drivers/md/Kconfig - arm/linux - Git at Google


            
            #

            
            # Block device driver configuration

            
            #


            menuconfig MD

            
            	bool "Multiple devices driver support (RAID and LVM)"

            
            	depends on BLOCK

            
            	select SRCU

            
            	help

            
            	  Support multiple physical spindles through a single logical device.

            
            	  Required for RAID and logical volume management.


            if MD


            config BLK_DEV_MD

            
            	tristate "RAID support"

            
            	---help---

            
            	  This driver lets you combine several hard disk partitions into one

            
            	  logical block device. This can be used to simply append one

            
            	  partition to another one or to combine several redundant hard disks

            
            	  into a RAID1/4/5 device so as to provide protection against hard

            
            	  disk failures. This is called "Software RAID" since the combining of

            
            	  the partitions is done by the kernel. "Hardware RAID" means that the

            
            	  combining is done by a dedicated controller; if you have such a

            
            	  controller, you do not need to say Y here.


            	  More information about Software RAID on Linux is contained in the

            
            	  Software RAID mini-HOWTO, available from

            
            	  <http://www.tldp.org/docs.html#howto>. There you will also learn

            
            	  where to get the supporting user space utilities raidtools.


            	  If unsure, say N.


            config MD_AUTODETECT

            
            	bool "Autodetect RAID arrays during kernel boot"

            
            	depends on BLK_DEV_MD=y

            
            	default y

            
            	---help---

            
            	  If you say Y here, then the kernel will try to autodetect raid

            
            	  arrays as part of its boot process.


            	  If you don't use raid and say Y, this autodetection can cause

            
            	  a several-second delay in the boot time due to various

            
            	  synchronisation steps that are part of this step.


            	  If unsure, say Y.


            config MD_LINEAR

            
            	tristate "Linear (append) mode"

            
            	depends on BLK_DEV_MD

            
            	---help---

            
            	  If you say Y here, then your multiple devices driver will be able to

            
            	  use the so-called linear mode, i.e. it will combine the hard disk

            
            	  partitions by simply appending one to the other.


            	  To compile this as a module, choose M here: the module

            
            	  will be called linear.


            	  If unsure, say Y.


            config MD_RAID0

            
            	tristate "RAID-0 (striping) mode"

            
            	depends on BLK_DEV_MD

            
            	---help---

            
            	  If you say Y here, then your multiple devices driver will be able to

            
            	  use the so-called raid0 mode, i.e. it will combine the hard disk

            
            	  partitions into one logical device in such a fashion as to fill them

            
            	  up evenly, one chunk here and one chunk there. This will increase

            
            	  the throughput rate if the partitions reside on distinct disks.


            	  Information about Software RAID on Linux is contained in the

            
            	  Software-RAID mini-HOWTO, available from

            
            	  <http://www.tldp.org/docs.html#howto>. There you will also

            
            	  learn where to get the supporting user space utilities raidtools.


            	  To compile this as a module, choose M here: the module

            
            	  will be called raid0.


            	  If unsure, say Y.


            config MD_RAID1

            
            	tristate "RAID-1 (mirroring) mode"

            
            	depends on BLK_DEV_MD

            
            	---help---

            
            	  A RAID-1 set consists of several disk drives which are exact copies

            
            	  of each other.  In the event of a mirror failure, the RAID driver

            
            	  will continue to use the operational mirrors in the set, providing

            
            	  an error free MD (multiple device) to the higher levels of the

            
            	  kernel.  In a set with N drives, the available space is the capacity

            
            	  of a single drive, and the set protects against a failure of (N - 1)

            
            	  drives.


            	  Information about Software RAID on Linux is contained in the

            
            	  Software-RAID mini-HOWTO, available from

            
            	  <http://www.tldp.org/docs.html#howto>.  There you will also

            
            	  learn where to get the supporting user space utilities raidtools.


            	  If you want to use such a RAID-1 set, say Y.  To compile this code

            
            	  as a module, choose M here: the module will be called raid1.


            	  If unsure, say Y.


            config MD_RAID10

            
            	tristate "RAID-10 (mirrored striping) mode"

            
            	depends on BLK_DEV_MD

            
            	---help---

            
            	  RAID-10 provides a combination of striping (RAID-0) and

            
            	  mirroring (RAID-1) with easier configuration and more flexible

            
            	  layout.

            
            	  Unlike RAID-0, but like RAID-1, RAID-10 requires all devices to

            
            	  be the same size (or at least, only as much as the smallest device

            
            	  will be used).

