Fcntl

fcntl OFD Locks Follow Open File Descriptions Instead of Processes

Traditional POSIX record locks have a property that can surprise code with several descriptors for the same file: lock ownership is associated with the process, and closing a descriptor for that file can release the process’s locks on it. Linux open file description locks move ownership to the kernel open file description referenced by a descriptor. The interface still uses fcntl() and struct flock, but the ownership boundary changes. F_OFD_SETLK, F_OFD_SETLKW, and F_OFD_GETLK make byte-range locking track the open file description rather than the process identity.