Re: unable to mount btrfs after upgrading from 4.16.1 to 4.19.1

[Tomasz Chmielewski <tch@virtall.com>]

On 2018-11-10 04:20, Tomasz Chmielewski wrote:
> On 2018-11-10 04:15, Tomasz Chmielewski wrote:
>> On 2018-11-10 03:20, Roman Mamedov wrote:
>>> On Sat, 10 Nov 2018 03:08:01 +0900
>>> Tomasz Chmielewski <tch@virtall.com> wrote:
>>> 
>>>> After upgrading from kernel 4.16.1 to 4.19.1 and a clean restart, 
>>>> the fs
>>>> no longer mounts:
>>> 
>>> Did you try rebooting back to 4.16.1 to see if it still mounts there?
>> 
>> Yes, just did.
>> 
>> Interestingly, it does mount when I boot back to 4.16.1 - side note -
>> it takes some 50 (!) minutes and ~8 GB of reads (according to iostat
>> -m) to mount... device size is 16 TB, on HDD.
> 
> Also - it did mount with 4.18.17.
> 
> Way faster, in some 2 min.

A few more clean reboot cycles with 4.18.17 and got:

[  113.677829] BTRFS error (device md2): open_ctree failed
[  113.692298] BTRFS info (device md2): force zstd compression, level 0
[  113.692302] BTRFS info (device md2): using free space tree
[  113.692304] BTRFS info (device md2): has skinny extents
[  113.897681] BTRFS error (device md2): super_total_bytes 
17920974913536 mismatch with fs_devices total_rw_bytes 35841949827072
[  113.897751] BTRFS error (device md2): failed to read chunk tree: -22
[  113.935149] BTRFS error (device md2): open_ctree failed


Another "mount /data" (without rebooting) mounted it fine.

Why are btrfs mounts so irregular here?

# btrfs device stats /data
[/dev/md2].write_io_errs    0
[/dev/md2].read_io_errs     0
[/dev/md2].flush_io_errs    0
[/dev/md2].corruption_errs  0
[/dev/md2].generation_errs  0


# btrfs fi usage /data
Overall:
     Device size:                  16.30TiB
     Device allocated:             14.26TiB
     Device unallocated:            2.04TiB
     Device missing:                  0.00B
     Used:                          7.99TiB
     Free (estimated):              8.27TiB      (min: 8.27TiB)
     Data ratio:                       1.00
     Metadata ratio:                   1.00
     Global reserve:              512.00MiB      (used: 0.00B)

Data,single: Size:14.15TiB, Used:7.92TiB
    /dev/md2       14.15TiB

Metadata,single: Size:111.00GiB, Used:74.78GiB
    /dev/md2      111.00GiB

System,single: Size:32.00MiB, Used:1.81MiB
    /dev/md2       32.00MiB

Unallocated:
    /dev/md2        2.04TiB



Tomasz Chmielewski
https://lxadm.com