CODEWITHSUNDEEP
linux-device-driver
user5177344
user5177344

Reputation:

How to performs I/O to block device from block device driver under Linux

I have a task to write a block device driver (/dev/dua - for example) , this block device is must be looks like to OS as a disk device like /dev/sda. So, this driver must process data blocks and write it to other block device.

I looking for a right way to performs I/O operations on the backend device like "/dev/sdb".

I have played with the vfs_read/write routines it's works at glance for disk sector sized transfers. But, probably there is more effective way to performs I/O on backend device ?

TIA.

Upvotes: 0

Views: 216

Answers (1)

user5177344
user5177344

Reputation:

Follows a piece of code (original has been found here : https://github.com/asimkadav/block-filter) implements a "filtering" feature, so it can be used as a method to performs I/O on a backend block device `

void misc_request_fn(struct request_queue *q, struct bio *bio) {
        printk ("we are passing bios.\n");
        // here is where we trace requests...
        original_request_fn (q, bio);
        return;
}


void register_block_device(char *path)  {

        struct request_queue *blkdev_queue = NULL;

        if (path == NULL)       {
                printk ("Block device empty.\n");
                return;
        }

        printk ("Will open %s.\n", path);

        blkdev = lookup_bdev(path);

        if (IS_ERR(blkdev))     {
                printk ("No such block device.\n");
                return;
        }

        printk ("Found block device %p with bs %d.\n", blkdev, blkdev->bd_block_size);
        blkdev_queue = bdev_get_queue(blkdev);
        original_request_fn = blkdev_queue->request_fn;
        blkdev_queue->request_fn = misc_request_fn;
}

`

Upvotes: 1

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