From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40280C433EF for ; Wed, 20 Jul 2022 15:23:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241302AbiGTPXN (ORCPT ); Wed, 20 Jul 2022 11:23:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232825AbiGTPXG (ORCPT ); Wed, 20 Jul 2022 11:23:06 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 50F855C94E for ; Wed, 20 Jul 2022 08:23:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1658330584; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=KUcxIoB2J7OZSdoCp00xQlFV5PxUPCmzZjIlgAQpABg=; b=fUvzYkgk23cyN7Bv3up2RpfOnbhvTZueJfjvkdkzKTgy2La5CSJFEYUUyj3QRGyvh5tvWw R+OBq2w6hTaeUqKwaHq4VYUnBsKyCmPbWV8aNznON5EArjnMn4o8H5OEELyLCArIAXpO2p D1IzFxdvvyJgttuxAZLNW0CeANbMcVQ= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-593-NSpBIl2VOkWCl7pVBu4WtA-1; Wed, 20 Jul 2022 11:23:01 -0400 X-MC-Unique: NSpBIl2VOkWCl7pVBu4WtA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 508538F3EE0; Wed, 20 Jul 2022 15:23:00 +0000 (UTC) Received: from fedora (unknown [10.40.194.108]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 419AE1121314; Wed, 20 Jul 2022 15:22:59 +0000 (UTC) Date: Wed, 20 Jul 2022 17:22:57 +0200 From: Lukas Czerner To: Jeff Layton Cc: tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-fsdevel , Benjamin Coddington Subject: Re: should we make "-o iversion" the default on ext4 ? Message-ID: <20220720152257.t67grnm4wdi3dpld@fedora> References: <69ac1d3ef0f63b309204a570ef4922d2684ed7f9.camel@kernel.org> <20220720141546.46l2d7bxwukjhtl7@fedora> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, Jul 20, 2022 at 10:38:31AM -0400, Jeff Layton wrote: > On Wed, 2022-07-20 at 16:15 +0200, Lukas Czerner wrote: --snip-- > > How would we approach making iversion a default? libmount is passing > > this option to the kernel as just a MS_I_VERSION flag that is set when > > -o iversion is used and left empty when the -o noiversion is used. This > > means that while we could make it a default in ext4, we don't have any > > way of knowing whether the user asked for -o noiversion. So that's not > > really an option. > > > > Updating the mke2fs/tune2fs to allow setting iversion as a default mount > > option I think has the same problem. > > > > So the only way I can see ATM would be to introduce another mountflag > > for libmount to indicate -o noiversion. This way we can make iversion a > > default on ext4 without loosing the information about user provided -o > > noiversion option. > > > > Is there a different way I am not seeing? > > > > Right, implementing this is the difficult bit actually since this uses a > MS_* flag. If we do make this the default, we'd definitely want to > continue allowing "-o noiversion" to disable it. > > Could we just reverse the default in libmount? It might cause this to > suddenly be enabled in some deployments, but in most cases, people > wouldn't even notice and they could still specify -o noiversion to turn > it off. Can be done, but that would change the default for everyone. Not sure if that desirable. Also I can image this being a bit confusing. I still think the best approach would be to introduce another MS_ flag for noiversion case. I think there is precedence in the case of MS_STRICTATIME - not exactly the same but similar enough. > Another idea would be to introduce new mount options for this, but > that's kind of nasty from a UI standpoint. > > > > > If we can do reasonably extensive testing that will indeed show > > negligible impact when nothing is querying i_version, then I would be in > > favor of the change. > > > > Excellent! I think that would be best if we can get away with it. A lot > of people are currently running ext4-backed nfs servers and aren't using > that mount option. Could you provide some performance numbers for iversion case? Thanks! -Lukas > -- > Jeff Layton >