Re: [PATCH 2/2] rust: block: fix wrong usage of lockdep API

[Dirk Behme]

On 15.08.2024 09:49, Andreas Hindborg wrote:
> From: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>
>
> When allocating `struct gendisk`, `GenDiskBuilder` is using a dynamic lock
> class key without registering the key. This is incorrect use of the API,
> which causes a `WARN` trace. This patch fixes 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@xxxxxxxxxxxx>
> Closes: https://rust-for-linux.zulipchat.com/#narrow/stream/288089-General/topic/6.2E11.2E0-rc1.3A.20rust.2Fkernel.2Fblock.2Fmq.2Ers.3A.20doctest.20lock.20warning
> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>

Tested-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>

Many thanks! :)

Dirk

> ---
>   rust/kernel/block/mq/gen_disk.rs | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/rust/kernel/block/mq/gen_disk.rs b/rust/kernel/block/mq/gen_disk.rs
> index f548a6199847..dbe560b09953 100644
> --- a/rust/kernel/block/mq/gen_disk.rs
> +++ b/rust/kernel/block/mq/gen_disk.rs
> @@ -6,7 +6,7 @@
>   //! C header: [`include/linux/blk_mq.h`](srctree/include/linux/blk_mq.h)
>   
>   use crate::block::mq::{raw_writer::RawWriter, Operations, TagSet};
> -use crate::error;
> +use crate::{error, static_lock_class};
>   use crate::{bindings, error::from_err_ptr, error::Result, sync::Arc};
>   use core::fmt::{self, Write};
>   
> @@ -93,8 +93,6 @@ pub fn build<T: Operations>(
>           name: fmt::Arguments<'_>,
>           tagset: Arc<TagSet<T>>,
>       ) -> Result<GenDisk<T>> {
> -        let lock_class_key = crate::sync::LockClassKey::new();
> -
>           // SAFETY: `bindings::queue_limits` contain only fields that are valid when zeroed.
>           let mut lim: bindings::queue_limits = unsafe { core::mem::zeroed() };
>   
> @@ -110,7 +108,7 @@ pub fn build<T: Operations>(
>                   tagset.raw_tag_set(),
>                   &mut lim,
>                   core::ptr::null_mut(),
> -                lock_class_key.as_ptr(),
> +                static_lock_class!().as_ptr(),
>               )
>           })?;
>   

--
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Dirk Behme                      Robert Bosch Car Multimedia GmbH
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