[PATCH v2] mm/khugepaged: add tracepoint to collapse_file()

[Gautam Menghani]

In the file mm/khugepaged.c, a TODO in the function collapse_file() asks
to add tracepoints. Add the tracepoint named "mm_khugepaged_collapse_file".

Signed-off-by: Gautam Menghani <gautammenghani201@xxxxxxxxx>
---
changes in v2:
1. Move filename dereference out of calling path (Steven Rostedt).
2. Capture is_shmem and index (Zach O'Keefe)

 include/trace/events/huge_memory.h | 38 ++++++++++++++++++++++++++++++
 mm/khugepaged.c                    |  4 +++-
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index 935af4947917..472238d0e3a3 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -203,5 +203,43 @@ TRACE_EVENT(mm_khugepaged_scan_file,
 		__print_symbolic(__entry->result, SCAN_STATUS))
 );
 
+TRACE_EVENT(mm_khugepaged_collapse_file,
+	TP_PROTO(struct mm_struct *mm, struct page *hpage, pgoff_t index,
+			bool is_shmem, unsigned long addr, struct file *file,
+			int nr, int result),
+	TP_ARGS(mm, hpage, index, is_shmem, addr, file, nr, result),
+	TP_STRUCT__entry(
+		__field(struct mm_struct *, mm)
+		__field(unsigned long, hpfn)
+		__field(pgoff_t, index)
+		__field(bool, is_shmem)
+		__field(unsigned long, addr)
+		__string(filename, file->f_path.dentry->d_iname)
+		__field(int, nr)
+		__field(int, result)
+	),
+
+	TP_fast_assign(
+		__entry->mm = mm;
+		__entry->hpfn = hpage ? page_to_pfn(hpage) : -1;
+		__entry->index = index;
+		__entry->is_shmem = is_shmem;
+		__entry->addr = addr;
+		__assign_str(filename, file->f_path.dentry->d_iname);
+		__entry->nr = nr;
+		__entry->result = result;
+	),
+
+	TP_printk("mm=%p, hpage_pfn=0x%lx, index=%ld, is_shmem=%d, addr=%ld, filename=%s, nr=%d, result=%s",
+		__entry->mm,
+		__entry->hpfn,
+		__entry->index,
+		__entry->is_shmem,
+		__entry->addr,
+		__get_str(filename),
+		__entry->nr,
+		__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 4734315f7940..977c0ff82c46 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2059,7 +2059,9 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 		mem_cgroup_uncharge(page_folio(hpage));
 		put_page(hpage);
 	}
-	/* TODO: tracepoints */
+
+	trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem,
+		addr, file, nr, result);
 	return result;
 }
 
-- 
2.34.1