From a8553d87d15bdc58c5d5599cda5d9a1fb2a2a486 Mon Sep 17 00:00:00 2001
From: Sven Van Asbroeck <thesven73@gmail.com>
Date: Fri, 4 Jun 2021 12:54:48 -0400
Subject: [PATCH] rust/kernel: remove config `#ifdef` in mutex.rs file

The use of `#ifdef CONFIG_` statements in .c/.rs files should be
avoided: it makes the code much more unmaintainable over time. See:
https://lore.kernel.org/lkml/YLjWKwhp7akqyR1S@kroah.com/

Use a Rust-C helper instead to leverage automatic `CONFIG` selection
in C kernel headers.

Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
---
 rust/helpers.c            |  7 +++++++
 rust/kernel/sync/mutex.rs | 15 +++++++--------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/rust/helpers.c b/rust/helpers.c
index 3526129f41c79a..cf4ddd705f222c 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -8,6 +8,7 @@
 #include <linux/highmem.h>
 #include <linux/uio.h>
 #include <linux/errname.h>
+#include <linux/mutex.h>
 
 void rust_helper_BUG(void)
 {
@@ -123,6 +124,12 @@ const char *rust_helper_errname(int err)
 	return errname(err);
 }
 
+void rust_helper_mutex_lock(struct mutex *lock)
+{
+	mutex_lock(lock);
+}
+EXPORT_SYMBOL_GPL(rust_helper_mutex_lock);
+
 /* We use bindgen's --size_t-is-usize option to bind the C size_t type
  * as the Rust usize type, so we can use it in contexts where Rust
  * expects a usize like slice (array) indices. usize is defined to be
diff --git a/rust/kernel/sync/mutex.rs b/rust/kernel/sync/mutex.rs
index 0a4371a7db6c74..74654631c8ce1b 100644
--- a/rust/kernel/sync/mutex.rs
+++ b/rust/kernel/sync/mutex.rs
@@ -77,19 +77,18 @@ impl<T: ?Sized> NeedsLockClass for Mutex<T> {
     }
 }
 
+extern "C" {
+    fn rust_helper_mutex_lock(mutex: *mut bindings::mutex);
+}
+
 impl<T: ?Sized> Lock for Mutex<T> {
     type Inner = T;
 
-    #[cfg(not(CONFIG_DEBUG_LOCK_ALLOC))]
     fn lock_noguard(&self) {
         // SAFETY: `mutex` points to valid memory.
-        unsafe { bindings::mutex_lock(self.mutex.get()) };
-    }
-
-    #[cfg(CONFIG_DEBUG_LOCK_ALLOC)]
-    fn lock_noguard(&self) {
-        // SAFETY: `mutex` points to valid memory.
-        unsafe { bindings::mutex_lock_nested(self.mutex.get(), 0) };
+        unsafe {
+            rust_helper_mutex_lock(self.mutex.get());
+        }
     }
 
     unsafe fn unlock(&self) {