Move xen patchset to new version's subdir.

[ipfire-2.x.git] / src / patches / suse-2.6.27.31 / patches.suse / rq-based-multipath

From: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Subject: Request-based multipath patches
References: FATE#302108

This is the latest version of the request-based multipathing patches,
posted to dm-devel and linux-scsi on 03.10.2008.

Signed-off-by: Hannes Reinecke <hare@suse.de>

---
 drivers/md/dm-ioctl.c         |   13 
 drivers/md/dm-mpath.c         |  192 +++++---
 drivers/md/dm-table.c         |   82 +++
 drivers/md/dm.c               |  952 +++++++++++++++++++++++++++++++++++++++---
 drivers/md/dm.h               |   17 
 include/linux/device-mapper.h |   24 +
 6 files changed, 1158 insertions(+), 122 deletions(-)

--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -32,6 +32,7 @@ static unsigned int _major = 0;
 
 static DEFINE_SPINLOCK(_minor_lock);
 /*
+ * For bio based dm.
  * One of these is allocated per bio.
  */
 struct dm_io {
@@ -43,6 +44,7 @@ struct dm_io {
 };
 
 /*
+ * For bio based dm.
  * One of these is allocated per target within a bio.  Hopefully
  * this will be simplified out one day.
  */
@@ -52,6 +54,31 @@ struct dm_target_io {
 	union map_info info;
 };
 
+/*
+ * For request based dm.
+ * One of these is allocated per request.
+ *
+ * Since assuming "original request : cloned request = 1 : 1" and
+ * a counter for number of clones like struct dm_io.io_count isn't needed,
+ * struct dm_io and struct target_io can be merged.
+ */
+struct dm_rq_target_io {
+	struct mapped_device *md;
+	struct dm_target *ti;
+	struct request *orig, clone;
+	int error;
+	union map_info info;
+};
+
+/*
+ * For request based dm.
+ * One of these is allocated per bio.
+ */
+struct dm_clone_bio_info {
+	struct bio *orig;
+	struct request *rq;
+};
+
 union map_info *dm_get_mapinfo(struct bio *bio)
 {
 	if (bio && bio->bi_private)
@@ -59,6 +86,14 @@ union map_info *dm_get_mapinfo(struct bi
 	return NULL;
 }
 
+union map_info *dm_get_rq_mapinfo(struct request *rq)
+{
+	if (rq && rq->end_io_data)
+		return &((struct dm_rq_target_io *)rq->end_io_data)->info;
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(dm_get_rq_mapinfo);
+
 #define MINOR_ALLOCED ((void *)-1)
 
 /*
@@ -76,7 +111,6 @@ union map_info *dm_get_mapinfo(struct bi
  */
 struct dm_wq_req {
 	enum {
-		DM_WQ_FLUSH_ALL,
 		DM_WQ_FLUSH_DEFERRED,
 	} type;
 	struct work_struct work;
@@ -126,6 +160,8 @@ struct mapped_device {
 
 	struct bio_set *bs;
 
+	unsigned int mempool_type; /* Type of mempools above. */
+
 	/*
 	 * Event handling.
 	 */
@@ -143,52 +179,74 @@ struct mapped_device {
 
 	/* forced geometry settings */
 	struct hd_geometry geometry;
+
+	/* marker of flush suspend for request-based dm */
+	struct request suspend_rq;
+
+	/* For saving the address of __make_request for request based dm */
+	make_request_fn *saved_make_request_fn;
 };
 
 #define MIN_IOS 256
 static struct kmem_cache *_io_cache;
 static struct kmem_cache *_tio_cache;
+static struct kmem_cache *_rq_tio_cache;
+static struct kmem_cache *_bio_info_cache;
 
 static int __init local_init(void)
 {
-	int r;
+	int r = -ENOMEM;
 
 	/* allocate a slab for the dm_ios */
 	_io_cache = KMEM_CACHE(dm_io, 0);
 	if (!_io_cache)
-		return -ENOMEM;
+		return r;
 
 	/* allocate a slab for the target ios */
 	_tio_cache = KMEM_CACHE(dm_target_io, 0);
-	if (!_tio_cache) {
-		kmem_cache_destroy(_io_cache);
-		return -ENOMEM;
-	}
+	if (!_tio_cache)
+		goto out_free_io_cache;
+
+	_rq_tio_cache = KMEM_CACHE(dm_rq_target_io, 0);
+	if (!_rq_tio_cache)
+		goto out_free_tio_cache;
+
+	_bio_info_cache = KMEM_CACHE(dm_clone_bio_info, 0);
+	if (!_bio_info_cache)
+		goto out_free_rq_tio_cache;
 
 	r = dm_uevent_init();
-	if (r) {
-		kmem_cache_destroy(_tio_cache);
-		kmem_cache_destroy(_io_cache);
-		return r;
-	}
+	if (r)
+		goto out_free_bio_info_cache;
 
 	_major = major;
 	r = register_blkdev(_major, _name);
-	if (r < 0) {
-		kmem_cache_destroy(_tio_cache);
-		kmem_cache_destroy(_io_cache);
-		dm_uevent_exit();
-		return r;
-	}
+	if (r < 0)
+		goto out_uevent_exit;
 
 	if (!_major)
 		_major = r;
 
 	return 0;
+
+out_uevent_exit:
+	dm_uevent_exit();
+out_free_bio_info_cache:
+	kmem_cache_destroy(_bio_info_cache);
+out_free_rq_tio_cache:
+	kmem_cache_destroy(_rq_tio_cache);
+out_free_tio_cache:
+	kmem_cache_destroy(_tio_cache);
+out_free_io_cache:
+	kmem_cache_destroy(_io_cache);
+
+	return r;
 }
 
 static void local_exit(void)
 {
+	kmem_cache_destroy(_bio_info_cache);
+	kmem_cache_destroy(_rq_tio_cache);
 	kmem_cache_destroy(_tio_cache);
 	kmem_cache_destroy(_io_cache);
 	unregister_blkdev(_major, _name);
@@ -380,6 +438,28 @@ static void free_tio(struct mapped_devic
 	mempool_free(tio, md->tio_pool);
 }
 
+static inline struct dm_rq_target_io *alloc_rq_tio(struct mapped_device *md)
+{
+	return mempool_alloc(md->tio_pool, GFP_ATOMIC);
+}
+
+static inline void free_rq_tio(struct mapped_device *md,
+			       struct dm_rq_target_io *tio)
+{
+	mempool_free(tio, md->tio_pool);
+}
+
+static inline struct dm_clone_bio_info *alloc_bio_info(struct mapped_device *md)
+{
+	return mempool_alloc(md->io_pool, GFP_ATOMIC);
+}
+
+static inline void free_bio_info(struct mapped_device *md,
+				 struct dm_clone_bio_info *info)
+{
+	mempool_free(info, md->io_pool);
+}
+
 static void start_io_acct(struct dm_io *io)
 {
 	struct mapped_device *md = io->md;
@@ -568,6 +648,266 @@ static void clone_endio(struct bio *bio,
 	free_tio(md, tio);
 }
 
