[PATCH] md: break out of a loop that doesn't need to run to completion

[net-next-2.6.git] / drivers / md / raid0.c

/*
   raid0.c : Multiple Devices driver for Linux
             Copyright (C) 1994-96 Marc ZYNGIER
	     <zyngier@ufr-info-p7.ibp.fr> or
	     <maz@gloups.fdn.fr>
             Copyright (C) 1999, 2000 Ingo Molnar, Red Hat


   RAID-0 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/raid0.h>

#define MAJOR_NR MD_MAJOR
#define MD_DRIVER
#define MD_PERSONALITY

static void raid0_unplug(request_queue_t *q)
{
	mddev_t *mddev = q->queuedata;
	raid0_conf_t *conf = mddev_to_conf(mddev);
	mdk_rdev_t **devlist = conf->strip_zone[0].dev;
	int i;

	for (i=0; i<mddev->raid_disks; i++) {
		request_queue_t *r_queue = bdev_get_queue(devlist[i]->bdev);

		if (r_queue->unplug_fn)
			r_queue->unplug_fn(r_queue);
	}
}

static int raid0_issue_flush(request_queue_t *q, struct gendisk *disk,
			     sector_t *error_sector)
{
	mddev_t *mddev = q->queuedata;
	raid0_conf_t *conf = mddev_to_conf(mddev);
	mdk_rdev_t **devlist = conf->strip_zone[0].dev;
	int i, ret = 0;

	for (i=0; i<mddev->raid_disks && ret == 0; i++) {
		struct block_device *bdev = devlist[i]->bdev;
		request_queue_t *r_queue = bdev_get_queue(bdev);

		if (!r_queue->issue_flush_fn)
			ret = -EOPNOTSUPP;
		else
			ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk, error_sector);
	}
	return ret;
}


static int create_strip_zones (mddev_t *mddev)
{
	int i, c, j;
	sector_t current_offset, curr_zone_offset;
	sector_t min_spacing;
	raid0_conf_t *conf = mddev_to_conf(mddev);
	mdk_rdev_t *smallest, *rdev1, *rdev2, *rdev;
	struct list_head *tmp1, *tmp2;
	struct strip_zone *zone;
	int cnt;
	char b[BDEVNAME_SIZE];
 
	/*
	 * The number of 'same size groups'
	 */
	conf->nr_strip_zones = 0;
 
	ITERATE_RDEV(mddev,rdev1,tmp1) {
		printk("raid0: looking at %s\n",
			bdevname(rdev1->bdev,b));
		c = 0;
		ITERATE_RDEV(mddev,rdev2,tmp2) {
			printk("raid0:   comparing %s(%llu)",
			       bdevname(rdev1->bdev,b),
			       (unsigned long long)rdev1->size);
			printk(" with %s(%llu)\n",
			       bdevname(rdev2->bdev,b),
			       (unsigned long long)rdev2->size);
			if (rdev2 == rdev1) {
				printk("raid0:   END\n");
				break;
			}
			if (rdev2->size == rdev1->size)
			{
				/*
				 * Not unique, don't count it as a new
				 * group
				 */
				printk("raid0:   EQUAL\n");
				c = 1;
				break;
			}
			printk("raid0:   NOT EQUAL\n");
		}
		if (!c) {
			printk("raid0:   ==> UNIQUE\n");
			conf->nr_strip_zones++;
			printk("raid0: %d zones\n", conf->nr_strip_zones);
		}
	}
	printk("raid0: FINAL %d zones\n", conf->nr_strip_zones);

	conf->strip_zone = kzalloc(sizeof(struct strip_zone)*
				conf->nr_strip_zones, GFP_KERNEL);
	if (!conf->strip_zone)
		return 1;
	conf->devlist = kzalloc(sizeof(mdk_rdev_t*)*
				conf->nr_strip_zones*mddev->raid_disks,
				GFP_KERNEL);
	if (!conf->devlist)
		return 1;

