Re: [Xen-users] PV DomU can't access disk from storage driver domain

[Alex Velazquez <alex.j.velazquez@xxxxxxxxx>]

On Fri, Sep 18, 2015 at 1:28 PM, Roger Pau Monnà <roger.pau@xxxxxxxxxx> wrote:
> El 18/09/15 a les 16.54, Alex Velazquez ha escrit:
>> Hi Roger,
>>
>> Thanks for your reply. I got a bit further now, but still hit some errors.
>>
>> First, as you suggested, I started the xendriverdomain service via the
>> init script (and have it start automatically on boot). "xl devd"
>> starts as expected and creates a log file at /var/log/xen/xldevd.log.
>>
>> When I start the client DomU, it receives the disk and is able to boot
>> from it. I can even log in, if I do it quickly. However, after a few
>> seconds, the client locks up and I see this printed to the console:
>>
>>  [    9.938197] vbd vbd-51712: 16 Device in use; refusing to close
>>  [    9.938524] vbd vbd-51712: failed to write error node for
>> device/vbd/51712 (16 Device in use; refusing to close)
>
> Can you print the xenstore related entries at this point (for both the
> frontend and the backend)?
>
> It's quite strange that a disk successfully connects and then
> disconnects without any apparent reason. Does the kernel log (dmesg) in
> the driver domain contain any hint about why it was disconnected?
>
> Roger.
>


The last few lines in storagedd's kernel log are:

 admin@storagedd:~$ sudo dmesg
 [....]
 [    4.012464] init: plymouth-upstart-bridge main process (163)
killed by TERM signal
 [    5.561811] init: plymouth-splash main process (1078) terminated
with status 1
 [   48.847611] xen-blkback:ring-ref 2047, event-channel 4, protocol 1
(x86_64-abi)
 [   52.758780] xen-blkback:backend/vbd/9/51712: prepare for reconnect
 [   52.927883] xen-blkback:ring-ref 8, event-channel 10, protocol 1
(x86_64-abi) persistent grants

While the client is booting, the backend entry appears in xenstore, as such:

 xenuser@xenhost:~$ sudo xenstore-ls /local/domain/2/backend
 vbd = ""
  3 = ""
   51712 = ""
    frontend = "/local/domain/3/device/vbd/51712"
    params = "/dev/loop0"
    script = "/etc/xen/scripts/block"
    frontend-id = "3"
    online = "1"
    removable = "0"
    bootable = "1"
    state = "4"
    dev = "xvda"
    type = "phy"
    mode = "w"
    device-type = "disk"
    discard-enable = "1"
    physical-device = "7:0"
    hotplug-status = "connected"
    feature-flush-cache = "1"
    discard-granularity = "4096"
    discard-alignment = "0"
    discard-secure = "0"
    feature-discard = "1"
    feature-barrier = "1"
    feature-persistent = "1"
    feature-max-indirect-segments = "256"
    sectors = "25165824"
    info = "0"
    sector-size = "512"
    physical-sector-size = "512"

However, interestingly, it clears out after a few seconds:

 xenuser@xenhost:~$ sudo xenstore-ls /local/domain/2/backend
 backend = ""
  vbd = ""
   3 = ""

Meanwhile, on the client's console, I see the following:

   Booting 'Ubuntu 14.04.3 LTS, kernel 3.13.0-63-generic'

 root  (hd0,0)
  Filesystem type is ext2fs, partition type 0x83
 kernel  /boot/vmlinuz-3.13.0-63-generic root=UUID=6084538e-aa25-4ede-a68e-57c66
 5d0ab8c ro console=xvc0 root=/dev/xvda1 ro quiet splash
 initrd  /boot/initrd.img-3.13.0-63-generic

 ============= Init TPM Front ================
 Tpmfront:Error Unable to read device/vtpm/0/backend-id during
tpmfront initialization! error = ENOENT
 Tpmfront:Info Shutting down tpmfront
 close blk: backend=/local/domain/2/backend/vbd/3/51712 node=device/vbd/51712

These messages disappear pretty quickly and I'm presented with the
login prompt. But then, a few seconds later:

 [    9.942627] vbd vbd-51712: 16 Device in use; refusing to close
 [    9.942982] vbd vbd-51712: failed to write error node for
device/vbd/51712 (16 Device in use; refusing to close)

Here's the full xenstore entry for the client:

 xenuser@xenhost:~$ sudo xenstore-ls /local/domain/3
 vm = "/vm/8defe686-be33-4a9f-a067-f39309429c56"
 name = "client"
 cpu = ""
  0 = ""
   availability = "online"
 memory = ""
  static-max = "1048576"
  target = "1048576"
  videoram = "0"
 device = ""
  suspend = ""
   event-channel = ""
  vbd = ""
   51712 = ""
    backend = "/local/domain/2/backend/vbd/3/51712"
    backend-id = "2"
    state = "5"
    virtual-device = "51712"
    device-type = "disk"
    protocol = "x86_64-abi"
    ring-ref = "8"
    event-channel = "10"
    feature-persistent = "1"
  vif = ""
   0 = ""
    backend = "/local/domain/0/backend/vif/3/0"
    backend-id = "0"
    state = "4"
    handle = "0"
    mac = "00:16:3e:37:00:02"
    tx-ring-ref = "9"
    rx-ring-ref = "10"
    event-channel-tx = "11"
    event-channel-rx = "12"
    request-rx-copy = "1"
    feature-rx-notify = "1"
    feature-sg = "1"
    feature-gso-tcpv4 = "1"
 control = ""
  shutdown = ""
  platform-feature-multiprocessor-suspend = "1"
  platform-feature-xs_reset_watches = "1"
 data = ""
 domid = "3"
 store = ""
  port = "1"
  ring-ref = "2360741"
 console = ""
  backend = "/local/domain/0/backend/console/3/0"
  backend-id = "0"
  limit = "1048576"
  type = "xenconsoled"
  output = "pty"
  tty = "/dev/pts/15"
  port = "2"
  ring-ref = "2360742"

Thanks,
Alex

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