/*****************************************************************************
 * raid5.c : Multiple Devices driver for Linux
 *           Copyright (C) 1996, 1997 Ingo Molnar, Miguel de Icaza, Gadi Oxman
 *
 * RAID-5 management functions.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * You should have received a copy of the GNU General Public License
 * (for example /usr/src/linux/COPYING); if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/module.h>
#include <linux/locks.h>
#include <linux/malloc.h>
#include <linux/md.h>
#include <linux/raid5.h>
#include <asm/bitops.h>
#include <asm/atomic.h>

static struct md_personality raid5_personality;

/*
 * Stripe cache
 */
#define NR_STRIPES		128
#define HASH_PAGES		1
#define HASH_PAGES_ORDER	0
#define NR_HASH			(HASH_PAGES * PAGE_SIZE / sizeof(struct stripe_head *))
#define HASH_MASK		(NR_HASH - 1)
#define stripe_hash(raid_conf, sect, size)	((raid_conf)->stripe_hashtbl[((sect) / (size >> 9)) & HASH_MASK])

/*
 * The following can be used to debug the driver
 */
#define RAID5_DEBUG	0

#if RAID5_DEBUG
#define PRINTK(x)   do { printk x; } while (0);
#else
#define PRINTK(x)   do { ; } while (0)
#endif

static inline int stripe_locked(struct stripe_head *sh)
{
	return test_bit(STRIPE_LOCKED, &sh->state);
}

static inline int stripe_error(struct stripe_head *sh)
{
	return test_bit(STRIPE_ERROR, &sh->state);
}

/*
 * Stripes are locked whenever new buffers can't be added to them.
 */
static inline void lock_stripe(struct stripe_head *sh)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	if (!test_and_set_bit(STRIPE_LOCKED, &sh->state)) {
		PRINTK(("locking stripe %lu\n", sh->sector));
		raid_conf->nr_locked_stripes++;
	}
}

static inline void unlock_stripe(struct stripe_head *sh)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	if (test_and_clear_bit(STRIPE_LOCKED, &sh->state)) {
		PRINTK(("unlocking stripe %lu\n", sh->sector));
		raid_conf->nr_locked_stripes--;
		wake_up(&sh->wait);
	}
}

static inline void finish_stripe(struct stripe_head *sh)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	unlock_stripe(sh);
	sh->cmd = STRIPE_NONE;
	sh->phase = PHASE_COMPLETE;
	raid_conf->nr_pending_stripes--;
	raid_conf->nr_cached_stripes++;
	wake_up(&raid_conf->wait_for_stripe);
}

void __wait_on_stripe(struct stripe_head *sh)
{
	struct wait_queue wait = { current, NULL };

	PRINTK(("wait_on_stripe %lu\n", sh->sector));
	sh->count++;
	add_wait_queue(&sh->wait, &wait);
repeat:
	current->state = TASK_UNINTERRUPTIBLE;
	if (stripe_locked(sh)) {
		schedule();
		goto repeat;
	}
	PRINTK(("wait_on_stripe %lu done\n", sh->sector));
	remove_wait_queue(&sh->wait, &wait);
	sh->count--;
	current->state = TASK_RUNNING;
}

static inline void wait_on_stripe(struct stripe_head *sh)
{
	if (stripe_locked(sh))
		__wait_on_stripe(sh);
}

static inline void remove_hash(struct raid5_data *raid_conf, struct stripe_head *sh)
{
	PRINTK(("remove_hash(), stripe %lu\n", sh->sector));

	if (sh->hash_pprev) {
		if (sh->hash_next)
			sh->hash_next->hash_pprev = sh->hash_pprev;
		*sh->hash_pprev = sh->hash_next;
		sh->hash_pprev = NULL;
		raid_conf->nr_hashed_stripes--;
	}
}

static inline void insert_hash(struct raid5_data *raid_conf, struct stripe_head *sh)
{
	struct stripe_head **shp = &stripe_hash(raid_conf, sh->sector, sh->size);

	PRINTK(("insert_hash(), stripe %lu, nr_hashed_stripes %d\n", sh->sector, raid_conf->nr_hashed_stripes));

	if ((sh->hash_next = *shp) != NULL)
		(*shp)->hash_pprev = &sh->hash_next;
	*shp = sh;
	sh->hash_pprev = shp;
	raid_conf->nr_hashed_stripes++;
}

static struct buffer_head *get_free_buffer(struct stripe_head *sh, int b_size)
{
	struct buffer_head *bh;
	unsigned long flags;

	save_flags(flags);
	cli();
	if ((bh = sh->buffer_pool) == NULL)
		return NULL;
	sh->buffer_pool = bh->b_next;
	bh->b_size = b_size;
	restore_flags(flags);
	return bh;
}

static struct buffer_head *get_free_bh(struct stripe_head *sh)
{
	struct buffer_head *bh;
	unsigned long flags;

	save_flags(flags);
	cli();
	if ((bh = sh->bh_pool) == NULL)
		return NULL;
	sh->bh_pool = bh->b_next;
	restore_flags(flags);
	return bh;
}

static void put_free_buffer(struct stripe_head *sh, struct buffer_head *bh)
{
	unsigned long flags;

	save_flags(flags);
	cli();
	bh->b_next = sh->buffer_pool;
	sh->buffer_pool = bh;
	restore_flags(flags);
}

static void put_free_bh(struct stripe_head *sh, struct buffer_head *bh)
{
	unsigned long flags;

	save_flags(flags);
	cli();
	bh->b_next = sh->bh_pool;
	sh->bh_pool = bh;
	restore_flags(flags);
}

static struct stripe_head *get_free_stripe(struct raid5_data *raid_conf)
{
	struct stripe_head *sh;
	unsigned long flags;

	save_flags(flags);
	cli();
	if ((sh = raid_conf->free_sh_list) == NULL) {
		restore_flags(flags);
		return NULL;
	}
	raid_conf->free_sh_list = sh->free_next;
	raid_conf->nr_free_sh--;
	if (!raid_conf->nr_free_sh && raid_conf->free_sh_list)
		printk ("raid5: bug: free_sh_list != NULL, nr_free_sh == 0\n");
	restore_flags(flags);
	if (sh->hash_pprev || sh->nr_pending || sh->count)
		printk("get_free_stripe(): bug\n");
	return sh;
}

static void put_free_stripe(struct raid5_data *raid_conf, struct stripe_head *sh)
{
	unsigned long flags;

	save_flags(flags);
	cli();
	sh->free_next = raid_conf->free_sh_list;
	raid_conf->free_sh_list = sh;
	raid_conf->nr_free_sh++;
	restore_flags(flags);
}

static void shrink_buffers(struct stripe_head *sh, int num)
{
	struct buffer_head *bh;

	while (num--) {
		if ((bh = get_free_buffer(sh, -1)) == NULL)
			return;
		free_page((unsigned long) bh->b_data);
		kfree(bh);
	}
}

static void shrink_bh(struct stripe_head *sh, int num)
{
	struct buffer_head *bh;

	while (num--) {
		if ((bh = get_free_bh(sh)) == NULL)
			return;
		kfree(bh);
	}
}

static int grow_buffers(struct stripe_head *sh, int num, int b_size, int priority)
{
	struct buffer_head *bh;

	while (num--) {
		if ((bh = kmalloc(sizeof(struct buffer_head), priority)) == NULL)
			return 1;
		memset(bh, 0, sizeof (struct buffer_head));
		bh->b_data = (char *) __get_free_page(priority);
		if (!bh->b_data) {
			kfree(bh);
			return 1;
		}
		bh->b_size = b_size;
		put_free_buffer(sh, bh);
	}
	return 0;
}

