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

[Andreas Hindborg <nmi@xxxxxxxxxxxx>]

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>
---
 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(),
             )
         })?;
 
-- 
2.46.0