On Thu, May 28, 2020 at 08:00:52PM +0100, Al Viro wrote: > On Thu, May 28, 2020 at 07:40:38AM +0200, Christoph Hellwig wrote: > > If we write to a file that implements ->write_iter there is no need > > to change the address limit if we send a kvec down. Implement that > > case, and prefer it over using plain ->write with a changed address > > limit if available. > > Umm... It needs a comment along the lines of "weird shits like > /dev/sg that currently check for uaccess_kernel() will just > have to make sure they never switch to ->write_iter()" sg and hid has the uaccess_kernel because it accesses userspace memory not in the range passed to it. Something using write_iter/read_iter should never access any memory outside the iter passed to. rdma has it because it uses write as a bidirectional interface, which obviously can't work at all with an iter. So I'm not sure what we should comment on, but if you have a desire and a proposal for a comment I'll happily add it.