+/*
+ * Partial completion handling for request-based dm
+ */
+static void end_clone_bio(struct bio *clone, int error)
+{
+	struct dm_clone_bio_info *info = clone->bi_private;
+	struct dm_rq_target_io *tio = info->rq->end_io_data;
+	struct bio *bio = info->orig;
+	unsigned int nr_bytes = info->orig->bi_size;
+
+	free_bio_info(tio->md, info);
+	clone->bi_private = tio->md->bs;
+	bio_put(clone);
+
+	if (tio->error) {
+		/*
+		 * An error has already been detected on the request.
+		 * Once error occurred, just let clone->end_io() handle
+		 * the remainder.
+		 */
+		return;
+	} else if (error) {
+		/*
+		 * Don't notice the error to the upper layer yet.
+		 * The error handling decision is made by the target driver,
+		 * when the request is completed.
+		 */
+		tio->error = error;
+		return;
+	}
+
+	/*
+	 * I/O for the bio successfully completed.
+	 * Notice the data completion to the upper layer.
+	 */
+
+	/*
+	 * bios are processed from the head of the list.
+	 * So the completing bio should always be rq->bio.
+	 * If it's not, something wrong is happening.
+	 */
+	if (tio->orig->bio != bio)
+		DMERR("bio completion is going in the middle of the request");
+
+	/*
+	 * Update the original request.
+	 * Do not use blk_end_request() here, because it may complete
+	 * the original request before the clone, and break the ordering.
+	 */
+	blk_update_request(tio->orig, 0, nr_bytes);
+}
+
+static void free_bio_clone(struct request *clone)
+{
+	struct dm_rq_target_io *tio = clone->end_io_data;
+	struct mapped_device *md = tio->md;
+	struct bio *bio;
+	struct dm_clone_bio_info *info;
+
+	while ((bio = clone->bio) != NULL) {
+		clone->bio = bio->bi_next;
+
+		info = bio->bi_private;
+		free_bio_info(md, info);
+
+		bio->bi_private = md->bs;
+		bio_put(bio);
+	}
+}
+
+static void dec_rq_pending(struct dm_rq_target_io *tio)
+{
+	if (!atomic_dec_return(&tio->md->pending))
+		/* nudge anyone waiting on suspend queue */
+		wake_up(&tio->md->wait);
+}
+
+static void dm_unprep_request(struct request *rq)
+{
+	struct request *clone = rq->special;
+	struct dm_rq_target_io *tio = clone->end_io_data;
+
+	rq->special = NULL;
+	rq->cmd_flags &= ~REQ_DONTPREP;
+
+	free_bio_clone(clone);
+	dec_rq_pending(tio);
+	free_rq_tio(tio->md, tio);
+}
+
+/*
+ * Requeue the original request of a clone.
+ */
+void dm_requeue_request(struct request *clone)
+{
+	struct dm_rq_target_io *tio = clone->end_io_data;
+	struct request *rq = tio->orig;
+	struct request_queue *q = rq->q;
+	unsigned long flags;
+
+	dm_unprep_request(rq);
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	if (elv_queue_empty(q))
+		blk_plug_device(q);
+	blk_requeue_request(q, rq);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+EXPORT_SYMBOL_GPL(dm_requeue_request);
+
+static inline void __stop_queue(struct request_queue *q)
+{
+	blk_stop_queue(q);
+}
+
+static void stop_queue(struct request_queue *q)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	__stop_queue(q);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+static inline void __start_queue(struct request_queue *q)
+{
+	if (blk_queue_stopped(q))
+		blk_start_queue(q);
+}
+
+static void start_queue(struct request_queue *q)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	__start_queue(q);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+/*
+ * Complete the clone and the original request
+ */
+static void dm_end_request(struct request *clone, int error)
+{
+	struct dm_rq_target_io *tio = clone->end_io_data;
+	struct request *rq = tio->orig;
+	struct request_queue *q = rq->q;
+	unsigned int nr_bytes = blk_rq_bytes(rq);
+
+	if (blk_pc_request(rq)) {
+		rq->errors = clone->errors;
+		rq->data_len = clone->data_len;
+
+		if (rq->sense)
+			/*
+			 * We are using the sense buffer of the original
+			 * request.
+			 * So setting the length of the sense data is enough.
+			 */
+			rq->sense_len = clone->sense_len;
+	}
+
+	free_bio_clone(clone);
+	dec_rq_pending(tio);
+	free_rq_tio(tio->md, tio);
+
+	if (unlikely(blk_end_request(rq, error, nr_bytes)))
+		BUG();
+
+	blk_run_queue(q);
+}
+
+/*
+ * Request completion handler for request-based dm
+ */
+static void dm_softirq_done(struct request *rq)
+{
+	struct request *clone = rq->completion_data;
+	struct dm_rq_target_io *tio = clone->end_io_data;
+	dm_request_endio_fn rq_end_io = tio->ti->type->rq_end_io;
+	int error = tio->error;
+	int r;
+
+	if (rq->cmd_flags & REQ_FAILED)
+		goto end_request;
+
+	if (rq_end_io) {
+		r = rq_end_io(tio->ti, clone, error, &tio->info);
+		if (r <= 0)
+			/* The target wants to complete the I/O */
+			error = r;
+		else if (r == DM_ENDIO_INCOMPLETE)
+			/* The target will handle the I/O */
+			return;
+		else if (r == DM_ENDIO_REQUEUE) {
+			/*
+			 * The target wants to requeue the I/O.
+			 * Don't invoke blk_run_queue() so that the requeued
+			 * request won't be dispatched again soon.
+			 */
+			dm_requeue_request(clone);
+			return;
+		} else {
+			DMWARN("unimplemented target endio return value: %d",
+			       r);
+			BUG();
+		}
+	}
+
+end_request:
+	dm_end_request(clone, error);
+}
+
+/*
+ * Called with the queue lock held
+ */
+static void end_clone_request(struct request *clone, int error)
+{
+	struct dm_rq_target_io *tio = clone->end_io_data;
+	struct request *rq = tio->orig;
+
+	/*
+	 * For just cleaning up the information of the queue in which
+	 * the clone was dispatched.
+	 * The clone is *NOT* freed actually here because it is alloced from
+	 * dm own mempool and REQ_ALLOCED isn't set in clone->cmd_flags.
+	 */
+	__blk_put_request(clone->q, clone);
+
+	/*
+	 * Actual request completion is done in a softirq context which doesn't
+	 * hold the queue lock.  Otherwise, deadlock could occur because:
+	 *     - another request may be submitted by the upper level driver
+	 *       of the stacking during the completion
+	 *     - the submission which requires queue lock may be done
+	 *       against this queue
+	 */
+	tio->error = error;
+	rq->completion_data = clone;
+	blk_complete_request(rq);
+}
+
+/*
+ * Complete the original request of a clone with an error status.
+ * Target's rq_end_io() function isn't called.
+ * This may be used by target's map_rq() function when the mapping fails.
+ */
+void dm_kill_request(struct request *clone, int error)
+{
+	struct dm_rq_target_io *tio = clone->end_io_data;
+	struct request *rq = tio->orig;
+
+	tio->error = error;
+	/* Avoid printing "I/O error" message, since we didn't I/O actually */
+	rq->cmd_flags |= (REQ_FAILED | REQ_QUIET);
+	rq->completion_data = clone;
+	blk_complete_request(rq);
+}
+EXPORT_SYMBOL_GPL(dm_kill_request);
+
 static sector_t max_io_len(struct mapped_device *md,
 			   sector_t sector, struct dm_target *ti)
 {
@@ -886,7 +1226,7 @@ out:
  * The request function that just remaps the bio built up by
  * dm_merge_bvec.
  */
-static int dm_request(struct request_queue *q, struct bio *bio)
+static int _dm_request(struct request_queue *q, struct bio *bio)
 {
 	int r = -EIO;
 	int rw = bio_data_dir(bio);
@@ -936,12 +1276,335 @@ out_req:
 	return 0;
 }
 
