/*
* multipath.c : Multiple Devices driver for Linux
*
* Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
*
* Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
*
* MULTIPATH management functions.
*
* derived from raid1.c.
*
* 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/slab.h>
#include <linux/spinlock.h>
#include <linux/raid/multipath.h>
#include <linux/buffer_head.h>
#include <asm/atomic.h>
#define MAJOR_NR MD_MAJOR
#define MD_DRIVER
#define MD_PERSONALITY
#define MAX_WORK_PER_DISK 128
#define NR_RESERVED_BUFS 32
static mdk_personality_t multipath_personality;
static void *mp_pool_alloc(unsigned int __nocast gfp_flags, void *data)
{
struct multipath_bh *mpb;
mpb = kmalloc(sizeof(*mpb), gfp_flags);
if (mpb)
memset(mpb, 0, sizeof(*mpb));
return mpb;
}
static void mp_pool_free(void *mpb, void *data)
{
kfree(mpb);
}
static int multipath_map (multipath_conf_t *conf)
{
int i, disks = conf->raid_disks;
/*
* Later we do read balancing on the read side
* now we use the first available disk.
*/
rcu_read_lock();
for (i = 0; i < disks; i++) {
mdk_rdev_t *rdev = conf->multipaths[i].rdev;
if (rdev && rdev->in_sync) {
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
return i;
}
}
rcu_read_unlock();
printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
return (-1);
}
static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
{
unsigned long flags;
mddev_t *mddev = mp_bh->mddev;
multipath_conf_t *conf = mddev_to_conf(mddev);
spin_lock_irqsave(&conf->device_lock, flags);
list_add(&mp_bh->retry_list, &conf->retry_list);
spin_unlock_irqrestore(&conf->device_lock, flags);
md_wakeup_thread(mddev->thread);
}
/*
* multipath_end_bh_io() is called when we have finished servicing a multipathed
* operation and are ready to return a success/failure code to the buffer
* cache layer.
*/
static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
{
struct bio *bio = mp_bh->master_bio;
multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
bio_endio(bio, bio->bi_size, err);
mempool_free(mp_bh, conf->pool);
}
int multipath_end_request(struct bio *bio, unsigned int bytes_done, int error)
{
int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
if (bio->bi_size)
return 1;
if (uptodate)
multipath_end_bh_io(mp_bh, 0);
else if (!bio_rw_ahead(bio)) {
/*
* oops, IO error:
*/
char b[BDEVNAME_SIZE];
md_error (mp_bh->mddev, rdev);
printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
bdevname(rdev->bdev,b),
(unsigned long long)bio->bi_sector);
multipath_reschedule_retry(mp_bh);
} else
multipath_end_bh_io(mp_bh, error);
rdev_dec_pending(rdev, conf->mddev);
return 0;
}
static void unplug_slaves(mddev_t *mddev)
{
multipath_conf_t *conf = mddev_to_conf(mddev);
int i;
rcu_read_lock();
for (i=0; i<mddev->raid_disks; i++) {
mdk_rdev_t *rdev = conf->multipaths[i].rdev;
if (rdev && !rdev->faulty && atomic_read(&rdev->nr_pending)) {
request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
if (r_queue->unplug_fn)
r_queue->unplug_fn(r_queue);
rdev_dec_pending(rdev, mddev);
rcu_read_lock();
}
}
rcu_read_unlock();
}
static void multipath_unplug(request_queue_t *q)
{
unplug_slaves(q->queuedata);
}
static int multipath_make_request (request_queue_t *q, struct bio * bio)
{
mddev_t *mddev = q->queuedata;
multipath_conf_t *conf = mddev_to_conf(mddev);
struct multipath_bh * mp_bh;
struct multipath_info *multipath;
mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
mp_bh->master_bio = bio;
mp_bh->mddev = mddev;
if (bio_data_dir(bio)==WRITE) {
disk_stat_inc(mddev->gendisk, writes);
disk_stat_add(mddev->gendisk, write_sectors, bio_sectors(bio));
} else {
disk_stat_inc(mddev->gendisk, reads);
disk_stat_add(mddev->gendisk, read_sectors, bio_sectors(bio));
}
mp_bh->path = multipath_map(conf);
if (mp_bh->path < 0) {
bio_endio(bio, bio->bi_size, -EIO);
mempool_free(mp_bh, conf->pool);
return 0;
}
multipath = conf->multipaths + mp_bh->path;
mp_bh->bio = *bio;
mp_bh->bio.bi_sector += multipath->rdev->data_offset;
mp_bh->bio.bi_bdev = multipath->rdev->bdev;
mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
mp_bh->bio.bi_end_io = multipath_end_request;
mp_bh->bio.bi_private = mp_bh;
generic_make_request(&mp_bh->bio);
return 0;
}
static void multipath_status (struct seq_file *seq, mddev_t *mddev)
{
multipath_conf_t *conf = mddev_to_conf(mddev);
int i;
seq_printf (seq, " [%d/%d] [", conf->raid_disks,
conf->working_disks);
for (i = 0; i < conf->raid_disks; i++)
seq_printf (seq, "%s",
conf->multipaths[i].rdev &&
conf->multipaths[i].rdev->in_sync ? "U" : "_");
seq_printf (seq, "]");
}
static int multipath_issue_flush(request_queue_t *q, struct gendisk *disk,
sector_t *error_sector)
{
mddev_t *mddev = q->queuedata;
multipath_conf_t *conf = mddev_to_conf(mddev);
int i, ret = 0;
rcu_read_lock();
for (i=0; i<mddev->raid_disks && ret == 0; i++) {
mdk_rdev_t *rdev = conf->multipaths[i].rdev;
if (rdev && !rdev->faulty) {
struct block_device *bdev = rdev->bdev;
request_queue_t *r_queue = bdev_get_queue(bdev);
if (!r_queue->issue_flush_fn)
ret = -EOPNOTSUPP;
else {
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
error_sector);
rdev_dec_pending(rdev, mddev);
rcu_read_lock();
}
}
}
rcu_read_unlock();
return ret;
}
/*
* Careful, this can execute in IRQ contexts as well!
