Add a configfs attribute to configure the queue depth (number of tags)
for the rnull block device.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 drivers/block/rnull/configfs.rs |  5 +++++
 drivers/block/rnull/rnull.rs    | 11 ++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs
index a84854e7c358..2dfc87dff66a 100644
--- a/drivers/block/rnull/configfs.rs
+++ b/drivers/block/rnull/configfs.rs
@@ -118,6 +118,7 @@ fn make_group(
                 mbps: 16,
                 blocking: 17,
                 shared_tags: 18,
+                hw_queue_depth: 19
             ],
         };
 
@@ -153,6 +154,7 @@ fn make_group(
                     blocking: false,
                     shared_tags: false,
                     shared_tag_set: self.shared_tag_set.clone(),
+                    hw_queue_depth: 64,
                 }),
             }),
             core::iter::empty(),
@@ -231,6 +233,7 @@ struct DeviceConfigInner {
     blocking: bool,
     shared_tags: bool,
     shared_tag_set: Arc<TagSet<NullBlkDevice>>,
+    hw_queue_depth: u32,
 }
 
 #[vtable]
@@ -274,6 +277,7 @@ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
                     blocking: guard.blocking,
                     memory_backed: guard.memory_backed,
                     no_sched: guard.no_sched,
+                    hw_queue_depth: guard.hw_queue_depth,
                 },
             })?);
             guard.powered = true;
@@ -447,3 +451,4 @@ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
 configfs_simple_field!(DeviceConfig, 16, mbps, u32);
 configfs_simple_bool_field!(DeviceConfig, 17, blocking);
 configfs_simple_bool_field!(DeviceConfig, 18, shared_tags);
+configfs_simple_field!(DeviceConfig, 19, hw_queue_depth, u32);
diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index bcf6a85f1cbc..491979daa50e 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -147,6 +147,10 @@
             default: false,
             description: "Share tag set between devices for blk-mq",
         },
+        hw_queue_depth: u32 {
+            default: 64,
+            description:  "Queue depth for each hardware queue. Default: 64",
+        },
     },
 }
 
@@ -172,6 +176,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
             let blocking = module_parameters::blocking.value();
             let memory_backed = module_parameters::memory_backed.value();
             let no_sched = module_parameters::no_sched.value();
+            let hw_queue_depth = module_parameters::hw_queue_depth.value();
 
             let shared_tag_set = NullBlkDevice::build_tag_set(TagSetOptions {
                 submit_queues,
@@ -179,6 +184,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
                 blocking,
                 memory_backed,
                 no_sched,
+                hw_queue_depth,
             })?;
 
             let mut disks = KVec::new();
@@ -209,6 +215,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
                         blocking,
                         memory_backed,
                         no_sched,
+                        hw_queue_depth,
                     },
                 })?;
                 disks.push(disk, GFP_KERNEL)?;
@@ -264,6 +271,7 @@ struct TagSetOptions {
     blocking: bool,
     memory_backed: bool,
     no_sched: bool,
+    hw_queue_depth: u32,
 }
 
 impl NullBlkDevice {
@@ -276,6 +284,7 @@ fn build_tag_set(options: TagSetOptions) -> Result<Arc<TagSet<Self>>> {
             blocking,
             memory_backed,
             no_sched,
+            hw_queue_depth,
         } = options;
 
         if home_node > kernel::numa::num_online_nodes().try_into()? {
@@ -297,7 +306,7 @@ fn build_tag_set(options: TagSetOptions) -> Result<Arc<TagSet<Self>>> {
         }
 
         Arc::pin_init(
-            TagSet::new(submit_queues, (), 256, 1, numa_node, flags),
+            TagSet::new(submit_queues, (), hw_queue_depth, 1, numa_node, flags),
             GFP_KERNEL,
         )
     }

-- 
2.51.2