+static int dm_make_request(struct request_queue *q, struct bio *bio)
+{
+	struct mapped_device *md = (struct mapped_device *)q->queuedata;
+
+	if (unlikely(bio_barrier(bio))) {
+		bio_endio(bio, -EOPNOTSUPP);
+		return 0;
+	}
+
+	if (unlikely(!md->map)) {
+		bio_endio(bio, -EIO);
+		return 0;
+	}
+
+	return md->saved_make_request_fn(q, bio); /* call __make_request() */
+}
+
+static inline int dm_request_based(struct mapped_device *md)
+{
+	return blk_queue_stackable(md->queue);
+}
+
+static int dm_request(struct request_queue *q, struct bio *bio)
+{
+	struct mapped_device *md = q->queuedata;
+
+	if (dm_request_based(md))
+		return dm_make_request(q, bio);
+
+	return _dm_request(q, bio);
+}
+
+void dm_dispatch_request(struct request *rq)
+{
+	int r;
+
+	rq->start_time = jiffies;
+	r = blk_insert_cloned_request(rq->q, rq);
+	if (r)
+		dm_kill_request(rq, r);
+}
+EXPORT_SYMBOL_GPL(dm_dispatch_request);
+
+static void copy_request_info(struct request *clone, struct request *rq)
+{
+	clone->cmd_flags = (rq_data_dir(rq) | REQ_NOMERGE);
+	clone->cmd_type = rq->cmd_type;
+	clone->sector = rq->sector;
+	clone->hard_sector = rq->hard_sector;
+	clone->nr_sectors = rq->nr_sectors;
+	clone->hard_nr_sectors = rq->hard_nr_sectors;
+	clone->current_nr_sectors = rq->current_nr_sectors;
+	clone->hard_cur_sectors = rq->hard_cur_sectors;
+	clone->nr_phys_segments = rq->nr_phys_segments;
+	clone->ioprio = rq->ioprio;
+	clone->buffer = rq->buffer;
+	clone->cmd_len = rq->cmd_len;
+	if (rq->cmd_len)
+		clone->cmd = rq->cmd;
+	clone->data_len = rq->data_len;
+	clone->extra_len = rq->extra_len;
+	clone->sense_len = rq->sense_len;
+	clone->data = rq->data;
+	clone->sense = rq->sense;
+}
+
+static int clone_request_bios(struct request *clone, struct request *rq,
+			      struct mapped_device *md)
+{
+	struct bio *bio, *clone_bio;
+	struct dm_clone_bio_info *info;
+
+	for (bio = rq->bio; bio; bio = bio->bi_next) {
+		info = alloc_bio_info(md);
+		if (!info)
+			goto free_and_out;
+
+		clone_bio = bio_alloc_bioset(GFP_ATOMIC, bio->bi_max_vecs,
+					     md->bs);
+		if (!clone_bio) {
+			free_bio_info(md, info);
+			goto free_and_out;
+		}
+
+		__bio_clone(clone_bio, bio);
+		clone_bio->bi_destructor = dm_bio_destructor;
+		clone_bio->bi_end_io = end_clone_bio;
+		info->rq = clone;
+		info->orig = bio;
+		clone_bio->bi_private = info;
+
+		if (clone->bio) {
+			clone->biotail->bi_next = clone_bio;
+			clone->biotail = clone_bio;
+		} else
+			clone->bio = clone->biotail = clone_bio;
+	}
+
+	return 0;
+
+free_and_out:
+	free_bio_clone(clone);
+
+	return -ENOMEM;
+}
+
+static int setup_clone(struct request *clone, struct request *rq,
+		       struct dm_rq_target_io *tio)
+{
+	int r;
+
+	blk_rq_init(NULL, clone);
+
+	r = clone_request_bios(clone, rq, tio->md);
+	if (r)
+		return r;
+
+	copy_request_info(clone, rq);
+	clone->start_time = jiffies;
+	clone->end_io = end_clone_request;
+	clone->end_io_data = tio;
+
+	return 0;
+}
+
+static inline int dm_flush_suspending(struct mapped_device *md)
+{
+	return !md->suspend_rq.data;
+}
+
+/*
+ * Called with the queue lock held.
+ */
+static int dm_prep_fn(struct request_queue *q, struct request *rq)
+{
+	struct mapped_device *md = (struct mapped_device *)q->queuedata;
+	struct dm_rq_target_io *tio;
+	struct request *clone;
+
+	if (unlikely(rq == &md->suspend_rq)) { /* Flush suspend marker */
+		if (dm_flush_suspending(md)) {
+			if (q->in_flight)
+				return BLKPREP_DEFER;
+			else {
+				/* This device should be quiet now */
+				__stop_queue(q);
+				smp_mb();
+				BUG_ON(atomic_read(&md->pending));
+				wake_up(&md->wait);
+				return BLKPREP_KILL;
+			}
+		} else
+			/*
+			 * The suspend process was interrupted.
+			 * So no need to suspend now.
+			 */
+			return BLKPREP_KILL;
+	}
+
+	if (unlikely(rq->special)) {
+		DMWARN("Already has something in rq->special.");
+		return BLKPREP_KILL;
+	}
+
+	if (unlikely(!dm_request_based(md))) {
+		DMWARN("Request was queued into bio-based device");
+		return BLKPREP_KILL;
+	}
+
+	tio = alloc_rq_tio(md); /* Only one for each original request */
+	if (!tio)
+		/* -ENOMEM */
+		return BLKPREP_DEFER;
+
+	tio->md = md;
+	tio->ti = NULL;
+	tio->orig = rq;
+	tio->error = 0;
+	memset(&tio->info, 0, sizeof(tio->info));
+
+	clone = &tio->clone;
+	if (setup_clone(clone, rq, tio)) {
+		/* -ENOMEM */
+		free_rq_tio(md, tio);
+		return BLKPREP_DEFER;
+	}
+
+	rq->special = clone;
+	rq->cmd_flags |= REQ_DONTPREP;
+
+	return BLKPREP_OK;
+}
+
+static void map_request(struct dm_target *ti, struct request *rq,
+			struct mapped_device *md)
+{
+	int r;
+	struct request *clone = rq->special;
+	struct dm_rq_target_io *tio = clone->end_io_data;
+
+	tio->ti = ti;
+	atomic_inc(&md->pending);
+
+	/*
+	 * Although submitted requests to the md->queue are checked against
+	 * the table/queue limitations at the submission time, the limitations
+	 * may be changed by a table swapping while those already checked
+	 * requests are in the md->queue.
+	 * If the limitations have been shrunk in such situations, we may be
+	 * dispatching requests violating the current limitations here.
+	 * Since struct request is a reliable one in the block-layer
+	 * and device drivers, dispatching such requests is dangerous.
+	 * (e.g. it may cause kernel panic easily.)
+	 * Avoid to dispatch such problematic requests in request-based dm.
+	 *
+	 * Since dm_kill_request() decrements the md->pending, this have to
+	 * be done after incrementing the md->pending.
+	 */
+	r = blk_rq_check_limits(rq->q, rq);
+	if (unlikely(r)) {
+		DMWARN("violating the queue limitation. the limitation may be"
+		       " shrunk while there are some requests in the queue.");
+		dm_kill_request(clone, r);
+		return;
+	}
+
+	r = ti->type->map_rq(ti, clone, &tio->info);
+	switch (r) {
+	case DM_MAPIO_SUBMITTED:
+		/* The target has taken the I/O to submit by itself later */
+		break;
+	case DM_MAPIO_REMAPPED:
+		/* The target has remapped the I/O so dispatch it */
+		dm_dispatch_request(clone);
+		break;
+	case DM_MAPIO_REQUEUE:
+		/* The target wants to requeue the I/O */
+		dm_requeue_request(clone);
+		break;
+	default:
+		if (r > 0) {
+			DMWARN("unimplemented target map return value: %d", r);
+			BUG();
+		}
+
+		/* The target wants to complete the I/O */
+		dm_kill_request(clone, r);
+		break;
+	}
+}
+
+/*
+ * q->request_fn for request-based dm.
+ * Called with the queue lock held.
+ */
+static void dm_request_fn(struct request_queue *q)
+{
+	struct mapped_device *md = (struct mapped_device *)q->queuedata;
+	struct dm_table *map = dm_get_table(md);
+	struct dm_target *ti;
+	struct request *rq;
+
+	/*
+	 * The check for blk_queue_stopped() needs here, because:
+	 *     - device suspend uses blk_stop_queue() and expects that
+	 *       no I/O will be dispatched any more after the queue stop
+	 *     - generic_unplug_device() doesn't call q->request_fn()
+	 *       when the queue is stopped, so no problem
+	 *     - but underlying device drivers may call q->request_fn()
+	 *       without the check through blk_run_queue()
+	 */
+	while (!blk_queue_plugged(q) && !blk_queue_stopped(q)) {
+		rq = elv_next_request(q);
+		if (!rq)
+			goto plug_and_out;
+
+		ti = dm_table_find_target(map, rq->sector);
+		if (ti->type->busy && ti->type->busy(ti))
+			goto plug_and_out;
+
+		blkdev_dequeue_request(rq);
+		spin_unlock(q->queue_lock);
+		map_request(ti, rq, md);
+		spin_lock_irq(q->queue_lock);
+	}
+
+	goto out;
+
+plug_and_out:
+	if (!elv_queue_empty(q))
+		/* Some requests still remain, retry later */
+		blk_plug_device(q);
+
+out:
+	dm_table_put(map);
+
+	return;
+}
+
+int dm_underlying_device_busy(struct request_queue *q)
+{
+	return blk_lld_busy(q);
+}
+EXPORT_SYMBOL_GPL(dm_underlying_device_busy);
+
+static int dm_lld_busy(struct request_queue *q)
+{
+	int r;
+	struct mapped_device *md = q->queuedata;
+	struct dm_table *map = dm_get_table(md);
+
+	if (!map || test_bit(DMF_BLOCK_IO, &md->flags))
+		r = 1;
+	else
+		r = dm_table_any_busy_target(map);
+
+	dm_table_put(map);
+	return r;
+}
+
 static void dm_unplug_all(struct request_queue *q)
 {
 	struct mapped_device *md = q->queuedata;
 	struct dm_table *map = dm_get_table(md);
 