            
            	  RAID-10 provides a variety of layouts that provide different levels

            
            	  of redundancy and performance.


            	  RAID-10 requires mdadm-1.7.0 or later, available at:


            	  ftp://ftp.kernel.org/pub/linux/utils/raid/mdadm/


            	  If unsure, say Y.


            config MD_RAID456

            
            	tristate "RAID-4/RAID-5/RAID-6 mode"

            
            	depends on BLK_DEV_MD

            
            	select RAID6_PQ

            
            	select LIBCRC32C

            
            	select ASYNC_MEMCPY

            
            	select ASYNC_XOR

            
            	select ASYNC_PQ

            
            	select ASYNC_RAID6_RECOV

            
            	---help---

            
            	  A RAID-5 set of N drives with a capacity of C MB per drive provides

            
            	  the capacity of C * (N - 1) MB, and protects against a failure

            
            	  of a single drive. For a given sector (row) number, (N - 1) drives

            
            	  contain data sectors, and one drive contains the parity protection.

            
            	  For a RAID-4 set, the parity blocks are present on a single drive,

            
            	  while a RAID-5 set distributes the parity across the drives in one

            
            	  of the available parity distribution methods.


            	  A RAID-6 set of N drives with a capacity of C MB per drive

            
            	  provides the capacity of C * (N - 2) MB, and protects

            
            	  against a failure of any two drives. For a given sector

            
            	  (row) number, (N - 2) drives contain data sectors, and two

            
            	  drives contains two independent redundancy syndromes.  Like

            
            	  RAID-5, RAID-6 distributes the syndromes across the drives

            
            	  in one of the available parity distribution methods.


            	  Information about Software RAID on Linux is contained in the

            
            	  Software-RAID mini-HOWTO, available from

            
            	  <http://www.tldp.org/docs.html#howto>. There you will also

            
            	  learn where to get the supporting user space utilities raidtools.


            	  If you want to use such a RAID-4/RAID-5/RAID-6 set, say Y.  To

            
            	  compile this code as a module, choose M here: the module

            
            	  will be called raid456.


            	  If unsure, say Y.


            config MD_MULTIPATH

            
            	tristate "Multipath I/O support"

            
            	depends on BLK_DEV_MD

            
            	help

            
            	  MD_MULTIPATH provides a simple multi-path personality for use

            
            	  the MD framework.  It is not under active development.  New

            
            	  projects should consider using DM_MULTIPATH which has more

            
            	  features and more testing.


            	  If unsure, say N.


            config MD_FAULTY

            
            	tristate "Faulty test module for MD"

            
            	depends on BLK_DEV_MD

            
            	help

            
            	  The "faulty" module allows for a block device that occasionally returns

            
            	  read or write errors.  It is useful for testing.


            	  In unsure, say N.


            config MD_CLUSTER

            
            	tristate "Cluster Support for MD (EXPERIMENTAL)"

            
            	depends on BLK_DEV_MD

            
            	depends on DLM

            
            	default n

            
            	---help---

            
            	Clustering support for MD devices. This enables locking and

            
            	synchronization across multiple systems on the cluster, so all

            
            	nodes in the cluster can access the MD devices simultaneously.


            	This brings the redundancy (and uptime) of RAID levels across the

            
            	nodes of the cluster.


            	If unsure, say N.


            source "drivers/md/bcache/Kconfig"


            config BLK_DEV_DM_BUILTIN

            
            	bool


            config BLK_DEV_DM

            
            	tristate "Device mapper support"

            
            	select BLK_DEV_DM_BUILTIN

            
            	---help---

            
            	  Device-mapper is a low level volume manager.  It works by allowing

            
            	  people to specify mappings for ranges of logical sectors.  Various

            
            	  mapping types are available, in addition people may write their own

            
            	  modules containing custom mappings if they wish.


            	  Higher level volume managers such as LVM2 use this driver.


            	  To compile this as a module, choose M here: the module will be

            
            	  called dm-mod.


            	  If unsure, say N.


            config DM_MQ_DEFAULT

            
            	bool "request-based DM: use blk-mq I/O path by default"

            
            	depends on BLK_DEV_DM

            
            	---help---

            
            	  This option enables the blk-mq based I/O path for request-based

            
            	  DM devices by default.  With the option the dm_mod.use_blk_mq

            
            	  module/boot option defaults to Y, without it to N, but it can

            
            	  still be overriden either way.


