Hi!
I upgraded one machine from 5.2.21 to 5.4.15, and one (freshly-created)
btrfs filesystem wrongly shows 0 avail in df after writing a bit of data:
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_ssd-data 6.5G 160M 0 100% /ssd
When at the same time, the filesystem should claim gobs of free space
(the df output corresponds to a time a bit earlier when not all data was
written yet):
Overall:
Device size: 6.00GiB
Device allocated: 0.63GiB
Device unallocated: 5.37GiB
Device missing: 0.00GiB
Used: 0.22GiB
Free (estimated): 5.77GiB (min: 5.77GiB)
Data ratio: 1.00
Metadata ratio: 1.00
Global reserve: 0.00GiB (used: 0.00GiB)
Data,single: Size:0.62GiB, Used:0.22GiB
/dev/mapper/vg_ssd-data 0.62GiB
Metadata,single: Size:0.01GiB, Used:0.00GiB
/dev/mapper/vg_ssd-data 0.01GiB
System,single: Size:0.00GiB, Used:0.00GiB
/dev/mapper/vg_ssd-data 0.00GiB
Unallocated:
/dev/mapper/vg_ssd-data 5.37GiB
This didn't happen under 5.2.21 for me, obviously.
Deleting some files makes the remaining space appear again, creating
them again changes to 0 free. I retried with a 76G partition but had
essentially the same results.
Only df output seems affected, the fs is still writable (I only realized
because apt told me the disk was full - the fs only stores apt package
lists and the apt cache).
When writing, this switch to 0 free happens suddenly (example with bigger
partition):
/dev/mapper/vg_ssd-data 76G 3.9M 76G 1% /ssd
/dev/mapper/vg_ssd-data 76G 3.9M 76G 1% /ssd
/dev/mapper/vg_ssd-data 76G 122M 76G 1% /ssd
/dev/mapper/vg_ssd-data 76G 201M 0 100% /ssd
/dev/mapper/vg_ssd-data 76G 244M 0 100% /ssd
Mount options are noatime,nossd,discard.
I see there were multiple reports for this and some discussion in december
(https://www.spinics.net/lists/linux-btrfs/msg95694.html), but apparently
nothing came of it and the bug still persists.
--
The choice of a Deliantra, the free code+content MORPG
-----==- _GNU_ http://www.deliantra.net
----==-- _ generation
---==---(_)__ __ ____ __ Marc Lehmann
--==---/ / _ \/ // /\ \/ / schmorp@xxxxxxxxxx
-=====/_/_//_/\_,_/ /_/\_\
