Merge tag 'dm-4.8-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper updates from Mike Snitzer:

 - initially based on Jens' 'for-4.8/core' (given all the flag churn)
   and later merged with 'for-4.8/core' to pickup the QUEUE_FLAG_DAX
   commits that DM depends on to provide its DAX support

 - clean up the bio-based vs request-based DM core code by moving the
   request-based DM core code out to dm-rq.[hc]

 - reinstate bio-based support in the DM multipath target (done with the
   idea that fast storage like NVMe over Fabrics could benefit) -- while
   preserving support for request_fn and blk-mq request-based DM mpath

 - SCSI and DM multipath persistent reservation fixes that were
   coordinated with Martin Petersen.

 - the DM raid target saw the most extensive change this cycle; it now
   provides reshape and takeover support (by layering ontop of the
   corresponding MD capabilities)

 - DAX support for DM core and the linear, stripe and error targets

 - a DM thin-provisioning block discard vs allocation race fix that
   addresses potential for corruption

 - a stable fix for DM verity-fec's block calculation during decode

 - a few cleanups and fixes to DM core and various targets

* tag 'dm-4.8-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (73 commits)
  dm: allow bio-based table to be upgraded to bio-based with DAX support
  dm snap: add fake origin_direct_access
  dm stripe: add DAX support
  dm error: add DAX support
  dm linear: add DAX support
  dm: add infrastructure for DAX support
  dm thin: fix a race condition between discarding and provisioning a block
  dm btree: fix a bug in dm_btree_find_next_single()
  dm raid: fix random optimal_io_size for raid0
  dm raid: address checkpatch.pl complaints
  dm: call PR reserve/unreserve on each underlying device
  sd: don't use the ALL_TG_PT bit for reservations
  dm: fix second blk_delay_queue() parameter to be in msec units not jiffies
  dm raid: change logical functions to actually return bool
  dm raid: use rdev_for_each in status
  dm raid: use rs->raid_disks to avoid memory leaks on free
  dm raid: support delta_disks for raid1, fix table output
  dm raid: enhance reshape check and factor out reshape setup
  dm raid: allow resize during recovery
  dm raid: fix rs_is_recovering() to allow for lvextend
  ...

26 files changed, 4395 insertions, 1810 deletions

diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 52ba8dd82821..3cbda1af87a0 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -3,7 +3,8 @@
 #
 
 dm-mod-y	+= dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
-		   dm-ioctl.o dm-io.o dm-kcopyd.o dm-sysfs.o dm-stats.o
+		   dm-ioctl.o dm-io.o dm-kcopyd.o dm-sysfs.o dm-stats.o \
+		   dm-rq.o
 dm-multipath-y	+= dm-path-selector.o dm-mpath.o
 dm-snapshot-y	+= dm-snap.o dm-exception-store.o dm-snap-transient.o \
 		    dm-snap-persistent.o
diff --git a/drivers/md/dm-builtin.c b/drivers/md/dm-builtin.c
index 6c9049c51b2b..f092771878c2 100644
--- a/drivers/md/dm-builtin.c
+++ b/drivers/md/dm-builtin.c
@@ -1,4 +1,4 @@
-#include "dm.h"
+#include "dm-core.h"
 
