Block-Level Data Management System

This specification is related to a Linux device driver implementing block-level maintenance of user data, in particular of user messages.

How to build

Binary build with debug informations and page cache write-back policy:

make -C kernelspace debug

Binary build with debug informations and page cache write-through policy:

make -C kernelspace debug-wt

Build test driver:

make -C userspace ./bin/test

To change test to launch, edit userspace/test/test_main.c

Usage

Once built, the module can be loaded using ìnsmod. Default values for module params are included in module source.

To load the module with default param values:

make -C kernelspace load

After loading the module, assuming default values for module params, a new block device will appear at /dev/bldmsdisk. Users can format and mount such device with bldms using the functions declared in userspace/logic/devkeeper/devkeeper.h.

Note that there is no strict need to use such device as the bldms support. Users can use whatever device they want, even a regular file, given that it is correctly formatted using the devkeeper.

Users are expected to build their clients using apis declared in userspace/logic/api/api.h if they want to access vfs unsupported operations.

Kernelspace design

The design boils down to the interaction between two main components:

• ops: implements interactions from userspace to the bldms system. It stems in additional two sub-components:
  • ops/vfs_unsupported: Implements the vfs-unsupported operations of put_data(), get_data() and invalidate_data() as system calls;
  • ops/vfs_supported: Implement a custom implementation of vfs read().
• block_layer: Provides a block-view of the underlying device, along with methods to interact with it while keeping consistent among concurrent usages;

The following components help the previous ones to do their job:

• usctm: provides facilities to register new syscalls in free entries of the syscall table;
• singlefilefs: provides a file system used to mount bldms and interact with it using vfs-supported ops (such as read())

Additionally, the device component implements a block device that users can use as the underlying device of bldms.

System-wide configuration params and module params default values can be found in config.h. Components can define additional configs in their corresponding sources.

Further implementation details can be found in comments in source files.