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

Andreas Hindborg
2024-03-14T08:58:31Z

Boqun Feng <boqun.feng@gmail.com> writes:

> On Wed, Mar 13, 2024 at 12:05:08PM +0100, Andreas Hindborg wrote:
>> From: Andreas Hindborg <a.hindborg@samsung.com>
>>
>> Add initial abstractions for working with blk-mq.
>>
>> This patch is a maintained, refactored subset of code originally published by
>> Wedson Almeida Filho <wedsonaf@gmail.com> [1].
>>
>> [1] https://github.com/wedsonaf/linux/tree/f2cfd2fe0e2ca4e90994f96afe268bbd4382a891/rust/kernel/blk/mq.rs
>>
>> Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
>> Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
>> ---
>> block/blk-mq.c | 3 +-
>> include/linux/blk-mq.h | 1 +
>> rust/bindings/bindings_helper.h | 2 +
>> rust/helpers.c | 45 ++++
>> rust/kernel/block.rs | 5 +
>> rust/kernel/block/mq.rs | 131 +++++++++++
>> rust/kernel/block/mq/gen_disk.rs | 174 +++++++++++++++
>> rust/kernel/block/mq/operations.rs | 346 +++++++++++++++++++++++++++++
>> rust/kernel/block/mq/raw_writer.rs | 60 +++++
>> rust/kernel/block/mq/request.rs | 182 +++++++++++++++
>> rust/kernel/block/mq/tag_set.rs | 117 ++++++++++
>> rust/kernel/error.rs | 5 +
>> rust/kernel/lib.rs | 1 +
>> 13 files changed, 1071 insertions(+), 1 deletion(-)
>> create mode 100644 rust/kernel/block.rs
>> create mode 100644 rust/kernel/block/mq.rs
>> create mode 100644 rust/kernel/block/mq/gen_disk.rs
>> create mode 100644 rust/kernel/block/mq/operations.rs
>> create mode 100644 rust/kernel/block/mq/raw_writer.rs
>> create mode 100644 rust/kernel/block/mq/request.rs
>> create mode 100644 rust/kernel/block/mq/tag_set.rs
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 2dc01551e27c..a531f664bee7 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -702,7 +702,7 @@ static void blk_mq_finish_request(struct request *rq)
>> }
>> }
>>
>> -static void __blk_mq_free_request(struct request *rq)
>> +void __blk_mq_free_request(struct request *rq)
>> {
>> struct request_queue *q = rq->q;
>> struct blk_mq_ctx *ctx = rq->mq_ctx;
>> @@ -722,6 +722,7 @@ static void __blk_mq_free_request(struct request *rq)
>> blk_mq_sched_restart(hctx);
>> blk_queue_exit(q);
>> }
>> +EXPORT_SYMBOL_GPL(__blk_mq_free_request);
>>
>
> Note that for an EXPORT_SYMBOL_GPL() symbol, you can just add the
> corresponding header file in rust/bindings/bindings_helper.h:
>
> +#include <linux/blk-mq.h>
>
> and you will be able to call it from Rust via:
>
> bindings::__blk_mq_free_request()
>
> in other words, rust_helper_blk_mq_free_request_internal() is probably
> not necessary.

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.

BR Andreas