1 files changed, 544 insertions, 0 deletions

diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
new file mode 100644
index 000000000..ac3ede2bd
--- /dev/null
+++ b/drivers/md/multipath.c
@@ -0,0 +1,544 @@
+/*
+ * 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/module.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 (struct mpconf *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++) {
+		struct md_rdev *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;
+	struct mddev *mddev = mp_bh->mddev;
+	struct mpconf *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;
+	struct mpconf *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;
+	struct mpconf *conf = mp_bh->mddev->private;
+	struct md_rdev *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_iter.bi_sector);
+		multipath_reschedule_retry(mp_bh);
+	} else
+		multipath_end_bh_io(mp_bh, error);
+	rdev_dec_pending(rdev, conf->mddev);
+}
+
+static void multipath_make_request(struct mddev *mddev, struct bio * bio)
+{
+	struct mpconf *conf = mddev->private;
+	struct multipath_bh * mp_bh;
+	struct multipath_info *multipath;
+
+	if (unlikely(bio->bi_rw & REQ_FLUSH)) {
+		md_flush_request(mddev, bio);
+		return;
+	}
+
+	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;
+	}
+	multipath = conf->multipaths + mp_bh->path;
+
+	mp_bh->bio = *bio;
+	mp_bh->bio.bi_iter.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;
+}
+
+static void multipath_status (struct seq_file *seq, struct mddev *mddev)
+{
+	struct mpconf *conf = mddev->private;
+	int i;
+
+	seq_printf (seq, " [%d/%d] [", conf->raid_disks,
+		    conf->raid_disks - mddev->degraded);
+	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(struct mddev *mddev, int bits)
+{
+	struct mpconf *conf = mddev->private;
+	int i, ret = 0;
+
+	rcu_read_lock();
+	for (i = 0; i < mddev->raid_disks ; i++) {
+		struct md_rdev *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 (struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct mpconf *conf = mddev->private;
+	char b[BDEVNAME_SIZE];
+
+	if (conf->raid_disks - mddev->degraded <= 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 */
+		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);
+	}
+	set_bit(Faulty, &rdev->flags);
+	set_bit(MD_CHANGE_DEVS, &mddev->flags);
+	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->raid_disks - mddev->degraded);
+}
+
+static void print_multipath_conf (struct mpconf *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->raid_disks - conf->mddev->degraded,
+			 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(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct mpconf *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);
+			}
+
+			spin_lock_irq(&conf->device_lock);
+			mddev->degraded--;
+			rdev->raid_disk = path;
+			set_bit(In_sync, &rdev->flags);
+			spin_unlock_irq(&conf->device_lock);
+			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(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct mpconf *conf = mddev->private;
+	int err = 0;
+	int number = rdev->raid_disk;
+	struct multipath_info *p = conf->multipaths + number;
+
+	print_multipath_conf(conf);
+
+	if (rdev == p->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;
+		}
+		err = 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(struct md_thread *thread)
+{
+	struct mddev *mddev = thread->mddev;
+	struct multipath_bh *mp_bh;
+	struct bio *bio;
+	unsigned long flags;
+	struct mpconf *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_iter.bi_sector = mp_bh->master_bio->bi_iter.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_iter.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_iter.bi_sector);
+			*bio = *(mp_bh->master_bio);
+			bio->bi_iter.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(struct mddev *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 (struct mddev *mddev)
+{
+	struct mpconf *conf;
+	int disk_idx;
+	struct multipath_info *disk;
+	struct md_rdev *rdev;
+	int working_disks;
+
+	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_free()]
+	 */
+
+	conf = kzalloc(sizeof(struct mpconf), 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;
+	}
+
+	working_disks = 0;
+	rdev_for_each(rdev, mddev) {
+		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))
+			working_disks++;
+	}
+
+	conf->raid_disks = mddev->raid_disks;
+	conf->mddev = mddev;
+	spin_lock_init(&conf->device_lock);
+	INIT_LIST_HEAD(&conf->retry_list);
+
+	if (!working_disks) {
+		printk(KERN_ERR "multipath: no operational IO paths for %s\n",
+			mdname(mddev));
+		goto out_free_conf;
+	}
+	mddev->degraded = conf->raid_disks - 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,
+						   "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->raid_disks - mddev->degraded,
+	       mddev->raid_disks);
+	/*
+	 * Ok, everything is just fine now
+	 */
+	md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
+
+	if (md_integrity_register(mddev))
+		goto out_free_conf;
+
+	return 0;
+
+out_free_conf:
+	if (conf->pool)
+		mempool_destroy(conf->pool);
+	kfree(conf->multipaths);
+	kfree(conf);
+	mddev->private = NULL;
+out:
+	return -EIO;
+}
+
+static void multipath_free(struct mddev *mddev, void *priv)
+{
+	struct mpconf *conf = priv;
+
+	mempool_destroy(conf->pool);
+	kfree(conf->multipaths);
+	kfree(conf);
+}
+
+static struct md_personality multipath_personality =
+{
+	.name		= "multipath",
+	.level		= LEVEL_MULTIPATH,
+	.owner		= THIS_MODULE,
+	.make_request	= multipath_make_request,
+	.run		= multipath_run,
+	.free		= multipath_free,
+	.status		= multipath_status,
+	.error_handler	= multipath_error,
+	.hot_add_disk	= multipath_add_disk,
+	.hot_remove_disk= multipath_remove_disk,
+	.size		= multipath_size,
+	.congested	= multipath_congested,
+};
+
+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");