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Writing to mounted devices is dangerous and can lead to filesystem corruption as well as crashes. Furthermore syzbot comes with more and more involved examples how to corrupt block device under a mounted filesystem leading to kernel crashes and reports we can do nothing about. Add tracking of writers to each block device and a kernel cmdline argument which controls whether other writeable opens to block devices open with BLK_OPEN_RESTRICT_WRITES flag are allowed. We will make filesystems use this flag for used devices. Note that this effectively only prevents modification of the particular block device's page cache by other writers. The actual device content can still be modified by other means - e.g. by issuing direct scsi commands, by doing writes through devices lower in the storage stack (e.g. in case loop devices, DM, or MD are involved) etc. But blocking direct modifications of the block device page cache is enough to give filesystems a chance to perform data validation when loading data from the underlying storage and thus prevent kernel crashes. Syzbot can use this cmdline argument option to avoid uninteresting crashes. Also users whose userspace setup does not need writing to mounted block devices can set this option for hardening. Link: https://lore.kernel.org/all/60788e5d-5c7c-1142-e554-c21d709acfd9@linaro.org Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20231101174325.10596-3-jack@suse.cz Reviewed-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Christian Brauner <brauner@kernel.org>
255 lines
8.0 KiB
Plaintext
255 lines
8.0 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0
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#
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# Block layer core configuration
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#
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menuconfig BLOCK
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bool "Enable the block layer" if EXPERT
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default y
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select FS_IOMAP
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select SBITMAP
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help
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Provide block layer support for the kernel.
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Disable this option to remove the block layer support from the
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kernel. This may be useful for embedded devices.
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If this option is disabled:
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- block device files will become unusable
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- some filesystems (such as ext3) will become unavailable.
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Also, SCSI character devices and USB storage will be disabled since
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they make use of various block layer definitions and facilities.
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Say Y here unless you know you really don't want to mount disks and
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suchlike.
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if BLOCK
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config BLOCK_LEGACY_AUTOLOAD
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bool "Legacy autoloading support"
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default y
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help
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Enable loading modules and creating block device instances based on
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accesses through their device special file. This is a historic Linux
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feature and makes no sense in a udev world where device files are
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created on demand, but scripts that manually create device nodes and
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then call losetup might rely on this behavior.
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config BLK_RQ_ALLOC_TIME
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bool
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config BLK_CGROUP_RWSTAT
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bool
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config BLK_CGROUP_PUNT_BIO
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bool
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config BLK_DEV_BSG_COMMON
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tristate
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config BLK_ICQ
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bool
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config BLK_DEV_BSGLIB
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bool "Block layer SG support v4 helper lib"
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select BLK_DEV_BSG_COMMON
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help
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Subsystems will normally enable this if needed. Users will not
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normally need to manually enable this.
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If unsure, say N.
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config BLK_DEV_INTEGRITY
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bool "Block layer data integrity support"
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help
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Some storage devices allow extra information to be
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stored/retrieved to help protect the data. The block layer
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data integrity option provides hooks which can be used by
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filesystems to ensure better data integrity.
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Say yes here if you have a storage device that provides the
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T10/SCSI Data Integrity Field or the T13/ATA External Path
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Protection. If in doubt, say N.
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config BLK_DEV_INTEGRITY_T10
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tristate
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depends on BLK_DEV_INTEGRITY
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select CRC_T10DIF
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select CRC64_ROCKSOFT
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config BLK_DEV_WRITE_MOUNTED
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bool "Allow writing to mounted block devices"
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default y
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help
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When a block device is mounted, writing to its buffer cache is very
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likely going to cause filesystem corruption. It is also rather easy to
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crash the kernel in this way since the filesystem has no practical way
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of detecting these writes to buffer cache and verifying its metadata
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integrity. However there are some setups that need this capability
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like running fsck on read-only mounted root device, modifying some
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features on mounted ext4 filesystem, and similar. If you say N, the
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kernel will prevent processes from writing to block devices that are
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mounted by filesystems which provides some more protection from runaway
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privileged processes and generally makes it much harder to crash
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filesystem drivers. Note however that this does not prevent
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underlying device(s) from being modified by other means, e.g. by
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directly submitting SCSI commands or through access to lower layers of
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storage stack. If in doubt, say Y. The configuration can be overridden
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with the bdev_allow_write_mounted boot option.
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config BLK_DEV_ZONED
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bool "Zoned block device support"
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select MQ_IOSCHED_DEADLINE
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help
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Block layer zoned block device support. This option enables
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support for ZAC/ZBC/ZNS host-managed and host-aware zoned block
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devices.
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Say yes here if you have a ZAC, ZBC, or ZNS storage device.
