linux-kernel - Re: [RFC][glibc PATCH] fcntl-linux.h: add new definitions and manual updates for open file description locks

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Date:	Wed, 23 Apr 2014 11:28:43 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	ams@....org
Cc:	libc-alpha@...rceware.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, tytso@....edu, dalias@...c.org,
	mtk.manpages@...il.com, samba-technical@...ts.samba.org,
	nfs-ganesha-devel@...ts.sourceforge.net, carlos@...hat.com,
	metze@...ba.org, hch@...radead.org, bharrosh@...asas.com
Subject: Re: [RFC][glibc PATCH] fcntl-linux.h: add new definitions and
 manual updates for open file description locks

On Wed, 23 Apr 2014 11:09:51 -0400
ams@....org (Alfred M. Szmidt) wrote:

>    @@ -2890,7 +2894,7 @@ Get flags associated with the open file.  @xref{File Status Flags}.
>     Set flags associated with the open file.  @xref{File Status Flags}.
> 
>     @item F_GETLK
>    -Get a file lock.  @xref{File Locks}.
>    +Test a file lock.  @xref{File Locks}.
> 
> F_GETLK does get the (first) lock which blocks; it doesn't test for
> it.  "Retrieves information about the first blocking lock ..." or
> something might be better than the original
> 
>    @@ -2898,6 +2902,18 @@ Set or clear a file lock.  @xref{File Locks}.
>     @item F_SETLKW
>     Like @code{F_SETLK}, but wait for completion.  @xref{File Locks}.
> 
>    +@...m F_OFD_GETLK
>    +Test a open file description lock.  @xref{Open File Description Locks}.
>    +Specific to Linux.
> 
> Likewise.  You infact write that it does get the lock information
> later in the document wrt. F_OFD_GETLK.

Sorry, I disagree here...GETLK is really a misnomer, IMO. TESTLK would
have been a better name.

It's a way to test whether a particular lock can be applied, and to
return information about a conflicting lock if it can't. If, for
instance there is no conflicting lock, then you don't "get" any lock
information back (l_type just gets reset to F_UNLCK).

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