linux-kernel - Re: [PATCH block#for-2.6.31 2/3] block: set rq->resid_len to blk_rq

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Date:	Sat, 16 May 2009 07:18:27 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Sergei Shtylyov <sshtylyov@...mvista.com>
CC:	Jens Axboe <jens.axboe@...cle.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Boaz Harrosh <bharrosh@...asas.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	IDE/ATA development list <linux-ide@...r.kernel.org>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Borislav Petkov <petkovbb@...glemail.com>,
	Pete Zaitcev <zaitcev@...hat.com>,
	Eric Moore <Eric.Moore@....com>,
	"Darrick J. Wong" <djwong@...ibm.com>
Subject: Re: [PATCH block#for-2.6.31 2/3] block: set rq->resid_len to blk_rq_bytes()
 on issue

Hello,

Sergei Shtylyov wrote:
>> Index: block/drivers/message/fusion/mptsas.c
>> ===================================================================
>> --- block.orig/drivers/message/fusion/mptsas.c
>> +++ block/drivers/message/fusion/mptsas.c
>> @@ -1357,7 +1357,8 @@ static int mptsas_smp_handler(struct Scs
>>          smprep = (SmpPassthroughReply_t *)ioc->sas_mgmt.reply;
>>          memcpy(req->sense, smprep, sizeof(*smprep));
>>          req->sense_len = sizeof(*smprep);
>> -        rsp->resid_len = blk_rq_bytes(rsp) - smprep->ResponseDataLength;
>> +        req->resid_len = 0;
>> +        rsp->resid_len -= smprep->ResponseDataLength;
> 
>    Is negative resid_len intended here? If so, shouldn't it be simply:
> 
>         rsp->resid_len = -smprep->ResponseDataLength;

>From patch description.

 This patchset restores the original behavior by setting rq->resid_len
 to blk_rq_bytes(rq) on issue and restoring explicit clearing in
 affected drivers.

So, rsp->resid_len equals the initial request length before the
subtraction and after subtraction it becomes the residue count.  The
original code was

	req->data_len = 0;
	rsp->data_len -= smprep->ResponseDataLength;

>> Index: block/drivers/scsi/libsas/sas_expander.c
>> ===================================================================
>> --- block.orig/drivers/scsi/libsas/sas_expander.c
>> +++ block/drivers/scsi/libsas/sas_expander.c
>> @@ -1937,7 +1937,11 @@ int sas_smp_handler(struct Scsi_Host *sh
>>      if (ret > 0) {
>>          /* positive number is the untransferred residual */
>>          rsp->resid_len = ret;
>> +        req->resid_len = 0;
>>          ret = 0;
>> +    } else if (ret == 0) {
>> +        rsp->resid_len = 0;
>> +        req->resid_len = 0;

Heh... there's a reason I mentioned the original commit.  The original
code was

	if (ret > 0) {
		/* positive number is the untransferred residual */
		rsp->data_len = ret;
		req->data_len = 0;
		ret = 0;
	} else if (ret == 0) {
		rsp->data_len = 0;
		req->data_len = 0;
	}

>> Index: block/drivers/scsi/libsas/sas_host_smp.c
>> ===================================================================
>> --- block.orig/drivers/scsi/libsas/sas_host_smp.c
>> +++ block/drivers/scsi/libsas/sas_host_smp.c
>> @@ -176,9 +176,6 @@ int sas_smp_host_handler(struct Scsi_Hos
>>      resp_data[1] = req_data[1];
>>      resp_data[2] = SMP_RESP_FUNC_UNK;
>>  
>> -    req->resid_len = blk_rq_bytes(req);
>> -    rsp->resid_len = blk_rq_bytes(rsp);
>> -

Cuz it's already set to blk_rq_bytes().

>>      switch (req_data[1]) {
>>      case SMP_REPORT_GENERAL:
>>          req->resid_len -= 8;
>> Index: block/drivers/scsi/mpt2sas/mpt2sas_transport.c
>> ===================================================================
>> --- block.orig/drivers/scsi/mpt2sas/mpt2sas_transport.c
>> +++ block/drivers/scsi/mpt2sas/mpt2sas_transport.c
>> @@ -1170,8 +1170,8 @@ transport_smp_handler(struct Scsi_Host *
>>  
>>          memcpy(req->sense, mpi_reply, sizeof(*mpi_reply));
>>          req->sense_len = sizeof(*mpi_reply);
>> -        rsp->resid_len = blk_rq_bytes(rsp) -
>> -                 mpi_reply->ResponseDataLength;
>> +        req->resid_len = 0;
>> +        rsp->resid_len -= mpi_reply->ResponseDataLength;
> 
>    Again, is negative resid_len intended?

Ditto.

Thanks.

-- 
tejun
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