[PATCH] locks: rename file-private locks to file-description locks

Michael Kerrisk (man-pages) mtk.manpages at gmail.com
Mon Apr 21 08:24:18 MDT 2014

On 04/21/2014 04:02 PM, Rich Felker wrote:
> On Mon, Apr 21, 2014 at 09:45:35AM -0400, Jeff Layton wrote:
>> File-private locks have been merged into Linux for v3.15, and *now*
>> people are commenting that the name and macro definitions for the new
>> file-private locks suck.
>> ....and I can't even disagree. The names and command macros do suck.
>> We're going to have to live with these for a long time, so it's
>> important that we be happy with the names before we're stuck with them.
>> The consensus on the lists so far is that they should be rechristened as
>> "file-description locks".
>> This patch makes the following changes that I think are necessary before
>> v3.15 ships:
>> 1) rename the command macros to their new names. These end up in the uapi
>>    headers and so are part of the external-facing API. It turns out that
>>    glibc doesn't actually use the fcntl.h uapi header, but it's hard to
>>    be sure that something else won't. Changing it now is safest.
>> 2) make the the /proc/locks output display these as type "FDLOCK"
>> The rest of the renaming can wait until v3.16, since everything else
>> isn't visible outside of the kernel.
> I'm sorry I didn't chime in on this earlier, but I really prefer the
> (somewhat bad) current naming ("private") to the
> ridiculously-confusing use of "FD" to mean "file descriptION" when
> everybody is used to it meaning "file descriptOR". The potential for
> confusion that these are "file descriptOR locks" (they're not) is much
> more of a problem, IMO, than the confusion about what "private" means
> (since it doesn't have an established meaning in this context.
> Thus my vote is for leaving things the way the kernel did it already.

There's at least two problems to solve here:

1) "File private locks" is _meaningless_ as a term. Elsewhere
   I suggested various alternatives. "File-handle locks [*]" was my
   initial preference, and I also suggested "file-description locks"
   and noted the drawbacks of that term. I think it's insufficient
   to say "stick with the existing poor name"--if you have
   something better, then please propose it. (Note by the way
   that for nearly a decade now, the open(2) man page has followed
   POSIX in using the term "open file description. Full disclosure:
   of course, I'm responsible for that change in the man page.)

2) The new API constants (F_SETLKP, F_SETLKPW, F_GETLKP) have names
   that are visually very close to the traditional POSIX lock names 
   (F_SETLK, F_SETLKW, F_GETLK). That's an accident waiting to happen
   when someone mistypes in code and/or misses such a misttyping
   when reading code. That really must be fixed.



[*] "File-handle locks" was considered by Jeff to be a little
confusing because of the term elsewhere, such as NFS. I take 
the point, though I'd still prefer it over "File-handle locks".

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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