scsi: sd: Clear sdkp->protection_type if disk is reformatted without PI

If an attached disk with protection information enabled is reformatted
to Type 0 the revalidation code does not clear the original protection
type and subsequent accesses will keep setting RDPROTECT/WRPROTECT.

Set the protection type to 0 if the disk reports PROT_EN=0 in READ
CAPACITY(16).

[mkp: commit desc]

Fixes: fe54239 ("[SCSI] sd: Ensure we correctly disable devices with unknown protection type")
Link: https://lore.kernel.org/r/1578532344-101668-1-git-send-email-chenxiang66@hisilicon.com
Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/sd.c

@@ -2211,8 +2211,10 @@ static int sd_read_protection_type(struct scsi_disk *sdkp, unsigned char *buffer
 	u8 type;
 	int ret = 0;
 
-	if (scsi_device_protection(sdp) == 0 || (buffer[12] & 1) == 0)
+	if (scsi_device_protection(sdp) == 0 || (buffer[12] & 1) == 0) {
+		sdkp->protection_type = 0;
 		return ret;
+	}
 
 	type = ((buffer[12] >> 1) & 7) + 1; /* P_TYPE 0 = Type 1 */