tracing: Use pr_err() instead of WARN() for memory failures

As warnings can trigger panics, especially when "panic_on_warn" is set,
memory failure warnings can cause panics and fail fuzz testers that are
stressing memory.

Create a MEM_FAIL() macro to use instead of WARN() in the tracing code
(perhaps this should be a kernel wide macro?), and use that for memory
failure issues. This should stop failing fuzz tests due to warnings.

Link: https://lore.kernel.org/r/CACT4Y+ZP-7np20GVRu3p+eZys9GPtbu+JpfV+HtsufAzvTgJrg@mail.gmail.com

Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace.h

@@ -94,6 +94,18 @@ enum trace_type {
 
 #include "trace_entries.h"
 
+/* Use this for memory failure errors */
+#define MEM_FAIL(condition, fmt, ...) ({			\
+	static bool __section(.data.once) __warned;		\
+	int __ret_warn_once = !!(condition);			\
+								\
+	if (unlikely(__ret_warn_once && !__warned)) {		\
+		__warned = true;				\
+		pr_err("ERROR: " fmt, ##__VA_ARGS__);		\
+	}							\
+	unlikely(__ret_warn_once);				\
+})
+
 /*
  * syscalls are special, and need special handling, this is why
  * they are not included in trace_entries.h