[PATCH 46/79] block: rust: move gendisk vtable construction to separate function

[Andreas Hindborg <a.hindborg@kernel.org>]

Refactor the `GenDiskBuilder::build` method to move the `gendisk`
vtable construction into a separate helper function. This prepares for
adding zoned block device support which requires conditional vtable
setup.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 drivers/block/rnull/configfs.rs  |  5 ++-
 rust/kernel/block/mq/gen_disk.rs | 66 ++++++++++++++++++++++------------------
 2 files changed, 40 insertions(+), 31 deletions(-)

diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs
index 90f2ecb454285..5dfe7b48af63b 100644
--- a/drivers/block/rnull/configfs.rs
+++ b/drivers/block/rnull/configfs.rs
@@ -266,7 +266,10 @@ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
     }
 }
 
-configfs_simple_field!(DeviceConfig, 1, block_size, u32, check GenDiskBuilder::validate_block_size);
+configfs_simple_field!(DeviceConfig, 1,
+                       block_size, u32,
+                       check GenDiskBuilder::<NullBlkDevice>::validate_block_size
+);
 configfs_simple_bool_field!(DeviceConfig, 2, rotational);
 configfs_simple_field!(DeviceConfig, 3, capacity_mib, u64);
 configfs_simple_field!(DeviceConfig, 4, irq_mode, IRQMode);
diff --git a/rust/kernel/block/mq/gen_disk.rs b/rust/kernel/block/mq/gen_disk.rs
index fbda2f572e17f..eb980079530bd 100644
--- a/rust/kernel/block/mq/gen_disk.rs
+++ b/rust/kernel/block/mq/gen_disk.rs
@@ -17,20 +17,21 @@
     sync::{Arc, UniqueArc},
     types::{ForeignOwnable, ScopeGuard},
 };
-use core::ptr::NonNull;
+use core::{marker::PhantomData, ptr::NonNull};
 
 /// A builder for [`GenDisk`].
 ///
 /// Use this struct to configure and add new [`GenDisk`] to the VFS.
-pub struct GenDiskBuilder {
+pub struct GenDiskBuilder<T> {
     rotational: bool,
     logical_block_size: u32,
     physical_block_size: u32,
     capacity_sectors: u64,
     max_hw_discard_sectors: u32,
+    _p: PhantomData<T>,
 }
 
-impl Default for GenDiskBuilder {
+impl<T> Default for GenDiskBuilder<T> {
     fn default() -> Self {
         Self {
             rotational: false,
@@ -38,11 +39,12 @@ fn default() -> Self {
             physical_block_size: bindings::PAGE_SIZE as u32,
             capacity_sectors: 0,
             max_hw_discard_sectors: 0,
+            _p: PhantomData,
         }
     }
 }
 
-impl GenDiskBuilder {
+impl<T: Operations> GenDiskBuilder<T> {
     /// Create a new instance.
     pub fn new() -> Self {
         Self::default()
@@ -109,7 +111,7 @@ pub fn max_hw_discard_sectors(mut self, max_hw_discard_sectors: u32) -> Self {
     }
 
     /// Build a new `GenDisk` and add it to the VFS.
-    pub fn build<T: Operations>(
+    pub fn build(
         self,
         name: fmt::Arguments<'_>,
         tagset: Arc<TagSet<T>>,
@@ -141,32 +143,8 @@ pub fn build<T: Operations>(
             )
         })?;
 
-        const TABLE: bindings::block_device_operations = bindings::block_device_operations {
-            submit_bio: None,
-            open: None,
-            release: None,
-            ioctl: None,
-            compat_ioctl: None,
-            check_events: None,
-            unlock_native_capacity: None,
-            getgeo: None,
-            set_read_only: None,
-            swap_slot_free_notify: None,
-            report_zones: None,
-            devnode: None,
-            alternative_gpt_sector: None,
-            get_unique_id: None,
-            // TODO: Set to THIS_MODULE. Waiting for const_refs_to_static feature to
-            // be merged (unstable in rustc 1.78 which is staged for linux 6.10)
-            // <https://github.com/rust-lang/rust/issues/119618>
-            owner: core::ptr::null_mut(),
-            pr_ops: core::ptr::null_mut(),
-            free_disk: None,
-            poll_bio: None,
-        };
-
         // SAFETY: `gendisk` is a valid pointer as we initialized it above
-        unsafe { (*gendisk).fops = &TABLE };
+        unsafe { (*gendisk).fops = Self::build_vtable() };
 
         let mut writer = NullTerminatedFormatter::new(
             // SAFETY: `gendisk` points to a valid and initialized instance. We
@@ -219,6 +197,34 @@ pub fn build<T: Operations>(
 
         Ok(disk.into())
     }
+
+    const VTABLE: bindings::block_device_operations = bindings::block_device_operations {
+        submit_bio: None,
+        open: None,
+        release: None,
+        ioctl: None,
+        compat_ioctl: None,
+        check_events: None,
+        unlock_native_capacity: None,
+        getgeo: None,
+        set_read_only: None,
+        swap_slot_free_notify: None,
+        report_zones: None,
+        devnode: None,
+        alternative_gpt_sector: None,
+        get_unique_id: None,
+        // TODO: Set to THIS_MODULE. Waiting for const_refs_to_static feature to
+        // be merged (unstable in rustc 1.78 which is staged for linux 6.10)
+        // <https://github.com/rust-lang/rust/issues/119618>
+        owner: core::ptr::null_mut(),
+        pr_ops: core::ptr::null_mut(),
+        free_disk: None,
+        poll_bio: None,
+    };
+
+    pub(crate) const fn build_vtable() -> &'static bindings::block_device_operations {
+        &Self::VTABLE
+    }
 }
 
 /// A generic block device.

-- 
2.51.2