 /*
  * The kobject release method must not be placed in the module itself,
diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
new file mode 100644
index 000000000000..40ceba1fe8be
--- /dev/null
+++ b/drivers/md/dm-core.h
@@ -0,0 +1,149 @@
+/*
+ * Internal header file _only_ for device mapper core
+ *
+ * Copyright (C) 2016 Red Hat, Inc. All rights reserved.
+ *
+ * This file is released under the LGPL.
+ */
+
+#ifndef DM_CORE_INTERNAL_H
+#define DM_CORE_INTERNAL_H
+
+#include <linux/kthread.h>
+#include <linux/ktime.h>
+#include <linux/blk-mq.h>
+
+#include <trace/events/block.h>
+
+#include "dm.h"
+
+#define DM_RESERVED_MAX_IOS		1024
+
+struct dm_kobject_holder {
+	struct kobject kobj;
+	struct completion completion;
+};
+
+/*
+ * DM core internal structure that used directly by dm.c and dm-rq.c
+ * DM targets must _not_ deference a mapped_device to directly access its members!
+ */
+struct mapped_device {
+	struct srcu_struct io_barrier;
+	struct mutex suspend_lock;
+
+	/*
+	 * The current mapping (struct dm_table *).
+	 * Use dm_get_live_table{_fast} or take suspend_lock for
+	 * dereference.
+	 */
+	void __rcu *map;
+
+	struct list_head table_devices;
+	struct mutex table_devices_lock;
+
+	unsigned long flags;
+
+	struct request_queue *queue;
+	int numa_node_id;
+
+	unsigned type;
+	/* Protect queue and type against concurrent access. */
+	struct mutex type_lock;
+
+	atomic_t holders;
+	atomic_t open_count;
+
+	struct dm_target *immutable_target;
+	struct target_type *immutable_target_type;
+
+	struct gendisk *disk;
+	char name[16];
+
+	void *interface_ptr;
+
+	/*
+	 * A list of ios that arrived while we were suspended.
+	 */
+	atomic_t pending[2];
+	wait_queue_head_t wait;
+	struct work_struct work;
+	spinlock_t deferred_lock;
+	struct bio_list deferred;
+
+	/*
+	 * Event handling.
+	 */
+	wait_queue_head_t eventq;
+	atomic_t event_nr;
+	atomic_t uevent_seq;
+	struct list_head uevent_list;
+	spinlock_t uevent_lock; /* Protect access to uevent_list */
+
+	/* the number of internal suspends */
+	unsigned internal_suspend_count;
+
+	/*
+	 * Processing queue (flush)
+	 */
+	struct workqueue_struct *wq;
+
+	/*
+	 * io objects are allocated from here.
+	 */
+	mempool_t *io_pool;
+	mempool_t *rq_pool;
+
+	struct bio_set *bs;
+
+	/*
+	 * freeze/thaw support require holding onto a super block
+	 */
+	struct super_block *frozen_sb;
+
+	/* forced geometry settings */
+	struct hd_geometry geometry;
+
+	struct block_device *bdev;
+
+	/* kobject and completion */
+	struct dm_kobject_holder kobj_holder;
+
+	/* zero-length flush that will be cloned and submitted to targets */
+	struct bio flush_bio;
+
+	struct dm_stats stats;
+
+	struct kthread_worker kworker;
+	struct task_struct *kworker_task;
+
+	/* for request-based merge heuristic in dm_request_fn() */
+	unsigned seq_rq_merge_deadline_usecs;
+	int last_rq_rw;
+	sector_t last_rq_pos;
+	ktime_t last_rq_start_time;
+
+	/* for blk-mq request-based DM support */
+	struct blk_mq_tag_set *tag_set;
+	bool use_blk_mq:1;
+	bool init_tio_pdu:1;
+};
+
+void dm_init_md_queue(struct mapped_device *md);
+void dm_init_normal_md_queue(struct mapped_device *md);
+int md_in_flight(struct mapped_device *md);
+void disable_write_same(struct mapped_device *md);
+
+static inline struct completion *dm_get_completion_from_kobject(struct kobject *kobj)
+{
+	return &container_of(kobj, struct dm_kobject_holder, kobj)->completion;
+}
+
+unsigned __dm_get_module_param(unsigned *module_param, unsigned def, unsigned max);
+
+static inline bool dm_message_test_buffer_overflow(char *result, unsigned maxlen)
+{
+	return !maxlen || strlen(result) + 1 >= maxlen;
+}
+
+#endif
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 96dd5d7e454a..8f2e3e2ffd26 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -683,7 +683,7 @@ static int crypt_iv_tcw_whitening(struct crypt_config *cc,
 				  u8 *data)
 {
 	struct iv_tcw_private *tcw = &cc->iv_gen_private.tcw;
-	u64 sector = cpu_to_le64((u64)dmreq->iv_sector);
+	__le64 sector = cpu_to_le64(dmreq->iv_sector);
 	u8 buf[TCW_WHITENING_SIZE];
 	SHASH_DESC_ON_STACK(desc, tcw->crc32_tfm);
 	int i, r;
@@ -722,7 +722,7 @@ static int crypt_iv_tcw_gen(struct crypt_config *cc, u8 *iv,
 			    struct dm_crypt_request *dmreq)
 {
 	struct iv_tcw_private *tcw = &cc->iv_gen_private.tcw;
-	u64 sector = cpu_to_le64((u64)dmreq->iv_sector);
+	__le64 sector = cpu_to_le64(dmreq->iv_sector);
 	u8 *src;
 	int r = 0;
 
