Alright, I'm trying to classify this bug report as either user-mode or system-mode related. Let me go through the details step by step. The issue described involves using qemu-nbd to mount a virtual disk. The steps include loading an nbd module with modprobe, running qemu-nbd to connect the virtual disk to /dev/nbd0, then mounting the partition and copying a file. After unmounting and remounting, the copied file's MD5 sum changes, indicating corruption. I know that user-mode applications run with regular privileges and don't interact directly with hardware. System-mode issues usually involve lower-level components like drivers or kernel modules that require higher privileges. In this case, qemu-nbd is used to expose a virtual disk as a block device (/dev/nbd0), which requires root privileges because it's interacting with the kernel's block layer. Mounting and copying files involve the filesystem, but since the problem occurs at the block level (nbd) which interacts with the kernel, it's likely related to how the driver handles data transfers. The fact that partprobe is used suggests that the system is detecting partitions on a device, which is a low-level operation. The file corruption upon remounting implies issues in how the data was written or cached at a lower level than user applications. Considering all this, the problem seems to stem from how qemu-nbd interacts with the kernel's block layer rather than any user-space application. Therefore, it's more likely a system-mode issue. system