 	if (map) {
+		if (dm_request_based(md))
+			generic_unplug_device(q);
+
 		dm_table_unplug_all(map);
 		dm_table_put(map);
 	}
@@ -955,6 +1618,12 @@ static int dm_any_congested(void *conges
 
 	if (!map || test_bit(DMF_BLOCK_IO, &md->flags))
 		r = bdi_bits;
+	else if (dm_request_based(md))
+		/*
+		 * Request-based dm cares about only own queue for
+		 * the query about congestion status of request_queue
+		 */
+		r = md->queue->backing_dev_info.state & bdi_bits;
 	else
 		r = dm_table_any_congested(map, bdi_bits);
 
@@ -1075,10 +1744,22 @@ static struct mapped_device *alloc_dev(i
 	INIT_LIST_HEAD(&md->uevent_list);
 	spin_lock_init(&md->uevent_lock);
 
-	md->queue = blk_alloc_queue(GFP_KERNEL);
+	md->queue = blk_init_queue(dm_request_fn, NULL);
 	if (!md->queue)
 		goto bad_queue;
 
+	/*
+	 * Request-based dm devices cannot be stacked on top of bio-based dm
+	 * devices.  The type of this dm device has not been decided yet,
+	 * although we initialized the queue using blk_init_queue().
+	 * The type is decided at the first table loading time.
+	 * To prevent problematic device stacking, clear the queue flag
+	 * for request stacking support until then.
+	 *
+	 * This queue is new, so no concurrency on the queue_flags.
+	 */
+	queue_flag_clear_unlocked(QUEUE_FLAG_STACKABLE, md->queue);
+	md->saved_make_request_fn = md->queue->make_request_fn;
 	md->queue->queuedata = md;
 	md->queue->backing_dev_info.congested_fn = dm_any_congested;
 	md->queue->backing_dev_info.congested_data = md;
@@ -1086,18 +1767,9 @@ static struct mapped_device *alloc_dev(i
 	blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
 	md->queue->unplug_fn = dm_unplug_all;
 	blk_queue_merge_bvec(md->queue, dm_merge_bvec);
-
-	md->io_pool = mempool_create_slab_pool(MIN_IOS, _io_cache);
-	if (!md->io_pool)
-		goto bad_io_pool;
-
-	md->tio_pool = mempool_create_slab_pool(MIN_IOS, _tio_cache);
-	if (!md->tio_pool)
-		goto bad_tio_pool;
-
-	md->bs = bioset_create(16, 16);
-	if (!md->bs)
-		goto bad_no_bioset;
+	blk_queue_softirq_done(md->queue, dm_softirq_done);
+	blk_queue_prep_rq(md->queue, dm_prep_fn);
+	blk_queue_lld_busy(md->queue, dm_lld_busy);
 
 	md->disk = alloc_disk(1);
 	if (!md->disk)
@@ -1132,12 +1804,6 @@ static struct mapped_device *alloc_dev(i
 bad_thread:
 	put_disk(md->disk);
 bad_disk:
-	bioset_free(md->bs);
-bad_no_bioset:
-	mempool_destroy(md->tio_pool);
-bad_tio_pool:
-	mempool_destroy(md->io_pool);
-bad_io_pool:
 	blk_cleanup_queue(md->queue);
 bad_queue:
 	free_minor(minor);
@@ -1159,9 +1825,12 @@ static void free_dev(struct mapped_devic
 		bdput(md->suspended_bdev);
 	}
 	destroy_workqueue(md->wq);
-	mempool_destroy(md->tio_pool);
-	mempool_destroy(md->io_pool);
-	bioset_free(md->bs);
+	if (md->tio_pool)
+		mempool_destroy(md->tio_pool);
+	if (md->io_pool)
+		mempool_destroy(md->io_pool);
+	if (md->bs)
+		bioset_free(md->bs);
 	del_gendisk(md->disk);
 	free_minor(minor);
 
@@ -1224,6 +1893,16 @@ static int __bind(struct mapped_device *
 	dm_table_get(t);
 	dm_table_event_callback(t, event_callback, md);
 