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index 0e225fd4a8d1..daa03e41654a 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -5,7 +5,7 @@
  * This file is released under the GPL.
  */
 
-#include "dm.h"
+#include "dm-core.h"
 
 #include <linux/device-mapper.h>
 
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 2c7ca258c4e4..966eb4b61aed 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -5,7 +5,7 @@
  * This file is released under the GPL.
  */
 
-#include "dm.h"
+#include "dm-core.h"
 
 #include <linux/module.h>
 #include <linux/vmalloc.h>
@@ -1267,6 +1267,15 @@ static int populate_table(struct dm_table *table,
 	return dm_table_complete(table);
 }
 
+static bool is_valid_type(unsigned cur, unsigned new)
+{
+	if (cur == new ||
+	    (cur == DM_TYPE_BIO_BASED && new == DM_TYPE_DAX_BIO_BASED))
+		return true;
+
+	return false;
+}
+
 static int table_load(struct dm_ioctl *param, size_t param_size)
 {
 	int r;
@@ -1309,7 +1318,7 @@ static int table_load(struct dm_ioctl *param, size_t param_size)
 			DMWARN("unable to set up device queue for new table.");
 			goto err_unlock_md_type;
 		}
-	} else if (dm_get_md_type(md) != dm_table_get_type(t)) {
+	} else if (!is_valid_type(dm_get_md_type(md), dm_table_get_type(t))) {
 		DMWARN("can't change device type after initial table load.");
 		r = -EINVAL;
 		goto err_unlock_md_type;
@@ -1670,8 +1679,7 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
 	return r;
 }
 
-#define DM_PARAMS_KMALLOC	0x0001	/* Params alloced with kmalloc */
-#define DM_PARAMS_VMALLOC	0x0002	/* Params alloced with vmalloc */
+#define DM_PARAMS_MALLOC	0x0001	/* Params allocated with kvmalloc() */
 #define DM_WIPE_BUFFER		0x0010	/* Wipe input buffer before returning from ioctl */
 
 static void free_params(struct dm_ioctl *param, size_t param_size, int param_flags)
@@ -1679,10 +1687,8 @@ static void free_params(struct dm_ioctl *param, size_t param_size, int param_fla
 	if (param_flags & DM_WIPE_BUFFER)
 		memset(param, 0, param_size);
 
-	if (param_flags & DM_PARAMS_KMALLOC)
-		kfree(param);
-	if (param_flags & DM_PARAMS_VMALLOC)
-		vfree(param);
+	if (param_flags & DM_PARAMS_MALLOC)
+		kvfree(param);
 }
 
 static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kernel,
@@ -1714,19 +1720,14 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
 	 * Use kmalloc() rather than vmalloc() when we can.
 	 */
 	dmi = NULL;
-	if (param_kernel->data_size <= KMALLOC_MAX_SIZE) {
+	if (param_kernel->data_size <= KMALLOC_MAX_SIZE)
 		dmi = kmalloc(param_kernel->data_size, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
-		if (dmi)
-			*param_flags |= DM_PARAMS_KMALLOC;
-	}
 
 	if (!dmi) {
 		unsigned noio_flag;
 		noio_flag = memalloc_noio_save();
 		dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_HIGH | __GFP_HIGHMEM, PAGE_KERNEL);
 		memalloc_noio_restore(noio_flag);
-		if (dmi)
-			*param_flags |= DM_PARAMS_VMALLOC;
 	}
 
 	if (!dmi) {
@@ -1735,6 +1736,8 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
 		return -ENOMEM;
 	}
 
+	*param_flags |= DM_PARAMS_MALLOC;
+
 	if (copy_from_user(dmi, user, param_kernel->data_size))
 		goto bad;
 
diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index 9da1d54ac6cb..9e9d04cb7d51 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -26,7 +26,7 @@
 #include <linux/device-mapper.h>
 #include <linux/dm-kcopyd.h>
 
-#include "dm.h"
+#include "dm-core.h"
 
