[Devel] Re: [PATCH] Introduce a handy list_first_entry macro

[Zach Brown]

On Tue, Apr 17, 2007 at 03:18:56PM +0400, Pavel Emelianov wrote:
> There are many places in the kernel where the construction like
> 
>    foo = list_entry(head->next, struct foo_struct, list);
> 
> are used. 
> The code might look more descriptive and neat if using the macro
> 
>    list_first_entry(head, type, member) \
>              list_entry((head)->next, type, member)

> -			dquot = list_entry(dirty->next, struct dquot, dq_dirty);
> +			dquot = list_first_entry(dirty, struct dquot, dq_dirty);

I think it's more than just descriptive and neat.  A common sneaky bug
is to accidentally pass &list->next into list_entry() instead of
list->next. This is easy to do because one is used to typing &list in
list_empty(), etc.  So by following ->next in the macro we make the list
argument consistent in list_empty() and list_first_entry() and hopefully
reduce the risk of making that mistake.

I like it.

- z