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linux-next/drivers/md/raid0.c
NeilBrown a2826aa92e md: support barrier requests on all personalities. 
Previously barriers were only supported on RAID1.  This is because
other levels requires synchronisation across all devices and so needed
a different approach.
Here is that approach.

When a barrier arrives, we send a zero-length barrier to every active
device.  When that completes - and if the original request was not
empty -  we submit the barrier request itself (with the barrier flag
cleared) and then submit a fresh load of zero length barriers.

The barrier request itself is asynchronous, but any subsequent
request will block until the barrier completes.

The reason for clearing the barrier flag is that a barrier request is
allowed to fail.  If we pass a non-empty barrier through a striping
raid level it is conceivable that part of it could succeed and part
could fail.  That would be way too hard to deal with.
So if the first run of zero length barriers succeed, we assume all is
sufficiently well that we send the request and ignore errors in the
second run of barriers.

RAID5 needs extra care as write requests may not have been submitted
to the underlying devices yet.  So we flush the stripe cache before
proceeding with the barrier.

Note that the second set of zero-length barriers are submitted
immediately after the original request is submitted.  Thus when
a personality finds mddev->barrier to be set during make_request,
it should not return from make_request until the corresponding
per-device request(s) have been queued.

That will be done in later patches.

Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Andre Noll <maan@systemlinux.org>
2009-12-14 12:49:49 +11:00

