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Based on https://www.redhat.com/archives/dm-devel/2019-March/msg00025.html Third version of dm-bow. Key changes: Free list added Support for block sizes other than 4k Handles writes during trim phase, and overlapping trims Integer overflow error Support trims even if underlying device doesn't Numerous small bug fixes bow == backup on write USE CASE: dm-bow takes a snapshot of an existing file system before mounting. The user may, before removing the device, commit the snapshot. Alternatively the user may remove the device and then run a command line utility to restore the device to its original state. dm-bow does not require an external device dm-bow efficiently uses all the available free space on the file system. IMPLEMENTATION: dm-bow can be in one of three states. In state one, the free blocks on the device are identified by issuing an FSTRIM to the filesystem. In state two, any writes cause the overwritten data to be backup up to the available free space. While in this state, the device can be restored by unmounting the filesystem, removing the dm-bow device and running a usermode tool over the underlying device. In state three, the changes are committed, dm-bow is in pass-through mode and the drive can no longer be restored. It is planned to use this driver to enable restoration of a failed update attempt on Android devices using ext4. Test: Can boot Android with userdata mounted on this device. Can commit userdata after SUW has run. Can then reboot, make changes and roll back. Known issues: Mutex is held around entire flush operation, including lengthy I/O. Plan is to convert to state machine with pending queues. Interaction with block encryption is unknown, especially with respect to sector 0. Bug: 119769411 Bug: 129280212 Test: Dogfooded on Wahoo. Ran under Cuttlefish, running VtsKernelBowTest & VtsKernelCheckpointTest tests against 4.19, 4.14 & 4.9 kernels Change-Id: Id70988bbd797ebe3e76fc175094388b423c8da8c Signed-off-by: Paul Lawrence <paullawrence@google.com> |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| build.config.cuttlefish.aarch64 | ||
| build.config.cuttlefish.x86_64 | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.