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)>

1 files changed, 4 insertions, 3 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3815f9789b6a..cfb0b2f5f63d 100644
--- 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);
 }
 
 /*