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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 B824EC433E0 for ; Mon, 15 Feb 2021 18:08:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9383864DA5 for ; Mon, 15 Feb 2021 18:08:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230186AbhBOSIa (ORCPT ); Mon, 15 Feb 2021 13:08:30 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:39416 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229991AbhBOSI1 (ORCPT ); Mon, 15 Feb 2021 13:08:27 -0500 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1lBiHh-00Exml-2G; Mon, 15 Feb 2021 11:07:45 -0700 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=fess.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1lBiHd-00Go0X-HA; Mon, 15 Feb 2021 11:07:44 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: Linus Torvalds Cc: Jens Axboe , linux-fsdevel , Al Viro References: <20201214191323.173773-1-axboe@kernel.dk> <94731b5a-a83e-91b5-bc6c-6fd4aaacb704@kernel.dk> Date: Mon, 15 Feb 2021 12:07:22 -0600 In-Reply-To: (Linus Torvalds's message of "Sun, 14 Feb 2021 12:30:07 -0800") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1lBiHd-00Go0X-HA;;;mid=;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1+kYEmN5PJD2f9ePzeREqnaiJQOPqGTsa4= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCHSET v3 0/4] fs: Support for LOOKUP_NONBLOCK / RESOLVE_NONBLOCK (Insufficiently faking current?) X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Linus Torvalds writes: > On Sun, Feb 14, 2021 at 8:38 AM Jens Axboe wrote: >> >> > Similarly it looks like opening of "/dev/tty" fails to >> > return the tty of the caller but instead fails because >> > io-wq threads don't have a tty. >> >> I've got a patch queued up for 5.12 that clears ->fs and ->files for the >> thread if not explicitly inherited, and I'm working on similarly >> proactively catching these cases that could potentially be problematic. > > Well, the /dev/tty case still needs fixing somehow. > > Opening /dev/tty actually depends on current->signal, and if it is > NULL it will fall back on the first VT console instead (I think). > > I wonder if it should do the same thing /proc/self does.. Would there be any downside of making the io-wq kernel threads be per process instead of per user? I can see a lower probability of a thread already existing. Are there other downsides I am missing? The upside would be that all of the issues of have we copied enough should go away, as the io-wq thread would then behave like another user space thread. To handle posix setresuid() and friends it looks like current_cred would need to be copied but I can't think of anything else. Right I am with Al and I don't have any idea how many special cases we need to play whack-a-mole with. Eric