 #define SUB_JOB_SIZE	128
 #define SPLIT_COUNT	8
diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 05c35aacb3aa..6d35dd4e9efb 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -141,9 +141,27 @@ static int linear_iterate_devices(struct dm_target *ti,
 	return fn(ti, lc->dev, lc->start, ti->len, data);
 }
 
+static long linear_direct_access(struct dm_target *ti, sector_t sector,
+				 void __pmem **kaddr, pfn_t *pfn, long size)
+{
+	struct linear_c *lc = ti->private;
+	struct block_device *bdev = lc->dev->bdev;
+	struct blk_dax_ctl dax = {
+		.sector = linear_map_sector(ti, sector),
+		.size = size,
+	};
+	long ret;
+
+	ret = bdev_direct_access(bdev, &dax);
+	*kaddr = dax.addr;
+	*pfn = dax.pfn;
+
+	return ret;
+}
+
 static struct target_type linear_target = {
 	.name   = "linear",
-	.version = {1, 2, 1},
+	.version = {1, 3, 0},
 	.module = THIS_MODULE,
 	.ctr    = linear_ctr,
 	.dtr    = linear_dtr,
@@ -151,6 +169,7 @@ static struct target_type linear_target = {
 	.status = linear_status,
 	.prepare_ioctl = linear_prepare_ioctl,
 	.iterate_devices = linear_iterate_devices,
+	.direct_access = linear_direct_access,
 };
 
 int __init dm_linear_init(void)
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 52baf8a5b0f4..7eac080fcb18 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -7,7 +7,8 @@
 
 #include <linux/device-mapper.h>
 
-#include "dm.h"
+#include "dm-rq.h"
+#include "dm-bio-record.h"
 #include "dm-path-selector.h"
 #include "dm-uevent.h"
 
@@ -89,6 +90,8 @@ struct multipath {
 	atomic_t pg_init_in_progress;	/* Only one pg_init allowed at once */
 	atomic_t pg_init_count;		/* Number of times pg_init called */
 
+	unsigned queue_mode;
+
 	/*
 	 * We must use a mempool of dm_mpath_io structs so that we
 	 * can resubmit bios on error.
@@ -97,10 +100,13 @@ struct multipath {
 
 	struct mutex work_mutex;
 	struct work_struct trigger_event;
+
+	struct work_struct process_queued_bios;
+	struct bio_list queued_bios;
 };
 
 /*
- * Context information attached to each bio we process.
+ * Context information attached to each io we process.
  */
 struct dm_mpath_io {
 	struct pgpath *pgpath;
@@ -114,6 +120,7 @@ static struct kmem_cache *_mpio_cache;
 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 static void trigger_event(struct work_struct *work);
 static void activate_path(struct work_struct *work);
+static void process_queued_bios(struct work_struct *work);
 
 /*-----------------------------------------------
  * Multipath state flags.
@@ -185,7 +192,7 @@ static void free_priority_group(struct priority_group *pg,
 	kfree(pg);
 }
 
-static struct multipath *alloc_multipath(struct dm_target *ti, bool use_blk_mq)
+static struct multipath *alloc_multipath(struct dm_target *ti)
 {
 	struct multipath *m;
 
@@ -203,15 +210,7 @@ static struct multipath *alloc_multipath(struct dm_target *ti, bool use_blk_mq)
 		mutex_init(&m->work_mutex);
 
 		m->mpio_pool = NULL;
-		if (!use_blk_mq) {
-			unsigned min_ios = dm_get_reserved_rq_based_ios();
-
-			m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
-			if (!m->mpio_pool) {
-				kfree(m);
-				return NULL;
-			}
-		}
+		m->queue_mode = DM_TYPE_NONE;
 
 		m->ti = ti;
 		ti->private = m;
@@ -220,6 +219,39 @@ static struct multipath *alloc_multipath(struct dm_target *ti, bool use_blk_mq)
 	return m;
 }
 
