Benjamin Block 04be704083 chreipl-fcp-mpath: record the event subject WWID if it repr. the tgt ...

When we have identified the current event subject to represent the
re-IPL target, we record its WWID for future identification in a
stateful ID-file (per default: /run/udev/chreiplzfcpmp-ipl-volume-id). In
addition to the WWID, we also record the current re-IPL triplet
(<Dev-Bus-ID>:<WWPN>:<LUN>), so that when that changes - e.g. due to an
operator manually changing the re-IPL target -, we know that the
recorded WWID is stale.

This record may be used in cases when the current re-IPL target is
completely gone from the system, so we can't used it as comparison
object for when events arrive for paths that go to the same volume, but
don't have the same I_T_L nexus. They however have the same WWID. We
may use these (new) paths as replacement for the one that is completely
gone.

The new helper `chreipl-fcp-mpath-record-volume-identifier` uses the
kernel scsi-device attribute `wwid` as source for the WWID (verbatim).

As with reading the re-IPL firmware information, when writing to the
ID-file, a lock is taken via `flock`, to prevent overlapping
writes/reads to the file.

Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

2021-11-10 15:12:10 +01:00

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