The "bio" is not used in sync_request_write after commit 
a68e58703575
("md/raid1: split out two sub-functions from sync_request_write").
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
 
        struct r1conf *conf = mddev->private;
        int i;
        int disks = conf->raid_disks * 2;
-       struct bio *bio, *wbio;
-
-       bio = r1_bio->bios[r1_bio->read_disk];
+       struct bio *wbio;
 
        if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
                /* ouch - failed to read all of that. */