Re: [PATCH UPDATED block#for-2.6.31 2/3] block: set rq->resid_len to blk_rq_bytes() on issue

[Boaz Harrosh <bharrosh@panasas.com>]

On 05/16/2009 03:18 AM, Tejun Heo wrote:
> In commit c3a4d78c580de4edc9ef0f7c59812fb02ceb037f, while introducing
> rq->resid_len, the default value of residue count was changed from
> full count to zero.  The conversion was done under the assumption that
> when a request fails residue count wasn't defined.  However, Boaz and
> James pointed out that this wasn't true and the residue count should
> be preserved for failed requests too.
> 
> 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.  While at it, take advantage of the fact that
> rq->resid_len is set to full count where applicable.
> 
> * ide-cd: rq->resid_len cleared on pc success
> 
> * mptsas: req->resid_len cleared on success
> 
> * sas_expander: rsp/req->resid_len cleared on success
> 
> * mpt2sas_transport: req->resid_len cleared on success
> 
> * ide-cd, ide-tape, mptsas, sas_host_smp, mpt2sas_transport, ub: take
>   advantage of initial full count to simplify code
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Jens Axboe <jens.axboe@oracle.com>
> Cc: Boaz Harrosh <bharrosh@panasas.com>
> Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
> Cc: Pete Zaitcev <zaitcev@redhat.com>
> Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
> Cc: Borislav Petkov <petkovbb@googlemail.com>
> Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
> Cc: Eric Moore <Eric.Moore@lsi.com>
> Cc: Darrick J. Wong <djwong@us.ibm.com>
> ---
> ub updated per Pete's comment.
> 
> Thanks.
> 
>  block/blk-core.c                         |    1 +
>  drivers/block/ub.c                       |    6 ++++--
>  drivers/ide/ide-cd.c                     |    4 ++--
>  drivers/ide/ide-tape.c                   |    2 +-
>  drivers/message/fusion/mptsas.c          |    3 ++-
>  drivers/scsi/libsas/sas_expander.c       |    4 ++++
>  drivers/scsi/libsas/sas_host_smp.c       |    3 ---
>  drivers/scsi/mpt2sas/mpt2sas_transport.c |    4 ++--
>  8 files changed, 16 insertions(+), 11 deletions(-)
> 
> Index: block/block/blk-core.c
> ===================================================================
> --- block.orig/block/blk-core.c
> +++ block/block/blk-core.c
> @@ -2198,6 +2198,7 @@ void blk_rq_bio_prep(struct request_queu
>  		rq->buffer = bio_data(bio);
>  	}
>  	rq->__data_len = bio->bi_size;
> +	rq->resid_len = bio->bi_size;
>  	rq->bio = rq->biotail = bio;
>  

Hi Tejun.
Surly this is not enough. This is not the only place rq->__data_len gets a value.
Specifically it can be added to in blk_rq_append_bio. You must then update
all places that set rq->__data_len to also set rq->resid_len.

Alternatively you could do a single:
+	rq->resid_len = blk_rq_bytes(rq);

inside  blk_fetch_request(q) or before the call to prep_fn, or even at
__elv_add_request().

Currently this is a bug with chained bios

Thanks
Boaz

>  	if (bio->bi_bdev)
> Index: block/drivers/ide/ide-cd.c
> ===================================================================
> --- block.orig/drivers/ide/ide-cd.c
> +++ block/drivers/ide/ide-cd.c
> @@ -699,6 +699,7 @@ static ide_startstop_t cdrom_newpc_intr(
>  
>  out_end:
>  	if (blk_pc_request(rq) && rc == 0) {
> +		rq->resid_len = 0;
>  		blk_end_request_all(rq, 0);
>  		hwif->rq = NULL;
>  	} else {
> @@ -718,8 +719,7 @@ out_end:
>  
>  		/* make sure it's fully ended */
>  		if (blk_fs_request(rq) == 0) {
> -			rq->resid_len = blk_rq_bytes(rq) -
> -				(cmd->nbytes - cmd->nleft);
> +			rq->resid_len -= cmd->nbytes - cmd->nleft;
>  			if (uptodate == 0 && (cmd->tf_flags & IDE_TFLAG_WRITE))
>  				rq->resid_len += cmd->last_xfer_len;
>  		}
> Index: block/drivers/ide/ide-tape.c
> ===================================================================
> --- block.orig/drivers/ide/ide-tape.c
> +++ block/drivers/ide/ide-tape.c
> @@ -380,7 +380,7 @@ static int ide_tape_callback(ide_drive_t
>  		}
>  
>  		tape->first_frame += blocks;
> -		rq->resid_len = blk_rq_bytes(rq) - blocks * tape->blk_size;
> +		rq->resid_len -= blocks * tape->blk_size;
>  
>  		if (pc->error) {
>  			uptodate = 0;
> 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;
>  	} else {
>  		printk(MYIOC_s_ERR_FMT "%s: smp passthru reply failed to be returned\n",
>  		    ioc->name, __func__);
> 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;
>  	}
>  
>  	return ret;
> 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);
> -
>  	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;
>  	} else {
>  		dtransportprintk(ioc, printk(MPT2SAS_DEBUG_FMT
>  		    "%s - no reply\n", ioc->name, __func__));
> Index: block/drivers/block/ub.c
> ===================================================================
> --- block.orig/drivers/block/ub.c
> +++ block/drivers/block/ub.c
> @@ -781,8 +781,10 @@ static void ub_rw_cmd_done(struct ub_dev
>  
>  	if (cmd->error == 0) {
>  		if (blk_pc_request(rq)) {
> -			if (cmd->act_len < blk_rq_bytes(rq))
> -				rq->resid_len = blk_rq_bytes(rq) - cmd->act_len;
> +			if (cmd->act_len >= rq->resid_len)
> +				rq->resid_len = 0;
> +			else
> +				rq->resid_len -= cmd->act_len;
>  			scsi_status = 0;
>  		} else {
>  			if (cmd->act_len != cmd->len) {