+static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
+{
+	if (m->queue_mode == DM_TYPE_NONE) {
+		/*
+		 * Default to request-based.
+		 */
+		if (dm_use_blk_mq(dm_table_get_md(ti->table)))
+			m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
+		else
+			m->queue_mode = DM_TYPE_REQUEST_BASED;
+	}
+
+	if (m->queue_mode == DM_TYPE_REQUEST_BASED) {
+		unsigned min_ios = dm_get_reserved_rq_based_ios();
+
+		m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
+		if (!m->mpio_pool)
+			return -ENOMEM;
+	}
+	else if (m->queue_mode == DM_TYPE_BIO_BASED) {
+		INIT_WORK(&m->process_queued_bios, process_queued_bios);
+		/*
+		 * bio-based doesn't support any direct scsi_dh management;
+		 * it just discovers if a scsi_dh is attached.
+		 */
+		set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
+	}
+
+	dm_table_set_type(ti->table, m->queue_mode);
+
+	return 0;
+}
+
 static void free_multipath(struct multipath *m)
 {
 	struct priority_group *pg, *tmp;
@@ -272,6 +304,41 @@ static void clear_request_fn_mpio(struct multipath *m, union map_info *info)
 	}
 }
 
+static size_t multipath_per_bio_data_size(void)
+{
+	return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
+}
+
+static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
+{
+	return dm_per_bio_data(bio, multipath_per_bio_data_size());
+}
+
+static struct dm_bio_details *get_bio_details_from_bio(struct bio *bio)
+{
+	/* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
+	struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
+	void *bio_details = mpio + 1;
+
+	return bio_details;
+}
+
+static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p,
+					struct dm_bio_details **bio_details_p)
+{
+	struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
+	struct dm_bio_details *bio_details = get_bio_details_from_bio(bio);
+
+	memset(mpio, 0, sizeof(*mpio));
+	memset(bio_details, 0, sizeof(*bio_details));
+	dm_bio_record(bio_details, bio);
+
+	if (mpio_p)
+		*mpio_p = mpio;
+	if (bio_details_p)
+		*bio_details_p = bio_details;
+}
+
 /*-----------------------------------------------
  * Path selection
  *-----------------------------------------------*/
@@ -431,16 +498,26 @@ failed:
  * and multipath_resume() calls and we have no need to check
  * for the DMF_NOFLUSH_SUSPENDING flag.
  */
-static int must_push_back(struct multipath *m)
+static bool __must_push_back(struct multipath *m)
+{
+	return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) !=
+		 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) &&
+		dm_noflush_suspending(m->ti));
+}
+
+static bool must_push_back_rq(struct multipath *m)
 {
 	return (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) ||
-		((test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) !=
-		  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) &&
-		 dm_noflush_suspending(m->ti)));
+		__must_push_back(m));
+}
+
+static bool must_push_back_bio(struct multipath *m)
+{
+	return __must_push_back(m);
 }
 
 /*
- * Map cloned requests
+ * Map cloned requests (request-based multipath)
  */
 static int __multipath_map(struct dm_target *ti, struct request *clone,
 			   union map_info *map_context,
@@ -459,7 +536,7 @@ static int __multipath_map(struct dm_target *ti, struct request *clone,
 		pgpath = choose_pgpath(m, nr_bytes);
 
 	if (!pgpath) {
-		if (!must_push_back(m))
+		if (!must_push_back_rq(m))
 			r = -EIO;	/* Failed */
 		return r;
 	} else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
@@ -530,6 +607,108 @@ static void multipath_release_clone(struct request *clone)
 }
 
