f2fs: add some tracepoints to debug volatile and atomic writes

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 486113d..241b987 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1287,9 +1287,11 @@
 			need_inplace_update(inode))) {
 		rewrite_data_page(page, fio);
 		set_inode_flag(F2FS_I(inode), FI_UPDATE_WRITE);
+		trace_f2fs_do_write_data_page(page, IPU);
 	} else {
 		write_data_page(page, &dn, fio);
 		f2fs_update_extent_cache(&dn);
+		trace_f2fs_do_write_data_page(page, OPU);
 		set_inode_flag(F2FS_I(inode), FI_APPEND_WRITE);
 		if (page->index == 0)
 			set_inode_flag(F2FS_I(inode), FI_FIRST_BLOCK_WRITTEN);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 9e37817..c981819 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -556,6 +556,10 @@
 	META,
 	NR_PAGE_TYPE,
 	META_FLUSH,
+	INMEM,		/* the below types are used by tracepoints only. */
+	INMEM_DROP,
+	IPU,
+	OPU,
 };
 
 struct f2fs_io_info {
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index eafaf72..f939660 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -205,6 +205,8 @@
 	list_add_tail(&new->list, &fi->inmem_pages);
 	inc_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
 	mutex_unlock(&fi->inmem_lock);
+
+	trace_f2fs_register_inmem_page(page, INMEM);
 }
 
 void commit_inmem_pages(struct inode *inode, bool abort)
@@ -238,11 +240,13 @@
 				f2fs_wait_on_page_writeback(cur->page, DATA);
 				if (clear_page_dirty_for_io(cur->page))
 					inode_dec_dirty_pages(inode);
+				trace_f2fs_commit_inmem_page(cur->page, INMEM);
 				do_write_data_page(cur->page, &fio);
 				submit_bio = true;
 			}
 			f2fs_put_page(cur->page, 1);
 		} else {
+			trace_f2fs_commit_inmem_page(cur->page, INMEM_DROP);
 			put_page(cur->page);
 		}
 		radix_tree_delete(&fi->inmem_root, cur->page->index);