Hey. I just repeatedly did the following twice on a ~8GB USB stick, under Debian sid (ergo kernel 4.2.0-1-amd64, btrfsprogs 4.2.2-1).
First, created some GPT on the stick: Number Start (sector) End (sector) Size Code Name 1 2048 1048575 511.0 MiB EF02 BIOS boot partition 2 1048576 3145727 1024.0 MiB 8300 Linux filesystem 3 3145728 4194303 512.0 MiB 8300 Linux filesystem 4 4194304 6291455 1024.0 MiB 8300 Linux filesystem 5 6291456 15687644 4.5 GiB 8300 Linux filesystem Then filesystems: root@heisenberg:~# mkfs.btrfs --nodiscard --label boot-main /dev/sdb2 btrfs-progs v4.2.2 See http://btrfs.wiki.kernel.org for more information. Label: boot-main UUID: 150ee9fb-c650-4b5b-8f64-606e589e429a Node size: 16384 Sector size: 4096 Filesystem size: 1.00GiB Block group profiles: Data: single 8.00MiB Metadata: DUP 59.19MiB System: DUP 12.00MiB SSD detected: no Incompat features: extref, skinny-metadata Number of devices: 1 Devices: ID SIZE PATH 1 1.00GiB /dev/sdb2 root@heisenberg:~# mkfs.btrfs --nodiscard --label boot-data /dev/sdb3 btrfs-progs v4.2.2 See http://btrfs.wiki.kernel.org for more information. Label: boot-data UUID: b1c1fc77-c965-4f0c-a2b5-44a301fd8772 Node size: 16384 Sector size: 4096 Filesystem size: 1.00GiB Block group profiles: Data: single 8.00MiB Metadata: DUP 59.19MiB System: DUP 12.00MiB SSD detected: no Incompat features: extref, skinny-metadata Number of devices: 1 Devices: ID SIZE PATH 1 1.00GiB /dev/sdb3 root@heisenberg:~# mkfs.btrfs --nodiscard --label boot-archive /dev/sdb4 btrfs-progs v4.2.2 See http://btrfs.wiki.kernel.org for more information. Label: boot-archive UUID: a063cf3b-0322-4ec7-a8c1-2dabecad9f57 Node size: 16384 Sector size: 4096 Filesystem size: 1.00GiB Block group profiles: Data: single 8.00MiB Metadata: DUP 59.19MiB System: DUP 12.00MiB SSD detected: no Incompat features: extref, skinny-metadata Number of devices: 1 Devices: ID SIZE PATH 1 1.00GiB /dev/sdb4 root@heisenberg:~# mkfs.btrfs --nodiscard --label boot-rescue /dev/sdb5 btrfs-progs v4.2.2 See http://btrfs.wiki.kernel.org for more information. Label: boot-rescue UUID: 104b7bc3-3b8c-4a08-b0a6-9172ed664e68 Node size: 16384 Sector size: 4096 Filesystem size: 3.98GiB Block group profiles: Data: single 8.00MiB Metadata: DUP 211.75MiB System: DUP 12.00MiB SSD detected: no Incompat features: extref, skinny-metadata Number of devices: 1 Devices: ID SIZE PATH 1 3.98GiB /dev/sdb5 No errors in the kernel log. Then I got usage info: root@heisenberg:/data/SSS/boot# btrfs filesystem usage data/ Overall: Device size: 1.00GiB Device allocated: 126.38MiB Device unallocated: 897.62MiB Device missing: 0.00B Used: 256.00KiB Free (estimated): 905.62MiB (min: 456.81MiB) Data ratio: 1.00 Metadata ratio: 2.00 Global reserve: 16.00MiB (used: 0.00B) Data,single: Size:8.00MiB, Used:0.00B /dev/sdb3 8.00MiB Metadata,DUP: Size:51.19MiB, Used:112.00KiB /dev/sdb3 102.38MiB System,DUP: Size:8.00MiB, Used:16.00KiB /dev/sdb3 16.00MiB Unallocated: /dev/sdb3 897.62MiB root@heisenberg:/data/SSS/boot# btrfs filesystem usage main/ Overall: Device size: 1.00GiB Device allocated: 126.38MiB Device unallocated: 897.62MiB