	/* The first zone must contain all devices, so here we check that
	 * there is a proper alignment of slots to devices and find them all
	 */
	zone = &conf->strip_zone[0];
	cnt = 0;
	smallest = NULL;
	zone->dev = conf->devlist;
	ITERATE_RDEV(mddev, rdev1, tmp1) {
		int j = rdev1->raid_disk;

		if (j < 0 || j >= mddev->raid_disks) {
			printk("raid0: bad disk number %d - aborting!\n", j);
			goto abort;
		}
		if (zone->dev[j]) {
			printk("raid0: multiple devices for %d - aborting!\n",
				j);
			goto abort;
		}
		zone->dev[j] = rdev1;

		blk_queue_stack_limits(mddev->queue,
				       rdev1->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 (rdev1->bdev->bd_disk->queue->merge_bvec_fn &&
		    mddev->queue->max_sectors > (PAGE_SIZE>>9))
			blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

		if (!smallest || (rdev1->size <smallest->size))
			smallest = rdev1;
		cnt++;
	}
	if (cnt != mddev->raid_disks) {
		printk("raid0: too few disks (%d of %d) - aborting!\n",
			cnt, mddev->raid_disks);
		goto abort;
	}
	zone->nb_dev = cnt;
	zone->size = smallest->size * cnt;
	zone->zone_offset = 0;

	current_offset = smallest->size;
	curr_zone_offset = zone->size;

	/* now do the other zones */
	for (i = 1; i < conf->nr_strip_zones; i++)
	{
		zone = conf->strip_zone + i;
		zone->dev = conf->strip_zone[i-1].dev + mddev->raid_disks;

		printk("raid0: zone %d\n", i);
		zone->dev_offset = current_offset;
		smallest = NULL;
		c = 0;

		for (j=0; j<cnt; j++) {
			char b[BDEVNAME_SIZE];
			rdev = conf->strip_zone[0].dev[j];
			printk("raid0: checking %s ...", bdevname(rdev->bdev,b));
			if (rdev->size > current_offset)
			{
				printk(" contained as device %d\n", c);
				zone->dev[c] = rdev;
				c++;
				if (!smallest || (rdev->size <smallest->size)) {
					smallest = rdev;
					printk("  (%llu) is smallest!.\n", 
						(unsigned long long)rdev->size);
				}
			} else
				printk(" nope.\n");
		}

		zone->nb_dev = c;
		zone->size = (smallest->size - current_offset) * c;
		printk("raid0: zone->nb_dev: %d, size: %llu\n",
			zone->nb_dev, (unsigned long long)zone->size);

		zone->zone_offset = curr_zone_offset;
		curr_zone_offset += zone->size;

		current_offset = smallest->size;
		printk("raid0: current zone offset: %llu\n",
			(unsigned long long)current_offset);
	}

	/* Now find appropriate hash spacing.
	 * We want a number which causes most hash entries to cover
	 * at most two strips, but the hash table must be at most
	 * 1 PAGE.  We choose the smallest strip, or contiguous collection
	 * of strips, that has big enough size.  We never consider the last
	 * strip though as it's size has no bearing on the efficacy of the hash
	 * table.
	 */
	conf->hash_spacing = curr_zone_offset;
	min_spacing = curr_zone_offset;
	sector_div(min_spacing, PAGE_SIZE/sizeof(struct strip_zone*));
	for (i=0; i < conf->nr_strip_zones-1; i++) {
		sector_t sz = 0;
		for (j=i; j<conf->nr_strip_zones-1 &&
			     sz < min_spacing ; j++)
			sz += conf->strip_zone[j].size;
		if (sz >= min_spacing && sz < conf->hash_spacing)
			conf->hash_spacing = sz;
	}

	mddev->queue->unplug_fn = raid0_unplug;

	mddev->queue->issue_flush_fn = raid0_issue_flush;

	printk("raid0: done.\n");
	return 0;
 abort:
	return 1;
}

/**
 *	raid0_mergeable_bvec -- tell bio layer if a 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 accept at this offset
 */
static int raid0_mergeable_bvec(request_queue_t *q, struct bio *bio, struct bio_vec *biovec)
{
	mddev_t *mddev = q->queuedata;
	sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
	int max;
	unsigned int chunk_sectors = mddev->chunk_size >> 9;
	unsigned int bio_sectors = bio->bi_size >> 9;

	max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
	if (max < 0) max = 0; /* bio_add cannot handle a negative return */
	if (max <= biovec->bv_len && bio_sectors == 0)
		return biovec->bv_len;
	else 
		return max;
}