static int grow_bh(struct stripe_head *sh, int num, int priority)
{
	struct buffer_head *bh;

	while (num--) {
		if ((bh = kmalloc(sizeof(struct buffer_head), priority)) == NULL)
			return 1;
		memset(bh, 0, sizeof (struct buffer_head));
		put_free_bh(sh, bh);
	}
	return 0;
}

static void raid5_kfree_buffer(struct stripe_head *sh, struct buffer_head *bh)
{
	unsigned long flags;

	save_flags(flags);
	cli();
	put_free_buffer(sh, bh);
	restore_flags(flags);
}

static void raid5_kfree_bh(struct stripe_head *sh, struct buffer_head *bh)
{
	unsigned long flags;

	save_flags(flags);
	cli();
	put_free_bh(sh, bh);
	restore_flags(flags);
}

static void raid5_kfree_old_bh(struct stripe_head *sh, int i)
{
	if (!sh->bh_old[i]) {
		printk("raid5_kfree_old_bh: bug: sector %lu, index %d not present\n", sh->sector, i);
		return;
	}
	raid5_kfree_buffer(sh, sh->bh_old[i]);
	sh->bh_old[i] = NULL;
}

static void raid5_update_old_bh(struct stripe_head *sh, int i)
{
	PRINTK(("stripe %lu, idx %d, updating cache copy\n", sh->sector, i));
	if (!sh->bh_copy[i]) {
		printk("raid5_update_old_bh: bug: sector %lu, index %d not present\n", sh->sector, i);
		return;
	}
	if (sh->bh_old[i])
		raid5_kfree_old_bh(sh, i);
	sh->bh_old[i] = sh->bh_copy[i];
	sh->bh_copy[i] = NULL;
}

static void kfree_stripe(struct stripe_head *sh)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	int disks = raid_conf->raid_disks, j;

	PRINTK(("kfree_stripe called, stripe %lu\n", sh->sector));
	if (sh->phase != PHASE_COMPLETE || stripe_locked(sh) || sh->count) {
		printk("raid5: kfree_stripe(), sector %lu, phase %d, locked %d, count %d\n", sh->sector, sh->phase, stripe_locked(sh), sh->count);
		return;
	}
	for (j = 0; j < disks; j++) {
		if (sh->bh_old[j])
			raid5_kfree_old_bh(sh, j);
		if (sh->bh_new[j] || sh->bh_copy[j])
			printk("raid5: bug: sector %lu, new %p, copy %p\n", sh->sector, sh->bh_new[j], sh->bh_copy[j]);
	}
	remove_hash(raid_conf, sh);
	put_free_stripe(raid_conf, sh);
}

static int shrink_stripe_cache(struct raid5_data *raid_conf, int nr)
{
	struct stripe_head *sh;
	int i, count = 0;

	PRINTK(("shrink_stripe_cache called, %d/%d, clock %d\n", nr, raid_conf->nr_hashed_stripes, raid_conf->clock));
	for (i = 0; i < NR_HASH; i++) {
repeat:
		sh = raid_conf->stripe_hashtbl[(i + raid_conf->clock) & HASH_MASK];
		for (; sh; sh = sh->hash_next) {
			if (sh->phase != PHASE_COMPLETE)
				continue;
			if (stripe_locked(sh))
				continue;
			if (sh->count)
				continue;
			kfree_stripe(sh);
			if (++count == nr) {
				PRINTK(("shrink completed, nr_hashed_stripes %d\n", raid_conf->nr_hashed_stripes));
				raid_conf->clock = (i + raid_conf->clock) & HASH_MASK;
				return nr;
			}
			goto repeat;
		}
	}
	PRINTK(("shrink completed, nr_hashed_stripes %d\n", raid_conf->nr_hashed_stripes));
	return count;
}

static struct stripe_head *find_stripe(struct raid5_data *raid_conf, unsigned long sector, int size)
{
	struct stripe_head *sh;

	if (raid_conf->buffer_size != size) {
		PRINTK(("switching size, %d --> %d\n", raid_conf->buffer_size, size));
		shrink_stripe_cache(raid_conf, raid_conf->max_nr_stripes);
		raid_conf->buffer_size = size;
	}

	PRINTK(("find_stripe, sector %lu\n", sector));
	for (sh = stripe_hash(raid_conf, sector, size); sh; sh = sh->hash_next)
		if (sh->sector == sector && sh->raid_conf == raid_conf) {
			if (sh->size == size) {
				PRINTK(("found stripe %lu\n", sector));
				return sh;
			} else {
				PRINTK(("switching size for %lu, %d --> %d\n", sector, sh->size, size));
				kfree_stripe(sh);
				break;
			}
		}
	PRINTK(("stripe %lu not in cache\n", sector));
	return NULL;
}

static int grow_stripes(struct raid5_data *raid_conf, int num, int priority)
{
	struct stripe_head *sh;

	while (num--) {
		if ((sh = kmalloc(sizeof(struct stripe_head), priority)) == NULL)
			return 1;
		memset(sh, 0, sizeof(*sh));
		if (grow_buffers(sh, 2 * raid_conf->raid_disks, PAGE_SIZE, priority)) {
			shrink_buffers(sh, 2 * raid_conf->raid_disks);
			kfree(sh);
			return 1;
		}
		if (grow_bh(sh, raid_conf->raid_disks, priority)) {
			shrink_buffers(sh, 2 * raid_conf->raid_disks);
			shrink_bh(sh, raid_conf->raid_disks);
			kfree(sh);
			return 1;
		}
		put_free_stripe(raid_conf, sh);
		raid_conf->nr_stripes++;
	}
	return 0;
}

static void shrink_stripes(struct raid5_data *raid_conf, int num)
{
	struct stripe_head *sh;

	while (num--) {
		sh = get_free_stripe(raid_conf);
		if (!sh)
			break;
		shrink_buffers(sh, raid_conf->raid_disks * 2);
		shrink_bh(sh, raid_conf->raid_disks);
		kfree(sh);
		raid_conf->nr_stripes--;
	}
}

static struct stripe_head *kmalloc_stripe(struct raid5_data *raid_conf, unsigned long sector, int size)
{
	struct stripe_head *sh = NULL, *tmp;
	struct buffer_head *buffer_pool, *bh_pool;

	PRINTK(("kmalloc_stripe called\n"));

	while ((sh = get_free_stripe(raid_conf)) == NULL) {
		shrink_stripe_cache(raid_conf, raid_conf->max_nr_stripes / 8);
		if ((sh = get_free_stripe(raid_conf)) != NULL)
			break;
		if (!raid_conf->nr_pending_stripes)
			printk("raid5: bug: nr_free_sh == 0, nr_pending_stripes == 0\n");
		md_wakeup_thread(raid_conf->thread);
		PRINTK(("waiting for some stripes to complete\n"));
		sleep_on(&raid_conf->wait_for_stripe);
	}

	/*
	 * The above might have slept, so perhaps another process
	 * already created the stripe for us..
	 */
	if ((tmp = find_stripe(raid_conf, sector, size)) != NULL) { 
		put_free_stripe(raid_conf, sh);
		wait_on_stripe(tmp);
		return tmp;
	}
	if (sh) {
		buffer_pool = sh->buffer_pool;
		bh_pool = sh->bh_pool;
		memset(sh, 0, sizeof(*sh));
		sh->buffer_pool = buffer_pool;
		sh->bh_pool = bh_pool;
		sh->phase = PHASE_COMPLETE;
		sh->cmd = STRIPE_NONE;
		sh->raid_conf = raid_conf;
		sh->sector = sector;
		sh->size = size;
		raid_conf->nr_cached_stripes++;
		insert_hash(raid_conf, sh);
	} else printk("raid5: bug: kmalloc_stripe() == NULL\n");
	return sh;
}

static struct stripe_head *get_stripe(struct raid5_data *raid_conf, unsigned long sector, int size)
{
	struct stripe_head *sh;

