Re: [PATCH 2/3] rust: file: add f_pos and set_f_pos

[Al Viro]

On Thu, Sep 26, 2024 at 02:58:56PM +0000, Alice Ryhl wrote:
> Add accessors for the file position. Most of the time, you should not
> use these methods directly, and you should instead use a guard for the
> file position to prove that you hold the fpos lock. However, under
> limited circumstances, files are allowed to choose a different locking
> strategy for their file position. These accessors can be used to handle
> that case.
> 
> For now, these accessors are the only way to access the file position
> within the llseek and read_iter callbacks.

You really should not do that within ->read_iter().  If your method
does that, it has the wrong signature.

If nothing else, it should be usable for preadv(2), so what file position
are you talking about?