md-multipath.c 13 KB
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/*
 * 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.
 */

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#include <linux/blkdev.h>
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#include <linux/module.h>
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#include <linux/raid/md_u.h>
#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include "md.h"
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#include "md-multipath.h"
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#define MAX_WORK_PER_DISK 128

#define	NR_RESERVED_BUFS	32

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static int multipath_map (struct mpconf *conf)
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{
	int i, disks = conf->raid_disks;

	/*
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	 * Later we do read balancing on the read side
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	 * now we use the first available disk.
	 */

	rcu_read_lock();
	for (i = 0; i < disks; i++) {
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		struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
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		if (rdev && test_bit(In_sync, &rdev->flags) &&
		    !test_bit(Faulty, &rdev->flags)) {
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			atomic_inc(&rdev->nr_pending);
			rcu_read_unlock();
			return i;
		}
	}
	rcu_read_unlock();

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	pr_crit_ratelimited("multipath_map(): no more operational IO paths?\n");
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	return (-1);
}

static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
{
	unsigned long flags;
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	struct mddev *mddev = mp_bh->mddev;
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	struct mpconf *conf = mddev->private;
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	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.
 */
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static void multipath_end_bh_io(struct multipath_bh *mp_bh, blk_status_t status)
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{
	struct bio *bio = mp_bh->master_bio;
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	struct mpconf *conf = mp_bh->mddev->private;
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	bio->bi_status = status;
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	bio_endio(bio);
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	mempool_free(mp_bh, &conf->pool);
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}

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static void multipath_end_request(struct bio *bio)
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{
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	struct multipath_bh *mp_bh = bio->bi_private;
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	struct mpconf *conf = mp_bh->mddev->private;
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	struct md_rdev *rdev = conf->multipaths[mp_bh->path].rdev;
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	if (!bio->bi_status)
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		multipath_end_bh_io(mp_bh, 0);
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	else if (!(bio->bi_opf & REQ_RAHEAD)) {
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		/*
		 * oops, IO error:
		 */
		char b[BDEVNAME_SIZE];
		md_error (mp_bh->mddev, rdev);
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		pr_info("multipath: %s: rescheduling sector %llu\n",
			bdevname(rdev->bdev,b),
			(unsigned long long)bio->bi_iter.bi_sector);
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		multipath_reschedule_retry(mp_bh);
	} else
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		multipath_end_bh_io(mp_bh, bio->bi_status);
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	rdev_dec_pending(rdev, conf->mddev);
}

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static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
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{
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	struct mpconf *conf = mddev->private;
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	struct multipath_bh * mp_bh;
	struct multipath_info *multipath;

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	if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
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		md_flush_request(mddev, bio);
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		return true;
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	}

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	mp_bh = mempool_alloc(&conf->pool, GFP_NOIO);
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	mp_bh->master_bio = bio;
	mp_bh->mddev = mddev;

	mp_bh->path = multipath_map(conf);
	if (mp_bh->path < 0) {
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		bio_io_error(bio);
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		mempool_free(mp_bh, &conf->pool);
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		return true;
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	}
	multipath = conf->multipaths + mp_bh->path;

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	bio_init(&mp_bh->bio, NULL, 0);
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	__bio_clone_fast(&mp_bh->bio, bio);

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	mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
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	bio_set_dev(&mp_bh->bio, multipath->rdev->bdev);
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	mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT;
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	mp_bh->bio.bi_end_io = multipath_end_request;
	mp_bh->bio.bi_private = mp_bh;
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	mddev_check_writesame(mddev, &mp_bh->bio);
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	mddev_check_write_zeroes(mddev, &mp_bh->bio);
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	generic_make_request(&mp_bh->bio);
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	return true;
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}

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static void multipath_status(struct seq_file *seq, struct mddev *mddev)
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{
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	struct mpconf *conf = mddev->private;
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	int i;
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	seq_printf (seq, " [%d/%d] [", conf->raid_disks,
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		    conf->raid_disks - mddev->degraded);
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	rcu_read_lock();
	for (i = 0; i < conf->raid_disks; i++) {
		struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
		seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
	}
	rcu_read_unlock();
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	seq_putc(seq, ']');
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}

