problems mounting subvolumes using nfs

i have a luks encrypted btrfs fileserver and have created this subvolume structure on the server for my samba shares

samba top level

---|home                subvolume
---|---|gen                subvolume
---|---|---|s4user        subvolume
---|profile                subvolume
---|print_driver        subvolume

these are my export configurations

cat /etc/exports

# /etc/exports - exports(5) - directories exported to NFS clients
#
/samba/home      
192.168.1.0/24(rw,no_subtree_check,no_root_squash,sync,sec=none:sys:krb5:krb5i:krb5p,insecure)
/samba/profiles  
192.168.1.0/24(rw,no_subtree_check,no_root_squash,sync,sec=none:sys:krb5:krb5i:krb5p,insecure)
/samba/Printer_drivers  
192.168.1.0/24(rw,no_subtree_check,no_root_squash,sync,sec=none:sys:krb5:krb5i:krb5p,insecure)

cat /etc/fstab
# /etc/fstab: static file system information
#

# encryped samba home partition
/dev/mapper/samba_crypt  /samba     btrfs    defaults        0       0

# mount
/dev/mapper/samba_crypt on /samba type btrfs (rw,relatime,space_cache)

# exportfs
exportfs
/samba/home               192.168.1.0/24
/samba/profiles           192.168.1.0/24
/samba/Printer_drivers    192.168.1.0/24

# btrfs subvolume list /samba
ID 257 gen 266 top level 5 path Printer_drivers
ID 258 gen 292 top level 5 path home
ID 259 gen 291 top level 5 path profiles
ID 261 gen 295 top level 258 path home/.snapshots
ID 262 gen 28 top level 261 path home/.snapshots/1/snapshot
ID 267 gen 262 top level 258 path home/gen
ID 268 gen 293 top level 267 path home/gen/s4user
ID 275 gen 61 top level 261 path home/.snapshots/12/snapshot
ID 278 gen 295 top level 268 path home/gen/s4user/.snapshots
ID 280 gen 72 top level 278 path home/gen/s4user/.snapshots/1/snapshot
ID 321 gen 143 top level 261 path home/.snapshots/36/snapshot
ID 322 gen 144 top level 278 path home/gen/s4user/.snapshots/22/snapshot

on the server using autofs
i can mount /samba/profile and /samba/print_driver
i can also mount /samba/home and enter the gen and gen/s4user subvolumes i cannot mount /samba/home/gen or /samba/home/gen/s4user from what i can gather the problem is todo with the subvolume layout of /samba/home/gen and /samba/home/gen/s4user or the export of /samba/home or with the automount specification in auto.master or auto.samba_home any pointers to getting the mounts to work would be appreciated

# uname -a
Linux tardis 4.1.18-1-ARCH #1 SMP Sat Feb 20 17:48:11 MST 2016 armv7l
GNU/Linux

# btrfs --version
btrfs-progs v4.4

# btrfs fi show
Label: 'smbhome'  uuid: 1cec48c5-a2c5-490f-8e9b-63f325721169
        Total devices 1 FS bytes used 1.39MiB
        devid    1 size 149.05GiB used 2.02GiB path /dev/mapper/samba_crypt

# btrfs fi df /samba
Data, single: total=8.00MiB, used=256.00KiB
System, DUP: total=8.00MiB, used=16.00KiB
Metadata, DUP: total=1.00GiB, used=1.12MiB
GlobalReserve, single: total=16.00MiB, used=0.00B

cat auto.master
/samba/home /etc/autofs/auto.samba_home
/samba/profiles /etc/autofs/auto_profiles
/- /etc/autofs/auto.prindrvs
+dir:/etc/autofs/auto.master.d
+auto.master

# cat auto_profiles
* -fstype=nfs,rw,nosuid,hard,sec=sys,vers=3
my.server.my.domain:/samba/profiles/&      

# cat auto.prindrvs
/samba/Printer_drivers -fstype=nfs,rw,nosuid,hard,sec=sys,vers=3
my.server.my.domain:/samba/Printer_drivers      

