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This is the driver part of userspace block driver(ublk driver), the other part is userspace daemon part(ublksrv)[1]. The two parts communicate by io_uring's IORING_OP_URING_CMD with one shared cmd buffer for storing io command, and the buffer is read only for ublksrv, each io command is indexed by io request tag directly, and is written by ublk driver. For example, when one READ io request is submitted to ublk block driver, ublk driver stores the io command into cmd buffer first, then completes one IORING_OP_URING_CMD for notifying ublksrv, and the URING_CMD is issued to ublk driver beforehand by ublksrv for getting notification of any new io request, and each URING_CMD is associated with one io request by tag. After ublksrv gets the io command, it translates and handles the ublk io request, such as, for the ublk-loop target, ublksrv translates the request into same request on another file or disk, like the kernel loop block driver. In ublksrv's implementation, the io is still handled by io_uring, and share same ring with IORING_OP_URING_CMD command. When the target io request is done, the same IORING_OP_URING_CMD is issued to ublk driver for both committing io request result and getting future notification of new io request. Another thing done by ublk driver is to copy data between kernel io request and ublksrv's io buffer: 1) before ubsrv handles WRITE request, copy the request's data into ublksrv's userspace io buffer, so that ublksrv can handle the write request 2) after ubsrv handles READ request, copy ublksrv's userspace io buffer into this READ request, then ublk driver can complete the READ request Zero copy may be switched if mm is ready to support it. ublk driver doesn't handle any logic of the specific user space driver, so it is small/simple enough. [1] ublksrv https://github.com/ming1/ubdsrv Signed-off-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20220713140711.97356-2-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
423 lines
14 KiB
Plaintext
423 lines
14 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0
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#
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# Block device driver configuration
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#
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menuconfig BLK_DEV
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bool "Block devices"
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depends on BLOCK
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default y
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help
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Say Y here to get to see options for various different block device
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drivers. This option alone does not add any kernel code.
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If you say N, all options in this submenu will be skipped and disabled;
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only do this if you know what you are doing.
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if BLK_DEV
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source "drivers/block/null_blk/Kconfig"
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config BLK_DEV_FD
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tristate "Normal floppy disk support"
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depends on ARCH_MAY_HAVE_PC_FDC
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help
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If you want to use the floppy disk drive(s) of your PC under Linux,
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say Y. Information about this driver, especially important for IBM
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Thinkpad users, is contained in
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<file:Documentation/admin-guide/blockdev/floppy.rst>.
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That file also contains the location of the Floppy driver FAQ as
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well as location of the fdutils package used to configure additional
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parameters of the driver at run time.
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To compile this driver as a module, choose M here: the
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module will be called floppy.
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config BLK_DEV_FD_RAWCMD
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bool "Support for raw floppy disk commands (DEPRECATED)"
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depends on BLK_DEV_FD
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help
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If you want to use actual physical floppies and expect to do
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special low-level hardware accesses to them (access and use
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non-standard formats, for example), then enable this.
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Note that the code enabled by this option is rarely used and
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might be unstable or insecure, and distros should not enable it.
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Note: FDRAWCMD is deprecated and will be removed from the kernel
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in the near future.
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If unsure, say N.
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config AMIGA_FLOPPY
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tristate "Amiga floppy support"
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depends on AMIGA
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config ATARI_FLOPPY
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tristate "Atari floppy support"
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depends on ATARI
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config MAC_FLOPPY
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tristate "Support for PowerMac floppy"
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depends on PPC_PMAC && !PPC_PMAC64
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help
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If you have a SWIM-3 (Super Woz Integrated Machine 3; from Apple)
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floppy controller, say Y here. Most commonly found in PowerMacs.
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config BLK_DEV_SWIM
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tristate "Support for SWIM Macintosh floppy"
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depends on M68K && MAC && !HIGHMEM
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help
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You should select this option if you want floppy support
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and you don't have a II, IIfx, Q900, Q950 or AV series.
