I've got a btrfs filesystem that I can't seem to get back to a useful state. The symptom I started with is that rename() operations started dying with ENOSPC, and it looks like the metadata allocation on the filesystem is full: # btrfs fi df /broken Data, RAID0: total=3.63TiB, used=67.00GiB System, RAID1: total=8.00MiB, used=224.00KiB Metadata, RAID1: total=3.00GiB, used=2.50GiB GlobalReserve, single: total=512.00MiB, used=0.00B All of the consumable space on the backing devices also seems to be in use: # btrfs fi show /broken Label: 'mon_data' uuid: 85e52555-7d6d-4346-8b37-8278447eb590 Total devices 4 FS bytes used 69.50GiB devid 1 size 931.51GiB used 931.51GiB path /dev/sda1 devid 2 size 931.51GiB used 931.51GiB path /dev/sdb1 devid 3 size 931.51GiB used 931.51GiB path /dev/sdc1 devid 4 size 931.51GiB used 931.51GiB path /dev/sdd1 Even the smallest balance operation I can start fails (this doesn't change even with an extra temporary device added to the filesystem): # btrfs balance start -v -dusage=1 /broken Dumping filters: flags 0x1, state 0x0, force is off DATA (flags 0x2): balancing, usage=1 ERROR: error during balancing '/broken': No space left on device There may be more info in syslog - try dmesg | tail # dmesg | tail -1 [11554.296805] BTRFS info (device sdc1): 757 enospc errors during balance The current kernel is 4.15.0 from Debian's stretch-backports (specifically linux-image-4.15.0-0.bpo.2-amd64), but it was Debian's 4.9.30 when the filesystem got into this state. I upgraded it in the hopes that a newer kernel would be smarter, but no dice. btrfs-progs is currently at v4.7.3. Most of what this filesystem stores is Prometheus 1.8's TSDB for its metrics, which are constantly written at around 50MB/second. The filesystem never really gets full as far as data goes, but there's a lot of never-ending churn for what data is there. Question 1: Are there other steps that can be tried to rescue a filesystem in this state? I still have it mounted in the same state, and I'm willing to try other things or extract debugging info. Question 2: Is there something I could have done to prevent this from happening in the first place? Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
