gfs2: Fix use of bio_chain

In gfs2_chain_bio(), the call to bio_chain() has its arguments swapped.
The result is leaked bios and incorrect synchronization (only the last
bio will actually be waited for).  This code is only used during mount
and filesystem thaw, so the bug normally won't be noticeable.

Reported-by: Stephen Zhang <starzhangzsd@gmail.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Author: Andreas Gruenbacher

fs/gfs2/lops.c

@@ -484,7 +484,7 @@ static struct bio *gfs2_chain_bio(struct bio *prev, unsigned int nr_iovecs)
 	new = bio_alloc(prev->bi_bdev, nr_iovecs, prev->bi_opf, GFP_NOIO);
 	bio_clone_blkg_association(new, prev);
 	new->bi_iter.bi_sector = bio_end_sector(prev);
-	bio_chain(new, prev);
+	bio_chain(prev, new);
 	submit_bio(prev);
 	return new;
 }