linux-kernel - Re: [PATCH v5 14/14] locks: add new fcntl cmd values for handling file private locks

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Message-ID: <20140109195527.2a86c7b7@tlielax.poochiereds.net>
Date:	Thu, 9 Jan 2014 19:55:27 -0500
From:	Jeff Layton <jlayton@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	linux-fsdevel@...r.kernel.org,
	nfs-ganesha-devel@...ts.sourceforge.net,
	samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 14/14] locks: add new fcntl cmd values for handling
 file private locks

On Thu, 09 Jan 2014 12:29:04 -0800
Andy Lutomirski <luto@...capital.net> wrote:

> On 01/09/2014 06:19 AM, Jeff Layton wrote:
> > Due to some unfortunate history, POSIX locks have very strange and
> > unhelpful semantics. The thing that usually catches people by surprise
> > is that they are dropped whenever the process closes any file descriptor
> > associated with the inode.
> > 
> 
> [...]
> 
> > +#define F_GETLKP	36
> > +#define F_SETLKP	37
> > +#define F_SETLKPW	38
> > +
> > +#ifndef CONFIG_64BIT
> > +#ifndef F_GETLK64
> > +#define F_GETLKP64	39
> > +#define F_SETLKP64	40
> > +#define F_SETLKPW64	41
> > +#endif
> > +#endif
> > +
> 
> Since there are no existing callers of these fcntls, can you get rid of
> the non-64-bit variants?  The implementation might be a bit more of
> departure from current code, but it should make everything a lot cleaner
> and make it easier (aka automatic) for new architectures to support this
> feature.
> 

That sounds reasonable, but I'll admit I had some trouble slogging
through the morass of fcntl/fcntl64 syscall handling code. I mostly did
the cargo-cult thing on this patch to get something that worked.

So, to make sure I understand...

You're basically suggesting that we just require that 32-bit userland
always use fcntl64() to access these new cmd values?

I'll try to do that, but I'll probably need someone to carefully review
what I come up with (hint, hint).

Thanks,
-- 
Jeff Layton <jlayton@...hat.com>
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