RE: [PATCH 5.10 83/83] scsi: ufs: core: Fix task management completion

["Hunter, Adrian" <adrian.hunter@intel.com>]

Hi

This doesn't work.  Please drop.  Sorry, no idea why I sent it before testing.

Specifically, in v5.10, ufshcd_tmc_handler() can be called under the same spinlock
it is using, which deadlocks.

Regards
Adrian

> -----Original Message-----
> From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Sent: Monday, October 11, 2021 4:47 PM
> To: linux-kernel@vger.kernel.org
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>;
> stable@vger.kernel.org; Bart Van Assche <bvanassche@acm.org>; Hunter,
> Adrian <adrian.hunter@intel.com>; Martin K. Petersen
> <martin.petersen@oracle.com>
> Subject: [PATCH 5.10 83/83] scsi: ufs: core: Fix task management completion
> 
> From: Adrian Hunter <adrian.hunter@intel.com>
> 
> commit f5ef336fd2e4c36dedae4e7ca66cf5349d6fda62 upstream.
> 
> The UFS driver uses blk_mq_tagset_busy_iter() when identifying task
> management requests to complete, however blk_mq_tagset_busy_iter()
> doesn't
> work.
> 
> blk_mq_tagset_busy_iter() only iterates requests dispatched by the block
> layer. That appears as if it might have started since commit 37f4a24c2469
> ("blk-mq: centralise related handling into blk_mq_get_driver_tag") which
> removed 'data->hctx->tags->rqs[rq->tag] = rq' from blk_mq_rq_ctx_init()
> which gets called:
> 
> 	blk_get_request
> 		blk_mq_alloc_request
> 			__blk_mq_alloc_request
> 				blk_mq_rq_ctx_init
> 
> Since UFS task management requests are not dispatched by the block layer,
> hctx->tags->rqs[rq->tag] remains NULL, and since
> blk_mq_tagset_busy_iter()
> relies on finding requests using hctx->tags->rqs[rq->tag], UFS task
> management requests are never found by blk_mq_tagset_busy_iter().
> 
> By using blk_mq_tagset_busy_iter(), the UFS driver was relying on internal
> details of the block layer, which was fragile and subsequently got
> broken. Fix by removing the use of blk_mq_tagset_busy_iter() and having
> the
> driver keep track of task management requests.
> 
> Link: https://lore.kernel.org/r/20210922091059.4040-1-
> adrian.hunter@intel.com
> Fixes: 1235fc569e0b ("scsi: ufs: core: Fix task management request
> completion timeout")
> Fixes: 69a6c269c097 ("scsi: ufs: Use blk_{get,put}_request() to allocate and
> free TMFs")
> Cc: stable@vger.kernel.org
> Tested-by: Bart Van Assche <bvanassche@acm.org>
> Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> ---
>  drivers/scsi/ufs/ufshcd.c |   54 +++++++++++++++++++++----------------------
> ---
>  drivers/scsi/ufs/ufshcd.h |    1
>  2 files changed, 26 insertions(+), 29 deletions(-)
> 
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -6105,27 +6105,6 @@ static irqreturn_t ufshcd_check_errors(s
>  	return retval;
>  }
> 
> -struct ctm_info {
> -	struct ufs_hba	*hba;
> -	unsigned long	pending;
> -	unsigned int	ncpl;
> -};
> -
> -static bool ufshcd_compl_tm(struct request *req, void *priv, bool reserved)
> -{
> -	struct ctm_info *const ci = priv;
> -	struct completion *c;
> -
> -	WARN_ON_ONCE(reserved);
> -	if (test_bit(req->tag, &ci->pending))
> -		return true;
> -	ci->ncpl++;
> -	c = req->end_io_data;
> -	if (c)
> -		complete(c);
> -	return true;
> -}
> -
>  /**
>   * ufshcd_tmc_handler - handle task management function completion
>   * @hba: per adapter instance
> @@ -6136,14 +6115,24 @@ static bool ufshcd_compl_tm(struct reque
>   */
>  static irqreturn_t ufshcd_tmc_handler(struct ufs_hba *hba)
>  {
> -	struct request_queue *q = hba->tmf_queue;
> -	struct ctm_info ci = {
> -		.hba	 = hba,
> -		.pending = ufshcd_readl(hba,
> REG_UTP_TASK_REQ_DOOR_BELL),
> -	};
> +	unsigned long flags, pending, issued;
> +	irqreturn_t ret = IRQ_NONE;
> +	int tag;
> 
> -	blk_mq_tagset_busy_iter(q->tag_set, ufshcd_compl_tm, &ci);
> -	return ci.ncpl ? IRQ_HANDLED : IRQ_NONE;
> +	pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
> +
> +	spin_lock_irqsave(hba->host->host_lock, flags);
> +	issued = hba->outstanding_tasks & ~pending;
> +	for_each_set_bit(tag, &issued, hba->nutmrs) {
> +		struct request *req = hba->tmf_rqs[tag];
> +		struct completion *c = req->end_io_data;
> +
> +		complete(c);
> +		ret = IRQ_HANDLED;
> +	}
> +	spin_unlock_irqrestore(hba->host->host_lock, flags);
> +
> +	return ret;
>  }
> 
>  /**
> @@ -6273,9 +6262,9 @@ static int __ufshcd_issue_tm_cmd(struct
>  	ufshcd_hold(hba, false);
> 
>  	spin_lock_irqsave(host->host_lock, flags);
> -	blk_mq_start_request(req);
> 
>  	task_tag = req->tag;
> +	hba->tmf_rqs[req->tag] = req;
>  	treq->req_header.dword_0 |= cpu_to_be32(task_tag);
> 
>  	memcpy(hba->utmrdl_base_addr + task_tag, treq, sizeof(*treq));
> @@ -6319,6 +6308,7 @@ static int __ufshcd_issue_tm_cmd(struct
>  	}
> 
>  	spin_lock_irqsave(hba->host->host_lock, flags);
> +	hba->tmf_rqs[req->tag] = NULL;
>  	__clear_bit(task_tag, &hba->outstanding_tasks);
>  	spin_unlock_irqrestore(hba->host->host_lock, flags);
> 
> @@ -9246,6 +9236,12 @@ int ufshcd_init(struct ufs_hba *hba, voi
>  		err = PTR_ERR(hba->tmf_queue);
>  		goto free_tmf_tag_set;
>  	}
> +	hba->tmf_rqs = devm_kcalloc(hba->dev, hba->nutmrs,
> +				    sizeof(*hba->tmf_rqs), GFP_KERNEL);
> +	if (!hba->tmf_rqs) {
> +		err = -ENOMEM;
> +		goto free_tmf_queue;
> +	}
> 
>  	/* Reset the attached device */
>  	ufshcd_vops_device_reset(hba);
> --- a/drivers/scsi/ufs/ufshcd.h
> +++ b/drivers/scsi/ufs/ufshcd.h
> @@ -731,6 +731,7 @@ struct ufs_hba {
> 
>  	struct blk_mq_tag_set tmf_tag_set;
>  	struct request_queue *tmf_queue;
> +	struct request **tmf_rqs;
> 
>  	struct uic_command *active_uic_cmd;
>  	struct mutex uic_cmd_mutex;
>