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/*
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/blkdev.h>
#include <linux/seq_file.h>
#include "md.h"
#include "raid0.h"
static void raid0_unplug(struct request_queue *q)
{
mddev_t *mddev = q->queuedata;
raid0_conf_t *conf = mddev->private;
mdk_rdev_t **devlist = conf->devlist;
int i;
for (i=0; i<mddev->raid_disks; i++) {
struct request_queue *r_queue = bdev_get_queue(devlist[i]->bdev);
blk_unplug(r_queue);
}
}
static int raid0_congested(void *data, int bits)
{
mddev_t *mddev = data;
raid0_conf_t *conf = mddev->private;
mdk_rdev_t **devlist = conf->devlist;
int i, ret = 0;
if (mddev_congested(mddev, bits))
return 1;
for (i = 0; i < mddev->raid_disks && !ret ; i++) {
struct request_queue *q = bdev_get_queue(devlist[i]->bdev);
ret |= bdi_congested(&q->backing_dev_info, bits);
}
return ret;
}
/*
* inform the user of the raid configuration
*/
static void dump_zones(mddev_t *mddev)
{
int j, k, h;
sector_t zone_size = 0;
sector_t zone_start = 0;
char b[BDEVNAME_SIZE];
raid0_conf_t *conf = mddev->private;
printk(KERN_INFO "******* %s configuration *********\n",
mdname(mddev));
h = 0;
for (j = 0; j < conf->nr_strip_zones; j++) {
printk(KERN_INFO "zone%d=[", j);
for (k = 0; k < conf->strip_zone[j].nb_dev; k++)
printk("%s/",
bdevname(conf->devlist[j*mddev->raid_disks
+ k]->bdev, b));
printk("]\n");
zone_size = conf->strip_zone[j].zone_end - zone_start;
printk(KERN_INFO " zone offset=%llukb "
"device offset=%llukb size=%llukb\n",
(unsigned long long)zone_start>>1,
(unsigned long long)conf->strip_zone[j].dev_start>>1,
(unsigned long long)zone_size>>1);
zone_start = conf->strip_zone[j].zone_end;
}
printk(KERN_INFO "**********************************\n\n");
}
static int create_strip_zones(mddev_t *mddev)
{
int i, c, err;
sector_t curr_zone_end, sectors;
mdk_rdev_t *smallest, *rdev1, *rdev2, *rdev, **dev;
struct strip_zone *zone;
int cnt;
char b[BDEVNAME_SIZE];
raid0_conf_t *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
if (!conf)
return -ENOMEM;
list_for_each_entry(rdev1, &mddev->disks, same_set) {
printk(KERN_INFO "raid0: looking at %s\n",
bdevname(rdev1->bdev,b));
c = 0;
/* round size to chunk_size */
sectors = rdev1->sectors;
sector_div(sectors, mddev->chunk_sectors);
rdev1->sectors = sectors * mddev->chunk_sectors;
list_for_each_entry(rdev2, &mddev->disks, same_set) {
printk(KERN_INFO "raid0: comparing %s(%llu)",
bdevname(rdev1->bdev,b),
(unsigned long long)rdev1->sectors);
printk(KERN_INFO " with %s(%llu)\n",
bdevname(rdev2->bdev,b),
(unsigned long long)rdev2->sectors);
if (rdev2 == rdev1) {
printk(KERN_INFO "raid0: END\n");
break;
}
if (rdev2->sectors == rdev1->sectors) {
/*
* Not unique, don't count it as a new
* group
*/
printk(KERN_INFO "raid0: EQUAL\n");
c = 1;
break;
}
printk(KERN_INFO "raid0: NOT EQUAL\n");
}
if (!c) {
printk(KERN_INFO "raid0: ==> UNIQUE\n");
conf->nr_strip_zones++;
printk(KERN_INFO "raid0: %d zones\n",
conf->nr_strip_zones);
}
}
printk(KERN_INFO "raid0: FINAL %d zones\n", conf->nr_strip_zones);
err = -ENOMEM;
conf->strip_zone = kzalloc(sizeof(struct strip_zone)*
conf->nr_strip_zones, GFP_KERNEL);
if (!conf->strip_zone)
goto abort;
conf->devlist = kzalloc(sizeof(mdk_rdev_t*)*
conf->nr_strip_zones*mddev->raid_disks,
GFP_KERNEL);
if (!conf->devlist)
goto abort;
/* 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;
dev = conf->devlist;
err = -EINVAL;
list_for_each_entry(rdev1, &mddev->disks, same_set) {
int j = rdev1->raid_disk;
if (j < 0 || j >= mddev->raid_disks) {
printk(KERN_ERR "raid0: bad disk number %d - "
"aborting!\n", j);
goto abort;
}
if (dev[j]) {
printk(KERN_ERR "raid0: multiple devices for %d - "
"aborting!\n", j);
goto abort;
}
dev[j] = rdev1;
disk_stack_limits(mddev->gendisk, rdev1->bdev,
rdev1->data_offset << 9);
/* 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 &&
queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
if (!smallest || (rdev1->sectors < smallest->sectors))
smallest = rdev1;
cnt++;
}
if (cnt != mddev->raid_disks) {
printk(KERN_ERR "raid0: too few disks (%d of %d) - "
"aborting!\n", cnt, mddev->raid_disks);
goto abort;
}
zone->nb_dev = cnt;
zone->zone_end = smallest->sectors * cnt;
curr_zone_end = zone->zone_end;
/* now do the other zones */
for (i = 1; i < conf->nr_strip_zones; i++)
{
int j;
zone = conf->strip_zone + i;
dev = conf->devlist + i * mddev->raid_disks;
printk(KERN_INFO "raid0: zone %d\n", i);
zone->dev_start = smallest->sectors;
smallest = NULL;
c = 0;
for (j=0; j<cnt; j++) {
rdev = conf->devlist[j];
printk(KERN_INFO "raid0: checking %s ...",
bdevname(rdev->bdev, b));
if (rdev->sectors <= zone->dev_start) {
printk(KERN_INFO " nope.\n");
continue;
}
printk(KERN_INFO " contained as device %d\n", c);
dev[c] = rdev;
c++;
if (!smallest || rdev->sectors < smallest->sectors) {
smallest = rdev;
printk(KERN_INFO " (%llu) is smallest!.\n",
(unsigned long long)rdev->sectors);
}
}
zone->nb_dev = c;
sectors = (smallest->sectors - zone->dev_start) * c;
printk(KERN_INFO "raid0: zone->nb_dev: %d, sectors: %llu\n",
zone->nb_dev, (unsigned long long)sectors);
curr_zone_end += sectors;
zone->zone_end = curr_zone_end;
printk(KERN_INFO "raid0: current zone start: %llu\n",
(unsigned long long)smallest->sectors);
}
mddev->queue->unplug_fn = raid0_unplug;
mddev->queue->backing_dev_info.congested_fn = raid0_congested;
mddev->queue->backing_dev_info.congested_data = mddev;
/*
* now since we have the hard sector sizes, we can make sure
* chunk size is a multiple of that sector size
*/
if ((mddev->chunk_sectors << 9) % queue_logical_block_size(mddev->queue)) {
printk(KERN_ERR "%s chunk_size of %d not valid\n",
mdname(mddev),
mddev->chunk_sectors << 9);
goto abort;
}
blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9);
blk_queue_io_opt(mddev->queue,
(mddev->chunk_sectors << 9) * mddev->raid_disks);
printk(KERN_INFO "raid0: done.\n");
mddev->private = conf;
return 0;
abort:
kfree(conf->strip_zone);
kfree(conf->devlist);
kfree(conf);
mddev->private = NULL;
return err;
}
/**
* raid0_mergeable_bvec -- tell bio layer if a 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 accept at this offset
*/
static int raid0_mergeable_bvec(struct request_queue *q,
struct bvec_merge_data *bvm,
struct bio_vec *biovec)
{
mddev_t *mddev = q->queuedata;
sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
int max;
unsigned int chunk_sectors = mddev->chunk_sectors;
unsigned int bio_sectors = bvm->bi_size >> 9;
if (is_power_of_2(chunk_sectors))
max = (chunk_sectors - ((sector & (chunk_sectors-1))
+ bio_sectors)) << 9;
else
max = (chunk_sectors - (sector_div(sector, chunk_sectors)
+ 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 sector_t raid0_size(mddev_t *mddev, sector_t sectors, int raid_disks)
{
sector_t array_sectors = 0;
mdk_rdev_t *rdev;
WARN_ONCE(sectors || raid_disks,
"%s does not support generic reshape\n", __func__);
list_for_each_entry(rdev, &mddev->disks, same_set)
array_sectors += rdev->sectors;
return array_sectors;
}
static int raid0_run(mddev_t *mddev)
{
int ret;
if (mddev->chunk_sectors == 0) {
printk(KERN_ERR "md/raid0: chunk size must be set.\n");
return -EINVAL;
}
if (md_check_no_bitmap(mddev))
return -EINVAL;
blk_queue_max_sectors(mddev->queue, mddev->chunk_sectors);
mddev->queue->queue_lock = &mddev->queue->__queue_lock;
ret = create_strip_zones(mddev);
if (ret < 0)
return ret;
/* calculate array device size */
md_set_array_sectors(mddev, raid0_size(mddev, 0, 0));
printk(KERN_INFO "raid0 : md_size is %llu sectors.\n",
(unsigned long long)mddev->array_sectors);
/* 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_sectors << 9) / 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);
dump_zones(mddev);
md_integrity_register(mddev);
return 0;
}
static int raid0_stop(mddev_t *mddev)
{
raid0_conf_t *conf = mddev->private;
blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
kfree(conf->strip_zone);
kfree(conf->devlist);
kfree(conf);
mddev->private = NULL;
return 0;
}
/* Find the zone which holds a particular offset
* Update *sectorp to be an offset in that zone
*/
static struct strip_zone *find_zone(struct raid0_private_data *conf,
sector_t *sectorp)
{
int i;
struct strip_zone *z = conf->strip_zone;
sector_t sector = *sectorp;
for (i = 0; i < conf->nr_strip_zones; i++)
if (sector < z[i].zone_end) {
if (i)
*sectorp = sector - z[i-1].zone_end;
