File /code/usr/include/linux/raid/raid5.h

#ifndef _RAID5_H
#define _RAID5_H

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


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;
	struct buffer_head	*bh_cache[MD_SB_DISKS];	/* buffered copy */
	struct buffer_head	*bh_read[MD_SB_DISKS];	/* read request buffers of the MD device */
	struct buffer_head	*bh_write[MD_SB_DISKS];	/* write request buffers of the MD device */
	struct buffer_head	*bh_written[MD_SB_DISKS]; /* write request buffers of the MD device that have been scheduled for write */
	struct page		*bh_page[MD_SB_DISKS];	/* saved bh_cache[n]->b_page when reading around the cache */
	unsigned long		sector;			/* sector of this row */
	int			size;			/* buffers size */
	int			pd_idx;			/* parity disk index */
	unsigned long		state;			/* state flags */
	atomic_t		count;			/* nr of active thread/requests */
	spinlock_t		lock;
	int			sync_redone;
};


/*
 * 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_ERROR		1
#define STRIPE_HANDLE		2
#define	STRIPE_SYNCING		3
#define	STRIPE_INSYNC		4
#define	STRIPE_PREREAD_ACTIVE	5
#define	STRIPE_DELAYED		6

/*
 * 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 unplg call is made. (the tq_disk list is run).
 *
 * 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 {
	kdev_t	dev;
	int	operational;
	int	number;
	int	raid_disk;
	int	write_only;
	int	spare;
	int	used_slot;
};

struct raid5_private_data {
	struct stripe_head	**stripe_hashtbl;
	mddev_t			*mddev;
	mdk_thread_t		*thread, *resync_thread;
	struct disk_info	disks[MD_SB_DISKS];
	struct disk_info	*spare;
	int			buffer_size;
	int			chunk_size, level, algorithm;
	int			raid_disks, working_disks, failed_disks;
	int			resync_parity;
	int			max_nr_stripes;

	struct list_head	handle_list; /* stripes needing handling */
	struct list_head	delayed_list; /* stripes that have plugged requests */
	atomic_t		preread_active_stripes; /* stripes with scheduled io */
	/*
	 * Free stripes pool
	 */
	atomic_t		active_stripes;
	struct list_head	inactive_list;
	md_wait_queue_head_t	wait_for_stripe;
	int			inactive_blocked;	/* release of inactive stripes blocked,
							 * waiting for 25% to be free
							 */        
	md_spinlock_t		device_lock;

	int			plugged;
	struct tq_struct	plug_tq;
};

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