From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Cox Subject: Re: [PATCH] [8/18] BKL-removal: Remove BKL from remote_llseek Date: Mon, 28 Jan 2008 14:50:47 +0000 Message-ID: <20080128145047.1b40655d@core> References: <20080127317.043953000@suse.de> <200801281427.36048.ak@suse.de> <20080128133857.6c53ac9f@core> <200801281510.35200.ak@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Andrew Morton , Trond Myklebust , Steve French , swhiteho@redhat.com, sfrench@samba.org, vandrove@vc.cvut.cz, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Andi Kleen Return-path: Received: from outpipe-village-512-1.bc.nu ([81.2.110.250]:40733 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752799AbYA1Ozo (ORCPT ); Mon, 28 Jan 2008 09:55:44 -0500 In-Reply-To: <200801281510.35200.ak@suse.de> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, 28 Jan 2008 15:10:34 +0100 Andi Kleen wrote: > On Monday 28 January 2008 14:38:57 Alan Cox wrote: > > > Also worse really fixing it would be a major change to the VFS > > > because of the way ->read/write are defined :/ > > > > I don't see a problem there. ->read and ->write update the passed pointer > > which is not the real f_pos anyway. Just the copies need fixing. > > They are effectually doing a decoupled read/modify/write cycle. e.g.: > > A B > > read fpos > > read fpos > > fpos += A fpos += B > write fpos > > > write fpos > > So you get overlapping reads. Probably not good. No unix system I'm aware of cares about the read/write positioning during parallel simultaneous reads or writes, with the exception of O_APPEND which is strictly defined. The problem case is getting fpos != either valid value.