md/raid10: properly indicate failure when ending a failed write request

Similar to [1], this patch fixes the same bug in raid10. Also cleanup the
comments.

[1] commit 2417b986 ("md/raid1: properly indicate failure when ending
                         a failed write request")
Cc: stable@vger.kernel.org
Fixes: 7cee6d4e ("md/raid10: end bio when the device faulty")
Signed-off-by: Wei Shuyu <wsy@dogben.com>
Acked-by: Guoqing Jiang <jiangguoqing@kylinos.cn>
Signed-off-by: Song Liu <song@kernel.org>

drivers/md/raid1.c

@@ -472,8 +472,6 @@ static void raid1_end_write_request(struct bio *bio)
 		/*
 		 * When the device is faulty, it is not necessary to
 		 * handle write error.
-		 * For failfast, this is the only remaining device,
-		 * We need to retry the write without FailFast.
 		 */
 		if (!test_bit(Faulty, &rdev->flags))
 			set_bit(R1BIO_WriteError, &r1_bio->state);

drivers/md/raid10.c

@@ -469,12 +469,12 @@ static void raid10_end_write_request(struct bio *bio)
 			/*
 			 * When the device is faulty, it is not necessary to
 			 * handle write error.
-			 * For failfast, this is the only remaining device,
-			 * We need to retry the write without FailFast.
 			 */
 			if (!test_bit(Faulty, &rdev->flags))
 				set_bit(R10BIO_WriteError, &r10_bio->state);
 			else {
+				/* Fail the request */
+				set_bit(R10BIO_Degraded, &r10_bio->state);
 				r10_bio->devs[slot].bio = NULL;
 				to_put = bio;
 				dec_rdev = 1;