[SCSI] libsas: prevent domain rediscovery competing with ata error handling
libata error handling provides for a timeout for link recovery. libsas must not rescan for previously known devices in this interval otherwise it may remove a device that is simply waiting for its link to recover. Let libata-eh make the determination of when the link is stable and prevent libsas (host workqueue) from taking action while this determination is pending. Using a mutex (ha->disco_mutex) to flush and disable revalidation while eh is running requires any discovery action that may block on eh be moved to its own context outside the lock. Probing ATA devices explicitly waits on ata-eh and the cache-flush-io issued during device removal may also pend awaiting eh completion. Essentially any rphy add/remove activity needs to run outside the lock. This adds two new cleanup states for sas_unregister_domain_devices() 'allocated-but-not-probed', and 'flagged-for-destruction'. In the 'allocated-but-not-probed' state dev->rphy points to a rphy that is known to have not been through a sas_rphy_add() event. At domain teardown check if this device is still pending probe and cleanup accordingly. Similarly if a device has already been queued for removal then sas_unregister_domain_devices has nothing to do. Signed-off-by:Dan Williams <dan.j.williams@intel.com> Signed-off-by: