[PATCH v2 82/83] block: rnull: add `shared_tag_bitmap` config option

[Andreas Hindborg]

Add a configfs attribute and module parameter to enable the
`BLK_MQ_F_TAG_HCTX_SHARED` flag for the rnull tag set. When enabled,
a tag bitmap is shared across all hardware queues.

Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
---
 drivers/block/rnull/configfs.rs       |  5 +++++
 drivers/block/rnull/rnull.rs          | 12 ++++++++++++
 rust/kernel/block/mq/tag_set/flags.rs |  4 ++++
 3 files changed, 21 insertions(+)

diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs
index 3e054339226c..1bab38c55698 100644
--- a/drivers/block/rnull/configfs.rs
+++ b/drivers/block/rnull/configfs.rs
@@ -134,6 +134,7 @@ fn make_group(
                 fua: 28,
                 max_sectors: 29,
                 virt_boundary: 30,
+                shared_tag_bitmap: 31,
             ],
         };
 
@@ -223,6 +224,7 @@ fn make_group(
                     init_hctx_inject,
                     max_sectors: 0,
                     virt_boundary: false,
+                    shared_tag_bitmap: false,
                 }),
             }),
             default_groups,
@@ -318,6 +320,7 @@ struct DeviceConfigInner {
     init_hctx_inject: Arc<FaultConfig>,
     max_sectors: u32,
     virt_boundary: bool,
+    shared_tag_bitmap: bool,
 }
 
 #[vtable]
@@ -374,6 +377,7 @@ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
                     blocking: guard.blocking,
                     memory_backed: guard.memory_backed,
                     no_sched: guard.no_sched,
+                    shared_tag_bitmap: guard.shared_tag_bitmap,
                     hw_queue_depth: guard.hw_queue_depth,
                     #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
                     init_hctx_inject: guard.init_hctx_inject.clone(),
@@ -622,3 +626,4 @@ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
 configfs_simple_bool_field!(DeviceConfig, 28, fua);
 configfs_simple_field!(DeviceConfig, 29, max_sectors, u32);
 configfs_simple_bool_field!(DeviceConfig, 30, virt_boundary);
+configfs_simple_bool_field!(DeviceConfig, 31, shared_tag_bitmap);
diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index 147dc8498c3a..81f9e2d03f31 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -216,6 +216,10 @@
             default: false,
             description: "Set alignment requirement for IO buffers to be page size.",
         },
+        shared_tag_bitmap: bool {
+            default: false,
+            description: "Use shared tag bitmap for all submission queues for blk-mq.",
+        },
     },
 }
 
@@ -245,6 +249,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
             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_bitmap = module_parameters::shared_tag_bitmap.value();
 
             let shared_tag_set = NullBlkDevice::build_tag_set(TagSetOptions {
                 home_node,
@@ -258,6 +263,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
                 blocking,
                 memory_backed,
                 no_sched,
+                shared_tag_bitmap,
                 hw_queue_depth,
                 #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
                 init_hctx_inject: Arc::pin_init(
@@ -300,6 +306,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
                         blocking,
                         memory_backed,
                         no_sched,
+                        shared_tag_bitmap,
                         hw_queue_depth,
                         #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
                         init_hctx_inject: Arc::pin_init(
@@ -404,6 +411,7 @@ struct TagSetOptions {
     blocking: bool,
     memory_backed: bool,
     no_sched: bool,
+    shared_tag_bitmap: bool,
     hw_queue_depth: u32,
     #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
     init_hctx_inject: Arc<FaultConfig>,
@@ -419,6 +427,7 @@ fn build_tag_set(options: TagSetOptions) -> Result<Arc<TagSet<Self>>> {
             blocking,
             memory_backed,
             no_sched,
+            shared_tag_bitmap,
             hw_queue_depth,
             #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
             init_hctx_inject,
@@ -441,6 +450,9 @@ fn build_tag_set(options: TagSetOptions) -> Result<Arc<TagSet<Self>>> {
         if no_sched {
             flags |= mq::tag_set::Flag::NoDefaultScheduler;
         }
+        if shared_tag_bitmap {
+            flags |= mq::tag_set::Flag::TagHctxShared;
+        }
 
         let queue_config_guard = queue_config.lock();
         let submit_queues = queue_config_guard.submit_queues;
diff --git a/rust/kernel/block/mq/tag_set/flags.rs b/rust/kernel/block/mq/tag_set/flags.rs
index 2561d7090c49..afc9d31ed998 100644
--- a/rust/kernel/block/mq/tag_set/flags.rs
+++ b/rust/kernel/block/mq/tag_set/flags.rs
@@ -21,5 +21,9 @@ pub enum Flag {
         /// Select 'none' during queue registration in case of a single hwq or shared
         /// hwqs instead of 'mq-deadline'.
         NoDefaultScheduler = bindings::BLK_MQ_F_NO_SCHED_BY_DEFAULT,
+
+        /// Use shared tag bitmap for all submission queues.
+        TagHctxShared = bindings::BLK_MQ_F_TAG_HCTX_SHARED,
+
     }
 }

-- 
2.51.2