Bug 619375

+++ This bug was initially created as a clone of Bug #619361 +++

Description of problem:
The SCSI ALUA handler does not handle ALUA transitioning states properly. For eg. for an ALUA enabled NetApp controller which supports implicit ALUA alone (with the following valid states - port group 00 state A supports ToUsNA), the following code snippet is seen in alua_rtpg:

if (h->tpgs & TPGS_MODE_EXPLICIT) {
        switch (h->state) {
        case TPGS_STATE_TRANSITIONING:
                /* State transition, retry */
                goto retry;
                break;
        case TPGS_STATE_OFFLINE:
                /* Path is offline, fail */
                err = SCSI_DH_DEV_OFFLINED;
                break;
        default:
                break;
        }
} else {
        /* Only Implicit ALUA support */
        if (h->state == TPGS_STATE_OPTIMIZED ||
            h->state == TPGS_STATE_NONOPTIMIZED ||
            h->state == TPGS_STATE_STANDBY)
                /* Useable path if active */
                err = SCSI_DH_OK;
        else
                /* Path unuseable for unavailable/offline */
                err = SCSI_DH_DEV_OFFLINED;
}

During NetApp controller faults, the lun is in 'transitioning' state. But from the above code, it seems this is handled for explicit ALUA alone, and not for implicit ALUA. It should have ideally handled this for both.

Secondly, in the alua_prep_fn:

if (h->state != TPGS_STATE_OPTIMIZED && h->state != TPGS_STATE_NONOPTIMIZED) {
        ret = BLKPREP_KILL;
        req->flags |= REQ_QUIET;
}

Why is TPGS_STATE_TRANSITIONING not handled above? For this state, I suppose the prep_fn should be returning BLKPREP_DEFER.

Because of these issues with the ALUA handler, we seem to have hit delayed dm-multipath IO (on SCSI devices using the ALUA handler) as described in bug 606259. 

Version-Release number of selected component (if applicable):
2.6.32-30.el6 (RHEL 6.0 Snap6)