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When we get an unsolicited notification on local link went down,
zfcp_fsf_status_read_link_down() calls zfcp_fsf_link_down_info_eval().
This only blocks rports, and sets ZFCP_STATUS_ADAPTER_LINK_UNPLUGGED and
ZFCP_STATUS_COMMON_ERP_FAILED. Only the fc_host port_state changes to
"Linkdown", because zfcp_scsi_get_host_port_state() is an active callback
and uses the adapter status.
Other fc_host attributes model, port_id, port_type, speed, fabric_name (and
zfcp device attributes card_version, peer_wwpn, peer_wwnn, peer_d_id) which
depend on a local link, continued to show their last known "good" value.
Only if something triggered an exchange config data, some values were
updated to their unknown equivalent via case
FSF_EXCHANGE_CONFIG_DATA_INCOMPLETE due to local link down. Triggers for
exchange config data are adapter recovery, or reading any of the following
zfcp-specific scsi host sysfs attributes "requests", "megabytes", or
"seconds_active" in /sys/devices/css*/*.*.*/*.*.*/host*/scsi_host/host*/.
The other fc_host attributes active_fc4s and permanent_port_name continued
to show their last known "good" value. Only if something triggered an
exchange port data, some values changed. Active_fc4s became all zeros as
unknown equivalent during link down. Permanent_port_name does not depend
on a local link. But for non-NPIV FCP devices, permanent_port_name
erroneously became whatever value fc_host port_name had at that point in
time (see previous paragraph). Triggers for exchange port data are the
zfcp-specific scsi host sysfs attribute "utilization", or
[{reset,get}_fc_host_stats] write anything into "reset_statistics" or read
any of the other attributes under
/sys/devices/css*/*.*.*/*.*.*/host*/fc_host/host*/statistics/.
(cf. v4.9 commit bd77befa5b ("zfcp: fix fc_host port_type with NPIV"))
This is particularly confusing when using "lszfcp -b <fcpdevbusid> -Ha" or
dbginfo.sh which read fc_host attributes and also scsi_host attributes.
After link down, the first invocation produces (abbreviated):
Class = "fc_host"
active_fc4s = "0x00 0x00 0x01 0x00 ..."
...
fabric_name = "0x10000027f8e04c49"
...
permanent_port_name = "0xc05076e4588059c1"
port_id = "0x244800"
port_state = "Linkdown"
port_type = "NPort (fabric via point-to-point)"
...
speed = "16 Gbit"
Class = "scsi_host"
...
megabytes = "0 0"
...
requests = "0 0 0"
seconds_active = "37"
...
utilization = "0 0 0"
The second and next invocations produce (abbreviated):
Class = "fc_host"
active_fc4s = "0x00 0x00 0x00 0x00 ..."
...
fabric_name = "0x0"
...
permanent_port_name = "0x0"
port_id = "0x000000"
port_state = "Linkdown"
port_type = "Unknown"
...
speed = "unknown"
Class = "scsi_host"
...
megabytes = "0 0"
...
requests = "0 0 0"
seconds_active = "38"
...
utilization = "0 0 0"
Factor out the resetting of local link dependent fc_host attributes from
zfcp_fsf_exchange_config_data_handler() case
FSF_EXCHANGE_CONFIG_DATA_INCOMPLETE into a new helper function
zfcp_fsf_fc_host_link_down(). All code places that detect local link down
(SRB, FSF_PROT_LINK_DOWN, xconf data/port incomplete) call
zfcp_fsf_link_down_info_eval(). Call the new helper from there. This works
because zfcp_fsf_link_down_info_eval() and thus the helper is called before
zfcp_fsf_exchange_{config,port}_evaluate().
Port_name and node_name are always valid, so never reset them.
Get the permanent_port_name from exchange port data unconditionally as it
always has a valid known good value, even during link down.
Note: Rather than hardcode in zfcp_fsf_exchange_config_evaluate(), fc_host
supported_classes could theoretically get its value from
fsf_qtcb_bottom_port.class_of_service in zfcp_fsf_exchange_port_evaluate().
When the link comes back, we get a different notification, perform adapter
recovery, and this triggers an implicit exchange config data followed by
exchange port data filling in the link dependent fc_host attributes with
known good values again.
Link: https://lore.kernel.org/r/20200312174505.51294-5-maier@linux.ibm.com
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.