On 2015-09-23 18:32, Goffredo Baroncelli wrote:
> On 2015-09-21 12:20, Rob wrote:
>> 2. btrfs scrub cancel /media/btrfs-rpi-raid6
>>
>> - I waited 4h but this didnt return to a prompt (tried unmounting,
>> killall -9 btrfs) so i switched power off to the disks, replaced
>> the faulty disk and switched the enclosure on again.
>
> I don't understood if the disks are in an external enclosure which
> was switched OFF (leaving the system ON) or you have switched OFF all
> the system. Could you clarify ?
>
I was able to reproduce this; the good new is that I reproduced this issue with an old kernel (v4.1.5); a more recent kernel (v4.2.1) doesn't show the problem.
I suspect that the commit below solved this issue:
commit 4fde46f0cc71c7aba299ee6dfb4f017fb97b6e70
Author: Anand Jain <Anand.Jain@xxxxxxxxxx>
Date: Wed Jun 17 21:10:48 2015 +0800
Btrfs: free the stale device
When btrfs on a device is overwritten with a new btrfs (mkfs),
the old btrfs instance in the kernel becomes stale. So with this
patch, if kernel finds device is overwritten then delete the stale
fsid/uuid.
To trigger the problem you have to re-register two different devices (== different dev_uuid) with the same device name and the same fs_uuid (without rebooting).
Below how I reproduced this issue:
# creating the filesystem
truncate -s 20G img0
truncate -s 20G img1
truncate -s 20G img2
truncate -s 20G img3
losetup /dev/loop0 img0
losetup /dev/loop1 img1
losetup /dev/loop2 img2
losetup /dev/loop3 img3
mkfs.btrfs -draid6 -mraid6 /dev/loop[0-3]
# mount and use the filesystem
mount /dev/loop1 /mnt/test
[...]
umount /mnt/test
# remove the img2, rotate the devices
losetup -d /dev/loop0
losetup -d /dev/loop1
losetup -d /dev/loop2
losetup -d /dev/loop3
losetup /dev/loop1 img0
losetup /dev/loop2 img1
losetup /dev/loop3 img3
#NOTE /dev/loop0 is unassigned
mount -o degraded /dev/loop1 /mnt/test
btrfs fi usage /mnt/test
WARNING: RAID56 detected, not implemented
WARNING: RAID56 detected, not implemented
WARNING: RAID56 detected, not implemented
Overall:
Device size: 80.00GiB
Device allocated: 20.00MiB
Device unallocated: 79.98GiB
Device missing: 0.00B
Used: 0.00B
Free (estimated): 20.07TiB (min: 81.99GiB)
Data ratio: 0.00
Metadata ratio: 0.00
Global reserve: 16.00MiB (used: 0.00B)
Data,single: Size:8.00MiB, Used:0.00B
/dev/loop1 8.00MiB
Data,RAID6: Size:2.00GiB, Used:11.00MiB
/dev/loop1 1.00GiB
/dev/loop2 1.00GiB
/dev/loop2 1.00GiB
/dev/loop3 1.00GiB
Metadata,single: Size:8.00MiB, Used:0.00B
/dev/loop1 8.00MiB
Metadata,RAID6: Size:2.00GiB, Used:112.00KiB
/dev/loop1 1.00GiB
/dev/loop2 1.00GiB
/dev/loop2 1.00GiB
/dev/loop3 1.00GiB
System,single: Size:4.00MiB, Used:0.00B
/dev/loop1 4.00MiB
System,RAID6: Size:16.00MiB, Used:16.00KiB
/dev/loop1 8.00MiB
/dev/loop2 8.00MiB
/dev/loop2 8.00MiB
/dev/loop3 8.00MiB
Unallocated:
/dev/loop1 17.97GiB
/dev/loop2 17.99GiB
/dev/loop2 17.99GiB
/dev/loop3 17.99GiB
BR
G.Baroncelli
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