MFC: 332385

MFC: 332385

r332385:
    hyperv/storvsc: storvsc_io_done(): do not use CAM_SEL_TIMEOUT

    CAM_SEL_TIMEOUT was introduced in
    https://reviews.freebsd.org/D7521 (r304251), which claimed:

    "VM shall response to CAM layer with CAM_SEL_TIMEOUT to filter those
    invalid LUNs. Never use CAM_DEV_NOT_THERE which will block LUN scan
    for LUN number higher than 7."

    But it turns out this is not correct:

    I think what really filters the invalid LUNs in r304251 is that:
    before r304251, we could set the CAM_REQ_CMP without checking
    vm_srb->srb_status at all:
    ccb->ccb_h.status |= CAM_REQ_CMP.

    r304251 checks vm_srb->srb_status and sets ccb->ccb_h.status properly,
    so the invalid LUNs are filtered.

    I changed my code version to r304251 but replaced the CAM_SEL_TIMEOUT
    with CAM_DEV_NOT_THERE, and I confirmed the invalid LUNs can also be
    filtered, and I successfully hot-added and hot-removed 8 disks to/from
    the VM without any issue.

    CAM_SEL_TIMEOUT has an unwanted side effect -- see cam_periph_error():
    For a selection timeout, we consider all of the LUNs on
    the target to be gone. If the status is CAM_DEV_NOT_THERE,
    then we only get rid of the device(s) specified by the
    path in the original CCB.

    This means: for a VM with a valid LUN on 3:0:0:0, when the VM inquires
    3:0:0:1 and the host reports 3:0:0:1 doesn't exist and storvsc returns
    CAM_SEL_TIMEOUT to the CAM layer, CAM will detech 3:0:0:0 as well: this
    is the bug I reported recently:
    https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=226583

    PR:     226583
    Reviewed by:    mav
    Sponsored by:   Microsoft
    Differential Revision:  https://reviews.freebsd.org/D14690

git-svn-id: svn://svn.freebsd.org/base/stable/10@332904 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f