On Fri, Aug 29, 2014 at 12:27:53PM -0400, Trond Myklebust wrote:
> Hi Al,
>
> Our internal testing shows that commit aba809cf0944 (namespace.c: get
> rid of mnt_ghosts) appears to break the NFS automounter functionality.
> When unmounting, the user now gets a permanent -EBUSY, presumably due
> to a refcounting issue with the patch.
>
> The reproducer is as follows:
>
> On the server, set up an export of the form:
>
> % showmount -e 192.168.214.128
> Export list for 192.168.214.128:
> /export *
>
> On the client:
>
> [fedora19@~]$sudo mount 192.168.214.128:/ /mnt/
> [fedora19@~]$df
> Filesystem Size Used Avail Use% Mounted on
> /dev/mapper/fedora-root 38G 15G 24G 38% /
> devtmpfs 229M 0 229M 0% /dev
> tmpfs 242M 80K 242M 1% /dev/shm
> tmpfs 242M 1.5M 241M 1% /run
> tmpfs 242M 0 242M 0% /sys/fs/cgroup
> tmpfs 242M 4.0K 242M 1% /tmp
> /dev/sda1 1.5G 248M 1.3G 17% /boot
> 192.168.214.128:/ 28G 25G 1.1G 96% /mnt
> [fedora19@~]$ls /mnt/export/
> [fedora19@~]$df
> Filesystem Size Used Avail Use% Mounted on
> /dev/mapper/fedora-root 38G 15G 24G 38% /
> devtmpfs 229M 0 229M 0% /dev
> tmpfs 242M 80K 242M 1% /dev/shm
> tmpfs 242M 1.5M 241M 1% /run
> tmpfs 242M 0 242M 0% /sys/fs/cgroup
> tmpfs 242M 4.0K 242M 1% /tmp
> /dev/sda1 1.5G 248M 1.3G 17% /boot
> 192.168.214.128:/ 28G 25G 1.1G 96% /mnt
> 192.168.214.128:/export 28G 25G 1.1G 96% /mnt/export
> [fedora19@~]$sudo umount /mnt
> umount.nfs4: /mnt: device is busy
> [fedora19@~]$df
> Filesystem Size Used Avail Use% Mounted on
> /dev/mapper/fedora-root 38G 15G 24G 38% /
> devtmpfs 229M 0 229M 0% /dev
> tmpfs 242M 80K 242M 1% /dev/shm
> tmpfs 242M 1.5M 241M 1% /run
> tmpfs 242M 0 242M 0% /sys/fs/cgroup
> tmpfs 242M 4.0K 242M 1% /tmp
> /dev/sda1 1.5G 248M 1.3G 17% /boot
> 192.168.214.128:/ 28G 25G 1.1G 96% /mnt
>
> Reverting commit aba809cf0944 fixes the problem for us on a 3.14.15
> client kernel.
Can't reproduce on a debian client with 3.12 kernel (which contains the
commit in question); it'll take a bit to get Fedora setup - I have it as KVM
image, but it's sandboxed to hell and back and certainly not allowed to play
with NFS traffic...
In the meanwhile, if you have a reproducer setup... Could you verify that
fuser -m /mnt does come empty? Another thing: does mount --make-rprivate /
done before that umount /mnt change behaviour? IOW, I wonder if it could
be affected by shared-subtree setup; that might be the relevant difference
between the working box and F19 one in this case. Could you at least post
the contents of /proc/*/mountinfo from all namespaces? Output of
grep . `md5sum /proc/*/mountinfo|sort|uniq -w32|awk '{print $2}'`
would do...
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