From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761458AbZCaGCB (ORCPT ); Tue, 31 Mar 2009 02:02:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758200AbZCaGBs (ORCPT ); Tue, 31 Mar 2009 02:01:48 -0400 Received: from brick.kernel.dk ([93.163.65.50]:34682 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755137AbZCaGBr (ORCPT ); Tue, 31 Mar 2009 02:01:47 -0400 Date: Tue, 31 Mar 2009 08:01:43 +0200 From: Jens Axboe To: Linus Torvalds Cc: Fernando Luis =?iso-8859-1?Q?V=E1zquez?= Cao , Jeff Garzik , Christoph Hellwig , Theodore Tso , Ingo Molnar , Alan Cox , Arjan van de Ven , Andrew Morton , Peter Zijlstra , Nick Piggin , David Rees , Jesper Krogh , Linux Kernel Mailing List , chris.mason@oracle.com, david@fromorbit.com, tj@kernel.org Subject: Re: [PATCH 1/7] block: Add block_flush_device() Message-ID: <20090331060143.GF5178@kernel.dk> References: <49D03377.1040909@oss.ntt.co.jp> <49D0B535.2010106@oss.ntt.co.jp> <49D0B687.1030407@oss.ntt.co.jp> <20090330175544.GX5178@kernel.dk> <20090330185414.GZ5178@kernel.dk> <20090330201732.GB5178@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 30 2009, Linus Torvalds wrote: > > > On Mon, 30 Mar 2009, Jens Axboe wrote: > > > > > > It has _nothing_ to do with 'reckless'. It has everything to do with 'you > > > can't do anything about it'. > > > > No, but you better damn well inform of such a discovery! > > Well, if that's the issue, then just add a printk to that > 'blkdev_issue_flush()', and now you have that informational message in > _one_ place, instead of havign each filesystem having to do it over and > over again. Right, that's exactly what I want :-) > > > No. Returning an error just means that now the box is useless. Nobody can > > > do anything about it. Not the admin, not the driver writer, not anybody. > > > > What, that's nonsense. The admin can certainly check whether it's an > > issue or not, and he should. > > If it's just informational, then again - why should the filesystem care? > > Returning an error to the caller is never the right thing to do. The > caller can't do anything sane about it. > > If you argue that the admin wants to know, then sure, make that > > if (bio_flagged(bio, BIO_EOPNOTSUPP)) > - ret = -EOPNOTSUPP; > + set_queue_noflush(q); > > "set_queue_noflush()" function print a warning message when it sets the > bit. > > Problem solved. > > > That's different from handling it in the kernel or in the application, > > but you have to inform about it. I honestly cannot fathom why you don't > > think that is important. > > I cannot fathom why you can _possibly_ think that this is something that > can and must be done something about in the caller. When the caller > obviously has no real option except to ignore the error _anyway_. > > That was always my point. Returning an error is INSANE, because ther is no > valid thing that the caller can possibly do. > > If you want it logged, fine. But THAT DOES NOT CHANGE ANYTHING. It would > still be wrong to return the error, since the caller _still_ can't do > anything about it. I don't want to return -EOPNOTSUPP, I think this thread has become increasingly confusing. And it's probably largely due to me mixing write barriers into it, if we stick purely to blkdev_issue_flush(), then logging a warning and returning 0 is perfectly fine with me. My objection was to ignoring the "I can't flush" error in the first place, not returning 0. -- Jens Axboe