OFD ("file private") locks and NFS

Michael Kerrisk (man-pages) mtk.manpages at gmail.com
Tue Apr 29 02:38:54 MDT 2014

Hi Jeff,

I've been looking a bit at the fcntl() documentation of traditional 
(F_SETLK) record locking, and a question just jumped out at me. Is 
it worth considering some future-proofing in the design of OFD locks
("open file description locks", formerly known as "file-private locks")?

What I am thinking of here is that on some systems, the traditional
'struct flock' has a nonstandard field, l_sysid, that is used on F_GETLK 
to identify the remote system on which a lock is held. Should the design
of OFD locks allow for such a field (now, or in the future), which might 
be useful in the context of locking on network file systems such as NFS.

Put more simply, should the new OFD locking system be using a new
structure for describing locks, rather than the traditional 'struct
flock'? Defining a new structure, might be useful to allow for
future extensions to the API.



Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/

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