Smart Block Device Driver

This repository contains a Linux kernel block device driver implementing a priority-aware, cached write-back strategy. The driver is designed for flexibility, efficiency, and real-time introspection via the procfs interface.

Features

• Priority-Aware Asynchronous Writes Write requests are buffered and ordered by process priority, ensuring higher-priority operations are serviced first.

• In-Memory Write Caching Requests are cached in memory to minimize direct disk writes and optimize I/O performance.

• Process-Specific Cache Flush Supports flushing of write requests associated with a specific process using the procfs interface.

• Dynamic Cache Resizing Cache size can be adjusted at runtime via procfs.

• Statistics and Monitoring Real-time statistics and cache contents are accessible via /proc/smart_block/.

Build and Installation

Build the Module

make

Load the Module

sudo insmod smart_block.ko cache_size=131072

This loads the block device driver with a 128KB cache (default is 64KB).

Create a Device Node

sudo mknod /dev/smart_block b <major_number> 0

Replace <major_number> with the actual major number printed in dmesg.

Unload the Module

sudo rmmod smart_block

Procfs Interface

The driver exposes a procfs directory at /proc/smart_block/ with the following entries:

File	Description
stats	Displays cached bytes and total flushes to disk
flush	Accepts a PID to flush that process's write requests
resize_cache	Accepts a new cache size (in bytes)
cache	Displays a list of all pending write requests with metadata

Examples

Flush cache for PID 1234:

echo 1234 | sudo tee /proc/smart_block/flush

Resize cache to 256KB:

echo 262144 | sudo tee /proc/smart_block/resize_cache

Check statistics:

cat /proc/smart_block/stats

Design Highlights

• Write requests are maintained in a linked list, sorted by process priority.
• Flush operations can be triggered automatically (e.g., cache overflow) or manually (via procfs).
• Spinlocks are used to ensure thread-safe cache access.
• blk-mq is used for scalable request queuing and dispatching.

Testing

A test suite is included to verify:

• Write ordering by priority
• Cache resizing behavior
• Process-aware flush correctness
• Proper statistics reporting

License

This project is licensed under the GPL-2.0 License.

Author

Anubhav Pandey