Align bullet points and improve indentation in the `Invariants` section
of the `GenDisk` struct documentation for better readability.

[ Yutaro is also working on implementing the lint we suggested to catch
  this sort of issue in upstream Rust:

    https://github.com/rust-lang/rust-clippy/issues/13601
    https://github.com/rust-lang/rust-clippy/pull/13711

  Thanks a lot! - Miguel ]

Fixes: 3253aba3408a ("rust: block: introduce `kernel::block::mq` module")
Signed-off-by: Yutaro Ohno <yutaro.ono.418@gmail.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Acked-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/ZxkcU5yTFCagg_lX@ohnotp
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

`Result` is used in place of `Result<()>` because the default type
parameters are unit `()` and `Error` types, which are automatically
inferred. Thus keep the usage consistent throughout codebase.

Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://github.com/Rust-for-Linux/linux/issues/1128
Signed-off-by: Manas <manas18244@iiitd.ac.in>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20241118-simplify-result-v3-1-6b1566a77eab@iiitd.ac.in
Signed-off-by: Jens Axboe <axboe@kernel.dk>

When allocating `struct gendisk`, `GenDiskBuilder` is using a dynamic
lock class key without registering the key. This is an incorrect use of
the API, which causes a `WARN` trace.

Fix the issue by using a static lock class key, which is more appropriate
for the situation anyway.

Fixes: 3253aba3408a ("rust: block: introduce `kernel::block::mq` module")
Reported-by: Behme Dirk (XC-CP/ESB5) <Dirk.Behme@de.bosch.com>
Closes: https://rust-for-linux.zulipchat.com/#narrow/stream/x/topic/x/near/457090036
Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Link: https://lore.kernel.org/r/20240815074519.2684107-3-nmi@metaspace.dk
[ Applied `rustfmt`, reworded slightly and made Zulip link
  a permalink. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

`blk_queue_flag_set` and `blk_queue_flag_clear` was removed in favor of a
new API. This caused a build error for Rust block device abstractions.
Thus, use the new feature passing API instead of the old removed API.

Fixes: bd4a633b6f7c ("block: move the nonrot flag to queue_limits")
Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
Link: https://lore.kernel.org/r/20240620085721.1218296-1-nmi@metaspace.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The Rust block layer API was using the old queue limit API, which was just
removed. Use the new API instead.

Reported-by: Boqun Feng <boqun.feng@gmail.com>
Fixes: 3253aba3408a ("rust: block: introduce `kernel::block::mq` module")
Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
Link: https://lore.kernel.org/r/20240614235350.621121-1-nmi@metaspace.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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>