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9db5579be4
linux/drivers/block/Kconfig
Nick Piggin 9db5579be4 rewrite rd 
This is a rewrite of the ramdisk block device driver.

The old one is really difficult because it effectively implements a block
device which serves data out of its own buffer cache.  It relies on the dirty
bit being set, to pin its backing store in cache, however there are non
trivial paths which can clear the dirty bit (eg.  try_to_free_buffers()),
which had recently lead to data corruption.  And in general it is completely
wrong for a block device driver to do this.

The new one is more like a regular block device driver.  It has no idea about
vm/vfs stuff.  It's backing store is similar to the buffer cache (a simple
radix-tree of pages), but it doesn't know anything about page cache (the pages
in the radix tree are not pagecache pages).

There is one slight downside -- direct block device access and filesystem
metadata access goes through an extra copy and gets stored in RAM twice.
However, this downside is only slight, because the real buffercache of the
device is now reclaimable (because we're not playing crazy games with it), so
under memory intensive situations, footprint should effectively be the same --
maybe even a slight advantage to the new driver because it can also reclaim
buffer heads.

The fact that it now goes through all the regular vm/fs paths makes it
much more useful for testing, too.

   text    data     bss     dec     hex filename
   2837     849     384    4070     fe6 drivers/block/rd.o
   3528     371      12    3911     f47 drivers/block/brd.o

Text is larger, but data and bss are smaller, making total size smaller.

A few other nice things about it:
- Similar structure and layout to the new loop device handlinag.
- Dynamic ramdisk creation.
- Runtime flexible buffer head size (because it is no longer part of the
  ramdisk code).
- Boot / load time flexible ramdisk size, which could easily be extended
  to a per-ramdisk runtime changeable size (eg. with an ioctl).
- Can use highmem for the backing store.

[akpm@linux-foundation.org: fix build]
[byron.bbradley@gmail.com: make rd_size non-static]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Byron Bradley <byron.bbradley@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:30 -08:00

