Re: [fuse-devel] [PATCH 0/8] MUSE: Userspace backed MTD v3

Luca Risolia
2021-02-09T15:11:28Z

Hi guys,

a bit OT probably: is there any chance for you to also implement mmap()
for CUSE? That would be much appreciated.

Thanks

On 09/02/21 15:35, Richard Weinberger wrote:
> Miklos,
>
> ----- Ursprüngliche Mail -----
>>> The core goal of MUSE is having the complexity on the userspace side and
>>> only a small MTD driver in kernelspace.
>>> While playing with different approaches I realized that FUSE offers everything
>>> we need. So MUSE is a little like CUSE except that it does not implement a
>>> bare character device but an MTD.
>>
>> Looks fine.
>
> I'm glad to hear that!
>
>> I do wonder if MUSE should go to drivers/mtd/ instead. Long term
>> goal would be move CUSE to drivers/char and move the transport part of
>> fuse into net/fuse leaving only the actual filesystems (fuse and
>> virtiofs) under fs/.
>>
>> But for now just moving the minimal interface needed for MUSE into a
>> separate header (<net/fuse.h>) would work, I guess.
>>
>> Do you think that would make sense?
>
> Yes, I'm all for having MUSE in drivers/mtd/.
>
> I placed MUSE initially in fs/fuse/ because CUSE was already there and muse.c includes
> fuse_i.h. So tried to be as little invasive as possible.
>
>>>
>>> Notes:
>>> ------
>>>
>>> - OOB support is currently limited. Currently MUSE has no support for processing
>>> in- and out-band in the same MTD operation. It is good enough to make JFFS2
>>> happy. This limitation is because FUSE has no support more than one variable
>>> length buffer in a FUSE request.
>>> At least I didn’t find a good way to pass more than one buffer to a request.
>>> Maybe FUSE folks can correct me. :-)
>>
>> If you look at fuse_do_ioctl() it does variable length input and
>> output at the same time. I guess you need something similar to that.
>
> I'll dig into this!
>
> Thanks,
> //richard