/*
   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/blkdev.h>
#include <linux/raid/md_u.h>
#include <linux/seq_file.h>
#include <linux/module.h>
#include <linux/slab.h>
#include "md.h"
#include "linear.h"

/*
 * find which device holds a particular offset 
 */
static inline struct dev_info *which_dev(struct mddev *mddev, sector_t sector)
{
        int lo, mid, hi;
        struct linear_conf *conf;

        lo = 0;
        hi = mddev->raid_disks - 1;
        conf = rcu_dereference(mddev->private);

        /*
         * Binary Search
         */

        while (hi > lo) {

                mid = (hi + lo) / 2;
                if (sector < conf->disks[mid].end_sector)
                        hi = mid;
                else
                        lo = mid + 1;
        }

        return conf->disks + lo;
}

/**
 *      linear_mergeable_bvec -- tell bio layer if two requests can be merged
 *      @q: request queue
 *      @bvm: properties of new bio
 *      @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 bvec_merge_data *bvm,
                                 struct bio_vec *biovec)
{
        struct mddev *mddev = q->queuedata;
        struct dev_info *dev0;
        unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
        sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
        int maxbytes = biovec->bv_len;
        struct request_queue *subq;

        rcu_read_lock();
        dev0 = which_dev(mddev, sector);
        maxsectors = dev0->end_sector - sector;
        subq = bdev_get_queue(dev0->rdev->bdev);
        if (subq->merge_bvec_fn) {
                bvm->bi_bdev = dev0->rdev->bdev;
                bvm->bi_sector -= dev0->end_sector - dev0->rdev->sectors;
                maxbytes = min(maxbytes, subq->merge_bvec_fn(subq, bvm,
                                                             biovec));
        }
        rcu_read_unlock();

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

        if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
                return maxbytes;

        if (maxsectors > (maxbytes >> 9))
                return maxbytes;
        else
                return maxsectors << 9;
}

static int linear_congested(void *data, int bits)
{
        struct mddev *mddev = data;
        struct linear_conf *conf;
        int i, ret = 0;

        if (mddev_congested(mddev, bits))
                return 1;

        rcu_read_lock();
        conf = rcu_dereference(mddev->private);

        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);
        }

        rcu_read_unlock();
        return ret;
}

static sector_t linear_size(struct mddev *mddev, sector_t sectors, int raid_disks)
{
        struct linear_conf *conf;
        sector_t array_sectors;

        rcu_read_lock();
        conf = rcu_dereference(mddev->private);
        WARN_ONCE(sectors || raid_disks,
                  "%s does not support generic reshape\n", __func__);
        array_sectors = conf->array_sectors;
        rcu_read_unlock();

        return array_sectors;
}

static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
{
        struct linear_conf *conf;
        struct md_rdev *rdev;
        int i, cnt;
        bool discard_supported = false;

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

        cnt = 0;
        conf->array_sectors = 0;

        rdev_for_each(rdev, mddev) {
                int j = rdev->raid_disk;
                struct dev_info *disk = conf->disks + j;
                sector_t sectors;

                if (j < 0 || j >= raid_disks || disk->rdev) {
                        printk(KERN_ERR "md/linear:%s: disk numbering problem. Aborting!\n",
                               mdname(mddev));
                        goto out;
                }

                disk->rdev = rdev;
                if (mddev->chunk_sectors) {
                        sectors = rdev->sectors;
                        sector_div(sectors, mddev->chunk_sectors);
                        rdev->sectors = sectors * mddev->chunk_sectors;
                }

                disk_stack_limits(mddev->gendisk, rdev->bdev,
                                  rdev->data_offset << 9);

                conf->array_sectors += rdev->sectors;
                cnt++;

                if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
                        discard_supported = true;
        }
        if (cnt != raid_disks) {
                printk(KERN_ERR "md/linear:%s: not enough drives present. Aborting!\n",
                       mdname(mddev));
                goto out;
        }

        if (!discard_supported)
                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
        else
                queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);