	PRINTK(("get_stripe, sector %lu\n", sector));
	sh = find_stripe(raid_conf, sector, size);
	if (sh)
		wait_on_stripe(sh);
	else
		sh = kmalloc_stripe(raid_conf, sector, size);
	return sh;
}


static struct buffer_head *raid5_kmalloc_buffer(struct stripe_head *sh, int b_size)
{
	struct buffer_head *bh;

	if ((bh = get_free_buffer(sh, b_size)) == NULL)
		printk("raid5: bug: raid5_kmalloc_buffer() == NULL\n");
	return bh;
}

static struct buffer_head *raid5_kmalloc_bh(struct stripe_head *sh)
{
	struct buffer_head *bh;

	if ((bh = get_free_bh(sh)) == NULL)
		printk("raid5: bug: raid5_kmalloc_bh() == NULL\n");
	return bh;
}

static inline void raid5_end_buffer_io (struct stripe_head *sh, int i, int uptodate)
{
	struct buffer_head *bh = sh->bh_new[i];

	sh->bh_new[i] = NULL;
	raid5_kfree_bh(sh, sh->bh_req[i]);
	sh->bh_req[i] = NULL;
	bh->b_end_io(bh, uptodate);
	if (!uptodate)
		printk(KERN_ALERT "raid5: %s: unrecoverable I/O error for "
		       "block %lu\n", kdevname(bh->b_dev), bh->b_blocknr);
}

static inline void raid5_mark_buffer_uptodate (struct buffer_head *bh, int uptodate)
{
	if (uptodate)
		set_bit(BH_Uptodate, &bh->b_state);
	else
		clear_bit(BH_Uptodate, &bh->b_state);
}

static void raid5_end_request (struct buffer_head * bh, int uptodate)
{
	struct stripe_head *sh = bh->b_dev_id;
	struct raid5_data *raid_conf = sh->raid_conf;
	int disks = raid_conf->raid_disks, i;
	unsigned long flags;

	PRINTK(("end_request %lu, nr_pending %d\n", sh->sector, sh->nr_pending));
	save_flags(flags);
	cli();
	raid5_mark_buffer_uptodate(bh, uptodate);
	--sh->nr_pending;
	if (!sh->nr_pending) {
		md_wakeup_thread(raid_conf->thread);
		atomic_inc(&raid_conf->nr_handle);
	}
	if (!uptodate)
		md_error(bh->b_dev, bh->b_rdev);
	if (raid_conf->failed_disks) {
		for (i = 0; i < disks; i++) {
			if (raid_conf->disks[i].operational)
				continue;
			if (bh != sh->bh_old[i] && bh != sh->bh_req[i] && bh != sh->bh_copy[i])
				continue;
			if (bh->b_rdev != raid_conf->disks[i].dev)
				continue;
			set_bit(STRIPE_ERROR, &sh->state);
		}
	}
	restore_flags(flags);
}

static int raid5_map (struct md_dev *mddev, kdev_t *rdev,
		      unsigned long *rsector, unsigned long size)
{
	/* No complex mapping used: the core of the work is done in the
	 * request routine
	 */
	return 0;
}

static void raid5_build_block (struct stripe_head *sh, struct buffer_head *bh, int i)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	struct md_dev *mddev = raid_conf->mddev;
	int minor = (int) (mddev - md_dev);
	char *b_data;
	kdev_t dev = MKDEV(MD_MAJOR, minor);
	int block = sh->sector / (sh->size >> 9);

	b_data = ((volatile struct buffer_head *) bh)->b_data;
	memset (bh, 0, sizeof (struct buffer_head));
	init_buffer(bh, dev, block, raid5_end_request, sh);
	((volatile struct buffer_head *) bh)->b_data = b_data;

	bh->b_rdev	= raid_conf->disks[i].dev;
	bh->b_rsector   = sh->sector;

	bh->b_state	= (1 << BH_Req);
	bh->b_size	= sh->size;
	bh->b_list	= BUF_LOCKED;
}

static int raid5_error (struct md_dev *mddev, kdev_t dev)
{
	struct raid5_data *raid_conf = (struct raid5_data *) mddev->private;
	md_superblock_t *sb = mddev->sb;
	struct disk_info *disk;
	int i;

	PRINTK(("raid5_error called\n"));
	raid_conf->resync_parity = 0;
	for (i = 0, disk = raid_conf->disks; i < raid_conf->raid_disks; i++, disk++)
		if (disk->dev == dev && disk->operational) {
			disk->operational = 0;
			sb->disks[disk->number].state |= (1 << MD_FAULTY_DEVICE);
			sb->disks[disk->number].state &= ~(1 << MD_SYNC_DEVICE);
			sb->disks[disk->number].state &= ~(1 << MD_ACTIVE_DEVICE);
			sb->active_disks--;
			sb->working_disks--;
			sb->failed_disks++;
			mddev->sb_dirty = 1;
			raid_conf->working_disks--;
			raid_conf->failed_disks++;
			md_wakeup_thread(raid_conf->thread);
			printk (KERN_ALERT
				"RAID5: Disk failure on %s, disabling device."
				"Operation continuing on %d devices\n",
				kdevname (dev), raid_conf->working_disks);
		}
	return 0;
}	

/*
 * Input: a 'big' sector number, 
 * Output: index of the data and parity disk, and the sector # in them.
 */
static inline unsigned long 
raid5_compute_sector (int r_sector, unsigned int raid_disks, unsigned int data_disks,
			unsigned int * dd_idx, unsigned int * pd_idx, 
			struct raid5_data *raid_conf)
{
	unsigned int  stripe;
	int chunk_number, chunk_offset;
	unsigned long new_sector;
	int sectors_per_chunk = raid_conf->chunk_size >> 9;

	/* First compute the information on this sector */

	/*
	 * Compute the chunk number and the sector offset inside the chunk
	 */
	chunk_number = r_sector / sectors_per_chunk;
	chunk_offset = r_sector % sectors_per_chunk;

	/*
	 * Compute the stripe number
	 */
	stripe = chunk_number / data_disks;

	/*
	 * Compute the data disk and parity disk indexes inside the stripe
	 */
	*dd_idx = chunk_number % data_disks;

	/*
	 * Select the parity disk based on the user selected algorithm.
	 */
	if (raid_conf->level == 4)
		*pd_idx = data_disks;
	else switch (raid_conf->algorithm) {
		case ALGORITHM_LEFT_ASYMMETRIC:
			*pd_idx = data_disks - stripe % raid_disks;
			if (*dd_idx >= *pd_idx)
				(*dd_idx)++;
			break;
		case ALGORITHM_RIGHT_ASYMMETRIC:
			*pd_idx = stripe % raid_disks;
			if (*dd_idx >= *pd_idx)
				(*dd_idx)++;
			break;
		case ALGORITHM_LEFT_SYMMETRIC:
			*pd_idx = data_disks - stripe % raid_disks;
			*dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;
			break;
		case ALGORITHM_RIGHT_SYMMETRIC:
			*pd_idx = stripe % raid_disks;
			*dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;
			break;
		default:
			printk ("raid5: unsupported algorithm %d\n", raid_conf->algorithm);
	}

	/*
	 * Finally, compute the new sector number
	 */
	new_sector = stripe * sectors_per_chunk + chunk_offset;

