Re: call trace: WARNING: at /build/linux-uwVqDp/linux-4.16.16/fs/btrfs/ctree.h:1565 btrfs_update_device

[Christoph Anton Mitterer <calestyo@scientia.net>]

Hey Qu and Nikolay.


On Thu, 2018-06-28 at 22:58 +0800, Qu Wenruo wrote:
> Nothing special. Btrfs-progs will handle it pretty well.
Since this a remote system where the ISP provides only a rescue image
with pretty old kernel/btrfs-progs, I had to copy a current local
binary and use that... but that seemed to have worked quite well

> Because the WARN_ON() is newly added.
Ah I see.

> Yep, latest will warn about it, and --repair can also fix it too.
Great.


On Thu, 2018-06-28 at 17:25 +0300, Nikolay Borisov wrote:
> Was this an old FS or a fresh one?
You mean in terms of original fs creation? Probably rather oldish.. I'd
guess at least a year or maybe even 2-3 or more.

> Looking at the callstack this
> seems
> to have occured due to "btrfs_set_device_total_bytes(leaf, dev_item,
> btrfs_device_get_disk_total_bytes(device));" call. Meaning the total
> bytes of the disk were unalgined. Perhaps this has been like that for
> quite some time, then you did a couple of kernel upgrades (this
> WARN_ON
> was added later than 4.11) and just now you happened to delete a
> chunk
> which would trigger a device update on-disk ?
Could be...


The following was however still a bit strange:
sda2 and sdb2 are the partitions on the two HDDs forming the RAID1.


root@rescue ~ # ./btrfs rescue fix-device-size /dev/sda2
Fixed device size for devid 2, old size: 999131127296 new size: 999131123712
Fixed super total bytes, old size: 1998262251008 new size: 1998262247424
Fixed unaligned/mismatched total_bytes for super block and device items
root@rescue ~ # ./btrfs rescue fix-device-size /dev/sdb2
No device size related problem found

As you can see, no alignment issues were found on sdb2.

I've created these at the same time...
I don't think (but cannot exclude for 100%) that this server ever lost
a disk (in that case I could image that newer progs/kernel might have
created sdb2 with proper alignment)

Looking at the partitions:

root@rescue ~ # gdisk -l /dev/sda
GPT fdisk (gdisk) version 1.0.1

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/sda: 1953525168 sectors, 931.5 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 1953525134
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048         2097151   1023.0 MiB  EF02  BIOS boot partition
   2         2097152      1953525134   930.5 GiB   8300  Linux filesystem
root@rescue ~ # gdisk -l /dev/sdb
GPT fdisk (gdisk) version 1.0.1

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/sdb: 1953525168 sectors, 931.5 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 1953525134
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048         2097151   1023.0 MiB  EF02  BIOS boot partition
   2         2097152      1953525134   930.5 GiB   8300  Linux filesystem


Both the same... so if there was no device replace or so... then I
wonder why only one device was affected.


Cheers,
Chris.