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    | 9 ++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs
index d1a70fe030cb2..90f2ecb454285 100644
--- a/drivers/block/rnull/configfs.rs
+++ b/drivers/block/rnull/configfs.rs
@@ -108,6 +108,7 @@ fn make_group(
                 mbps: 16,
                 blocking: 17,
                 shared_tags: 18,
+                hw_queue_depth: 19
             ],
         };
 
@@ -142,6 +143,7 @@ fn make_group(
                     mbps: 0,
                     blocking: false,
                     shared_tags: false,
+                    hw_queue_depth: 64,
                 }),
             }),
             core::iter::empty(),
@@ -209,6 +211,7 @@ struct DeviceConfigInner {
     mbps: u32,
     blocking: bool,
     shared_tags: bool,
+    hw_queue_depth: u32,
 }
 
 #[vtable]
@@ -251,6 +254,7 @@ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
                 bandwidth_limit: u64::from(guard.mbps) * 2u64.pow(20),
                 blocking: guard.blocking,
                 shared_tags: guard.shared_tags,
+                hw_queue_depth: guard.hw_queue_depth,
             })?);
             guard.powered = true;
         } else if guard.powered && !power_op {
@@ -472,3 +476,4 @@ 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 84e75a7042214..3fb19836ce6ff 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -149,6 +149,10 @@
             default: 0,
             description: "Share tag set between devices for blk-mq",
         },
+        hw_queue_depth: u32 {
+            default: 64,
+            description:  "Queue depth for each hardware queue. Default: 64",
+        },
     },
 }
 
@@ -197,6 +201,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
                     bandwidth_limit: u64::from(*module_parameters::mbps.value()) * 2u64.pow(20),
                     blocking: *module_parameters::blocking.value() != 0,
                     shared_tags: *module_parameters::shared_tags.value() != 0,
+                    hw_queue_depth: *module_parameters::hw_queue_depth.value(),
                 })?;
                 disks.push(disk, GFP_KERNEL)?;
             }
@@ -230,6 +235,7 @@ struct NullBlkOptions<'a> {
     bandwidth_limit: u64,
     blocking: bool,
     shared_tags: bool,
+    hw_queue_depth: u32,
 }
 
 static SHARED_TAG_SET: SetOnce<Arc<TagSet<NullBlkDevice>>> = SetOnce::new();
@@ -276,6 +282,7 @@ fn new(options: NullBlkOptions<'_>) -> Result<Arc<GenDisk<Self>>> {
             bandwidth_limit,
             blocking,
             shared_tags,
+            hw_queue_depth,
         } = options;
 
         let mut flags = mq::tag_set::Flags::default();
@@ -297,7 +304,7 @@ fn new(options: NullBlkOptions<'_>) -> Result<Arc<GenDisk<Self>>> {
 
         let tagset_ctor = || -> Result<Arc<_>> {
             Arc::pin_init(
-                TagSet::new(submit_queues, (), 256, 1, home_node, flags),
+                TagSet::new(submit_queues, (), hw_queue_depth, 1, home_node, flags),
                 GFP_KERNEL,
             )
         };

-- 
2.51.2