return z + i;
}
BUG();
}
/*
* remaps the bio to the target device. we separate two flows.
* power 2 flow and a general flow for the sake of perfromance
*/
static mdk_rdev_t *map_sector(mddev_t *mddev, struct strip_zone *zone,
sector_t sector, sector_t *sector_offset)
{
unsigned int sect_in_chunk;
sector_t chunk;
raid0_conf_t *conf = mddev->private;
unsigned int chunk_sects = mddev->chunk_sectors;
if (is_power_of_2(chunk_sects)) {
int chunksect_bits = ffz(~chunk_sects);
/* find the sector offset inside the chunk */
sect_in_chunk = sector & (chunk_sects - 1);
sector >>= chunksect_bits;
/* chunk in zone */
chunk = *sector_offset;
/* quotient is the chunk in real device*/
sector_div(chunk, zone->nb_dev << chunksect_bits);
} else{
sect_in_chunk = sector_div(sector, chunk_sects);
chunk = *sector_offset;
sector_div(chunk, chunk_sects * zone->nb_dev);
}
/*
* position the bio over the real device
* real sector = chunk in device + starting of zone
* + the position in the chunk
*/
*sector_offset = (chunk * chunk_sects) + sect_in_chunk;
return conf->devlist[(zone - conf->strip_zone)*mddev->raid_disks
+ sector_div(sector, zone->nb_dev)];
}
/*
* Is io distribute over 1 or more chunks ?
*/
static inline int is_io_in_chunk_boundary(mddev_t *mddev,
unsigned int chunk_sects, struct bio *bio)
{
if (likely(is_power_of_2(chunk_sects))) {
return chunk_sects >= ((bio->bi_sector & (chunk_sects-1))
+ (bio->bi_size >> 9));
} else{
sector_t sector = bio->bi_sector;
return chunk_sects >= (sector_div(sector, chunk_sects)
+ (bio->bi_size >> 9));
}
}
static int raid0_make_request(struct request_queue *q, struct bio *bio)
{
mddev_t *mddev = q->queuedata;
unsigned int chunk_sects;
sector_t sector_offset;
struct strip_zone *zone;
mdk_rdev_t *tmp_dev;
const int rw = bio_data_dir(bio);
int cpu;
if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER))) {
md_barrier_request(mddev, bio);
return 0;
}
cpu = part_stat_lock();
part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
bio_sectors(bio));
part_stat_unlock();
chunk_sects = mddev->chunk_sectors;
if (unlikely(!is_io_in_chunk_boundary(mddev, chunk_sects, bio))) {
sector_t sector = bio->bi_sector;
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.
*/
if (likely(is_power_of_2(chunk_sects)))
bp = bio_split(bio, chunk_sects - (sector &
(chunk_sects-1)));
else
bp = bio_split(bio, chunk_sects -
sector_div(sector, chunk_sects));
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;
}
sector_offset = bio->bi_sector;
zone = find_zone(mddev->private, &sector_offset);
tmp_dev = map_sector(mddev, zone, bio->bi_sector,
&sector_offset);
bio->bi_bdev = tmp_dev->bdev;
bio->bi_sector = sector_offset + zone->dev_start +
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_sects / 2,
(unsigned long long)bio->bi_sector, bio->bi_size >> 10);
bio_io_error(bio);
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->private;
sector_t zone_size;
sector_t zone_start = 0;
h = 0;
for (j = 0; j < conf->nr_strip_zones; j++) {
seq_printf(seq, " z%d", j);
seq_printf(seq, "=[");
for (k = 0; k < conf->strip_zone[j].nb_dev; k++)
seq_printf(seq, "%s/", bdevname(
conf->devlist[j*mddev->raid_disks + k]
->bdev, b));
zone_size = conf->strip_zone[j].zone_end - zone_start;
seq_printf(seq, "] ze=%lld ds=%lld s=%lld\n",
(unsigned long long)zone_start>>1,
(unsigned long long)conf->strip_zone[j].dev_start>>1,
(unsigned long long)zone_size>>1);
zone_start = conf->strip_zone[j].zone_end;
}
#endif
seq_printf(seq, " %dk chunks", mddev->chunk_sectors / 2);
return;
}
static struct mdk_personality raid0_personality=
{
.name = "raid0",
.level = 0,
.owner = THIS_MODULE,
.make_request = raid0_make_request,
.run = raid0_run,
.stop = raid0_stop,
.status = raid0_status,
.size = raid0_size,
};
static int __init raid0_init (void)
{
return register_md_personality (&raid0_personality);
}
static void raid0_exit (void)
{
unregister_md_personality (&raid0_personality);
}
module_init(raid0_init);
module_exit(raid0_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS("md-personality-2"); /* RAID0 */
MODULE_ALIAS("md-raid0");
MODULE_ALIAS("md-level-0");
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