Hi all. I am happy to offer an improved version of the block device filtering mechanism (blkfilter) and module for creating snapshots of block devices (blksnap). The filtering block device mechanism is implemented in the block layer. This allows to attach and detach block device filters. Filters extend the functionality of the block layer. See more in Documentation/block/blkfilter.rst. The main purpose of snapshots of block devices is to provide backups of them. See more in Documentation/block/blksnap.rst. The tool, library and tests for working with blksnap can be found on github. Link: https://github.com/veeam/blksnap/tree/stable-v2.0 There is also documentation from which you can learn how to manage the module using the library and the console tool. Based on LK v6.8-rc3 with Christoph's patchset "clean up blk_mq_submit_bio". Link: https://lore.kernel.org/linux-block/50fbe76b-d77d-4a7e-bda4-3a3b754fbd7e@xxxxxxxxxx/T/#t I express my appreciation and gratitude to Christoph. Thanks to his attention to the project, it was possible to raise the quality of the code. I probably wouldn't have made version 7 if it wasn't for his help. I am sure that the blksnap module will improve the quality of backup tools for Linux. v7 changes: - The location of the filtering of I/O units has been changed. This made it possible to remove the additional call bio_queue_enter(). - Remove configs BLKSNAP_DIFF_BLKDEV and BLKSNAP_CHUNK_DIFF_BIO_SYNC. - To process the ioctl, the switch statement is used instead of a table with functions. - Instead of a file descriptor, the module gets a path on the file system. This allows the kernel module to correctly open a file or block device with exclusive access rights. - Fixed a bio leaking bugs. v6 changes: - The difference storage has been changed. In the previous version, the file was created only to reserve sector ranges on a block device. The data was stored directly to the block device in these sector ranges. Now saving and reading data is done using 'VFS' using vfs_iter_write() and vfs_iter_read() functions. This allows not to depend on the filesystem and use, for example, tmpfs. Using an unnamed temporary file allows hiding it from other processes and automatically release it when the snapshot is closed. However, now the module does not allow adding a block device to the snapshot on which the difference storage is located. There is no way to ensure the immutability of file metadata when writing data to a file. This means that the metadata of the filesystem may change, which may cause damage to the snapshot. - _IOW and _IOR were mixed up - fixed. - Protection against the use of the snapshots for block devices with hardware inline encryption and data integrity was implemented. Compatibility with them was not planned and has not been tested at the moment. v5 changes: - Rebase for "kernel/git/axboe/linux-block.git" branch "for-6.5/block". Link: https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/log/?h=for-6.5/block v4 changes: - Structures for describing the state of chunks are allocated dynamically. This reduces memory consumption, since the struct chunk is allocated only for those blocks for which the snapshot image state differs from the original block device. - The algorithm for calculating the chunk size depending on the size of the block device has been changed. For large block devices, it is now possible to allocate a larger number of chunks, and their size is smaller. - For block devices, a 'filter' file has been added to /sys/block/<device>. It displays the name of the filter that is attached to the block device. - Fixed a problem with the lack of protection against re-adding a block device to a snapshot. - Fixed a bug in the algorithm of allocating the next bio for a chunk. This problem was occurred on large disks, for which a chunk consists of at least two bio. - The ownership mechanism of the diff_area structure has been changed. This fixed the error of prematurely releasing the diff_area structure when destroying the snapshot. - Documentation corrected. - The Sparse analyzer is passed. - Use __u64 type instead pointers in UAPI. v3 changes: - New block device I/O controls BLKFILTER_ATTACH and BLKFILTER_DETACH allow to attach and detach filters. - New block device I/O control BLKFILTER_CTL allow sending command to attached block device filter. - The copy-on-write algorithm for processing I/O units has been optimized and has become asynchronous. - The snapshot image reading algorithm has been optimized and has become asynchronous. - Optimized the finite state machine for processing chunks. - Fixed a tracking block size calculation bug. v2 changes: - Added documentation for Block Device