Hello, I'm trying to build a block device with a small writable area (a loopback device) and a large read-only area full of zeroes. Stacking a read-only zero device doesn't work, because linear writes to it anyway (tested in 3.8.1, steps below). It seems to be a bug, but in case it isn't or can't be fixed, could one of the dm targets (linear, error, or zero) get a read-only flag that ensures that writes do fail? Test case: sudo dmsetup create --readonly --table '0 1024 zero' rozero sudo dmsetup create --table '0 1024 linear /dev/mapper/rozero 0' synthetic sudo dd if=/dev/urandom of=/dev/mapper/synthetic bs=512 count=1024 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