#if 0
	if (	*dd_idx > data_disks || *pd_idx > data_disks || 
		chunk_offset + bh->b_size / 512 > sectors_per_chunk	)

		printk ("raid5: bug: dd_idx == %d, pd_idx == %d, chunk_offset == %d\n", 
				*dd_idx, *pd_idx, chunk_offset);
#endif

	return new_sector;
}

static unsigned long compute_blocknr(struct stripe_head *sh, int i)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	int raid_disks = raid_conf->raid_disks, data_disks = raid_disks - 1;
	unsigned long new_sector = sh->sector, check;
	int sectors_per_chunk = raid_conf->chunk_size >> 9;
	unsigned long stripe = new_sector / sectors_per_chunk;
	int chunk_offset = new_sector % sectors_per_chunk;
	int chunk_number, dummy1, dummy2, dd_idx = i;
	unsigned long r_sector, blocknr;

	switch (raid_conf->algorithm) {
		case ALGORITHM_LEFT_ASYMMETRIC:
		case ALGORITHM_RIGHT_ASYMMETRIC:
			if (i > sh->pd_idx)
				i--;
			break;
		case ALGORITHM_LEFT_SYMMETRIC:
		case ALGORITHM_RIGHT_SYMMETRIC:
			if (i < sh->pd_idx)
				i += raid_disks;
			i -= (sh->pd_idx + 1);
			break;
		default:
			printk ("raid5: unsupported algorithm %d\n", raid_conf->algorithm);
	}

	chunk_number = stripe * data_disks + i;
	r_sector = chunk_number * sectors_per_chunk + chunk_offset;
	blocknr = r_sector / (sh->size >> 9);

	check = raid5_compute_sector (r_sector, raid_disks, data_disks, &dummy1, &dummy2, raid_conf);
	if (check != sh->sector || dummy1 != dd_idx || dummy2 != sh->pd_idx) {
		printk("compute_blocknr: map not correct\n");
		return 0;
	}
	return blocknr;
}

static void xor_block(struct buffer_head *dest, struct buffer_head *source)
{
	int lines = dest->b_size / (sizeof (int)) / 8, i;
	int *destp = (int *) dest->b_data, *sourcep = (int *) source->b_data;

	for (i = lines; i > 0; i--) {
		*(destp + 0) ^= *(sourcep + 0);
		*(destp + 1) ^= *(sourcep + 1);
		*(destp + 2) ^= *(sourcep + 2);
		*(destp + 3) ^= *(sourcep + 3);
		*(destp + 4) ^= *(sourcep + 4);
		*(destp + 5) ^= *(sourcep + 5);
		*(destp + 6) ^= *(sourcep + 6);
		*(destp + 7) ^= *(sourcep + 7);
		destp += 8;
		sourcep += 8;
	}
}

static void compute_block(struct stripe_head *sh, int dd_idx)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	int i, disks = raid_conf->raid_disks;

	PRINTK(("compute_block, stripe %lu, idx %d\n", sh->sector, dd_idx));

	if (sh->bh_old[dd_idx] == NULL)
		sh->bh_old[dd_idx] = raid5_kmalloc_buffer(sh, sh->size);
	raid5_build_block(sh, sh->bh_old[dd_idx], dd_idx);

	memset(sh->bh_old[dd_idx]->b_data, 0, sh->size);
	for (i = 0; i < disks; i++) {
		if (i == dd_idx)
			continue;
		if (sh->bh_old[i]) {
			xor_block(sh->bh_old[dd_idx], sh->bh_old[i]);
			continue;
		} else
			printk("compute_block() %d, stripe %lu, %d not present\n", dd_idx, sh->sector, i);
	}
	raid5_mark_buffer_uptodate(sh->bh_old[dd_idx], 1);
}

static void compute_parity(struct stripe_head *sh, int method)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	int i, pd_idx = sh->pd_idx, disks = raid_conf->raid_disks;

	PRINTK(("compute_parity, stripe %lu, method %d\n", sh->sector, method));
	for (i = 0; i < disks; i++) {
		if (i == pd_idx || !sh->bh_new[i])
			continue;
		if (!sh->bh_copy[i])
			sh->bh_copy[i] = raid5_kmalloc_buffer(sh, sh->size);
		raid5_build_block(sh, sh->bh_copy[i], i);
		mark_buffer_clean(sh->bh_new[i]);
		memcpy(sh->bh_copy[i]->b_data, sh->bh_new[i]->b_data, sh->size);
	}
	if (sh->bh_copy[pd_idx] == NULL)
		sh->bh_copy[pd_idx] = raid5_kmalloc_buffer(sh, sh->size);
	raid5_build_block(sh, sh->bh_copy[pd_idx], sh->pd_idx);

	if (method == RECONSTRUCT_WRITE) {
		memset(sh->bh_copy[pd_idx]->b_data, 0, sh->size);
		for (i = 0; i < disks; i++) {
			if (i == sh->pd_idx)
				continue;
			if (sh->bh_new[i]) {
				xor_block(sh->bh_copy[pd_idx], sh->bh_copy[i]);
				continue;
			}
			if (sh->bh_old[i]) {
				xor_block(sh->bh_copy[pd_idx], sh->bh_old[i]);
				continue;
			}
		}
	} else if (method == READ_MODIFY_WRITE) {
		memcpy(sh->bh_copy[pd_idx]->b_data, sh->bh_old[pd_idx]->b_data, sh->size);
		for (i = 0; i < disks; i++) {
			if (i == sh->pd_idx)
				continue;
			if (sh->bh_new[i] && sh->bh_old[i]) {
				xor_block(sh->bh_copy[pd_idx], sh->bh_copy[i]);
				xor_block(sh->bh_copy[pd_idx], sh->bh_old[i]);
				continue;
			}
		}
	}
	raid5_mark_buffer_uptodate(sh->bh_copy[pd_idx], 1);
}

static void add_stripe_bh (struct stripe_head *sh, struct buffer_head *bh, int dd_idx, int rw)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	struct buffer_head *bh_req;

	if (sh->bh_new[dd_idx])
		printk("raid5: bug: stripe->bh_new[%d], sector %lu exists\n", dd_idx, sh->sector);

	set_bit(BH_Lock, &bh->b_state);

	bh_req = raid5_kmalloc_bh(sh);
	raid5_build_block(sh, bh_req, dd_idx);
	bh_req->b_data = bh->b_data;

	if (sh->phase == PHASE_COMPLETE && sh->cmd == STRIPE_NONE) {
		sh->phase = PHASE_BEGIN;
		sh->cmd = (rw == READ) ? STRIPE_READ : STRIPE_WRITE;
		raid_conf->nr_pending_stripes++;
		atomic_inc(&raid_conf->nr_handle);
	}
	sh->bh_new[dd_idx] = bh;
	sh->bh_req[dd_idx] = bh_req;
	sh->cmd_new[dd_idx] = rw;
	sh->new[dd_idx] = 1;
}

static void complete_stripe(struct stripe_head *sh)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	int disks = raid_conf->raid_disks;
	int i, new = 0;
	
	PRINTK(("complete_stripe %lu\n", sh->sector));
	for (i = 0; i < disks; i++) {
		if (sh->cmd == STRIPE_WRITE && i == sh->pd_idx)
			raid5_update_old_bh(sh, i);
		if (sh->bh_new[i]) {
			if (!sh->new[i]) {
#if 0
				if (sh->cmd == STRIPE_WRITE) {
					if (memcmp(sh->bh_new[i]->b_data, sh->bh_copy[i]->b_data, sh->size)) {
						printk("copy differs, %s, sector %lu ",
							test_bit(BH_Dirty, &sh->bh_new[i]->b_state) ? "dirty" : "clean",
							sh->sector);
					} else if (test_bit(BH_Dirty, &sh->bh_new[i]->b_state))
						printk("sector %lu dirty\n", sh->sector);
				}
#endif
				if (sh->cmd == STRIPE_WRITE)
					raid5_update_old_bh(sh, i);
				raid5_end_buffer_io(sh, i, 1);
				continue;
			} else
				new++;
		}
		if (new && sh->cmd == STRIPE_WRITE)
			printk("raid5: bug, completed STRIPE_WRITE with new == %d\n", new);
	}
	if (!new)
		finish_stripe(sh);
	else {
		PRINTK(("stripe %lu, new == %d\n", sh->sector, new));
		sh->phase = PHASE_BEGIN;
	}
}

