting bitmap update */
	atomic_t preread_active_stripes; /* stripes with scheduled io */

	char cache_name[20];
	kmem_cache_t 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.
	*/

	/*
	* Free stripes pool
	*/
	atomic_t active_stripes;
	struct list_head inactive_list;
	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
	*/
	spinlock_t device_lock;
	struct disk_info disks[0];
	};

	typedef struct raid5_private_data raid5_conf_t;

	#define mddev_to_conf(mddev) ((raid5_conf_t *) mddev->private)

	/*
	* Our supported algorithms
	*/
	#define ALGORITHM_LEFT_ASYMMETRIC 0
	#define ALGORITHM_RIGHT_ASYMMETRIC 1
	#define ALGORITHM_LEFT_SYMMETRIC 2
	#define ALGORITHM_RIGHT_SYMMETRIC 3

	#endif