Re: [PATCH 1/7] rust: file: add Rust abstraction for `struct file`

[Theodore Ts'o]

On Fri, Dec 01, 2023 at 12:27:40PM +0000, Alice Ryhl wrote:
> 
> You can import it with a use statement. For example:
> 
> use kernel::file::flags::O_RDONLY;
> // use as O_RDONLY

That's good to hear, but it still means that we have to use the XYZ_*
prefix, because otherwise, after something like

use kernel::file::flags::RDONLY;
use kernel::uapi::rwf::RDONLY;

that will blow up.  So that has to be

use kernel::file::flags::O_RDONLY;
use kernel::uapi::rwf::RWF_RDONLY;

Which is a bit more verbose, at least things won't blow up
spectacularly when you need to use both namespaces in the same
codepath.

Also note how we do things like this:

#define IOCB_APPEND          (__force int) RWF_APPEND

In other words, the IOCB_* namespace and the RWF_* namespace partially
share code points, and so they *have* to be assigned to the same value
--- and note that since RWF_APPEND is defined as part of the UAPI, it
might not even be the same across different architectures....

Cheers,

						- Ted