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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 12CCCC169C4 for ; Wed, 6 Feb 2019 13:00:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCDCE2175B for ; Wed, 6 Feb 2019 13:00:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=szeredi.hu header.i=@szeredi.hu header.b="ECTFOsBk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728018AbfBFNAs (ORCPT ); Wed, 6 Feb 2019 08:00:48 -0500 Received: from mail-it1-f193.google.com ([209.85.166.193]:55255 "EHLO mail-it1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726598AbfBFNAr (ORCPT ); Wed, 6 Feb 2019 08:00:47 -0500 Received: by mail-it1-f193.google.com with SMTP id i145so6024770ita.4 for ; Wed, 06 Feb 2019 05:00:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:from:date:message-id:subject:to:cc :content-transfer-encoding; bh=fOIQJZI5ixQwS/lmnoBCYM2uMl/vkq4KxqXJU++gt3U=; b=ECTFOsBkpy73B8UftN2IbIv75uXdlaVeKOnc3zYw/tqRhDaD7/O8CAREku75naTBRa 0C+V7FyVxsXlT2mTIhkIYIwK7+jLaRIc2LBxIL5fWAVnIl+GV0r8gtyL0JRt0f0rrQC0 +NS0IbKnAeGKpn59wi5a6cHaHgT7yeOGRz+hc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to:cc :content-transfer-encoding; bh=fOIQJZI5ixQwS/lmnoBCYM2uMl/vkq4KxqXJU++gt3U=; b=MdbEPxFtT7EbI3QKxMkZYU/CUckWUqwda02VlEulWRpVWbEQ2jjlGi1kuI1p1gmkYC 2TpS9iiK7Lf6MW5EwEn4BPdHei2lWi97MkM+LnH3Pb+68bJi5qGrjgZOrQ+jRyrrpjVx dbZnc0/x9B54wCwAaDPeY0AGOJMj/XjLtYbQt3C4aDbJtM9BUZVBa+kqSpEO31h3hyK4 A6Gr+CyYbJrh0lIPsoYT6oUPY+o5Mt40Vxvk7Qf6U5pfzA4FPceIbDqJgwUn9lwJ/Xxw EKprlm4prF0ZnMOjcCPKoVDaMxpbnmhtfev6Z+9To0ObJ7MpO86U+1s2TzzcvvxYCDHs rXeA== X-Gm-Message-State: AHQUAuahekT+8hAstPpioEKaEPQtUkzThzGiKJwE5ns8hCrNAvdKQ5P1 zkordPxvGwGOgOIjS22+XgKnsCKTCgB6yKd4pbVqaw== X-Google-Smtp-Source: AHgI3Iavku+34l9vp8gYIesHqSALvNmE/GBbVmEjNjRvFj+8QeGoS/qkh4yFScCgAMrZ6N5iOxOiRXQJY8pcO75c9Dw= X-Received: by 2002:a6b:e506:: with SMTP id y6mr176263ioc.246.1549458046738; Wed, 06 Feb 2019 05:00:46 -0800 (PST) MIME-Version: 1.0 From: Miklos Szeredi Date: Wed, 6 Feb 2019 14:00:35 +0100 Message-ID: Subject: [LSF/MM TOPIC] filesystem virtualization To: lsf-pc@lists.linux-foundation.org Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Vivek Goyal , Stefan Hajnoczi , "Dr. David Alan Gilbert" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org This is a joint topic proposal with Vivek Goyal. Discuss remaining issues related to exporting a filesystem from host to guest (see virtio-fs prototype posting[1] for more background): * How to provide strong coherency guarantees? - Fsnotify synchronous post op notification - Extend lease (delegation) API to userspace - Multi-component path revalidation * Issues related to c/m/atime handling: - Clock synchronization between host and guest (not an fs issue, but fs has to deal with lack of it) - Could we have O_NOCMTIME open flag? * Shared access to file data: - Use DAX in guest to access host page cache (mmap/munmap sections of file in guest address space; happens dynamically on a need basis); is this design reasonable? - Avoids memory copies and cache duplication, but host page table setup may have high cost. Can that be improved? (E.g. fault-ahead) - Too many VMA=E2=80=99s on host per qemu instance? * File locking: - Host API for POSIX lock sharing? * Ideas for the future: - Buffering directory operations (e.g. "tar xfz ..." with as few synchronous ops as possible) [1] https://lore.kernel.org/lkml/20181210171318.16998-1-vgoyal@redhat.com/