cfq-iosched: Do not access cfqq after freeing it

Fix a crash during boot reported by Jeff Moyer. Fix the issue of accessing
cfqq after freeing it.

Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@carl.(none)>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3815f97..cfb0b2f 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2368,7 +2368,7 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
 static void cfq_put_queue(struct cfq_queue *cfqq)
 {
        struct cfq_data *cfqd = cfqq->cfqd;
-       struct cfq_group *cfqg;
+       struct cfq_group *cfqg, *orig_cfqg;
 
        BUG_ON(atomic_read(&cfqq->ref) <= 0);
 
@@ -2379,6 +2379,7 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
        BUG_ON(rb_first(&cfqq->sort_list));
        BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
        cfqg = cfqq->cfqg;
+       orig_cfqg = cfqq->orig_cfqg;
 
        if (unlikely(cfqd->active_queue == cfqq)) {
                __cfq_slice_expired(cfqd, cfqq, 0);
@@ -2388,8 +2389,8 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
        BUG_ON(cfq_cfqq_on_rr(cfqq));
        kmem_cache_free(cfq_pool, cfqq);
        cfq_put_cfqg(cfqg);
-       if (cfqq->orig_cfqg)
-               cfq_put_cfqg(cfqq->orig_cfqg);
+       if (orig_cfqg)
+               cfq_put_cfqg(orig_cfqg);
 }
 
 /*