From 9dee5c51516d2c3fff22633c1272c5652e68075a Mon Sep 17 00:00:00 2001 From: Cody P Schafer Date: Wed, 11 Sep 2013 14:25:10 -0700 Subject: rbtree: add postorder iteration functions 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. This patch: Add postorder iteration functions for rbtree. These are useful for safely freeing an entire rbtree without modifying the tree at all. Signed-off-by: Cody P Schafer Reviewed-by: Seth Jennings Cc: David Woodhouse Cc: Rik van Riel Cc: Michel Lespinasse Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/rbtree.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/rbtree.h') diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h index 0022c1bb1e26..c467151e9950 100644 --- a/include/linux/rbtree.h +++ b/include/linux/rbtree.h @@ -68,6 +68,10 @@ extern struct rb_node *rb_prev(const struct rb_node *); extern struct rb_node *rb_first(const struct rb_root *); extern struct rb_node *rb_last(const struct rb_root *); +/* Postorder iteration - always visit the parent after its children */ +extern struct rb_node *rb_first_postorder(const struct rb_root *); +extern struct rb_node *rb_next_postorder(const struct rb_node *); + /* Fast replacement of a single node without remove/rebalance/add/rebalance */ extern void rb_replace_node(struct rb_node *victim, struct rb_node *new, struct rb_root *root); -- cgit v1.2.3 From 2b529089257705499207ce7da9d0e3ae26a844ba Mon Sep 17 00:00:00 2001 From: Cody P Schafer Date: Wed, 11 Sep 2013 14:25:11 -0700 Subject: rbtree: add rbtree_postorder_for_each_entry_safe() helper Because deletion (of the entire tree) is a relatively common use of the rbtree_postorder iteration, and because doing it safely means fiddling with temporary storage, provide a helper to simplify postorder rbtree iteration. Signed-off-by: Cody P Schafer Reviewed-by: Seth Jennings Cc: David Woodhouse Cc: Rik van Riel Cc: Michel Lespinasse Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/rbtree.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'include/linux/rbtree.h') diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h index c467151e9950..aa870a4ddf54 100644 --- a/include/linux/rbtree.h +++ b/include/linux/rbtree.h @@ -85,4 +85,22 @@ static inline void rb_link_node(struct rb_node * node, struct rb_node * parent, *rb_link = node; } +/** + * rbtree_postorder_for_each_entry_safe - iterate over rb_root in post order of + * given type safe against removal of rb_node entry + * + * @pos: the 'type *' to use as a loop cursor. + * @n: another 'type *' to use as temporary storage + * @root: 'rb_root *' of the rbtree. + * @field: the name of the rb_node field within 'type'. + */ +#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \ + for (pos = rb_entry(rb_first_postorder(root), typeof(*pos), field),\ + n = rb_entry(rb_next_postorder(&pos->field), \ + typeof(*pos), field); \ + &pos->field; \ + pos = n, \ + n = rb_entry(rb_next_postorder(&pos->field), \ + typeof(*pos), field)) + #endif /* _LINUX_RBTREE_H */ -- cgit v1.2.3