Re: [PATCH] cifs: Collapse smbd_recv_*() into smbd_recv() and just use copy_to_iter()

[David Howells <dhowells@redhat.com>]

Stefan Metzmacher <metze@samba.org> wrote:

> >   read_rfc1002_done:
> > +		/* SMBDirect will read it all or nothing */
> > +		msg->msg_iter.count = 0;
> 
> And this iov_iter_truncate(0);

Actually, it should probably have been iov_iter_advance().

> While I'm wondering why we had this at all.
> 
> It seems all callers of cifs_read_iter_from_socket()
> don't care and the code path via sock_recvmsg() doesn't
> truncate it just calls copy_to_iter() via this chain:
> ->inet_recvmsg->tcp_recvmsg->skb_copy_datagram_msg->skb_copy_datagram_iter
> ->simple_copy_to_iter->copy_to_iter()
> 
> I think the old code should have called
> iov_iter_advance(rc) instead of msg->msg_iter.count = 0.
> 
> But the new code doesn't need it as copy_to_iter()
> calls iterate_and_advance().

Yeah, it should.  I seem to remember that there were situations in which it
didn't, but it's possible I managed to get rid of them.

> > -	default:
> > -		/* It's a bug in upper layer to get there */
> > -		cifs_dbg(VFS, "Invalid msg type %d\n",
> > -			 iov_iter_type(&msg->msg_iter));
> > -		rc = -EINVAL;
> > -	}
> 
> I guess this is actually a real fix as I just saw
> CIFS: VFS: Invalid msg type 4
> in logs while running the cifs/001 test.
> And 4 is ITER_FOLIOQ.

Ah... Were you using "-o seal"?  The encrypted data is held in a buffer formed
from a folioq with a series of folios in it.

David