From: Shaohua Li <shaohua.li@intel.com>
Date: Mon, 27 Jun 2011 07:03:47 +0000 (+0200)
Subject: cfq-iosched: fix a rcu warning
X-Git-Tag: v2.6.27.60~64
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=95f89dc7063f6efd2c5ce21ee165fd3df1f010e0;p=thirdparty%2Fkernel%2Fstable.git

cfq-iosched: fix a rcu warning

commit 3181faa85bda3dc3f5e630a1846526c9caaa38e3 upstream.

I got a rcu warnning at boot. the ioc->ioc_data is rcu_deferenced, but
doesn't hold rcu_read_lock.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ee3c6068ceb7f..524608ca92b9a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1286,11 +1286,14 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
 	cic->dead_key = (unsigned long) cic->key;
 	cic->key = NULL;
 
+	rcu_read_lock();
 	if (rcu_dereference(ioc->ioc_data) == cic) {
+		rcu_read_unlock();
 		spin_lock(&ioc->lock);
 		rcu_assign_pointer(ioc->ioc_data, NULL);
 		spin_unlock(&ioc->lock);
-	}
+	} else
+		rcu_read_unlock();
 
 	if (cic->cfqq[ASYNC]) {
 		cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);