Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2992866AbbEPAKb (ORCPT ); Fri, 15 May 2015 20:10:31 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:58600 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2992574AbbEPAKa (ORCPT ); Fri, 15 May 2015 20:10:30 -0400 Date: Sat, 16 May 2015 01:10:27 +0100 From: Al Viro To: Dave Chinner Cc: Linus Torvalds , Linux Kernel Mailing List , linux-fsdevel , Christoph Hellwig , Neil Brown Subject: Re: [RFC][PATCHSET v3] non-recursive pathname resolution & RCU symlinks Message-ID: <20150516001027.GL7232@ZenIV.linux.org.uk> References: <20150505052205.GS889@ZenIV.linux.org.uk> <20150511180650.GA4147@ZenIV.linux.org.uk> <20150513222533.GA24192@ZenIV.linux.org.uk> <20150514033040.GF7232@ZenIV.linux.org.uk> <20150514112304.GT15721@dastard> <20150515233808.GH4316@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150515233808.GH4316@dastard> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1477 Lines: 30 On Sat, May 16, 2015 at 09:38:08AM +1000, Dave Chinner wrote: > > Both readdir() and path component lookup are technically read > > operations, so why the hell do we use a mutex, rather than just > > get a read-write lock for reading? Yeah, it's that (d) above. I > > might trust xfs and ext4 to get their internal exclusions for > > allocations etc right when called concurrently for the same > > directory. But the others? > > They just use a write lock for everything and *nothing changes* - > this is a simple problem to solve. > > The argument "filesystem developers are stupid" is not a > compelling argument against changing locking. You're just being > insulting, even though you probably don't realise it. Er... Remember the clusterfuck around the ->i_size and alignment checks on XFS DIO writes? Just this cycle. Correctness of XFS locking is nothing to boast about - it *is* convoluted as hell and you guys are not superhuman enough to reliably spot the problems in that nest of horrors. Nobody is. PS: I've no idea whether I'm being insulting or not and frankly, I don't give a damn; unlike Linus I hadn't signed off on the "code of conflict" nonsense. Anyone who feels like complaining is quite welcome to it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/