linear.c

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/*
   linear.c : Multiple Devices driver for Linux
          Copyright (C) 1994-96 Marc ZYNGIER
          <[email protected]> or
          <[email protected]>

   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;
}

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->bi_sector + (bio->bi_size >> 9) >
             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");