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#
# Block device driver configuration
#
menuconfig BLK_DEV
bool "Block devices"
depends on BLOCK
default y
---help---
Say Y here to get to see options for various different block device
drivers. This option alone does not add any kernel code.
If you say N, all options in this submenu will be skipped and disabled;
only do this if you know what you are doing.
if BLK_DEV
config BLK_DEV_FD
tristate "Normal floppy disk support"
depends on ARCH_MAY_HAVE_PC_FDC
---help---
If you want to use the floppy disk drive(s) of your PC under Linux,
say Y. Information about this driver, especially important for IBM
Thinkpad users, is contained in <file:Documentation/floppy.txt>.
That file also contains the location of the Floppy driver FAQ as
well as location of the fdutils package used to configure additional
parameters of the driver at run time.
To compile this driver as a module, choose M here: the
module will be called floppy.
config AMIGA_FLOPPY
tristate "Amiga floppy support"
depends on AMIGA
config ATARI_FLOPPY
tristate "Atari floppy support"
depends on ATARI
config MAC_FLOPPY
tristate "Support for PowerMac floppy"
depends on PPC_PMAC && !PPC_PMAC64
help
If you have a SWIM-3 (Super Woz Integrated Machine 3; from Apple)
floppy controller, say Y here. Most commonly found in PowerMacs.
config BLK_DEV_PS2
tristate "PS/2 ESDI hard disk support"
depends on MCA && MCA_LEGACY && BROKEN
help
Say Y here if you have a PS/2 machine with a MCA bus and an ESDI
hard disk.
To compile this driver as a module, choose M here: the
module will be called ps2esdi.
config AMIGA_Z2RAM
tristate "Amiga Zorro II ramdisk support"
depends on ZORRO
help
This enables support for using Chip RAM and Zorro II RAM as a
ramdisk or as a swap partition. Say Y if you want to include this
driver in the kernel.
To compile this driver as a module, choose M here: the
module will be called z2ram.
config BLK_DEV_XD
tristate "XT hard disk support"
depends on ISA && ISA_DMA_API
select CHECK_SIGNATURE
help
Very old 8 bit hard disk controllers used in the IBM XT computer
will be supported if you say Y here.
To compile this driver as a module, choose M here: the
module will be called xd.
It's pretty unlikely that you have one of these: say N.
config PARIDE
tristate "Parallel port IDE device support"
depends on PARPORT_PC
---help---
There are many external CD-ROM and disk devices that connect through
your computer's parallel port. Most of them are actually IDE devices
using a parallel port IDE adapter. This option enables the PARIDE
subsystem which contains drivers for many of these external drives.
Read <file:Documentation/paride.txt> for more information.
If you have said Y to the "Parallel-port support" configuration
option, you may share a single port between your printer and other
parallel port devices. Answer Y to build PARIDE support into your
kernel, or M if you would like to build it as a loadable module. If
your parallel port support is in a loadable module, you must build
PARIDE as a module. If you built PARIDE support into your kernel,
you may still build the individual protocol modules and high-level
drivers as loadable modules. If you build this support as a module,
it will be called paride.
To use the PARIDE support, you must say Y or M here and also to at
least one high-level driver (e.g. "Parallel port IDE disks",
"Parallel port ATAPI CD-ROMs", "Parallel port ATAPI disks" etc.) and
to at least one protocol driver (e.g. "ATEN EH-100 protocol",
"MicroSolutions backpack protocol", "DataStor Commuter protocol"
etc.).
config GDROM
tristate "SEGA Dreamcast GD-ROM drive"
depends on SH_DREAMCAST
help
A standard SEGA Dreamcast comes with a modified CD ROM drive called a
"GD-ROM" by SEGA to signify it is capable of reading special disks
with up to 1 GB of data. This drive will also read standard CD ROM
disks. Select this option to access any disks in your GD ROM drive.
Most users will want to say "Y" here.
You can also build this as a module which will be called gdrom.ko
source "drivers/block/paride/Kconfig"
config BLK_CPQ_DA
tristate "Compaq SMART2 support"
depends on PCI && VIRT_TO_BUS
help
This is the driver for Compaq Smart Array controllers. Everyone
using these boards should say Y here. See the file
<file:Documentation/cpqarray.txt> for the current list of boards
supported by this driver, and for further information on the use of
this driver.
config BLK_CPQ_CISS_DA
tristate "Compaq Smart Array 5xxx support"
depends on PCI
help
This is the driver for Compaq Smart Array 5xxx controllers.
Everyone using these boards should say Y here.
See <file:Documentation/cciss.txt> for the current list of
boards supported by this driver, and for further information
on the use of this driver.
config CISS_SCSI_TAPE
bool "SCSI tape drive support for Smart Array 5xxx"
depends on BLK_CPQ_CISS_DA && PROC_FS
depends on SCSI=y || SCSI=BLK_CPQ_CISS_DA
help
When enabled (Y), this option allows SCSI tape drives and SCSI medium
