From: Eric Dumazet <edumazet@google.com>
Date: Fri, 14 Nov 2025 14:06:45 +0000 (+0000)
Subject: rbtree: inline rb_first()
X-Git-Tag: v6.19-rc1~70^2~56
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c2d2dad24503d7e2eb7cba354fcc73f95fa78d7a;p=thirdparty%2Flinux.git

rbtree: inline rb_first()

Patch series "rbree: inline rb_first() and rb_last()".

Inline these two small helpers, heavily used in TCP and FQ packet scheduler,
and in many other places.

This reduces kernel text size, and brings an 1.5 % improvement on network
TCP stress test.


This patch (of 2):

This is a very small function, inlining it saves cpu cycles by reducing
register pressure and removing call/ret overhead.

It also reduces vmlinux text size by 744 bytes on a typical x86_64 build.

Before:

size vmlinux
   text	   data	    bss	    dec	    hex	filename
34812525	22177365	5685248	62675138	3bc58c2	vmlinux

After:

size vmlinux
   text	   data	    bss	    dec	    hex	filename
34811781	22177365	5685248	62674394	3bc55da	vmlinux

[ojeda@kernel.org: fix rust build]
  Link: https://lkml.kernel.org/r/20251120085518.1463498-1-ojeda@kernel.org
Link: https://lkml.kernel.org/r/20251114140646.3817319-1-edumazet@google.com
Link: https://lkml.kernel.org/r/20251114140646.3817319-2-edumazet@google.com
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Cc: Jakub Kacinski <kuba@kernel.org>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Stehen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h
index 8d2ba3749866f..484554900f7d3 100644
--- a/include/linux/rbtree.h
+++ b/include/linux/rbtree.h
@@ -43,7 +43,21 @@ 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(const struct rb_node *);
 extern struct rb_node *rb_prev(const struct rb_node *);
-extern struct rb_node *rb_first(const struct rb_root *);
+
+/*
+ * This function returns the first node (in sort order) of the tree.
+ */
+static inline struct rb_node *rb_first(const struct rb_root *root)
+{
+	struct rb_node	*n;
+
+	n = root->rb_node;
+	if (!n)
+		return NULL;
+	while (n->rb_left)
+		n = n->rb_left;
+	return n;
+}
 extern struct rb_node *rb_last(const struct rb_root *);
 
 /* Postorder iteration - always visit the parent after its children */
diff --git a/lib/rbtree.c b/lib/rbtree.c
index 5114eda6309c9..b946eb4b759d3 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -460,22 +460,6 @@ void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
 }
 EXPORT_SYMBOL(__rb_insert_augmented);
 
-/*
- * This function returns the first node (in sort order) of the tree.
- */
-struct rb_node *rb_first(const struct rb_root *root)
-{
-	struct rb_node	*n;
-
-	n = root->rb_node;
-	if (!n)
-		return NULL;
-	while (n->rb_left)
-		n = n->rb_left;
-	return n;
-}
-EXPORT_SYMBOL(rb_first);
-
 struct rb_node *rb_last(const struct rb_root *root)
 {
 	struct rb_node	*n;
diff --git a/rust/helpers/rbtree.c b/rust/helpers/rbtree.c
index 6d404b84a9b53..d0e452234632a 100644
--- a/rust/helpers/rbtree.c
+++ b/rust/helpers/rbtree.c
@@ -7,3 +7,8 @@ void rust_helper_rb_link_node(struct rb_node *node, struct rb_node *parent,
 {
 	rb_link_node(node, parent, rb_link);
 }
+
+struct rb_node *rust_helper_rb_first(const struct rb_root *root)
+{
+	return rb_first(root);
+}