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[209.85.220.41]) by mx.google.com with SMTPS id t4sor1376159ywa.78.2019.02.06.12.02.52 for (Google Transport Security); Wed, 06 Feb 2019 12:02:52 -0800 (PST) Received-SPF: pass (google.com: domain of amir73il@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="dj/gJrDa"; spf=pass (google.com: domain of amir73il@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=amir73il@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com 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:content-transfer-encoding; bh=k0CqLn4RmwyP4v+EH3CC7Wy9XequpyzTFjmrIxpm28w=; b=dj/gJrDa8zw3vtVYnHJd/t+pYYFJQDxEXu4PjdcePhS7VBpCcJm8+upK6P941DgWvr QqiuHGezcDgQOUeZIFJmxqpif362kZ8leWojlB6bAxtC4RxYpUZZyET4osW8TEY2KLBc QJNd0D01wcMi9KbFhZKSUYA00IVE9jvDiP+HE2YYLZfNx7TB8rjeMTN71rZnaQ0kcstM rz8PdWsj6tr+jgXVgfDt+7kYnJI/APEIWiyZiwqJTObkLkgE6C7DRP4ceJM68LKzscIc +9adB4RS44yagYD1PSHJPx5MvAeoMXJYI3piRn0vzubv6YV1yXH9IPoMUb9SU6KgDlR2 2ExQ== X-Google-Smtp-Source: AHgI3IaBTPP//bgYeedw+uvGhvGlZhkhp40MfBbDsRSYtirCoaL3vAqqbCyHK036ef79w+N3U3HfEeROQZ9yuHYFenw= X-Received: by 2002:a81:274e:: with SMTP id n75mr10117588ywn.404.1549483372445; Wed, 06 Feb 2019 12:02:52 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Amir Goldstein Date: Wed, 6 Feb 2019 22:02:40 +0200 Message-ID: Subject: Re: [LSF/MM TOPIC] filesystem virtualization To: Miklos Szeredi Cc: lsf-pc@lists.linux-foundation.org, linux-fsdevel , Linux MM , Vivek Goyal , Stefan Hajnoczi , "Dr. David Alan Gilbert" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 Wed, Feb 6, 2019 at 3:06 PM Miklos Szeredi wrote: > > 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 There are some commonalities here with userspace networking file servers. I am interested in samba in particular and things that we can do to improve Linux interfaces for samba. SMB3 directory leases for example. Thanks, Amir. > - Multi-component path revalidation > > * Issues related to c/m/atime handling: > > - Clock synchronization between host and guest (not an fs issue, but f= s > 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); i= s > this design reasonable? > > - Avoids memory copies and cache duplication, but host page table setu= p > 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= /