After some changes to the FC connector we have introduced a regression
on the way we do the scans, and we end up scanning using wildcards even
though we shouldn't.
The targets in the "initiator_target_map" don't mean that they are all
connected, so we must take that into account.
With the current code, if we have the following connections:
HBA host7 ---- SWITCH ---- port W (channel 0, target 2)
\--- SWITCH ---- port X (channel 0, target 3)
HBA host8 ---- SWITCH ---- port Y (channel 0, target 2)
\--- SWITCH ---- port Z (channel 0, target 3)
We will end up with the following scans 8 scans for LUN L:
- - L > host7
- - L > host7
0 2 L > host7
0 3 L > host7
0 2 L > host8
0 3 L > host8
- - L > host8
- - L > host8
Which correspond to the responses from _get_hba_channel_scsi_target like
this:
port Y port Z port W port X
host7 ... ['-','-',L] ['-','-',L] ['0','2',L] ['0','3',L]
host8 ... ['0','2',L] ['0','3',L] ['-','-',L] ['-','-',L]
And we should only be doing 4 scans:
0 2 L > host7
0 3 L > host7
0 2 L > host8
0 3 L > host8
Most storage arrays get their target ports automatically detected by the
Linux FC initiator and sysfs gets populated with that information, but
there are some that don't.
We'll do a narrow scan using the channel, target, and LUN for the former
and a wider scan for the latter.
If all paths to a former type of array were down on the system boot the
array could look like it's of the latter type and make us bring us
unwanted volumes into the system by doing a broad scan.
To prevent this from happening Cinder drivers can use the
"enable_wildcard_scan" key in the connection information to let us know
they don't want us to do broad scans even if no target ports are found
(because they know the cause is there's no connection).
Close-Bug: #1849504
Related-Bug: #1765000
Related-Bug: #1828440
Change-Id: I5dbefaff43fb902b15117b443fc92f7b6a6ad8c9
708733e495