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 <sjenn...@linux.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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