qla2xxx: added sess generations to detect RSCN update races

RSCN processing in qla2xxx driver can run in parallel with ELS/IO
processing. As such the decision to remove disappeared fc port's
session could be stale, because a new login sequence has occurred
since and created a brand new session.

Previous mechanism of dealing with this by delaying deletion request
was prone to erroneous deletions if the event that was supposed to
cancel the deletion never arrived or has been delayed in processing.

New mechanism relies on a time-like generation counter to serialize
RSCN updates relative to ELS/IO updates.

Cc: <stable@vger.kernel.org> # v3.18+
Signed-off-by: Alexei Potashnik <alexei@purestorage.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@qlogic.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Alexei Potashnik 2015-07-14 16:00:46 -04:00 • committed by Nicholas Bellinger
commit df673274fa
6 changed files with 83 additions and 26 deletions