linux-kernel - Re: [RFC PATCH 3/3] nvme: Introduce nvme_execute_passthru_rq

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Date:   Fri, 25 Oct 2019 13:41:03 -0700
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org
Cc:     Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>,
        Stephen Bates <sbates@...thlin.com>,
        Keith Busch <kbusch@...nel.org>,
        Max Gurtovoy <maxg@...lanox.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [RFC PATCH 3/3] nvme: Introduce nvme_execute_passthru_rq_nowait()

> +#ifdef CONFIG_NVME_TARGET_PASSTHRU
> +static void nvme_execute_passthru_rq_work(struct work_struct *w)
> +{
> +	struct nvme_request *req = container_of(w, struct nvme_request, work);
> +	struct request *rq = blk_mq_rq_from_pdu(req);
> +	rq_end_io_fn *done = rq->end_io;
> +	void *end_io_data = rq->end_io_data;

Why is end_io_data stored to a local variable here? where is it set?

> +
> +	nvme_execute_passthru_rq(rq);
> +
> +	if (done) {
> +		rq->end_io_data = end_io_data;
> +		done(rq, 0);
> +	}
> +}
> +
> +void nvme_execute_passthru_rq_nowait(struct request *rq, rq_end_io_fn *done)
> +{
> +	struct nvme_command *cmd = nvme_req(rq)->cmd;
> +	struct nvme_ctrl *ctrl = nvme_req(rq)->ctrl;
> +	struct nvme_ns *ns = rq->q->queuedata;
> +	struct gendisk *disk = ns ? ns->disk : NULL;
> +	u32 effects;
> +
> +	/*
> +	 * This function may be called in interrupt context, so we cannot sleep
> +	 * but nvme_passthru_[start|end]() may sleep so we need to execute
> +	 * the command in a work queue.
> +	 */
> +	effects = nvme_command_effects(ctrl, ns, cmd->common.opcode);
> +	if (effects) {
> +		rq->end_io = done;
> +		INIT_WORK(&nvme_req(rq)->work, nvme_execute_passthru_rq_work);
> +		queue_work(nvme_wq, &nvme_req(rq)->work);

This work will need to be flushed when in nvme_stop_ctrl. That is
assuming that it will fail-fast and not hang (which it should given
that its a passthru command that is allocated via nvme_alloc_request).