Re: [PATCH 6/8] block: add example ioctl

[Pavel Begunkov <asml.silence@gmail.com>]

On 18/03/2021 05:45, Christoph Hellwig wrote:
> On Wed, Mar 17, 2021 at 04:10:25PM -0600, Jens Axboe wrote:
>> +static int blkdev_uring_ioctl(struct block_device *bdev,
>> +			      struct io_uring_cmd *cmd)
>> +{
>> +	struct block_uring_cmd *bcmd = (struct block_uring_cmd *) &cmd->pdu;
>> +
>> +	switch (bcmd->ioctl_cmd) {
>> +	case BLKBSZGET:
>> +		return block_size(bdev);
>> +	default:
>> +		return -ENOTTY;
>> +	}
>> +}
>> +
>>  static int blkdev_uring_cmd(struct io_uring_cmd *cmd,
>>  			    enum io_uring_cmd_flags flags)
>>  {
>>  	struct block_device *bdev = I_BDEV(cmd->file->f_mapping->host);
>>  
>> +	switch (cmd->op) {
>> +	case BLOCK_URING_OP_IOCTL:
>> +		return blkdev_uring_ioctl(bdev, cmd);
> 
> I don't think the two level dispatch here makes any sense.  Then again

At least it's in my plans to rework it a bit to resolve callbacks in
advance and get rid of double dispatching (for some cases). Like

struct io_cmd {
	void (*cb)(...);
	...
};

struct file_operations {
	struct io_cmd *get_cmd(...);
};

// registration
ctx->cmds[i] = file->get_cmd(...);

And first we do registration, and then use it

> I don't think this code makes sense either except as an example..

-- 
Pavel Begunkov