            	  If unsure say N.


            config DM_DEBUG

            
            	bool "Device mapper debugging support"

            
            	depends on BLK_DEV_DM

            
            	---help---

            
            	  Enable this for messages that may help debug device-mapper problems.


            	  If unsure, say N.


            config DM_BUFIO

            
                   tristate

            
                   depends on BLK_DEV_DM

            
                   ---help---

            
            	 This interface allows you to do buffered I/O on a device and acts

            
            	 as a cache, holding recently-read blocks in memory and performing

            
            	 delayed writes.


            config DM_DEBUG_BLOCK_STACK_TRACING

            
                   bool "Keep stack trace of persistent data block lock holders"

            
                   depends on STACKTRACE_SUPPORT && DM_BUFIO

            
                   select STACKTRACE

            
                   ---help---

            
            	 Enable this for messages that may help debug problems with the

            
            	 block manager locking used by thin provisioning and caching.


            	 If unsure, say N.


            config DM_BIO_PRISON

            
                   tristate

            
                   depends on BLK_DEV_DM

            
                   ---help---

            
            	 Some bio locking schemes used by other device-mapper targets

            
            	 including thin provisioning.


            source "drivers/md/persistent-data/Kconfig"


            config DM_CRYPT

            
            	tristate "Crypt target support"

            
            	depends on BLK_DEV_DM

            
            	select CRYPTO

            
            	select CRYPTO_CBC

            
            	---help---

            
            	  This device-mapper target allows you to create a device that

            
            	  transparently encrypts the data on it. You'll need to activate

            
            	  the ciphers you're going to use in the cryptoapi configuration.


            	  For further information on dm-crypt and userspace tools see:

            
            	  <https://gitlab.com/cryptsetup/cryptsetup/wikis/DMCrypt>


            	  To compile this code as a module, choose M here: the module will

            
            	  be called dm-crypt.


            	  If unsure, say N.


            config DM_SNAPSHOT

            
                   tristate "Snapshot target"

            
                   depends on BLK_DEV_DM

            
                   select DM_BUFIO

            
                   ---help---

            
                     Allow volume managers to take writable snapshots of a device.


            config DM_THIN_PROVISIONING

            
                   tristate "Thin provisioning target"

            
                   depends on BLK_DEV_DM

            
                   select DM_PERSISTENT_DATA

            
                   select DM_BIO_PRISON

            
                   ---help---

            
                     Provides thin provisioning and snapshots that share a data store.


            config DM_CACHE

            
                   tristate "Cache target (EXPERIMENTAL)"

            
                   depends on BLK_DEV_DM

            
                   default n

            
                   select DM_PERSISTENT_DATA

            
                   select DM_BIO_PRISON

            
                   ---help---

            
                     dm-cache attempts to improve performance of a block device by

            
                     moving frequently used data to a smaller, higher performance

            
                     device.  Different 'policy' plugins can be used to change the

            
                     algorithms used to select which blocks are promoted, demoted,

            
                     cleaned etc.  It supports writeback and writethrough modes.


            config DM_CACHE_SMQ

            
                   tristate "Stochastic MQ Cache Policy (EXPERIMENTAL)"

            
                   depends on DM_CACHE

            
                   default y

            
                   ---help---

            
                     A cache policy that uses a multiqueue ordered by recent hits

            
                     to select which blocks should be promoted and demoted.

            
                     This is meant to be a general purpose policy.  It prioritises

            
                     reads over writes.  This SMQ policy (vs MQ) offers the promise

            
                     of less memory utilization, improved performance and increased

            
                     adaptability in the face of changing workloads.


            config DM_CACHE_CLEANER

            
                   tristate "Cleaner Cache Policy (EXPERIMENTAL)"

            
                   depends on DM_CACHE

            
                   default y

            
                   ---help---

            
                     A simple cache policy that writes back all data to the

            
                     origin.  Used when decommissioning a dm-cache.


            config DM_ERA

            
                   tristate "Era target (EXPERIMENTAL)"

            
                   depends on BLK_DEV_DM

            
                   default n

            
                   select DM_PERSISTENT_DATA

            
                   select DM_BIO_PRISON

            
                   ---help---

            
                     dm-era tracks which parts of a block device are written to

            
                     over time.  Useful for maintaining cache coherency when using

            
                     vendor snapshots.


            config DM_MIRROR

            
                   tristate "Mirror target"

            
                   depends on BLK_DEV_DM

            
                   ---help---

            
                     Allow volume managers to mirror logical volumes, also

            
                     needed for live data migration tools such as 'pvmove'.


            config DM_LOG_USERSPACE

            
            	tristate "Mirror userspace logging"

            
            	depends on DM_MIRROR && NET

            
            	select CONNECTOR

            
            	---help---

            
            	  The userspace logging module provides a mechanism for

            
            	  relaying the dm-dirty-log API to userspace.  Log designs

            
            	  which are more suited to userspace implementation (e.g.

            
            	  shared storage logs) or experimental logs can be implemented

            
            	  by leveraging this framework.


            config DM_RAID

            
                   tristate "RAID 1/4/5/6/10 target"

            
                   depends on BLK_DEV_DM

            
                   select MD_RAID1

            
                   select MD_RAID10

            
                   select MD_RAID456

            
                   select BLK_DEV_MD

            
                   ---help---

            
            	 A dm target that supports RAID1, RAID10, RAID4, RAID5 and RAID6 mappings


            	 A RAID-5 set of N drives with a capacity of C MB per drive provides

            
            	 the capacity of C * (N - 1) MB, and protects against a failure

            
            	 of a single drive. For a given sector (row) number, (N - 1) drives

            
            	 contain data sectors, and one drive contains the parity protection.

            
            	 For a RAID-4 set, the parity blocks are present on a single drive,

            
            	 while a RAID-5 set distributes the parity across the drives in one

            
            	 of the available parity distribution methods.


            	 A RAID-6 set of N drives with a capacity of C MB per drive

            
            	 provides the capacity of C * (N - 2) MB, and protects

            
            	 against a failure of any two drives. For a given sector

            
            	 (row) number, (N - 2) drives contain data sectors, and two

            
            	 drives contains two independent redundancy syndromes.  Like

            
            	 RAID-5, RAID-6 distributes the syndromes across the drives

            
            	 in one of the available parity distribution methods.


            config DM_ZERO

            
            	tristate "Zero target"

            
            	depends on BLK_DEV_DM

            
            	---help---

            
            	  A target that discards writes, and returns all zeroes for

            
            	  reads.  Useful in some recovery situations.


            config DM_MULTIPATH

            
            	tristate "Multipath target"

            
            	depends on BLK_DEV_DM

            
            	# nasty syntax but means make DM_MULTIPATH independent

            
            	# of SCSI_DH if the latter isn't defined but if

            
            	# it is, DM_MULTIPATH must depend on it.  We get a build

            
            	# error if SCSI_DH=m and DM_MULTIPATH=y

            
            	depends on !SCSI_DH || SCSI

            
            	---help---

            
            	  Allow volume managers to support multipath hardware.


            config DM_MULTIPATH_QL

            
            	tristate "I/O Path Selector based on the number of in-flight I/Os"

            
            	depends on DM_MULTIPATH

            
            	---help---

            
            	  This path selector is a dynamic load balancer which selects

            
            	  the path with the least number of in-flight I/Os.


            	  If unsure, say N.


            config DM_MULTIPATH_ST

            
            	tristate "I/O Path Selector based on the service time"

            
            	depends on DM_MULTIPATH

            
            	---help---

            
            	  This path selector is a dynamic load balancer which selects

            
            	  the path expected to complete the incoming I/O in the shortest

            
            	  time.


            	  If unsure, say N.


            config DM_DELAY

            
            	tristate "I/O delaying target"

            
            	depends on BLK_DEV_DM

            
            	---help---

            
            	A target that delays reads and/or writes and can send

            
            	them to different devices.  Useful for testing.


            	If unsure, say N.


            config DM_UEVENT

            
            	bool "DM uevents"

            
            	depends on BLK_DEV_DM

            
            	---help---

            
            	Generate udev events for DM events.


            config DM_FLAKEY

            
                   tristate "Flakey target"

            
                   depends on BLK_DEV_DM

            
                   ---help---

            
                     A target that intermittently fails I/O for debugging purposes.


            config DM_VERITY

            
            	tristate "Verity target support"

            
            	depends on BLK_DEV_DM

            
            	select CRYPTO

            
            	select CRYPTO_HASH

            
            	select DM_BUFIO

            
            	---help---

            
            	  This device-mapper target creates a read-only device that

            
            	  transparently validates the data on one underlying device against

            
            	  a pre-generated tree of cryptographic checksums stored on a second

            
            	  device.


            	  You'll need to activate the digests you're going to use in the

            
            	  cryptoapi configuration.


            	  To compile this code as a module, choose M here: the module will

            
            	  be called dm-verity.


            	  If unsure, say N.


            config DM_VERITY_FEC

            
            	bool "Verity forward error correction support"

            
            	depends on DM_VERITY

            
            	select REED_SOLOMON

            
            	select REED_SOLOMON_DEC8

            
            	---help---

            
            	  Add forward error correction support to dm-verity. This option

            
            	  makes it possible to use pre-generated error correction data to

            
            	  recover from corrupted blocks.


            	  If unsure, say N.


            config DM_SWITCH

            
            	tristate "Switch target support (EXPERIMENTAL)"

            
            	depends on BLK_DEV_DM

            
            	---help---

            
            	  This device-mapper target creates a device that supports an arbitrary

            
            	  mapping of fixed-size regions of I/O across a fixed set of paths.

            
            	  The path used for any specific region can be switched dynamically

            
            	  by sending the target a message.


            	  To compile this code as a module, choose M here: the module will

            
            	  be called dm-switch.


            	  If unsure, say N.


            config DM_LOG_WRITES

            
            	tristate "Log writes target support"

            
            	depends on BLK_DEV_DM

            
            	---help---

            
            	  This device-mapper target takes two devices, one device to use

            
            	  normally, one to log all write operations done to the first device.

            
            	  This is for use by file system developers wishing to verify that

            
            	  their fs is writing a consistent file system at all times by allowing

            
            	  them to replay the log in a variety of ways and to check the

            
            	  contents.


            	  To compile this code as a module, choose M here: the module will

            
            	  be called dm-log-writes.


            	  If unsure, say N.


            endif # MD
	#
	# Block device driver configuration
	#

	menuconfig MD
	bool "Multiple devices driver support (RAID and LVM)"
	depends on BLOCK
	select SRCU
	help
	Support multiple physical spindles through a single logical device.
	Required for RAID and logical volume management.

	if MD

	config BLK_DEV_MD
	tristate "RAID support"
	---help---
	This driver lets you combine several hard disk partitions into one
	logical block device. This can be used to simply append one
	partition to another one or to combine several redundant hard disks
	into a RAID1/4/5 device so as to provide protection against hard
	disk failures. This is called "Software RAID" since the combining of
	the partitions is done by the kernel. "Hardware RAID" means that the
	combining is done by a dedicated controller; if you have such a
	controller, you do not need to say Y here.

	More information about Software RAID on Linux is contained in the
	Software RAID mini-HOWTO, available from
	<http://www.tldp.org/docs.html#howto>. There you will also learn
	where to get the supporting user space utilities raidtools.

	If unsure, say N.

	config MD_AUTODETECT
	bool "Autodetect RAID arrays during kernel boot"
	depends on BLK_DEV_MD=y
	default y
	---help---
	If you say Y here, then the kernel will try to autodetect raid
	arrays as part of its boot process.

	If you don't use raid and say Y, this autodetection can cause
	a several-second delay in the boot time due to various
	synchronisation steps that are part of this step.

	If unsure, say Y.

	config MD_LINEAR
	tristate "Linear (append) mode"
	depends on BLK_DEV_MD
	---help---
	If you say Y here, then your multiple devices driver will be able to
	use the so-called linear mode, i.e. it will combine the hard disk
	partitions by simply appending one to the other.

	To compile this as a module, choose M here: the module
	will be called linear.

	If unsure, say Y.

	config MD_RAID0
	tristate "RAID-0 (striping) mode"
	depends on BLK_DEV_MD
	---help---
	If you say Y here, then your multiple devices driver will be able to
	use the so-called raid0 mode, i.e. it will combine the hard disk
	partitions into one logical device in such a fashion as to fill them
	up evenly, one chunk here and one chunk there. This will increase
	the throughput rate if the partitions reside on distinct disks.

	Information about Software RAID on Linux is contained in the
	Software-RAID mini-HOWTO, available from
	<http://www.tldp.org/docs.html#howto>. There you will also
	learn where to get the supporting user space utilities raidtools.

	To compile this as a module, choose M here: the module
	will be called raid0.

	If unsure, say Y.

	config MD_RAID1
	tristate "RAID-1 (mirroring) mode"
	depends on BLK_DEV_MD
	---help---
	A RAID-1 set consists of several disk drives which are exact copies
	of each other. In the event of a mirror failure, the RAID driver
	will continue to use the operational mirrors in the set, providing
	an error free MD (multiple device) to the higher levels of the
	kernel. In a set with N drives, the available space is the capacity
	of a single drive, and the set protects against a failure of (N - 1)
	drives.

	Information about Software RAID on Linux is contained in the
	Software-RAID mini-HOWTO, available from
	<http://www.tldp.org/docs.html#howto>. There you will also
	learn where to get the supporting user space utilities raidtools.

	If you want to use such a RAID-1 set, say Y. To compile this code
	as a module, choose M here: the module will be called raid1.

	If unsure, say Y.

	config MD_RAID10
	tristate "RAID-10 (mirrored striping) mode"
	depends on BLK_DEV_MD
	---help---
	RAID-10 provides a combination of striping (RAID-0) and
	mirroring (RAID-1) with easier configuration and more flexible
	layout.
	Unlike RAID-0, but like RAID-1, RAID-10 requires all devices to
	be the same size (or at least, only as much as the smallest device
	will be used).
	RAID-10 provides a variety of layouts that provide different levels
	of redundancy and performance.

	RAID-10 requires mdadm-1.7.0 or later, available at:

	ftp://ftp.kernel.org/pub/linux/utils/raid/mdadm/

	If unsure, say Y.

	config MD_RAID456
	tristate "RAID-4/RAID-5/RAID-6 mode"
	depends on BLK_DEV_MD
	select RAID6_PQ
	select LIBCRC32C
	select ASYNC_MEMCPY
	select ASYNC_XOR
	select ASYNC_PQ
	select ASYNC_RAID6_RECOV
	---help---
	A RAID-5 set of N drives with a capacity of C MB per drive provides
	the capacity of C * (N - 1) MB, and protects against a failure
	of a single drive. For a given sector (row) number, (N - 1) drives
	contain data sectors, and one drive contains the parity protection.
	For a RAID-4 set, the parity blocks are present on a single drive,
	while a RAID-5 set distributes the parity across the drives in one
	of the available parity distribution methods.

	A RAID-6 set of N drives with a capacity of C MB per drive
	provides the capacity of C * (N - 2) MB, and protects
	against a failure of any two drives. For a given sector
	(row) number, (N - 2) drives contain data sectors, and two
	drives contains two independent redundancy syndromes. Like
	RAID-5, RAID-6 distributes the syndromes across the drives
	in one of the available parity distribution methods.

	Information about Software RAID on Linux is contained in the
	Software-RAID mini-HOWTO, available from
	<http://www.tldp.org/docs.html#howto>. There you will also
	learn where to get the supporting user space utilities raidtools.

	If you want to use such a RAID-4/RAID-5/RAID-6 set, say Y. To
	compile this code as a module, choose M here: the module
	will be called raid456.

	If unsure, say Y.

	config MD_MULTIPATH
	tristate "Multipath I/O support"
	depends on BLK_DEV_MD
	help
	MD_MULTIPATH provides a simple multi-path personality for use
	the MD framework. It is not under active development. New
	projects should consider using DM_MULTIPATH which has more
	features and more testing.

	If unsure, say N.

	config MD_FAULTY
	tristate "Faulty test module for MD"
	depends on BLK_DEV_MD
	help
	The "faulty" module allows for a block device that occasionally returns
	read or write errors. It is useful for testing.

	In unsure, say N.


	config MD_CLUSTER
	tristate "Cluster Support for MD (EXPERIMENTAL)"
	depends on BLK_DEV_MD
	depends on DLM
	default n
	---help---
	Clustering support for MD devices. This enables locking and
	synchronization across multiple systems on the cluster, so all
	nodes in the cluster can access the MD devices simultaneously.

	This brings the redundancy (and uptime) of RAID levels across the
	nodes of the cluster.

	If unsure, say N.

	source "drivers/md/bcache/Kconfig"

	config BLK_DEV_DM_BUILTIN
	bool

	config BLK_DEV_DM
	tristate "Device mapper support"
	select BLK_DEV_DM_BUILTIN
	---help---
	Device-mapper is a low level volume manager. It works by allowing
	people to specify mappings for ranges of logical sectors. Various
	mapping types are available, in addition people may write their own
	modules containing custom mappings if they wish.

	Higher level volume managers such as LVM2 use this driver.

	To compile this as a module, choose M here: the module will be
	called dm-mod.

	If unsure, say N.

	config DM_MQ_DEFAULT
	bool "request-based DM: use blk-mq I/O path by default"
	depends on BLK_DEV_DM
	---help---
	This option enables the blk-mq based I/O path for request-based
	DM devices by default. With the option the dm_mod.use_blk_mq
	module/boot option defaults to Y, without it to N, but it can
	still be overriden either way.

	If unsure say N.

	config DM_DEBUG
	bool "Device mapper debugging support"
	depends on BLK_DEV_DM
	---help---
	Enable this for messages that may help debug device-mapper problems.

	If unsure, say N.

	config DM_BUFIO
	tristate
	depends on BLK_DEV_DM
	---help---
	This interface allows you to do buffered I/O on a device and acts
	as a cache, holding recently-read blocks in memory and performing
	delayed writes.

	config DM_DEBUG_BLOCK_STACK_TRACING
	bool "Keep stack trace of persistent data block lock holders"
	depends on STACKTRACE_SUPPORT && DM_BUFIO
	select STACKTRACE
	---help---
	Enable this for messages that may help debug problems with the
	block manager locking used by thin provisioning and caching.

	If unsure, say N.

	config DM_BIO_PRISON
	tristate
	depends on BLK_DEV_DM
	---help---
	Some bio locking schemes used by other device-mapper targets
	including thin provisioning.

	source "drivers/md/persistent-data/Kconfig"

	config DM_CRYPT
	tristate "Crypt target support"
	depends on BLK_DEV_DM
	select CRYPTO
	select CRYPTO_CBC
	---help---
	This device-mapper target allows you to create a device that
	transparently encrypts the data on it. You'll need to activate
	the ciphers you're going to use in the cryptoapi configuration.

	For further information on dm-crypt and userspace tools see:
	<https://gitlab.com/cryptsetup/cryptsetup/wikis/DMCrypt>

	To compile this code as a module, choose M here: the module will
	be called dm-crypt.

	If unsure, say N.

	config DM_SNAPSHOT
	tristate "Snapshot target"
	depends on BLK_DEV_DM
	select DM_BUFIO
	---help---
	Allow volume managers to take writable snapshots of a device.

	config DM_THIN_PROVISIONING
	tristate "Thin provisioning target"
	depends on BLK_DEV_DM
	select DM_PERSISTENT_DATA
	select DM_BIO_PRISON
	---help---
	Provides thin provisioning and snapshots that share a data store.

	config DM_CACHE
	tristate "Cache target (EXPERIMENTAL)"
	depends on BLK_DEV_DM
	default n
	select DM_PERSISTENT_DATA
	select DM_BIO_PRISON
	---help---
	dm-cache attempts to improve performance of a block device by
	moving frequently used data to a smaller, higher performance
	device. Different 'policy' plugins can be used to change the
	algorithms used to select which blocks are promoted, demoted,
	cleaned etc. It supports writeback and writethrough modes.

	config DM_CACHE_SMQ
	tristate "Stochastic MQ Cache Policy (EXPERIMENTAL)"
	depends on DM_CACHE
	default y
	---help---
	A cache policy that uses a multiqueue ordered by recent hits
	to select which blocks should be promoted and demoted.
	This is meant to be a general purpose policy. It prioritises
	reads over writes. This SMQ policy (vs MQ) offers the promise
	of less memory utilization, improved performance and increased
	adaptability in the face of changing workloads.

	config DM_CACHE_CLEANER
	tristate "Cleaner Cache Policy (EXPERIMENTAL)"
	depends on DM_CACHE
	default y
	---help---
	A simple cache policy that writes back all data to the
	origin. Used when decommissioning a dm-cache.

	config DM_ERA
	tristate "Era target (EXPERIMENTAL)"
	depends on BLK_DEV_DM
	default n
	select DM_PERSISTENT_DATA
	select DM_BIO_PRISON
	---help---
	dm-era tracks which parts of a block device are written to
	over time. Useful for maintaining cache coherency when using
	vendor snapshots.

	config DM_MIRROR
	tristate "Mirror target"
	depends on BLK_DEV_DM
	---help---
	Allow volume managers to mirror logical volumes, also
	needed for live data migration tools such as 'pvmove'.

	config DM_LOG_USERSPACE
	tristate "Mirror userspace logging"
	depends on DM_MIRROR && NET
	select CONNECTOR
	---help---
	The userspace logging module provides a mechanism for
	relaying the dm-dirty-log API to userspace. Log designs
	which are more suited to userspace implementation (e.g.
	shared storage logs) or experimental logs can be implemented
	by leveraging this framework.

	config DM_RAID
	tristate "RAID 1/4/5/6/10 target"
	depends on BLK_DEV_DM
	select MD_RAID1
	select MD_RAID10
	select MD_RAID456
	select BLK_DEV_MD
	---help---
	A dm target that supports RAID1, RAID10, RAID4, RAID5 and RAID6 mappings

	A RAID-5 set of N drives with a capacity of C MB per drive provides
	the capacity of C * (N - 1) MB, and protects against a failure
	of a single drive. For a given sector (row) number, (N - 1) drives
	contain data sectors, and one drive contains the parity protection.
	For a RAID-4 set, the parity blocks are present on a single drive,
	while a RAID-5 set distributes the parity across the drives in one
	of the available parity distribution methods.

