From: Praveen Kumar <kpraveen.lkml@gmail.com>
To: xen-devel@lists.xen.org
Cc: sstabellini@kernel.org, wei.liu2@citrix.com,
George.Dunlap@eu.citrix.com, andrew.cooper3@citrix.com,
dario.faggioli@citrix.com, ian.jackson@eu.citrix.com,
tim@xen.org, Praveen Kumar <kpraveen.lkml@gmail.com>,
jbeulich@suse.com
Subject: [Resend][PATCH 17/17] rbtree: add postorder iteration functions
Date: Thu, 1 Jun 2017 02:50:56 +0530 [thread overview]
Message-ID: <20170531212056.10583-18-kpraveen.lkml@gmail.com> (raw)
In-Reply-To: <20170531212056.10583-1-kpraveen.lkml@gmail.com>
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.
commit 9dee5c51516d2c3fff22633c1272c5652e68075a from Linux tree
Signed-off-by: Praveen Kumar <kpraveen.lkml@gmail.com>
---
xen/common/rbtree.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
xen/include/xen/rbtree.h | 4 ++++
2 files changed, 49 insertions(+)
diff --git a/xen/common/rbtree.c b/xen/common/rbtree.c
index 83b4892f54..3c994dcc0c 100644
--- a/xen/common/rbtree.c
+++ b/xen/common/rbtree.c
@@ -584,3 +584,48 @@ void rb_replace_node(struct rb_node *victim, struct rb_node *new,
*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);
+
diff --git a/xen/include/xen/rbtree.h b/xen/include/xen/rbtree.h
index 107f1b12f2..24650a5cd8 100644
--- a/xen/include/xen/rbtree.h
+++ b/xen/include/xen/rbtree.h
@@ -66,4 +66,8 @@ static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
*rb_link = node;
}
+/* 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 *);
+
#endif /* __RBTREE_H__ */
--
2.12.0
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next prev parent reply other threads:[~2017-05-31 21:20 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-31 21:20 [Xen-devel[PATCH Resend v2] xen: common: rbtree: ported updates from linux tree Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 01/17] rb_tree: reorganize code in rb_erase() for additional changes Praveen Kumar
2017-05-31 22:40 ` Dario Faggioli
2017-05-31 22:56 ` Andrew Cooper
2017-06-01 8:01 ` Dario Faggioli
2017-06-02 16:28 ` Praveen Kumar
2017-06-08 15:57 ` Jan Beulich
2017-05-31 21:20 ` [Resend][PATCH 02/17] rb_tree: make clear distinction between two different cases in rb_erase() Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 03/17] rb_tree: remove redundant if()-condition " Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 04/17] rbtree: empty nodes have no color Praveen Kumar
2017-06-12 16:42 ` Dario Faggioli
2017-06-13 8:21 ` Jan Beulich
2017-05-31 21:20 ` [Resend][PATCH 05/17] rbtree: move some implementation details from rbtree.h to rbtree.c Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 06/17] rbtree: break out of rb_insert_color loop after tree rotation Praveen Kumar
2017-06-12 16:41 ` Dario Faggioli
2017-05-31 21:20 ` [Resend][PATCH 07/17] rbtree: adjust root color in rb_insert_color() only when necessary Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 08/17] rbtree: low level optimizations in rb_insert_color() Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 09/17] rbtree: adjust node color in __rb_erase_color() only when necessary Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 10/17] rbtree: optimize case selection logic in __rb_erase_color() Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 11/17] rbtree: low level optimizations " Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 12/17] rbtree: optimize fetching of sibling node Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 13/17] rbtree: add __rb_change_child() helper function Praveen Kumar
2017-06-12 16:14 ` Dario Faggioli
2017-05-31 21:20 ` [Resend][PATCH 14/17] rbtree: place easiest case first in rb_erase() Praveen Kumar
2017-06-12 16:19 ` Dario Faggioli
2017-05-31 21:20 ` [Resend][PATCH 15/17] rbtree: handle 1-child recoloring in rb_erase() instead of rb_erase_color() Praveen Kumar
2017-05-31 21:20 ` [Resend][PATCH 16/17] rbtree: low level optimizations in rb_erase() Praveen Kumar
2017-05-31 21:20 ` Praveen Kumar [this message]
2017-05-31 22:34 ` [Xen-devel[PATCH Resend v2] xen: common: rbtree: ported updates from linux tree Dario Faggioli
2017-06-01 7:26 ` Jan Beulich
2017-06-01 7:43 ` Dario Faggioli
2017-06-02 16:35 ` Praveen Kumar
2017-06-02 16:31 ` Praveen Kumar
2017-06-12 16:44 ` Dario Faggioli
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