On Thu, 2014-11-20 at 22:25 +0000, Al Viro wrote: > Yes, it is. You are breaking several _other_ kernel_sendmsg() users. > They are already slightly broken, but that'll make breakage much more > common. > > Please, don't - the right thing to do is to have iov_iter in msghdr > (we already have the kernel and userland ones with different types and > we do not assume their layouts to be identical - currently they are, > but it's easy to change), keep iovec constant in all cases and advance > ->msg_iter. Also in all cases. > > Note that direct manipulations of what's currently in ->msg_iov are > wrong - all those loops over vector elements, etc., belong in low-level > primitives. The main missing ones right now are csum_and_copy_{from,to}_iter() > - I have those in local queue, but I'm still trying to get a reasonably > clean mm/iov_iter.c without ridiculous amounts of boilerplating. A bit more > massage is needed there... > > Seriously, take a look at vfs.git#iov_iter-net; it's preparations for the > one that'll introduce ->msg_iter. Right now that branch has local iov_iter > declared and initialized in several ->sendmsg() and ->recvmsg() instances and > fed to primitives that work with it; after the conversion it'll be in > msg->msg_iter and it will be initialized by sock_sendmsg()/sock_recvmsg(). > > The tricky part is how to get through that without temporary breaking the > existing sendmsg/recvmsg users in the kernel *and* without a patch size from > hell. I more or less see how to carve the remaining steps into > reasonably-sized chunks; iscsi is one of the tricky ones and it, AFAICS, > is genuinely broken in mainline and will need fixes that can go into -stable. > > And no, your solution doesn't work. Sorry. You'll break e.g. smb_send_kvec() > that way. ceph_tcp_sendmsg() as well, IIRC. Nowhere in tcp_sendmsg() the iov had const qualifier. If it was declared as const, this discussion would not happen, we would know we are not allowed to modify it. iov_iter is nice, but not a single time it is used in net/ Please make sure to add const where appropriate. Thanks. -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html