dm unstriped: add new target

index 83b9362be09c..7f8099f53ad6 100644
@@ -269,6 +269,17 @@ config DM_BIO_PRISON
 
 source "drivers/md/persistent-data/Kconfig"
 
+config DM_UNSTRIPED
+       tristate "Transpose IO to individual drives on a raid device"
+       depends on BLK_DEV_DM
+       ---help---
+         Enable this feature if you with to unstripe I/O on a RAID 0
+	 device to the respective drive. If your hardware has physical
+	 RAID 0 this module can unstripe the I/O to respective controllers
+	 on the stripes.
+
+	 If unsure say N.
+
 config DM_CRYPT
 	tristate "Crypt target support"
 	depends on BLK_DEV_DM

index f701bb211783..63255f3ebd97 100644
@@ -43,6 +43,7 @@ obj-$(CONFIG_BCACHE)		+= bcache/
 obj-$(CONFIG_BLK_DEV_MD)	+= md-mod.o
 obj-$(CONFIG_BLK_DEV_DM)	+= dm-mod.o
 obj-$(CONFIG_BLK_DEV_DM_BUILTIN) += dm-builtin.o
+obj-$(CONFIG_DM_UNSTRIPED)	+= dm-unstripe.o
 obj-$(CONFIG_DM_BUFIO)		+= dm-bufio.o
 obj-$(CONFIG_DM_BIO_PRISON)	+= dm-bio-prison.o
 obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o

new file mode 100644
index 000000000000..01d7194b9075
@@ -0,0 +1,130 @@
+Device-Mapper Unstripe
+=====================
+
+The device-mapper unstripe (dm-unstripe) target provides a transparent
+mechanism to unstripe a device-mapper "striped" target to access the
+underlying disks without having to touch the true backing block-device.
+It can also be used to unstripe a hardware RAID-0 to access backing disks
+as well.
+
+
+Parameters:
+<drive (ex: /dev/nvme0n1)> <drive #> <# of drives> <chunk sectors>
+
+
+<drive>
+	The block device you wish to unstripe.
+
+<drive #>
+        The physical drive you wish to expose via this "virtual" device
+	mapper target. This must be 0 indexed.
+
+<# of drives>
+        The number of drives in the RAID 0.
+
+<chunk sectors>
+	The amount of 512B sectors in the chunk striping, or zero, if you
+	wish you use max_hw_sector_size.
+
+
+Why use this module?
+=====================
+
+    An example of undoing an existing dm-stripe:
+
+    This small bash script will setup 4 loop devices and use the existing
+    dm-stripe target to combine the 4 devices into one. It then will use
+    the unstripe target on the new combined stripe device to access the
+    individual backing loop devices. We write data to the newly exposed
+    unstriped devices and verify the data written matches the correct
+    underlying device on the striped array.
+
+    #!/bin/bash
+
+    MEMBER_SIZE=$((128 * 1024 * 1024))
+    NUM=4
+    SEQ_END=$((${NUM}-1))
+    CHUNK=256
+    BS=4096
+
+    RAID_SIZE=$((${MEMBER_SIZE}*${NUM}/512))
+    DM_PARMS="0 ${RAID_SIZE} striped ${NUM} ${CHUNK}"
+    COUNT=$((${MEMBER_SIZE} / ${BS}))
+
