[PATCH 01/20] rbtree: add const qualifier to some functions

[Praveen Kumar <kpraveen.lkml@gmail.com>]

The 'rb_first()', 'rb_last()', 'rb_next()' and 'rb_prev()' calls
take a pointer to an RB node or RB root. They do not change the
pointed objects, so add a 'const' qualifier in order to make life
of the users of these functions easier.

Indeed, if I have my own constant pointer &const struct my_type *p,
and I call 'rb_next(&p->rb)', I get a GCC warning:

warning: passing argument 1 of ‘rb_next’ discards qualifiers from pointer target
type

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[Linux commit f4b477c47332367d35686bd2b808c2156b96d7c7]

Ported to Xen.

Signed-off-by: Praveen Kumar <kpraveen.lkml@gmail.com>
---
 xen/common/rbtree.c      | 12 ++++++------
 xen/include/xen/rbtree.h |  8 ++++----
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/xen/common/rbtree.c b/xen/common/rbtree.c
index 3328960d56..d86b5f25c0 100644
--- a/xen/common/rbtree.c
+++ b/xen/common/rbtree.c
@@ -291,7 +291,7 @@ EXPORT_SYMBOL(rb_erase);
 /*
  * This function returns the first node (in sort order) of the tree.
  */
-struct rb_node *rb_first(struct rb_root *root)
+struct rb_node *rb_first(const struct rb_root *root)
 {
     struct rb_node *n;
 
@@ -304,7 +304,7 @@ struct rb_node *rb_first(struct rb_root *root)
 }
 EXPORT_SYMBOL(rb_first);
 
-struct rb_node *rb_last(struct rb_root *root)
+struct rb_node *rb_last(const struct rb_root *root)
 {
     struct rb_node *n;
 
@@ -317,7 +317,7 @@ struct rb_node *rb_last(struct rb_root *root)
 }
 EXPORT_SYMBOL(rb_last);
 
-struct rb_node *rb_next(struct rb_node *node)
+struct rb_node *rb_next(const struct rb_node *node)
 {
     struct rb_node *parent;
 
@@ -330,7 +330,7 @@ struct rb_node *rb_next(struct rb_node *node)
         node = node->rb_right; 
         while (node->rb_left)
             node=node->rb_left;
-        return node;
+        return (struct rb_node *)node;
     }
 
     /* No right-hand children.  Everything down and left is
@@ -346,7 +346,7 @@ struct rb_node *rb_next(struct rb_node *node)
 }
 EXPORT_SYMBOL(rb_next);
 
-struct rb_node *rb_prev(struct rb_node *node)
+struct rb_node *rb_prev(const struct rb_node *node)
 {
     struct rb_node *parent;
 
@@ -359,7 +359,7 @@ struct rb_node *rb_prev(struct rb_node *node)
         node = node->rb_left; 
         while (node->rb_right)
             node=node->rb_right;
-        return node;
+        return (struct rb_node *)node;
     }
 
     /* No left-hand children. Go up till we find an ancestor which
diff --git a/xen/include/xen/rbtree.h b/xen/include/xen/rbtree.h
index f93c4d5823..3eb527eb37 100644
--- a/xen/include/xen/rbtree.h
+++ b/xen/include/xen/rbtree.h
@@ -60,10 +60,10 @@ extern void rb_insert_color(struct rb_node *, struct rb_root *);
 extern void rb_erase(struct rb_node *, struct rb_root *);
 
 /* Find logical next and previous nodes in a tree */
-extern struct rb_node *rb_next(struct rb_node *);
-extern struct rb_node *rb_prev(struct rb_node *);
-extern struct rb_node *rb_first(struct rb_root *);
-extern struct rb_node *rb_last(struct rb_root *);
+extern struct rb_node *rb_next(const struct rb_node *);
+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 *);
 
 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new, 
-- 
2.12.0


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