1 files changed, 584 insertions, 0 deletions

diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
new file mode 100644
index 000000000000..c9b134cd1532
--- /dev/null
+++ b/drivers/md/multipath.c
@@ -0,0 +1,584 @@
+/*
+ * 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_kernel();
+		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 */