f2fs: fix missing skip pages info

fix missing skip pages info in f2fs_writepages trace event.

Signed-off-by: Yunlei He <heyunlei@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 95e05256..a27f7de 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1342,8 +1342,6 @@
 	int ret;
 	long diff;
 
-	trace_f2fs_writepages(mapping->host, wbc, DATA);
-
 	/* deal with chardevs and other special file */
 	if (!mapping->a_ops->writepage)
 		return 0;
@@ -1365,6 +1363,8 @@
 	if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
 		goto skip_write;
 
+	trace_f2fs_writepages(mapping->host, wbc, DATA);
+
 	diff = nr_pages_to_write(sbi, DATA, wbc);
 
 	if (!S_ISDIR(inode->i_mode) && wbc->sync_mode == WB_SYNC_ALL) {
@@ -1383,6 +1383,7 @@
 
 skip_write:
 	wbc->pages_skipped += get_dirty_pages(inode);
+	trace_f2fs_writepages(mapping->host, wbc, DATA);
 	return 0;
 }