	A RAID-6 set of N drives with a capacity of C MB per drive
	provides the capacity of C * (N - 2) MB, and protects
	against a failure of any two drives. For a given sector
	(row) number, (N - 2) drives contain data sectors, and two
	drives contains two independent redundancy syndromes. Like
	RAID-5, RAID-6 distributes the syndromes across the drives
	in one of the available parity distribution methods.

	config DM_ZERO
	tristate "Zero target"
	depends on BLK_DEV_DM
	---help---
	A target that discards writes, and returns all zeroes for
	reads. Useful in some recovery situations.

	config DM_MULTIPATH
	tristate "Multipath target"
	depends on BLK_DEV_DM
	# nasty syntax but means make DM_MULTIPATH independent
	# of SCSI_DH if the latter isn't defined but if
	# it is, DM_MULTIPATH must depend on it. We get a build
	# error if SCSI_DH=m and DM_MULTIPATH=y
	depends on !SCSI_DH \|\| SCSI
	---help---
	Allow volume managers to support multipath hardware.

	config DM_MULTIPATH_QL
	tristate "I/O Path Selector based on the number of in-flight I/Os"
	depends on DM_MULTIPATH
	---help---
	This path selector is a dynamic load balancer which selects
	the path with the least number of in-flight I/Os.

	If unsure, say N.

	config DM_MULTIPATH_ST
	tristate "I/O Path Selector based on the service time"
	depends on DM_MULTIPATH
	---help---
	This path selector is a dynamic load balancer which selects
	the path expected to complete the incoming I/O in the shortest
	time.

	If unsure, say N.

	config DM_DELAY
	tristate "I/O delaying target"
	depends on BLK_DEV_DM
	---help---
	A target that delays reads and/or writes and can send
	them to different devices. Useful for testing.

	If unsure, say N.

	config DM_UEVENT
	bool "DM uevents"
	depends on BLK_DEV_DM
	---help---
	Generate udev events for DM events.

	config DM_FLAKEY
	tristate "Flakey target"
	depends on BLK_DEV_DM
	---help---
	A target that intermittently fails I/O for debugging purposes.

	config DM_VERITY
	tristate "Verity target support"
	depends on BLK_DEV_DM
	select CRYPTO
	select CRYPTO_HASH
	select DM_BUFIO
	---help---
	This device-mapper target creates a read-only device that
	transparently validates the data on one underlying device against
	a pre-generated tree of cryptographic checksums stored on a second
	device.

	You'll need to activate the digests you're going to use in the
	cryptoapi configuration.

	To compile this code as a module, choose M here: the module will
	be called dm-verity.

	If unsure, say N.

	config DM_VERITY_FEC
	bool "Verity forward error correction support"
	depends on DM_VERITY
	select REED_SOLOMON
	select REED_SOLOMON_DEC8
	---help---
	Add forward error correction support to dm-verity. This option
	makes it possible to use pre-generated error correction data to
	recover from corrupted blocks.

	If unsure, say N.

	config DM_SWITCH
	tristate "Switch target support (EXPERIMENTAL)"
	depends on BLK_DEV_DM
	---help---
	This device-mapper target creates a device that supports an arbitrary
	mapping of fixed-size regions of I/O across a fixed set of paths.
	The path used for any specific region can be switched dynamically
	by sending the target a message.

	To compile this code as a module, choose M here: the module will
	be called dm-switch.

	If unsure, say N.

	config DM_LOG_WRITES
	tristate "Log writes target support"
	depends on BLK_DEV_DM
	---help---
	This device-mapper target takes two devices, one device to use
	normally, one to log all write operations done to the first device.
	This is for use by file system developers wishing to verify that
	their fs is writing a consistent file system at all times by allowing
	them to replay the log in a variety of ways and to check the
	contents.

	To compile this code as a module, choose M here: the module will
	be called dm-log-writes.

	If unsure, say N.

	endif # MD