Re: [PATCH v6 02/16] chardev: introduce cdev_get_by_path()

Sagi Grimberg
2019-07-26T04:29:45Z

>>>>>>> NVMe-OF is configured using configfs. The target is specified by the
>>>>>>> user writing a path to a configfs attribute. This is the way it works
>>>>>>> today but with blkdev_get_by_path()[1]. For the passthru code, we need
>>>>>>> to get a nvme_ctrl instead of a block_device, but the principal is the same.
>>>>>>
>>>>>> Why isn't a fd being passed in there instead of a random string?
>>>>>
>>>>> I suppose we could echo a string of the file descriptor number there,
>>>>> and look up the fd in the process' file descriptor table ...
>>>>
>>>> Assuming that there is a open handle somewhere out there...
>>
>> Yes, that would be a step backwards from an interface. The user would
>> then need a special process to open the fd and pass it through configfs.
>> They couldn't just do it with basic bash commands.
>
> First of all, they can, but... WTF not have filp_open() done right there?
> Yes, by name. With permission checks done. And pick your object from the
> sodding struct file you'll get.
>
> What's the problem? Why do you need cdev lookups, etc., when you are
> dealing with files under your full control? Just open them and use
> ->private_data or whatever you set in ->open() to access the damn thing.
> All there is to it...
Oh this is so much simpler. There is really no point in using anything
else. Just need to remember to compare f->f_op to what we expect to make
sure that it is indeed the same device class.