From: Ming Lei <ming.lei@redhat.com>
To: Yu Kuai <yukuai3@huawei.com>
Cc: josef@toxicpanda.com, axboe@kernel.dk, hch@infradead.org,
linux-block@vger.kernel.org, nbd@other.debian.org,
linux-kernel@vger.kernel.org, yi.zhang@huawei.com
Subject: Re: [PATCH v7 2/6] nbd: make sure request completion won't concurrent
Date: Thu, 16 Sep 2021 15:53:18 +0800 [thread overview]
Message-ID: <YUL37uANjYQbG382@T590> (raw)
In-Reply-To: <20210915092010.2087371-3-yukuai3@huawei.com>
On Wed, Sep 15, 2021 at 05:20:06PM +0800, Yu Kuai wrote:
> commit cddce0116058 ("nbd: Aovid double completion of a request")
> try to fix that nbd_clear_que() and recv_work() can complete a
> request concurrently. However, the problem still exists:
>
> t1 t2 t3
>
> nbd_disconnect_and_put
> flush_workqueue
> recv_work
> blk_mq_complete_request
> blk_mq_complete_request_remote -> this is true
> WRITE_ONCE(rq->state, MQ_RQ_COMPLETE)
> blk_mq_raise_softirq
> blk_done_softirq
> blk_complete_reqs
> nbd_complete_rq
> blk_mq_end_request
> blk_mq_free_request
> WRITE_ONCE(rq->state, MQ_RQ_IDLE)
> nbd_clear_que
> blk_mq_tagset_busy_iter
> nbd_clear_req
> __blk_mq_free_request
> blk_mq_put_tag
> blk_mq_complete_request -> complete again
>
> There are three places where request can be completed in nbd:
> recv_work(), nbd_clear_que() and nbd_xmit_timeout(). Since they
> all hold cmd->lock before completing the request, it's easy to
> avoid the problem by setting and checking a cmd flag.
>
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
Reviewed-by: Ming Lei <ming.lei@redhat.com>
--
Ming
next prev parent reply other threads:[~2021-09-16 7:53 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-15 9:20 [PATCH v7 0/6] handle unexpected message from server Yu Kuai
2021-09-15 9:20 ` [PATCH v7 1/6] nbd: don't handle response without a corresponding request message Yu Kuai
2021-09-15 9:20 ` [PATCH v7 2/6] nbd: make sure request completion won't concurrent Yu Kuai
2021-09-16 7:53 ` Ming Lei [this message]
2021-09-15 9:20 ` [PATCH v7 3/6] nbd: check sock index in nbd_read_stat() Yu Kuai
2021-09-15 9:20 ` [PATCH v7 4/6] nbd: don't start request if nbd_queue_rq() failed Yu Kuai
2021-09-16 7:58 ` Ming Lei
2021-09-15 9:20 ` [PATCH v7 5/6] nbd: partition nbd_read_stat() into nbd_read_reply() and nbd_handle_reply() Yu Kuai
2021-09-16 8:00 ` Ming Lei
2021-09-15 9:20 ` [PATCH v7 6/6] nbd: fix uaf in nbd_handle_reply() Yu Kuai
2021-09-16 8:04 ` Ming Lei
2021-09-16 8:47 ` yukuai (C)
2021-09-16 9:06 ` Ming Lei
2021-09-16 9:14 ` yukuai (C)
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