[Linux-stable-mirror] block: two patches for 4.14.x

Hi, there are two commits in master that should be cherry-picked for 4.14.x:

commit 0abc2a10389f0c9070f76ca906c7382788036b93 block: fix blk_rq_append_bio

commit 14cb0dc6479dc5ebc63b3a459a5d89a2f1b39fed block: don't let passthrough IO go into .make_request_fn()

These avoid oopses, especially on x86-32.

Thanks, Michele Ballabio