cma: tracing: print alloc result in trace_cma_alloc_finish

The result of the allocation attempt is not printed in
trace_cma_alloc_finish, but it's important to do it so we can set filters
to catch specific errors on allocation or to trigger some operations on
specific errors.

We have printed the result in log, but the log is conditional and could
not be filtered by tracing events.

It introduces little overhead to print this result.  The result of
allocation is named `errorno' in the trace.

Link: https://lkml.kernel.org/r/20221208142130.1501195-1-haowenchao@huawei.comSigned-off-by: Wenchao Hao <haowenchao@huawei.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/trace/events/cma.h

@@ -91,12 +91,38 @@ TRACE_EVENT(cma_alloc_start,
 		  __entry->align)
 );
 
-DEFINE_EVENT(cma_alloc_class, cma_alloc_finish,
+TRACE_EVENT(cma_alloc_finish,
 
 	TP_PROTO(const char *name, unsigned long pfn, const struct page *page,
-		 unsigned long count, unsigned int align),
+		 unsigned long count, unsigned int align, int errorno),
 
-	TP_ARGS(name, pfn, page, count, align)
+	TP_ARGS(name, pfn, page, count, align, errorno),
+
+	TP_STRUCT__entry(
+		__string(name, name)
+		__field(unsigned long, pfn)
+		__field(const struct page *, page)
+		__field(unsigned long, count)
+		__field(unsigned int, align)
+		__field(int, errorno)
+	),
+
+	TP_fast_assign(
+		__assign_str(name, name);
+		__entry->pfn = pfn;
+		__entry->page = page;
+		__entry->count = count;
+		__entry->align = align;
+		__entry->errorno = errorno;
+	),
+
+	TP_printk("name=%s pfn=0x%lx page=%p count=%lu align=%u errorno=%d",
+		  __get_str(name),
+		  __entry->pfn,
+		  __entry->page,
+		  __entry->count,
+		  __entry->align,
+		  __entry->errorno)
 );
 
 DEFINE_EVENT(cma_alloc_class, cma_alloc_busy_retry,

mm/cma.c

@@ -491,7 +491,7 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
 		start = bitmap_no + mask + 1;
 	}
 
-	trace_cma_alloc_finish(cma->name, pfn, page, count, align);
+	trace_cma_alloc_finish(cma->name, pfn, page, count, align, ret);
 
 	/*
 	 * CMA can allocate multiple page blocks, which results in different