[dm-devel] Re: [2.6.22 PATCH 22/26] dm: bio list helpers

[Andrew Morton <akpm linux-foundation org>]

On Tue, 8 May 2007 20:48:45 +0100
Alasdair G Kergon <agk redhat com> wrote:

> +#define BIO_LIST_INIT { .head = NULL, .tail = NULL }
> +
> +#define BIO_LIST(bl) \
> +	struct bio_list bl = BIO_LIST_INIT

BIO_LIST is a strange name for something which initialises storage.

>  static inline void bio_list_init(struct bio_list *bl)
>  {
>  	bl->head = bl->tail = NULL;
>  }
>  
> +#define bio_list_for_each(bio, bl) \
> +	for (bio = (bl)->head; bio && ({ prefetch(bio->bi_next); 1; }); \
> +	     bio = bio->bi_next)
> +

I have this vague memory from a long time ago that one particular CPU type
wants to go oops when prefetching from an invalid address.

Maybe that went away for some reason - we'd have hit it again if it was
real.