[Bug 111441] iscsi fails to attach to targets

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https://bugzilla.kernel.org/show_bug.cgi?id=111441

--- Comment #13 from nab <nab@linux-iscsi.org> ---
On Mon, 2016-02-01 at 10:55 -0600, Mike Christie wrote:
> On 01/30/2016 01:38 AM, Nicholas A. Bellinger wrote:
> > On Fri, 2016-01-29 at 17:32 -0600, Mike Christie wrote:
> >> On 01/29/2016 04:21 PM, Serguei Bezverkhi (sbezverk) wrote:
> >>> HI Mike,
> >>>
> >>> I tried your patch and it is has eliminated first traceback but I still do not see my remote targets.
> >>>
> >>
> >> That is sort of expected. Your target is not setup for ALUA properly. It
> >> says it supports ALUA, but when scsi_dh_alua asks about the ports it is
> >> reporting there are none. Ccing the people that made the patch that
> >> added the issue and own the code.
> >>
> >> Hey Christoph and Hannes,
> >>
> >> The dh/alua changes that added this:
> >>
> >>         error = scsi_dh_add_device(sdev);
> >>         if (error) {
> >>                 sdev_printk(KERN_INFO, sdev,
> >>                                 "failed to add device handler: %d\n",
> >> error);
> >>                 return error;
> >>         }
> >>
> >> to scsi_sysfs_add_sdev are adding a regression.
> >>
> >> 1. If that fails, then we forget to do device_del before doing the
> >> return. My patch in this thread added that back, so we do not see the
> >> sysfs oopses anymore. But.....
> >>
> >> 2. It looks like in older kernels, we would allow misconfigured targets
> >> like this one to still setup devices. Do we want that old behavior back?
> >> Should we just ignore the return value from scsi_dh_add_device above?
> >> Note that in this case, it is LIO so it can be easily fixed on the
> >> target side by just setting it up properly. I do not think other targets
> >> would hit this type of issue.
> >>
> > 
> > Btw, what does misconfigured mean here wrt target ALUA..?
> 
> [   25.833195] sd 6:0:0:4: alua: supports implicit and explicit TPGS
> [   25.833360] sd 6:0:0:4: alua: No target port descriptors found
> [   25.833363] sd 6:0:0:4: alua: Attach failed (-22)
> [   25.833365] sd 6:0:0:4: failed to add device handler: -22
> 

Strange, this hasn't changed in forever on the target side..

> He has LIO configured to report it supports implicit/explicit ALUA, but
> the ports do not seem to be configured.
> 
> For the LIO config side, are his LUNs just not in a the default_lu_gp or
> any other group?

So every non-PSCSI backend device becomes part of default_lu_gp +
default_tg_pt_gp and automatically shows up in EVPD=0x83, without user
needing to do any additional configuration.

Here's what the output looks like:

root@haakon3:/usr/src/target-pending.git# sg_inq -Hi /dev/sdb
VPD INQUIRY: Device Identification page
  <SNIP>
  Designation descriptor number 3, descriptor length: 8
    transport: Serial Attached SCSI Protocol (SPL-2)
    designator_type: Relative target port,  code_set: Binary
    associated with the target port
    designator header(hex): 61 94 00 04
    designator:
 00     00 00 00 02                                         ....
  Designation descriptor number 4, descriptor length: 8
    transport: Serial Attached SCSI Protocol (SPL-2)
    designator_type: Target port group,  code_set: Binary
    associated with the target port
    designator header(hex): 61 95 00 04
    designator:
 00     00 00 00 00                                         ....
  Designation descriptor number 5, descriptor length: 8
    designator_type: Logical unit group,  code_set: Binary
    associated with the addressed logical unit
    designator header(hex): 01 06 00 04
    designator:
 00     00 00 00 00                                         ....
 <SNIP>

So AFAICT, the relative target port, target port group, and logical unit
group being returned from target on v4.5-rc1 code looks correct.

Serguei, can you confirm with 'sg_inq -Hi /dev/sdX' output on your side
with the v3.10 based target..?

AFAICT the parsing in scsi_vpd_tpg_id() from commit a8aa3978 looks
correct too.

Hannes, any ideas..?

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