Hi,
Interests[1] have been shown in multipage bvecs, so this patchset
try to prepare for the support and do two things:
1) the 1st 4 patches use bvec iterator to implement iterate_bvec(),
then we can drop the non-standard way for iterating bvec, which
can be thought as a good cleanup for lib/iov_iter.c
2) remove BIO_MAX_SECTORS and makre BIO_MAX_SIZE as obsolete, and
now there is only one user for each. Once multipage bvecs is introduced,
one bio may hold lots of sectors, and we should always use sort of
BIO_MAX_VECS which should be introduced in future and is similiar
with current BIO_MAX_PAGES.
The only functional change is iterate_bvec():lib/iov_iter.c
xfstests(-a auto) over loop aio is run for ext4/xfs to verify
the change and no regression found with this patchset.