scsi: core: Remember if a device is an ATA device

scsi_add_lun() tests the device vendor string of SCSI devices to detect
if a SCSI device is in fact an ATA device, in order to correctly handle
SATL power management. The function scsi_cdl_enable() also requires
knowing if a SCSI device is an ATA device to control the state of the
device CDL feature but this function does that by testing for the
presence of the VPD page 89h (ATA INFORMATION page).
sd_read_write_same() also has a similar test.

Simplify these different methods by adding the is_ata field to struct
scsi_device to remember that a SCSI device is in fact an ATA one based
on the device vendor name test. This field can also allow low level
SCSI host adapter drivers to take special actions for ATA devices
(e.g. to better handle ATA NCQ errors).

With this, simplify scsi_cdl_enable() and sd_read_write_same().

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20250611093421.2901633-1-dlemoal@kernel.org
Reviewed-by: Igor Pylypiv <ipylypiv@google.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: damien-lemoal

drivers/scsi/scsi.c

@@ -708,20 +708,15 @@ void scsi_cdl_check(struct scsi_device *sdev)
 int scsi_cdl_enable(struct scsi_device *sdev, bool enable)
 {
 	char buf[64];
-	bool is_ata;
 	int ret;
 
 	if (!sdev->cdl_supported)
 		return -EOPNOTSUPP;
 
-	rcu_read_lock();
-	is_ata = rcu_dereference(sdev->vpd_pg89);
-	rcu_read_unlock();
-
 	/*
 	 * For ATA devices, CDL needs to be enabled with a SET FEATURES command.
 	 */
-	if (is_ata) {
+	if (sdev->is_ata) {
 		struct scsi_mode_data data;
 		struct scsi_sense_hdr sshdr;
 		char *buf_data;

drivers/scsi/scsi_scan.c

@@ -909,7 +909,8 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
 	sdev->model = (char *) (sdev->inquiry + 16);
 	sdev->rev = (char *) (sdev->inquiry + 32);
 
-	if (strncmp(sdev->vendor, "ATA     ", 8) == 0) {
+	sdev->is_ata = strncmp(sdev->vendor, "ATA     ", 8) == 0;
+	if (sdev->is_ata) {
 		/*
 		 * sata emulation layer device.  This is a hack to work around
 		 * the SATL power management specifications which state that

drivers/scsi/sd.c

@@ -3459,19 +3459,14 @@ static void sd_read_write_same(struct scsi_disk *sdkp, unsigned char *buffer)
 	}
 
 	if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, INQUIRY, 0) < 0) {
-		struct scsi_vpd *vpd;
-
 		sdev->no_report_opcodes = 1;
 
-		/* Disable WRITE SAME if REPORT SUPPORTED OPERATION
-		 * CODES is unsupported and the device has an ATA
-		 * Information VPD page (SAT).
+		/*
+		 * Disable WRITE SAME if REPORT SUPPORTED OPERATION CODES is
+		 * unsupported and this is an ATA device.
 		 */
-		rcu_read_lock();
-		vpd = rcu_dereference(sdev->vpd_pg89);
-		if (vpd)
+		if (sdev->is_ata)
 			sdev->no_write_same = 1;
-		rcu_read_unlock();
 	}
 
 	if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, WRITE_SAME_16, 0) == 1)

include/scsi/scsi_device.h

@@ -184,6 +184,11 @@ struct scsi_device {
 	 */
 	unsigned force_runtime_start_on_system_start:1;
 
+	/*
+	 * Set if the device is an ATA device.
+	 */
+	unsigned is_ata:1;
+
 	unsigned removable:1;
 	unsigned changed:1;	/* Data invalid due to media change */
 	unsigned busy:1;	/* Used to prevent races */