Date: Fri, 15 Sep 2006 17:03:21 -0500 From: Mike Christie <mchristi@redhat.com> Subject: [PATCH RHEL5] don't create scsi_device at lun0 for pq=1 This is for BZ 205802. Targets like Netapp, return PQ=1 for LUN 0 if the LUN is not mapped. PQ=1 means: The device server is capable of supporting the specified peripheral device type on this logical unit. However, the physical device is not currently connected to this logical unit. Currently scsi-ml will create a sort of dummy scsi_device when PQ=1 is returned. Later if the usr maps a device to LUN0 and wants to rescan, scsi-ml will just detect the dummy device (but not that it is a dummy device) and skip rescanning it. The attached patch modifies scsi-ml so that devices are not created when PQ=1. It is upstream in the scsi maintainer's tree for 2.6.19. I have only done some basic testing by connecting devices and making sure they are scanned and that this fixes the problem on netapp targets. --- a/drivers/scsi/scsi_scan.c 2006-07-15 17:53:08.000000000 -0400 +++ b/drivers/scsi/scsi_scan.c 2006-08-09 14:01:20.000000000 -0400 @@ -943,11 +943,26 @@ static int scsi_probe_and_add_lun(struct } /* - * Non-standard SCSI targets may set the PDT to 0x1f (unknown or - * no device type) instead of using the Peripheral Qualifier to - * indicate that no LUN is present. For example, USB UFI does this. + * Some targets may set slight variations of PQ and PDT to signal + * that no LUN is present, so don't add sdev in these cases. + * Two specific examples are: + * 1) NetApp targets: return PQ=1, PDT=0x1f + * 2) USB UFI: returns PDT=0x1f, with the PQ bits being "reserved" + * in the UFI 1.0 spec (we cannot rely on reserved bits). + * + * References: + * 1) SCSI SPC-3, pp. 145-146 + * PQ=1: "A peripheral device having the specified peripheral + * device type is not connected to this logical unit. However, the + * device server is capable of supporting the specified peripheral + * device type on this logical unit." + * PDT=0x1f: "Unknown or no device type" + * 2) USB UFI 1.0, p. 20 + * PDT=00h Direct-access device (floppy) + * PDT=1Fh none (no FDD connected to the requested logical unit) */ - if (starget->pdt_1f_for_no_lun && (result[0] & 0x1f) == 0x1f) { + if (((result[0] >> 5) == 1 || starget->pdt_1f_for_no_lun) && + (result[0] & 0x1f) == 0x1f) { SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO "scsi scan: peripheral device type" " of 31, no device added\n"));