[PATCH] dm: drop BIO_SEG_VALID bit

From: Joe Thornber <thornber@redhat.com>

I just noticed that bio_clone copies the BIO_SEG_VALID bit from the original
bio when it was set.  When we modify bi_idx or bi_vcnt afterwards the segment
counts are invalid and the bit must be dropped (though it is fairly unlikely
that it has already been set).  [Christophe Saout]

drivers/md/dm.c

@@ -338,6 +338,7 @@ static struct bio *clone_bio(struct bio *bio, sector_t sector,
 	clone->bi_idx = idx;
 	clone->bi_vcnt = idx + bv_count;
 	clone->bi_size = to_bytes(len);
+	clone->bi_flags &= ~(1 << BIO_SEG_VALID);
 
 	return clone;
 }