[PATCH v3 0/1] scsi: ufs: fix LRB pointer incorrect initialization issue

[PATCH v3 0/1] scsi: ufs: fix LRB pointer incorrect initialization issue

[huobean]

From: Bean Huo <beanhuo@micron.com>

Hi, Martin and Bart

Based on the Bart's suggestion, delete ufshcd_init_lrb(), and update the patch
to v3. This version patch passed stress test.
Thanks,

//Bean

Bean Huo (1):
  scsi: ufs: fix LRB pointer incorrect initialization issue

 drivers/scsi/ufs/ufshcd.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

-- 
2.17.1

[PATCH v3 1/1] scsi: ufs: fix LRB pointer incorrect initialization issue

[huobean]

From: Bean Huo <beanhuo@micron.com>

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")

v2-v3:
    - delete ufshcd_init_cmd_priv()
    - change commit message

Signed-off-by: Bean Huo <beanhuo@micron.com>
---
 drivers/scsi/ufs/ufshcd.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index e987fa3a77c7..dfb44e8cc9dd 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -2471,6 +2471,8 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
 		BUG();
 	}
 
+	ufshcd_init_lrb(hba, lrbp, tag);
+
 	WARN_ON_ONCE(!ufshcd_is_scsi(cmd->request));
 
 	if (!down_read_trylock(&hba->clk_scaling_lock))
@@ -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
@@ -4834,6 +4829,7 @@ static void __ufshcd_transfer_req_compl(struct ufs_hba *hba,
 			continue;
 		cmd = blk_mq_rq_to_pdu(req);
 		lrbp = scsi_cmd_priv(cmd);
+		ufshcd_init_lrb(hba, lrbp, index);
 		if (ufshcd_is_scsi(req)) {
 			ufshcd_add_command_trace(hba, req, "complete");
 			result = ufshcd_transfer_rsp_status(hba, lrbp);
@@ -5900,6 +5896,7 @@ 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 +7177,6 @@ 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,
-- 
2.17.1

Re: [PATCH v3 1/1] scsi: ufs: fix LRB pointer incorrect initialization issue

[Bart Van Assche]

On 2020-03-09 09:10, huobean@gmail.com wrote:
> @@ -4834,6 +4829,7 @@ static void __ufshcd_transfer_req_compl(struct ufs_hba *hba,
>  			continue;
>  		cmd = blk_mq_rq_to_pdu(req);
>  		lrbp = scsi_cmd_priv(cmd);
> +		ufshcd_init_lrb(hba, lrbp, index);
>  		if (ufshcd_is_scsi(req)) {
>  			ufshcd_add_command_trace(hba, req, "complete");
>  			result = ufshcd_transfer_rsp_status(hba, lrbp);

This ufshcd_init_lrb() call looks incorrect to me. I think that
ufshcd_init_lrb() should only be called before a request is submitted to
the UFS controller and also that ufshcd_init_lrb() should not be called
from the completion path.

Thanks,

Bart.

RE: [EXT] Re: [PATCH v3 1/1] scsi: ufs: fix LRB pointer incorrect initialization issue

[Bean Huo (beanhuo)]

Hi, Bart 

> Subject: [EXT] Re: [PATCH v3 1/1] scsi: ufs: fix LRB pointer incorrect initialization
> issue
> 
> On 2020-03-09 09:10, huobean@gmail.com wrote:
> > @@ -4834,6 +4829,7 @@ static void __ufshcd_transfer_req_compl(struct
> ufs_hba *hba,
> >  			continue;
> >  		cmd = blk_mq_rq_to_pdu(req);
> >  		lrbp = scsi_cmd_priv(cmd);
> > +		ufshcd_init_lrb(hba, lrbp, index);
> >  		if (ufshcd_is_scsi(req)) {
> >  			ufshcd_add_command_trace(hba, req, "complete");
> >  			result = ufshcd_transfer_rsp_status(hba, lrbp);
> 
> This ufshcd_init_lrb() call looks incorrect to me. I think that
> ufshcd_init_lrb() should only be called before a request is submitted to the UFS
> controller and also that ufshcd_init_lrb() should not be called from the
> completion path.
> 

__ufshcd_transfer_req_compl()
	ufshcd_transfer_rsp_status()  will access lrbp->ucd_rsp_ptr.
Without calling ufshcd_init_lrb() here, there will be an error.

//Bean

 
> Thanks,
> 
> Bart.

Re: [EXT] Re: [PATCH v3 1/1] scsi: ufs: fix LRB pointer incorrect initialization issue

[Bart Van Assche]

On 2020-03-10 00:53, Bean Huo (beanhuo) wrote:
> Hi, Bart 
> 
>> Subject: [EXT] Re: [PATCH v3 1/1] scsi: ufs: fix LRB pointer incorrect initialization
>> issue
>>
>> On 2020-03-09 09:10, huobean@gmail.com wrote:
>>> @@ -4834,6 +4829,7 @@ static void __ufshcd_transfer_req_compl(struct
>> ufs_hba *hba,
>>>  			continue;
>>>  		cmd = blk_mq_rq_to_pdu(req);
>>>  		lrbp = scsi_cmd_priv(cmd);
>>> +		ufshcd_init_lrb(hba, lrbp, index);
>>>  		if (ufshcd_is_scsi(req)) {
>>>  			ufshcd_add_command_trace(hba, req, "complete");
>>>  			result = ufshcd_transfer_rsp_status(hba, lrbp);
>>
>> This ufshcd_init_lrb() call looks incorrect to me. I think that
>> ufshcd_init_lrb() should only be called before a request is submitted to the UFS
>> controller and also that ufshcd_init_lrb() should not be called from the
>> completion path.
> 
> __ufshcd_transfer_req_compl()
> 	ufshcd_transfer_rsp_status()  will access lrbp->ucd_rsp_ptr.
> Without calling ufshcd_init_lrb() here, there will be an error.

Hi Bean,

I think that ufshcd_init_lrb() should only be called from the code that
prepares a command before it is submitted and not from the command
completion path. Because v5.6-rc5 has already been released, there is
not that much time left until the merge window opens. I think it is less
risky to revert commit 34656dda81ac ("scsi: ufs: Let the SCSI core
allocate per-command UFS data") than to proceed with the above patch. Do
you want to submit a revert or do you perhaps want me to do that?

Thanks,

Bart.