linux-kernel - [PATCH 03/13] rbtree: fix incorrect rbtree node insertion in fs/proc/proc

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Date:	Mon,  9 Jul 2012 16:35:13 -0700
From:	Michel Lespinasse <walken@...gle.com>
To:	aarcange@...hat.com, dwmw2@...radead.org, riel@...hat.com,
	peterz@...radead.org, daniel.santos@...ox.com, axboe@...nel.dk,
	ebiederm@...ssion.com
Cc:	linux-mm@...ck.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org
Subject: [PATCH 03/13] rbtree: fix incorrect rbtree node insertion in fs/proc/proc_sysctl.c

The recently added code to use rbtrees in sysctl did not follow the proper
rbtree interface on insertion - it was calling rb_link_node() which
inserts a new node into the binary tree, but missed the call to
rb_insert_color() which properly balances the rbtree and establishes all
expected rbtree invariants.

I found out about this only because faulty commit also used rb_init_node(),
which I am removing within this patchset. But I think it's an easy mistake
to make, and it makes me wonder if we should change the rbtree API so that
insertions would be done with a single rb_insert() call (even if its
implementation could still inline the rb_link_node() part and call
a private __rb_insert_color function to do the rebalancing).

Signed-off-by: Michel Lespinasse <walken@...gle.com>
---
 fs/proc/proc_sysctl.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 33aea86..77602c1a 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -142,6 +142,7 @@ static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
 	}

 	rb_link_node(node, parent, p);
+	rb_insert_color(node, &head->parent->root);
 	return 0;
 }

-- 
1.7.7.3

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