Mysterious device (id 0).

Mysterious device (id 0).

[Christian]

Hi,

My laptop has a small ext4 /boot partition /dev/sda1 and a large btrfs 
partition containing / and /home as a sub volume /dev/sda3

When I run scrub on /dev/sda3 and check status with sudo btrfs scrub 
status -d /dev/sda3 I get:

scrub status for 3d52dc93-c89f-453f-965d-8601d11e7710
scrub device /dev/sda3 (id 1) history
	scrub started at Thu May 14 19:54:02 2015 and finished after 235 seconds
	total bytes scrubbed: 111.03GiB with 0 errors
scrub device  (id 0) history
	scrub started at Thu May 14 19:54:02 2015 and was aborted after 0 seconds
	total bytes scrubbed: 0.00B with 0 errors

As device (id 0) is indicated, but I have no idea what it is.

When I run scrub with a script (cron) the same device (id 0) shows up in 
a warning:

/etc/cron.daily/btrfs-scrub:
WARNING: device 0 not present
scrub device /dev/sda3 (id 1) done
     scrub started at Sat May  2 08:03:46 2015 and finished after 241 
seconds
     total bytes scrubbed: 109.06GiB with 0 errors
scrub device  (id 0) canceled
     scrub started at Sat May  2 08:03:46 2015 and was aborted after 0 
seconds
     total bytes scrubbed: 0.00B with 0 errors

What is this device (id 0) which never gets scrubbed but always shows up?

I'm running Ubuntu 15.04 with the 3.19.0-16-generic kernel.

P.S. I am not a developer.

-- 
//Christian

Re: Mysterious device (id 0).

[Austin S Hemmelgarn]

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On 2015-05-14 20:09, Christian wrote:
> Hi,
>
> My laptop has a small ext4 /boot partition /dev/sda1 and a large btrfs
> partition containing / and /home as a sub volume /dev/sda3
>
> When I run scrub on /dev/sda3 and check status with sudo btrfs scrub
> status -d /dev/sda3 I get:
>
> scrub status for 3d52dc93-c89f-453f-965d-8601d11e7710
> scrub device /dev/sda3 (id 1) history
>      scrub started at Thu May 14 19:54:02 2015 and finished after 235
> seconds
>      total bytes scrubbed: 111.03GiB with 0 errors
> scrub device  (id 0) history
>      scrub started at Thu May 14 19:54:02 2015 and was aborted after 0
> seconds
>      total bytes scrubbed: 0.00B with 0 errors
>
> As device (id 0) is indicated, but I have no idea what it is.
>
> When I run scrub with a script (cron) the same device (id 0) shows up in
> a warning:
>
> /etc/cron.daily/btrfs-scrub:
> WARNING: device 0 not present
> scrub device /dev/sda3 (id 1) done
>      scrub started at Sat May  2 08:03:46 2015 and finished after 241
> seconds
>      total bytes scrubbed: 109.06GiB with 0 errors
> scrub device  (id 0) canceled
>      scrub started at Sat May  2 08:03:46 2015 and was aborted after 0
> seconds
>      total bytes scrubbed: 0.00B with 0 errors
>
> What is this device (id 0) which never gets scrubbed but always shows up?
>
> I'm running Ubuntu 15.04 with the 3.19.0-16-generic kernel.
>
Have you ever run 'btrfs replace' to replace a device in the filesystem? 
  I know that new device in a replace operation get's tagged as device 
id 0 until the replace operation completes (at which point it gets the 
devid of the device it replaced).  Personally, this is the only case 
that I know of that devid 0 is actually used in the code.  Thinking 
further though, it might also be an off-by-one error somewhere, although 
I have no idea where.



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Re: Mysterious device (id 0).

[Christian]

On 05/15/2015 07:25 AM, Austin S Hemmelgarn wrote:

