Re: [RFC][PATCH] ensure i_ino uniqueness in filesystems without permanent inode numbers (via pointer conversion)

[Matthew Wilcox <matthew@wil.cx>]

On Fri, Nov 17, 2006 at 08:43:00AM -0500, Jeff Layton wrote:
> +/* convert an inode address into an unsigned int and xor it with a random value
> + * determined at boot time */
> +static inline unsigned int inode_to_uint (struct inode *inode)
> +{
> +	return ((((unsigned long) (inode - (struct inode *) 0))
> +		 ^ inode_xor_mask) & 0xffffffff);
> +}

Seems a little obfuscated.  Why not simply:

	return ((unsigned long)inode ^ inode_xor_mask) & 0xffffffff;

> @@ -125,7 +135,6 @@ static struct inode *alloc_inode(struct 
>  		inode->i_size = 0;
>  		inode->i_blocks = 0;
>  		inode->i_bytes = 0;
> -		inode->i_generation = 0;
>  #ifdef CONFIG_QUOTA
>  		memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
>  #endif

It seems to me that filesystems with fake inodes could instead
initialise i_generation to, say, jiffies.  What do you think to that?

I like this idea, very creative.