linux-kernel - Re: [PATCH 0/5] Add rbtree postorder iteration functions, runtime tests, and update zswap to use.

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Date:	Mon, 29 Jul 2013 10:11:04 -0500
From:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
To:	Cody P Schafer <cody@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>,
	David Woodhouse <David.Woodhouse@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Michel Lespinasse <walken@...gle.com>
Subject: Re: [PATCH 0/5] Add rbtree postorder iteration functions, runtime
 tests, and update zswap to use.

On Fri, Jul 26, 2013 at 02:13:38PM -0700, Cody P Schafer wrote:
> Postorder iteration yields all of a node's children prior to yielding the node
> itself, and this particular implementation also avoids examining the leaf links
> in a node after that node has been yielded.
> 
> In what I expect will be it's most common usage, postorder iteration allows the

s/it's/its/

> deletion of every node in an rbtree without modifying the rbtree nodes (no
> _requirement_ that they be nulled) while avoiding referencing child nodes after
> they have been "deleted" (most commonly, freed).
> 
> I have only updated zswap to use this functionality at this point, but numerous
> bits of code (most notably in the filesystem drivers) use a hand rolled
> postorder iteration that NULLs child links as it traverses the tree. Each of
> those instances could be replaced with this common implementation.

Thanks for doing this Cody!  Other than the nits I've sent, it looks
good.  Whole set:

Reviewed-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>

> 
> Cody P Schafer (5):
>   rbtree: add postorder iteration functions.
>   rbtree: add rbtree_postorder_for_each_entry_safe() helper.
>   rbtree_test: add test for postorder iteration.
>   rbtree: allow tests to run as builtin
>   mm/zswap: use postorder iteration when destroying rbtree
> 
>  include/linux/rbtree.h | 21 +++++++++++++++++++++
>  lib/Kconfig.debug      |  2 +-
>  lib/rbtree.c           | 40 ++++++++++++++++++++++++++++++++++++++++
>  lib/rbtree_test.c      | 12 ++++++++++++
>  mm/zswap.c             | 15 ++-------------
>  5 files changed, 76 insertions(+), 14 deletions(-)
> 
> -- 
> 1.8.3.4
> 

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