/*
 * handle_stripe() is our main logic routine. Note that:
 *
 * 1.	lock_stripe() should be used whenever we can't accept additonal
 *	buffers, either during short sleeping in handle_stripe() or
 *	during io operations.
 *
 * 2.	We should be careful to set sh->nr_pending whenever we sleep,
 *	to prevent re-entry of handle_stripe() for the same sh.
 *
 * 3.	raid_conf->failed_disks and disk->operational can be changed
 *	from an interrupt. This complicates things a bit, but it allows
 *	us to stop issuing requests for a failed drive as soon as possible.
 */
static void handle_stripe(struct stripe_head *sh)
{
	struct raid5_data *raid_conf = sh->raid_conf;
	struct md_dev *mddev = raid_conf->mddev;
	int minor = (int) (mddev - md_dev);
	struct buffer_head *bh;
	int disks = raid_conf->raid_disks;
	int i, nr = 0, nr_read = 0, nr_write = 0;
	int nr_cache = 0, nr_cache_other = 0, nr_cache_overwrite = 0, parity = 0;
	int nr_failed_other = 0, nr_failed_overwrite = 0, parity_failed = 0;
	int reading = 0, nr_writing = 0;
	int method1 = INT_MAX, method2 = INT_MAX;
	int block;
	unsigned long flags;
	int operational[MD_SB_DISKS], failed_disks = raid_conf->failed_disks;

	PRINTK(("handle_stripe(), stripe %lu\n", sh->sector));
	if (sh->nr_pending) {
		printk("handle_stripe(), stripe %lu, io still pending\n", sh->sector);
		return;
	}
	if (sh->phase == PHASE_COMPLETE) {
		printk("handle_stripe(), stripe %lu, already complete\n", sh->sector);
		return;
	}

	atomic_dec(&raid_conf->nr_handle);

	if (test_and_clear_bit(STRIPE_ERROR, &sh->state)) {
		printk("raid5: restarting stripe %lu\n", sh->sector);
		sh->phase = PHASE_BEGIN;
	}

	if ((sh->cmd == STRIPE_WRITE && sh->phase == PHASE_WRITE) ||
	    (sh->cmd == STRIPE_READ && sh->phase == PHASE_READ)) {
		/*
		 * Completed
		 */
		complete_stripe(sh);
		if (sh->phase == PHASE_COMPLETE)
			return;
	}

	save_flags(flags);
	cli();
	for (i = 0; i < disks; i++) {
		operational[i] = raid_conf->disks[i].operational;
		if (i == sh->pd_idx && raid_conf->resync_parity)
			operational[i] = 0;
	}
	failed_disks = raid_conf->failed_disks;
	restore_flags(flags);

	if (failed_disks > 1) {
		for (i = 0; i < disks; i++) {
			if (sh->bh_new[i]) {
				raid5_end_buffer_io(sh, i, 0);
				continue;
			}
		}
		finish_stripe(sh);
		return;
	}

	for (i = 0; i < disks; i++) {
		if (sh->bh_old[i])
			nr_cache++;
		if (i == sh->pd_idx) {
			if (sh->bh_old[i])
				parity = 1;
			else if(!operational[i])
				parity_failed = 1;
			continue;
		}
		if (!sh->bh_new[i]) {
			if (sh->bh_old[i])
				nr_cache_other++;
			else if (!operational[i])
				nr_failed_other++;
			continue;
		}
		sh->new[i] = 0;
		nr++;
		if (sh->cmd_new[i] == READ)
			nr_read++;
		if (sh->cmd_new[i] == WRITE)
			nr_write++;
		if (sh->bh_old[i])
			nr_cache_overwrite++;
		else if (!operational[i])
			nr_failed_overwrite++;
	}

	if (nr_write && nr_read)
		printk("raid5: bug, nr_write == %d, nr_read == %d, sh->cmd == %d\n", nr_write, nr_read, sh->cmd);

	if (nr_write) {
		/*
		 * Attempt to add entries :-)
		 */
		if (nr_write != disks - 1) {
			for (i = 0; i < disks; i++) {
				if (i == sh->pd_idx)
					continue;
				if (sh->bh_new[i])
					continue;
				block = (int) compute_blocknr(sh, i);
				bh = find_buffer(MKDEV(MD_MAJOR, minor), block, sh->size);
				if (bh && bh->b_count == 0 && buffer_dirty(bh) && !buffer_locked(bh)) {
					PRINTK(("Whee.. sector %lu, index %d (%d) found in the buffer cache!\n", sh->sector, i, block));
					add_stripe_bh(sh, bh, i, WRITE);
					sh->new[i] = 0;
					nr++; nr_write++;
					if (sh->bh_old[i]) {
						nr_cache_overwrite++;
						nr_cache_other--;
					} else if (!operational[i]) {
						nr_failed_overwrite++;
						nr_failed_other--;
					}
				}
			}
		}
		PRINTK(("handle_stripe() -- begin writing, stripe %lu\n", sh->sector));
		/*
		 * Writing, need to update parity buffer.
		 *
		 * Compute the number of I/O requests in the "reconstruct
		 * write" and "read modify write" methods.
		 */
		if (!nr_failed_other)
			method1 = (disks - 1) - (nr_write + nr_cache_other);
		if (!nr_failed_overwrite && !parity_failed)
			method2 = nr_write - nr_cache_overwrite + (1 - parity);

		if (method1 == INT_MAX && method2 == INT_MAX)
			printk("raid5: bug: method1 == method2 == INT_MAX\n");
		PRINTK(("handle_stripe(), sector %lu, nr_write %d, method1 %d, method2 %d\n", sh->sector, nr_write, method1, method2));

		if (!method1 || !method2) {
			lock_stripe(sh);
			sh->nr_pending++;
			sh->phase = PHASE_WRITE;
			compute_parity(sh, method1 <= method2 ? RECONSTRUCT_WRITE : READ_MODIFY_WRITE);
			for (i = 0; i < disks; i++) {
				if (!operational[i] && !raid_conf->spare && !raid_conf->resync_parity)
					continue;
				if (i == sh->pd_idx || sh->bh_new[i])
					nr_writing++;
			}

			sh->nr_pending = nr_writing;
			PRINTK(("handle_stripe() %lu, writing back %d\n", sh->sector, sh->nr_pending));

			for (i = 0; i < disks; i++) {
				if (!operational[i] && !raid_conf->spare && !raid_conf->resync_parity)
					continue;
				bh = sh->bh_copy[i];
				if (i != sh->pd_idx && ((bh == NULL) ^ (sh->bh_new[i] == NULL)))
					printk("raid5: bug: bh == %p, bh_new[%d] == %p\n", bh, i, sh->bh_new[i]);
				if (i == sh->pd_idx && !bh)
					printk("raid5: bug: bh == NULL, i == pd_idx == %d\n", i);
				if (bh) {
					bh->b_state |= (1<<BH_Dirty);
					PRINTK(("making request for buffer %d\n", i));
					clear_bit(BH_Lock, &bh->b_state);
					if (!operational[i] && !raid_conf->resync_parity) {
						bh->b_rdev = raid_conf->spare->dev;
						make_request(MAJOR(raid_conf->spare->dev), WRITE, bh);
					} else
						make_request(MAJOR(raid_conf->disks[i].dev), WRITE, bh);
				}
			}
			return;
		}

