*** Some devices missing ***

*** Some devices missing ***

[Luescher Claude]

Hi,

I have the following array:

Label: 'backup_fs'  uuid: xxxxx
         Total devices 10 FS bytes used 13.46TiB
         devid    1 size 3.64TiB used 3.32TiB path /dev/sdf
         devid    2 size 3.64TiB used 3.32TiB path /dev/sde
         devid    3 size 3.64TiB used 3.32TiB path /dev/sdd
         devid    4 size 3.64TiB used 3.32TiB path /dev/sdg
         devid    5 size 3.64TiB used 3.33TiB path /dev/sdh
         devid    6 size 3.64TiB used 3.33TiB path /dev/sdi
         devid    7 size 3.64TiB used 3.33TiB path /dev/sdc
         devid    8 size 5.46TiB used 1.82TiB path /dev/sdb
         devid    9 size 5.46TiB used 1.82TiB path /dev/sdj
         *** Some devices missing

The server was running 3.13 kernel and btrfs progs 4.0  until it 
crashed. After that mounting the file system hang forever so I decided 
to switch to Linux Kernel 4.8.11 and btrfs-progs v4.8.5.

There are of course no missing devices.  This is what I get in dmesg 
when I try to mount the array with or without the degraded option:

[  362.906958] BTRFS info (device sdf): disk space caching is enabled
[  363.066379] BTRFS error (device sdf): super_num_devices 10 mismatch 
with num_devices 9 found here
[  363.067095] BTRFS error (device sdf): failed to read chunk tree: -22
[  363.086089] BTRFS: open_ctree failed
[  438.747338] BTRFS info (device sdf): allowing degraded mounts
[  438.747341] BTRFS info (device sdf): disk space caching is enabled
[  438.993190] BTRFS error (device sdf): super_num_devices 10 mismatch 
with num_devices 9 found here
[  438.993914] BTRFS error (device sdf): failed to read chunk tree: -22
[  439.013552] BTRFS: open_ctree failed


I only find an old 2014 list entry that it was some bug and fixed so it 
should be long time fixed in 4.8.5. I need to put the device back to 
operation as soon as possible. Anybody have any further ideas what can I 
do?

I running btrfsck on the array and at least that works, but I doubt that 
it will do anything useful.

Thanks

Re: *** Some devices missing ***

[Duncan]

Luescher Claude posted on Tue, 06 Dec 2016 14:00:28 +0100 as excerpted:

> The server was running 3.13 kernel and btrfs progs 4.0  until it
> crashed. After that mounting the file system hang forever so I decided
> to switch to Linux Kernel 4.8.11 and btrfs-progs v4.8.5.
> 
> There are of course no missing devices.  This is what I get in dmesg
> when I try to mount the array with or without the degraded option:

> [363.066379] BTRFS error (device sdf): super_num_devices 10 mismatch
> with num_devices 9 found here

> I only find an old 2014 list entry that it was some bug and fixed so it
> should be long time fixed in 4.8.5. I need to put the device back to
> operation as soon as possible. Anybody have any further ideas what can I
> do?

FWIW there's a very recent (within the last week) thread on this, with a 
patch.  I'm not a dev, just a btrfs user and list regular, so I didn't 
specifically track it, but someone else will likely post a more direct 
link or list the thread name anyway.

IIRC the problem is that under certain circumstances the number of 
devices as given in the superblock can be incorrect, so the patch lets 
btrfs ignore the given number if all chunks (both copies in raid1/10 
mode) appear to be accounted for on already available devices.

I believe the patch has been queued, but isn't in a release yet.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman