[PATCH] compiler.h: Move barrier() back into compiler-*.h

[Arvind Sankar <nivedita@alum.mit.edu>]

Commit
  b9de06783f01 ("compiler.h: fix barrier_data() on clang")
moved the definition of barrier() into compiler.h.

This causes build failures at least on alpha, because there are files
that rely on barrier() being defined via the implicit include of
compiler_types.h.

Revert this portion of the commit to fix.

Link: https://lore.kernel.org/linux-mm/202010312104.Dk9VQJYb-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Fixes: b9de06783f01 ("compiler.h: fix barrier_data() on clang")
Cc: <stable@vger.kernel.org>
---
 include/linux/compiler-clang.h | 6 ++++++
 include/linux/compiler-gcc.h   | 5 +++++
 include/linux/compiler.h       | 3 +--
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index dd7233c48bf3..230604e7f057 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -60,6 +60,12 @@
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #endif
 
+/* The following are for compatibility with GCC, from compiler-gcc.h,
+ * and may be redefined here because they should not be shared with other
+ * compilers, like ICC.
+ */
+#define barrier() __asm__ __volatile__("" : : : "memory")
+
 #if __has_feature(shadow_call_stack)
 # define __noscs	__attribute__((__no_sanitize__("shadow-call-stack")))
 #endif
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 50912ed00278..a572965c801a 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -15,6 +15,11 @@
 # error Sorry, your version of GCC is too old - please use 4.9 or newer.
 #endif
 
+/* Optimization barrier */
+
+/* The "volatile" is due to gcc bugs */
+#define barrier() __asm__ __volatile__("": : :"memory")
+
 /*
  * This macro obfuscates arithmetic on a variable address so that gcc
  * shouldn't recognize the original var, and make assumptions about it.
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index b8fe0c23cfff..25c803f4222f 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -80,8 +80,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 
 /* Optimization barrier */
 #ifndef barrier
-/* The "volatile" is due to gcc bugs */
-# define barrier() __asm__ __volatile__("": : :"memory")
+# define barrier() __memory_barrier()
 #endif
 
 #ifndef barrier_data
-- 
2.26.2