io-wq: ensure work->task_pid is cleared on init

to #28170604

commit 2d141dd2caa78fbaf87b57c27769bdc14975ab3d upstream

We use ->task_pid for exit cancellation, but we need to ensure it's
cleared to zero for io_req_work_grab_env() to do the right thing. Take
a suggestion from Bart and clear the whole thing, just setting the
function passed in. This makes it more future proof as well.

Fixes: 36282881a795 ("io-wq: add io_wq_cancel_pid() to cancel based on a specific pid")
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Acked-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>

fs/io-wq.h

@@ -78,16 +78,10 @@ struct io_wq_work {
 	pid_t task_pid;
 };
 
-#define INIT_IO_WORK(work, _func)			\
-	do {						\
-		(work)->list.next = NULL;		\
-		(work)->func = _func;			\
-		(work)->files = NULL;			\
-		(work)->mm = NULL;			\
-		(work)->creds = NULL;			\
-		(work)->fs = NULL;			\
-		(work)->flags = 0;			\
-	} while (0)					\
+#define INIT_IO_WORK(work, _func)				\
+	do {							\
+		*(work) = (struct io_wq_work){ .func = _func };	\
+	} while (0)						\
 
 typedef void (get_work_fn)(struct io_wq_work *);
 typedef void (put_work_fn)(struct io_wq_work *);