linux-kernel - Support for applications which need NFS or CIFS "share

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Date:	Tue, 2 Dec 2008 10:31:20 -0600
From:	"Steve French" <smfrench@...il.com>
To:	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-cifs-client@...ts.samba.org" 
	<linux-cifs-client@...ts.samba.org>
Subject: Support for applications which need NFS or CIFS "share_deny" flags on open

Some of the Wine community posted last month to the cifs mailing list
asking about a change needed for Wine for working properly over
network mounts, but the change is not really cifs specific and would
help other file systems as well so I wanted to mention it here.   The
original post was:
http://marc.info/?l=linux-cifs-client&m=122505569315992&w=2

Support for the flags they suggest would be easy for cifs (the
protocol has a field for this, and cifs clients on various other OS
set it), and should be fairly easy for NFSv4 (the RFC for NFSv4
specifies the "share_deny" field within the NFS open request, and
various clients, but not Linux, set it), and would allow WINE to
function properly over a network mount.

>we proffer to add into the file /usr/include/asm-generic/fcntl.h
> following flags:
>
>#define O_DENYREAD      004000000 /* Do not permit read access */
>#define O_DENYWRITE     010000000 /* Do not permit write access */
>#define O_DENYDELETE  020000000 /* Do not permit delete or rename
> operations*/

Presumably for applications on local mounts, wine mediates their own
mandatory locks, but this is impossible on network mounts without this
change (and can lead to data corruption).

-- 
Thanks,

Steve
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