From: Miklos Szeredi <miklos@szeredi.hu>
To: Greg Kurz <groug@kaod.org>
Cc: virtualization@lists.linux-foundation.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
virtio-fs-list <virtio-fs@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Max Reitz <mreitz@redhat.com>, Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH v4 4/5] virtiofs: Skip submounts in sget_fc()
Date: Fri, 21 May 2021 10:26:27 +0200 [thread overview]
Message-ID: <CAJfpegugQM-ChaGiLyfPkbFr9c=_BiOBQkJTeEz5yN0ujO_O4A@mail.gmail.com> (raw)
In-Reply-To: <20210520154654.1791183-5-groug@kaod.org>
On Thu, 20 May 2021 at 17:47, Greg Kurz <groug@kaod.org> wrote:
>
> All submounts share the same virtio-fs device instance as the root
> mount. If the same virtiofs filesystem is mounted again, sget_fc()
> is likely to pick up any of these submounts and reuse it instead of
> the root mount.
>
> On the server side:
>
> # mkdir ${some_dir}
> # mkdir ${some_dir}/mnt1
> # mount -t tmpfs none ${some_dir}/mnt1
> # touch ${some_dir}/mnt1/THIS_IS_MNT1
> # mkdir ${some_dir}/mnt2
> # mount -t tmpfs none ${some_dir}/mnt2
> # touch ${some_dir}/mnt2/THIS_IS_MNT2
>
> On the client side:
>
> # mkdir /mnt/virtiofs1
> # mount -t virtiofs myfs /mnt/virtiofs1
> # ls /mnt/virtiofs1
> mnt1 mnt2
> # grep virtiofs /proc/mounts
> myfs /mnt/virtiofs1 virtiofs rw,seclabel,relatime 0 0
> none on /mnt/mnt1 type virtiofs (rw,relatime,seclabel)
> none on /mnt/mnt2 type virtiofs (rw,relatime,seclabel)
>
> And now remount it again:
>
> # mount -t virtiofs myfs /mnt/virtiofs2
> # grep virtiofs /proc/mounts
> myfs /mnt/virtiofs1 virtiofs rw,seclabel,relatime 0 0
> none on /mnt/mnt1 type virtiofs (rw,relatime,seclabel)
> none on /mnt/mnt2 type virtiofs (rw,relatime,seclabel)
> myfs /mnt/virtiofs2 virtiofs rw,seclabel,relatime 0 0
> # ls /mnt/virtiofs2
> THIS_IS_MNT2
>
> Submount mnt2 was picked-up instead of the root mount.
Why is this a problem?
Thanks,
Miklos
next prev parent reply other threads:[~2021-05-21 8:26 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-20 15:46 [PATCH v4 0/5] virtiofs: propagate sync() to file server Greg Kurz
2021-05-20 15:46 ` [PATCH v4 1/5] fuse: Fix leak in fuse_dentry_automount() error path Greg Kurz
2021-05-20 19:45 ` Al Viro
2021-05-21 7:54 ` Miklos Szeredi
2021-05-21 8:15 ` Greg Kurz
2021-05-21 8:23 ` Miklos Szeredi
2021-05-21 8:08 ` Greg Kurz
2021-05-20 15:46 ` [PATCH v4 2/5] fuse: Call vfs_get_tree() for submounts Greg Kurz
2021-05-21 8:19 ` Miklos Szeredi
2021-05-21 8:28 ` Greg Kurz
2021-05-22 17:50 ` kernel test robot
2021-05-22 20:12 ` kernel test robot
2021-05-20 15:46 ` [PATCH v4 3/5] fuse: Make fuse_fill_super_submount() static Greg Kurz
2021-05-20 15:46 ` [PATCH v4 4/5] virtiofs: Skip submounts in sget_fc() Greg Kurz
2021-05-21 8:26 ` Miklos Szeredi [this message]
2021-05-21 8:39 ` Greg Kurz
2021-05-21 8:50 ` Miklos Szeredi
2021-05-21 10:06 ` Greg Kurz
2021-05-21 12:37 ` Miklos Szeredi
2021-05-21 13:36 ` Greg Kurz
2021-05-20 15:46 ` [PATCH v4 5/5] virtiofs: propagate sync() to file server Greg Kurz
2021-05-21 10:08 ` Greg Kurz
2021-05-21 12:51 ` Miklos Szeredi
2021-08-15 14:14 ` Amir Goldstein
2021-08-16 15:29 ` Vivek Goyal
2021-08-16 18:57 ` Amir Goldstein
2021-08-16 19:11 ` Vivek Goyal
2021-08-16 19:46 ` Amir Goldstein
2021-08-28 15:21 ` Miklos Szeredi
2021-08-30 17:01 ` Vivek Goyal
2021-08-30 17:36 ` Miklos Szeredi
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