changers (tape robots) to be accessed via a Compaq 5xxx array
controller. (See <file:Documentation/cciss.txt> for more details.)
"SCSI support" and "SCSI tape support" must also be enabled for this
option to work.
When this option is disabled (N), the SCSI portion of the driver
is not compiled.
config BLK_DEV_DAC960
tristate "Mylex DAC960/DAC1100 PCI RAID Controller support"
depends on PCI
help
This driver adds support for the Mylex DAC960, AcceleRAID, and
eXtremeRAID PCI RAID controllers. See the file
<file:Documentation/README.DAC960> for further information about
this driver.
To compile this driver as a module, choose M here: the
module will be called DAC960.
config BLK_DEV_UMEM
tristate "Micro Memory MM5415 Battery Backed RAM support (EXPERIMENTAL)"
depends on PCI && EXPERIMENTAL
---help---
Saying Y here will include support for the MM5415 family of
battery backed (Non-volatile) RAM cards.
<http://www.umem.com/>
The cards appear as block devices that can be partitioned into
as many as 15 partitions.
To compile this driver as a module, choose M here: the
module will be called umem.
The umem driver has not yet been allocated a MAJOR number, so
one is chosen dynamically.
config BLK_DEV_UBD
bool "Virtual block device"
depends on UML
---help---
The User-Mode Linux port includes a driver called UBD which will let
you access arbitrary files on the host computer as block devices.
Unless you know that you do not need such virtual block devices say
Y here.
config BLK_DEV_UBD_SYNC
bool "Always do synchronous disk IO for UBD"
depends on BLK_DEV_UBD
---help---
Writes to the virtual block device are not immediately written to the
host's disk; this may cause problems if, for example, the User-Mode
Linux 'Virtual Machine' uses a journalling filesystem and the host
computer crashes.
Synchronous operation (i.e. always writing data to the host's disk
immediately) is configurable on a per-UBD basis by using a special
kernel command line option. Alternatively, you can say Y here to
turn on synchronous operation by default for all block devices.
If you're running a journalling file system (like reiserfs, for
example) in your virtual machine, you will want to say Y here. If
you care for the safety of the data in your virtual machine, Y is a
wise choice too. In all other cases (for example, if you're just
playing around with User-Mode Linux) you can choose N.
config BLK_DEV_COW_COMMON
bool
default BLK_DEV_UBD
config BLK_DEV_LOOP
tristate "Loopback device support"
---help---
Saying Y here will allow you to use a regular file as a block
device; you can then create a file system on that block device and
mount it just as you would mount other block devices such as hard
drive partitions, CD-ROM drives or floppy drives. The loop devices
are block special device files with major number 7 and typically
called /dev/loop0, /dev/loop1 etc.
This is useful if you want to check an ISO 9660 file system before
burning the CD, or if you want to use floppy images without first
writing them to floppy. Furthermore, some Linux distributions avoid
the need for a dedicated Linux partition by keeping their complete
root file system inside a DOS FAT file using this loop device
driver.
To use the loop device, you need the losetup utility, found in the
util-linux package, see
<ftp://ftp.kernel.org/pub/linux/utils/util-linux/>.
The loop device driver can also be used to "hide" a file system in
a disk partition, floppy, or regular file, either using encryption
(scrambling the data) or steganography (hiding the data in the low
bits of, say, a sound file). This is also safe if the file resides
on a remote file server.
There are several ways of encrypting disks. Some of these require
kernel patches. The vanilla kernel offers the cryptoloop option
and a Device Mapper target (which is superior, as it supports all
file systems). If you want to use the cryptoloop, say Y to both
LOOP and CRYPTOLOOP, and make sure you have a recent (version 2.12
or later) version of util-linux. Additionally, be aware that
the cryptoloop is not safe for storing journaled filesystems.
Note that this loop device has nothing to do with the loopback
device used for network connections from the machine to itself.
To compile this driver as a module, choose M here: the
module will be called loop.
Most users will answer N here.
config BLK_DEV_CRYPTOLOOP
tristate "Cryptoloop Support"
select CRYPTO
select CRYPTO_CBC
depends on BLK_DEV_LOOP
---help---
Say Y here if you want to be able to use the ciphers that are
provided by the CryptoAPI as loop transformation. This might be
used as hard disk encryption.
WARNING: This device is not safe for journaled file systems like
ext3 or Reiserfs. Please use the Device Mapper crypto module
instead, which can be configured to be on-disk compatible with the
cryptoloop device.
config BLK_DEV_NBD
tristate "Network block device support"
depends on NET
---help---
Saying Y here will allow your computer to be a client for network
