Re: [RFC PATCH v2 1/1] scsi: ufs: fix lrbp pointer incorrect initialization issue

[Bart Van Assche <bvanassche@acm.org>]

On 2020-03-08 07:56, Bean Huo wrote:
> The parameter cmd of ufshcd_init_cmd_priv() wasn't given a correct tag
> value while the SCSI layer calls back ufshcd_init_cmd_priv(), this results
> in all pointers of lrbp in UFS driver point to first the lrbp.
> 
> As this is just observed, the patch is for reference so others
> who want to use the latest UFS driver can avoid this issue. Any recommend
> is welcomed.

How about also removing ufshcd_init_cmd_priv(), like in the untested patch
below?

Thanks,

Bart.

Subject: [PATCH] ufs: Fix LRB initialization

There are two issues with the ufshcd_init_lrb() call in
ufshcd_init_cmd_priv():
- cmd->tag is set from inside scsi_mq_prep_fn() and hence is not yet set
  when ufshcd_init_cmd_priv() is set.
- Inside ufshcd_init_cmd_priv() the tag can only be derived from the SCSI
  command pointer if no scheduler has been associated with the UFS block
  device. If no scheduler is associated with a block device, the
  relationship between hctx->tags->static_rqs[] and rq->tag is static.
  If a scheduler has been configured, a single tag can be associated
  with a different struct request if a request is reallocated.

Fixes: 34656dda81ac ("ufs: Let the SCSI core allocate per-command UFS data")
---
 drivers/scsi/ufs/ufshcd.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index e987fa3a77c7..1589ba70672f 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -2473,6 +2473,8 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)

 	WARN_ON_ONCE(!ufshcd_is_scsi(cmd->request));

+	ufshcd_init_lrb(hba, lrbp, tag);
+
 	if (!down_read_trylock(&hba->clk_scaling_lock))
 		return SCSI_MLQUEUE_HOST_BUSY;

@@ -2707,6 +2709,7 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,

 	init_completion(&wait);
 	lrbp = ufshcd_req_to_lrb(req);
+	ufshcd_init_lrb(hba, lrbp, tag);
 	err = ufshcd_compose_dev_cmd(hba, lrbp, cmd_type, tag);
 	if (unlikely(err))
 		goto out_put_tag;
@@ -3504,14 +3507,6 @@ static void ufshcd_host_memory_configure(struct ufs_hba *hba)
 	}
 }

-static int ufshcd_init_cmd_priv(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
-{
-	struct ufs_hba *hba = shost_priv(shost);
-
-	ufshcd_init_lrb(hba, scsi_cmd_priv(cmd), cmd->tag);
-	return 0;
-}
-
 /**
  * ufshcd_dme_link_startup - Notify Unipro to perform link startup
  * @hba: per adapter instance
@@ -5900,6 +5895,7 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba,

 	init_completion(&wait);
 	lrbp = ufshcd_req_to_lrb(req);
+	ufshcd_init_lrb(hba, lrbp, tag);
 	lrbp->sense_bufflen = 0;
 	lrbp->sense_buffer = NULL;
 	lrbp->task_tag = tag;
@@ -7180,7 +7176,6 @@ static struct scsi_host_template ufshcd_driver_template = {
 	.module			= THIS_MODULE,
 	.name			= UFSHCD,
 	.proc_name		= UFSHCD,
-	.init_cmd_priv		= ufshcd_init_cmd_priv,
 	.queuecommand		= ufshcd_queuecommand,
 	.slave_alloc		= ufshcd_slave_alloc,
 	.slave_configure	= ufshcd_slave_configure,