linux/drivers/md/multipath.c
Christoph Hellwig 7b6d91daee block: unify flags for struct bio and struct request
Remove the current bio flags and reuse the request flags for the bio, too.
This allows to more easily trace the type of I/O from the filesystem
down to the block driver.  There were two flags in the bio that were
missing in the requests:  BIO_RW_UNPLUG and BIO_RW_AHEAD.  Also I've
renamed two request flags that had a superflous RW in them.

Note that the flags are in bio.h despite having the REQ_ name - as
blkdev.h includes bio.h that is the only way to go for now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-08-07 18:20:39 +02:00

584 lines
15 KiB
C

/*
* 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/blkdev.h>
#include <linux/raid/md_u.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include "md.h"
#include "multipath.h"
#define MAX_WORK_PER_DISK 128
#define NR_RESERVED_BUFS 32
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 = rcu_dereference(conf->multipaths[i].rdev);
if (rdev && test_bit(In_sync, &rdev->flags)) {
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->private;
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 = mp_bh->mddev->private;
bio_endio(bio, err);
mempool_free(mp_bh, conf->pool);
}
static void multipath_end_request(struct bio *bio, int error)
{
int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
struct multipath_bh *mp_bh = bio->bi_private;
multipath_conf_t *conf = mp_bh->mddev->private;
mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
if (uptodate)
multipath_end_bh_io(mp_bh, 0);
else if (!(bio->bi_rw & REQ_RAHEAD)) {
/*
* 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);
}
static void unplug_slaves(mddev_t *mddev)
{
multipath_conf_t *conf = mddev->private;
int i;
rcu_read_lock();
for (i=0; i<mddev->raid_disks; i++) {
mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
if (rdev && !test_bit(Faulty, &rdev->flags)
&& atomic_read(&rdev->nr_pending)) {
struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
blk_unplug(r_queue);
rdev_dec_pending(rdev, mddev);
rcu_read_lock();
}
}
rcu_read_unlock();
}
static void multipath_unplug(struct request_queue *q)
{
unplug_slaves(q->queuedata);
}
static int multipath_make_request(mddev_t *mddev, struct bio * bio)
{
multipath_conf_t *conf = mddev->private;
struct multipath_bh * mp_bh;
struct multipath_info *multipath;
if (unlikely(bio->bi_rw & REQ_HARDBARRIER)) {
md_barrier_request(mddev, bio);
return 0;
}
mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
mp_bh->master_bio = bio;
mp_bh->mddev = mddev;
mp_bh->path = multipath_map(conf);
if (mp_bh->path < 0) {
bio_endio(bio, -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 |= REQ_FAILFAST_TRANSPORT;
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->private;
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 &&
test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
seq_printf (seq, "]");
}
static int multipath_congested(void *data, int bits)
{
mddev_t *mddev = data;
multipath_conf_t *conf = mddev->private;
int i, ret = 0;
if (mddev_congested(mddev, bits))
return 1;
rcu_read_lock();
for (i = 0; i < mddev->raid_disks ; i++) {
mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
if (rdev && !test_bit(Faulty, &rdev->flags)) {
struct request_queue *q = bdev_get_queue(rdev->bdev);
ret |= bdi_congested(&q->backing_dev_info, bits);
/* Just like multipath_map, we just check the
* first available device
*/
break;
}
}
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->private;
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 (!test_bit(Faulty, &rdev->flags)) {
char b[BDEVNAME_SIZE];
clear_bit(In_sync, &rdev->flags);
set_bit(Faulty, &rdev->flags);
set_bit(MD_CHANGE_DEVS, &mddev->flags);
conf->working_disks--;
mddev->degraded++;
printk(KERN_ALERT "multipath: IO failure on %s,"
" disabling IO path.\n"
"multipath: 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,!test_bit(Faulty, &tmp->rdev->flags),
bdevname(tmp->rdev->bdev,b));
}
}
static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
{
multipath_conf_t *conf = mddev->private;