Filtering Mechanism. - Added documentation for Block Devices Snapshots Module (blksnap). - The MAINTAINERS file has been updated. - Optimized queue code for snapshot images. - Fixed comments, log messages and code for better readability. v1 changes: - Forgotten "static" declarations have been added. - The text of the comments has been corrected. - It is possible to connect only one filter, since there are no others in upstream. - Do not have additional locks for attach/detach filter. - blksnap.h moved to include/uapi/. - #pragma once and commented code removed. - uuid_t removed from user API. - Removed default values for module parameters from the configuration file. - The debugging code for tracking memory leaks has been removed. - Simplified Makefile. - Optimized work with large memory buffers, CBT tables are now in virtual memory. - The allocation code of minor numbers has been optimized. - The implementation of the snapshot image block device has been simplified, now it is a bio-based block device. - Removed initialization of global variables with null values. - only one bio is used to copy one chunk. - Checked on ppc64le. Sergei Shtepa (8): documentation: filtering and snapshots of a block devices block: filtering of a block devices block: header file of the blksnap module interface block: module management interface functions block: handling and tracking I/O units block: difference storage implementation block: snapshot and snapshot image block device block: Kconfig, Makefile and MAINTAINERS files Documentation/block/blkfilter.rst | 66 ++ Documentation/block/blksnap.rst | 351 ++++++++++ Documentation/block/index.rst | 2 + .../userspace-api/ioctl/ioctl-number.rst | 1 + MAINTAINERS | 17 + block/Makefile | 3 +- block/bdev.c | 2 + block/blk-core.c | 26 +- block/blk-filter.c | 257 +++++++ block/blk-mq.c | 7 +- block/blk-mq.h | 2 +- block/blk.h | 11 + block/genhd.c | 10 + block/ioctl.c | 7 + block/partitions/core.c | 9 + drivers/block/Kconfig | 2 + drivers/block/Makefile | 2 + drivers/block/blksnap/Kconfig | 12 + drivers/block/blksnap/Makefile | 15 + drivers/block/blksnap/cbt_map.c | 225 +++++++ drivers/block/blksnap/cbt_map.h | 90 +++ drivers/block/blksnap/chunk.c | 631 ++++++++++++++++++ drivers/block/blksnap/chunk.h | 134 ++++ drivers/block/blksnap/diff_area.c | 577 ++++++++++++++++ drivers/block/blksnap/diff_area.h | 175 +++++ drivers/block/blksnap/diff_buffer.c | 114 ++++ drivers/block/blksnap/diff_buffer.h | 37 + drivers/block/blksnap/diff_storage.c | 290 ++++++++ drivers/block/blksnap/diff_storage.h | 103 +++ drivers/block/blksnap/event_queue.c | 81 +++ drivers/block/blksnap/event_queue.h | 64 ++ drivers/block/blksnap/main.c | 481 +++++++++++++ drivers/block/blksnap/params.h | 16 + drivers/block/blksnap/snapimage.c | 135 ++++ drivers/block/blksnap/snapimage.h | 10 + drivers/block/blksnap/snapshot.c | 462 +++++++++++++ drivers/block/blksnap/snapshot.h | 65 ++ drivers/block/blksnap/tracker.c | 369 ++++++++++ drivers/block/blksnap/tracker.h | 78 +++ include/linux/blk-filter.h | 72 ++ include/linux/blk_types.h | 1 + include/linux/sched.h | 1 + include/uapi/linux/blk-filter.h | 35 + include/uapi/linux/blksnap.h | 384 +++++++++++ include/uapi/linux/fs.h | 3 + 45 files changed, 5430 insertions(+), 5 deletions(-) create mode 100644 Documentation/block/blkfilter.rst create mode 100644 Documentation/block/blksnap.rst create mode 100644 block/blk-filter.c create mode 100644 drivers/block/blksnap/Kconfig create mode 100644 drivers/block/blksnap/Makefile create mode 100644 drivers/block/blksnap/cbt_map.c create mode 100644 drivers/block/blksnap/cbt_map.h create mode 100644 drivers/block/blksnap/chunk.c create mode 100644 drivers/block/blksnap/chunk.h create mode 100644 drivers/block/blksnap/diff_area.c create mode 100644 drivers/block/blksnap/diff_area.h create mode 100644 drivers/block/blksnap/diff_buffer.c create mode 100644 drivers/block/blksnap/diff_buffer.h create mode 100644 drivers/block/blksnap/diff_storage.c create mode 100644 drivers/block/blksnap/diff_storage.h create mode 100644 drivers/block/blksnap/event_queue.c create mode 100644 drivers/block/blksnap/event_queue.h create mode 100644 drivers/block/blksnap/main.c create mode 100644 drivers/block/blksnap/params.h create mode 100644 drivers/block/blksnap/snapimage.c create mode 100644 drivers/block/blksnap/snapimage.h create mode 100644 drivers/block/blksnap/snapshot.c create mode 100644 drivers/block/blksnap/snapshot.h create mode 100644 drivers/block/blksnap/tracker.c create mode 100644 drivers/block/blksnap/tracker.h create mode 100644 include/linux/blk-filter.h create mode 100644 include/uapi/linux/blk-filter.h create mode 100644 include/uapi/linux/blksnap.h -- 2.34.1
