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9361401eb7
Make it possible to disable the block layer. Not all embedded devices require
it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require
the block layer to be present.
This patch does the following:
(*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev
support.
(*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls
an item that uses the block layer. This includes:
(*) Block I/O tracing.
(*) Disk partition code.
(*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS.
(*) The SCSI layer. As far as I can tell, even SCSI chardevs use the
block layer to do scheduling. Some drivers that use SCSI facilities -
such as USB storage - end up disabled indirectly from this.
(*) Various block-based device drivers, such as IDE and the old CDROM
drivers.
(*) MTD blockdev handling and FTL.
(*) JFFS - which uses set_bdev_super(), something it could avoid doing by
taking a leaf out of JFFS2's book.
(*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and
linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is,
however, still used in places, and so is still available.
(*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and
parts of linux/fs.h.
(*) Makes a number of files in fs/ contingent on CONFIG_BLOCK.
(*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK.
(*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK
is not enabled.
(*) fs/no-block.c is created to hold out-of-line stubs and things that are
required when CONFIG_BLOCK is not set:
(*) Default blockdev file operations (to give error ENODEV on opening).
(*) Makes some /proc changes:
(*) /proc/devices does not list any blockdevs.
(*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK.
(*) Makes some compat ioctl handling contingent on CONFIG_BLOCK.
(*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if
given command other than Q_SYNC or if a special device is specified.
(*) In init/do_mounts.c, no reference is made to the blockdev routines if
CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2.
(*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return
error ENOSYS by way of cond_syscall if so).
(*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if
CONFIG_BLOCK is not set, since they can't then happen.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
256 lines
8.9 KiB
Text
256 lines
8.9 KiB
Text
#
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# Block device driver configuration
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#
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if BLOCK
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menu "Multi-device support (RAID and LVM)"
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config MD
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bool "Multiple devices driver support (RAID and LVM)"
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help
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Support multiple physical spindles through a single logical device.
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Required for RAID and logical volume management.
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config BLK_DEV_MD
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tristate "RAID support"
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depends on MD
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---help---
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This driver lets you combine several hard disk partitions into one
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logical block device. This can be used to simply append one
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partition to another one or to combine several redundant hard disks
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into a RAID1/4/5 device so as to provide protection against hard
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disk failures. This is called "Software RAID" since the combining of
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the partitions is done by the kernel. "Hardware RAID" means that the
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combining is done by a dedicated controller; if you have such a
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controller, you do not need to say Y here.
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More information about Software RAID on Linux is contained in the
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Software RAID mini-HOWTO, available from
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<http://www.tldp.org/docs.html#howto>. There you will also learn
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where to get the supporting user space utilities raidtools.
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If unsure, say N.
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config MD_LINEAR
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tristate "Linear (append) mode"
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depends on BLK_DEV_MD
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---help---
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If you say Y here, then your multiple devices driver will be able to
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use the so-called linear mode, i.e. it will combine the hard disk
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partitions by simply appending one to the other.
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To compile this as a module, choose M here: the module
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will be called linear.
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If unsure, say Y.
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config MD_RAID0
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tristate "RAID-0 (striping) mode"
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depends on BLK_DEV_MD
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---help---
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If you say Y here, then your multiple devices driver will be able to
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use the so-called raid0 mode, i.e. it will combine the hard disk
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partitions into one logical device in such a fashion as to fill them
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up evenly, one chunk here and one chunk there. This will increase
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the throughput rate if the partitions reside on distinct disks.
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Information about Software RAID on Linux is contained in the
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Software-RAID mini-HOWTO, available from
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<http://www.tldp.org/docs.html#howto>. There you will also
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learn where to get the supporting user space utilities raidtools.
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To compile this as a module, choose M here: the module
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will be called raid0.
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If unsure, say Y.
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config MD_RAID1
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tristate "RAID-1 (mirroring) mode"
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depends on BLK_DEV_MD
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---help---
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A RAID-1 set consists of several disk drives which are exact copies
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of each other. In the event of a mirror failure, the RAID driver
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will continue to use the operational mirrors in the set, providing
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an error free MD (multiple device) to the higher levels of the
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kernel. In a set with N drives, the available space is the capacity
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of a single drive, and the set protects against a failure of (N - 1)
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drives.
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Information about Software RAID on Linux is contained in the
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Software-RAID mini-HOWTO, available from
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<http://www.tldp.org/docs.html#howto>. There you will also
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learn where to get the supporting user space utilities raidtools.
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If you want to use such a RAID-1 set, say Y. To compile this code
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as a module, choose M here: the module will be called raid1.
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If unsure, say Y.
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config MD_RAID10
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tristate "RAID-10 (mirrored striping) mode (EXPERIMENTAL)"
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depends on BLK_DEV_MD && EXPERIMENTAL
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---help---
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RAID-10 provides a combination of striping (RAID-0) and
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mirroring (RAID-1) with easier configuration and more flexible
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layout.
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Unlike RAID-0, but like RAID-1, RAID-10 requires all devices to
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be the same size (or at least, only as much as the smallest device
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will be used).
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RAID-10 provides a variety of layouts that provide different levels
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of redundancy and performance.
