Re: [PATCH v2 5/5] fuse: introduce inode io modes

[Miklos Szeredi <miklos@szeredi.hu>]

On Tue, 6 Feb 2024 at 13:39, Amir Goldstein <amir73il@gmail.com> wrote:

> I have played with this rebranding of
> FOPEN_CACHE_IO => FOPEN_NO_PARALLEL_DIO_WRITES
>
> The meaning of the rebranded flag is:
> Prevent parallel dio on inode for as long as this file is kept open.
>
> The io modes code sets this flag implicitly on the first shared mmap.
>
> Let me know if this makes the external flag easier to swallow.
> Of course I can make this flag internal and not and FOPEN_ flag
> at all, but IMO, the code is easier to understand when the type of
> iocachectl refcount held by any file is specified by its FOPEN_ flags.

If there's no clear use case that would benefit from having this flag
on the userspace interface, then I'd recommend not to export it for
now.

I understand the need for clarifying the various states that the
kernel can be, but I think that's a bigger project involving e.g. data
and metadata cache validity, where the current rules are pretty
convoluted.

So for now I'd just stick with the implicit state change by mmap.

BTW, I started looking at the fuse-backing-fd branch and really hope
we can get this into shape for the next merge window.

Thanks,
Miklos