/*
   linear.c : Multiple Devices driver for Linux
              Copyright (C) 1994-96 Marc ZYNGIER
              <zyngier@ufr-info-p7.ibp.fr> or
              <maz@gloups.fdn.fr>

   Linear mode 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/raid/md.h>
#include <linux/slab.h>
#include <linux/raid/linear.h>

#define MAJOR_NR MD_MAJOR
#define MD_DRIVER
#define MD_PERSONALITY

/*
 * find which device holds a particular offset 
 */
static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
{
        dev_info_t *hash;
        linear_conf_t *conf = mddev_to_conf(mddev);
        sector_t block = sector >> 1;

        /*
         * sector_div(a,b) returns the remainer and sets a to a/b
         */
        block >>= conf->preshift;
        (void)sector_div(block, conf->hash_spacing);
        hash = conf->hash_table[block];

        while ((sector>>1) >= (hash->size + hash->offset))
                hash++;
        return hash;
}

/**
 *      linear_mergeable_bvec -- tell bio layer if two requests can be merged
 *      @q: request queue
 *      @bio: the buffer head that's been built up so far
 *      @biovec: the request that could be merged to it.
 *
 *      Return amount of bytes we can take at this offset
 */
static int linear_mergeable_bvec(struct request_queue *q, struct bio *bio, struct bio_vec *biovec)
{
        mddev_t *mddev = q->queuedata;
        dev_info_t *dev0;
        unsigned long maxsectors, bio_sectors = bio->bi_size >> 9;
        sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);

        dev0 = which_dev(mddev, sector);
        maxsectors = (dev0->size << 1) - (sector - (dev0->offset<<1));

        if (maxsectors < bio_sectors)
                maxsectors = 0;
        else
                maxsectors -= bio_sectors;

        if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
                return biovec->bv_len;
        /* The bytes available at this offset could be really big,
         * so we cap at 2^31 to avoid overflow */
        if (maxsectors > (1 << (31-9)))
                return 1<<31;
        return maxsectors << 9;
}

static void linear_unplug(struct request_queue *q)
{
        mddev_t *mddev = q->queuedata;
        linear_conf_t *conf = mddev_to_conf(mddev);
        int i;

        for (i=0; i < mddev->raid_disks; i++) {
                struct request_queue *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
                blk_unplug(r_queue);
        }
}

static int linear_congested(void *data, int bits)
{
        mddev_t *mddev = data;
        linear_conf_t *conf = mddev_to_conf(mddev);
        int i, ret = 0;

        for (i = 0; i < mddev->raid_disks && !ret ; i++) {
                struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
                ret |= bdi_congested(&q->backing_dev_info, bits);
        }
        return ret;
}

static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
{
        linear_conf_t *conf;
        dev_info_t **table;
        mdk_rdev_t *rdev;
        int i, nb_zone, cnt;
        sector_t min_spacing;
        sector_t curr_offset;
        struct list_head *tmp;

        conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(dev_info_t),
                        GFP_KERNEL);
        if (!conf)
                return NULL;

        cnt = 0;
        conf->array_size = 0;

        ITERATE_RDEV(mddev,rdev,tmp) {
                int j = rdev->raid_disk;
                dev_info_t *disk = conf->disks + j;

                if (j < 0 || j > raid_disks || disk->rdev) {
                        printk("linear: disk numbering problem. Aborting!\n");
                        goto out;
                }

                disk->rdev = rdev;

                blk_queue_stack_limits(mddev->queue,
                                       rdev->bdev->bd_disk->queue);
                /* as we don't honour merge_bvec_fn, we must never risk
                 * violating it, so limit ->max_sector to one PAGE, as
                 * a one page request is never in violation.
                 */
                if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
                    mddev->queue->max_sectors > (PAGE_SIZE>>9))
                        blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

                disk->size = rdev->size;
                conf->array_size += rdev->size;

                cnt++;
        }
        if (cnt != raid_disks) {
                printk("linear: not enough drives present. Aborting!\n");
                goto out;
        }

        min_spacing = conf->array_size;
        sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));

