Hi Hannes,
On 11/11/2015 11:34 AM, Hannes Reinecke wrote:
having been subjected to the pain of trying to bootstrap a really
large machine with systemd I decided to implement LUN masking in
This is very interesting.
I also thought about initiator-based LUN masking a while ago.
While scsi_transport_fc would be sufficient to allow zfcp to get rid of
its own implementation, I wonder why we wouldn't do it in the midlayer's
scsi_scan.c. This would provide initiator-based LUN masking for any and
all transports and LLDDs?
(I also thought about initiator-based zoning, and that would indeed be
something for scsi_transport_fc because it is inherently transport
specific.)
scsi_transport_fc.
The principle is simple: disallow the automated LUN scanning when
discovering a rport, and create udev rules which selectively
enable individual LUNs by echoing the relevant values in the 'scan'
attribute of the SCSI host.
I imagined exactly the same existing user space interface.
Now we "only" need some user-friendly user space tooling, which provides
transport specific user arguments automatically translated into the
midlayer naming scheme, such as converting FC SAN addressing (HBA device
bus-ID,WWPN,FCPLUN) into scsi_device names (Scsi_Host,0,scsi_id,scsi_lun),
and some persistency mechanism (such as managing udev rules).
With that I'm able to boot an arbitrary large machine without
running into any udev or systemd imposed timeout.
To _disable_ LUN masking and restoring the original behaviour
I've noticed that the 'scan' sysfs attribute is actually synchronous,
ie the calling process will be blocked until the entire LUN scan
is completed.
So I've added another module parameter 'async_user_scan' to
move the scanning onto the existing scan workqueue, and unblock
the calling process.
Just curious: Which means would a user of async_user_scan have to sync
against the completion?
Or is this only meant for user space--I currently cannot imagine--which
does not care about the appearance of what was (newly) discovered?
As usual, comments and reviews are welcome.
Hannes Reinecke (2):
scsi_transport_fc: implement 'disable_target_scan' module parameter
scsi_transport_fc: Implement 'async_user_scan' module parameter
drivers/scsi/scsi_transport_fc.c | 47 +++++++++++++++++++++++++++++++++++++---
1 file changed, 44 insertions(+), 3 deletions(-)
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Mit freundlichen Grüßen / Kind regards
Steffen Maier
Linux on z Systems Development
IBM Deutschland Research & Development GmbH
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschaeftsfuehrung: Dirk Wittkopp
Sitz der Gesellschaft: Boeblingen
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