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Explore advanced Linux kernel concepts in this 19-minute conference talk that addresses critical challenges in checkpoint/restore operations for processes with files open on unmounted mounts. Learn how CRIU (Checkpoint/Restore in Userspace) encounters difficulties when attempting to checkpoint and restore processes that have file descriptors open on mounts that have been unmounted using MNT_DETACH, as these "unmounted" mounts lack accessible mountinfo. Discover two potential solutions to extract mountinfo for these problematic mounts: implementing a special kernel-only unmount_mnt_ns where unmounted mounts can be stored and later queried using statmount(), and introducing fd-based statmount() functionality that allows passing file descriptors to statmount to retrieve mountinfo for the mount associated with the open file descriptor. Gain insights into the technical complexities of process checkpoint/restore mechanisms and proposed kernel-level solutions for handling edge cases in mount namespace management.
