scsi_free_sdev and slave destroy

Hi,
I was going through the function
scsi_probe_and_add_lun().
It does
scsi_alloc_sdev
probe for the lun
If lun does not exist call scsi_free_sdev.

scsi_alloc_sdev calls slave_alloc of the HBA driver where as scsi_free_sdev does not seem to call slave_destroy. Please let me know if this is a bug or I am missing something.

Thanx
N.C.Krishna Murthy

This is a current bug and is fixed in the latest scsi patch set.

James

Hi,

scsi_probe_lun() does find out whether a target is SCSI_2 or SCSI_3. The follg is the code from the function which does that.

-------------------------------------------

sdev->scsi_level = inq_result[2] & 0x07;
        if (sdev->scsi_level >= 2 ||
            (sdev->scsi_level == 1 && (inq_result[3] & 0x0f) == 1))
                sdev->scsi_level++;

---------------------------------------------
Looks like this information is not preserved long enough to be used properly in case LUN 0 is offline.

The follg is the call sequence

scsi_scan_host_selected()

	|
scsi_scan_channel()
	|

scsi_scan_target() ->

			res = scsi_probe_and_add_lun ( lun 0)
			if res == SCSI_SCAN_TARGET_PRESENT
				scsi_sequential_lun_scan

scsi_probe_and_add_lun() calls scsi_probe_lun(). In case there is no lun 0 then the information about scsi_level is lost.
----------------------------------------------------------------------
/*
* result contains valid SCSI INQUIRY data.
*/
if ((result[0] >> 5) == 3) {
/*
* For a Peripheral qualifier 3 (011b), the SCSI
* spec says: The device server is not capable of
* supporting a physical device on this logical
* unit.
*
* For disks, this implies that there is no
* logical disk configured at sdev->lun, but there
* is a target id responding.
*/
SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO
"scsi scan: peripheral qualifier of
3,"

                                        " no device added\n"));
                res = SCSI_SCAN_TARGET_PRESENT;
                goto out_free_result;
        }

------------------------------------------------------------------------------
We now call scsi_sequential_lun_scan() with BLIST_SPARSELUN,SCSI_2 as parameters, which instead should have been bflags,scsi_level as determined by scsi_probe_lun.

Isn't this is a bug? Please let me know if I am missing something.

Thanx
N.C.Krishna Murthy

Hi,
In scsi_probe_and_add_lun we check for Peripheral qualifier 3 (011b).
----------------------------------------------------------------------
/*
* result contains valid SCSI INQUIRY data.
*/
if ((result[0] >> 5) == 3) {
/*
* For a Peripheral qualifier 3 (011b), the SCSI
* spec says: The device server is not capable of
* supporting a physical device on this logical
* unit.
*
* For disks, this implies that there is no
* logical disk configured at sdev->lun, but there
* is a target id responding.
*/
SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO
"scsi scan: peripheral qualifier of
3,"

                                        " no device added\n"));
                res = SCSI_SCAN_TARGET_PRESENT;
                goto out_free_result;
        }

------------------------------------------------------------------------------
Shouldn't the same apply for peripheral qualifier 1. This is what the SCSI spec has to say about 1:
The device server is capable of supporting specified peripheral device type on this logical unit. However the physical device is currently not connected to this logical unit.

Thanx
N.C.Krishna Murthy

We handle PQ 1 later, because it indicates a transient connection condition. See scsi_add_lun().

James

SAM-3 in section 4.9.2 begins "All SCSI devices shall accept LUN 0 as a valid address...".

This requirement is in SCSI-2 as well.

If your implementation doesn't do this, I suggest you fix it.

If lun 0 responds (as it is required by the standards to do), but shows only a perfunctory standards conforming response indicating it's not really present, we scan, and the scsi_level will be recorded for each correctly scanned lun.

No, it's deliberate. Whether we should do this is open to debate, but there's a comment in the code explaining the logic:

/*
* There's a target here, but lun 0 is offline so we
* can't use the report_lun scan. Fall back to a
* sequential lun scan with a bflags of SPARSELUN and
* a default scsi level of SCSI_2
*/

James

Hi,
What I intended to say was in case we get 3 as the peripheral qualifier
in response to inquiry on lun 0, shouldn't we use the scsi level as returned in inquiry response instead of using a a default scsi level of SCSI_2.

Thanx
N.C.Krishna Murthy

It's open to debate whether a device reporting PQ 3 is required to fill in all the rest of the inquiry data correctly. The code takes the most conservative view.

James