[PATCH v2 18/83] block: rnull: add `use_per_node_hctx` config option

[Andreas Hindborg]

Add a configfs attribute to enable per-NUMA-node hardware contexts.
When enabled, the driver creates one hardware queue per NUMA node
instead of the default configuration.

Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
---
 drivers/block/rnull/configfs.rs | 24 ++++++++++++++++++++++--
 drivers/block/rnull/rnull.rs    | 28 ++++++++++++++++++++++------
 2 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs
index 0dea92a9079b..71b38373be33 100644
--- a/drivers/block/rnull/configfs.rs
+++ b/drivers/block/rnull/configfs.rs
@@ -33,7 +33,8 @@
     configfs_simple_bool_field,
     configfs_simple_field,
     show_field,
-    store_number_with_power_check, //
+    store_number_with_power_check,
+    store_with_power_check, //
 };
 
 mod macros;
@@ -62,7 +63,7 @@ impl AttributeOperations<0> for Config {
         let mut writer = kernel::str::Formatter::new(page);
         writer.write_str(
             "blocksize,size,rotational,irqmode,completion_nsec,memory_backed,\
-             submit_queues\n",
+             submit_queues,use_per_node_hctx\n",
         )?;
         Ok(writer.bytes_written())
     }
@@ -89,6 +90,7 @@ fn make_group(
                 completion_nsec: 5,
                 memory_backed: 6,
                 submit_queues: 7,
+                use_per_node_hctx: 8,
             ],
         };
 
@@ -268,3 +270,21 @@ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
         Ok(())
     }
 }
+
+configfs_attribute!(DeviceConfig, 8,
+    show: |this, page| show_field(
+        this.data.lock().submit_queues == kernel::numa::num_online_nodes(), page
+    ),
+    store: |this, page| store_with_power_check(this, page, |data, page| {
+        let value = core::str::from_utf8(page)?
+            .trim()
+            .parse::<u8>()
+            .map_err(|_| kernel::error::code::EINVAL)?
+            != 0;
+
+        if value {
+            data.submit_queues = kernel::numa::num_online_nodes();
+        }
+        Ok(())
+    })
+);
diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index a7c35f33631a..30de022146ec 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -21,12 +21,18 @@
         },
     },
     error::Result,
-    memalloc_scope, new_mutex, new_xarray,
+    memalloc_scope,
+    new_mutex,
+    new_xarray,
     page::SafePage,
     pr_info,
     prelude::*,
     str::CString,
-    sync::{aref::ARef, Arc, Mutex},
+    sync::{
+        aref::ARef,
+        Arc,
+        Mutex, //
+    },
     time::{
         hrtimer::{
             HrTimerCallback,
@@ -40,7 +46,7 @@
         OwnableRefCounted,
         Owned, //
     },
-    xarray::XArray,
+    xarray::XArray, //
 };
 
 module! {
@@ -71,8 +77,9 @@
             description:  "IRQ completion handler. 0-none, 1-softirq, 2-timer",
         },
         completion_nsec: u64 {
-            default: 10_000,
-            description:  "Time in ns to complete a request in hardware. Default: 10,000ns",
+                default: 10_000,
+                description:
+            "Time in ns to complete a request in hardware. Default: 10,000ns",
         },
         memory_backed: bool {
             default: false,
@@ -82,6 +89,10 @@
             default: 1,
             description: "Number of submission queues",
         },
+        use_per_node_hctx: bool {
+            default: false,
+            description: "Use per-node allocation for hardware context queues.",
+        },
     },
 }
 
@@ -104,6 +115,11 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
             for i in 0..module_parameters::nr_devices.value() {
                 let name = CString::try_from_fmt(fmt!("rnullb{}", i))?;
 
+                let submit_queues = if module_parameters::use_per_node_hctx.value() {
+                    kernel::numa::num_online_nodes()
+                } else {
+                    module_parameters::submit_queues.value()
+                };
                 let disk = NullBlkDevice::new(NullBlkOptions {
                     name: &name,
                     block_size: module_parameters::bs.value(),
@@ -112,7 +128,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
                     irq_mode: module_parameters::irqmode.value().try_into()?,
                     completion_time: Delta::from_nanos(completion_time),
                     memory_backed: module_parameters::memory_backed.value(),
-                    submit_queues: module_parameters::submit_queues.value(),
+                    submit_queues,
                 })?;
                 disks.push(disk, GFP_KERNEL)?;
             }

-- 
2.51.2