From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andreas Schwab <schwab@linux-m68k.org>
Subject: Re: [PATCH] fs: O_* bit numbers uniqueness check
Date: Wed, 06 Jan 2010 10:13:54 +0100
Message-ID: <m2iqbfwq7h.fsf@whitebox.home>
References: <20100106065526.GB11368@localhost> <4B443695.5090301@gmail.com>
	<20100106072029.GA25169@localhost>
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Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Miller <davem@davemloft.net>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@infradead.org>,
	Eric Paris <eparis@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"linux-fsdevel\@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
To: Wu Fengguang <fengguang.wu@intel.com>
Return-path: <linux-kernel-owner+glk-linux-kernel-3=40m.gmane.org-S1754453Ab0AIMjQ@vger.kernel.org>
In-Reply-To: <20100106072029.GA25169@localhost> (Wu Fengguang's message of
	"Wed, 6 Jan 2010 15:20:29 +0800")
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

Wu Fengguang <fengguang.wu@intel.com> writes:

> On Wed, Jan 06, 2010 at 03:07:01PM +0800, Eric Dumazet wrote:
>> Le 06/01/2010 07:55, Wu Fengguang a =C3=A9crit :
>> > The O_* bit numbers are defined in 20+ arch/*, and hence can silen=
tly
>> > overlap. Add a boot time check to ensure the uniqueness as suggest=
ed
>> > by David Miller.
>> >=20
>> > CC: David Miller <davem@davemloft.net>
>> > CC: Stephen Rothwell <sfr@canb.auug.org.au>
>> > CC: Al Viro <viro@zeniv.linux.org.uk>
>> > CC: Christoph Hellwig <hch@infradead.org>
>> > CC: Eric Paris <eparis@redhat.com>
>> > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
>> > ---
>> >  {
>> > +	/* please add new bits here to ensure allocation uniqueness */
>> > +	BUG_ON(20 !=3D hweight32(
>> > +		O_RDONLY	| O_WRONLY	| O_RDWR	|
>> > +		O_CREAT		| O_EXCL	| O_NOCTTY	|
>> > +		O_TRUNC		| O_APPEND	| O_NONBLOCK	|
>> > +		O_SYNC		| FASYNC	| O_DIRECT	|
>> > +		O_LARGEFILE	| O_DIRECTORY	| O_NOFOLLOW	|
>> > +		O_NOATIME	| O_CLOEXEC	| O_RANDOM	|
>> > +		FMODE_EXEC	| FMODE_NONOTIFY));
>> > +
>>=20
>> I cannot test it, but given O_RDONLY is 0, are you sure 20 bits are =
actually set ?
>
> Yes, I tested it. The tricky one is O_SYNC, which actually has two bi=
ts..

What if a new architecture wants to use a single bit value (since it
does not need backwards compatibility)?

Andreas.

--=20
Andreas Schwab, schwab@linux-m68k.org
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"And now for something completely different."