[PATCH 1/3] scsi: st: instrument the pos_unknown code

[John Meneghini <jmeneghi@xxxxxxxxxx>]

Add debugging printfs to the various code paths that use pos_unknown.
This code is a little chatty but nothing has been added to the datapath.
It has been used to help debug a number of customer reported problems
from the field since the change for commit 9604eea5bd3a ("scsi: st: Add
third party poweron reset handling") was added.

To enable:

  echo 1 > /sys/module/st/drivers/scsi:st/debug_flag

Signed-off-by: John Meneghini <jmeneghi@xxxxxxxxxx>
Reviewed-by: Laurence Oberman <loberman@xxxxxxxxxx>
Tested-by: Laurence Oberman <loberman@xxxxxxxxxx>
---
 drivers/scsi/st.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index d50bad3a2ce9..9c0f9779768e 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -418,6 +418,10 @@ static int st_chk_result(struct scsi_tape *STp, struct st_request * SRpnt)
 
 	STp->pos_unknown |= STp->device->was_reset;
 
+	DEBC_printk(STp, "%s: %d: pos_unknown %x was_reset %x ready %x, result %d\n",
+			__func__, __LINE__, STp->pos_unknown, STp->device->was_reset,
+			STp->ready, result);
+
 	if (cmdstatp->have_sense &&
 	    scode == RECOVERED_ERROR
 #if ST_RECOVERED_WRITE_FATAL
@@ -834,6 +838,10 @@ static int flush_buffer(struct scsi_tape *STp, int seek_next)
 	int backspace, result;
 	struct st_partstat *STps;
 
+	DEBC_printk(STp, "%s: %d: pos_unknown %x was_reset %x ready %x\n",
+		__func__, __LINE__, STp->pos_unknown, STp->device->was_reset,
+		STp->ready);
+
 	if (STp->ready != ST_READY)
 		return 0;
 
@@ -1050,6 +1058,10 @@ static int check_tape(struct scsi_tape *STp, struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int mode = TAPE_MODE(inode);
 
+	DEBC_printk(STp, "%s: %d: pos_unknown %x was_reset %x ready %x\n",
+			__func__, __LINE__, STp->pos_unknown,
+			STp->device->was_reset, STp->ready);
+
 	STp->ready = ST_READY;
 
 	if (mode != STp->current_mode) {
@@ -1085,6 +1097,9 @@ static int check_tape(struct scsi_tape *STp, struct file *filp)
 			STps->drv_file = 0;
 		}
 		new_session = 1;
+		DEBC_printk(STp, "%s: %d: CHKRES_NEW_SESS pos_unknown %x was_reset %x ready %x\n",
+				__func__, __LINE__, STp->pos_unknown, STp->device->was_reset,
+				STp->ready);
 	}
 	else {
 		STp->cleaning_req |= saved_cleaning;
@@ -1101,6 +1116,12 @@ static int check_tape(struct scsi_tape *STp, struct file *filp)
 			STp->ps[0].drv_file = STp->ps[0].drv_block = (-1);
 			STp->partition = STp->new_partition = 0;
 			STp->door_locked = ST_UNLOCKED;
+
+			DEBC_printk(STp,
+				"%s: %d: CHKRES_NOT_READY pos_unknown %x was_reset %x ready %x\n",
+				__func__, __LINE__, STp->pos_unknown, STp->device->was_reset,
+				STp->ready);
+
 			return CHKRES_NOT_READY;
 		}
 	}
@@ -1237,9 +1258,16 @@ static int check_tape(struct scsi_tape *STp, struct file *filp)
 		}
 	}
 
+	DEBC_printk(STp, "%s: %d: CHKRES_READY pos_unknown %x was_reset %x ready %x\n",
+			__func__, __LINE__, STp->pos_unknown, STp->device->was_reset,
+			STp->ready);
+
 	return CHKRES_READY;
 
  err_out:
+	DEBC_printk(STp, "%s: %d: pos_unknown %x was_reset %x ready %x retval %d\n",
+			__func__, __LINE__, STp->pos_unknown, STp->device->was_reset,
+			STp->ready, retval);
 	return retval;
 }
 
@@ -1352,6 +1380,9 @@ static int st_flush(struct file *filp, fl_owner_t id)
 	if (file_count(filp) > 1)
 		return 0;
 
+	DEBC_printk(STp, "%s: %d: pos_unknown %x was_reset %x ready %x\n",
+			__func__, __LINE__, STp->pos_unknown, STp->device->was_reset, STp->ready);
+
 	if (STps->rw == ST_WRITING && !STp->pos_unknown) {
 		result = st_flush_write_buffer(STp);
 		if (result != 0 && result != (-ENOSPC))
-- 
2.47.0