md/raid10: simplify read error handling during recovery.

If a read error is detected during recovery the code currently
fails the read device.
This isn't really necessary.  recovery_request_write will signal
a write error to end_sync_write and it will record a write
error on the destination device which will record a bad block
there or kick it from the array.

So just remove this call to do md_error.
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/raid10.c

@@ -1418,13 +1418,12 @@ static void end_sync_read(struct bio *bio, int error)
 
 	if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 		set_bit(R10BIO_Uptodate, &r10_bio->state);
-	else {
+	else
+		/* The write handler will notice the lack of
+		 * R10BIO_Uptodate and record any errors etc
+		 */
 		atomic_add(r10_bio->sectors,
 			   &conf->mirrors[d].rdev->corrected_errors);
-		if (!test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery))
-			md_error(r10_bio->mddev,
-				 conf->mirrors[d].rdev);
-	}
 
 	/* for reconstruct, we always reschedule after a read.
 	 * for resync, only after all reads