smaller testcase that shows the immediate enospc after fallocate -> rm,
though I don't know if it is really related to the full filesystem
bugging out as the balance does work if you wait a few seconds after the
balance.
But this sequence of commands did work in 4.2.
$ sudo btrfs fi show /dev/mapper/lvm-testing
Label: none uuid: 25889ba9-a957-415a-83b0-e34a62cb3212
Total devices 1 FS bytes used 225.18MiB
devid 1 size 5.00GiB used 788.00MiB path /dev/mapper/lvm-testing
$ fallocate -l 4.4G test.dat
$ rm -f test.dat
$ sudo btrfs fi balance start -dusage=0 .
ERROR: error during balancing '.': No space left on device
There may be more info in syslog - try dmesg | tail
On 04/12/2016 12:24 PM, Julian Taylor wrote:
> hi,
> I have a system with two filesystems which are both affected by the
> notorious enospace bug when there is plenty of unallocated space
> available. The system is a raid0 on two 900 GiB disks and an iscsi
> single/dup 1.4TiB.
> To deal with the problem I use a cronjob that uses fallocate to give me
> an advance notice on the issue so I can apply the only workaround that
> works for me, which is shrink the fs to the minimum and grow it again.
> This has worked fine for a couple of month.
>
> I now updated from 4.2 to 4.4.6 and it appears my cronjob actually
> triggers an immediate enospc in the balance after removing the
> fallocated file and the shrink/resize workaround does not work anymore.
> it is mounted with enospc_debug but that just says "2 enospc in
> balance". Nothing else useful in the log.
>
> I had to revert back to 4.2 to get the system running again so it is
> currently not available for more testing, but I may be able to do more
> tests if required in future.
>
> The cronjob does this once a day:
>
> #!/bin/bash
> sync
>
> check() {
> date
> mnt=$1
> time btrfs fi balance start -mlimit=2 $mnt
> btrfs fi balance start -dusage=5 $mnt
> sync
> freespace=$(df -B1 $mnt | tail -n 1 | awk '{print $4 -
> 50*1024*1024*1024}')
> fallocate -l $freespace $mnt/falloc
> /usr/sbin/filefrag $mnt/falloc
> rm -f $mnt/falloc
> btrfs fi balance start -dusage=0 $mnt
>
> time btrfs fi balance start -mlimit=2 $mnt
> time btrfs fi balance start -dlimit=10 $mnt
> date
> }
>
> check /data
> check /data/nas
>
>
> btrfs info:
>
>
> ~ $ btrfs --version
> btrfs-progs v4.4
> sagan5 ~ $ sudo btrfs fi show
> Label: none uuid: e4aef349-7a56-4287-93b1-79233e016aae
> Total devices 2 FS bytes used 898.18GiB
> devid 1 size 880.00GiB used 473.03GiB path /dev/mapper/data-linear1
> devid 2 size 880.00GiB used 473.03GiB path /dev/mapper/data-linear2
>
> Label: none uuid: 14040f9b-53c8-46cf-be6b-35de746c3153
> Total devices 1 FS bytes used 557.19GiB
> devid 1 size 1.36TiB used 585.95GiB path /dev/sdd
>
> ~ $ sudo btrfs fi df /data
> Data, RAID0: total=938.00GiB, used=895.09GiB
> System, RAID1: total=32.00MiB, used=112.00KiB
> Metadata, RAID1: total=4.00GiB, used=3.10GiB
> GlobalReserve, single: total=512.00MiB, used=0.00B
> sagan5 ~ $ sudo btrfs fi usage /data
> Overall:
> Device size: 1.72TiB
> Device allocated: 946.06GiB
> Device unallocated: 813.94GiB
> Device missing: 0.00B
> Used: 901.27GiB
> Free (estimated): 856.85GiB (min: 449.88GiB)
> Data ratio: 1.00
> Metadata ratio: 2.00
> Global reserve: 512.00MiB (used: 0.00B)
>
> Data,RAID0: Size:938.00GiB, Used:895.09GiB
> /dev/dm-1 469.00GiB
> /dev/mapper/data-linear1 469.00GiB
>
> Metadata,RAID1: Size:4.00GiB, Used:3.09GiB
> /dev/dm-1 4.00GiB
> /dev/mapper/data-linear1 4.00GiB
>
> System,RAID1: Size:32.00MiB, Used:112.00KiB
> /dev/dm-1 32.00MiB
> /dev/mapper/data-linear1 32.00MiB
>
> Unallocated:
> /dev/dm-1 406.97GiB
> /dev/mapper/data-linear1 406.97GiB
>
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