> On 2015-05-14 20:09, Christian wrote:
>> Hi,
>>
>> My laptop has a small ext4 /boot partition /dev/sda1 and a large btrfs
>> partition containing / and /home as a sub volume /dev/sda3
>>
>> When I run scrub on /dev/sda3 and check status with sudo btrfs scrub
>> status -d /dev/sda3 I get:
>>
>> scrub status for 3d52dc93-c89f-453f-965d-8601d11e7710
>> scrub device /dev/sda3 (id 1) history
>>      scrub started at Thu May 14 19:54:02 2015 and finished after 235
>> seconds
>>      total bytes scrubbed: 111.03GiB with 0 errors
>> scrub device  (id 0) history
>>      scrub started at Thu May 14 19:54:02 2015 and was aborted after 0
>> seconds
>>      total bytes scrubbed: 0.00B with 0 errors
>>
>> As device (id 0) is indicated, but I have no idea what it is.
>>
>> When I run scrub with a script (cron) the same device (id 0) shows up in
>> a warning:
>>
>> /etc/cron.daily/btrfs-scrub:
>> WARNING: device 0 not present
>> scrub device /dev/sda3 (id 1) done
>>      scrub started at Sat May  2 08:03:46 2015 and finished after 241
>> seconds
>>      total bytes scrubbed: 109.06GiB with 0 errors
>> scrub device  (id 0) canceled
>>      scrub started at Sat May  2 08:03:46 2015 and was aborted after 0
>> seconds
>>      total bytes scrubbed: 0.00B with 0 errors
>>
>> What is this device (id 0) which never gets scrubbed but always shows up?
>>
>> I'm running Ubuntu 15.04 with the 3.19.0-16-generic kernel.
>>
> Have you ever run 'btrfs replace' to replace a device in the filesystem?
>   I know that new device in a replace operation get's tagged as device
> id 0 until the replace operation completes (at which point it gets the
> devid of the device it replaced).  Personally, this is the only case
> that I know of that devid 0 is actually used in the code.  Thinking
> further though, it might also be an off-by-one error somewhere, although
> I have no idea where.
>
>
No, I have never run 'btrfs replace'. This problem was discussed in a 
previous thread covering the script I am using for daily scrub. The 
author had the same problem, but for him it simply went away. Not for me 
though. The thread was

"Re: 3.19.3: check tree block failed + WARNING: device 0 not present on 
scrub".

I have had some problems with btrfs in the past so I am very ware of any 
error message! I can't live without the snapshots anymore though :)


-- 
//Christian

Re: Mysterious device (id 0).

[Anand Jain]

On 05/15/2015 08:09 AM, Christian wrote:
> Hi,
>
> My laptop has a small ext4 /boot partition /dev/sda1 and a large btrfs
> partition containing / and /home as a sub volume /dev/sda3
>
> When I run scrub on /dev/sda3 and check status with sudo btrfs scrub
> status -d /dev/sda3 I get:
>
> scrub status for 3d52dc93-c89f-453f-965d-8601d11e7710
> scrub device /dev/sda3 (id 1) history
>      scrub started at Thu May 14 19:54:02 2015 and finished after 235
> seconds
>      total bytes scrubbed: 111.03GiB with 0 errors
> scrub device  (id 0) history
>      scrub started at Thu May 14 19:54:02 2015 and was aborted after 0
> seconds
>      total bytes scrubbed: 0.00B with 0 errors

  we are reading an uninitialized device struct and that uninitialized
  devid happens to be 0. looks like num_devices count went haywire.

  in this config was there any device delete ? or a reduce in # of
  devices? and has the system been rebooted after that ?

Thanks, Anand


> As device (id 0) is indicated, but I have no idea what it is.
>
> When I run scrub with a script (cron) the same device (id 0) shows up in
> a warning:
>
> /etc/cron.daily/btrfs-scrub:
> WARNING: device 0 not present
> scrub device /dev/sda3 (id 1) done
>      scrub started at Sat May  2 08:03:46 2015 and finished after 241
> seconds
>      total bytes scrubbed: 109.06GiB with 0 errors
> scrub device  (id 0) canceled
>      scrub started at Sat May  2 08:03:46 2015 and was aborted after 0
> seconds
>      total bytes scrubbed: 0.00B with 0 errors
>
> What is this device (id 0) which never gets scrubbed but always shows up?
>
> I'm running Ubuntu 15.04 with the 3.19.0-16-generic kernel.
>
> P.S. I am not a developer.
>

Re: Mysterious device (id 0).