+	/*
+	 * The queue hasn't been stopped yet, if the old table type wasn't
+	 * for request-based during suspension.  So stop it to prevent
+	 * I/O mapping before resume.
+	 * This must be done before setting the queue restrictions,
+	 * because request-based dm may be run just after the setting.
+	 */
+	if (dm_table_request_based(t) && !blk_queue_stopped(q))
+		stop_queue(q);
+
 	write_lock(&md->map_lock);
 	md->map = t;
 	dm_table_set_restrictions(t, q);
@@ -1346,7 +2025,11 @@ static int dm_wait_for_completion(struct
 		set_current_state(TASK_INTERRUPTIBLE);
 
 		smp_mb();
-		if (!atomic_read(&md->pending))
+		if (dm_request_based(md)) {
+			if (!atomic_read(&md->pending) &&
+			    blk_queue_stopped(md->queue))
+				break;
+		} else if (!atomic_read(&md->pending))
 			break;
 
 		if (signal_pending(current)) {
@@ -1369,7 +2052,13 @@ static void __flush_deferred_io(struct m
 	struct bio *c;
 
 	while ((c = bio_list_pop(&md->deferred))) {
-		if (__split_bio(md, c))
+		/*
+		 * Some bios might have been queued here during suspension
+		 * before setting of request-based dm in resume
+		 */
+		if (dm_request_based(md))
+			generic_make_request(c);
+		else if (__split_bio(md, c))
 			bio_io_error(c);
 	}
 
@@ -1394,9 +2083,6 @@ static void dm_wq_work(struct work_struc
 
 	down_write(&md->io_lock);
 	switch (req->type) {
-	case DM_WQ_FLUSH_ALL:
-		__merge_pushback_list(md);
-		/* pass through */
 	case DM_WQ_FLUSH_DEFERRED:
 		__flush_deferred_io(md);
 		break;
@@ -1451,6 +2137,88 @@ out:
 	return r;
 }
 
+static inline void dm_invalidate_flush_suspend(struct mapped_device *md)
+{
+	md->suspend_rq.data = (void *)0x1;
+}
+
+static void dm_abort_suspend(struct mapped_device *md, int noflush)
+{
+	struct request_queue *q = md->queue;
+	unsigned long flags;
+
+	/*
+	 * For flush suspend, invalidation and queue restart must be protected
+	 * by a single queue lock to prevent a race with dm_prep_fn().
+	 */
+	spin_lock_irqsave(q->queue_lock, flags);
+	if (!noflush)
+		dm_invalidate_flush_suspend(md);
+	__start_queue(q);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+/*
+ * Additional suspend work for request-based dm.
+ *
+ * In request-based dm, stopping request_queue prevents mapping.
+ * Even after stopping the request_queue, submitted requests from upper-layer
+ * can be inserted to the request_queue.  So original (unmapped) requests are
+ * kept in the request_queue during suspension.
+ */
+static void dm_start_suspend(struct mapped_device *md, int noflush)
+{
+	struct request *rq = &md->suspend_rq;
+	struct request_queue *q = md->queue;
+	unsigned long flags;
+
+	if (noflush) {
+		stop_queue(q);
+		return;
+	}
+
+	/*
+	 * For flush suspend, we need a marker to indicate the border line
+	 * between flush needed I/Os and deferred I/Os, since all I/Os are
+	 * queued in the request_queue during suspension.
+	 *
+	 * This marker must be inserted after setting DMF_BLOCK_IO,
+	 * because dm_prep_fn() considers no DMF_BLOCK_IO to be
+	 * a suspend interruption.
+	 */
+	spin_lock_irqsave(q->queue_lock, flags);
+	if (unlikely(rq->ref_count)) {
+		/*
+		 * This can happen when the previous suspend was interrupted,
+		 * the inserted suspend_rq for the previous suspend has still
+		 * been in the queue and this suspend has been invoked.
+		 *
+		 * We could re-insert the suspend_rq by deleting it from
+		 * the queue forcibly using list_del_init(&rq->queuelist).
+		 * But it would break the block-layer easily.
+		 * So we don't re-insert the suspend_rq again in such a case.
+		 * The suspend_rq should be already invalidated during
+		 * the previous suspend interruption, so just wait for it
+		 * to be completed.
+		 *
+		 * This suspend will never complete, so warn the user to
+		 * interrupt this suspend and retry later.
+		 */
+		BUG_ON(!rq->data);
+		spin_unlock_irqrestore(q->queue_lock, flags);
+
+		DMWARN("Invalidating the previous suspend is still in"
+		       " progress.  This suspend will be never done."
+		       " Please interrupt this suspend and retry later.");
+		return;
+	}
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	/* Now no user of the suspend_rq */
+	blk_rq_init(q, rq);
+	blk_insert_request(q, rq, 0, NULL);
+}
+
 /*
  * Functions to lock and unlock any filesystem running on the
  * device.
@@ -1526,7 +2294,7 @@ int dm_suspend(struct mapped_device *md,
 		if (!md->suspended_bdev) {
 			DMWARN("bdget failed in dm_suspend");
 			r = -ENOMEM;
-			goto flush_and_out;
+			goto out;
 		}
 
 		/*
@@ -1549,6 +2317,9 @@ int dm_suspend(struct mapped_device *md,
 	add_wait_queue(&md->wait, &wait);
 	up_write(&md->io_lock);
 
+	if (dm_request_based(md))
+		dm_start_suspend(md, noflush);
+
 	/* unplug */
 	if (map)
 		dm_table_unplug_all(map);
@@ -1561,14 +2332,22 @@ int dm_suspend(struct mapped_device *md,
 	down_write(&md->io_lock);
 	remove_wait_queue(&md->wait, &wait);
 
-	if (noflush)
-		__merge_pushback_list(md);
+	if (noflush) {
+		if (dm_request_based(md))
+			/* All requeued requests are already in md->queue */
+			clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
+		else
+			__merge_pushback_list(md);
+	}
 	up_write(&md->io_lock);
 
 	/* were we interrupted ? */
 	if (r < 0) {
 		dm_queue_flush(md, DM_WQ_FLUSH_DEFERRED, NULL);
 
+		if (dm_request_based(md))
+			dm_abort_suspend(md, noflush);
+
 		unlock_fs(md);
 		goto out; /* pushback list is already flushed, so skip flush */
 	}
@@ -1577,14 +2356,6 @@ int dm_suspend(struct mapped_device *md,
 
 	set_bit(DMF_SUSPENDED, &md->flags);
 
-flush_and_out:
-	if (r && noflush)
-		/*
-		 * Because there may be already I/Os in the pushback list,
-		 * flush them before return.
-		 */
-		dm_queue_flush(md, DM_WQ_FLUSH_ALL, NULL);
-
 out:
 	if (r && md->suspended_bdev) {
 		bdput(md->suspended_bdev);
@@ -1617,6 +2388,14 @@ int dm_resume(struct mapped_device *md)
 
 	dm_queue_flush(md, DM_WQ_FLUSH_DEFERRED, NULL);
 
+	/*
+	 * Flushing deferred I/Os must be done after targets are resumed
+	 * so that mapping of targets can work correctly.
+	 * Request-based dm is queueing the deferred I/Os in its request_queue.
+	 */
+	if (dm_request_based(md))
+		start_queue(md->queue);
+
 	unlock_fs(md);
 
 	if (md->suspended_bdev) {
@@ -1698,6 +2477,65 @@ int dm_noflush_suspending(struct dm_targ
 }
 EXPORT_SYMBOL_GPL(dm_noflush_suspending);
 