*/
static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
{
multipath_conf_t *conf = mddev_to_conf(mddev);
if (conf->working_disks <= 1) {
/*
* Uh oh, we can do nothing if this is our last path, but
* first check if this is a queued request for a device
* which has just failed.
*/
printk(KERN_ALERT
"multipath: only one IO path left and IO error.\n");
/* leave it active... it's all we have */
} else {
/*
* Mark disk as unusable
*/
if (!rdev->faulty) {
char b[BDEVNAME_SIZE];
rdev->in_sync = 0;
rdev->faulty = 1;
mddev->sb_dirty = 1;
conf->working_disks--;
printk(KERN_ALERT "multipath: IO failure on %s,"
" disabling IO path. \n Operation continuing"
" on %d IO paths.\n",
bdevname (rdev->bdev,b),
conf->working_disks);
}
}
}
static void print_multipath_conf (multipath_conf_t *conf)
{
int i;
struct multipath_info *tmp;
printk("MULTIPATH conf printout:\n");
if (!conf) {
printk("(conf==NULL)\n");
return;
}
printk(" --- wd:%d rd:%d\n", conf->working_disks,
conf->raid_disks);
for (i = 0; i < conf->raid_disks; i++) {
char b[BDEVNAME_SIZE];
tmp = conf->multipaths + i;
if (tmp->rdev)
printk(" disk%d, o:%d, dev:%s\n",
i,!tmp->rdev->faulty,
bdevname(tmp->rdev->bdev,b));
}
}
static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
{
multipath_conf_t *conf = mddev->private;
int found = 0;
int path;
struct multipath_info *p;
print_multipath_conf(conf);
for (path=0; path<mddev->raid_disks; path++)
if ((p=conf->multipaths+path)->rdev == NULL) {
blk_queue_stack_limits(mddev->queue,
rdev->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.
* (Note: it is very unlikely that a device with
* merge_bvec_fn will be involved in multipath.)
*/
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
mddev->queue->max_sectors > (PAGE_SIZE>>9))
blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
conf->working_disks++;
rdev->raid_disk = path;
rdev->in_sync = 1;
p->rdev = rdev;
found = 1;
}
print_multipath_conf(conf);
return found;
}
static int multipath_remove_disk(mddev_t *mddev, int number)
{
multipath_conf_t *conf = mddev->private;
int err = 0;
mdk_rdev_t *rdev;
struct multipath_info *p = conf->multipaths + number;
print_multipath_conf(conf);
rdev = p->rdev;
if (rdev) {
if (rdev->in_sync ||
atomic_read(&rdev->nr_pending)) {
printk(KERN_ERR "hot-remove-disk, slot %d is identified" " but is still operational!\n", number);
err = -EBUSY;
goto abort;
}
p->rdev = NULL;
synchronize_rcu();
if (atomic_read(&rdev->nr_pending)) {
/* lost the race, try later */
err = -EBUSY;
p->rdev = rdev;
}
}
abort:
print_multipath_conf(conf);
return err;
}
/*
* This is a kernel thread which:
*
* 1. Retries failed read operations on working multipaths.
* 2. Updates the raid superblock when problems encounter.
* 3. Performs writes following reads for array syncronising.