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config BLK_DEV_THROTTLING
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bool "Block layer bio throttling support"
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depends on BLK_CGROUP
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select BLK_CGROUP_RWSTAT
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help
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Block layer bio throttling support. It can be used to limit
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the IO rate to a device. IO rate policies are per cgroup and
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one needs to mount and use blkio cgroup controller for creating
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cgroups and specifying per device IO rate policies.
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See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
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config BLK_DEV_THROTTLING_LOW
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bool "Block throttling .low limit interface support (EXPERIMENTAL)"
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depends on BLK_DEV_THROTTLING
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help
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Add .low limit interface for block throttling. The low limit is a best
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effort limit to prioritize cgroups. Depending on the setting, the limit
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can be used to protect cgroups in terms of bandwidth/iops and better
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utilize disk resource.
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Note, this is an experimental interface and could be changed someday.
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config BLK_WBT
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bool "Enable support for block device writeback throttling"
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help
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Enabling this option enables the block layer to throttle buffered
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background writeback from the VM, making it more smooth and having
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less impact on foreground operations. The throttling is done
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dynamically on an algorithm loosely based on CoDel, factoring in
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the realtime performance of the disk.
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config BLK_WBT_MQ
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bool "Enable writeback throttling by default"
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default y
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depends on BLK_WBT
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help
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Enable writeback throttling by default for request-based block devices.
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config BLK_CGROUP_IOLATENCY
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bool "Enable support for latency based cgroup IO protection"
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depends on BLK_CGROUP
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help
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Enabling this option enables the .latency interface for IO throttling.
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The IO controller will attempt to maintain average IO latencies below
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the configured latency target, throttling anybody with a higher latency
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target than the victimized group.
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Note, this is an experimental interface and could be changed someday.
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config BLK_CGROUP_FC_APPID
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bool "Enable support to track FC I/O Traffic across cgroup applications"
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depends on BLK_CGROUP && NVME_FC
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help
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Enabling this option enables the support to track FC I/O traffic across
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cgroup applications. It enables the Fabric and the storage targets to
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identify, monitor, and handle FC traffic based on VM tags by inserting
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application specific identification into the FC frame.
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config BLK_CGROUP_IOCOST
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bool "Enable support for cost model based cgroup IO controller"
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depends on BLK_CGROUP
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select BLK_RQ_ALLOC_TIME
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help
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Enabling this option enables the .weight interface for cost
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model based proportional IO control. The IO controller
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distributes IO capacity between different groups based on
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their share of the overall weight distribution.
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config BLK_CGROUP_IOPRIO
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bool "Cgroup I/O controller for assigning an I/O priority class"
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depends on BLK_CGROUP
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help
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Enable the .prio interface for assigning an I/O priority class to
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requests. The I/O priority class affects the order in which an I/O
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scheduler and block devices process requests. Only some I/O schedulers
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and some block devices support I/O priorities.
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config BLK_DEBUG_FS
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bool "Block layer debugging information in debugfs"
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default y
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depends on DEBUG_FS
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help
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Include block layer debugging information in debugfs. This information
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is mostly useful for kernel developers, but it doesn't incur any cost
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at runtime.
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Unless you are building a kernel for a tiny system, you should
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say Y here.
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config BLK_DEBUG_FS_ZONED
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bool
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default BLK_DEBUG_FS && BLK_DEV_ZONED
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config BLK_SED_OPAL
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bool "Logic for interfacing with Opal enabled SEDs"
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depends on KEYS
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select PSERIES_PLPKS if PPC_PSERIES
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select PSERIES_PLPKS_SED if PPC_PSERIES
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help
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Builds Logic for interfacing with Opal enabled controllers.
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Enabling this option enables users to setup/unlock/lock
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Locking ranges for SED devices using the Opal protocol.
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config BLK_INLINE_ENCRYPTION
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bool "Enable inline encryption support in block layer"
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help
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Build the blk-crypto subsystem. Enabling this lets the
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block layer handle encryption, so users can take
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advantage of inline encryption hardware if present.
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config BLK_INLINE_ENCRYPTION_FALLBACK
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bool "Enable crypto API fallback for blk-crypto"
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depends on BLK_INLINE_ENCRYPTION
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select CRYPTO
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select CRYPTO_SKCIPHER
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help
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Enabling this lets the block layer handle inline encryption
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by falling back to the kernel crypto API when inline
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encryption hardware is not present.
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source "block/partitions/Kconfig"
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config BLK_MQ_PCI
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def_bool PCI
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config BLK_MQ_VIRTIO
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bool
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depends on VIRTIO
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default y
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config BLK_PM
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def_bool PM
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# do not use in new code
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config BLOCK_HOLDER_DEPRECATED
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bool
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config BLK_MQ_STACKING
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bool
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source "block/Kconfig.iosched"
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endif # BLOCK
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