+int dm_init_md_mempool(struct mapped_device *md, int type)
+{
+	if (unlikely(type == DM_TYPE_NONE)) {
+		DMWARN("no type is specified, can't initialize mempool");
+		return -EINVAL;
+	}
+
+	if (md->mempool_type == type)
+		return 0;
+
+	if (md->map) {
+		/* The md has been using, can't change the mempool type */
+		DMWARN("can't change mempool type after a table is bound");
+		return -EINVAL;
+	}
+
+	/* Not using the md yet, we can still change the mempool type */
+	if (md->mempool_type != DM_TYPE_NONE) {
+		mempool_destroy(md->io_pool);
+		md->io_pool = NULL;
+		mempool_destroy(md->tio_pool);
+		md->tio_pool = NULL;
+		bioset_free(md->bs);
+		md->bs = NULL;
+		md->mempool_type = DM_TYPE_NONE;
+	}
+
+	md->io_pool = (type == DM_TYPE_BIO_BASED) ?
+		      mempool_create_slab_pool(MIN_IOS, _io_cache) :
+		      mempool_create_slab_pool(MIN_IOS, _bio_info_cache);
+	if (!md->io_pool)
+		return -ENOMEM;
+
+	md->tio_pool = (type == DM_TYPE_BIO_BASED) ?
+		       mempool_create_slab_pool(MIN_IOS, _tio_cache) :
+		       mempool_create_slab_pool(MIN_IOS, _rq_tio_cache);
+	if (!md->tio_pool)
+		goto free_io_pool_and_out;
+
+	md->bs = (type == DM_TYPE_BIO_BASED) ?
+		 bioset_create(16, 16) : bioset_create(MIN_IOS, MIN_IOS);
+	if (!md->bs)
+		goto free_tio_pool_and_out;
+
+	md->mempool_type = type;
+
+	return 0;
+
+free_tio_pool_and_out:
+	mempool_destroy(md->tio_pool);
+	md->tio_pool = NULL;
+
+free_io_pool_and_out:
+	mempool_destroy(md->io_pool);
+	md->io_pool = NULL;
+
+	return -ENOMEM;
+}
+
 static struct block_device_operations dm_blk_dops = {
 	.open = dm_blk_open,
 	.release = dm_blk_close,
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -23,6 +23,13 @@
 #define DM_SUSPEND_NOFLUSH_FLAG		(1 << 1)
 
 /*
+ * Type of table and mapped_device's mempool
+ */
+#define DM_TYPE_NONE		0
+#define DM_TYPE_BIO_BASED	1
+#define DM_TYPE_REQUEST_BASED	2
+
+/*
  * List of devices that a metadevice uses and should open/close.
  */
 struct dm_dev {
@@ -49,6 +56,10 @@ void dm_table_presuspend_targets(struct 
 void dm_table_postsuspend_targets(struct dm_table *t);
 int dm_table_resume_targets(struct dm_table *t);
 int dm_table_any_congested(struct dm_table *t, int bdi_bits);
+int dm_table_any_busy_target(struct dm_table *t);
+int dm_table_set_type(struct dm_table *t);
+int dm_table_get_type(struct dm_table *t);
+int dm_table_request_based(struct dm_table *t);
 void dm_table_unplug_all(struct dm_table *t);
 
 /*
@@ -97,10 +108,16 @@ void *dm_vcalloc(unsigned long nmemb, un
 union map_info *dm_get_mapinfo(struct bio *bio);
 int dm_open_count(struct mapped_device *md);
 int dm_lock_for_deletion(struct mapped_device *md);
+union map_info *dm_get_rq_mapinfo(struct request *rq);
 
 void dm_kobject_uevent(struct mapped_device *md);
 
 int dm_kcopyd_init(void);
 void dm_kcopyd_exit(void);
 
+/*
+ * Mempool initializer for a mapped_device
+ */
+int dm_init_md_mempool(struct mapped_device *md, int type);
+
 #endif
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1046,6 +1046,12 @@ static int populate_table(struct dm_tabl
 		next = spec->next;
 	}
 
+	r = dm_table_set_type(table);
+	if (r) {
+		DMWARN("unable to set table type");
+		return r;
+	}
+
 	return dm_table_complete(table);
 }
 
@@ -1070,6 +1076,13 @@ static int table_load(struct dm_ioctl *p
 		goto out;
 	}
 
+	r = dm_init_md_mempool(md, dm_table_get_type(t));
+	if (r) {
+		DMWARN("unable to initialize the md mempools for this table");
+		dm_table_put(t);
+		goto out;
+	}
+
 	down_write(&_hash_lock);
 	hc = dm_get_mdptr(md);
 	if (!hc || hc->md != md) {
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -7,8 +7,6 @@
 
 #include "dm.h"
 #include "dm-path-selector.h"
-#include "dm-bio-list.h"
-#include "dm-bio-record.h"
 #include "dm-uevent.h"
 
 #include <linux/ctype.h>
@@ -83,7 +81,7 @@ struct multipath {
 	unsigned pg_init_count;		/* Number of times pg_init called */
 
 	struct work_struct process_queued_ios;
-	struct bio_list queued_ios;
+	struct list_head queued_ios;
 	unsigned queue_size;
 
 	struct work_struct trigger_event;
@@ -100,7 +98,6 @@ struct multipath {
  */
 struct dm_mpath_io {
 	struct pgpath *pgpath;
-	struct dm_bio_details details;
 };
 
 typedef int (*action_fn) (struct pgpath *pgpath);
@@ -197,6 +194,7 @@ static struct multipath *alloc_multipath
 	m = kzalloc(sizeof(*m), GFP_KERNEL);
 	if (m) {
 		INIT_LIST_HEAD(&m->priority_groups);
+		INIT_LIST_HEAD(&m->queued_ios);
 		spin_lock_init(&m->lock);
 		m->queue_io = 1;
 		INIT_WORK(&m->process_queued_ios, process_queued_ios);
@@ -321,12 +319,13 @@ static int __must_push_back(struct multi
 		dm_noflush_suspending(m->ti));
 }
 
-static int map_io(struct multipath *m, struct bio *bio,
+static int map_io(struct multipath *m, struct request *clone,
 		  struct dm_mpath_io *mpio, unsigned was_queued)
 {
 	int r = DM_MAPIO_REMAPPED;
 	unsigned long flags;
 	struct pgpath *pgpath;
+	struct block_device *bdev;
 
 	spin_lock_irqsave(&m->lock, flags);
 
@@ -343,16 +342,18 @@ static int map_io(struct multipath *m, s
 	if ((pgpath && m->queue_io) ||
 	    (!pgpath && m->queue_if_no_path)) {
 		/* Queue for the daemon to resubmit */
-		bio_list_add(&m->queued_ios, bio);
+		list_add_tail(&clone->queuelist, &m->queued_ios);
 		m->queue_size++;
 		if ((m->pg_init_required && !m->pg_init_in_progress) ||
 		    !m->queue_io)
 			queue_work(kmultipathd, &m->process_queued_ios);
 		pgpath = NULL;
 		r = DM_MAPIO_SUBMITTED;
-	} else if (pgpath)
-		bio->bi_bdev = pgpath->path.dev->bdev;
-	else if (__must_push_back(m))
+	} else if (pgpath) {
+		bdev = pgpath->path.dev->bdev;
+		clone->q = bdev_get_queue(bdev);
+		clone->rq_disk = bdev->bd_disk;
+	} else if (__must_push_back(m))
 		r = DM_MAPIO_REQUEUE;
 	else
 		r = -EIO;	/* Failed */
@@ -395,30 +396,31 @@ static void dispatch_queued_ios(struct m
 {
 	int r;
 	unsigned long flags;
-	struct bio *bio = NULL, *next;
 	struct dm_mpath_io *mpio;
 	union map_info *info;
+	struct request *clone, *n;
+	LIST_HEAD(cl);
 
 	spin_lock_irqsave(&m->lock, flags);
-	bio = bio_list_get(&m->queued_ios);
+	list_splice_init(&m->queued_ios, &cl);
 	spin_unlock_irqrestore(&m->lock, flags);
 