 /*
+ * Map cloned bios (bio-based multipath)
+ */
+static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_mpath_io *mpio)
+{
+	size_t nr_bytes = bio->bi_iter.bi_size;
+	struct pgpath *pgpath;
+	unsigned long flags;
+	bool queue_io;
+
+	/* Do we need to select a new pgpath? */
+	pgpath = lockless_dereference(m->current_pgpath);
+	queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
+	if (!pgpath || !queue_io)
+		pgpath = choose_pgpath(m, nr_bytes);
+
+	if ((pgpath && queue_io) ||
+	    (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
+		/* Queue for the daemon to resubmit */
+		spin_lock_irqsave(&m->lock, flags);
+		bio_list_add(&m->queued_bios, bio);
+		spin_unlock_irqrestore(&m->lock, flags);
+		/* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
+		if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
+			pg_init_all_paths(m);
+		else if (!queue_io)
+			queue_work(kmultipathd, &m->process_queued_bios);
+		return DM_MAPIO_SUBMITTED;
+	}
+
+	if (!pgpath) {
+		if (!must_push_back_bio(m))
+			return -EIO;
+		return DM_MAPIO_REQUEUE;
+	}
+
+	mpio->pgpath = pgpath;
+	mpio->nr_bytes = nr_bytes;
+
+	bio->bi_error = 0;
+	bio->bi_bdev = pgpath->path.dev->bdev;
+	bio->bi_rw |= REQ_FAILFAST_TRANSPORT;
+
+	if (pgpath->pg->ps.type->start_io)
+		pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
+					      &pgpath->path,
+					      nr_bytes);
+	return DM_MAPIO_REMAPPED;
+}
+
+static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
+{
+	struct multipath *m = ti->private;
+	struct dm_mpath_io *mpio = NULL;
+
+	multipath_init_per_bio_data(bio, &mpio, NULL);
+
+	return __multipath_map_bio(m, bio, mpio);
+}
+
+static void process_queued_bios_list(struct multipath *m)
+{
+	if (m->queue_mode == DM_TYPE_BIO_BASED)
+		queue_work(kmultipathd, &m->process_queued_bios);
+}
+
+static void process_queued_bios(struct work_struct *work)
+{
+	int r;
+	unsigned long flags;
+	struct bio *bio;
+	struct bio_list bios;
+	struct blk_plug plug;
+	struct multipath *m =
+		container_of(work, struct multipath, process_queued_bios);
+
+	bio_list_init(&bios);
+
+	spin_lock_irqsave(&m->lock, flags);
+
+	if (bio_list_empty(&m->queued_bios)) {
+		spin_unlock_irqrestore(&m->lock, flags);
+		return;
+	}
+
+	bio_list_merge(&bios, &m->queued_bios);
+	bio_list_init(&m->queued_bios);
+
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	blk_start_plug(&plug);
+	while ((bio = bio_list_pop(&bios))) {
+		r = __multipath_map_bio(m, bio, get_mpio_from_bio(bio));
+		if (r < 0 || r == DM_MAPIO_REQUEUE) {
+			bio->bi_error = r;
+			bio_endio(bio);
+		} else if (r == DM_MAPIO_REMAPPED)
+			generic_make_request(bio);
+	}
+	blk_finish_plug(&plug);
+}
+
+/*
  * If we run out of usable paths, should we queue I/O or error it?
  */
 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
@@ -557,8 +736,10 @@ static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 
 	spin_unlock_irqrestore(&m->lock, flags);
 
-	if (!queue_if_no_path)
+	if (!queue_if_no_path) {
 		dm_table_run_md_queue_async(m->ti->table);
+		process_queued_bios_list(m);
+	}
 
 	return 0;
 }
@@ -798,6 +979,12 @@ static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 	if (!hw_argc)
 		return 0;
 
+	if (m->queue_mode == DM_TYPE_BIO_BASED) {
+		dm_consume_args(as, hw_argc);
+		DMERR("bio-based multipath doesn't allow hardware handler args");
+		return 0;
+	}
+
 	m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 
 	if (hw_argc > 1) {
@@ -833,7 +1020,7 @@ static int parse_features(struct dm_arg_set *as, struct multipath *m)
 	const char *arg_name;
 
 	static struct dm_arg _args[] = {
-		{0, 6, "invalid number of feature args"},
+		{0, 8, "invalid number of feature args"},
 		{1, 50, "pg_init_retries must be between 1 and 50"},
 		{0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 	};
@@ -873,6 +1060,24 @@ static int parse_features(struct dm_arg_set *as, struct multipath *m)
 			continue;
 		}
 
+		if (!strcasecmp(arg_name, "queue_mode") &&
+		    (argc >= 1)) {
+			const char *queue_mode_name = dm_shift_arg(as);
+
+			if (!strcasecmp(queue_mode_name, "bio"))
+				m->queue_mode = DM_TYPE_BIO_BASED;
+			else if (!strcasecmp(queue_mode_name, "rq"))
+				m->queue_mode = DM_TYPE_REQUEST_BASED;
+			else if (!strcasecmp(queue_mode_name, "mq"))
+				m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
+			else {
+				ti->error = "Unknown 'queue_mode' requested";
+				r = -EINVAL;
+			}
+			argc--;
+			continue;
+		}
+
 		ti->error = "Unrecognised multipath feature request";
 		r = -EINVAL;
 	} while (argc && !r);
@@ -880,8 +1085,7 @@ static int parse_features(struct dm_arg_set *as, struct multipath *m)
 	return r;
 }
 
