percpu: introduce PERCPU_PTR() macro

Introduce PERCPU_PTR() macro to cast the percpu pointer from the percpu
address space to a generic (kernel) address space.  Use it in
per_cpu_ptr() and related SHIFT_PERCPU_PTR() macros.

Also remove common knowledge from SHIFT_PERCPU_PTR() comment, "weird cast"
is just a standard way to inform sparse of a cast from the percpu address
space to a generic address space.

Link: https://lkml.kernel.org/r/20241021080856.48746-2-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
index 7fa88c5f4b26c3a9ecf619f7b3c8fc9bc62c0434..e1cf7982424f18c17198965f3787d34ac644ce5a 100644 (file)
--- a/include/linux/percpu-defs.h
+++ b/include/linux/percpu-defs.h
@@ -220,15 +220,17 @@ do {                                                                      \
        (void)__vpp_verify;                                             \
 } while (0)
 
+#define PERCPU_PTR(__p)                                                        \
+       (typeof(*(__p)) __force __kernel *)(__p);
+
 #ifdef CONFIG_SMP
 
 /*
- * Add an offset to a pointer but keep the pointer as-is.  Use RELOC_HIDE()
- * to prevent the compiler from making incorrect assumptions about the
- * pointer value.  The weird cast keeps both GCC and sparse happy.
+ * Add an offset to a pointer.  Use RELOC_HIDE() to prevent the compiler
+ * from making incorrect assumptions about the pointer value.
  */
 #define SHIFT_PERCPU_PTR(__p, __offset)                                        \
-       RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))
+       RELOC_HIDE(PERCPU_PTR(__p), (__offset))
 
 #define per_cpu_ptr(ptr, cpu)                                          \
 ({                                                                     \
@@ -258,7 +260,7 @@ do {                                                                        \
 ({                                                                     \
        (void)(cpu);                                                    \
        __verify_pcpu_ptr(ptr);                                         \
-       (typeof(*(ptr)) __kernel __force *)(ptr);                       \
+       PERCPU_PTR(ptr);                                                \
 })
 
 #define raw_cpu_ptr(ptr)       per_cpu_ptr(ptr, 0)