+    for i in $(seq 0 ${SEQ_END}); do
+      dd if=/dev/zero of=member-${i} bs=${MEMBER_SIZE} count=1 oflag=direct
+      losetup /dev/loop${i} member-${i}
+      DM_PARMS+=" /dev/loop${i} 0"
+    done
+
+    echo $DM_PARMS | dmsetup create raid0
+    for i in $(seq 0 ${SEQ_END}); do
+      echo "0 1 unstripe /dev/mapper/raid0 ${i} ${NUM} ${CHUNK}" | dmsetup create set-${i}
+    done;
+
+    for i in $(seq 0 ${SEQ_END}); do
+      dd if=/dev/urandom of=/dev/mapper/set-${i} bs=${BS} count=${COUNT} oflag=direct
+      diff /dev/mapper/set-${i} member-${i}
+    done;
+
+    for i in $(seq 0 ${SEQ_END}); do
+      dmsetup remove set-${i}
+    done
+
+    dmsetup remove raid0
+
+    for i in $(seq 0 ${SEQ_END}); do
+      losetup -d /dev/loop${i}
+      rm -f member-${i}
+    done
+
+==============
+
+
+    Another example:
+
+    Intel NVMe drives contain two cores on the physical device.
+    Each core of the drive has segregated access to its LBA range.
+    The current LBA model has a RAID 0 128k chunk on each core, resulting
+    in a 256k stripe across the two cores:
+
+       Core 0:                Core 1:
+      __________            __________
+      | LBA 512|            | LBA 768|
+      | LBA 0  |            | LBA 256|
+      ⎻⎻⎻⎻⎻⎻⎻⎻⎻⎻            ⎻⎻⎻⎻⎻⎻⎻⎻⎻⎻
+
+    The purpose of this unstriping is to provide better QoS in noisy
+    neighbor environments. When two partitions are created on the
+    aggregate drive without this unstriping, reads on one partition
+    can affect writes on another partition. This is because the partitions
+    are striped across the two cores. When we unstripe this hardware RAID 0
+    and make partitions on each new exposed device the two partitions are now
+    physically separated.
+
+    With the module we were able to segregate a fio script that has read and
+    write jobs that are independent of each other. Compared to when we run
+    the test on a combined drive with partitions, we were able to get a 92%
+    reduction in five-9ths read latency using this device mapper target.
+
+
+====================
+Example scripts:
+
+
+dmsetup create nvmset1 --table '0 1 unstripe /dev/nvme0n1 1 2 0'
+dmsetup create nvmset0 --table '0 1 unstripe /dev/nvme0n1 0 2 0'
+
+There will now be two mappers:
+/dev/mapper/nvmset1
+/dev/mapper/nvmset0
+
+that will expose core 0 and core 1.
+
+
+# In a dm-stripe with 4 drives of chunk size 128K:
+dmsetup create raid_disk0 --table '0 1 unstripe /dev/mapper/striped 0 4 256'
+dmsetup create raid_disk1 --table '0 1 unstripe /dev/mapper/striped 1 4 256'
+dmsetup create raid_disk2 --table '0 1 unstripe /dev/mapper/striped 2 4 256'
+dmsetup create raid_disk3 --table '0 1 unstripe /dev/mapper/striped 3 4 256'
+