[Christian]

On 05/15/2015 12:20 PM, Anand Jain wrote:
>
>
> On 05/15/2015 08:09 AM, Christian wrote:
>> Hi,
>>
>> My laptop has a small ext4 /boot partition /dev/sda1 and a large btrfs
>> partition containing / and /home as a sub volume /dev/sda3
>>
>> When I run scrub on /dev/sda3 and check status with sudo btrfs scrub
>> status -d /dev/sda3 I get:
>>
>> scrub status for 3d52dc93-c89f-453f-965d-8601d11e7710
>> scrub device /dev/sda3 (id 1) history
>>      scrub started at Thu May 14 19:54:02 2015 and finished after 235
>> seconds
>>      total bytes scrubbed: 111.03GiB with 0 errors
>> scrub device  (id 0) history
>>      scrub started at Thu May 14 19:54:02 2015 and was aborted after 0
>> seconds
>>      total bytes scrubbed: 0.00B with 0 errors
>
>   we are reading an uninitialized device struct and that uninitialized
>   devid happens to be 0. looks like num_devices count went haywire.
>
>   in this config was there any device delete ? or a reduce in # of
>   devices? and has the system been rebooted after that ?
>
> Thanks, Anand

Not sure I understand fully what you are asking, but I deleted a swap 
partition on the drive a while back and increased the size of the btrfs 
partition (with gparted). I have rebooted many times since then. That is 
all the changes I have done to this SSD recently.

Thanks.
>
>
>> As device (id 0) is indicated, but I have no idea what it is.
>>
>> When I run scrub with a script (cron) the same device (id 0) shows up in
>> a warning:
>>
>> /etc/cron.daily/btrfs-scrub:
>> WARNING: device 0 not present
>> scrub device /dev/sda3 (id 1) done
>>      scrub started at Sat May  2 08:03:46 2015 and finished after 241
>> seconds
>>      total bytes scrubbed: 109.06GiB with 0 errors
>> scrub device  (id 0) canceled
>>      scrub started at Sat May  2 08:03:46 2015 and was aborted after 0
>> seconds
>>      total bytes scrubbed: 0.00B with 0 errors
>>
>> What is this device (id 0) which never gets scrubbed but always shows up?
>>
>> I'm running Ubuntu 15.04 with the 3.19.0-16-generic kernel.
>>
>> P.S. I am not a developer.
>>
> --



-- 
//Christian

Re: Mysterious device (id 0).

[Anand Jain]

On 05/16/2015 12:37 AM, Christian wrote:
> On 05/15/2015 12:20 PM, Anand Jain wrote:
>>
>>
>> On 05/15/2015 08:09 AM, Christian wrote:
>>> Hi,
>>>
>>> My laptop has a small ext4 /boot partition /dev/sda1 and a large btrfs
>>> partition containing / and /home as a sub volume /dev/sda3
>>>
>>> When I run scrub on /dev/sda3 and check status with sudo btrfs scrub
>>> status -d /dev/sda3 I get:
>>>
>>> scrub status for 3d52dc93-c89f-453f-965d-8601d11e7710
>>> scrub device /dev/sda3 (id 1) history
>>>      scrub started at Thu May 14 19:54:02 2015 and finished after 235
>>> seconds
>>>      total bytes scrubbed: 111.03GiB with 0 errors
>>> scrub device  (id 0) history
>>>      scrub started at Thu May 14 19:54:02 2015 and was aborted after 0
>>> seconds
>>>      total bytes scrubbed: 0.00B with 0 errors
>>
>>   we are reading an uninitialized device struct and that uninitialized
>>   devid happens to be 0. looks like num_devices count went haywire.
>>
>>   in this config was there any device delete ? or a reduce in # of
>>   devices? and has the system been rebooted after that ?
>>
>> Thanks, Anand
>
> Not sure I understand fully what you are asking, but I deleted a swap
> partition on the drive a while back and increased the size of the btrfs
> partition (with gparted). I have rebooted many times since then. That is
> all the changes I have done to this SSD recently.

  ok got it. now do you have any other disk in the system with the same
  fsid ? what does the btrfs fi show -d or blkid show.

Thanks


> Thanks.
>>
>>
>>> As device (id 0) is indicated, but I have no idea what it is.
>>>
>>> When I run scrub with a script (cron) the same device (id 0) shows up in
>>> a warning:
>>>
>>> /etc/cron.daily/btrfs-scrub:
>>> WARNING: device 0 not present
>>> scrub device /dev/sda3 (id 1) done
>>>      scrub started at Sat May  2 08:03:46 2015 and finished after 241
>>> seconds
>>>      total bytes scrubbed: 109.06GiB with 0 errors
>>> scrub device  (id 0) canceled
>>>      scrub started at Sat May  2 08:03:46 2015 and was aborted after 0
>>> seconds
>>>      total bytes scrubbed: 0.00B with 0 errors
>>>
>>> What is this device (id 0) which never gets scrubbed but always shows
>>> up?
>>>
>>> I'm running Ubuntu 15.04 with the 3.19.0-16-generic kernel.
>>>
>>> P.S. I am not a developer.
>>>
>> --
>
>
>

Re: Mysterious device (id 0).

