Add a configfs attribute to configure the virtual memory boundary mask
for the rnull block device. This allows testing how drivers and
filesystems handle devices with specific alignment requirements.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 drivers/block/rnull/configfs.rs |  5 +++++
 drivers/block/rnull/rnull.rs    | 17 ++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs
index 9eaace8b4257e..8b9ad8a1a243b 100644
--- a/drivers/block/rnull/configfs.rs
+++ b/drivers/block/rnull/configfs.rs
@@ -123,6 +123,7 @@ fn make_group(
                 poll_queues: 27,
                 fua: 28,
                 max_sectors: 29,
+                virt_boundary: 30,
             ],
         };
 
@@ -210,6 +211,7 @@ fn make_group(
                     #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
                     init_hctx_inject,
                     max_sectors: 0,
+                    virt_boundary: false,
                 }),
             }),
             default_groups,
@@ -293,6 +295,7 @@ struct DeviceConfigInner {
     #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
     init_hctx_inject: Arc<FaultConfig>,
     max_sectors: u32,
+    virt_boundary: bool,
 }
 
 #[vtable]
@@ -351,6 +354,7 @@ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
                 #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
                 timeout_inject: guard.timeout_inject.clone(),
                 max_sectors: guard.max_sectors,
+                virt_boundary: guard.virt_boundary,
             })?);
             guard.powered = true;
         } else if guard.powered && !power_op {
@@ -629,3 +633,4 @@ 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);
diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index 495a810f4f4e1..dfdb56bd76f52 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -28,7 +28,10 @@
             BadBlocks, //
         },
         bio::Segment,
-        error::{BlkError, BlkResult},
+        error::{
+            BlkError,
+            BlkResult, //
+        },
         mq::{
             self,
             gen_disk::{
@@ -53,6 +56,7 @@
     impl_has_hr_timer,
     new_mutex,
     new_spinlock,
+    page::PAGE_SIZE,
     pr_info,
     prelude::*,
     revocable::Revocable,
@@ -210,6 +214,10 @@
             default: 0,
             description: "Maximum size of a command (in 512B sectors)",
         },
+        virt_boundary: u8 {
+            default: 0,
+            description: "Set alignment requirement for IO buffers to be page size.",
+        },
     },
 }
 
@@ -287,6 +295,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
                     #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
                     timeout_inject: Arc::pin_init(FaultConfig::new(c"timeout_inject"), GFP_KERNEL)?,
                     max_sectors: *module_parameters::max_sectors.value(),
+                    virt_boundary: *module_parameters::virt_boundary.value() != 0,
                 })?;
                 disks.push(disk, GFP_KERNEL)?;
             }
@@ -342,6 +351,7 @@ struct NullBlkOptions<'a> {
     #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
     timeout_inject: Arc<FaultConfig>,
     max_sectors: u32,
+    virt_boundary: bool,
 }
 
 static SHARED_TAG_SET: SetOnce<Arc<TagSet<NullBlkDevice>>> = SetOnce::new();
@@ -414,6 +424,7 @@ fn new(options: NullBlkOptions<'_>) -> Result<Arc<GenDisk<Self>>> {
             #[cfg(CONFIG_BLK_DEV_RUST_NULL_FAULT_INJECTION)]
             timeout_inject,
             max_sectors,
+            virt_boundary,
         } = options;
 
         let mut flags = mq::tag_set::Flags::default();
@@ -512,6 +523,10 @@ fn new(options: NullBlkOptions<'_>) -> Result<Arc<GenDisk<Self>>> {
             .forced_unit_access(forced_unit_access && storage.cache_enabled())
             .max_sectors(max_sectors);
 
+        if virt_boundary {
+            builder = builder.virt_boundary_mask(PAGE_SIZE - 1);
+        }
+
         #[cfg(CONFIG_BLK_DEV_ZONED)]
         {
             builder = builder

-- 
2.51.2