Commit 2645672f authored by Jens Axboe's avatar Jens Axboe

block: pop cached rq before potentially blocking rq_qos_throttle()

If rq_qos_throttle() ends up blocking, then we will have invalidated and
flushed our current plug. Since blk_mq_get_cached_request() hasn't
popped the cached request off the plug list just yet, we end holding a
pointer to a request that is no longer valid. This insta-crashes with
rq->mq_hctx being NULL in the validity checks just after.

Pop the request off the cached list before doing rq_qos_throttle() to
avoid using a potentially stale request.

Fixes: 0a5aa8d1 ("block: fix blk_mq_attempt_bio_merge and rq_qos_throttle protection")
Reported-by: default avatarDylan Yudaken <dylany@fb.com>
Tested-by: default avatarDylan Yudaken <dylany@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 9243fc4c
......@@ -2765,15 +2765,20 @@ static inline struct request *blk_mq_get_cached_request(struct request_queue *q,
return NULL;
}
rq_qos_throttle(q, *bio);
if (blk_mq_get_hctx_type((*bio)->bi_opf) != rq->mq_hctx->type)
return NULL;
if (op_is_flush(rq->cmd_flags) != op_is_flush((*bio)->bi_opf))
return NULL;
rq->cmd_flags = (*bio)->bi_opf;
/*
* If any qos ->throttle() end up blocking, we will have flushed the
* plug and hence killed the cached_rq list as well. Pop this entry
* before we throttle.
*/
plug->cached_rq = rq_list_next(rq);
rq_qos_throttle(q, *bio);
rq->cmd_flags = (*bio)->bi_opf;
INIT_LIST_HEAD(&rq->queuelist);
return rq;
}
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment