Jetpack/kernel/kernel-4.9/drivers/md/Kconfig

#
# 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_RAID0
       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_HASH_PREFETCH_MIN_SIZE_128
	bool "Prefetch size 128"

config DM_VERITY_HASH_PREFETCH_MIN_SIZE
	int "Verity hash prefetch minimum size"
	depends on DM_VERITY
	range 1 4096
	default 128 if DM_VERITY_HASH_PREFETCH_MIN_SIZE_128
	default 1
	---help---
	  This sets minimum number of hash blocks to prefetch for dm-verity.
	  For devices like eMMC, having larger prefetch size like 128 can improve
	  performance with increased memory consumption for keeping more hashes
	  in RAM.

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.

config DM_VERITY_AVB
	tristate "Support AVB specific verity error behavior"
	depends on DM_VERITY
	---help---
	  Enables Android Verified Boot platform-specific error
	  behavior. In particular, it will modify the vbmeta partition
	  specified on the kernel command-line when non-transient error
	  occurs (followed by a panic).

	  If unsure, say N.

config DM_ANDROID_VERITY
	bool "Android verity target support"
	depends on BLK_DEV_DM=y
	depends on DM_VERITY=y
	depends on X509_CERTIFICATE_PARSER
	depends on SYSTEM_TRUSTED_KEYRING
	depends on CRYPTO_RSA
	depends on KEYS
	depends on ASYMMETRIC_KEY_TYPE
	depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE
	select DM_VERITY_HASH_PREFETCH_MIN_SIZE_128
	---help---
	  This device-mapper target is virtually a VERITY target. This
	  target is setup by reading the metadata contents piggybacked
	  to the actual data blocks in the block device. The signature
	  of the metadata contents are verified against the key included
	  in the system keyring. Upon success, the underlying verity
	  target is setup.

config DM_ANDROID_VERITY_AT_MOST_ONCE_DEFAULT_ENABLED
	bool "Verity will validate blocks at most once"
	depends on DM_VERITY
	---help---
	  Default enables at_most_once option for dm-verity

	  Verify data blocks only the first time they are read from the
	  data device, rather than every time.  This reduces the overhead
	  of dm-verity so that it can be used on systems that are memory
	  and/or CPU constrained.  However, it provides a reduced level
	  of security because only offline tampering of the data device's
	  content will be detected, not online tampering.

	  Hash blocks are still verified each time they are read from the
	  hash device, since verification of hash blocks is less performance
	  critical than data blocks, and a hash block will not be verified
	  any more after all the data blocks it covers have been verified anyway.

	  If unsure, say N.
endif # MD