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 X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0D84C1B08C for ; Thu, 15 Jul 2021 15:45:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C142B613D0 for ; Thu, 15 Jul 2021 15:45:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238465AbhGOPsa (ORCPT ); Thu, 15 Jul 2021 11:48:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42110 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238143AbhGOPsa (ORCPT ); Thu, 15 Jul 2021 11:48:30 -0400 Received: from fieldses.org (fieldses.org [IPv6:2600:3c00:e000:2f7::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 31629C06175F; Thu, 15 Jul 2021 08:45:37 -0700 (PDT) Received: by fieldses.org (Postfix, from userid 2815) id 033DF69D6; Thu, 15 Jul 2021 11:45:35 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.11.0 fieldses.org 033DF69D6 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fieldses.org; s=default; t=1626363935; bh=um4FevvC0GtfFwF+FGlJuSPjool50OiKU6H5RtnTrj8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cq6Lk/d7wbZIHoGu+OoGye3oJ6Xznfft79zYQYSSSG5phg6puHj0kc4NiV4Sih7m9 X/60woOWJiB9I4y5dm5YfuzFM8nntYI5827nVBgv7LDrwxb8c90x+LN7xONxbIW7Ts 72FXCcHiTqOddWmTZfB7VZDaLo2UQ2ZFhgVQR0lw= Date: Thu, 15 Jul 2021 11:45:34 -0400 From: "J. Bruce Fields" To: NeilBrown Cc: Chuck Lever , Chris Mason , Josef Bacik , David Sterba , linux-nfs@vger.kernel.org, Wang Yugui , Ulli Horlacher , linux-btrfs@vger.kernel.org Subject: Re: [PATCH/RFC] NFSD: handle BTRFS subvolumes better. Message-ID: <20210715154534.GA24492@fieldses.org> References: <20210613115313.BC59.409509F4@e16-tech.com> <20210310074620.GA2158@tik.uni-stuttgart.de> <162632387205.13764.6196748476850020429@noble.neil.brown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <162632387205.13764.6196748476850020429@noble.neil.brown.name> User-Agent: Mutt/1.5.21 (2010-09-15) Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Thu, Jul 15, 2021 at 02:37:52PM +1000, NeilBrown wrote: > To fix this, we need to report a different fsid for each subvolume, but > need to use the same fsid that we currently use for the top-level > volume. Changing this (by rebooting a server to new code), might > confuse the client. I don't think it would be a major problem (stale > filehandles shouldn't happen), but it is best avoided. ... > Again, we really want an API to get this from the filesystem. Changing > it later has no cost, so we don't need any commitment from the btrfs team > that this is what they will provide if/when we do get such an API. "No cost" makes me a little nervous, are we sure nobody will notice the mountd-on-fileid changing? Fileid and fsid changes I'd worry about more, though I wouldn't rule it out if that'd stand in the way of a bug fix. Thanks for looking into this. --b.