Re: [PATCH] make the SCSI mid-layer obey the device online flag

[Luben Tuikov <tluben@rogers.com>]

James Bottomley wrote:
> Surprise ejection:
> 
> driver starts returning DID_NO_CONNECT to commands
> possibly hotplug notify of surprise ejection
> device->online to be reset
> command queue drains
> command queue drops to zero, ->remove can be called and everything
> cleaned up from user level (including remove-single-device)
> 
> Nice ejection:
> 
> hotplug notify of ejection request
> eject script cleans up, unmounts, possibly resets online
> command queue drains
> command queue drops to zero, ->remove can be called and everything
> cleaned up from user level (including remove-single-device)
> ejection may now proceed

Exactly right!  (This is ``ejection'' of a device off the SAN.)
 
> For the remove_host scenario, it would be convenient just to do
> nice/surprise ejections on all the devices (from user level) and then do
> the clean up when the hosts device count falls to zero.  That may imply
> some type of host->offline flag which disallows the addition of new scsi
> devices to the host.

Just to be clear: this is when a PCI host (SCSI portal) becomes
unavailable. (quite different from the above)

In which case SCSI host should NOT call the queuecommand
(it being a property of the portal) and if user space drivers submit
commands to a device there of or the host, SCSI Core should return said
commands with response SERVICE DELIVERY OR TARGET FAILURE (this is NOT
the status SAM_xxx).

-- 
Luben