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Subject[PATCH 29/91] cfq-iosched: fix a rcu warning
2.6.27-longterm review patch.  If anyone has any objections, please let us know.

------------------

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>
---
block/cfq-iosched.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)

Index: longterm-2.6.27/block/cfq-iosched.c
===================================================================
--- longterm-2.6.27.orig/block/cfq-iosched.c 2012-02-05 22:34:38.850917663 +0100
+++ longterm-2.6.27/block/cfq-iosched.c 2012-02-05 22:34:38.987917155 +0100
@@ -1286,11 +1286,14 @@
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]);



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