>Number:         15555
>Category:       kern
>Synopsis:       nullfs is slow to flush certain changes
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Feb 09 14:50:00 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Christophe Kalt
>Release:        1.5.1, kernel may be a little more recent
>Organization:
	
>Environment:
	
System: NetBSD zh.taranis.org 1.5.1 NetBSD 1.5.1 (XPSH) #1: Sat Jul 7 15:27:33 EDT 2001 root@zh.taranis.org:/usr/src/sys/arch/i386/compile/XPSH i386


>Description:
when deleting files, space is not reclaimed as quickly as it should.
i've noticed it times and times again when filling up a partition,
trying to free up space by deleting files only to find that i have
to wait *minutes* (5, 10 sometimes) to be able to get space freed.

i'm including below an example using mfs as the underlying filesystem,
not that i believe it to matter.

anyhow, you will notice that unmounting the nullfs will force things.
>How-To-Repeat:
# mount -t mfs -o rw,-s1024 swap /mnt
# mkdir /mnt2
# mount -t null /mnt /mnt2
# df -k /mnt /mnt2
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
mfs:655           463        1      438     0%    /mnt
/mnt              463        1      438     0%    /mnt2
# cat /dev/zero > /mnt2/oink

/mnt: write failed, file system is full
cat: stdout: No space left on device
# df -k /mnt /mnt2
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
mfs:655           463      449      -10   102%    /mnt
/mnt              463      449      -10   102%    /mnt2
# date
Sat Feb  9 17:30:14 EST 2002
# ls -l /mnt /mnt2
/mnt:

/mnt2:
# sync;sync;sync;sync
# df -k /mnt /mnt2
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
mfs:655           463      449      -10   102%    /mnt
/mnt              463      449      -10   102%    /mnt2
# date; df -k /mnt /mnt2
Sat Feb  9 17:33:24 EST 2002
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
mfs:655           463      449      -10   102%    /mnt
/mnt              463      449      -10   102%    /mnt2
# umount /mnt2
# df -k /mnt
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
mfs:655           463        1      438     0%    /mnt
>Fix:
	
>Release-Note:
>Audit-Trail:
>Unformatted: