tree a080f083ccf61b949e41699f2d20f7efffce9114
parent 31b140398ce56ab41646eda7f02bcb78d6a4c916
author Al Viro <viro@zeniv.linux.org.uk> 1394474925 -0400
committer Al Viro <viro@zeniv.linux.org.uk> 1399411967 -0400

give ->direct_IO() a copy of iov_iter

the thing is, we want to advance what's given to ->direct_IO() as we
are forming the request; however, the callers care about the amount
of data actually transferred, not the amount we tried to transfer.
It's more convenient to allow ->direct_IO() instances do use
iov_iter_advance() on the copy of iov_iter, leaving the actual
advancing of the original to caller.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>