Re: "Btrfs: device_list_add() should not update list when mounted" breaks subvol mount

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Hi Xavier,

 Thanks for the report.

 I got this reproduced: its a very corner case, it depends on the
 device path given in the subsequent subvol mounts, the fix appear
 to be outside of this patch at this moment and I am digging to know
 if we need to normalize the device path before using it in the btrfs
 kernel, just like btrfs-progs did recently.


 reproducer:
 ls -l /root/dev/sde-link
   /root/dev/sde-link -> /dev/sde

 mount -o device=/root/dev/sde-link /dev/sdd /btrfs1
 btrfs fi show
 Label: none  uuid: 943bf422-998c-4640-9d7f-d49f17b782ce
	Total devices 2 FS bytes used 272.00KiB
	devid    1 size 1.52GiB used 339.50MiB path /dev/sdd
	devid    2 size 1.52GiB used 319.50MiB path /root/dev/sde-link

 mount -o subvol=sv1,device=/dev/sde /dev/sdd /btrfs  <-shouldn't fail.
  mount: /dev/sdd already mounted or /btrfs busy
  mount: according to mtab, /dev/sdd is mounted on /btrfs1

 mount -o device=/root/dev/sde-link /dev/sdd /btrfs
  echo $?
  0


Xavier, Johannes,

    The quickest workaround for you will be to try to match
 the device path as in the btrfs fi show -m </mnt> output to
 your probably fstab/mnttab entry.


Anand

On 09/13/2014 04:43 AM, xavier.gnata@xxxxxxxxx wrote:
Hi,

On standard ubuntu 14.04 a with an encrypted (cryptsetup) /home as brtfs
subvolume we have the following results:
3.17-rc2 : Ok.
3.17-rc3 and 3.17-rc4 :  /home fails to mount on boot. If one try mount
-a then the system tells that the partition is already mounted according
to matab.



On a 3.17-rc4, btrfs fi sh returns nothing special:
"
Label: none  uuid: f4f554bb-57d9-4647-ab14-ea978c9e7e9f
         Total devices 1 FS bytes used 131.41GiB
         devid    1 size 173.31GiB used 134.03GiB path /dev/sda5

Btrfs v3.12
"

I'm not sure if it has something to do with cryptsetup...


Xavier

Hi Johannes,

I've two more systems with kernel version >3.17-rc3
running and no problem like this.

 Does this 3.17-rc3 also has the same type of subvol config
 and it mount operation/sequence as you mentioned ?

> - one hdd with btrfs
> - default subvolume (rootfs) is different from subovlid=0
> - at boot, several subvols are mounted at /home/$DIR

 I ran a few tests, on our mainline
 ----
 mount -o subvol=sv1 /dev/sdh1 /btrfs
 mount /dev/sdh1 /btrfs
  mount: /dev/sdh1 already mounted or /btrfs busy [*]
 mount /dev/sdh1 /btrfs1
 echo $?
 0
 -----

 [*] hope this isn't the problem you are mentioning.

Thanks, Anand
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