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Commit 6ae0516b8a50ece5d766be608a305707e0450060

Authored by Shaohua Li
Committed by Jens Axboe
1 parent 4eabc94125
Exists in master and in 6 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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>

Showing 1 changed file with 12 additions and 0 deletions Side-by-side Diff

... ... @@ -1655,6 +1655,8 @@
1655 1655 struct request *next)
1656 1656 {
1657 1657 struct cfq_queue *cfqq = RQ_CFQQ(rq);
  1658 + struct cfq_data *cfqd = q->elevator->elevator_data;
  1659 +
1658 1660 /*
1659 1661 * reposition in fifo if next is older than rq
1660 1662 */
... ... @@ -1669,6 +1671,16 @@
1669 1671 cfq_remove_request(next);
1670 1672 cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg,
1671 1673 rq_data_dir(next), rq_is_sync(next));
  1674 +
  1675 + cfqq = RQ_CFQQ(next);
  1676 + /*
  1677 + * all requests of this queue are merged to other queues, delete it
  1678 + * from the service tree. If it's the active_queue,
  1679 + * cfq_dispatch_requests() will choose to expire it or do idle
  1680 + */
  1681 + if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list) &&
  1682 + cfqq != cfqd->active_queue)
  1683 + cfq_del_cfqq_rr(cfqd, cfqq);
1672 1684 }
1673 1685  
1674 1686 static int cfq_allow_merge(struct request_queue *q, struct request *rq,