path: root/block
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authorShaohua Li <shaohua.li@intel.com>2011-12-16 14:04:23 +0100
committerJens Axboe <axboe@kernel.dk>2011-12-16 14:04:23 +0100
commit6ae0516b8a50ece5d766be608a305707e0450060 (patch)
tree90e4768d9d984d94cb45464b49b9c62b93ffba9f /block
parent4eabc941259f9d8c8fb71746d3f30c87e1d9e49b (diff)
block, cfq: fix empty queue crash caused by request merge
All requests of a queue could be merged to other requests of other queue. Such queue will not have request in it, but it's in service tree. This will cause kernel oops. I encounter a BUG_ON() in cfq_dispatch_request() with next patch, but the issue should exist without the patch. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
1 files changed, 12 insertions, 0 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4c12869fcf7..3548705b04e 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1655,6 +1655,8 @@ cfq_merged_requests(struct request_queue *q, struct request *rq,
struct request *next)
struct cfq_queue *cfqq = RQ_CFQQ(rq);
+ struct cfq_data *cfqd = q->elevator->elevator_data;
* reposition in fifo if next is older than rq
@@ -1669,6 +1671,16 @@ cfq_merged_requests(struct request_queue *q, struct request *rq,
rq_data_dir(next), rq_is_sync(next));
+ cfqq = RQ_CFQQ(next);
+ /*
+ * all requests of this queue are merged to other queues, delete it
+ * from the service tree. If it's the active_queue,
+ * cfq_dispatch_requests() will choose to expire it or do idle
+ */
+ if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list) &&
+ cfqq != cfqd->active_queue)
+ cfq_del_cfqq_rr(cfqd, cfqq);
static int cfq_allow_merge(struct request_queue *q, struct request *rq,