[Christian]

On 05/15/2015 12:51 PM, Anand Jain wrote:
>
>
> On 05/16/2015 12:37 AM, Christian wrote:
>> On 05/15/2015 12:20 PM, Anand Jain wrote:
>>>
>>>
>>> On 05/15/2015 08:09 AM, Christian wrote:
>>>> Hi,
>>>>
>>>> My laptop has a small ext4 /boot partition /dev/sda1 and a large btrfs
>>>> partition containing / and /home as a sub volume /dev/sda3
>>>>
>>>> When I run scrub on /dev/sda3 and check status with sudo btrfs scrub
>>>> status -d /dev/sda3 I get:
>>>>
>>>> scrub status for 3d52dc93-c89f-453f-965d-8601d11e7710
>>>> scrub device /dev/sda3 (id 1) history
>>>>      scrub started at Thu May 14 19:54:02 2015 and finished after 235
>>>> seconds
>>>>      total bytes scrubbed: 111.03GiB with 0 errors
>>>> scrub device  (id 0) history
>>>>      scrub started at Thu May 14 19:54:02 2015 and was aborted after 0
>>>> seconds
>>>>      total bytes scrubbed: 0.00B with 0 errors
>>>
>>>   we are reading an uninitialized device struct and that uninitialized
>>>   devid happens to be 0. looks like num_devices count went haywire.
>>>
>>>   in this config was there any device delete ? or a reduce in # of
>>>   devices? and has the system been rebooted after that ?
>>>
>>> Thanks, Anand
>>
>> Not sure I understand fully what you are asking, but I deleted a swap
>> partition on the drive a while back and increased the size of the btrfs
>> partition (with gparted). I have rebooted many times since then. That is
>> all the changes I have done to this SSD recently.
>
>   ok got it. now do you have any other disk in the system with the same
>   fsid ? what does the btrfs fi show -d or blkid show.
>
> Thanks

btrfs fi show -d
Label: none  uuid: 3d52dc93-c89f-453f-965d-8601d11e7710
	Total devices 1 FS bytes used 108.94GiB
	devid    1 size 222.84GiB used 111.03GiB path /dev/sda3


blkid
/dev/sda1: UUID="82348a5a-6c11-47dc-a4aa-884431c7cc1a" TYPE="ext4" 
PARTUUID="8e3b64c9-0f7d-4720-be83-8de7a63ec246"
/dev/sda3: UUID="3d52dc93-c89f-453f-965d-8601d11e7710" 
UUID_SUB="91c64b93-2eb7-4e98-b940-57a2ae3edd6e" TYPE="btrfs" 
PARTUUID="40fcadee-050e-4f5d-8538-6abdfc57c7b8"

It probably doesn't matter but the drive is an INTEL SSD on a Lenovo 
Thinkpad X1 Carbon with Ubuntu 15.04

>
>
>> Thanks.
>>>
>>>
>>>> As device (id 0) is indicated, but I have no idea what it is.
>>>>
>>>> When I run scrub with a script (cron) the same device (id 0) shows
>>>> up in
>>>> a warning:
>>>>
>>>> /etc/cron.daily/btrfs-scrub:
>>>> WARNING: device 0 not present
>>>> scrub device /dev/sda3 (id 1) done
>>>>      scrub started at Sat May  2 08:03:46 2015 and finished after 241
>>>> seconds
>>>>      total bytes scrubbed: 109.06GiB with 0 errors
>>>> scrub device  (id 0) canceled
>>>>      scrub started at Sat May  2 08:03:46 2015 and was aborted after 0
>>>> seconds
>>>>      total bytes scrubbed: 0.00B with 0 errors
>>>>
>>>> What is this device (id 0) which never gets scrubbed but always shows
>>>> up?
>>>>
>>>> I'm running Ubuntu 15.04 with the 3.19.0-16-generic kernel.
>>>>
>>>> P.S. I am not a developer.
>>>>
>>> --
>>
>>
>>
> --


-- 
//Christian