Date: Fri, 17 Jun 2011 17:34:15 +0200 From: Hans Ottevanger <hans@beastielabs.net> To: freebsd-current@freebsd.org Subject: SU+J: negative used diskspace (for a while) Message-ID: <20110617153415.GA92803@testsoekris.hotsoft.nl>
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Hi,
I found a possible issue with SU+J on recent versions of -CURRENT.
After deleting a large file hierarchy (copy of /usr/src, ~1.5 Gbyte),
df reports a negative number of blocks "Used" for a while.
I am using a GENERIC kernel (r223184) on an amd64 platform. The hardware
is relatively simple: Intel DP965LT mainboard with a Q6600 CPU, 8 Gbyte
RAM and two Samsung 501LJ 500 Gbyte SATA disks.
The issue can be demonstrated by copying /usr/src to the current directory
(cp -R /usr/src .) and running the following script to delete the copy
and print the free space at 10 second intervals:
#!/bin/sh
df .
time rm -rf src
echo 'src is gone ...'
while true
do
df . | tail -1
sleep 10
done
This yields the following output:
Filesystem 1K-blocks Used Avail Capacity Mounted on
/dev/ada0s1g 416144900 1612066 381241242 0% /home
51.21 real 1.00 user 17.38 sys
src is gone ...
/dev/ada0s1g 416144900 -164692 383018000 -0% /home
/dev/ada0s1g 416144900 -165082 383018390 -0% /home
/dev/ada0s1g 416144900 -246852 383100160 -0% /home
/dev/ada0s1g 416144900 -246852 383100160 -0% /home
/dev/ada0s1g 416144900 -246852 383100160 -0% /home
/dev/ada0s1g 416144900 -64146 382917454 -0% /home
/dev/ada0s1g 416144900 -64146 382917454 -0% /home
/dev/ada0s1g 416144900 -64146 382917454 -0% /home
/dev/ada0s1g 416144900 32910 382820398 0% /home
/dev/ada0s1g 416144900 32910 382820398 0% /home
So it takes more than a minute before the disk space is back to "normal"
values.
After disabling journaling (tunefs -j disable) I get the following output:
Filesystem 1K-blocks Used Avail Capacity Mounted on
/dev/ada0s1g 416144900 1579284 381274024 0% /home
35.40 real 0.96 user 13.32 sys
src is gone ...
/dev/ada0s1g 416144900 128 382853180 0% /home
/dev/ada0s1g 416144900 128 382853180 0% /home
/dev/ada0s1g 416144900 128 382853180 0% /home
/dev/ada0s1g 416144900 128 382853180 0% /home
which is as it should be.
The problem also does not occur with journaling enabled when I revert
to r222723.
Is anybody else seeing these weird phenomena?
Could this be related to the recent changes to UFS?
Kind regards,
Hans Ottevanger
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