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config AMIGA_Z2RAM
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tristate "Amiga Zorro II ramdisk support"
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depends on ZORRO
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help
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This enables support for using Chip RAM and Zorro II RAM as a
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ramdisk or as a swap partition. Say Y if you want to include this
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driver in the kernel.
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To compile this driver as a module, choose M here: the
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module will be called z2ram.
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config N64CART
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bool "N64 cart support"
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depends on MACH_NINTENDO64
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help
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Support for the N64 cart.
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config CDROM
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tristate
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config GDROM
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tristate "SEGA Dreamcast GD-ROM drive"
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depends on SH_DREAMCAST
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select CDROM
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help
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A standard SEGA Dreamcast comes with a modified CD ROM drive called a
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"GD-ROM" by SEGA to signify it is capable of reading special disks
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with up to 1 GB of data. This drive will also read standard CD ROM
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disks. Select this option to access any disks in your GD ROM drive.
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Most users will want to say "Y" here.
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You can also build this as a module which will be called gdrom.
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config PARIDE
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tristate "Parallel port IDE device support"
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depends on PARPORT_PC
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help
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There are many external CD-ROM and disk devices that connect through
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your computer's parallel port. Most of them are actually IDE devices
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using a parallel port IDE adapter. This option enables the PARIDE
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subsystem which contains drivers for many of these external drives.
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Read <file:Documentation/admin-guide/blockdev/paride.rst> for more information.
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If you have said Y to the "Parallel-port support" configuration
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option, you may share a single port between your printer and other
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parallel port devices. Answer Y to build PARIDE support into your
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kernel, or M if you would like to build it as a loadable module. If
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your parallel port support is in a loadable module, you must build
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PARIDE as a module. If you built PARIDE support into your kernel,
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you may still build the individual protocol modules and high-level
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drivers as loadable modules. If you build this support as a module,
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it will be called paride.
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To use the PARIDE support, you must say Y or M here and also to at
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least one high-level driver (e.g. "Parallel port IDE disks",
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"Parallel port ATAPI CD-ROMs", "Parallel port ATAPI disks" etc.) and
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to at least one protocol driver (e.g. "ATEN EH-100 protocol",
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"MicroSolutions backpack protocol", "DataStor Commuter protocol"
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etc.).
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source "drivers/block/paride/Kconfig"
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source "drivers/block/mtip32xx/Kconfig"
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source "drivers/block/zram/Kconfig"
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config BLK_DEV_UBD
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bool "Virtual block device"
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depends on UML
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help
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The User-Mode Linux port includes a driver called UBD which will let
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you access arbitrary files on the host computer as block devices.
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Unless you know that you do not need such virtual block devices say
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Y here.
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config BLK_DEV_UBD_SYNC
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bool "Always do synchronous disk IO for UBD"
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depends on BLK_DEV_UBD
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help
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Writes to the virtual block device are not immediately written to the
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host's disk; this may cause problems if, for example, the User-Mode
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Linux 'Virtual Machine' uses a journalling filesystem and the host
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computer crashes.
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Synchronous operation (i.e. always writing data to the host's disk
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immediately) is configurable on a per-UBD basis by using a special
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kernel command line option. Alternatively, you can say Y here to
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turn on synchronous operation by default for all block devices.
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If you're running a journalling file system (like reiserfs, for
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example) in your virtual machine, you will want to say Y here. If
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you care for the safety of the data in your virtual machine, Y is a
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wise choice too. In all other cases (for example, if you're just
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playing around with User-Mode Linux) you can choose N.
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config BLK_DEV_COW_COMMON
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bool
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default BLK_DEV_UBD
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config BLK_DEV_LOOP
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tristate "Loopback device support"
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help
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Saying Y here will allow you to use a regular file as a block
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device; you can then create a file system on that block device and
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mount it just as you would mount other block devices such as hard
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drive partitions, CD-ROM drives or floppy drives. The loop devices
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are block special device files with major number 7 and typically
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called /dev/loop0, /dev/loop1 etc.