static int raid0_run (mddev_t *mddev)
{
	unsigned  cur=0, i=0, nb_zone;
	s64 size;
	raid0_conf_t *conf;
	mdk_rdev_t *rdev;
	struct list_head *tmp;

	printk("%s: setting max_sectors to %d, segment boundary to %d\n",
	       mdname(mddev),
	       mddev->chunk_size >> 9,
	       (mddev->chunk_size>>1)-1);
	blk_queue_max_sectors(mddev->queue, mddev->chunk_size >> 9);
	blk_queue_segment_boundary(mddev->queue, (mddev->chunk_size>>1) - 1);

	conf = kmalloc(sizeof (raid0_conf_t), GFP_KERNEL);
	if (!conf)
		goto out;
	mddev->private = (void *)conf;
 
	conf->strip_zone = NULL;
	conf->devlist = NULL;
	if (create_strip_zones (mddev)) 
		goto out_free_conf;

	/* calculate array device size */
	mddev->array_size = 0;
	ITERATE_RDEV(mddev,rdev,tmp)
		mddev->array_size += rdev->size;

	printk("raid0 : md_size is %llu blocks.\n", 
		(unsigned long long)mddev->array_size);
	printk("raid0 : conf->hash_spacing is %llu blocks.\n",
		(unsigned long long)conf->hash_spacing);
	{
#if __GNUC__ < 3
		volatile
#endif
		sector_t s = mddev->array_size;
		sector_t space = conf->hash_spacing;
		int round;
		conf->preshift = 0;
		if (sizeof(sector_t) > sizeof(u32)) {
			/*shift down space and s so that sector_div will work */
			while (space > (sector_t) (~(u32)0)) {
				s >>= 1;
				space >>= 1;
				s += 1; /* force round-up */
				conf->preshift++;
			}
		}
		round = sector_div(s, (u32)space) ? 1 : 0;
		nb_zone = s + round;
	}
	printk("raid0 : nb_zone is %d.\n", nb_zone);

	printk("raid0 : Allocating %Zd bytes for hash.\n",
				nb_zone*sizeof(struct strip_zone*));
	conf->hash_table = kmalloc (sizeof (struct strip_zone *)*nb_zone, GFP_KERNEL);
	if (!conf->hash_table)
		goto out_free_conf;
	size = conf->strip_zone[cur].size;

	for (i=0; i< nb_zone; i++) {
		conf->hash_table[i] = conf->strip_zone + cur;
		while (size <= conf->hash_spacing) {
			cur++;
			size += conf->strip_zone[cur].size;
		}
		size -= conf->hash_spacing;
	}
	if (conf->preshift) {
		conf->hash_spacing >>= conf->preshift;
		/* round hash_spacing up so when we divide by it, we
		 * err on the side of too-low, which is safest
		 */
		conf->hash_spacing++;
	}

	/* calculate the max read-ahead size.
	 * For read-ahead of large files to be effective, we need to
	 * readahead at least twice a whole stripe. i.e. number of devices
	 * multiplied by chunk size times 2.
	 * If an individual device has an ra_pages greater than the
	 * chunk size, then we will not drive that device as hard as it
	 * wants.  We consider this a configuration error: a larger
	 * chunksize should be used in that case.
	 */
	{
		int stripe = mddev->raid_disks * mddev->chunk_size / PAGE_SIZE;
		if (mddev->queue->backing_dev_info.ra_pages < 2* stripe)
			mddev->queue->backing_dev_info.ra_pages = 2* stripe;
	}


	blk_queue_merge_bvec(mddev->queue, raid0_mergeable_bvec);
	return 0;

out_free_conf:
	kfree(conf->strip_zone);
	kfree(conf->devlist);
	kfree(conf);
	mddev->private = NULL;
out:
	return 1;
}

static int raid0_stop (mddev_t *mddev)
{
	raid0_conf_t *conf = mddev_to_conf(mddev);

	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
	kfree(conf->hash_table);
	conf->hash_table = NULL;
	kfree(conf->strip_zone);
	conf->strip_zone = NULL;
	kfree(conf);
	mddev->private = NULL;

	return 0;
}

static int raid0_make_request (request_queue_t *q, struct bio *bio)
{
	mddev_t *mddev = q->queuedata;
	unsigned int sect_in_chunk, chunksize_bits,  chunk_size, chunk_sects;
	raid0_conf_t *conf = mddev_to_conf(mddev);
	struct strip_zone *zone;
	mdk_rdev_t *tmp_dev;
	unsigned long chunk;
	sector_t block, rsect;
	const int rw = bio_data_dir(bio);

