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[2620:137:e000::1:20]) by mx.google.com with ESMTP id i12-20020a63130c000000b004fc39adf481si3812994pgl.381.2023.04.13.21.08.33; Thu, 13 Apr 2023 21:08:55 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linux.org.uk header.s=zeniv-20220401 header.b=J1uqK7jB; spf=pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-nfs-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=zeniv.linux.org.uk Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229449AbjDNDvb (ORCPT + 99 others); Thu, 13 Apr 2023 23:51:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50840 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229540AbjDNDvO (ORCPT ); Thu, 13 Apr 2023 23:51:14 -0400 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [IPv6:2a03:a000:7:0:5054:ff:fe1c:15ff]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51ED24EDC; Thu, 13 Apr 2023 20:51:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=A5unxLUF/trhWh4az7FEFonxncdYDeRL1VTUQkMbeug=; b=J1uqK7jB8dgmSMMXL4PGfK/Hdq v14gCrD6dOrwQsq4DzOhUuaRepU392hyDjLtMcC784AMioXrn7t4UiiWbWL9vo8vIko77DTeY+Iyf oYbosxXTI7XDPRy3rWNrE9LSFvncCY8LXi+1QZQDeWYlS7ARkKXVXoeN0VAaUm1aWwIZzPcaNmESM 2tEl2gzFrC8dNA/T57FM3fDOEEh9CN58iR13n+a3aFfwM6WKb61R0GpJM6lDBNGFrhZWry7nCihqG dNoUEPO6hKeH7rV059dxR81JUpYi88fe2+waaPvZ17ocFJWSG3NOGd/u6TsIXl99KiH5PNiY0GgUv rJ360xOw==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.96 #2 (Red Hat Linux)) id 1pnASm-008q23-29; Fri, 14 Apr 2023 03:51:04 +0000 Date: Fri, 14 Apr 2023 04:51:04 +0100 From: Al Viro To: Trond Myklebust Cc: Neil Brown , Jeffrey Layton , Christian Brauner , Dave Wysochanski , linux-fsdevel , linux-nfs , David Howells , Christoph Hellwig Subject: Re: allowing for a completely cached umount(2) pathwalk Message-ID: <20230414035104.GH3390869@ZenIV> References: <95ee689c76bf034fa2fe9fade0bccdb311f3a04f.camel@kernel.org> <168142566371.24821.15867603327393356000@noble.neil.brown.name> <20230414024312.GF3390869@ZenIV> <8EC5C625-ACD6-4BA0-A190-21A73CCBAC34@hammerspace.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8EC5C625-ACD6-4BA0-A190-21A73CCBAC34@hammerspace.com> Sender: Al Viro X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Fri, Apr 14, 2023 at 03:28:45AM +0000, Trond Myklebust wrote: > We already have support for directory file descriptors when mounting with move_mount(). Why not add a umountat() with similar support for the unmount side? > Then add a syscall to allow users with (e.g.) the CAP_DAC_OVERRIDE privilege to convert the mount-id into an O_PATH file descriptor. You can already do umount -l /proc/self/fd/69 if you have a descriptor. Converting mount-id to O_PATH... might be an interesting idea.