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static int multipath_congested(struct mddev *mddev, int bits)
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{
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	struct mpconf *conf = mddev->private;
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	int i, ret = 0;

	rcu_read_lock();
	for (i = 0; i < mddev->raid_disks ; i++) {
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		struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
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		if (rdev && !test_bit(Faulty, &rdev->flags)) {
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			struct request_queue *q = bdev_get_queue(rdev->bdev);
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			ret |= bdi_congested(q->backing_dev_info, bits);
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			/* Just like multipath_map, we just check the
			 * first available device
			 */
			break;
		}
	}
	rcu_read_unlock();
	return ret;
}
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/*
 * Careful, this can execute in IRQ contexts as well!
 */
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static void multipath_error (struct mddev *mddev, struct md_rdev *rdev)
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{
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	struct mpconf *conf = mddev->private;
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	char b[BDEVNAME_SIZE];
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	if (conf->raid_disks - mddev->degraded <= 1) {
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		/*
		 * 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.
		 */
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		pr_warn("multipath: only one IO path left and IO error.\n");
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		/* leave it active... it's all we have */
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		return;
	}
	/*
	 * Mark disk as unusable
	 */
	if (test_and_clear_bit(In_sync, &rdev->flags)) {
		unsigned long flags;
		spin_lock_irqsave(&conf->device_lock, flags);
		mddev->degraded++;
		spin_unlock_irqrestore(&conf->device_lock, flags);
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	}
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	set_bit(Faulty, &rdev->flags);
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	set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
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	pr_err("multipath: IO failure on %s, disabling IO path.\n"
	       "multipath: Operation continuing on %d IO paths.\n",
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	       bdevname(rdev->bdev, b),
	       conf->raid_disks - mddev->degraded);
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}

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static void print_multipath_conf (struct mpconf *conf)
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{
	int i;
	struct multipath_info *tmp;

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	pr_debug("MULTIPATH conf printout:\n");
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	if (!conf) {
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		pr_debug("(conf==NULL)\n");
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		return;
	}
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	pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
		 conf->raid_disks);
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	for (i = 0; i < conf->raid_disks; i++) {
		char b[BDEVNAME_SIZE];
		tmp = conf->multipaths + i;
		if (tmp->rdev)
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			pr_debug(" disk%d, o:%d, dev:%s\n",
				 i,!test_bit(Faulty, &tmp->rdev->flags),
				 bdevname(tmp->rdev->bdev,b));
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	}
}

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static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev)
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{
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	struct mpconf *conf = mddev->private;
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	int err = -EEXIST;
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	int path;
	struct multipath_info *p;
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	int first = 0;
	int last = mddev->raid_disks - 1;

	if (rdev->raid_disk >= 0)
		first = last = rdev->raid_disk;
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	print_multipath_conf(conf);

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	for (path = first; path <= last; path++)
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		if ((p=conf->multipaths+path)->rdev == NULL) {
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			disk_stack_limits(mddev->gendisk, rdev->bdev,
					  rdev->data_offset << 9);
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			err = md_integrity_add_rdev(rdev, mddev);
			if (err)
				break;
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			spin_lock_irq(&conf->device_lock);
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			mddev->degraded--;
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			rdev->raid_disk = path;
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			set_bit(In_sync, &rdev->flags);
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			spin_unlock_irq(&conf->device_lock);
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			rcu_assign_pointer(p->rdev, rdev);
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			err = 0;
			break;
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		}

	print_multipath_conf(conf);
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	return err;
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}

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static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
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{
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	struct mpconf *conf = mddev->private;
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	int err = 0;
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	int number = rdev->raid_disk;
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	struct multipath_info *p = conf->multipaths + number;

	print_multipath_conf(conf);

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	if (rdev == p->rdev) {
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		if (test_bit(In_sync, &rdev->flags) ||
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		    atomic_read(&rdev->nr_pending)) {
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			pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number);
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			err = -EBUSY;
			goto abort;
		}
		p->rdev = NULL;
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		if (!test_bit(RemoveSynchronized, &rdev->flags)) {
			synchronize_rcu();
			if (atomic_read(&rdev->nr_pending)) {
				/* lost the race, try later */
				err = -EBUSY;
				p->rdev = rdev;
				goto abort;
			}
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		}
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		err = md_integrity_register(mddev);
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	}
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.
 */

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static void multipathd(struct md_thread *thread)
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{
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	struct mddev *mddev = thread->mddev;
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	struct multipath_bh *mp_bh;
	struct bio *bio;
	unsigned long flags;
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	struct mpconf *conf = mddev->private;
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	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;
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		bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
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		if ((mp_bh->path = multipath_map (conf))<0) {
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			pr_err("multipath: %s: unrecoverable IO read error for block %llu\n",
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			       bio_devname(bio, b),
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			       (unsigned long long)bio->bi_iter.bi_sector);
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			multipath_end_bh_io(mp_bh, BLK_STS_IOERR);
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		} else {
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			pr_err("multipath: %s: redirecting sector %llu to another IO path\n",
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			       bio_devname(bio, b),
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			       (unsigned long long)bio->bi_iter.bi_sector);
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			*bio = *(mp_bh->master_bio);
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			bio->bi_iter.bi_sector +=
				conf->multipaths[mp_bh->path].rdev->data_offset;
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			bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev);
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			bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
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			bio->bi_end_io = multipath_end_request;
			bio->bi_private = mp_bh;
			generic_make_request(bio);
		}
	}
	spin_unlock_irqrestore(&conf->device_lock, flags);
}

