linux-kernel - [PATCH v3 3/6] esp_scsi: Grant disconnect privilege for untagged commands

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Message-Id: <4208077979dff12471046ab27be1d7a89887d1d3.1539667885.git.fthain@telegraphics.com.au>
Date:   Tue, 16 Oct 2018 16:31:25 +1100
From:   Finn Thain <fthain@...egraphics.com.au>
To:     "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     Michael Schmitz <schmitzmic@...il.com>,
        Hannes Reinecke <hare@...e.de>, linux-scsi@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 3/6] esp_scsi: Grant disconnect privilege for untagged
 commands

A SCSI device is not granted disconnect privilege by an esp_scsi host
unless that device has its simple_tags flag set. However, a device may
support disconnect/reselect and not support command queueing. Allow
such devices to disconnect and thereby improve bus utilization.

Drop the redundant 'lp' check. The mid-layer invokes .slave_alloc and
.slave_destroy in such a way that we may rely on scmd->device->hostdata
for as long as scmd belongs to the low-level driver.

Tested-by: Stan Johnson <userm57@...oo.com>
Signed-off-by: Finn Thain <fthain@...egraphics.com.au>
Tested-by: Michael Schmitz <schmitzmic@...il.com>
---
Changed since v2:
 - Drop redundant 'lp' check.
---
 drivers/scsi/esp_scsi.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
index 9e5d3f7d29ae..5b24aa21a797 100644
--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -717,7 +717,6 @@ static struct esp_cmd_entry *find_and_prep_issuable_command(struct esp *esp)
 static void esp_maybe_execute_command(struct esp *esp)
 {
 	struct esp_target_data *tp;
-	struct esp_lun_data *lp;
 	struct scsi_device *dev;
 	struct scsi_cmnd *cmd;
 	struct esp_cmd_entry *ent;
@@ -743,7 +742,6 @@ static void esp_maybe_execute_command(struct esp *esp)
 	tgt = dev->id;
 	lun = dev->lun;
 	tp = &esp->target[tgt];
-	lp = dev->hostdata;
 
 	list_move(&ent->list, &esp->active_cmds);
 
@@ -799,14 +797,7 @@ static void esp_maybe_execute_command(struct esp *esp)
 	}
 
 build_identify:
-	/* If we don't have a lun-data struct yet, we're probing
-	 * so do not disconnect.  Also, do not disconnect unless
-	 * we have a tag on this command.
-	 */
-	if (lp && (tp->flags & ESP_TGT_DISCONNECT) && ent->tag[0])
-		*p++ = IDENTIFY(1, lun);
-	else
-		*p++ = IDENTIFY(0, lun);
+	*p++ = IDENTIFY(tp->flags & ESP_TGT_DISCONNECT, lun);
 
 	if (ent->tag[0] && esp->rev == ESP100) {
 		/* ESP100 lacks select w/atn3 command, use select
-- 
2.18.1