        /* min_spacing is the minimum spacing that will fit the hash
         * table in one PAGE.  This may be much smaller than needed.
         * We find the smallest non-terminal set of consecutive devices
         * that is larger than min_spacing as use the size of that as
         * the actual spacing
         */
        conf->hash_spacing = conf->array_size;
        for (i=0; i < cnt-1 ; i++) {
                sector_t sz = 0;
                int j;
                for (j = i; j < cnt - 1 && sz < min_spacing; j++)
                        sz += conf->disks[j].size;
                if (sz >= min_spacing && sz < conf->hash_spacing)
                        conf->hash_spacing = sz;
        }

        /* hash_spacing may be too large for sector_div to work with,
         * so we might need to pre-shift
         */
        conf->preshift = 0;
        if (sizeof(sector_t) > sizeof(u32)) {
                sector_t space = conf->hash_spacing;
                while (space > (sector_t)(~(u32)0)) {
                        space >>= 1;
                        conf->preshift++;
                }
        }
        /*
         * This code was restructured to work around a gcc-2.95.3 internal
         * compiler error.  Alter it with care.
         */
        {
                sector_t sz;
                unsigned round;
                unsigned long base;

                sz = conf->array_size >> conf->preshift;
                sz += 1; /* force round-up */
                base = conf->hash_spacing >> conf->preshift;
                round = sector_div(sz, base);
                nb_zone = sz + (round ? 1 : 0);
        }
        BUG_ON(nb_zone > PAGE_SIZE / sizeof(struct dev_info *));

        conf->hash_table = kmalloc (sizeof (struct dev_info *) * nb_zone,
                                        GFP_KERNEL);
        if (!conf->hash_table)
                goto out;

        /*
         * Here we generate the linear hash table
         * First calculate the device offsets.
         */
        conf->disks[0].offset = 0;
        for (i = 1; i < raid_disks; i++)
                conf->disks[i].offset =
                        conf->disks[i-1].offset +
                        conf->disks[i-1].size;

        table = conf->hash_table;
        curr_offset = 0;
        i = 0;
        for (curr_offset = 0;
             curr_offset < conf->array_size;
             curr_offset += conf->hash_spacing) {

                while (i < raid_disks-1 &&
                       curr_offset >= conf->disks[i+1].offset)
                        i++;

                *table ++ = conf->disks + i;
        }

        if (conf->preshift) {
                conf->hash_spacing >>= conf->preshift;
                /* round hash_spacing up so that when we divide by it,
                 * we err on the side of "too-low", which is safest.
                 */
                conf->hash_spacing++;
        }

        BUG_ON(table - conf->hash_table > nb_zone);

        return conf;

out:
        kfree(conf);
        return NULL;
}

static int linear_run (mddev_t *mddev)
{
        linear_conf_t *conf;

        conf = linear_conf(mddev, mddev->raid_disks);

        if (!conf)
                return 1;
        mddev->private = conf;
        mddev->array_size = conf->array_size;

        blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
        mddev->queue->unplug_fn = linear_unplug;
        mddev->queue->backing_dev_info.congested_fn = linear_congested;
        mddev->queue->backing_dev_info.congested_data = mddev;
        return 0;
}

static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
{
        /* Adding a drive to a linear array allows the array to grow.
         * It is permitted if the new drive has a matching superblock
         * already on it, with raid_disk equal to raid_disks.
         * It is achieved by creating a new linear_private_data structure
         * and swapping it in in-place of the current one.
         * The current one is never freed until the array is stopped.
         * This avoids races.
         */
        linear_conf_t *newconf;

        if (rdev->saved_raid_disk != mddev->raid_disks)
                return -EINVAL;

        rdev->raid_disk = rdev->saved_raid_disk;

        newconf = linear_conf(mddev,mddev->raid_disks+1);

        if (!newconf)
                return -ENOMEM;

