[PATCH 00/35 v2] separate operations from flags in the bio/request structs

[mchristi@xxxxxxxxxx]

The following patches begin to cleanup the request->cmd_flags and
bio->bi_rw mess. We currently use cmd_flags to specify the operation,
attributes and state of the request. For bi_rw we use it for similar
info and also the priority but then also have another bi_flags field
for state. At some point, we abused them so much we just made cmd_flags
64 bits, so we could add more.

The following patches seperate the operation (read, write discard,
flush, etc) from cmd_flags/bi_rw.

This patchset was made against linux-next from today Jan 5 2016.
(git tag next-20160105).

v2.

1. Dropped arguments from submit_bio, and had callers setup
bio.
2. Add REQ_OP_FLUSH for request_fn users and renamed REQ_FLUSH
to REQ_PREFLUSH for make_request_fn users.
3. Dropped bio/rq_data_dir functions, and added a op_is_write
function instead.