[PATCH AUTOSEL 5.4 16/22] block: only call sched requeue_request() for scheduled requests

Sasha Levin
2020-09-14T14:44:02Z

From: Omar Sandoval <osandov@fb.com>

[ Upstream commit e8a8a185051a460e3eb0617dca33f996f4e31516 ]

Yang Yang reported the following crash caused by requeueing a flush
request in Kyber:

[ 2.517297] Unable to handle kernel paging request at virtual address ffffffd8071c0b00
...
[ 2.517468] pc : clear_bit+0x18/0x2c
[ 2.517502] lr : sbitmap_queue_clear+0x40/0x228
[ 2.517503] sp : ffffff800832bc60 pstate : 00c00145
...
[ 2.517599] Process ksoftirqd/5 (pid: 51, stack limit = 0xffffff8008328000)
[ 2.517602] Call trace:
[ 2.517606] clear_bit+0x18/0x2c
[ 2.517619] kyber_finish_request+0x74/0x80
[ 2.517627] blk_mq_requeue_request+0x3c/0xc0
[ 2.517637] __scsi_queue_insert+0x11c/0x148
[ 2.517640] scsi_softirq_done+0x114/0x130
[ 2.517643] blk_done_softirq+0x7c/0xb0
[ 2.517651] __do_softirq+0x208/0x3bc
[ 2.517657] run_ksoftirqd+0x34/0x60
[ 2.517663] smpboot_thread_fn+0x1c4/0x2c0
[ 2.517667] kthread+0x110/0x120
[ 2.517669] ret_from_fork+0x10/0x18

This happens because Kyber doesn't track flush requests, so
kyber_finish_request() reads a garbage domain token. Only call the
scheduler's requeue_request() hook if RQF_ELVPRIV is set (like we do for
the finish_request() hook in blk_mq_free_request()). Now that we're
handling it in blk-mq, also remove the check from BFQ.

Reported-by: Yang Yang <yang.yang@vivo.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/bfq-iosched.c | 12 ------------
block/blk-mq-sched.h | 2 +-
2 files changed, 1 insertion(+), 13 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 88497bff1135f..ba32adaeefdd0 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5890,18 +5890,6 @@ static void bfq_finish_requeue_request(struct request *rq)
struct bfq_queue *bfqq = RQ_BFQQ(rq);
struct bfq_data *bfqd;

- /*
- * Requeue and finish hooks are invoked in blk-mq without
- * checking whether the involved request is actually still
- * referenced in the scheduler. To handle this fact, the
- * following two checks make this function exit in case of
- * spurious invocations, for which there is nothing to do.
- *
- * First, check whether rq has nothing to do with an elevator.
- */
- if (unlikely(!(rq->rq_flags & RQF_ELVPRIV)))
- return;
-
/*
* rq either is not associated with any icq, or is an already
* requeued request that has not (yet) been re-inserted into
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 126021fc3a11f..e81ca1bf6e10b 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -66,7 +66,7 @@ static inline void blk_mq_sched_requeue_request(struct request *rq)
struct request_queue *q = rq->q;
struct elevator_queue *e = q->elevator;

- if (e && e->type->ops.requeue_request)
+ if ((rq->rq_flags & RQF_ELVPRIV) && e && e->type->ops.requeue_request)
e->type->ops.requeue_request(rq);
}

--
2.25.1