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

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

	chunk_size = mddev->chunk_size >> 10;
	chunk_sects = mddev->chunk_size >> 9;
	chunksize_bits = ffz(~chunk_size);
	block = bio->bi_sector >> 1;
	

	if (unlikely(chunk_sects < (bio->bi_sector & (chunk_sects - 1)) + (bio->bi_size >> 9))) {
		struct bio_pair *bp;
		/* Sanity check -- queue functions should prevent this happening */
		if (bio->bi_vcnt != 1 ||
		    bio->bi_idx != 0)
			goto bad_map;
		/* This is a one page bio that upper layers
		 * refuse to split for us, so we need to split it.
		 */
		bp = bio_split(bio, bio_split_pool, chunk_sects - (bio->bi_sector & (chunk_sects - 1)) );
		if (raid0_make_request(q, &bp->bio1))
			generic_make_request(&bp->bio1);
		if (raid0_make_request(q, &bp->bio2))
			generic_make_request(&bp->bio2);

		bio_pair_release(bp);
		return 0;
	}
 

	{
#if __GNUC__ < 3
		volatile
#endif
		sector_t x = block >> conf->preshift;
		sector_div(x, (u32)conf->hash_spacing);
		zone = conf->hash_table[x];
	}
 
	while (block >= (zone->zone_offset + zone->size)) 
		zone++;
    
	sect_in_chunk = bio->bi_sector & ((chunk_size<<1) -1);


	{
		sector_t x =  (block - zone->zone_offset) >> chunksize_bits;

		sector_div(x, zone->nb_dev);
		chunk = x;
		BUG_ON(x != (sector_t)chunk);

		x = block >> chunksize_bits;
		tmp_dev = zone->dev[sector_div(x, zone->nb_dev)];
	}
	rsect = (((chunk << chunksize_bits) + zone->dev_offset)<<1)
		+ sect_in_chunk;
 
	bio->bi_bdev = tmp_dev->bdev;
	bio->bi_sector = rsect + tmp_dev->data_offset;

	/*
	 * Let the main block layer submit the IO and resolve recursion:
	 */
	return 1;

bad_map:
	printk("raid0_make_request bug: can't convert block across chunks"
		" or bigger than %dk %llu %d\n", chunk_size, 
		(unsigned long long)bio->bi_sector, bio->bi_size >> 10);

	bio_io_error(bio, bio->bi_size);
	return 0;
}
			   
static void raid0_status (struct seq_file *seq, mddev_t *mddev)
{
#undef MD_DEBUG
#ifdef MD_DEBUG
	int j, k, h;
	char b[BDEVNAME_SIZE];
	raid0_conf_t *conf = mddev_to_conf(mddev);
  
	h = 0;
	for (j = 0; j < conf->nr_strip_zones; j++) {
		seq_printf(seq, "      z%d", j);
		if (conf->hash_table[h] == conf->strip_zone+j)
			seq_printf("(h%d)", h++);
		seq_printf(seq, "=[");
		for (k = 0; k < conf->strip_zone[j].nb_dev; k++)
			seq_printf (seq, "%s/", bdevname(
				conf->strip_zone[j].dev[k]->bdev,b));

		seq_printf (seq, "] zo=%d do=%d s=%d\n",
				conf->strip_zone[j].zone_offset,
				conf->strip_zone[j].dev_offset,
				conf->strip_zone[j].size);
	}
#endif
	seq_printf(seq, " %dk chunks", mddev->chunk_size/1024);
	return;
}

static mdk_personality_t raid0_personality=
{
	.name		= "raid0",
	.owner		= THIS_MODULE,
	.make_request	= raid0_make_request,
	.run		= raid0_run,
	.stop		= raid0_stop,
	.status		= raid0_status,
};

static int __init raid0_init (void)
{
	return register_md_personality (RAID0, &raid0_personality);
}

static void raid0_exit (void)
{
	unregister_md_personality (RAID0);
}

module_init(raid0_init);
module_exit(raid0_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS("md-personality-2"); /* RAID0 */