[PATCH] CFQ: bad locking in changed_ioprio()

When the ioprio code recently got juggled a bit, a bug was introduced.
changed_ioprio() is no longer called with interrupts disabled, so using
plain spin_lock() on the queue_lock is a bug.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 5c3da894a56c..25c4e7ed0d00 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1215,11 +1215,12 @@ static inline void changed_ioprio(struct cfq_io_context *cic)
 {
         struct cfq_data *cfqd = cic->key;
         struct cfq_queue *cfqq;
+        unsigned long flags;
 
         if (unlikely(!cfqd))
                 return;
 
-        spin_lock(cfqd->queue->queue_lock);
+        spin_lock_irqsave(cfqd->queue->queue_lock, flags);
 
         cfqq = cic->cfqq[ASYNC];
         if (cfqq) {
@@ -1236,7 +1237,7 @@ static inline void changed_ioprio(struct cfq_io_context *cic)
         if (cfqq)
                 cfq_mark_cfqq_prio_changed(cfqq);
 
-        spin_unlock(cfqd->queue->queue_lock);
+        spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
 }
 
 static void cfq_ioc_set_ioprio(struct io_context *ioc)