linear.c

/*
   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)
{
	char b[BDEVNAME_SIZE];
	struct dev_info *tmp_dev;
	struct bio *split;
	sector_t start_sector, end_sector, data_offset;

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

	do {
		rcu_read_lock();

		tmp_dev = which_dev(mddev, bio->bi_iter.bi_sector);
		start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
		end_sector = tmp_dev->end_sector;
		data_offset = tmp_dev->rdev->data_offset;
		bio->bi_bdev = tmp_dev->rdev->bdev;

		rcu_read_unlock();

		if (unlikely(bio->bi_iter.bi_sector >= end_sector ||
			     bio->bi_iter.bi_sector < start_sector))
			goto out_of_bounds;

		if (unlikely(bio_end_sector(bio) > end_sector)) {
			/* This bio crosses a device boundary, so we have to
			 * split it.
			 */
			split = bio_split(bio, end_sector -
					  bio->bi_iter.bi_sector,
					  GFP_NOIO, fs_bio_set);
			bio_chain(split, bio);
		} else {
			split = bio;
		}

		split->bi_iter.bi_sector = split->bi_iter.bi_sector -
			start_sector + data_offset;

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

out_of_bounds:
	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_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);
}

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");