Skip to content

L
linux
Switch branch/tag
  1. 27 Nov, 2014 1 commit
  3. 25 Nov, 2014 11 commits
  5. 24 Nov, 2014 26 commits
  7. 20 Nov, 2014 2 commits
    • Martin Peschke's avatar
      zfcp: auto port scan resiliency · 18f87a67
      Martin Peschke authored 
      This patch improves the Fibre Channel port scan behaviour of the zfcp lldd.
Without it the zfcp device driver may churn up the storage area network by
excessive scanning and scan bursts, particularly in big virtual server
environments, potentially resulting in interference of virtual servers and
reduced availability of storage connectivity.

The two main issues as to the zfcp device drivers automatic port scan in
virtual server environments are frequency and simultaneity.
On the one hand, there is no point in allowing lots of ports scans
in a row. It makes sense, though, to make sure that a scan is conducted
eventually if there has been any indication for potential SAN changes.
On the other hand, lots of virtual servers receiving the same indication
for a SAN change had better not attempt to conduct a scan instantly,
that is, at the same time.

Hence this patch has a two-fold approach for better port scanning:
the introduction of a rate limit to amend frequency issues, and the
introduction of a short random backoff to amend simultaneity issues.
Both approaches boil down to deferred port scans, with delays
comprising parts for both approaches.

The new port scan behaviour is summarised best by:

                                               NEW:    NEW:
                          no_auto_port_rescan  random  rate    flush
                                               backoff limit   =wait

adapter resume/thaw       yes                  yes     no      yes*
adapter online (user)     no                   yes     no      yes*
port rescan (user)        no                   no      no      yes
adapter recovery (user)   yes                  yes     yes     no
adapter recovery (other)  yes                  yes     yes     no
incoming ELS              yes                  yes     yes     no
incoming ELS lost         yes                  yes     yes     no

Implementation is straight-forward by converting an existing worker to
a delayed worker. But care is needed whenever that worker is going to be
flushed (in order to make sure work has been completed), since a flush
operation cancels the timer set up for deferred execution (see * above).

There is a small race window whenever a port scan work starts
running up to the point in time of storing the time stamp for that port
scan. The impact is negligible. Closing that gap isn't trivial, though, and
would the destroy the beauty of a simple work-to-delayed-work conversion.
Signed-off-by: default avatarMartin Peschke <mpeschke@linux.vnet.ibm.com>
Signed-off-by: default avatarSteffen Maier <maier@linux.vnet.ibm.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      18f87a67
    • Steffen Maier's avatar
      zfcp: bring back unit sysfs attributes for automatic LUN scan · c8bba144
      Steffen Maier authored 
      Through sysfs attributes, zfcp unit objects
provide a trigger for manual LUN recovery
and export information for problem determination.

With commit
f8210e34
"[SCSI] zfcp: Allow midlayer to scan for LUNs when running in NPIV mode"
and when attaching SCSI devices through this new optional method,
no more zfcp unit objects are allocated for such SCSI devices.
Hence, the above-mentioned trigger and information were missing.

The information and context is located in SCSI transport device data since
b62a8d9b
"[SCSI] zfcp: Use SCSI device data zfcp_scsi_dev instead of zfcp_unit"
57c23773
"[SCSI] zfcp: Add zfcp private struct as SCSI device driver data"
Hence, introduce the trigger and the information unconditionally
for all SCSI devices attached through zfcp.

We prefix the attribute names with 'zfcp_' to prevent collisions and
to avoid mix-ups such as with the common 'state' attribute.

Since some of the new attribute views do not need zfcp_port
in the ZFCP_DEFINE_SCSI_ATTR helper macro, remove zfcp_port
to avoid compiler warnings on unused variable.
It's easy to open code the conversion from zfcp_scsi_dev to zfcp_port
for the two already existing attributes hba_id and wwpn.
Signed-off-by: default avatarSteffen Maier <maier@linux.vnet.ibm.com>
Reviewed-by: default avatarMartin Peschke <mpeschke@linux.vnet.ibm.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      c8bba144
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7