block & iov_iter: use bvec iterator to implement iterate_bvec()

From: Ming Lei
Date: Tue Mar 08 2016 - 06:34:12 EST

Hi Guys,

The 1st two patches move bvec iterator helpers out from bio.h, then
they can be used even if CONFIG_BLOCK is disabled, so not necessary
to use iov iter own approach to do the job.

One motivation is that in the future we may support multipage bvecs,
as interests[1] have been shown in this idea, so looks better to
unify the implementation now.


include/linux/bio.h | 55 +------------------------------------------
include/linux/blk_types.h | 4 ++--
include/linux/bvec_iter.h | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
lib/iov_iter.c | 31 +++++++++---------------
4 files changed, 93 insertions(+), 76 deletions(-)