Re: [patch 4/6] vfs: O_* bit numbers uniqueness check

[Eric Paris <eparis@redhat.com>]

On Thu, 2010-03-11 at 14:11 -0800, akpm@linux-foundation.org wrote:
> From: Wu Fengguang <fengguang.wu@intel.com>
> 
> The O_* bit numbers are defined in 20+ arch/*, and can silently overlap. 
> Add a compile time check to ensure the uniqueness as suggested by David
> Miller.

Until the FMODE_ and O_ bits do not overload I think we need to check
FMODE_EXEC and FMODE_NONOTIFY (if you have that one) inside fcntl_init()
as well.  I guess I'll send a patch to someone ?Al? to add FMODE_EXEC to
the list....

-Eric

> 
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> 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>
> Cc: Roland Dreier <rdreier@cisco.com>
> Cc: Jamie Lokier <jamie@shareable.org>
> Cc: Andreas Schwab <schwab@linux-m68k.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  fs/fcntl.c                  |   14 ++++++++++++--
>  include/asm-generic/fcntl.h |    2 ++
>  2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff -puN fs/fcntl.c~vfs-o_-bit-numbers-uniqueness-check fs/fcntl.c
> --- a/fs/fcntl.c~vfs-o_-bit-numbers-uniqueness-check
> +++ a/fs/fcntl.c
> @@ -739,11 +739,21 @@ void kill_fasync(struct fasync_struct **
>  }
>  EXPORT_SYMBOL(kill_fasync);
>  
> -static int __init fasync_init(void)
> +static int __init fcntl_init(void)
>  {
> +	/* please add new bits here to ensure allocation uniqueness */
> +	BUILD_BUG_ON(17 != HWEIGHT32(
> +		O_RDONLY	| O_WRONLY	| O_RDWR	|
> +		O_CREAT		| O_EXCL	| O_NOCTTY	|
> +		O_TRUNC		| O_APPEND	| O_NONBLOCK	|
> +		__O_SYNC	| O_DSYNC	| FASYNC	|
> +		O_DIRECT	| O_LARGEFILE	| O_DIRECTORY	|
> +		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC
> +		));
> +
>  	fasync_cache = kmem_cache_create("fasync_cache",
>  		sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
>  	return 0;
>  }
>  
> -module_init(fasync_init)
> +module_init(fcntl_init)
> diff -puN include/asm-generic/fcntl.h~vfs-o_-bit-numbers-uniqueness-check include/asm-generic/fcntl.h
> --- a/include/asm-generic/fcntl.h~vfs-o_-bit-numbers-uniqueness-check
> +++ a/include/asm-generic/fcntl.h
> @@ -4,6 +4,8 @@
>  #include <linux/types.h>
>  
>  /*
> + * When introducing new O_* bits, please check its uniqueness in fcntl_init().
> + *
>   * FMODE_EXEC is 0x20
>   * FMODE_NONOTIFY is 0x1000000
>   * These cannot be used by userspace O_* until internal and external open
> _