Comment 51 for bug 1023755

FYI i could reproduce a hang in dd doing the following:

truncate -s 1G foo
sudo losetup -f --show foo
echo "0 2097152 zero" | sudo dmsetup create zero1
echo "0 2097152 snapshot /dev/mapper/zero1 /dev/loop0 n 128" | sudo dmsetup create clean1
sudo dd if=/dev/zero of=/dev/mapper/clean1 bs=1M count=1024

Using strace, the command hangs partway through:

read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576) = 1048576
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576

I can ctrl-c out of strace but the resulting dd process is completely hung and unkillalble

Note that this is running in a (vmware fusion) vm.