Disk full during delayed allocation

[Jan Engelhardt]

Hi,


on space-constrained filesystems, I noticed that extracting lots of 
files [about 10k] bumps the Used count up quickly leading to a disk full 
unless the extraction process (rpm here) is halted, synced, and then 
continued. I believe this is fully within XFS's standard behavior, but I 
would like to learn more how exactly this can happen. My guess is that 
this is due to the "dynamic journal/log" size XFS employs - on a 
filesystem just mkfs'ed, about 4256KB (for a volume of 128MB) are used, 
compared to e.g. reiser3 where the full 32MB for the journal are used 
(according to df) right from the start.
Is this so?

# df; killall -CONT rpm; sleep 1; killall -STOP rpm; df; sync; df;
Filesystem           1K-blocks      Used Available Use% Mounted on
/lo/src.fs               93504     29396     64108  32% /usr/src
/lo/src.fs               93504     49072     44432  53% /usr/src
/lo/src.fs               93504     35632     57872  39% /usr/src