Re: [PATCH] reduce sizeof(struct file)

[Nick Piggin <nickpiggin@yahoo.com.au>]

Eric Dumazet wrote:

> --- linux-2.6.14-rc2-orig/include/linux/fs.h	2005-09-20 05:00:41.000000000 +0200
> +++ linux-2.6.14-rc2/include/linux/fs.h	2005-09-24 04:52:20.000000000 +0200
> @@ -574,7 +574,13 @@
>  #define RA_FLAG_INCACHE 0x02	/* file is already in cache */
>  
>  struct file {
> -	struct list_head	f_list;
> +/*
> + * f_list and f_rcuhead can share the same memory location
> + */
> +	union {
> +		struct list_head	fu_list;
> +		struct rcu_head 	fu_rcuhead;
> +		} f_u;

I don't think you need to explain this basic C semantic to
the reader if they have gotten this far ;)

Instead, explain when fu_list and fu_rcuhead are used.
Something along the lines of

/*
 * fu_list becomes invalid after file_free is called
 * and queued via fu_rcuhead for RCU freeing
 */

Nick

--
SUSE Labs, Novell Inc.

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