[PATCH] cma:tracing: Print alloc result in trace_cma_alloc_finish

[Wenchao Hao]

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

Although we have printed the result in log, but the log is
conditional and could not be filtered by tracing event.

What's more, it introduce little overhead to print this result.
The result of allocation is named as errorno in trace.

Signed-off-by: Wenchao Hao <haowenchao@xxxxxxxxxx>
---
 include/trace/events/cma.h | 32 +++++++++++++++++++++++++++++---
 mm/cma.c                   |  2 +-
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/cma.h b/include/trace/events/cma.h
index 3d708dae1542..ef75ea606ab2 100644
--- a/include/trace/events/cma.h
+++ b/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,
diff --git a/mm/cma.c b/mm/cma.c
index 4a978e09547a..a75b17b03b66 100644
--- a/mm/cma.c
+++ b/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
-- 
2.32.0