Subject: + rbtree-add-postorder-iteration-functions.patch added to -mm tree
To: cody@xxxxxxxxxxxxxxxxxx,David.Woodhouse@xxxxxxxxx,riel@xxxxxxxxxx,sjenning@xxxxxxxxxxxxxxxxxx,walken@xxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Mon, 29 Jul 2013 15:43:55 -0700
The patch titled
Subject: rbtree: add postorder iteration functions
has been added to the -mm tree. Its filename is
rbtree-add-postorder-iteration-functions.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/rbtree-add-postorder-iteration-functions.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/rbtree-add-postorder-iteration-functions.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
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 <cody@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
Cc: David Woodhouse <David.Woodhouse@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/rbtree.h | 4 +++
lib/rbtree.c | 40 +++++++++++++++++++++++++++++++++++++++
2 files changed, 44 insertions(+)
diff -puN include/linux/rbtree.h~rbtree-add-postorder-iteration-functions include/linux/rbtree.h
--- a/include/linux/rbtree.h~rbtree-add-postorder-iteration-functions
+++ a/include/linux/rbtree.h
@@ -68,6 +68,10 @@ extern struct rb_node *rb_prev(const str
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);
diff -puN lib/rbtree.c~rbtree-add-postorder-iteration-functions lib/rbtree.c
--- a/lib/rbtree.c~rbtree-add-postorder-iteration-functions
+++ a/lib/rbtree.c
@@ -518,3 +518,43 @@ void rb_replace_node(struct rb_node *vic
*new = *victim;
}
EXPORT_SYMBOL(rb_replace_node);
+
+static struct rb_node *rb_left_deepest_node(const struct rb_node *node)
+{
+ for (;;) {
+ if (node->rb_left)
+ node = node->rb_left;
+ else if (node->rb_right)
+ node = node->rb_right;
+ else
+ return (struct rb_node *)node;
+ }
+}
+
+struct rb_node *rb_next_postorder(const struct rb_node *node)
+{
+ const struct rb_node *parent;
+ if (!node)
+ return NULL;
+ parent = rb_parent(node);
+
+ /* If we're sitting on node, we've already seen our children */
+ if (parent && node == parent->rb_left && parent->rb_right) {
+ /* If we are the parent's left node, go to the parent's right
+ * node then all the way down to the left */
+ return rb_left_deepest_node(parent->rb_right);
+ } else
+ /* Otherwise we are the parent's right node, and the parent
+ * should be next */
+ return (struct rb_node *)parent;
+}
+EXPORT_SYMBOL(rb_next_postorder);
+
+struct rb_node *rb_first_postorder(const struct rb_root *root)
+{
+ if (!root->rb_node)
+ return NULL;
+
+ return rb_left_deepest_node(root->rb_node);
+}
+EXPORT_SYMBOL(rb_first_postorder);
_
Patches currently in -mm which might be from cody@xxxxxxxxxxxxxxxxxx are
mm-page_alloc-restructure-free-page-stealing-code-and-fix-a-bug.patch
mm-page_alloc-restructure-free-page-stealing-code-and-fix-a-bug-fix.patch
mm-fix-the-value-of-fallback_migratetype-in-alloc_extfrag-tracepoint.patch
rbtree-add-postorder-iteration-functions.patch
rbtree-add-rbtree_postorder_for_each_entry_safe-helper.patch
rbtree_test-add-test-for-postorder-iteration.patch
rbtree-allow-tests-to-run-as-builtin.patch
mm-zswap-use-postorder-iteration-when-destroying-rbtree.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
