[PATCH mm-unstable v2 4/9] mm/khugepaged: add tracepoint to hpage_collapse_scan_file()

["Zach O'Keefe" <zokeefe@google.com>]

Add huge_memory:trace_mm_khugepaged_scan_file tracepoint to
hpage_collapse_scan_file() analogously to hpage_collapse_scan_pmd().
While this change is targeted at debugging MADV_COLLAPSE pathway, the
"mm_khugepaged" prefix is retained for symmetry with
huge_memory:trace_mm_khugepaged_scan_pmd, which retains it's legacy name
to prevent changing kernel ABI as much as possible.

Signed-off-by: Zach O'Keefe <zokeefe@google.com>
---
 include/trace/events/huge_memory.h | 34 ++++++++++++++++++++++++++++++
 mm/khugepaged.c                    |  3 ++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index a8db658e99e9..1d2dd88dc3c4 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -169,5 +169,39 @@ TRACE_EVENT(mm_collapse_huge_page_swapin,
 		__entry->ret)
 );
 
+TRACE_EVENT(mm_khugepaged_scan_file,
+
+	TP_PROTO(struct mm_struct *mm, struct page *page, const char *filename,
+		 int present, int swap, int result),
+
+	TP_ARGS(mm, page, filename, present, swap, result),
+
+	TP_STRUCT__entry(
+		__field(struct mm_struct *, mm)
+		__field(unsigned long, pfn)
+		__string(filename, filename)
+		__field(int, present)
+		__field(int, swap)
+		__field(int, result)
+	),
+
+	TP_fast_assign(
+		__entry->mm = mm;
+		__entry->pfn = page ? page_to_pfn(page) : -1;
+		__assign_str(filename, filename);
+		__entry->present = present;
+		__entry->swap = swap;
+		__entry->result = result;
+	),
+
+	TP_printk("mm=%p, scan_pfn=0x%lx, filename=%s, present=%d, swap=%d, result=%s",
+		__entry->mm,
+		__entry->pfn,
+		__get_str(filename),
+		__entry->present,
+		__entry->swap,
+		__print_symbolic(__entry->result, SCAN_STATUS))
+);
+
 #endif /* __HUGE_MEMORY_H */
 #include <trace/define_trace.h>
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 34c0c74b3839..55144f33ba09 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2171,7 +2171,8 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
 		}
 	}
 
-	/* TODO: tracepoints */
+	trace_mm_khugepaged_scan_file(mm, page, file->f_path.dentry->d_iname,
+				      present, swap, result);
 	return result;
 }
 #else
-- 
2.37.2.672.g94769d06f0-goog