linux-kernel - Re: [PATCH v3 15/16] nvmet-fc: avoid deadlock on delete association path

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Message-ID: <662c46d9-d342-47c3-9048-9d73d8e745a5@suse.de>
Date: Tue, 19 Dec 2023 12:43:46 +0100
From: Hannes Reinecke <hare@...e.de>
To: Daniel Wagner <dwagner@...e.de>, linux-nvme@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
 Sagi Grimberg <sagi@...mberg.me>, Keith Busch <kbusch@...nel.org>,
 James Smart <james.smart@...adcom.com>
Subject: Re: [PATCH v3 15/16] nvmet-fc: avoid deadlock on delete association
 path

On 12/18/23 16:31, Daniel Wagner wrote:
> When deleting an association the shutdown path is deadlocking because we
> try to flush the nvmet_wq nested. Avoid this by deadlock by deferring
> the put work into its own work item.
> 
Maybe deleting the first 'by' ?

> Signed-off-by: Daniel Wagner <dwagner@...e.de>
> ---
>   drivers/nvme/target/fc.c | 14 ++++++++++++--
>   1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
> index 23d8779dc221..30ba4ede333f 100644
> --- a/drivers/nvme/target/fc.c
> +++ b/drivers/nvme/target/fc.c
> @@ -111,6 +111,8 @@ struct nvmet_fc_tgtport {
>   	struct nvmet_fc_port_entry	*pe;
>   	struct kref			ref;
>   	u32				max_sg_cnt;
> +
> +	struct work_struct		put_work;
>   };
>   
>   struct nvmet_fc_port_entry {
> @@ -243,6 +245,13 @@ static LIST_HEAD(nvmet_fc_portentry_list);
>   
>   static void nvmet_fc_handle_ls_rqst_work(struct work_struct *work);
>   static void nvmet_fc_fcp_rqst_op_defer_work(struct work_struct *work);
> +static void nvmet_fc_put_tgtport_work(struct work_struct *work)
> +{
> +	struct nvmet_fc_tgtport *tgtport =
> +		container_of(work, struct nvmet_fc_tgtport, put_work);
> +
> +	nvmet_fc_tgtport_put(tgtport);
> +}
>   static void nvmet_fc_tgt_a_put(struct nvmet_fc_tgt_assoc *assoc);
>   static int nvmet_fc_tgt_a_get(struct nvmet_fc_tgt_assoc *assoc);
>   static void nvmet_fc_tgt_q_put(struct nvmet_fc_tgt_queue *queue);
> @@ -359,7 +368,7 @@ __nvmet_fc_finish_ls_req(struct nvmet_fc_ls_req_op *lsop)
>   
>   	if (!lsop->req_queued) {
>   		spin_unlock_irqrestore(&tgtport->lock, flags);
> -		nvmet_fc_tgtport_put(tgtport);
> +		queue_work(nvmet_wq, &tgtport->put_work);
>   		return;
>   	}
>   
> @@ -373,7 +382,7 @@ __nvmet_fc_finish_ls_req(struct nvmet_fc_ls_req_op *lsop)
>   				  (lsreq->rqstlen + lsreq->rsplen),
>   				  DMA_BIDIRECTIONAL);
>   
> -	nvmet_fc_tgtport_put(tgtport);
> +	queue_work(nvmet_wq, &tgtport->put_work);
>   }
>   
>   static int
> @@ -1402,6 +1411,7 @@ nvmet_fc_register_targetport(struct nvmet_fc_port_info *pinfo,
>   	kref_init(&newrec->ref);
>   	ida_init(&newrec->assoc_cnt);
>   	newrec->max_sg_cnt = template->max_sgl_segments;
> +	INIT_WORK(&newrec->put_work, nvmet_fc_put_tgtport_work);
>   
>   	ret = nvmet_fc_alloc_ls_iodlist(newrec);
>   	if (ret) {
Otherwise:

Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
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