block: rnull: Initialize the module in place

Using `InPlaceModule` avoids an allocation and an indirection.

Signed-off-by: Benoît du Garreau <benoit@dugarreau.fr>
Acked-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20241204-rnull_in_place-v1-1-efe3eafac9fb@dugarreau.fr
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 18 insertions, 12 deletions

diff --git a/drivers/block/rnull.rs b/drivers/block/rnull.rs
index 9cca05dcf772..ddf3629d8894 100644
--- a/drivers/block/rnull.rs
+++ b/drivers/block/rnull.rs
@@ -32,25 +32,31 @@ module! {
     license: "GPL v2",
 }
 
+#[pin_data]
 struct NullBlkModule {
-    _disk: Pin<KBox<Mutex<GenDisk<NullBlkDevice>>>>,
+    #[pin]
+    _disk: Mutex<GenDisk<NullBlkDevice>>,
 }
 
-impl kernel::Module for NullBlkModule {
-    fn init(_module: &'static ThisModule) -> Result<Self> {
+impl kernel::InPlaceModule for NullBlkModule {
+    fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
         pr_info!("Rust null_blk loaded\n");
-        let tagset = Arc::pin_init(TagSet::new(1, 256, 1), flags::GFP_KERNEL)?;
 
-        let disk = gen_disk::GenDiskBuilder::new()
-            .capacity_sectors(4096 << 11)
-            .logical_block_size(4096)?
-            .physical_block_size(4096)?
-            .rotational(false)
-            .build(format_args!("rnullb{}", 0), tagset)?;
+        // Use a immediately-called closure as a stable `try` block
+        let disk = /* try */ (|| {
+            let tagset = Arc::pin_init(TagSet::new(1, 256, 1), flags::GFP_KERNEL)?;
 
-        let disk = KBox::pin_init(new_mutex!(disk, "nullb:disk"), flags::GFP_KERNEL)?;
+            gen_disk::GenDiskBuilder::new()
+                .capacity_sectors(4096 << 11)
+                .logical_block_size(4096)?
+                .physical_block_size(4096)?
+                .rotational(false)
+                .build(format_args!("rnullb{}", 0), tagset)
+        })();
 
-        Ok(Self { _disk: disk })
+        try_pin_init!(Self {
+            _disk <- new_mutex!(disk?, "nullb:disk"),
+        })
     }
 }