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@xxxxxxxxxxxxxxxxxx> 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>