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=-3.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 8D043C433DF for ; Mon, 15 Jun 2020 10:05:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 681E0206B7 for ; Mon, 15 Jun 2020 10:05:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Rm9uZHQ6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729551AbgFOKFW (ORCPT ); Mon, 15 Jun 2020 06:05:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53504 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726111AbgFOKFU (ORCPT ); Mon, 15 Jun 2020 06:05:20 -0400 Received: from mail-io1-xd44.google.com (mail-io1-xd44.google.com [IPv6:2607:f8b0:4864:20::d44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5820CC061A0E; Mon, 15 Jun 2020 03:05:20 -0700 (PDT) Received: by mail-io1-xd44.google.com with SMTP id p20so17105775iop.11; Mon, 15 Jun 2020 03:05:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=dfs5PllpQpG9QpYkVZTr5YGvpGpnNGmZTQiHA7UaSnw=; b=Rm9uZHQ6qwXtdXIirn2i9Fii8ebIQCWolZpKBzlXT7okYU7u/azWvU+8b7sqW/YcUW ueDgXdICoowFfocCx2+bP5cZxxiTGZtoFD3Rj8MxuHhfGVMxP7A/5vZklUxUQWT6aBk7 NHE4H4ZlKtqPC6AAfiJIFbn2Hu3ZCcHe509LrqUtQkVMKdzYbtP5q06WyV53SY4sM1Qb JBGM/6CD86ycKuf94WO1HOtOjPs5KHWV4GLz3kfw3sSWOALL1SZWpfEKCo/5LnkgNRvw yPJKX2c6g34XP6ZRPKLvPGsaYZiUQt7NoWsovDir5xdi39QJv9qax/GvJ2byOJbpoh1j R9Dg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=dfs5PllpQpG9QpYkVZTr5YGvpGpnNGmZTQiHA7UaSnw=; b=ZCG6wxvHKYa0FlJEsBekRj4kPd4tHv+NqTmh4PnFRGxvu7z7qpThI0chDLih0rrnTP kDyf2GTQzCKDjICc6vG98Aw3uZQSoKrD33IKVanphAOu38QJNO5STKupfofE6sBq7qqk mwDr0excSEMmd1LKOAaAf+rGTi6krek/wjq32Blkn0bGfdj+q067PeUMRfLSQO5CE1ge 8uhwFXFRdXMmpnWyZtfFhJjGwlHYWI8MYMWY+WxNP+bkMpjksKtIJXQRX6OPxijAgraZ rM1XXYJ0bZ3DeUlLe/BdSW8QBwd6Cd2z6fFO2jaL7z7XC/evTdyzoc1PGLdzuADUlYiC vuvA== X-Gm-Message-State: AOAM532IBfPHP9PCrYt/i6OCa7d38JaRrSBcFtJUGLZwdQTQuVfR3D2X 6r9saIUm7rBc6NOoT8XgqTE64iVq8b+HEDqDa5c= X-Google-Smtp-Source: ABdhPJw2ZNSatUBV5nkdNWJB5epCtTEMUWyTNWezAfi/r72JR+OKrJKz92f3vb55u1hjxnOO0jazboJ+w2X3EnzYQqk= X-Received: by 2002:a05:6638:d96:: with SMTP id l22mr21113713jaj.120.1592215519677; Mon, 15 Jun 2020 03:05:19 -0700 (PDT) MIME-Version: 1.0 References: <20200612004644.255692-1-mike.kravetz@oracle.com> <20200612015842.GC23230@ZenIV.linux.org.uk> <6e8924b0-bfc4-eaf5-1775-54f506cdf623@oracle.com> In-Reply-To: From: Amir Goldstein Date: Mon, 15 Jun 2020 13:05:08 +0300 Message-ID: Subject: Re: [PATCH v4 1/2] hugetlb: use f_mode & FMODE_HUGETLBFS to identify hugetlbfs files To: Miklos Szeredi Cc: Mike Kravetz , Al Viro , Linux MM , linux-fsdevel , overlayfs , linux-kernel , Matthew Wilcox , Colin Walters , Andrew Morton , syzbot , syzkaller-bugs Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 15, 2020 at 10:53 AM Miklos Szeredi wrote: > > On Sat, Jun 13, 2020 at 9:12 PM Mike Kravetz wrote: > > > > On 6/12/20 11:53 PM, Amir Goldstein wrote: > > > As a hugetlbfs developer, I do not know of a use case for interoperability > > with overlayfs. So yes, I am not too interested in making them work well > > together. However, if there was an actual use case I would be more than > > happy to consider doing the work. Just hate to put effort into fixing up > > two 'special' filesystems for functionality that may not be used. > > > > I can't speak for overlayfs developers. > > As I said, I only know of tmpfs being upper layer as a valid use case. > Does that work with hugepages? How would I go about testing that? Simple, after enabling CONFIG_HUGETLBFS: diff --git a/mount_union.py b/mount_union.py index fae8899..4070c70 100644 --- a/mount_union.py +++ b/mount_union.py @@ -15,7 +15,7 @@ def mount_union(ctx): snapshot_mntroot = cfg.snapshot_mntroot() if cfg.should_mount_upper(): system("mount " + upper_mntroot + " 2>/dev/null" - " || mount -t tmpfs upper_layer " + upper_mntroot) + " || mount -t hugetlbfs upper_layer " + upper_mntroot) layer_mntroot = upper_mntroot + "/" + ctx.curr_layer() upperdir = layer_mntroot + "/u" workdir = layer_mntroot + "/w" It fails colossally, because hugetlbfs, does not have write_iter(). It is only meant as an interface to create named maps of huge pages. So I don't really see the use case for using it as upper. Thanks, Amir.