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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06FCCE7F12C for ; Tue, 26 Sep 2023 21:36:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9172E6B014E; Tue, 26 Sep 2023 17:36:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8C7D26B014F; Tue, 26 Sep 2023 17:36:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 78F6F6B0150; Tue, 26 Sep 2023 17:36:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 691A46B014E for ; Tue, 26 Sep 2023 17:36:31 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 34BA8C06BE for ; Tue, 26 Sep 2023 21:36:31 +0000 (UTC) X-FDA: 81280057782.30.3E1EEC3 Received: from mail-yb1-f171.google.com (mail-yb1-f171.google.com [209.85.219.171]) by imf22.hostedemail.com (Postfix) with ESMTP id 6F048C000B for ; Tue, 26 Sep 2023 21:36:29 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=AjPLVbIS; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf22.hostedemail.com: domain of hughd@google.com designates 209.85.219.171 as permitted sender) smtp.mailfrom=hughd@google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1695764189; a=rsa-sha256; cv=none; b=F2y/1dIdeeBHIeXjZjBEmSVeOYXbow7sFYRQR6ITbQfDkTIbwAQuhKijPOkMkF5on7myFl PESVkIFZ2nL9gt5C7HY3yZEZ0jHYdPg89tBNvw9fBO+TsIGdY3EkpV0jA05snw827RlfeO SgxzDaOv1M2C3q+WpYZLBtDpzAzBsX0= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=AjPLVbIS; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf22.hostedemail.com: domain of hughd@google.com designates 209.85.219.171 as permitted sender) smtp.mailfrom=hughd@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1695764189; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=1MNbo8WjlIbk+vD57Y9Z/H6BU+dtLvsY8sTpvqB5nJI=; b=Y9+MoFOFu0w2e+6bV3EazbK+mE09QeDs3jYKK9EJSPHJvoGhqm901f2Z9U1zPLBiG+K/sL 2U+Oxrwg/UWNeb3sxTw3RA0cHpABdh3T93WMELP3oD82TcDZrX7Mtta/blH01TkgFBNhJ2 hTBx7urqhjHpqy+cp+wRHCObWe15j+U= Received: by mail-yb1-f171.google.com with SMTP id 3f1490d57ef6-d818d65f23cso11182840276.3 for ; Tue, 26 Sep 2023 14:36:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1695764188; x=1696368988; darn=kvack.org; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:from:to:cc:subject:date:message-id:reply-to; bh=1MNbo8WjlIbk+vD57Y9Z/H6BU+dtLvsY8sTpvqB5nJI=; b=AjPLVbISpGDYSYMk/2ajzQrZ7PpqpoSoaBTA4PNd+QTTCFTE03WhcPkmFT2K6MPi59 LAxoxAopO6MywWtqp4PTMZQHEZr/tmAOZFO4J71OO8PFaikwJV3DsRFi71+ju3If888W VcjODoNuCfAwzrRCzq5wvwYhi4xzlvhXRx1VOsop3AIv/2IR/LXOIQG+6eaHbuTxwkau LW5RZw6n6iKqXMUAxhXcPtmdWjSvNs0/KQJn27kOawq2FrB1LZI6a9MFs5KK0xuh6QmX NdMhTTbGaKq4wIlCKUkC37X2A3lpKQEtaVMnD4TcZCBFQbSPFdyDg7fKkm3Nm4OdLotp 2sCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695764188; x=1696368988; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=1MNbo8WjlIbk+vD57Y9Z/H6BU+dtLvsY8sTpvqB5nJI=; b=ku23CTFTsNFO2ICvoh5PL9MekUOUswtIO9bpRycvRKjxZw7BzOAuakCKOwgkpxm2Oh sEgKe11uswO3PCErHlhjDKc5VdJtHA3e4cMiIPQ9B42DolCpz5+MhhiZFwyXc8ZhKooN MKPXXAXZ4DjCIe0lYJL/BC/A6Jmd0T2N+kjz1NBVmaziPh5m6o1Pr78waO4ZKAxY95Ok 2NmZTG+5s27uIbsc5HlvpzHAJ5IXyl6wWJHXPcFwEapiWY0clgUwNozTFnJ8GC+OmU7q dGoMcoK46kqGgW3ZFTQiZppQRwmAuMS9UA7l7TFDSo7GRaBdqVyXvskwKvXGRbp0DpCt LGaw== X-Gm-Message-State: AOJu0YyqOVDS//9zpzHCDwI0l5um/inbfsHXwG45L6MjKmgwK/xthhym 6bfMT2jgeI4grCsjBbsuiRuacA== X-Google-Smtp-Source: AGHT+IELIOjIzVR9C4NP9eVufHE/iePU436e3hIzTZyc8ipuHsADk8UsXov3hJAz4eamwIw3djhY8Q== X-Received: by 2002:a81:a08c:0:b0:59b:e72a:e40b with SMTP id x134-20020a81a08c000000b0059be72ae40bmr278076ywg.6.1695764188458; Tue, 26 Sep 2023 14:36:28 -0700 (PDT) Received: from ripple.attlocal.net (172-10-233-147.lightspeed.sntcca.sbcglobal.net. [172.10.233.147]) by smtp.gmail.com with ESMTPSA id e11-20020a81690b000000b0059b20231f1dsm3258266ywc.121.2023.09.26.14.36.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Sep 2023 14:36:27 -0700 (PDT) Date: Tue, 26 Sep 2023 14:36:25 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Matthew Wilcox cc: Hugh Dickins , Andrew Morton , Andi Kleen , Christoph Lameter , Mike Kravetz , David Hildenbrand , Suren Baghdasaryan , Yang Shi , Sidhartha Kumar , Vishal Moola , Kefeng Wang , Greg Kroah-Hartman , Tejun Heo , Mel Gorman , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 07/12] mempolicy: mpol_shared_policy_init() without pseudo-vma In-Reply-To: Message-ID: <4fe84029-ad5-63cb-f2a7-3c83ea427bf1@google.com> References: <2d872cef-7787-a7ca-10e-9d45a64c80b4@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 6F048C000B X-Stat-Signature: k3groz77zyuh85iq3ku4jzej3pxhwkek X-HE-Tag: 1695764189-193886 X-HE-Meta: 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 a+1/ge3j 2NQju66QBecZteLs605NbtEVdYVGCZ4zH4TqeE2Yn+6AsDW8OQN0XQduffFJ6RTBNCwI/sAzcqyKtt6fH0Ng757hFnmi7/3wMw1BLv1zqQpjCs+7BOH4BbFpmdxZJSyz5mDY7Kl55ZY7w+wPeeuS5UW9pvCX2B/St7271iqO18nq8aveUiNAK3Z3C/Z1o//wdu2nYzv8X+kb3FaMOYCkj0rpikQPakWZBBQ0fyN+WSeXVV4yo9au7e9rNI+T8PBXiOxQKMb8L0+5or6bscGM1XP//40WpxR+iuNlTt5vGm79MsPqX328/NolvMSkzCedJQV92z0Yxpx2KtzMTpNZx1px6eBSmFpfJk4SIsuNOfrpcjOslIe+V2BE7yzCNF/VZsUBJRwJ4E3d9OqaQFVVVwrHBEG2O1h/jJJ7NjxvoaARoSlZSwsbXZZPwupzLqSqY75WdetpWaXYhBGcM/P+1lgmZhVQmOQNKv7b2 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 25 Sep 2023, Matthew Wilcox wrote: > On Mon, Sep 25, 2023 at 01:29:28AM -0700, Hugh Dickins wrote: > > + /* alloc node covering entire file; adds ref to new */ > > This comment is confusing. sp_alloc initialises the refcount of 'n' to 1. > Which is the same memory referred to by the name 'new' in __mpol_dup(), > but in this function, the name "new" refers to the mempolicy called > "old" in __mpol_dup(). No promises, but I'll see if I can make it look better in v2. > > > + n = sp_alloc(0, MAX_LFS_FILESIZE >> PAGE_SHIFT, new); > > + if (n) > > + sp_insert(sp, n); > > put_new: > > mpol_put(new); /* drop initial ref */ > > free_scratch: > > This is all a bit inefficient, really. We call mpol_new() to get a > new mpol, then we set it up, then we dup it, then we free it. It'd > be nice if we could donate it instead of copying it. Maybe you'll > do something like that later. "later" is probably the operative word. I do have an unincluded 2017 patch where I had that same realization, and wrote "I suspect that this series of commits may be adding to an absurdity of over-mpol_dup()ing: but that's for some other future cleanup, right now I'm just happy not to be corrupting or leaking mpols." Hugh