[PATCH 2/3] tcm/pscsi: Add proper BIDI-COMMAND passthrough to SCSI MidLayer

[Nicholas A. Bellinger]

From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>

This patch updates the TCM/pSCSI plugin to support BIDI-COMMAND passthrough to the
Linux/SCSI MidLayer using struct se_task->task_sg_bidi[] from commit 2f2e67d85860,
and the setup of the extra struct request for the BIDI SCSI READ payload.

This patchturns the original pscsi_map_task_SG() into a wrapper call for the
new __pscsi_map_task_SG() which now accepts struct scatterlist *task_sg and u32 task_sg_num
for struct se_task -> struct bio allocation, map and blk_make_request() calls.

It also updates pscsi_blk_init_request() which now gets called twice for BIDI-COMMAND
case.  This includes the pscsi_blk_init_request() change to perform the assignment of
'req->cmd = &pt->pscsi_cdb[0]' and drop the original CDB memcpy() of pt->pscsi_cdb[]
into struct request->cmd[] -> struct request->__cmd[MAX_BLK_CDB].

Tested with scsi_debug w/ XDWRITE_READ32 and TCM_Loop w/ TCM/pSCSI backstores
using 'sgv4_xdwriteread -e'.

Signed-off-by: Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx>
---
 drivers/target/target_core_pscsi.c |  111 +++++++++++++++++++++++++++--------
 drivers/target/target_core_pscsi.h |    1 +
 2 files changed, 86 insertions(+), 26 deletions(-)

diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index beca807..60f825d 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -727,29 +727,37 @@ static void *pscsi_allocate_request(
 
 static inline void pscsi_blk_init_request(
 	struct se_task *task,
-	struct pscsi_plugin_task *pt)
+	struct pscsi_plugin_task *pt,
+	struct request *req,
+	int bidi_read)
 {
 	/*
 	 * Defined as "scsi command" in include/linux/blkdev.h.
 	 */
-	pt->pscsi_req->cmd_type = REQ_TYPE_BLOCK_PC;
+	req->cmd_type = REQ_TYPE_BLOCK_PC;
+	/*
+	 * For the extra BIDI-COMMAND READ struct request we do not
+	 * need to setup the remaining structure members
+	 */
+	if (bidi_read)
+		return;
 	/*
 	 * Setup the done function pointer for struct request,
 	 * also set the end_io_data pointer.to struct se_task.
 	 */
-	pt->pscsi_req->end_io = pscsi_req_done;
-	pt->pscsi_req->end_io_data = (void *)task;
+	req->end_io = pscsi_req_done;
+	req->end_io_data = (void *)task;
 	/*
 	 * Load the referenced struct se_task's SCSI CDB into
 	 * include/linux/blkdev.h:struct request->cmd
 	 */
-	pt->pscsi_req->cmd_len = scsi_command_size(pt->pscsi_cdb);
-	memcpy(pt->pscsi_req->cmd, pt->pscsi_cdb, pt->pscsi_req->cmd_len);
+	req->cmd_len = scsi_command_size(pt->pscsi_cdb);
+	req->cmd = &pt->pscsi_cdb[0];
 	/*
 	 * Setup pointer for outgoing sense data.
 	 */
-	pt->pscsi_req->sense = (void *)&pt->pscsi_sense[0];
-	pt->pscsi_req->sense_len = 0;
+	req->sense = (void *)&pt->pscsi_sense[0];
+	req->sense_len = 0;
 }
 
 /*
@@ -771,7 +779,7 @@ static int pscsi_blk_get_request(struct se_task *task)
 	 * Setup the newly allocated struct request for REQ_TYPE_BLOCK_PC,
 	 * and setup rq callback, CDB and sense.
 	 */
-	pscsi_blk_init_request(task, pt);
+	pscsi_blk_init_request(task, pt, pt->pscsi_req, 0);
 	return 0;
 }
 
@@ -1051,11 +1059,11 @@ static inline struct bio *pscsi_get_bio(struct pscsi_dev_virt *pdv, int sg_num)
 #define DEBUG_PSCSI(x...)
 #endif
 
-/*      pscsi_map_task_SG():
- *
- *
- */
-static int pscsi_map_task_SG(struct se_task *task)
+static int __pscsi_map_task_SG(
+	struct se_task *task,
+	struct scatterlist *task_sg,
+	u32 task_sg_num,
+	int bidi_read)
 {
 	struct pscsi_plugin_task *pt = (struct pscsi_plugin_task *) task->transport_req;
 	struct pscsi_dev_virt *pdv = (struct pscsi_dev_virt *) task->se_dev->dev_ptr;
@@ -1063,7 +1071,7 @@ static int pscsi_map_task_SG(struct se_task *task)
 	struct page *page;
 	struct scatterlist *sg;
 	u32 data_len = task->task_size, i, len, bytes, off;
-	int nr_pages = (task->task_size + task->task_sg[0].offset +
+	int nr_pages = (task->task_size + task_sg[0].offset +
 			PAGE_SIZE - 1) >> PAGE_SHIFT;
 	int nr_vecs = 0, ret = 0;
 	int rw = (TASK_CMD(task)->data_direction == DMA_TO_DEVICE);
@@ -1083,7 +1091,7 @@ static int pscsi_map_task_SG(struct se_task *task)
 	 */
 	DEBUG_PSCSI("PSCSI: nr_pages: %d\n", nr_pages);
 
