f2fs: add tracepoint for set_page_dirty

This patch adds a tracepoint for set_page_dirty.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 7bac481..304d5ce 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1225,6 +1225,8 @@
 	struct address_space *mapping = page->mapping;
 	struct f2fs_sb_info *sbi = F2FS_SB(mapping->host->i_sb);
 
+	trace_f2fs_set_page_dirty(page, NODE);
+
 	SetPageUptodate(page);
 	if (!PageDirty(page)) {
 		__set_page_dirty_nobuffers(page);