Re: [RFC PATCH 1/5] rust: block: introduce `kernel::block::mq` module

[Andreas Hindborg]

Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx> writes:

> On Thu, Mar 14, 2024 at 9:58 AM Andreas Hindborg <nmi@xxxxxxxxxxxx> wrote:
>>
>> Yes, good point. Another option suggested by Miguel is that
>> `__blk_mq_free_request` need not be exported at all. We can make it
>> non-static and then call it from
>> `rust_helper_blk_mq_free_request_internal()`. Then only the latter will
>> be in the kernel image symbol table, which might be better in terms of
>> not exposing `__blk_mq_free_request()` directly.
>
> The helper is not needed, i.e. what I meant was to make it non-static
> and add it to `include/linux/blk-mq.h`.

The way the current code compiles, <kernel::block::mq::Request as
kernel::types::AlwaysRefCounted>::dec_ref` is inlined into the `rnull`
module. A relocation for `rust_helper_blk_mq_free_request_internal`
appears in `rnull_mod.ko`. I didn't test it yet, but if
`__blk_mq_free_request` (or the helper) is not exported, I don't think
this would be possible?

BR Andreas