Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757683AbaDWTN1 (ORCPT ); Wed, 23 Apr 2014 15:13:27 -0400 Received: from mail-lb0-f178.google.com ([209.85.217.178]:57077 "EHLO mail-lb0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754881AbaDWTNZ (ORCPT ); Wed, 23 Apr 2014 15:13:25 -0400 MIME-Version: 1.0 Reply-To: mtk.manpages@gmail.com In-Reply-To: References: <1398253172-9221-1-git-send-email-jlayton@redhat.com> <20140423112843.77889d16@tlielax.poochiereds.net> From: "Michael Kerrisk (man-pages)" Date: Wed, 23 Apr 2014 21:13:03 +0200 Message-ID: Subject: Re: [RFC][glibc PATCH] fcntl-linux.h: add new definitions and manual updates for open file description locks To: ams@gnu.org Cc: Jeff Layton , "libc-alpha@sourceware.org" , "linux-fsdevel@vger.kernel.org" , lkml , "Theodore Ts'o" , Rich Felker , samba-technical@lists.samba.org, Ganesha NFS List , "Carlos O'Donell" , "Stefan (metze) Metzmacher" , Christoph Hellwig , Boaz Harrosh Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 23, 2014 at 9:00 PM, Alfred M. Szmidt wrote: > > 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. I'm inclined to agree. > GETLK are used is to "get the first lock". > > 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). > > While I kinda see your point, it isn't what GETLK does; it really does > get you information about the first lock -- you're not testing > anything. It is also the terminology used in the POSIX standard. The POSIX wording is a little confused. For example, what does "first" mean in this context? F_GETLK returns information about one (arbitrarily selected) lock that blocks a lock you would like to place. So, I'm inclined to agree with Jeff -- this really is a "test" (or "can I lock it") operation. Of course, the operation has no reliable use: by the time it returns the information might already be out of date. I suspect that it was designed to solve the problem: "My F_GETLK operation failed. Who's blocking me?" Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/