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static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
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{
	WARN_ONCE(sectors || raid_disks,
		  "%s does not support generic reshape\n", __func__);

	return mddev->dev_sectors;
}

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static int multipath_run (struct mddev *mddev)
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{
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	struct mpconf *conf;
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	int disk_idx;
	struct multipath_info *disk;
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	struct md_rdev *rdev;
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	int working_disks;
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	int ret;
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	if (md_check_no_bitmap(mddev))
		return -EINVAL;

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	if (mddev->level != LEVEL_MULTIPATH) {
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		pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n",
			mdname(mddev), mddev->level);
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		goto out;
	}
	/*
	 * copy the already verified devices into our private MULTIPATH
	 * bookkeeping area. [whatever we allocate in multipath_run(),
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	 * should be freed in multipath_free()]
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	 */

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	conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
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	mddev->private = conf;
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	if (!conf)
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		goto out;

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	conf->multipaths = kcalloc(mddev->raid_disks,
				   sizeof(struct multipath_info),
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				   GFP_KERNEL);
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	if (!conf->multipaths)
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		goto out_free_conf;

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	working_disks = 0;
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	rdev_for_each(rdev, mddev) {
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		disk_idx = rdev->raid_disk;
		if (disk_idx < 0 ||
		    disk_idx >= mddev->raid_disks)
			continue;

		disk = conf->multipaths + disk_idx;
		disk->rdev = rdev;
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		disk_stack_limits(mddev->gendisk, rdev->bdev,
				  rdev->data_offset << 9);
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		if (!test_bit(Faulty, &rdev->flags))
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			working_disks++;
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	}

	conf->raid_disks = mddev->raid_disks;
	conf->mddev = mddev;
	spin_lock_init(&conf->device_lock);
	INIT_LIST_HEAD(&conf->retry_list);

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	if (!working_disks) {
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		pr_warn("multipath: no operational IO paths for %s\n",
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			mdname(mddev));
		goto out_free_conf;
	}
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	mddev->degraded = conf->raid_disks - working_disks;
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	ret = mempool_init_kmalloc_pool(&conf->pool, NR_RESERVED_BUFS,
					sizeof(struct multipath_bh));
	if (ret)
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		goto out_free_conf;

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	mddev->thread = md_register_thread(multipathd, mddev,
					   "multipath");
	if (!mddev->thread)
		goto out_free_conf;
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	pr_info("multipath: array %s active with %d out of %d IO paths\n",
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		mdname(mddev), conf->raid_disks - mddev->degraded,
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		mddev->raid_disks);
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	/*
	 * Ok, everything is just fine now
	 */
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	md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
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	if (md_integrity_register(mddev))
		goto out_free_conf;

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	return 0;

out_free_conf:
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	mempool_exit(&conf->pool);
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	kfree(conf->multipaths);
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	kfree(conf);
	mddev->private = NULL;
out:
	return -EIO;
}

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static void multipath_free(struct mddev *mddev, void *priv)
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{
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	struct mpconf *conf = priv;
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	mempool_exit(&conf->pool);
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	kfree(conf->multipaths);
	kfree(conf);
}

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static struct md_personality multipath_personality =
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{
	.name		= "multipath",
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	.level		= LEVEL_MULTIPATH,
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	.owner		= THIS_MODULE,
	.make_request	= multipath_make_request,
	.run		= multipath_run,
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	.free		= multipath_free,
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	.status		= multipath_status,
	.error_handler	= multipath_error,
	.hot_add_disk	= multipath_add_disk,
	.hot_remove_disk= multipath_remove_disk,
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	.size		= multipath_size,
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	.congested	= multipath_congested,
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};

static int __init multipath_init (void)
{
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	return register_md_personality (&multipath_personality);
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}

static void __exit multipath_exit (void)
{
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	unregister_md_personality (&multipath_personality);
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}

module_init(multipath_init);
module_exit(multipath_exit);
MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("simple multi-path personality for MD");
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MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
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MODULE_ALIAS("md-multipath");
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MODULE_ALIAS("md-level--4");