[Nbd] nbd and recent kernels (lock up of the clients ...)

[dsuchod <dsuchod@...65...>]

Hi!! I was testing the NBD with newer kernels again (had some problems 
with client hangs before and wanted to check if anything changed):

nbd hangs after a while, if not using the kernel command line option
"elevator=noop" (did not test other elevators yet). It hangs when using 
ext2 or squashfs (the latter has problems itself - it has to be patched so 
it does not get into troubles because of scheduler itself).

If the elevator option is given I did not encounter problems, at least for 
the tests I did (sent around 500MB over the net).

I'm using 2.8.3 of the user space tools and 2.6.13 and .16 kernels.

Ciao,
	Dirk