io_uring: cancel-match based on flags

Instead of going into request internals, like checking req->file->f_op,
do match them based on REQ_F_INFLIGHT, it's set only when we want it to
be reliably cancelled.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -703,7 +703,7 @@ enum {
 
 	/* fail rest of links */
 	REQ_F_FAIL_LINK		= BIT(REQ_F_FAIL_LINK_BIT),
-	/* on inflight list */
+	/* on inflight list, should be cancelled and waited on exit reliably */
 	REQ_F_INFLIGHT		= BIT(REQ_F_INFLIGHT_BIT),
 	/* read/write uses file position */
 	REQ_F_CUR_POS		= BIT(REQ_F_CUR_POS_BIT),
@@ -1069,7 +1069,7 @@ static bool io_match_task(struct io_kiocb *head,
 		return true;
 
 	io_for_each_link(req, head) {
-		if (req->file && req->file->f_op == &io_uring_fops)
+		if (req->flags & REQ_F_INFLIGHT)
 			return true;
 		if (req->task->files == files)
 			return true;