linux-kernel - Re: [PATCH] locks: rename file-private locks to file-description locks

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Message-ID: <53558A73.3010602@samba.org>
Date:	Mon, 21 Apr 2014 23:15:31 +0200
From:	"Stefan (metze) Metzmacher" <metze@...ba.org>
To:	Jeff Layton <jlayton@...hat.com>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
CC:	Rich Felker <dalias@...c.org>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, samba-technical@...ts.samba.org,
	Ganesha NFS List <nfs-ganesha-devel@...ts.sourceforge.net>,
	Carlos O'Donell <carlos@...hat.com>,
	libc-alpha <libc-alpha@...rceware.org>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH] locks: rename file-private locks to file-description
 locks

Am 21.04.2014 21:55, schrieb Jeff Layton:
> On Mon, 21 Apr 2014 21:39:12 +0200
> "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com> wrote:
> 
>> On 04/21/2014 08:46 PM, Rich Felker wrote:
>>> On Mon, Apr 21, 2014 at 08:32:44PM +0200, Michael Kerrisk (man-pages) wrote:
>>>> On 04/21/2014 06:10 PM, Rich Felker wrote:
>>>>> I'm well aware of that. The problem is that the proposed API is using
>>>>> the two-letter abbreviation FD, which ALWAYS means file descriptor and
>>>>> NEVER means file description (in existing usage) to mean file
>>>>> description. That's what's wrong.
>>>>
>>>> So, can you *please* answer this question: what do you call (i.e., 
>>>> what  everyday technical language term do use for) the thing
>>>> that sits between a file descriptor and an i-node? 
>>>>
>>>> (Please don't say 'struct file' -- that is not is an implementation 
>>>> detail, and does not qualify as the kind of term that I could use 
>>>> when documenting this feature in man pages.)
>>>
>>> "Open file description".
>>
>> Oh! I didn't realize we agreed :-).
>>
>>>> POSIX uses (or invented, I am not sure which) the term file description
>>>> for a good reason: it is unambiguous, and therefore precise. I do agree
>>>> that there's a risk of confusion between 'open file descriptor" and 
>>>> 'and file description'--it's the same kind of risk as between English 
>>>> terms such as 'arbitrator' and 'arbitration' (and any number of other
>>>> examples), and as language speakers we deal with this every day.
>>>
>>> There's not a problem when the full word is used. On the other hand,
>>> if you use "arb" as an abbreviation for "arbitration" in a context
>>> where it was already universally understood as meaning "arbitrator",
>>> that would be a big problem.
>>>
>>> Likewise the problem here isn't that "open file description" is a bad
>>> term. It's that using "FD" to mean "[open] file description" is
>>> utterly confusing, even moreso than just making up a new completely
>>> random word.
>>
>> Ohh -- I had thought you a problem not just with "FD" but also
>> "(open) file description".
>>
>>>>>> 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.
>>>>>
>>>>> I agree, but I don't think making it worse is a solution.
>>>>
>>>> I don't agree that it's making it worse. The real problem here is 
>>>> that people use no good unambiguous term for the thing between a file
>>>> descriptor and an inode. POSIX provides us with a solution that may
>>>> not seem perfect, but it is unambiguous, and I think it might feel
>>>> more comfortable if we used it often enough.
>>>
>>> I would like to see it used more too, and in particular, I think it
>>> belongs in the documentation for these new locking interfaces. But
>>> that still doesn't answer the question of what to call them (the
>>> macros) unless you want:
>>>
>>> F_OPEN_FILE_DESCRIPTION_GETLK
>>> F_OPEN_FILE_DESCRIPTION_SETLK
>>> F_OPEN_FILE_DESCRIPTION_SETLKW
>>
>> Or just 'F_OFD_*'?
>>
>>> Perhaps "OP" (for open-private, i.e. private to the particular open)
>>> would be a sensible choice; OTOH people are likely to misread it as
>>> OPeration. The general principle I have in mind though is that it
>>> might be nice to highlight the word "open" in "open file description"
>>
>> (Fair enough.)
>>
>>> since it (1) contrasts with file descriptor, despite file descriptors
>>> also dealing with open files, and (2) contrasts well with legacy fcntl
>>> locks, which are (this is the whole bug) associated with the
>>> underlying file and not the open file description.
>>
>> Makes sense to me. (We are in more agreement that I realized.)
>>
>> Cheers,
>>
>> Michael
>>
>>
>>
> 
> So the motion is to call them "open file description locks" and change
> the macros to read *_OFD_*. Does anyone object?

Works fine for me...

metze
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