block: set rq->resid_len to blk_rq_bytes() on issue

In commit c3a4d78c58, 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 request start 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

Boaz Harrosh spotted bug in resid_len initialization.  Fixed as
suggested.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Borislav Petkov <petkovbb@googlemail.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: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Eric Moore <Eric.Moore@lsi.com>
Cc: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/blk-core.c

@@ -1783,9 +1783,10 @@ void blk_start_request(struct request *req)
 	blk_dequeue_request(req);
 
 	/*
-	 * We are now handing the request to the hardware, add the
-	 * timeout handler.
+	 * We are now handing the request to the hardware, initialize
+	 * resid_len to full count and add the timeout handler.
 	 */
+	req->resid_len = blk_rq_bytes(req);
 	blk_add_timer(req);
 }
 EXPORT_SYMBOL(blk_start_request);

drivers/block/ub.c

@@ -781,8 +781,10 @@ static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
 
 	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) {

drivers/ide/ide-cd.c

@@ -699,6 +699,7 @@ static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
 
 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;
 		}

drivers/ide/ide-tape.c

@@ -380,7 +380,7 @@ static int ide_tape_callback(ide_drive_t *drive, int dsc)
 		}
 
 		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;

drivers/message/fusion/mptsas.c

@@ -1357,7 +1357,8 @@ static int mptsas_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 		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__);

drivers/scsi/libsas/sas_expander.c

@@ -1937,7 +1937,11 @@ int sas_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 	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;

drivers/scsi/libsas/sas_host_smp.c

@@ -176,9 +176,6 @@ int sas_smp_host_handler(struct Scsi_Host *shost, struct request *req,
 	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;

drivers/scsi/mpt2sas/mpt2sas_transport.c

@@ -1170,8 +1170,8 @@ transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 
 		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__));