Re: [PATCH 2/2] [SCSI] ufs: add SCSI host lock push-down for ufs.

[Namjae Jeon <linkinjeon@xxxxxxxxx>]

2012/5/2, James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>:
> On Tue, 2012-05-01 at 10:31 -0400, Namjae Jeon wrote:
>> SCSI host lock push-down patch is not applied in ufs host driver yet.
>> After adding it, I tried to remove unneeded spin lock in queuecommand
>> also.
>
> This really isn't the correct thing: you're increasing the lock coverage
> not decreasing it.
>
> In the old way, ->queuecommand() was called locked.  DEF_SCSI_QCMD() was
> a macro we use to avoid converting all the previous methods from locked
> to unlocked (it simply acts as a bridge between the new way and the old
> way).
>
> In the new way we call ->queuecommand() unlocked and try only to take
> the lock when it's needed, if at all.  The current ufshcd_queuecommand()
> is correct because it only takes the lock when it needs it in
> ufshcd_send_command().  A lock push down into that routine might be
> possible, but since it's only a couple of bytes, probably not worth it.
>
> James
Hi James.
I agree your comment.
Thanks for your explanation.
>
>
>> Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxx>
>> ---
>>  drivers/scsi/ufs/ufshcd.c |   20 ++++++++++----------
>>  1 files changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 3cb7a08..a134738 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -658,23 +658,23 @@ static void ufshcd_compose_upiu(struct ufshcd_lrb
>> *lrbp)
>>  }
>>
>>  /**
>> - * ufshcd_queuecommand - main entry point for SCSI requests
>> + * ufshcd_queuecommand_lck - main entry point for SCSI requests
>>   * @cmd: command from SCSI Midlayer
>>   * @done: call back function
>>   *
>>   * Returns 0 for success, non-zero in case of failure
>>   */
>> -static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd
>> *cmd)
>> +static int
>> +ufshcd_queuecommand_lck(struct scsi_cmnd *scp, void (*done)(struct
>> scsi_cmnd *))
>>  {
>>  	struct ufshcd_lrb *lrbp;
>>  	struct ufs_hba *hba;
>> -	unsigned long flags;
>>  	int tag;
>>  	int err = 0;
>>
>> -	hba = shost_priv(host);
>> +	hba = shost_priv(scp->device->host);
>>
>> -	tag = cmd->request->tag;
>> +	tag = scp->request->tag;
>>
>>  	if (hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL) {
>>  		err = SCSI_MLQUEUE_HOST_BUSY;
>> @@ -683,11 +683,11 @@ static int ufshcd_queuecommand(struct Scsi_Host
>> *host, struct scsi_cmnd *cmd)
>>
>>  	lrbp = &hba->lrb[tag];
>>
>> -	lrbp->cmd = cmd;
>> +	lrbp->cmd = scp;
>>  	lrbp->sense_bufflen = SCSI_SENSE_BUFFERSIZE;
>> -	lrbp->sense_buffer = cmd->sense_buffer;
>> +	lrbp->sense_buffer = scp->sense_buffer;
>>  	lrbp->task_tag = tag;
>> -	lrbp->lun = cmd->device->lun;
>> +	lrbp->lun = scp->device->lun;
>>
>>  	lrbp->command_type = UTP_CMD_TYPE_SCSI;
>>
>> @@ -698,13 +698,13 @@ static int ufshcd_queuecommand(struct Scsi_Host
>> *host, struct scsi_cmnd *cmd)
>>  		goto out;
>>
>>  	/* issue command to the controller */
>> -	spin_lock_irqsave(hba->host->host_lock, flags);
>>  	ufshcd_send_command(hba, tag);
>> -	spin_unlock_irqrestore(hba->host->host_lock, flags);
>>  out:
>>  	return err;
>>  }
>>
>> +static DEF_SCSI_QCMD(ufshcd_queuecommand);
>> +
>>  /**
>>   * ufshcd_memory_alloc - allocate memory for host memory space data
>> structures
>>   * @hba: per adapter instance
>
>
>
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