struct request_queue *q;
int err = -EEXIST;
int path;
struct multipath_info *p;
int first = 0;
int last = mddev->raid_disks - 1;
if (rdev->raid_disk >= 0)
first = last = rdev->raid_disk;
print_multipath_conf(conf);
for (path = first; path <= last; path++)
if ((p=conf->multipaths+path)->rdev == NULL) {
q = rdev->bdev->bd_disk->queue;
disk_stack_limits(mddev->gendisk, rdev->bdev,
rdev->data_offset << 9);
/* as we don't honour merge_bvec_fn, we must never risk
* violating it, so limit ->max_segments to one, lying
* within a single page.
* (Note: it is very unlikely that a device with
* merge_bvec_fn will be involved in multipath.)
*/
if (q->merge_bvec_fn) {
blk_queue_max_segments(mddev->queue, 1);
blk_queue_segment_boundary(mddev->queue,
PAGE_CACHE_SIZE - 1);
}
conf->working_disks++;
mddev->degraded--;
rdev->raid_disk = path;
set_bit(In_sync, &rdev->flags);
rcu_assign_pointer(p->rdev, rdev);
err = 0;
md_integrity_add_rdev(rdev, mddev);
break;
}
print_multipath_conf(conf);
return err;
}
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 (test_bit(In_sync, &rdev->flags) ||
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;
goto abort;
}
md_integrity_register(mddev);
}
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->private;
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 |= REQ_FAILFAST_TRANSPORT;
bio->bi_end_io = multipath_end_request;
bio->bi_private = mp_bh;
generic_make_request(bio);
}
}
spin_unlock_irqrestore(&conf->device_lock, flags);
}
static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
{
WARN_ONCE(sectors || raid_disks,
"%s does not support generic reshape\n", __func__);
return mddev->dev_sectors;
}
static int multipath_run (mddev_t *mddev)
{
multipath_conf_t *conf;
int disk_idx;
struct multipath_info *disk;
mdk_rdev_t *rdev;
if (md_check_no_bitmap(mddev))
return -EINVAL;
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()]
*/
mddev->queue->queue_lock = &mddev->queue->__queue_lock;
conf = kzalloc(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;
}
conf->multipaths = kzalloc(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;
}
conf->working_disks = 0;
list_for_each_entry(rdev, &mddev->disks, same_set) {
disk_idx = rdev->raid_disk;
if (disk_idx < 0 ||
disk_idx >= mddev->raid_disks)
continue;
disk = conf->multipaths + disk_idx;
disk->rdev = rdev;
disk_stack_limits(mddev->gendisk, rdev->bdev,
rdev->data_offset << 9);
/* 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) {
blk_queue_max_segments(mddev->queue, 1);
blk_queue_segment_boundary(mddev->queue,
PAGE_CACHE_SIZE - 1);
}
if (!test_bit(Faulty, &rdev->flags))
conf->working_disks++;
}
conf->raid_disks = mddev->raid_disks;
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_kmalloc_pool(NR_RESERVED_BUFS,
sizeof(struct multipath_bh));
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, NULL);
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
*/
md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
mddev->queue->unplug_fn = multipath_unplug;
mddev->queue->backing_dev_info.congested_fn = multipath_congested;
mddev->queue->backing_dev_info.congested_data = mddev;
md_integrity_register(mddev);
return 0;
out_free_conf:
if (conf->pool)
mempool_destroy(conf->pool);
kfree(conf->multipaths);
kfree(conf);
mddev->private = NULL;
out:
return -EIO;
}
static int multipath_stop (mddev_t *mddev)
{
multipath_conf_t *conf = mddev->private;
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 struct mdk_personality multipath_personality =
{
.name = "multipath",
.level = LEVEL_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,
.size = multipath_size,
};
static int __init multipath_init (void)
{
return register_md_personality (&multipath_personality);
}
static void __exit multipath_exit (void)
{
unregister_md_personality (&multipath_personality);
}
module_init(multipath_init);
module_exit(multipath_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("simple multi-path personality for MD");
MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
MODULE_ALIAS("md-multipath");
MODULE_ALIAS("md-level--4");