md/raid10: check replacement and rdev to prevent submit the same io twice

After commit 4ca40c2c ("md/raid10: Allow replacement device to be
replace old drive."), 'rdev' and 'replacement' could appear to be
identical. There are already checks for that in wait_blocked_dev() and
raid10_write_request(). Add check for raid10_handle_discard() now.
Signed-off-by: Li Nan <linan122@huawei.com>
Link: https://lore.kernel.org/r/20230701080529.2684932-2-linan666@huaweicloud.comSigned-off-by: Song Liu <song@kernel.org>

drivers/md/raid10.c

@@ -1785,6 +1785,8 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
 		r10_bio->devs[disk].bio = NULL;
 		r10_bio->devs[disk].repl_bio = NULL;
 
+		if (rdev == rrdev)
+			rrdev = NULL;
 		if (rdev && (test_bit(Faulty, &rdev->flags)))
 			rdev = NULL;
 		if (rrdev && (test_bit(Faulty, &rrdev->flags)))