-	while (bio) {
-		next = bio->bi_next;
-		bio->bi_next = NULL;
+	list_for_each_entry_safe(clone, n, &cl, queuelist) {
+		list_del_init(&clone->queuelist);
 
-		info = dm_get_mapinfo(bio);
+		info = dm_get_rq_mapinfo(clone);
 		mpio = info->ptr;
 
-		r = map_io(m, bio, mpio, 1);
-		if (r < 0)
-			bio_endio(bio, r);
-		else if (r == DM_MAPIO_REMAPPED)
-			generic_make_request(bio);
-		else if (r == DM_MAPIO_REQUEUE)
-			bio_endio(bio, -EIO);
-
-		bio = next;
+		r = map_io(m, clone, mpio, 1);
+		if (r < 0) {
+			mempool_free(mpio, m->mpio_pool);
+			dm_kill_request(clone, r);
+		} else if (r == DM_MAPIO_REMAPPED)
+			dm_dispatch_request(clone);
+		else if (r == DM_MAPIO_REQUEUE) {
+			mempool_free(mpio, m->mpio_pool);
+			dm_requeue_request(clone);
+		}
 	}
 }
 
@@ -833,21 +835,24 @@ static void multipath_dtr(struct dm_targ
 }
 
 /*
- * Map bios, recording original fields for later in case we have to resubmit
+ * Map cloned requests
  */
-static int multipath_map(struct dm_target *ti, struct bio *bio,
+static int multipath_map(struct dm_target *ti, struct request *clone,
 			 union map_info *map_context)
 {
 	int r;
 	struct dm_mpath_io *mpio;
 	struct multipath *m = (struct multipath *) ti->private;
 
-	mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
-	dm_bio_record(&mpio->details, bio);
+	mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
+	if (!mpio)
+		/* ENOMEM, requeue */
+		return DM_MAPIO_REQUEUE;
+	memset(mpio, 0, sizeof(*mpio));
 
 	map_context->ptr = mpio;
-	bio->bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
-	r = map_io(m, bio, mpio, 0);
+	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
+	r = map_io(m, clone, mpio, 0);
 	if (r < 0 || r == DM_MAPIO_REQUEUE)
 		mempool_free(mpio, m->mpio_pool);
 
@@ -1129,53 +1134,41 @@ static void activate_path(struct work_st
 /*
  * end_io handling
  */
-static int do_end_io(struct multipath *m, struct bio *bio,
+static int do_end_io(struct multipath *m, struct request *clone,
 		     int error, struct dm_mpath_io *mpio)
 {
+	/*
+	 * We don't queue any clone request inside the multipath target
+	 * during end I/O handling, since those clone requests don't have
+	 * bio clones.  If we queue them inside the multipath target,
+	 * we need to make bio clones, that requires memory allocation.
+	 * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
+	 *  don't have bio clones.)
+	 * Instead of queueing the clone request here, we queue the original
+	 * request into dm core, which will remake a clone request and
+	 * clone bios for it and resubmit it later.
+	 */
+	int r = DM_ENDIO_REQUEUE;
 	unsigned long flags;
 
-	if (!error)
+	if (!error && !clone->errors)
 		return 0;	/* I/O complete */
 
-	if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
-		return error;
-
 	if (error == -EOPNOTSUPP)
 		return error;
 
-	spin_lock_irqsave(&m->lock, flags);
-	if (!m->nr_valid_paths) {
-		if (__must_push_back(m)) {
-			spin_unlock_irqrestore(&m->lock, flags);
-			return DM_ENDIO_REQUEUE;
-		} else if (!m->queue_if_no_path) {
-			spin_unlock_irqrestore(&m->lock, flags);
-			return -EIO;
-		} else {
-			spin_unlock_irqrestore(&m->lock, flags);
-			goto requeue;
-		}
-	}
-	spin_unlock_irqrestore(&m->lock, flags);
-
 	if (mpio->pgpath)
 		fail_path(mpio->pgpath);
 
-      requeue:
-	dm_bio_restore(&mpio->details, bio);
-
-	/* queue for the daemon to resubmit or fail */
 	spin_lock_irqsave(&m->lock, flags);
-	bio_list_add(&m->queued_ios, bio);
-	m->queue_size++;
-	if (!m->queue_io)
-		queue_work(kmultipathd, &m->process_queued_ios);
+	if (!m->nr_valid_paths && !m->queue_if_no_path && !__must_push_back(m))
+		r = -EIO;
 	spin_unlock_irqrestore(&m->lock, flags);
 
-	return DM_ENDIO_INCOMPLETE;	/* io not complete */
+	return r;
 }
 
-static int multipath_end_io(struct dm_target *ti, struct bio *bio,
+static int multipath_end_io(struct dm_target *ti, struct request *clone,
 			    int error, union map_info *map_context)
 {
 	struct multipath *m = ti->private;
@@ -1184,14 +1177,13 @@ static int multipath_end_io(struct dm_ta
 	struct path_selector *ps;
 	int r;
 
-	r  = do_end_io(m, bio, error, mpio);
+	r  = do_end_io(m, clone, error, mpio);
 	if (pgpath) {
 		ps = &pgpath->pg->ps;
 		if (ps->type->end_io)
 			ps->type->end_io(ps, &pgpath->path);
 	}
-	if (r != DM_ENDIO_INCOMPLETE)
-		mempool_free(mpio, m->mpio_pool);
+	mempool_free(mpio, m->mpio_pool);
 
 	return r;
 }
@@ -1427,6 +1419,75 @@ static int multipath_ioctl(struct dm_tar
 					 bdev->bd_disk, cmd, arg);
 }
 
+static int __pgpath_busy(struct pgpath *pgpath)
+{
+	struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
+
+	return dm_underlying_device_busy(q);
+}
+
+/*
+ * We return "busy", only when we can map I/Os but underlying devices
+ * are busy (so even if we map I/Os now, the I/Os will wait on
+ * the underlying queue).
+ * In other words, if we want to kill I/Os or queue them inside us
+ * due to map unavailability, we don't return "busy".  Otherwise,
+ * dm core won't give us the I/Os and we can't do what we want.
+ */
+static int multipath_busy(struct dm_target *ti)
+{
+	int busy = 0, has_active = 0;
+	struct multipath *m = (struct multipath *) ti->private;
+	struct priority_group *pg;
+	struct pgpath *pgpath;
+	unsigned long flags;
+
+	spin_lock_irqsave(&m->lock, flags);
+
+	/* Guess which priority_group will be used at next mapping time */
+	if (unlikely(!m->current_pgpath && m->next_pg))
+		pg = m->next_pg;
+	else if (likely(m->current_pg))
+		pg = m->current_pg;
+	else
+		/*
+		 * We don't know which pg will be used at next mapping time.
+		 * We don't call __choose_pgpath() here to avoid to trigger
+		 * pg_init just by busy checking.
+		 * So we don't know whether underlying devices we will be using
+		 * at next mapping time are busy or not. Just try mapping.
+		 */
+		goto out;
+
+	/*
+	 * If there is one non-busy active path at least, the path selector
+	 * will be able to select it. So we consider such a pg as not busy.
+	 */
+	busy = 1;
+	list_for_each_entry(pgpath, &pg->pgpaths, list)
+		if (pgpath->is_active) {
+			has_active = 1;
+
+			if (!__pgpath_busy(pgpath)) {
+				busy = 0;
+				break;
+			}
+		}
+
+	if (!has_active)
+		/*
+		 * No active path in this pg, so this pg won't be used and
+		 * the current_pg will be changed at next mapping time.
+		 * We need to try mapping to determine it.
+		 */
+		busy = 0;
+
+out:
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	return busy;
+}
+
 /*-----------------------------------------------------------------
  * Module setup
  *---------------------------------------------------------------*/
@@ -1436,13 +1497,14 @@ static struct target_type multipath_targ
 	.module = THIS_MODULE,
 	.ctr = multipath_ctr,
 	.dtr = multipath_dtr,
-	.map = multipath_map,
-	.end_io = multipath_end_io,
+	.map_rq = multipath_map,
+	.rq_end_io = multipath_end_io,
 	.presuspend = multipath_presuspend,
 	.resume = multipath_resume,
 	.status = multipath_status,
 	.message = multipath_message,
 	.ioctl  = multipath_ioctl,
+	.busy = multipath_busy,
 };
 
