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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 7F09BC433DF for ; Fri, 22 May 2020 17:02:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4D0712078D for ; Fri, 22 May 2020 17:02:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="n98JT5//" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730720AbgEVRCv (ORCPT ); Fri, 22 May 2020 13:02:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49592 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730665AbgEVRCv (ORCPT ); Fri, 22 May 2020 13:02:51 -0400 Received: from mail-io1-xd42.google.com (mail-io1-xd42.google.com [IPv6:2607:f8b0:4864:20::d42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 52D6EC061A0E; Fri, 22 May 2020 10:02:50 -0700 (PDT) Received: by mail-io1-xd42.google.com with SMTP id q8so10686373iow.7; Fri, 22 May 2020 10:02:50 -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=5oEjRlutZgesjZsBZiS7Pr4cJPVCPyetipAJ+rscTg4=; b=n98JT5//RP8Wvyu9VLvSNejJOq74cqmdRu2GtXGCOZw+Jr0LyauRuu5OQV6CGUdNNi 2DP0kjZCfNmTSf0pVZX1WCu5QIeTytgjkIZV3zJBapZCr5koWfmnPKoS+OH+nxl+Wp4t dxXL18qA4DRC+/9/9hKNPyzbz0syZ/eNn5KLQwLs3qAOE9rGdHNohtNLzMtO8L5WTWSJ kz8/scjklAb/6U91mL6ktfl3bgFvznonDRAem3LXoeZhLJq0Rc1XXL5aJVe05DghWd2+ 3YMOMX7RtUB9cp02VYmWO7ju0Z1h8aUJpEco4aOOCyXyjKmudu6sDy8vW1AKZlnScn4q 4/AA== 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=5oEjRlutZgesjZsBZiS7Pr4cJPVCPyetipAJ+rscTg4=; b=IS2Yrb4rFMGQGlbX7/EdAX9K7/DX8OASwdA1V+v/rYH0QLKOXeO4KuVMeQE9N/com5 yGnrVjFXFTS/nSsDvZhObnpnVM3VxJBs7ITEN8X0jJBWR5932FowetcxTYWgu0mSqK2a YVUzEBGdy+8E2EN/LTHojjCK/uBvjnNSZABpkzPtFS1tgLEyk+DbwSOQtzHL5AVatGwH Ufk56jx1gSGQe5Vosi0f+wP8klN8FWLyb2+HGF8voBL+5Pr68x03xMJwlj07iN5OOEXe sZAk3ncp1jvgR3rsmc5B0o2GZBffCM2kbdXhid4uGsw5SFsI+D9rhFEP8XFT4LBcwhk1 NUtw== X-Gm-Message-State: AOAM532d7I2vRWnws7XtEA9P1O9NLok+CH3TQEquy0m8ZRzLLWlPcQ8w t7NmcqHwjPXf15ve9Ct91xpdcioNDJaqgKMxZ4xxClre X-Google-Smtp-Source: ABdhPJzGYyiIz9HHCDTTzCDAm4IA7auea9SQSZM9H0EeTh377b4cTFqNt1IwzJLGdNzH58gNtehDSupkPPwT20xJQHU= X-Received: by 2002:a5e:840d:: with SMTP id h13mr3873782ioj.64.1590166969578; Fri, 22 May 2020 10:02:49 -0700 (PDT) MIME-Version: 1.0 References: <20200522085723.29007-1-mszeredi@redhat.com> <20200522160815.GT23230@ZenIV.linux.org.uk> In-Reply-To: From: Amir Goldstein Date: Fri, 22 May 2020 20:02:37 +0300 Message-ID: Subject: Re: [PATCH] ovl: make private mounts longterm To: Miklos Szeredi Cc: Al Viro , overlayfs , linux-fsdevel , lkml Content-Type: text/plain; charset="UTF-8" Sender: linux-unionfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org > > > - mntput(ofs->upper_mnt); > > > - for (i = 1; i < ofs->numlayer; i++) { > > > - iput(ofs->layers[i].trap); > > > - mntput(ofs->layers[i].mnt); > > > + > > > + if (!ofs->layers) { > > > + /* Deal with partial setup */ > > > + kern_unmount(ofs->upper_mnt); > > > + } else { > > > + /* Hack! Reuse ofs->layers as a mounts array */ > > > + struct vfsmount **mounts = (struct vfsmount **) ofs->layers; > > > + > > > + for (i = 0; i < ofs->numlayer; i++) { > > > + iput(ofs->layers[i].trap); > > > + mounts[i] = ofs->layers[i].mnt; > > > + } > > > + kern_unmount_many(mounts, ofs->numlayer); > > > + kfree(ofs->layers); > > > > That's _way_ too subtle. AFAICS, you rely upon ->upper_mnt == ->layers[0].mnt, > > ->layers[0].trap == NULL, without even mentioning that. And the hack you do > > mention... Yecchhh... How many layers are possible, again? > > 500, mounts array would fit inside a page and a page can be allocated > with __GFP_NOFAIL. But why bother? It's not all that bad, is it? FWIW, it seems fine to me. We can transfer the reference from upperdir_trap to layers[0].trap when initializing layers[0] for the sake of clarity. Thanks, Amir.