diff options
Diffstat (limited to 'drivers/md/multipath.c')
-rw-r--r-- | drivers/md/multipath.c | 564 |
1 files changed, 564 insertions, 0 deletions
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c new file mode 100644 index 0000000..d4ac47d --- /dev/null +++ b/drivers/md/multipath.c @@ -0,0 +1,564 @@ +/* + * 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/raid/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_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, 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 = (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 (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); +} + +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 = 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 (struct request_queue *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; + const int rw = bio_data_dir(bio); + int cpu; + + if (unlikely(bio_barrier(bio))) { + bio_endio(bio, -EOPNOTSUPP); + return 0; + } + + mp_bh = mempool_alloc(conf->pool, GFP_NOIO); + + mp_bh->master_bio = bio; + mp_bh->mddev = mddev; + + 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(); + + 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 |= (1 << BIO_RW_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_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 && + 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_to_conf(mddev); + int i, ret = 0; + + 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_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 (!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; + blk_queue_stack_limits(mddev->queue, q); + + /* 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 (q->merge_bvec_fn && + mddev->queue->max_sectors > (PAGE_SIZE>>9)) + blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9); + + conf->working_disks++; + mddev->degraded--; + rdev->raid_disk = path; + set_bit(In_sync, &rdev->flags); + rcu_assign_pointer(p->rdev, rdev); + err = 0; + 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; + } + } +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_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 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()] + */ + 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; + rdev_for_each(rdev, tmp, mddev) { + 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 (!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_kzalloc_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, "%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_sectors = mddev->size * 2; + + mddev->queue->unplug_fn = multipath_unplug; + mddev->queue->backing_dev_info.congested_fn = multipath_congested; + mddev->queue->backing_dev_info.congested_data = 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_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 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, +}; + +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_ALIAS("md-personality-7"); /* MULTIPATH */ +MODULE_ALIAS("md-multipath"); +MODULE_ALIAS("md-level--4"); |