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RAID-10 requires mdadm-1.7.0 or later, available at:
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ftp://ftp.kernel.org/pub/linux/utils/raid/mdadm/
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If unsure, say Y.
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config MD_RAID456
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tristate "RAID-4/RAID-5/RAID-6 mode"
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depends on BLK_DEV_MD
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---help---
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A RAID-5 set of N drives with a capacity of C MB per drive provides
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the capacity of C * (N - 1) MB, and protects against a failure
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of a single drive. For a given sector (row) number, (N - 1) drives
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contain data sectors, and one drive contains the parity protection.
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For a RAID-4 set, the parity blocks are present on a single drive,
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while a RAID-5 set distributes the parity across the drives in one
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of the available parity distribution methods.
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A RAID-6 set of N drives with a capacity of C MB per drive
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provides the capacity of C * (N - 2) MB, and protects
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against a failure of any two drives. For a given sector
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(row) number, (N - 2) drives contain data sectors, and two
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drives contains two independent redundancy syndromes. Like
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RAID-5, RAID-6 distributes the syndromes across the drives
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in one of the available parity distribution methods.
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Information about Software RAID on Linux is contained in the
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Software-RAID mini-HOWTO, available from
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<http://www.tldp.org/docs.html#howto>. There you will also
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learn where to get the supporting user space utilities raidtools.
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If you want to use such a RAID-4/RAID-5/RAID-6 set, say Y. To
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compile this code as a module, choose M here: the module
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will be called raid456.
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If unsure, say Y.
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config MD_RAID5_RESHAPE
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bool "Support adding drives to a raid-5 array (experimental)"
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depends on MD_RAID456 && EXPERIMENTAL
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---help---
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A RAID-5 set can be expanded by adding extra drives. This
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requires "restriping" the array which means (almost) every
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block must be written to a different place.
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This option allows such restriping to be done while the array
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is online. However it is still EXPERIMENTAL code. It should
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work, but please be sure that you have backups.
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You will need mdadm version 2.4.1 or later to use this
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feature safely. During the early stage of reshape there is
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a critical section where live data is being over-written. A
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crash during this time needs extra care for recovery. The
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newer mdadm takes a copy of the data in the critical section
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and will restore it, if necessary, after a crash.
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The mdadm usage is e.g.
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mdadm --grow /dev/md1 --raid-disks=6
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to grow '/dev/md1' to having 6 disks.
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Note: The array can only be expanded, not contracted.
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There should be enough spares already present to make the new
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array workable.
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config MD_MULTIPATH
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tristate "Multipath I/O support"
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depends on BLK_DEV_MD
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help
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Multipath-IO is the ability of certain devices to address the same
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physical disk over multiple 'IO paths'. The code ensures that such
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paths can be defined and handled at runtime, and ensures that a
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transparent failover to the backup path(s) happens if a IO errors
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arrives on the primary path.
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If unsure, say N.
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config MD_FAULTY
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tristate "Faulty test module for MD"
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depends on BLK_DEV_MD
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help
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The "faulty" module allows for a block device that occasionally returns
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read or write errors. It is useful for testing.
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In unsure, say N.
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config BLK_DEV_DM
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tristate "Device mapper support"
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depends on MD
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---help---
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Device-mapper is a low level volume manager. It works by allowing
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people to specify mappings for ranges of logical sectors. Various
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mapping types are available, in addition people may write their own
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modules containing custom mappings if they wish.
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Higher level volume managers such as LVM2 use this driver.
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To compile this as a module, choose M here: the module will be
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called dm-mod.
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If unsure, say N.
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config DM_CRYPT
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tristate "Crypt target support"
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depends on BLK_DEV_DM && EXPERIMENTAL
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select CRYPTO
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---help---
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This device-mapper target allows you to create a device that
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transparently encrypts the data on it. You'll need to activate
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the ciphers you're going to use in the cryptoapi configuration.
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Information on how to use dm-crypt can be found on
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<http://www.saout.de/misc/dm-crypt/>
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To compile this code as a module, choose M here: the module will
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be called dm-crypt.
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If unsure, say N.
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config DM_SNAPSHOT
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tristate "Snapshot target (EXPERIMENTAL)"
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depends on BLK_DEV_DM && EXPERIMENTAL
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---help---
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Allow volume managers to take writable snapshots of a device.
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config DM_MIRROR
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tristate "Mirror target (EXPERIMENTAL)"
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depends on BLK_DEV_DM && EXPERIMENTAL
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---help---
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Allow volume managers to mirror logical volumes, also
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needed for live data migration tools such as 'pvmove'.
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config DM_ZERO
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tristate "Zero target (EXPERIMENTAL)"
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depends on BLK_DEV_DM && EXPERIMENTAL
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---help---
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A target that discards writes, and returns all zeroes for
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reads. Useful in some recovery situations.
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config DM_MULTIPATH
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tristate "Multipath target (EXPERIMENTAL)"
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depends on BLK_DEV_DM && EXPERIMENTAL
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---help---
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Allow volume managers to support multipath hardware.
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config DM_MULTIPATH_EMC
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tristate "EMC CX/AX multipath support (EXPERIMENTAL)"
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depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL
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---help---
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Multipath support for EMC CX/AX series hardware.
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endmenu
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endif
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