block devices, i.e. it will be able to use block devices exported by
servers (mount file systems on them etc.). Communication between
client and server works over TCP/IP networking, but to the client
program this is hidden: it looks like a regular local file access to
a block device special file such as /dev/nd0.
Network block devices also allows you to run a block-device in
userland (making server and client physically the same computer,
communicating using the loopback network device).
Read <file:Documentation/nbd.txt> for more information, especially
about where to find the server code, which runs in user space and
does not need special kernel support.
Note that this has nothing to do with the network file systems NFS
or Coda; you can say N here even if you intend to use NFS or Coda.
To compile this driver as a module, choose M here: the
module will be called nbd.
If unsure, say N.
config BLK_DEV_SX8
tristate "Promise SATA SX8 support"
depends on PCI
---help---
Saying Y or M here will enable support for the
Promise SATA SX8 controllers.
Use devices /dev/sx8/$N and /dev/sx8/$Np$M.
config BLK_DEV_UB
tristate "Low Performance USB Block driver"
depends on USB
help
This driver supports certain USB attached storage devices
such as flash keys.
If you enable this driver, it is recommended to avoid conflicts
with usb-storage by enabling USB_LIBUSUAL.
If unsure, say N.
config BLK_DEV_RAM
tristate "RAM block device support"
---help---
Saying Y here will allow you to use a portion of your RAM memory as
a block device, so that you can make file systems on it, read and
write to it and do all the other things that you can do with normal
block devices (such as hard drives). It is usually used to load and
store a copy of a minimal root file system off of a floppy into RAM
during the initial install of Linux.
Note that the kernel command line option "ramdisk=XX" is now
obsolete. For details, read <file:Documentation/ramdisk.txt>.
To compile this driver as a module, choose M here: the
module will be called rd.
Most normal users won't need the RAM disk functionality, and can
thus say N here.
config BLK_DEV_RAM_COUNT
int "Default number of RAM disks"
default "16"
depends on BLK_DEV_RAM
help
The default value is 16 RAM disks. Change this if you know what you
are doing. If you boot from a filesystem that needs to be extracted
in memory, you will need at least one RAM disk (e.g. root on cramfs).
config BLK_DEV_RAM_SIZE
int "Default RAM disk size (kbytes)"
depends on BLK_DEV_RAM
default "4096"
help
The default value is 4096 kilobytes. Only change this if you know
what you are doing.
config CDROM_PKTCDVD
tristate "Packet writing on CD/DVD media"
depends on !UML
help
If you have a CDROM/DVD drive that supports packet writing, say
Y to include support. It should work with any MMC/Mt Fuji
compliant ATAPI or SCSI drive, which is just about any newer
DVD/CD writer.
Currently only writing to CD-RW, DVD-RW, DVD+RW and DVDRAM discs
is possible.
DVD-RW disks must be in restricted overwrite mode.
See the file <file:Documentation/cdrom/packet-writing.txt>
for further information on the use of this driver.
To compile this driver as a module, choose M here: the
module will be called pktcdvd.
config CDROM_PKTCDVD_BUFFERS
int "Free buffers for data gathering"
depends on CDROM_PKTCDVD
default "8"
help
This controls the maximum number of active concurrent packets. More
concurrent packets can increase write performance, but also require
more memory. Each concurrent packet will require approximately 64Kb
of non-swappable kernel memory, memory which will be allocated when
a disc is opened for writing.
config CDROM_PKTCDVD_WCACHE
bool "Enable write caching (EXPERIMENTAL)"
depends on CDROM_PKTCDVD && EXPERIMENTAL
help
If enabled, write caching will be set for the CD-R/W device. For now
this option is dangerous unless the CD-RW media is known good, as we
don't do deferred write error handling yet.
config ATA_OVER_ETH
tristate "ATA over Ethernet support"
depends on NET
help
This driver provides Support for ATA over Ethernet block
devices like the Coraid EtherDrive (R) Storage Blade.
config SUNVDC
tristate "Sun Virtual Disk Client support"
depends on SUN_LDOMS
help
Support for virtual disk devices as a client under Sun
Logical Domains.
source "drivers/s390/block/Kconfig"
config XILINX_SYSACE
tristate "Xilinx SystemACE support"
depends on 4xx
help
Include support for the Xilinx SystemACE CompactFlash interface
config XEN_BLKDEV_FRONTEND
tristate "Xen virtual block device support"
depends on XEN
default y
help
This driver implements the front-end of the Xen virtual
block device driver. It communicates with a back-end driver
in another domain which drives the actual block device.
config VIRTIO_BLK
tristate "Virtio block driver (EXPERIMENTAL)"
depends on EXPERIMENTAL && VIRTIO
---help---
This is the virtual block driver for virtio. It can be used with
lguest or QEMU based VMMs (like KVM or Xen). Say Y or M.
endif # BLK_DEV
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