rnull: add soft-irq completion support

rnull currently only supports direct completion. Add option for completing
requests across CPU nodes via soft IRQ or IPI.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20250902-rnull-up-v6-16-v7-17-b5212cc89b98@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 21 insertions, 11 deletions

diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index a19c55717c4f..1ec694d7f1a6 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -4,6 +4,7 @@
 
 mod configfs;
 
+use configfs::IRQMode;
 use kernel::{
     block::{
         self,
@@ -53,35 +54,44 @@ impl NullBlkDevice {
         block_size: u32,
         rotational: bool,
         capacity_mib: u64,
+        irq_mode: IRQMode,
     ) -> Result<GenDisk<Self>> {
         let tagset = Arc::pin_init(TagSet::new(1, 256, 1), GFP_KERNEL)?;
 
+        let queue_data = Box::new(QueueData { irq_mode }, GFP_KERNEL)?;
+
         gen_disk::GenDiskBuilder::new()
             .capacity_sectors(capacity_mib << (20 - block::SECTOR_SHIFT))
             .logical_block_size(block_size)?
             .physical_block_size(block_size)?
             .rotational(rotational)
-            .build(fmt!("{}", name.to_str()?), tagset, ())
+            .build(fmt!("{}", name.to_str()?), tagset, queue_data)
     }
 }
 
+struct QueueData {
+    irq_mode: IRQMode,
+}
+
 #[vtable]
 impl Operations for NullBlkDevice {
-    type QueueData = ();
+    type QueueData = KBox<QueueData>;
 
     #[inline(always)]
-    fn queue_rq(_queue_data: (), 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");
-
+    fn queue_rq(queue_data: &QueueData, rq: ARef<mq::Request<Self>>, _is_last: bool) -> Result {
+        match queue_data.irq_mode {
+            IRQMode::None => 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"),
+            IRQMode::Soft => mq::Request::complete(rq),
+        }
         Ok(())
     }
 
-    fn commit_rqs(_queue_data: ()) {}
+    fn commit_rqs(_queue_data: &QueueData) {}
 
     fn complete(rq: ARef<mq::Request<Self>>) {
         mq::Request::end_ok(rq)