ldd ch06: impl init_completion

bindings_generated.rs does not implement init_completion but only
provide Default trait with writing 0.
So I adds init_swait_queue_head implementation for myself.

Now it generated dead-lock as below.
1. read locks inner to get the mutable reference to completion
2. write also should locks the inner to get the mutable reference to
   completion as well
3. dead-lock

I MUST find out how to get the mutable reference to a object
which is inside of an object wrapped by ArcBorrow.

/ # insmod share/rust_ldd06.ko
[  466.173709] rust_ldd06: module verification failed: signature and/or required key missing - tainting kernel
[  466.176106] rust_completion: rust_ldd06 is loaded
[  466.177064] rust_completion: completion_dev created
/ # mknod /dev/rust_ldd06 c 10 124
/ # cat /dev/rust_ldd06 &
/ # [  489.911819] rust_completion: open is invoked
[  489.913171] rust_completion: read is invoked
[  489.913932] rust_completion: read:dummy=1

/ # echo "asdf" > /dev/rust_ldd06
[  500.059213] rust_completion: open is invoked
[  500.060580] rust_completion: write is invoked

Signed-off-by: Gioh Kim <gurugio@gmail.com>

Author: gurugio

samples/rust/rust_ldd06.rs

@@ -9,11 +9,11 @@
 //! How to use:
 //! / # insmod rust_ldd06.ko
 //! / # mknod /dev/rust_ldd06 c 10 124
+//! / # cat /dev/rust_ldd06 &
 //! / # echo "hello" > /dev/rust_ldd06
-//! / # cat /dev/rust_ldd06
 use kernel::prelude::*;
 use kernel::{
-    bindings,
+    bindings, c_str,
     file::{self, File},
     fmt,
     io_buffer::{IoBufferReader, IoBufferWriter},
@@ -25,7 +25,7 @@ module! {
     type: RustCompletion,
     name: "rust_completion",
     author: "Rust for Linux Contributors",
-    description: "Rust LDD ch06 scull",
+    description: "Rust LDD ch06",
     license: "GPL",
 }
 
@@ -44,8 +44,6 @@ struct CompletionInner {
 // internal info between file operations
 #[pin_data]
 struct CompletionDev {
-    pub completion: bindings::completion,
-
     #[pin]
     inner: Mutex<CompletionInner>,
 }
@@ -54,10 +52,28 @@ struct CompletionDev {
 impl CompletionDev {
     fn try_new() -> Result<Arc<Self>> {
         pr_info!("completion_dev created\n");
+
+        //
+        // #define init_swait_queue_head(q)				\
+        // do {							\
+        //    static struct lock_class_key __key;		\
+        //    __init_swait_queue_head((q), #q, &__key);	\
+        //} while (0)
+        let mut compl = bindings::completion::default();
+        let compl_name = c_str!("completion_dev");
+        let mut key: bindings::lock_class_key = bindings::lock_class_key::default();
+        compl.done = 0;
+        unsafe {
+            bindings::__init_swait_queue_head(
+                &mut compl.wait,
+                compl_name.as_char_ptr() as *mut core::ffi::c_char,
+                &mut key,
+            );
+        }
+
         let dev = Arc::pin_init(pin_init!(Self {
-            completion: bindings::completion::default(), // Default trait is implmented by bindget. See rust/bindings/bindings_generates.rs
             inner <- new_mutex!(CompletionInner {
-                completion: bindings::completion::default(),
+                completion: compl,
                 dummy: 0,
             }),
         }))?;
@@ -108,7 +124,7 @@ impl file::Operations for RustFile {
         data: &mut impl IoBufferReader,
         _offset: u64,
     ) -> Result<usize> {
-        pr_debug!("write is invoked\n");
+        pr_info!("write is invoked\n");
 
         let mut inner_guard = shared.inner.lock();
         pr_info!("write:dummy={}\n", inner_guard.dummy);