[PATCH] samples: rust: debugfs: fix excessive stack use

[Gary Guo]

From: Gary Guo <gary@xxxxxxxxxxx>

The current implementation creates a 4K array and move it into the box.
Klint reports that this causes excesssive stack usage:

warning: stack size of `create_file_write` is 4472 bytes, exceeds the 2048-byte limit
  --> samples/rust/rust_debugfs_scoped.rs:54:1
   |
54 | / fn create_file_write(
55 | |     mod_data: &ModuleData,
56 | |     reader: &mut kernel::uaccess::UserSliceReader,
57 | | ) -> Result {
   | |___________^
   |
   = note: the stack size is inferred from instruction `sub $0x1178,%rsp` at .text+2205

Use pin-init to create the array in-place instead.

Fixes: f656279afde1 ("samples: rust: debugfs_scoped: add example for blobs")
Signed-off-by: Gary Guo <gary@xxxxxxxxxxx>
---
 samples/rust/rust_debugfs_scoped.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/rust/rust_debugfs_scoped.rs b/samples/rust/rust_debugfs_scoped.rs
index 6a575a15a2c2..33a4a0865f5b 100644
--- a/samples/rust/rust_debugfs_scoped.rs
+++ b/samples/rust/rust_debugfs_scoped.rs
@@ -75,7 +75,7 @@ fn create_file_write(
             GFP_KERNEL,
         )?;
     }
-    let blob = KBox::pin_init(new_mutex!([0x42; SZ_4K]), GFP_KERNEL)?;
+    let blob = KBox::pin_init(new_mutex!(pin_init::init_array_from_fn(|_| 0x42)), GFP_KERNEL)?;
 
     let scope = KBox::pin_init(
         mod_data.device_dir.scope(

base-commit: b8809969e1d7a591e0f49dd464a5d04b3cf02ab1
-- 
2.54.0