# cat auto.samba_home
* -fstype=nfs,rw,nosuid,hard,vers=3,sec=sys 
my.server.my.domain:/samba/home/&

# ls -al /samba/home/gen/s4user
ls: cannot access /samba/home/gen/s4user: No such file or directory

# journalctl -f -u autofs
handle_packet: type = 3
handle_packet_missing_indirect: token 53, name gen, request pid 22842
attempting to mount entry /samba/home/gen
lookup_mount: lookup(file): looking up gen
lookup_mount: lookup(file): gen ->
-fstype=nfs,rw,nosuid,hard,vers=3,sec=sys  my.server.my.domain:/samba/home/&
parse_mount: parse(sun): expanded entry:
-fstype=nfs,rw,nosuid,hard,vers=3,sec=sys 
my.server.my.domain:/samba/home/gen
parse_mount: parse(sun): gathered options:
fstype=nfs,rw,nosuid,hard,vers=3,sec=sys
parse_mount: parse(sun): dequote("my.server.my.domain:/samba/home/gen")
-> my.server.my.domain:/samba/home/gen
parse_mount: parse(sun): core of entry:
options=fstype=nfs,rw,nosuid,hard,vers=3,sec=sys,
loc=my.server.my.domain:/samba/home/gen
sun_mount: parse(sun): mounting root /samba/home, mountpoint gen, what
my.server.my.domain:/samba/home/gen, fstype nfs, options
rw,nosuid,hard,vers=3,sec=sys
mount_mount: mount(nfs): root=/samba/home name=gen
what=my.server.my.domain:/samba/home/gen, fstype=nfs,
options=rw,nosuid,hard,vers=3,sec=sys
mount_mount: mount(nfs): nfs options="rw,nosuid,hard,vers=3,sec=sys",
nobind=0, nosymlink=0, ro=0
mount_mount: mount(nfs): calling mkdir_path /samba/home/gen
mount_mount: mount(nfs): calling mount -t nfs -s -o
rw,nosuid,hard,vers=3,sec=sys my.server.my.domain:/samba/home/gen
/samba/home/gen

my.server.my.domain:/samba/home/gen
mount(nfs): nfs: mount failure my.server.my.domain:/samba/home/gen on /samba/home/gen
dev_ioctl_send_fail: token = 53
failed to mount /samba/home/gen
st_expire: state 1 path /samba/home
expire_proc: exp_proc = 1960834160 path /samba/home
expire_cleanup: got thid 1960834160 path /samba/home stat 0
expire_cleanup: sigchld: exp 1960834160 finished, switching from 2 to 1
st_ready: st_ready(): state = 2 path /samba/home
st_expire: state 1 path /-
expire_proc: exp_proc = 1960834160 path /-
expire_cleanup: got thid 1960834160 path /- stat 0
expire_cleanup: sigchld: exp 1960834160 finished, switching from 2 to 1
st_ready: st_ready(): state = 2 path /-

Shadrock

I don't know if this is related to your problem, but one thing you
need to do here is specify different fsid fields for each exported subvol on the same FS. If you don't, NFS can't tell which subvol was intended, and will export the same subvol for each one. So:

/samba/home               -fsid=0x1729 192.168.1.0/24
/samba/profiles           -fsid=0x172a 192.168.1.0/24
/samba/Printer_drivers    -fsid=0x172b 192.168.1.0/24

I suspect that you may not be able to export nested subvols, either
(which is probably your conclusion below). I haven't actually tested that theory, though. (I don't tend to use nested subvols at all; they're more trouble than they're worth in most cases, in my experience).

I would suggest mounting, or bind-mounting, to /samba/$whatever
every individual subvol that you want to be able to export, and putting in a separate export entry for it in /etc/exports.

Hugo.

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