-static int multipath_ctr(struct dm_target *ti, unsigned int argc,
-			 char **argv)
+static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
 {
 	/* target arguments */
 	static struct dm_arg _args[] = {
@@ -894,12 +1098,11 @@ static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 	struct dm_arg_set as;
 	unsigned pg_count = 0;
 	unsigned next_pg_num;
-	bool use_blk_mq = dm_use_blk_mq(dm_table_get_md(ti->table));
 
 	as.argc = argc;
 	as.argv = argv;
 
-	m = alloc_multipath(ti, use_blk_mq);
+	m = alloc_multipath(ti);
 	if (!m) {
 		ti->error = "can't allocate multipath";
 		return -EINVAL;
@@ -909,6 +1112,10 @@ static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 	if (r)
 		goto bad;
 
+	r = alloc_multipath_stage2(ti, m);
+	if (r)
+		goto bad;
+
 	r = parse_hw_handler(&as, m);
 	if (r)
 		goto bad;
@@ -958,7 +1165,9 @@ static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 	ti->num_flush_bios = 1;
 	ti->num_discard_bios = 1;
 	ti->num_write_same_bios = 1;
-	if (use_blk_mq)
+	if (m->queue_mode == DM_TYPE_BIO_BASED)
+		ti->per_io_data_size = multipath_per_bio_data_size();
+	else if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
 		ti->per_io_data_size = sizeof(struct dm_mpath_io);
 
 	return 0;
@@ -1083,8 +1292,10 @@ static int reinstate_path(struct pgpath *pgpath)
 
 out:
 	spin_unlock_irqrestore(&m->lock, flags);
-	if (run_queue)
+	if (run_queue) {
 		dm_table_run_md_queue_async(m->ti->table);
+		process_queued_bios_list(m);
+	}
 
 	return r;
 }
@@ -1281,6 +1492,8 @@ static void pg_init_done(void *data, int errors)
 	}
 	clear_bit(MPATHF_QUEUE_IO, &m->flags);
 
+	process_queued_bios_list(m);
+
 	/*
 	 * Wake up any thread waiting to suspend.
 	 */
@@ -1328,7 +1541,7 @@ static int do_end_io(struct multipath *m, struct request *clone,
 	 * 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
+	 * (See drivers/md/dm-rq.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
@@ -1347,7 +1560,7 @@ static int do_end_io(struct multipath *m, struct request *clone,
 
 	if (!atomic_read(&m->nr_valid_paths)) {
 		if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
-			if (!must_push_back(m))
+			if (!must_push_back_rq(m))
 				r = -EIO;
 		} else {
 			if (error == -EBADE)
@@ -1381,6 +1594,64 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone,
 	return r;
 }
 
+static int do_end_io_bio(struct multipath *m, struct bio *clone,
+			 int error, struct dm_mpath_io *mpio)
+{
+	unsigned long flags;
+
+	if (!error)
+		return 0;	/* I/O complete */
+
+	if (noretry_error(error))
+		return error;
+
+	if (mpio->pgpath)
+		fail_path(mpio->pgpath);
+
+	if (!atomic_read(&m->nr_valid_paths)) {
+		if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
+			if (!must_push_back_bio(m))
+				return -EIO;
+			return DM_ENDIO_REQUEUE;
+		} else {
+			if (error == -EBADE)
+				return error;
+		}
+	}
+
+	/* Queue for the daemon to resubmit */
+	dm_bio_restore(get_bio_details_from_bio(clone), clone);
+
+	spin_lock_irqsave(&m->lock, flags);
+	bio_list_add(&m->queued_bios, clone);
+	spin_unlock_irqrestore(&m->lock, flags);
+	if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
+		queue_work(kmultipathd, &m->process_queued_bios);
+
+	return DM_ENDIO_INCOMPLETE;
+}
+
+static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone, int error)
+{
+	struct multipath *m = ti->private;
+	struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
+	struct pgpath *pgpath;
+	struct path_selector *ps;
+	int r;
+
+	BUG_ON(!mpio);
+
+	r = do_end_io_bio(m, clone, error, mpio);
+	pgpath = mpio->pgpath;
+	if (pgpath) {
+		ps = &pgpath->pg->ps;
+		if (ps->type->end_io)
+			ps->type->end