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This is useful if you want to check an ISO 9660 file system before
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burning the CD, or if you want to use floppy images without first
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writing them to floppy. Furthermore, some Linux distributions avoid
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the need for a dedicated Linux partition by keeping their complete
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root file system inside a DOS FAT file using this loop device
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driver.
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To use the loop device, you need the losetup utility, found in the
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util-linux package, see
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<https://www.kernel.org/pub/linux/utils/util-linux/>.
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The loop device driver can also be used to "hide" a file system in
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a disk partition, floppy, or regular file, either using encryption
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(scrambling the data) or steganography (hiding the data in the low
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bits of, say, a sound file). This is also safe if the file resides
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on a remote file server.
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Note that this loop device has nothing to do with the loopback
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device used for network connections from the machine to itself.
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To compile this driver as a module, choose M here: the
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module will be called loop.
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Most users will answer N here.
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config BLK_DEV_LOOP_MIN_COUNT
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int "Number of loop devices to pre-create at init time"
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depends on BLK_DEV_LOOP
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default 8
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help
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Static number of loop devices to be unconditionally pre-created
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at init time.
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This default value can be overwritten on the kernel command
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line or with module-parameter loop.max_loop.
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The historic default is 8. If a late 2011 version of losetup(8)
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is used, it can be set to 0, since needed loop devices can be
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dynamically allocated with the /dev/loop-control interface.
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source "drivers/block/drbd/Kconfig"
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config BLK_DEV_NBD
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tristate "Network block device support"
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depends on NET
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help
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Saying Y here will allow your computer to be a client for network
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block devices, i.e. it will be able to use block devices exported by
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servers (mount file systems on them etc.). Communication between
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client and server works over TCP/IP networking, but to the client
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program this is hidden: it looks like a regular local file access to
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a block device special file such as /dev/nd0.
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Network block devices also allows you to run a block-device in
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userland (making server and client physically the same computer,
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communicating using the loopback network device).
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Read <file:Documentation/admin-guide/blockdev/nbd.rst> for more information,
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especially about where to find the server code, which runs in user
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space and does not need special kernel support.
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Note that this has nothing to do with the network file systems NFS
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or Coda; you can say N here even if you intend to use NFS or Coda.
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To compile this driver as a module, choose M here: the
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module will be called nbd.
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If unsure, say N.
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config BLK_DEV_SX8
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tristate "Promise SATA SX8 support"
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depends on PCI
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help
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Saying Y or M here will enable support for the
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Promise SATA SX8 controllers.
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Use devices /dev/sx8/$N and /dev/sx8/$Np$M.
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config BLK_DEV_RAM
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tristate "RAM block device support"
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help
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Saying Y here will allow you to use a portion of your RAM memory as
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a block device, so that you can make file systems on it, read and
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write to it and do all the other things that you can do with normal
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block devices (such as hard drives). It is usually used to load and
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store a copy of a minimal root file system off of a floppy into RAM
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during the initial install of Linux.
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Note that the kernel command line option "ramdisk=XX" is now obsolete.
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For details, read <file:Documentation/admin-guide/blockdev/ramdisk.rst>.
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To compile this driver as a module, choose M here: the
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module will be called brd. An alias "rd" has been defined
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for historical reasons.
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Most normal users won't need the RAM disk functionality, and can
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thus say N here.
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config BLK_DEV_RAM_COUNT
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int "Default number of RAM disks"
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default "16"
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depends on BLK_DEV_RAM
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help
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The default value is 16 RAM disks. Change this if you know what you
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are doing. If you boot from a filesystem that needs to be extracted
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in memory, you will need at least one RAM disk (e.g. root on cramfs).
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config BLK_DEV_RAM_SIZE
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int "Default RAM disk size (kbytes)"
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depends on BLK_DEV_RAM
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default "4096"
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help
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The default value is 4096 kilobytes. Only change this if you know
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what you are doing.