        newconf->prev = mddev_to_conf(mddev);
        mddev->private = newconf;
        mddev->raid_disks++;
        mddev->array_size = newconf->array_size;
        set_capacity(mddev->gendisk, mddev->array_size << 1);
        return 0;
}

static int linear_stop (mddev_t *mddev)
{
        linear_conf_t *conf = mddev_to_conf(mddev);
  
        blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
        do {
                linear_conf_t *t = conf->prev;
                kfree(conf->hash_table);
                kfree(conf);
                conf = t;
        } while (conf);

        return 0;
}

static int linear_make_request (struct request_queue *q, struct bio *bio)
{
        const int rw = bio_data_dir(bio);
        mddev_t *mddev = q->queuedata;
        dev_info_t *tmp_dev;
        sector_t block;

        if (unlikely(bio_barrier(bio))) {
                bio_endio(bio, -EOPNOTSUPP);
                return 0;
        }

        disk_stat_inc(mddev->gendisk, ios[rw]);
        disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));

        tmp_dev = which_dev(mddev, bio->bi_sector);
        block = bio->bi_sector >> 1;
    
        if (unlikely(block >= (tmp_dev->size + tmp_dev->offset)
                     || block < tmp_dev->offset)) {
                char b[BDEVNAME_SIZE];

                printk("linear_make_request: Block %llu out of bounds on "
                        "dev %s size %llu offset %llu\n",
                        (unsigned long long)block,
                        bdevname(tmp_dev->rdev->bdev, b),
                        (unsigned long long)tmp_dev->size,
                        (unsigned long long)tmp_dev->offset);
                bio_io_error(bio);
                return 0;
        }
        if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
                     (tmp_dev->offset + tmp_dev->size)<<1)) {
                /* This bio crosses a device boundary, so we have to
                 * split it.
                 */
                struct bio_pair *bp;
                bp = bio_split(bio, bio_split_pool,
                               ((tmp_dev->offset + tmp_dev->size)<<1) - bio->bi_sector);
                if (linear_make_request(q, &bp->bio1))
                        generic_make_request(&bp->bio1);
                if (linear_make_request(q, &bp->bio2))
                        generic_make_request(&bp->bio2);
                bio_pair_release(bp);
                return 0;
        }
                    
        bio->bi_bdev = tmp_dev->rdev->bdev;
        bio->bi_sector = bio->bi_sector - (tmp_dev->offset << 1) + tmp_dev->rdev->data_offset;

        return 1;
}

static void linear_status (struct seq_file *seq, mddev_t *mddev)
{

#undef MD_DEBUG
#ifdef MD_DEBUG
        int j;
        linear_conf_t *conf = mddev_to_conf(mddev);
        sector_t s = 0;
  
        seq_printf(seq, "      ");
        for (j = 0; j < mddev->raid_disks; j++)
        {
                char b[BDEVNAME_SIZE];
                s += conf->smallest_size;
                seq_printf(seq, "[%s",
                           bdevname(conf->hash_table[j][0].rdev->bdev,b));

                while (s > conf->hash_table[j][0].offset +
                           conf->hash_table[j][0].size)
                        seq_printf(seq, "/%s] ",
                                   bdevname(conf->hash_table[j][1].rdev->bdev,b));
                else
                        seq_printf(seq, "] ");
        }
        seq_printf(seq, "\n");
#endif
        seq_printf(seq, " %dk rounding", mddev->chunk_size/1024);
}


static struct mdk_personality linear_personality =
{
        .name           = "linear",
        .level          = LEVEL_LINEAR,
        .owner          = THIS_MODULE,
        .make_request   = linear_make_request,
        .run            = linear_run,
        .stop           = linear_stop,
        .status         = linear_status,
        .hot_add_disk   = linear_add,
};

static int __init linear_init (void)
{
        return register_md_personality (&linear_personality);
}

static void linear_exit (void)
{
        unregister_md_personality (&linear_personality);
}


module_init(linear_init);
module_exit(linear_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
MODULE_ALIAS("md-linear");
MODULE_ALIAS("md-level--1");