Device missing: 0.00B Used: 256.00KiB Free (estimated): 905.62MiB (min: 456.81MiB) Data ratio: 1.00 Metadata ratio: 2.00 Global reserve: 16.00MiB (used: 0.00B) Data,single: Size:8.00MiB, Used:0.00B /dev/sdb2 8.00MiB Metadata,DUP: Size:51.19MiB, Used:112.00KiB /dev/sdb2 102.38MiB System,DUP: Size:8.00MiB, Used:16.00KiB /dev/sdb2 16.00MiB Unallocated: /dev/sdb2 897.62MiB root@heisenberg:/data/SSS/boot# btrfs filesystem usage rescue/ Overall: Device size: 3.98GiB Device allocated: 431.50MiB Device unallocated: 3.56GiB Device missing: 0.00B Used: 320.00KiB Free (estimated): 3.57GiB (min: 1.79GiB) Data ratio: 1.00 Metadata ratio: 2.00 Global reserve: 16.00MiB (used: 0.00B) Data,single: Size:8.00MiB, Used:64.00KiB /dev/sdb5 8.00MiB Metadata,DUP: Size:203.75MiB, Used:112.00KiB /dev/sdb5 407.50MiB System,DUP: Size:8.00MiB, Used:16.00KiB /dev/sdb5 16.00MiB Unallocated: /dev/sdb5 3.56GiB Still all fine. Now I write to one of the filesystems (main at first, that still works) but then when I cp -a from another btrfs to data: cp: error writing ‘data/SHA512-sums.OLD’: No space left on device cp: failed to extend ‘data/SHA512-sums.OLD’: No space left on device cp: error writing ‘data/SHA512-sums’: No space left on device cp: failed to extend ‘data/SHA512-sums’: No space left on device (these files are just a few bytes large) On the target fs, they're there but all 0 bytes large. (btw: I've aliased cp to cp --reflink=auto When I now repeat the usage info: root@heisenberg:/data/SSS/boot# btrfs filesystem usage data Overall: Device size: 1.00GiB Device allocated: 118.38MiB Device unallocated: 905.62MiB Device missing: 0.00B Used: 256.00KiB Free (estimated): 8.00EiB (min: 8.00EiB) Data ratio: -nan Metadata ratio: 2.00 Global reserve: 16.00MiB (used: 0.00B) Metadata,DUP: Size:51.19MiB, Used:112.00KiB /dev/sdc3 102.38MiB System,DUP: Size:8.00MiB, Used:16.00KiB /dev/sdc3 16.00MiB Unallocated: /dev/sdc3 905.62MiB It get's bogus... at least the Free space shows 8 EiB (if wishes were horses)... Still no error in kernel logs: 3401.934514] BTRFS: device label boot-rescue devid 1 transid 8 /dev/sdc5 [ 3401.985858] BTRFS: device label boot-main devid 1 transid 8 /dev/sdc2 [ 3401.988601] BTRFS: device label boot-data devid 1 transid 9 /dev/sdc3 [ 3401.997370] BTRFS: device label boot-archive devid 1 transid 9 /dev/sdc4 [ 3403.721091] BTRFS info (device sdc3): disk space caching is enabled [ 3403.721098] BTRFS: has skinny extents [ 3413.964033] BTRFS info (device sdb3): disk space caching is enabled [ 3413.964042] BTRFS: has skinny extents [ 3522.902309] BTRFS info (device sdb3): disk space caching is enabled [ 3522.902314] BTRFS: has skinny extents [ 3525.055653] BTRFS info (device sdc3): disk space caching is enabled [ 3525.055659] BTRFS: has skinny extents btrfs check doesn't show errors either. After a balance, i can copy again, even though the usage still shows 8 EiB for a while... Anyway how can it happen, that on a fresh btrfs with no files at all a balance is necessary? Or is there some deeper corruption going on here? Thanks, Chris.
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