		lock_stripe(sh);
		sh->nr_pending++;
		if (method1 < method2) {
			sh->write_method = RECONSTRUCT_WRITE;
			for (i = 0; i < disks; i++) {
				if (i == sh->pd_idx)
					continue;
				if (sh->bh_new[i] || sh->bh_old[i])
					continue;
				sh->bh_old[i] = raid5_kmalloc_buffer(sh, sh->size);
				raid5_build_block(sh, sh->bh_old[i], i);
				reading++;
			}
		} else {
			sh->write_method = READ_MODIFY_WRITE;
			for (i = 0; i < disks; i++) {
				if (sh->bh_old[i])
					continue;
				if (!sh->bh_new[i] && i != sh->pd_idx)
					continue;
				sh->bh_old[i] = raid5_kmalloc_buffer(sh, sh->size);
				raid5_build_block(sh, sh->bh_old[i], i);
				reading++;
			}
		}
		sh->phase = PHASE_READ_OLD;
		sh->nr_pending = reading;
		PRINTK(("handle_stripe() %lu, reading %d old buffers\n", sh->sector, sh->nr_pending));
		for (i = 0; i < disks; i++) {
			if (!sh->bh_old[i])
				continue;
			if (buffer_uptodate(sh->bh_old[i]))
				continue;
		 	clear_bit(BH_Lock, &sh->bh_old[i]->b_state);
			make_request(MAJOR(raid_conf->disks[i].dev), READ, sh->bh_old[i]);
		}
	} else {
		/*
		 * Reading
		 */
		method1 = nr_read - nr_cache_overwrite;
		lock_stripe(sh);
		sh->nr_pending++;

		PRINTK(("handle_stripe(), sector %lu, nr_read %d, nr_cache %d, method1 %d\n", sh->sector, nr_read, nr_cache, method1));
		if (!method1 || (method1 == 1 && nr_cache == disks - 1)) {
			PRINTK(("read %lu completed from cache\n", sh->sector));
			for (i = 0; i < disks; i++) {
				if (!sh->bh_new[i])
					continue;
				if (!sh->bh_old[i])
					compute_block(sh, i);
				memcpy(sh->bh_new[i]->b_data, sh->bh_old[i]->b_data, sh->size);
			}
			sh->nr_pending--;
			complete_stripe(sh);
			return;
		}
		if (nr_failed_overwrite) {
			sh->phase = PHASE_READ_OLD;
			sh->nr_pending = (disks - 1) - nr_cache;
			PRINTK(("handle_stripe() %lu, phase READ_OLD, pending %d\n", sh->sector, sh->nr_pending));
			for (i = 0; i < disks; i++) {
				if (sh->bh_old[i])
					continue;
				if (!operational[i])
					continue;
				sh->bh_old[i] = raid5_kmalloc_buffer(sh, sh->size);
				raid5_build_block(sh, sh->bh_old[i], i);
			 	clear_bit(BH_Lock, &sh->bh_old[i]->b_state);
				make_request(MAJOR(raid_conf->disks[i].dev), READ, sh->bh_old[i]);
			}
		} else {
			sh->phase = PHASE_READ;
			sh->nr_pending = nr_read - nr_cache_overwrite;
			PRINTK(("handle_stripe() %lu, phase READ, pending %d\n", sh->sector, sh->nr_pending));
			for (i = 0; i < disks; i++) {
				if (!sh->bh_new[i])
					continue;
				if (sh->bh_old[i]) {
					memcpy(sh->bh_new[i]->b_data, sh->bh_old[i]->b_data, sh->size);
					continue;
				}
				make_request(MAJOR(raid_conf->disks[i].dev), READ, sh->bh_req[i]);
			}
		}
	}
}

static int raid5_make_request (struct md_dev *mddev, int rw, struct buffer_head * bh)
{
	struct raid5_data *raid_conf = (struct raid5_data *) mddev->private;
	const unsigned int raid_disks = raid_conf->raid_disks;
	const unsigned int data_disks = raid_disks - 1;
	unsigned int  dd_idx, pd_idx;
	unsigned long new_sector;

	struct stripe_head *sh;

	if (rw == READA) rw = READ;
	if (rw == WRITEA) rw = WRITE;

	new_sector = raid5_compute_sector(bh->b_rsector, raid_disks, data_disks,
						&dd_idx, &pd_idx, raid_conf);

	PRINTK(("raid5_make_request, sector %lu\n", new_sector));
repeat:
	sh = get_stripe(raid_conf, new_sector, bh->b_size);
	if ((rw == READ && sh->cmd == STRIPE_WRITE) || (rw == WRITE && sh->cmd == STRIPE_READ)) {
		PRINTK(("raid5: lock contention, rw == %d, sh->cmd == %d\n", rw, sh->cmd));
		lock_stripe(sh);
		if (!sh->nr_pending)
			handle_stripe(sh);
		goto repeat;
	}
	sh->pd_idx = pd_idx;
	if (sh->phase != PHASE_COMPLETE && sh->phase != PHASE_BEGIN)
		PRINTK(("stripe %lu catching the bus!\n", sh->sector));
	add_stripe_bh(sh, bh, dd_idx, rw);

	md_wakeup_thread(raid_conf->thread);
	return 0;
}

static void unplug_devices(struct stripe_head *sh)
{
#if 0
	struct raid5_data *raid_conf = sh->raid_conf;
	int i;

	for (i = 0; i < raid_conf->raid_disks; i++)
		unplug_device(blk_dev + MAJOR(raid_conf->disks[i].dev));
#endif
}

/*
 * This is our raid5 kernel thread.
 *
 * We scan the hash table for stripes which can be handled now.
 * During the scan, completed stripes are saved for us by the interrupt
 * handler, so that they will not have to wait for our next wakeup.
 */
static void raid5d (void *data)
{
	struct stripe_head *sh;
	struct raid5_data *raid_conf = data;
	struct md_dev *mddev = raid_conf->mddev;
	int i, handled = 0, unplug = 0;
	unsigned long flags;

	PRINTK(("+++ raid5d active\n"));

	if (mddev->sb_dirty) {
		mddev->sb_dirty = 0;
		md_update_sb((int) (mddev - md_dev));
	}
	for (i = 0; i < NR_HASH; i++) {
repeat:
		sh = raid_conf->stripe_hashtbl[i];
		for (; sh; sh = sh->hash_next) {
			if (sh->raid_conf != raid_conf)
				continue;
			if (sh->phase == PHASE_COMPLETE)
				continue;
			if (sh->nr_pending)
				continue;
			if (sh->sector == raid_conf->next_sector) {
				raid_conf->sector_count += (sh->size >> 9);
				if (raid_conf->sector_count >= 128)
					unplug = 1;
			} else
				unplug = 1;
			if (unplug) {
				PRINTK(("unplugging devices, sector == %lu, count == %d\n", sh->sector, raid_conf->sector_count));
				unplug_devices(sh);
				unplug = 0;
				raid_conf->sector_count = 0;
			}
			raid_conf->next_sector = sh->sector + (sh->size >> 9);
			handled++;
			handle_stripe(sh);
			goto repeat;
		}
	}
	if (raid_conf) {
		PRINTK(("%d stripes handled, nr_handle %d\n", handled, atomic_read(&raid_conf->nr_handle)));
		save_flags(flags);
		cli();
		if (!atomic_read(&raid_conf->nr_handle))
			clear_bit(THREAD_WAKEUP, &raid_conf->thread->flags);
	}
	PRINTK(("--- raid5d inactive\n"));
}

#if SUPPORT_RECONSTRUCTION
/*
 * Private kernel thread for parity reconstruction after an unclean
 * shutdown. Reconstruction on spare drives in case of a failed drive
 * is done by the generic mdsyncd.
 */
static void raid5syncd (void *data)
{
	struct raid5_data *raid_conf = data;
	struct md_dev *mddev = raid_conf->mddev;

	if (!raid_conf->resync_parity)
		return;
	md_do_sync(mddev);
	raid_conf->resync_parity = 0;
}
#endif /* SUPPORT_RECONSTRUCTION */

static int __check_consistency (struct md_dev *mddev, int row)
{
	struct raid5_data *raid_conf = mddev->private;
	kdev_t dev;
	struct buffer_head *bh[MD_SB_DISKS], tmp;
	int i, rc = 0, nr = 0;

	if (raid_conf->working_disks != raid_conf->raid_disks)
		return 0;
	tmp.b_size = 4096;
	if ((tmp.b_data = (char *) get_free_page(GFP_KERNEL)) == NULL)
		return 0;
	memset(bh, 0, MD_SB_DISKS * sizeof(struct buffer_head *));
	for (i = 0; i < raid_conf->raid_disks; i++) {
		dev = raid_conf->disks[i].dev;
		set_blocksize(dev, 4096);
		if ((bh[i] = bread(dev, row / 4, 4096)) == NULL)
			break;
		nr++;
	}
	if (nr == raid_conf->raid_disks) {
		for (i = 1; i < nr; i++)
			xor_block(&tmp, bh[i]);
		if (memcmp(tmp.b_data, bh[0]->b_data, 4096))
			rc = 1;
	}
	for (i = 0; i < raid_conf->raid_disks; i++) {
		dev = raid_conf->disks[i].dev;
		if (bh[i]) {
			bforget(bh[i]);
			bh[i] = NULL;
		}
		fsync_dev(dev);
		invalidate_buffers(dev);
	}
	free_page((unsigned long) tmp.b_data);
	return rc;
}

static int check_consistency (struct md_dev *mddev)
{
	int size = mddev->sb->size;
	int row;

	for (row = 0; row < size; row += size / 8)
		if (__check_consistency(mddev, row))
			return 1;
	return 0;
}

static int raid5_run (int minor, struct md_dev *mddev)
{
	struct raid5_data *raid_conf;
	int i, j, raid_disk, memory;
	md_superblock_t *sb = mddev->sb;
	md_descriptor_t *descriptor;
	struct real_dev *realdev;

	MOD_INC_USE_COUNT;

	if (sb->level != 5 && sb->level != 4) {
		printk("raid5: %s: raid level not set to 4/5 (%d)\n", kdevname(MKDEV(MD_MAJOR, minor)), sb->level);
		MOD_DEC_USE_COUNT;
		return -EIO;
	}

	mddev->private = kmalloc (sizeof (struct raid5_data), GFP_KERNEL);
	if ((raid_conf = mddev->private) == NULL)
		goto abort;
	memset (raid_conf, 0, sizeof (*raid_conf));
	raid_conf->mddev = mddev;

	if ((raid_conf->stripe_hashtbl = (struct stripe_head **) __get_free_pages(GFP_ATOMIC, HASH_PAGES_ORDER)) == NULL)
		goto abort;
	memset(raid_conf->stripe_hashtbl, 0, HASH_PAGES * PAGE_SIZE);

	init_waitqueue(&raid_conf->wait_for_stripe);
	PRINTK(("raid5_run(%d) called.\n", minor));

  	for (i = 0; i < mddev->nb_dev; i++) {
  		realdev = &mddev->devices[i];
		if (!realdev->sb) {
			printk(KERN_ERR "raid5: disabled device %s (couldn't access raid superblock)\n", kdevname(realdev->dev));
			continue;
		}

		/*
		 * This is important -- we are using the descriptor on
		 * the disk only to get a pointer to the descriptor on
		 * the main superblock, which might be more recent.
		 */
		descriptor = &sb->disks[realdev->sb->descriptor.number];
		if (descriptor->state & (1 << MD_FAULTY_DEVICE)) {
			printk(KERN_ERR "raid5: disabled device %s (errors detected)\n", kdevname(realdev->dev));
			continue;
		}
		if (descriptor->state & (1 << MD_ACTIVE_DEVICE)) {
			if (!(descriptor->state & (1 << MD_SYNC_DEVICE))) {
				printk(KERN_ERR "raid5: disabled device %s (not in sync)\n", kdevname(realdev->dev));
				continue;
			}
			raid_disk = descriptor->raid_disk;
			if (descriptor->number > sb->nr_disks || raid_disk > sb->raid_disks) {
				printk(KERN_ERR "raid5: disabled device %s (inconsistent descriptor)\n", kdevname(realdev->dev));
				continue;
			}
			if (raid_conf->disks[raid_disk].operational) {
				printk(KERN_ERR "raid5: disabled device %s (device %d already operational)\n", kdevname(realdev->dev), raid_disk);
				continue;
			}
			printk(KERN_INFO "raid5: device %s operational as raid disk %d\n", kdevname(realdev->dev), raid_disk);
	
			raid_conf->disks[raid_disk].number = descriptor->number;
			raid_conf->disks[raid_disk].raid_disk = raid_disk;
			raid_conf->disks[raid_disk].dev = mddev->devices[i].dev;
			raid_conf->disks[raid_disk].operational = 1;

			raid_conf->working_disks++;
		} else {
			/*
			 * Must be a spare disk ..
			 */
			printk(KERN_INFO "raid5: spare disk %s\n", kdevname(realdev->dev));
			raid_disk = descriptor->raid_disk;
			raid_conf->disks[raid_disk].number = descriptor->number;
			raid_conf->disks[raid_disk].raid_disk = raid_disk;
			raid_conf->disks[raid_disk].dev = mddev->devices [i].dev;

			raid_conf->disks[raid_disk].operational = 0;
			raid_conf->disks[raid_disk].write_only = 0;
			raid_conf->disks[raid_disk].spare = 1;
		}
	}
	raid_conf->raid_disks = sb->raid_disks;
	raid_conf->failed_disks = raid_conf->raid_disks - raid_conf->working_disks;
	raid_conf->mddev = mddev;
	raid_conf->chunk_size = sb->chunk_size;
	raid_conf->level = sb->level;
	raid_conf->algorithm = sb->parity_algorithm;
	raid_conf->max_nr_stripes = NR_STRIPES;

	if (raid_conf->working_disks != sb->raid_disks && sb->state != (1 << MD_SB_CLEAN)) {
		printk(KERN_ALERT "raid5: raid set %s not clean and not all disks are operational -- run ckraid\n", kdevname(MKDEV(MD_MAJOR, minor)));
		goto abort;
	}
	if (!raid_conf->chunk_size || raid_conf->chunk_size % 4) {
		printk(KERN_ERR "raid5: invalid chunk size %d for %s\n", raid_conf->chunk_size, kdevname(MKDEV(MD_MAJOR, minor)));
		goto abort;
	}
	if (raid_conf->algorithm > ALGORITHM_RIGHT_SYMMETRIC) {
		printk(KERN_ERR "raid5: unsupported parity algorithm %d for %s\n", raid_conf->algorithm, kdevname(MKDEV(MD_MAJOR, minor)));
		goto abort;
	}
	if (raid_conf->failed_disks > 1) {
		printk(KERN_ERR "raid5: not enough operational devices for %s (%d/%d failed)\n", kdevname(MKDEV(MD_MAJOR, minor)), raid_conf->failed_disks, raid_conf->raid_disks);
		goto abort;
	}

	if ((sb->state & (1 << MD_SB_CLEAN)) && check_consistency(mddev)) {
		printk(KERN_ERR "raid5: detected raid-5 xor inconsistenty -- run ckraid\n");
		sb->state |= 1 << MD_SB_ERRORS;
		goto abort;
	}

	if ((raid_conf->thread = md_register_thread(raid5d, raid_conf)) == NULL) {
		printk(KERN_ERR "raid5: couldn't allocate thread for %s\n", kdevname(MKDEV(MD_MAJOR, minor)));
		goto abort;
	}

