linux-kernel - [PATCH v2 0/5] Add rbtree postorder iteration functions, runtime tests, and update zswap to use

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Date:	Mon, 29 Jul 2013 12:19:25 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	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>,
	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>
Subject: [PATCH v2 0/5] Add rbtree postorder iteration functions, runtime tests, and update zswap to use

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 its most common usage, postorder iteration allows the
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.

1 & 2 add rbtree postorder iteration functions.
3 adds testing of the iteration to the rbtree runtime tests
4 allows building the rbtree runtime tests as builtins
5 updates zswap.

--
since v1:
	- spacing
	- s/it's/its/
	- remove now unused var in zswap code.
	- 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 | 22 ++++++++++++++++++++++
 lib/Kconfig.debug      |  2 +-
 lib/rbtree.c           | 40 ++++++++++++++++++++++++++++++++++++++++
 lib/rbtree_test.c      | 12 ++++++++++++
 mm/zswap.c             | 16 ++--------------
 5 files changed, 77 insertions(+), 15 deletions(-)

-- 
1.8.3.4

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