// SPDX-License-Identifier: GPL-2.0-or-later
/*
   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.

*/

#include <linux/blkdev.h>
#include <linux/raid/md_u.h>
#include <linux/seq_file.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <trace/events/block.h>
#include "md.h"
#include "md-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 = 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 sector_t linear_size(struct mddev *mddev, sector_t sectors, int raid_disks)
{
        struct linear_conf *conf;
        sector_t array_sectors;

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

        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(struct_size(conf, disks, raid_disks), 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) {
                        pr_warn("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) {
                pr_warn("md/linear:%s: not enough drives present. Aborting!\n",
                        mdname(mddev));
                goto out;
        }

        if (!discard_supported)
                blk_queue_flag_clear(QUEUE_FLAG_DISCARD, mddev->queue);
        else
                blk_queue_flag_set(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;

        /*
         * conf->raid_disks is copy of mddev->raid_disks. The reason to
         * keep a copy of mddev->raid_disks in struct linear_conf is,
         * mddev->raid_disks may not be consistent with pointers number of
         * conf->disks[] when it is updated in linear_add() and used to
         * iterate old conf->disks[] earray in linear_congested().
         * Here conf->raid_disks is always consitent with number of
         * pointers in conf->disks[] array, and mddev->private is updated
         * with rcu_assign_pointer() in linear_addr(), such race can be
         * avoided.
         */
        conf->raid_disks = raid_disks;

        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));

        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;

        /* newconf->raid_disks already keeps a copy of * the increased
         * value of mddev->raid_disks, WARN_ONCE() is just used to make
         * sure of this. It is possible that oldconf is still referenced
         * in linear_congested(), therefore kfree_rcu() is used to free
         * oldconf until no one uses it anymore.
         */
        mddev_suspend(mddev);
        oldconf = rcu_dereference_protected(mddev->private,
                        lockdep_is_held(&mddev->reconfig_mutex));
        mddev->raid_disks++;
        WARN_ONCE(mddev->raid_disks != newconf->raid_disks,
                "copied raid_disks doesn't match 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);
        mddev_resume(mddev);
        revalidate_disk_size(mddev->gendisk, true);
        kfree_rcu(oldconf, rcu);
        return 0;
}

static void linear_free(struct mddev *mddev, void *priv)
{
        struct linear_conf *conf = priv;

        kfree(conf);
}

static bool linear_make_request(struct mddev *mddev, struct bio *bio)
{
        char b[BDEVNAME_SIZE];
        struct dev_info *tmp_dev;
        sector_t start_sector, end_sector, data_offset;
        sector_t bio_sector = bio->bi_iter.bi_sector;

        if (unlikely(bio->bi_opf & REQ_PREFLUSH)
            && md_flush_request(mddev, bio))
                return true;

        tmp_dev = which_dev(mddev, bio_sector);
        start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
        end_sector = tmp_dev->end_sector;
        data_offset = tmp_dev->rdev->data_offset;

        if (unlikely(bio_sector >= end_sector ||
                     bio_sector < start_sector))
                goto out_of_bounds;

        if (unlikely(is_mddev_broken(tmp_dev->rdev, "linear"))) {
                bio_io_error(bio);
                return true;
        }

        if (unlikely(bio_end_sector(bio) > end_sector)) {
                /* This bio crosses a device boundary, so we have to split it */
                struct bio *split = bio_split(bio, end_sector - bio_sector,
                                              GFP_NOIO, &mddev->bio_set);
                bio_chain(split, bio);
                submit_bio_noacct(bio);
                bio = split;
        }

        bio_set_dev(bio, tmp_dev->rdev->bdev);
        bio->bi_iter.bi_sector = bio->bi_iter.bi_sector -
                start_sector + data_offset;

        if (unlikely((bio_op(bio) == REQ_OP_DISCARD) &&
                     !blk_queue_discard(bio->bi_disk->queue))) {
                /* Just ignore it */
                bio_endio(bio);
        } else {
                if (mddev->gendisk)
                        trace_block_bio_remap(bio->bi_disk->queue,
                                              bio, disk_devt(mddev->gendisk),
                                              bio_sector);
                mddev_check_writesame(mddev, bio);
                mddev_check_write_zeroes(mddev, bio);
                submit_bio_noacct(bio);
        }
        return true;

out_of_bounds:
        pr_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_iter.bi_sector,
               bdevname(tmp_dev->rdev->bdev, b),
               (unsigned long long)tmp_dev->rdev->sectors,
               (unsigned long long)start_sector);
        bio_io_error(bio);
        return true;
}

static void linear_status (struct seq_file *seq, struct mddev *mddev)
{
        seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
}

static void linear_quiesce(struct mddev *mddev, int state)
{
}

static struct md_personality linear_personality =
{
        .name           = "linear",
        .level          = LEVEL_LINEAR,
        .owner          = THIS_MODULE,
        .make_request   = linear_make_request,
        .run            = linear_run,
        .free           = linear_free,
        .status         = linear_status,
        .hot_add_disk   = linear_add,
        .size           = linear_size,
        .quiesce        = linear_quiesce,
};

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");