*/
static void multipathd (mddev_t *mddev)
{
struct multipath_bh *mp_bh;
struct bio *bio;
unsigned long flags;
multipath_conf_t *conf = mddev_to_conf(mddev);
struct list_head *head = &conf->retry_list;
md_check_recovery(mddev);
for (;;) {
char b[BDEVNAME_SIZE];
spin_lock_irqsave(&conf->device_lock, flags);
if (list_empty(head))
break;
mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
list_del(head->prev);
spin_unlock_irqrestore(&conf->device_lock, flags);
bio = &mp_bh->bio;
bio->bi_sector = mp_bh->master_bio->bi_sector;
if ((mp_bh->path = multipath_map (conf))<0) {
printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
" error for block %llu\n",
bdevname(bio->bi_bdev,b),
(unsigned long long)bio->bi_sector);
multipath_end_bh_io(mp_bh, -EIO);
} else {
printk(KERN_ERR "multipath: %s: redirecting sector %llu"
" to another IO path\n",
bdevname(bio->bi_bdev,b),
(unsigned long long)bio->bi_sector);
*bio = *(mp_bh->master_bio);
bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
bio->bi_rw |= (1 << BIO_RW_FAILFAST);
bio->bi_end_io = multipath_end_request;
bio->bi_private = mp_bh;
generic_make_request(bio);
}
}
spin_unlock_irqrestore(&conf->device_lock, flags);
}
static int multipath_run (mddev_t *mddev)
{
multipath_conf_t *conf;
int disk_idx;
struct multipath_info *disk;
mdk_rdev_t *rdev;
struct list_head *tmp;
if (mddev->level != LEVEL_MULTIPATH) {
printk("multipath: %s: raid level not set to multipath IO (%d)\n",
mdname(mddev), mddev->level);
goto out;
}
/*
* copy the already verified devices into our private MULTIPATH
* bookkeeping area. [whatever we allocate in multipath_run(),
* should be freed in multipath_stop()]
*/
conf = kmalloc(sizeof(multipath_conf_t), GFP_KERNEL);
mddev->private = conf;
if (!conf) {
printk(KERN_ERR
"multipath: couldn't allocate memory for %s\n",
mdname(mddev));
goto out;
}
memset(conf, 0, sizeof(*conf));
conf->multipaths = kmalloc(sizeof(struct multipath_info)*mddev->raid_disks,
GFP_KERNEL);
if (!conf->multipaths) {
printk(KERN_ERR
"multipath: couldn't allocate memory for %s\n",
mdname(mddev));
goto out_free_conf;
}
memset(conf->multipaths, 0, sizeof(struct multipath_info)*mddev->raid_disks);
mddev->queue->unplug_fn = multipath_unplug;
mddev->queue->issue_flush_fn = multipath_issue_flush;
conf->working_disks = 0;
ITERATE_RDEV(mddev,rdev,tmp) {
disk_idx = rdev->raid_disk;
if (disk_idx < 0 ||
disk_idx >= mddev->raid_disks)
continue;
disk = conf->multipaths + disk_idx;
disk->rdev = rdev;
blk_queue_stack_limits(mddev->queue,
rdev->bdev->bd_disk->queue);
/* as we don't honour merge_bvec_fn, we must never risk
* violating it, not that we ever expect a device with
* a merge_bvec_fn to be involved in multipath */
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
mddev->queue->max_sectors > (PAGE_SIZE>>9))
blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
if (!rdev->faulty)
conf->working_disks++;
}
conf->raid_disks = mddev->raid_disks;
mddev->sb_dirty = 1;
conf->mddev = mddev;
spin_lock_init(&conf->device_lock);
INIT_LIST_HEAD(&conf->retry_list);
if (!conf->working_disks) {
printk(KERN_ERR "multipath: no operational IO paths for %s\n",
mdname(mddev));
goto out_free_conf;
}
mddev->degraded = conf->raid_disks = conf->working_disks;
conf->pool = mempool_create(NR_RESERVED_BUFS,
mp_pool_alloc, mp_pool_free,
NULL);
if (conf->pool == NULL) {
printk(KERN_ERR
"multipath: couldn't allocate memory for %s\n",
mdname(mddev));
goto out_free_conf;
}
{
mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
if (!mddev->thread) {
printk(KERN_ERR "multipath: couldn't allocate thread"
" for %s\n", mdname(mddev));
goto out_free_conf;
}
}
printk(KERN_INFO
"multipath: array %s active with %d out of %d IO paths\n",
mdname(mddev), conf->working_disks, mddev->raid_disks);
/*
* Ok, everything is just fine now
*/
mddev->array_size = mddev->size;
return 0;
out_free_conf:
if (conf->pool)
mempool_destroy(conf->pool);
if (conf->multipaths)
kfree(conf->multipaths);
kfree(conf);
mddev->private = NULL;
out:
return -EIO;
}
static int multipath_stop (mddev_t *mddev)
{
multipath_conf_t *conf = mddev_to_conf(mddev);
md_unregister_thread(mddev->thread);
mddev->thread = NULL;
blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
mempool_destroy(conf->pool);
kfree(conf->multipaths);
kfree(conf);
mddev->private = NULL;
return 0;
}
static mdk_personality_t multipath_personality=
{
.name = "multipath",
.owner = THIS_MODULE,
.make_request = multipath_make_request,
.run = multipath_run,
.stop = multipath_stop,
.status = multipath_status,
.error_handler = multipath_error,
.hot_add_disk = multipath_add_disk,
.hot_remove_disk= multipath_remove_disk,
};
static int __init multipath_init (void)
{
return register_md_personality (MULTIPATH, &multipath_personality);
}
static void __exit multipath_exit (void)
{
unregister_md_personality (MULTIPATH);
}
module_init(multipath_init);
module_exit(multipath_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
