1 files changed, 80 insertions, 0 deletions
diff --git a/drivers/block/rnull.rs b/drivers/block/rnull.rs
new file mode 100644
index 000000000000..ddf3629d8894
--- /dev/null
+++ b/drivers/block/rnull.rs
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! This is a Rust implementation of the C null block driver.
+//!
+//! Supported features:
+//!
+//! - blk-mq interface
+//! - direct completion
+//! - block size 4k
+//!
+//! The driver is not configurable.
+
+use kernel::{
+    alloc::flags,
+    block::mq::{
+        self,
+        gen_disk::{self, GenDisk},
+        Operations, TagSet,
+    },
+    error::Result,
+    new_mutex, pr_info,
+    prelude::*,
+    sync::{Arc, Mutex},
+    types::ARef,
+};
+
+module! {
+    type: NullBlkModule,
+    name: "rnull_mod",
+    author: "Andreas Hindborg",
+    description: "Rust implementation of the C null block driver",
+    license: "GPL v2",
+}
+
+#[pin_data]
+struct NullBlkModule {
+    #[pin]
+    _disk: Mutex<GenDisk<NullBlkDevice>>,
+}
+
+impl kernel::InPlaceModule for NullBlkModule {
+    fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
+        pr_info!("Rust null_blk loaded\n");
+
+        // 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)?;
+
+            gen_disk::GenDiskBuilder::new()
+                .capacity_sectors(4096 << 11)
+                .logical_block_size(4096)?
+                .physical_block_size(4096)?
+                .rotational(false)
+                .build(format_args!("rnullb{}", 0), tagset)
+        })();
+
+        try_pin_init!(Self {
+            _disk <- new_mutex!(disk?, "nullb:disk"),
+        })
+    }
+}
+
+struct NullBlkDevice;
+
+#[vtable]
+impl Operations for NullBlkDevice {
+    #[inline(always)]
+    fn queue_rq(rq: ARef<mq::Request<Self>>, _is_last: bool) -> Result {
+        mq::Request::end_ok(rq)
+            .map_err(|_e| kernel::error::code::EIO)
+            // We take no refcounts on the request, so we expect to be able to
+            // end the request. The request reference must be unique at this
+            // point, and so `end_ok` cannot fail.
+            .expect("Fatal error - expected to be able to end request");
+
+        Ok(())
+    }
+
+    fn commit_rqs() {}
+}