 static int __init dm_multipath_init(void)
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -108,6 +108,8 @@ static void combine_restrictions_low(str
 	lhs->bounce_pfn = min_not_zero(lhs->bounce_pfn, rhs->bounce_pfn);
 
 	lhs->no_cluster |= rhs->no_cluster;
+
+	lhs->no_request_stacking |= rhs->no_request_stacking;
 }
 
 /*
@@ -522,6 +524,8 @@ void dm_set_device_limits(struct dm_targ
 	rs->bounce_pfn = min_not_zero(rs->bounce_pfn, q->bounce_pfn);
 
 	rs->no_cluster |= !test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
+
+	rs->no_request_stacking |= !blk_queue_stackable(q);
 }
 EXPORT_SYMBOL_GPL(dm_set_device_limits);
 
@@ -731,6 +735,66 @@ int dm_table_add_target(struct dm_table 
 	return r;
 }
 
+int dm_table_set_type(struct dm_table *t)
+{
+	int i;
+	int bio_based = 0, request_based = 0;
+	struct dm_target *tgt;
+
+	for (i = 0; i < t->num_targets; i++) {
+		tgt = t->targets + i;
+		if (tgt->type->map_rq)
+			request_based = 1;
+		else
+			bio_based = 1;
+
+		if (bio_based && request_based) {
+			DMWARN("Inconsistent table: different target types"
+			       " can't be mixed up");
+			return -EINVAL;
+		}
+	}
+
+	if (bio_based) {
+		/* We must use this table as bio-based */
+		t->limits.no_request_stacking = 1;
+		return 0;
+	}
+
+	BUG_ON(!request_based); /* No targets in this table */
+
+	/* Non-request-stackable devices can't be used for request-based dm */
+	if (t->limits.no_request_stacking) {
+		DMWARN("table load rejected: including non-request-stackable"
+		       " devices");
+		return -EINVAL;
+	}
+
+	/*
+	 * Request-based dm supports only tables that have a single target now.
+	 * To support multiple targets, request splitting support is needed,
+	 * and that needs lots of changes in the block-layer.
+	 * (e.g. request completion process for partial completion.)
+	 */
+	if (t->num_targets > 1) {
+		DMWARN("Request-based dm doesn't support multiple targets yet");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int dm_table_get_type(struct dm_table *t)
+{
+	return t->limits.no_request_stacking ?
+		DM_TYPE_BIO_BASED : DM_TYPE_REQUEST_BASED;
+}
+
+int dm_table_request_based(struct dm_table *t)
+{
+	return dm_table_get_type(t) == DM_TYPE_REQUEST_BASED;
+}
+
 static int setup_indexes(struct dm_table *t)
 {
 	int i;
@@ -861,6 +925,10 @@ void dm_table_set_restrictions(struct dm
 	else
 		queue_flag_set_unlocked(QUEUE_FLAG_CLUSTER, q);
 
+	if (t->limits.no_request_stacking)
+		queue_flag_clear_unlocked(QUEUE_FLAG_STACKABLE, q);
+	else
+		queue_flag_set_unlocked(QUEUE_FLAG_STACKABLE, q);
 }
 
 unsigned int dm_table_get_num_targets(struct dm_table *t)
@@ -949,6 +1017,20 @@ int dm_table_any_congested(struct dm_tab
 	return r;
 }
 
+int dm_table_any_busy_target(struct dm_table *t)
+{
+	int i;
+	struct dm_target *ti;
+
+	for (i = 0; i < t->num_targets; i++) {
+		ti = t->targets + i;
+		if (ti->type->busy && ti->type->busy(ti))
+			return 1;
+	}
+
+	return 0;
+}
+
 void dm_table_unplug_all(struct dm_table *t)
 {
 	struct dm_dev *dd;
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -46,6 +46,8 @@ typedef void (*dm_dtr_fn) (struct dm_tar
  */
 typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio,
 			  union map_info *map_context);
+typedef int (*dm_map_request_fn) (struct dm_target *ti, struct request *clone,
+				  union map_info *map_context);
 
 /*
  * Returns:
@@ -58,6 +60,9 @@ typedef int (*dm_map_fn) (struct dm_targ
 typedef int (*dm_endio_fn) (struct dm_target *ti,
 			    struct bio *bio, int error,
 			    union map_info *map_context);
+typedef int (*dm_request_endio_fn) (struct dm_target *ti,
+				    struct request *clone, int error,
+				    union map_info *map_context);
 
 typedef void (*dm_flush_fn) (struct dm_target *ti);
 typedef void (*dm_presuspend_fn) (struct dm_target *ti);
@@ -77,6 +82,13 @@ typedef int (*dm_ioctl_fn) (struct dm_ta
 typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
 			    struct bio_vec *biovec, int max_size);
 
+/*
+ * Returns:
+ *    0: The target can handle the next I/O immediately.
+ *    1: The target can't handle the next I/O immediately.
+ */
+typedef int (*dm_busy_fn) (struct dm_target *ti);
+
 void dm_error(const char *message);
 
 /*
@@ -103,7 +115,9 @@ struct target_type {
 	dm_ctr_fn ctr;
 	dm_dtr_fn dtr;
 	dm_map_fn map;
+	dm_map_request_fn map_rq;
 	dm_endio_fn end_io;
+	dm_request_endio_fn rq_end_io;
 	dm_flush_fn flush;
 	dm_presuspend_fn presuspend;
 	dm_postsuspend_fn postsuspend;
@@ -113,6 +127,7 @@ struct target_type {
 	dm_message_fn message;
 	dm_ioctl_fn ioctl;
 	dm_merge_fn merge;
+	dm_busy_fn busy;
 };
 
 struct io_restrictions {
@@ -125,6 +140,7 @@ struct io_restrictions {
 	unsigned short max_hw_segments;
 	unsigned short max_phys_segments;
 	unsigned char no_cluster; /* inverted so that 0 is default */
+	unsigned char no_request_stacking;
 };
 
 struct dm_target {
@@ -348,4 +364,12 @@ static inline unsigned long to_bytes(sec
 	return (n << SECTOR_SHIFT);
 }
 
+/*-----------------------------------------------------------------
+ * Helper for block layer and dm core operations
+ *---------------------------------------------------------------*/
+void dm_dispatch_request(struct request *rq);
+void dm_requeue_request(struct request *rq);
+void dm_kill_request(struct request *rq, int error);
+int dm_underlying_device_busy(struct request_queue *q);
+
 #endif	/* _LINUX_DEVICE_MAPPER_H */