Re: [PATCH] fs: O_* bit numbers uniqueness check

[Wu Fengguang <fengguang.wu@intel.com>]

On Wed, Jan 06, 2010 at 05:13:54PM +0800, Andreas Schwab wrote:
> 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 écrit :
> >> > The O_* bit numbers are defined in 20+ arch/*, and hence can silently
> >> > overlap. Add a boot time check to ensure the uniqueness as suggested
> >> > by David Miller.
> >> > 
> >> > 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 != 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));
> >> > +
> >> 
> >> 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 bits..
> 
> What if a new architecture wants to use a single bit value (since it
> does not need backwards compatibility)?

You mean to test __O_SYNC | O_DSYNC instead of O_SYNC?