From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756791AbZJBHrx (ORCPT ); Fri, 2 Oct 2009 03:47:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756710AbZJBHrw (ORCPT ); Fri, 2 Oct 2009 03:47:52 -0400 Received: from brick.kernel.dk ([93.163.65.50]:39824 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756288AbZJBHrv (ORCPT ); Fri, 2 Oct 2009 03:47:51 -0400 Date: Fri, 2 Oct 2009 09:47:54 +0200 From: Jens Axboe To: David Miller Cc: torvalds@linux-foundation.org, eric.dumazet@gmail.com, jgunthorpe@obsidianresearch.com, vl@samba.org, opurdila@ixiacom.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: SPLICE_F_NONBLOCK semantics... Message-ID: <20091002074754.GE14918@kernel.dk> References: <20091001.151102.09812927.davem@davemloft.net> <20091001.152717.187318570.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091001.152717.187318570.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 01 2009, David Miller wrote: > From: Linus Torvalds > Date: Thu, 1 Oct 2009 15:21:44 -0700 (PDT) > > > On Thu, 1 Oct 2009, David Miller wrote: > >> > >> It depends upon our interpretation of how you intended the > >> SPLICE_F_NONBLOCK flag to work when you added it way back > >> when. > >> > >> Linus introduced SPLICE_F_NONBLOCK in commit 29e350944fdc2dfca102500790d8ad6d6ff4f69d > >> (splice: add SPLICE_F_NONBLOCK flag ) > >> > >> It doesn't make the splice itself necessarily nonblocking (because the > >> actual file descriptors that are spliced from/to may block unless they > >> have the O_NONBLOCK flag set), but it makes the splice pipe operations > >> nonblocking. > >> > >> Linus intention was clear : let SPLICE_F_NONBLOCK control the splice pipe mode only > > > > Ack. The original intent was for the flag to affect the buffering, not the > > end points. > > Great, thanks for reviewing. > > > Although the more I think about it, the more I suspect that the > > whole NONBLOCK thing should probably have been two bits, and simply > > been about "nonblocking input" vs "nonblocking output" (so that you > > could control both sides on a call-by-call basis). > > I think we could still extend things in this way if we wanted to. > So if you specify the explicit input and/or output nonblock flag, > it takes precedence over the SPLICE_F_NONBLOCK thing. Yes I agree, thank god for having a 'flags' parameter for the syscalls :-). I'll make a note to add and test bidirectional nonblock hints. The net patch looks fine and correct to me, feel free to add my acked-by if you want. -- Jens Axboe