new file mode 100644
index 000000000000..0b2a306c54ee
@@ -0,0 +1,124 @@
+Introduction
+============
+
+The device-mapper "unstriped" target provides a transparent mechanism to
+unstripe a device-mapper "striped" target to access the underlying disks
+without having to touch the true backing block-device.  It can also be
+used to unstripe a hardware RAID-0 to access backing disks.
+
+Parameters:
+<number of stripes> <chunk size> <stripe #> <dev_path> <offset>
+
+<number of stripes>
+        The number of stripes in the RAID 0.
+
+<chunk size>
+	The amount of 512B sectors in the chunk striping.
+
+<dev_path>
+	The block device you wish to unstripe.
+
+<stripe #>
+        The stripe number within the device that corresponds to physical
+        drive you wish to unstripe.  This must be 0 indexed.
+
+
+Why use this module?
+====================
+
+An example of undoing an existing dm-stripe
+-------------------------------------------
+
+This small bash script will setup 4 loop devices and use the existing
+striped target to combine the 4 devices into one.  It then will use
+the unstriped target ontop of the striped device to access the
+individual backing loop devices.  We write data to the newly exposed
+unstriped devices and verify the data written matches the correct
+underlying device on the striped array.
+
+#!/bin/bash
+
+MEMBER_SIZE=$((128 * 1024 * 1024))
+NUM=4
+SEQ_END=$((${NUM}-1))
+CHUNK=256
+BS=4096
+
+RAID_SIZE=$((${MEMBER_SIZE}*${NUM}/512))
+DM_PARMS="0 ${RAID_SIZE} striped ${NUM} ${CHUNK}"
+COUNT=$((${MEMBER_SIZE} / ${BS}))
+
+for i in $(seq 0 ${SEQ_END}); do
+  dd if=/dev/zero of=member-${i} bs=${MEMBER_SIZE} count=1 oflag=direct
+  losetup /dev/loop${i} member-${i}
+  DM_PARMS+=" /dev/loop${i} 0"
+done
+
+echo $DM_PARMS | dmsetup create raid0
+for i in $(seq 0 ${SEQ_END}); do
+  echo "0 1 unstriped ${NUM} ${CHUNK} ${i} /dev/mapper/raid0 0" | dmsetup create set-${i}
+done;
+
+for i in $(seq 0 ${SEQ_END}); do
+  dd if=/dev/urandom of=/dev/mapper/set-${i} bs=${BS} count=${COUNT} oflag=direct
+  diff /dev/mapper/set-${i} member-${i}
+done;
+
+for i in $(seq 0 ${SEQ_END}); do
+  dmsetup remove set-${i}
+done
+
+dmsetup remove raid0
+
+for i in $(seq 0 ${SEQ_END}); do
+  losetup -d /dev/loop${i}
+  rm -f member-${i}
+done
+
+Another example
+---------------
+
+Intel NVMe drives contain two cores on the physical device.
+Each core of the drive has segregated access to its LBA range.
+The current LBA model has a RAID 0 128k chunk on each core, resulting
+in a 256k stripe across the two cores:
+
+   Core 0:       Core 1:
+  __________    __________
+  | LBA 512|    | LBA 768|
+  | LBA 0  |    | LBA 256|
+  ----------    ----------
+
+The purpose of this unstriping is to provide better QoS in noisy
+neighbor environments. When two partitions are created on the
+aggregate drive without this unstriping, reads on one partition
+can affect writes on another partition.  This is because the partitions
+are striped across the two cores.  When we unstripe this hardware RAID 0
+and make partitions on each new exposed device the two partitions are now
+physically separated.
+
+With the dm-unstriped target we're able to segregate an fio script that
+has read and write jobs that are independent of each other.  Compared to
+when we run the test on a combined drive with partitions, we were able
+to get a 92% reduction in read latency using this device mapper target.
+
+
+Example dmsetup usage
+=====================
+
+unstriped ontop of Intel NVMe device that has 2 cores
+-----------------------------------------------------
+dmsetup create nvmset0 --table '0 512 unstriped 2 256 0 /dev/nvme0n1 0'
+dmsetup create nvmset1 --table '0 512 unstriped 2 256 1 /dev/nvme0n1 0'
+
+There will now be two devices that expose Intel NVMe core 0 and 1
+respectively:
+/dev/mapper/nvmset0
+/dev/mapper/nvmset1
+
+unstriped ontop of striped with 4 drives using 128K chunk size
+--------------------------------------------------------------
+dmsetup create raid_disk0 --table '0 512 unstriped 4 256 0 /dev/mapper/striped 0'
+dmsetup create raid_disk1 --table '0 512 unstriped 4 256 1 /dev/mapper/striped 0'
+dmsetup create raid_disk2 --table '0 512 unstriped 4 256 2 /dev/mapper/striped 0'
+dmsetup create raid_disk3 --table '0 512 unstriped 4 256 3 /dev/mapper/striped 0'

index 83b9362be09c..7843cf86f74a 100644
@@ -269,6 +269,13 @@ config DM_BIO_PRISON
 
 source "drivers/md/persistent-data/Kconfig"
 
+config DM_UNSTRIPED
+       tristate "Unstriped target"
+       depends on BLK_DEV_DM
+       ---help---
+	  Issue I/O to individual drives of a striped RAID device.
+	  Provides direct access to 1/N of an N-way RAID 0 device.
+
 config DM_CRYPT
 	tristate "Crypt target support"
 	depends on BLK_DEV_DM

index f701bb211783..63255f3ebd97 100644
@@ -43,6 +43,7 @@ obj-$(CONFIG_BCACHE)		+= bcache/
 obj-$(CONFIG_BLK_DEV_MD)	+= md-mod.o
 obj-$(CONFIG_BLK_DEV_DM)	+= dm-mod.o
 obj-$(CONFIG_BLK_DEV_DM_BUILTIN) += dm-builtin.o
+obj-$(CONFIG_DM_UNSTRIPED)	+= dm-unstripe.o
 obj-$(CONFIG_DM_BUFIO)		+= dm-bufio.o
 obj-$(CONFIG_DM_BIO_PRISON)	+= dm-bio-prison.o
 obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o