From: Shaohua Li Date: Fri, 16 Dec 2011 13:00:22 +0000 (+0100) Subject: block, cfq: fix empty queue crash caused by request merge X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=4a0b75c7d02c2bd46ed227d4ba5941ba8a0aba5d;p=openwrt%2Fstaging%2Fblogic.git 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 Signed-off-by: Jens Axboe --- diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index f3b44c394e6d..163263ddd381 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1656,6 +1656,8 @@ 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 */ @@ -1670,6 +1672,16 @@ cfq_merged_requests(struct request_queue *q, struct request *rq, cfq_remove_request(next); cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg, 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,