[PATCH 00/20] blksnap - creating non-persistent snapshots for backup

Sergei Shtepa
2022-06-13T18:55:50Z

Hi all.

I suggest the blksnap kernel module for consideration. It allows to create
non-persistent snapshots of any block devices. The main purpose of such
snapshots is to create a backup of block devices.

A snapshot is created simultaneously for several block devices, ensuring
their mutual consistency in the backup.

A change tracker is implemented in the module. It allows to determine
which blocks were changed during the time between the last snapshot
created and any of the previous snapshots of the same generation.
This allows to implement incremental and differential backups.

An arbitrary range of sectors on any block device can be used to store
snapshot changes. The size of the storage for changes can be increased after the
snapshot is created by adding new sector ranges. This allows to create a
storage of differences in individual files on a file system that can occupy
the entire space of a block device and increase the storage of differences
as needed.

To create images of snapshots of block devices, the module stores blocks
of the original block device that have been changed since the snapshot was
taken. To do this, the module intercepts write requests and reads blocks
that need to be overwritten. This algorithm guarantees the safety of the
data of the original block device in case of overflow of the snapshot and
even in case of unpredictable critical errors.

To connect and disconnect the module to the block layer, the concept of a
block device filter is introduced. Functions for connecting filters are
added to the block layer and the ability to intercept I/O requests is
provided.

The blksnap module was created specifically for upstream based on the
experience of operating the out-of-tree veeamsnap module, which is part of
the Veeam Agent for Linux product. I am sure that the module will be in
demand by other creators of backup tools and will save them from having to
use their out-of-tree kernel modules.

A tool, a library for working with blksnap, tests and some documentations
can be found at www.github.com/veeam/blksnap.

Sergei Shtepa (20):
block, blk_filter: enable block device filters
block, blksnap: header file of the module interface
block, blksnap: module management interface functions
block, blksnap: init() and exit() functions
block, blksnap: interaction with sysfs
block, blksnap: attaching and detaching the filter and handling a bios
block, blksnap: map of change block tracking
block, blksnap: big buffer in the form of an array of pages
block, blksnap: minimum data storage unit of the original block device
block, blksnap: buffer in memory for the minimum data storage unit
block, blksnap: functions and structures for performing block I/O
operations
block, blksnap: storage for storing difference blocks
block, blksnap: event queue from the difference storage
block, blksnap: owner of information about overwritten blocks of the
original block device
block, blksnap: snapshot image block device
block, blksnap: snapshot
block, blksnap: debugging mechanism for monitoring memory consumption
block, blksnap: Kconfig
block, blksnap: Makefile
block, blksnap: adds a blksnap to the kernel tree

block/Kconfig | 8 +
block/bdev.c | 129 +++++
block/blk-core.c | 88 ++++
drivers/block/Kconfig | 2 +
drivers/block/Makefile | 1 +
drivers/block/blksnap/Kconfig | 101 ++++
drivers/block/blksnap/Makefile | 20 +
drivers/block/blksnap/big_buffer.c | 218 ++++++++
drivers/block/blksnap/big_buffer.h | 27 +
drivers/block/blksnap/cbt_map.c | 280 ++++++++++
drivers/block/blksnap/cbt_map.h | 112 ++++
drivers/block/blksnap/chunk.c | 352 +++++++++++++
drivers/block/blksnap/chunk.h | 129 +++++
drivers/block/blksnap/ctrl.c | 445 ++++++++++++++++
drivers/block/blksnap/ctrl.h | 7 +
drivers/block/blksnap/diff_area.c | 602 +++++++++++++++++++++
drivers/block/blksnap/diff_area.h | 179 +++++++
drivers/block/blksnap/diff_buffer.c | 146 ++++++
drivers/block/blksnap/diff_buffer.h | 78 +++
drivers/block/blksnap/diff_io.c | 204 ++++++++
drivers/block/blksnap/diff_io.h | 122 +++++
drivers/block/blksnap/diff_storage.c | 316 +++++++++++
drivers/block/blksnap/diff_storage.h | 94 ++++
drivers/block/blksnap/event_queue.c | 90 ++++
drivers/block/blksnap/event_queue.h | 64 +++
drivers/block/blksnap/main.c | 109 ++++
drivers/block/blksnap/memory_checker.c | 100 ++++
drivers/block/blksnap/memory_checker.h | 41 ++
drivers/block/blksnap/params.h | 10 +
drivers/block/blksnap/snapimage.c | 345 ++++++++++++
drivers/block/blksnap/snapimage.h | 65 +++
drivers/block/blksnap/snapshot.c | 671 ++++++++++++++++++++++++
drivers/block/blksnap/snapshot.h | 76 +++
drivers/block/blksnap/sysfs.c | 81 +++
drivers/block/blksnap/sysfs.h | 5 +
drivers/block/blksnap/tracker.c | 693 +++++++++++++++++++++++++
drivers/block/blksnap/tracker.h | 71 +++
drivers/block/blksnap/version.h | 8 +
include/linux/blk_snap.h | 460 ++++++++++++++++
include/linux/blk_types.h | 22 +
include/linux/blkdev.h | 81 +++
41 files changed, 6652 insertions(+)
create mode 100644 drivers/block/blksnap/Kconfig
create mode 100644 drivers/block/blksnap/Makefile
create mode 100644 drivers/block/blksnap/big_buffer.c
create mode 100644 drivers/block/blksnap/big_buffer.h
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/ctrl.c
create mode 100644 drivers/block/blksnap/ctrl.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_io.c
create mode 100644 drivers/block/blksnap/diff_io.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/memory_checker.c
create mode 100644 drivers/block/blksnap/memory_checker.h
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/sysfs.c
create mode 100644 drivers/block/blksnap/sysfs.h
create mode 100644 drivers/block/blksnap/tracker.c
create mode 100644 drivers/block/blksnap/tracker.h
create mode 100644 drivers/block/blksnap/version.h
create mode 100644 include/linux/blk_snap.h

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2.20.1