        /*
         * Here we calculate the device offsets.
         */
        conf->disks[0].end_sector = conf->disks[0].rdev->sectors;

        for (i = 1; i < raid_disks; i++)
                conf->disks[i].end_sector =
                        conf->disks[i-1].end_sector +
                        conf->disks[i].rdev->sectors;

        return conf;

out:
        kfree(conf);
        return NULL;
}

static int linear_run (struct mddev *mddev)
{
        struct linear_conf *conf;
        int ret;

        if (md_check_no_bitmap(mddev))
                return -EINVAL;
        conf = linear_conf(mddev, mddev->raid_disks);

        if (!conf)
                return 1;
        mddev->private = conf;
        md_set_array_sectors(mddev, linear_size(mddev, 0, 0));

        blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
        mddev->queue->backing_dev_info.congested_fn = linear_congested;
        mddev->queue->backing_dev_info.congested_data = mddev;

        ret =  md_integrity_register(mddev);
        if (ret) {
                kfree(conf);
                mddev->private = NULL;
        }
        return ret;
}

static int linear_add(struct mddev *mddev, struct md_rdev *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.
         */
        struct linear_conf *newconf, *oldconf;

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

        rdev->raid_disk = rdev->saved_raid_disk;
        rdev->saved_raid_disk = -1;

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

        if (!newconf)
                return -ENOMEM;

        oldconf = rcu_dereference_protected(mddev->private,
                                            lockdep_is_held(
                                                    &mddev->reconfig_mutex));
        mddev->raid_disks++;
        rcu_assign_pointer(mddev->private, newconf);
        md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
        set_capacity(mddev->gendisk, mddev->array_sectors);
        revalidate_disk(mddev->gendisk);
        kfree_rcu(oldconf, rcu);
        return 0;
}

static int linear_stop (struct mddev *mddev)
{
        struct linear_conf *conf =
                rcu_dereference_protected(mddev->private,
                                          lockdep_is_held(
                                                  &mddev->reconfig_mutex));

        /*
         * We do not require rcu protection here since
         * we hold reconfig_mutex for both linear_add and
         * linear_stop, so they cannot race.
         * We should make sure any old 'conf's are properly
         * freed though.
         */
        rcu_barrier();
        blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
        kfree(conf);
        mddev->private = NULL;

        return 0;
}

static void linear_make_request(struct mddev *mddev, struct bio *bio)
{
        struct dev_info *tmp_dev;
        sector_t start_sector;

        if (unlikely(bio->bi_rw & REQ_FLUSH)) {
                md_flush_request(mddev, bio);
                return;
        }

        rcu_read_lock();
        tmp_dev = which_dev(mddev, bio->bi_sector);
        start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;


        if (unlikely(bio->bi_sector >= (tmp_dev->end_sector)
                     || (bio->bi_sector < start_sector))) {
                char b[BDEVNAME_SIZE];

                printk(KERN_ERR
                       "md/linear:%s: make_request: Sector %llu out of bounds on "
                       "dev %s: %llu sectors, offset %llu\n",
                       mdname(mddev),
                       (unsigned long long)bio->bi_sector,
                       bdevname(tmp_dev->rdev->bdev, b),
                       (unsigned long long)tmp_dev->rdev->sectors,
                       (unsigned long long)start_sector);
                rcu_read_unlock();
                bio_io_error(bio);
                return;
        }
        if (unlikely(bio_end_sector(bio) > tmp_dev->end_sector)) {
                /* This bio crosses a device boundary, so we have to
                 * split it.
                 */
                struct bio_pair *bp;
                sector_t end_sector = tmp_dev->end_sector;

                rcu_read_unlock();

                bp = bio_split(bio, end_sector - bio->bi_sector);

                linear_make_request(mddev, &bp->bio1);
                linear_make_request(mddev, &bp->bio2);
                bio_pair_release(bp);
                return;
        }
                    
        bio->bi_bdev = tmp_dev->rdev->bdev;
        bio->bi_sector = bio->bi_sector - start_sector
                + tmp_dev->rdev->data_offset;
        rcu_read_unlock();

        if (unlikely((bio->bi_rw & REQ_DISCARD) &&
                     !blk_queue_discard(bdev_get_queue(bio->bi_bdev)))) {
                /* Just ignore it */
                bio_endio(bio, 0);
                return;
        }

        generic_make_request(bio);
}

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

        seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
}


static struct md_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,
        .size           = linear_size,
};

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_DESCRIPTION("Linear device concatenation personality for MD");
MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
MODULE_ALIAS("md-linear");
MODULE_ALIAS("md-level--1");