#if SUPPORT_RECONSTRUCTION
	if ((raid_conf->resync_thread = md_register_thread(raid5syncd, raid_conf)) == NULL) {
		printk(KERN_ERR "raid5: couldn't allocate thread for %s\n", kdevname(MKDEV(MD_MAJOR, minor)));
		goto abort;
	}
#endif /* SUPPORT_RECONSTRUCTION */

	memory = raid_conf->max_nr_stripes * (sizeof(struct stripe_head) +
		 raid_conf->raid_disks * (sizeof(struct buffer_head) +
		 2 * (sizeof(struct buffer_head) + PAGE_SIZE))) / 1024;
	if (grow_stripes(raid_conf, raid_conf->max_nr_stripes, GFP_KERNEL)) {
		printk(KERN_ERR "raid5: couldn't allocate %dkB for buffers\n", memory);
		shrink_stripes(raid_conf, raid_conf->max_nr_stripes);
		goto abort;
	} else
		printk(KERN_INFO "raid5: allocated %dkB for %s\n", memory, kdevname(MKDEV(MD_MAJOR, minor)));

	/*
	 * Regenerate the "device is in sync with the raid set" bit for
	 * each device.
	 */
	for (i = 0; i < sb->nr_disks ; i++) {
		sb->disks[i].state &= ~(1 << MD_SYNC_DEVICE);
		for (j = 0; j < sb->raid_disks; j++) {
			if (!raid_conf->disks[j].operational)
				continue;
			if (sb->disks[i].number == raid_conf->disks[j].number)
				sb->disks[i].state |= 1 << MD_SYNC_DEVICE;
		}
	}
	sb->active_disks = raid_conf->working_disks;

	if (sb->active_disks == sb->raid_disks)
		printk("raid5: raid level %d set %s active with %d out of %d devices, algorithm %d\n", raid_conf->level, kdevname(MKDEV(MD_MAJOR, minor)), sb->active_disks, sb->raid_disks, raid_conf->algorithm);
	else
		printk(KERN_ALERT "raid5: raid level %d set %s active with %d out of %d devices, algorithm %d\n", raid_conf->level, kdevname(MKDEV(MD_MAJOR, minor)), sb->active_disks, sb->raid_disks, raid_conf->algorithm);

	if ((sb->state & (1 << MD_SB_CLEAN)) == 0) {
		printk("raid5: raid set %s not clean; re-constructing parity\n", kdevname(MKDEV(MD_MAJOR, minor)));
		raid_conf->resync_parity = 1;
#if SUPPORT_RECONSTRUCTION
		md_wakeup_thread(raid_conf->resync_thread);
#endif /* SUPPORT_RECONSTRUCTION */
	}

	/* Ok, everything is just fine now */
	return (0);
abort:
	if (raid_conf) {
		if (raid_conf->stripe_hashtbl)
			free_pages((unsigned long) raid_conf->stripe_hashtbl, HASH_PAGES_ORDER);
		kfree(raid_conf);
	}
	mddev->private = NULL;
	printk(KERN_ALERT "raid5: failed to run raid set %s\n", kdevname(MKDEV(MD_MAJOR, minor)));
	MOD_DEC_USE_COUNT;
	return -EIO;
}

static int raid5_stop (int minor, struct md_dev *mddev)
{
	struct raid5_data *raid_conf = (struct raid5_data *) mddev->private;

	shrink_stripe_cache(raid_conf, raid_conf->max_nr_stripes);
	shrink_stripes(raid_conf, raid_conf->max_nr_stripes);
	md_unregister_thread(raid_conf->thread);
#if SUPPORT_RECONSTRUCTION
	md_unregister_thread(raid_conf->resync_thread);
#endif /* SUPPORT_RECONSTRUCTION */
	free_pages((unsigned long) raid_conf->stripe_hashtbl, HASH_PAGES_ORDER);
	kfree(raid_conf);
	mddev->private = NULL;
	MOD_DEC_USE_COUNT;
	return 0;
}

static int raid5_status (char *page, int minor, struct md_dev *mddev)
{
	struct raid5_data *raid_conf = (struct raid5_data *) mddev->private;
	md_superblock_t *sb = mddev->sb;
	int sz = 0, i;

	sz += sprintf (page+sz, " level %d, %dk chunk, algorithm %d", sb->level, sb->chunk_size >> 10, sb->parity_algorithm);
	sz += sprintf (page+sz, " [%d/%d] [", raid_conf->raid_disks, raid_conf->working_disks);
	for (i = 0; i < raid_conf->raid_disks; i++)
		sz += sprintf (page+sz, "%s", raid_conf->disks[i].operational ? "U" : "_");
	sz += sprintf (page+sz, "]");
	return sz;
}

static int raid5_mark_spare(struct md_dev *mddev, md_descriptor_t *spare, int state)
{
	int i = 0, failed_disk = -1;
	struct raid5_data *raid_conf = mddev->private;
	struct disk_info *disk = raid_conf->disks;
	unsigned long flags;
	md_superblock_t *sb = mddev->sb;
	md_descriptor_t *descriptor;

	for (i = 0; i < MD_SB_DISKS; i++, disk++) {
		if (disk->spare && disk->number == spare->number)
			goto found;
	}
	return 1;
found:
	for (i = 0, disk = raid_conf->disks; i < raid_conf->raid_disks; i++, disk++)
		if (!disk->operational)
			failed_disk = i;
	if (failed_disk == -1)
		return 1;
	save_flags(flags);
	cli();
	switch (state) {
		case SPARE_WRITE:
			disk->operational = 1;
			disk->write_only = 1;
			raid_conf->spare = disk;
			break;
		case SPARE_INACTIVE:
			disk->operational = 0;
			disk->write_only = 0;
			raid_conf->spare = NULL;
			break;
		case SPARE_ACTIVE:
			disk->spare = 0;
			disk->write_only = 0;

			descriptor = &sb->disks[raid_conf->disks[failed_disk].number];
			i = spare->raid_disk;
			disk->raid_disk = spare->raid_disk = descriptor->raid_disk;
			if (disk->raid_disk != failed_disk)
				printk("raid5: disk->raid_disk != failed_disk");
			descriptor->raid_disk = i;

			raid_conf->spare = NULL;
			raid_conf->working_disks++;
			raid_conf->failed_disks--;
			raid_conf->disks[failed_disk] = *disk;
			break;
		default:
			printk("raid5_mark_spare: bug: state == %d\n", state);
			restore_flags(flags);
			return 1;
	}
	restore_flags(flags);
	return 0;
}

static struct md_personality raid5_personality=
{
	"raid5",
	raid5_map,
	raid5_make_request,
	raid5_end_request,
	raid5_run,
	raid5_stop,
	raid5_status,
	NULL,			/* no ioctls */
	0,
	raid5_error,
	/* raid5_hot_add_disk, */ NULL,
	/* raid1_hot_remove_drive */ NULL,
	raid5_mark_spare
};

int raid5_init (void)
{
	return register_md_personality (RAID5, &raid5_personality);
}

#ifdef MODULE
int init_module (void)
{
	return raid5_init();
}

void cleanup_module (void)
{
	unregister_md_personality (RAID5);
}
#endif