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From: Sven Eckelmann <sven@narfation.org>
Date: Fri, 19 Jun 2015 11:23:18 +0200
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Subject: Re: [B.A.T.M.A.N.] [PATCH] batman-adv: convert tt request list into
	hlist
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Cc: Marek Lindner <mareklindner@neomailbox.ch>


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On Friday 19 June 2015 15:09:18 Marek Lindner wrote:
> The tt request list does not require a double linked list, hence a
> conversion to hlist saves memory without losing functionality.
> 
> Also, the list_del() call was changed to hlist_del_init() to allow
> an adding an extra check prior to deletion in batadv_tt_req_node_new().
> 
> Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>

hlist_node is still double linked [1] (pprev is an "indirect" pointer to the
next pointer of the previous hlist_node in the list). The hlist_head is the
only one which has only one pointer. This is the reason why you can't add
things to the end of an hlist. But you can still add an hlist_node before
another hlist_node. This would be something which you could not do easily on a
"not double linked list"

Kind regards,
	Sven

[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/linux/list.h?id=a54acb3a6f853e8394c4cb7b6a4d93c88f13eefd#n588

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