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Date: Tue, 8 May 2007 17:41:59 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com, linux-kernel@vger.kernel.org,
       Heinz Mauelshagen <hjm@redhat.com>
Subject: Re: [2.6.22 PATCH 22/26] dm: bio list helpers
Message-Id: <20070508174159.7d78a275.akpm@linux-foundation.org>
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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.