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config CDROM_PKTCDVD
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tristate "Packet writing on CD/DVD media (DEPRECATED)"
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depends on !UML
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depends on SCSI
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select CDROM
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help
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Note: This driver is deprecated and will be removed from the
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kernel in the near future!
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If you have a CDROM/DVD drive that supports packet writing, say
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Y to include support. It should work with any MMC/Mt Fuji
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compliant ATAPI or SCSI drive, which is just about any newer
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DVD/CD writer.
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Currently only writing to CD-RW, DVD-RW, DVD+RW and DVDRAM discs
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is possible.
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DVD-RW disks must be in restricted overwrite mode.
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See the file <file:Documentation/cdrom/packet-writing.rst>
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for further information on the use of this driver.
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To compile this driver as a module, choose M here: the
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module will be called pktcdvd.
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config CDROM_PKTCDVD_BUFFERS
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int "Free buffers for data gathering"
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depends on CDROM_PKTCDVD
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default "8"
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help
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This controls the maximum number of active concurrent packets. More
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concurrent packets can increase write performance, but also require
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more memory. Each concurrent packet will require approximately 64Kb
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of non-swappable kernel memory, memory which will be allocated when
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a disc is opened for writing.
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config CDROM_PKTCDVD_WCACHE
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bool "Enable write caching"
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depends on CDROM_PKTCDVD
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help
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If enabled, write caching will be set for the CD-R/W device. For now
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this option is dangerous unless the CD-RW media is known good, as we
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don't do deferred write error handling yet.
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config ATA_OVER_ETH
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tristate "ATA over Ethernet support"
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depends on NET
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help
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This driver provides Support for ATA over Ethernet block
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devices like the Coraid EtherDrive (R) Storage Blade.
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config SUNVDC
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tristate "Sun Virtual Disk Client support"
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depends on SUN_LDOMS
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help
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Support for virtual disk devices as a client under Sun
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Logical Domains.
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source "drivers/s390/block/Kconfig"
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config XEN_BLKDEV_FRONTEND
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tristate "Xen virtual block device support"
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depends on XEN
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default y
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select XEN_XENBUS_FRONTEND
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help
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This driver implements the front-end of the Xen virtual
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block device driver. It communicates with a back-end driver
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in another domain which drives the actual block device.
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config XEN_BLKDEV_BACKEND
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tristate "Xen block-device backend driver"
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depends on XEN_BACKEND
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help
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The block-device backend driver allows the kernel to export its
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block devices to other guests via a high-performance shared-memory
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interface.
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The corresponding Linux frontend driver is enabled by the
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CONFIG_XEN_BLKDEV_FRONTEND configuration option.
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The backend driver attaches itself to a any block device specified
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in the XenBus configuration. There are no limits to what the block
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device as long as it has a major and minor.
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If you are compiling a kernel to run in a Xen block backend driver
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domain (often this is domain 0) you should say Y here. To
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compile this driver as a module, chose M here: the module
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will be called xen-blkback.
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config VIRTIO_BLK
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tristate "Virtio block driver"
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depends on VIRTIO
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select SG_POOL
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help
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This is the virtual block driver for virtio. It can be used with
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QEMU based VMMs (like KVM or Xen). Say Y or M.
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config BLK_DEV_RBD
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tristate "Rados block device (RBD)"
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depends on INET && BLOCK
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select CEPH_LIB
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select LIBCRC32C
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select CRYPTO_AES
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select CRYPTO
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help
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Say Y here if you want include the Rados block device, which stripes
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a block device over objects stored in the Ceph distributed object
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store.
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More information at http://ceph.newdream.net/.
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If unsure, say N.
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config BLK_DEV_UBLK
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tristate "Userspace block driver (Experimental)"
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select IO_URING
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help
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io_uring based userspace block driver. Together with ublk server, ublk
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has been working well, but interface with userspace or command data
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definition isn't finalized yet, and might change according to future
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requirement, so mark is as experimental now.
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source "drivers/block/rnbd/Kconfig"
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endif # BLK_DEV
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