It may be worth a discussion of whether linkat() could be given a flag to
allow the destination to be replaced or if a new syscall should be made for
this - or whether it should be disallowed entirely.
A set of patches has been posted by Omar Sandoval that makes this possible:
https://lore.kernel.org/linux-fsdevel/cover.1524549513.git.osandov@xxxxxx/
though it only includes filesystem support for btrfs.
This could be useful for cachefiles:
https://lore.kernel.org/linux-fsdevel/3326.1579019665@xxxxxxxxxxxxxxxxxxxxxx/
and overlayfs.
David
