trying to track down UFS "dup alloc" message on iSCSI

Andrew Snow andrew at
Fri Oct 3 05:27:49 UTC 2008

I am playing with an iSCSI device on FreeBSD client running UFS2 on the
device over a LAN.  Everything works well until I reboot the iSCSI
server - the client pauses for a minute or so then continues working
after iSCSI server comes back.  No I/O errors are reported.  Everything 
seems to work fine for a little while!

But shortly afterwards, I get a panic with the message

   panic: ffs_valloc: dup alloc

It seems related to the length of the delay the iSCSI device is paused -
restarting the iSCSI target daemon process doesn't cause the problem but 
rebooting the whole target box does cause it.

1. Could this be related to the patch Matt Dillon created years ago 
which I found here?

2. Can anyone think of any other reason this might happen?  I know I am
stretching UFS to the limits here, expecting it to pause and restart
after more than a minute of locked disk :-)  However, since all I/O 
eventually complete successfully and no errors are reported, I find it 


- Andrew

ps. running latest iSCSI code 2.1 on latest 7-STABLE box.

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