On Wed, Aug 18, 2010 at 8:13 AM, James Bottomley <James.Bottomley@xxxxxxx> wrote: > On Wed, 2010-08-18 at 08:10 -0700, Richard Sharpe wrote: >> On Sun, Aug 15, 2010 at 5:08 PM, <realrichardsharpe@xxxxxxxxx> wrote: >> > From: Richard Sharpe <realrichardsharpe@xxxxxxxxx> >> > >> > If the target returns logical_unit_not_supported when we send REPORT LUNS >> > it means that it supports REPORT LUNS but there really are no LUNs there. >> > Delete LUN 0 in that case. >> > >> > Also, when parsing the LUNs reported, remove any LUNs that used to exist >> > in the gaps, and remove LUNs beyond the end of those reported. They no >> > longer exist. >> > >> > Also don't scan a target where the ID is too large or the channel is >> > too large. >> > >> > Tested by adding four LUNs with scst_local and then deleting them in >> > various combinations, including deleting from LUN 0, deleting from last >> > LUN and deleting in the middle out. >> >> Hmmm, before James responds, it turns out that I did not test as >> carefully as I thought, and deleting LUNs in the order 0, 2, ... does >> not produce the results I expected, so I will have to rework this. > > OK, so I think what I'd really like is an AEN notification > infrastructure based on the unit attentions that bubbles this up to user > space for a decision. That way if user space does the removal, we're > not going to get into locking or other problems. Having looked at this some more, I think that I chose the wrong way to go about this. What I think should happen is that the target (in my case scst_local, which is both a SCSI LLD and a SCSI target driver that hooks into SCST) should establish a UNIT ATTENTION condition with an ASC of REPORTED LUNS DATA HAS CHANGED (ASC = 3Fh ASCQ = 0Eh). This should be detected by the SCSI stack which should then do a REPORT LUNS scan and do the appropriate things (like cancel any submitted requests for LUNs that no longer exist. Does this sound reasonable? -- Regards, Richard Sharpe -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
