nbd hangs in 2.6.21

[Rogier Wolff]

Hi,

I've been doing some work with nbd-servers, but it seems they are
a bit unreliable right now. It seems to be the kernel side that
is locking up. 

Doing things like 

dd if=/dev/zero of=filesys bs=1k count=1 seek=1024000
nbd-server 1234 `pwd`/filesys 

and then 

nbd-client othersystem 1234 /dev/nd0 
mke2fs /dev/nd0
mount /dev/nd0 /mnt
cp -r /usr/src/linux/ /mnt/test1
cp -r /usr/src/linux/ /mnt/test2
sync

will usually do the trick: The sync will hang in disk-wait and never
come out of it. 

In my case "othersystem" is running 2.6.20. I don't think it is
causing the problems: the nbd-server is simply waiting for the next
request. I also tried a different codebase: nbdsvr. Same thing. 

Anybody else see this?

	Roger. 

-- 
** R.E.Wolff@xxxxxxxxxxxx ** http://www.BitWizard.nl/ ** +31-15-2600998 **
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