-	for_each_sg(task->task_sg, sg, task->task_sg_num, i) {
+	for_each_sg(task_sg, sg, task_sg_num, i) {
 		page = sg_page(sg);
 		off = sg->offset;
 		len = sg->length;
@@ -1155,20 +1163,44 @@ static int pscsi_map_task_SG(struct se_task *task)
 		}
 	}
 	/*
-	 * Starting with v2.6.31, call blk_make_request() passing in *hbio to
-	 * allocate the pSCSI task a struct request.
+	 * Setup the primary pt->pscsi_req used for non BIDI and BIDI-COMMAND
+	 * primary SCSI WRITE poayload mapped for struct se_task->task_sg[]
 	 */
-	pt->pscsi_req = blk_make_request(pdv->pdv_sd->request_queue,
-				hbio, GFP_KERNEL);
-	if (!(pt->pscsi_req)) {
-		printk(KERN_ERR "pSCSI: blk_make_request() failed\n");
-		goto fail;
+	if (!(bidi_read)) {
+		/*
+		 * Starting with v2.6.31, call blk_make_request() passing in *hbio to
+		 * allocate the pSCSI task a struct request.
+		 */
+		pt->pscsi_req = blk_make_request(pdv->pdv_sd->request_queue,
+					hbio, GFP_KERNEL);
+		if (!(pt->pscsi_req)) {
+			printk(KERN_ERR "pSCSI: blk_make_request() failed\n");
+			goto fail;
+		}
+		/*
+		 * Setup the newly allocated struct request for REQ_TYPE_BLOCK_PC,
+		 * and setup rq callback, CDB and sense.
+		 */
+		pscsi_blk_init_request(task, pt, pt->pscsi_req, 0);
+
+		return task->task_sg_num;
 	}
 	/*
-	 * Setup the newly allocated struct request for REQ_TYPE_BLOCK_PC,
-	 * and setup rq callback, CDB and sense.
+	 * Setup the secondary pt->pscsi_req_bidi used for the extra BIDI-COMMAND
+	 * SCSI READ paylaod mapped for struct se_task->task_sg_bidi[]
 	 */
-	pscsi_blk_init_request(task, pt);
+	pt->pscsi_req_bidi = blk_make_request(pdv->pdv_sd->request_queue,
+					hbio, GFP_KERNEL);
+	if (!(pt->pscsi_req_bidi)) {
+		printk(KERN_ERR "pSCSI: blk_make_request() failed for BIDI\n");
+		goto fail;
+	}
+	pscsi_blk_init_request(task, pt, pt->pscsi_req_bidi, 1);
+	/*
+	 * Setup the magic BIDI-COMMAND ->next_req pointer to the original
+	 * pt->pscsi_req.
+	 */	
+	pt->pscsi_req->next_rq = pt->pscsi_req_bidi;
 
 	return task->task_sg_num;
 fail:
@@ -1181,6 +1213,27 @@ fail:
 	return ret;
 }
 
+static int pscsi_map_task_SG(struct se_task *task)
+{
+	int ret;
+	/*
+	 * Setup the main struct request for the task->task_sg[] payload
+	 */
+
+	ret = __pscsi_map_task_SG(task, task->task_sg, task->task_sg_num, 0);
+	if (ret < 0)
+		return ret;
+
+	if (!(task->task_sg_bidi))
+		return ret;
+	/*
+	 * If present, set up the extra BIDI-COMMAND SCSI READ
+	 * struct request and payload.
+	 */
+	return __pscsi_map_task_SG(task, task->task_sg_bidi,
+				task->task_sg_num, 1);
+}
+
 /*	pscsi_map_task_non_SG():
  *
  *
@@ -1438,6 +1491,12 @@ static void pscsi_req_done(struct request *req, int uptodate)
 	pt->pscsi_resid = req->resid_len;
 
 	pscsi_process_SAM_status(task, pt);
+
+	if (req->next_rq != NULL) {
+		__blk_put_request(req->q, req->next_rq);
+		pt->pscsi_req_bidi = NULL;
+	}
+
 	__blk_put_request(req->q, req);
 	pt->pscsi_req = NULL;
 }
diff --git a/drivers/target/target_core_pscsi.h b/drivers/target/target_core_pscsi.h
index 086e6f1..d3c8972 100644
--- a/drivers/target/target_core_pscsi.h
+++ b/drivers/target/target_core_pscsi.h
@@ -34,6 +34,7 @@ struct pscsi_plugin_task {
 	int	pscsi_result;
 	u32	pscsi_resid;
 	struct request *pscsi_req;
+	struct request *pscsi_req_bidi;
 } ____cacheline_aligned;
 
 #define PDF_HAS_CHANNEL_ID	0x01
-- 
1.5.6.5

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