UPSTREAM: f2fs: add dump_stack() in f2fs_handle_critical_error()

To show call stack, so that we can see who causes critical error, note
that it won't call dump_stack() for shutdown path.

Change-Id: Ie24b3beb190d4e3e32a279164542f2d9df80dcd4
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit 4f91f074702af3931a35c244470ae0c4b66f909c)

fs/f2fs/super.c

@@ -4256,6 +4256,8 @@ void f2fs_handle_critical_error(struct f2fs_sb_info *sbi, unsigned char reason)
 
 	if (shutdown)
 		set_sbi_flag(sbi, SBI_IS_SHUTDOWN);
+	else
+		dump_stack();
 
 	/*
 	 * Continue filesystem operators if errors=continue. Should not set