rust: block: introduce `kernel::block::mq` module

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>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20240611114551.228679-2-nmi@metaspace.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 16 insertions, 0 deletions

diff --git a/rust/helpers.c b/rust/helpers.c
index 2c37a0f5d7a8..3df5217fb2ff 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -186,3 +186,19 @@ static_assert(
 	__alignof__(size_t) == __alignof__(uintptr_t),
 	"Rust code expects C `size_t` to match Rust `usize`"
 );
+
+// This will soon be moved to a separate file, so no need to merge with above.
+#include <linux/blk-mq.h>
+#include <linux/blkdev.h>
+
+void *rust_helper_blk_mq_rq_to_pdu(struct request *rq)
+{
+	return blk_mq_rq_to_pdu(rq);
+}
+EXPORT_SYMBOL_GPL(rust_helper_blk_mq_rq_to_pdu);
+
+struct request *rust_helper_blk_mq_rq_from_pdu(void *pdu)
+{
+	return blk_mq_rq_from_pdu(pdu);
+}
+EXPORT_SYMBOL_GPL(rust_helper_blk_mq_rq_from_pdu);