ceph: define ceph_writepages_osd_request()

Mostly for readability, define ceph_writepages_osd_request() and
use it to allocate the osd request for ceph_writepages_start().

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
1 file changed