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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 F0A5CC33C9E for ; Tue, 14 Jan 2020 18:59:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CC9E624655 for ; Tue, 14 Jan 2020 18:59:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579028389; bh=+/letKJ2R7JqB8fztNDvcbdj3Rb7Mbv1rNUQoK8f+4k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=fY5dGFA2rDExyd93mulo6rzGRGNEH1GXQMP7M8k2kMKRtoey99cdschlJIHArewD6 GLkpWfTROMcZwxNmS8TVExYQ163CBLydsGu1UC3Kdj+OWh/HGFpXYhTslQx/vR0qDs uWOEi37hc6l7QfR8BSykjZHI3Ut6YOe2Dvigz7Dc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728708AbgANS7t (ORCPT ); Tue, 14 Jan 2020 13:59:49 -0500 Received: from mail-pg1-f193.google.com ([209.85.215.193]:45355 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726450AbgANS7s (ORCPT ); Tue, 14 Jan 2020 13:59:48 -0500 Received: by mail-pg1-f193.google.com with SMTP id b9so6794042pgk.12; Tue, 14 Jan 2020 10:59:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=ZLdWsGP0XHWGCxqVZhBLWctk+c6rDeF6k4vcD9DPHeI=; b=i2esJgOGFaemeAJAp/5QuOJMkYpdkKC+BLVc3D4N2IEPIwfcCJcCSPc/Rp3CxvQcSX 8kRFU0HiBO9tAtgVGddZGvBf66yxgIoiUP2gAFr9YIvFs3e1tJCgnaRRF3+HT3F6hCVX HQUUXaaol4cLeN7aKj8yFkgcOpznc1FoOoXd6AeqMXb4zSwz+GxGgcMO6ULnsUFnZfTQ +uWHsyf5dvD13xhpYMo/FUR/Rs3U11m8KLSDY1X1u9UZAfhcWHvVfUfIqeJXH4qpKJlE eZubYzsEvAnrRoY2zi3DmJb8WFDVO05RQQDJ1WGC8Lz+Fj0k2Jc/8s24Ix0/pXV9Txhr WSwQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=ZLdWsGP0XHWGCxqVZhBLWctk+c6rDeF6k4vcD9DPHeI=; b=ovedxxpPXWGQvjcoTKshv6FTrNjOdkkdtPvUhdz7a2mDUPHojs3o/PvhIrF2rl+BZn M/GavCm/LOdmmmsViPo1MG7xJ5Gge6dNZTA9QeQEy932gDu11//qWTRQQJFmqrvKGsvr twb/eIs0JGB+/96RyTpMIUxk5OXQZ7PrS1osa+e+W3mB1YeIWQxqpF6wHgfbqTStVuxt b0Qf6B299mfGIPBkDRc3mYtz64UxqZpjme496qRPttpqcOiR4BWStzoCAEfKkDDDIqAJ dDy+BoAftl4OMqsfGgUkbjV7D+abmPZxGnPL7+1tgE85lR2DoD4O7Hq+RhqIUUEPwu0F VGzw== X-Gm-Message-State: APjAAAWjESv2HwnwR2JTJq8gF3kZh8ZpeUhWcWtEf24erj2FcCgzo8Zt 0M5eX7BkpjNdamfO4ebRl/A= X-Google-Smtp-Source: APXvYqy/N+z69PG6y7Ebj6znXULG+UpZs19rlNT7fvG0Mt2TmO28ChC4a53hBPhfkDlB2m58VsHirQ== X-Received: by 2002:a63:ed56:: with SMTP id m22mr28041543pgk.261.1579028387395; Tue, 14 Jan 2020 10:59:47 -0800 (PST) Received: from google.com ([2620:15c:211:1:3e01:2939:5992:52da]) by smtp.gmail.com with ESMTPSA id b4sm19392543pfd.18.2020.01.14.10.59.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Jan 2020 10:59:46 -0800 (PST) Date: Tue, 14 Jan 2020 10:59:44 -0800 From: Minchan Kim To: Christian Brauner Cc: Kirill Tkhai , Michal Hocko , Andrew Morton , LKML , linux-mm , linux-api@vger.kernel.org, oleksandr@redhat.com, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Johannes Weiner , Shakeel Butt , John Dias Subject: Re: [PATCH 2/4] mm: introduce external memory hinting API Message-ID: <20200114185944.GA178589@google.com> References: <20200110213433.94739-1-minchan@kernel.org> <20200110213433.94739-3-minchan@kernel.org> <56ea0927-ad2e-3fbd-3366-3813330f6cec@virtuozzo.com> <20200113104256.5ujbplyec2sk4onn@wittgenstein> <20200113184408.GD110363@google.com> <20200113191046.2tidyvc544zvchek@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200113191046.2tidyvc544zvchek@wittgenstein> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Christian, On Mon, Jan 13, 2020 at 08:10:47PM +0100, Christian Brauner wrote: > On Mon, Jan 13, 2020 at 10:44:08AM -0800, Minchan Kim wrote: > > On Mon, Jan 13, 2020 at 11:42:57AM +0100, Christian Brauner wrote: > > > On Mon, Jan 13, 2020 at 11:47:11AM +0300, Kirill Tkhai wrote: > > > > < snip > > > > > > > > +SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start, > > > > > + size_t, len_in, int, behavior, unsigned long, flags) > > > > > > > > I don't like the interface. The fact we have pidfd does not mean, > > > > we have to use it for new syscalls always. A user may want to set > > > > madvise for specific pid from console and pass pid as argument. > > > > pidfd would be an overkill in this case. > > > > We usually call "kill -9 pid" from console. Why shouldn't process_madvise() > > > > allow this? > > > > > > > > I suggent to extend first argument to work with both pid and pidfd. > > > > Look at what we have for waitid(idtype, id_t id, ...) for example: > > > > > > > > idtype == P_PID > > > > Wait for the child whose process ID matches id. > > > > > > > > idtype == P_PIDFD (since Linux 5.4) > > > > Wait for the child referred to by the PID file descriptor specified in id. (See pidfd_open(2) for further information on > > > > PID file descriptors.) > > > > > > > > We may use @flags argument for this. > > > > > > Sorry for chiming in just a comment. Overall, I don't particularly care > > > how or if you integrate pidfd here. One thing I would like to point out > > > is that we're working on a patch to place new features under pidfd > > > specific flags. This e.g. means a pidfd would be only be able to be used > > > for madvise operations (or getfd operations) if it was created with that > > > specific flag set making it easier to share them with other processes. > > > So if you integrate them here I would be quite thankful if you target > > > the patchset for the v5.7 merge window, not for v5.6. > > > > Hi Christian, > > Sorry but I couldn't understand your point. > > Could you clarify what you meant? > > Hi Minchan, > > Sure. When you create a pidfd, e.g. with clone3() and you'd wanted to > use it for madvise you'd need to set a flag like pidfd_cap_madvise or > pidfd_feature_madvise when you create the pidfd. Only if the pidfd was > created with that flag set could you use it with madvise (This does not > affect the permission checking you're performing here.). This has come > up a couple of times and becomes more relevant now that people keep > adding new features on top of pidfd and is similar to what we are now > doing with openat2(). Thanks for the explain. When I read discussion with you and Daniel, it's still vague for me that what's the outcome so that it could land onto v5.6.(If I miss something progress on other thread, sorry about that.) I will keep Ccing you so that you may notice when this patchset could be merged(Please Cc me when you send your patchset for me to notice) So if we judge it's worth to integrate, maybe we could make a quick patch to use it or postpone a cycle to intergrate it if we have more time. Thanks.