• Salyzyn, Mark's avatar
    [SCSI] aacraid: add support for FUA · 9d399cc7
    Salyzyn, Mark authored
    Back in the beginning of last year we disabled mode page 8 and mode page
    3f requests through device quirk bits instead of enhancing the driver to
    respond to these mode pages because there was no apparent added value.
    
    The Firmware that supports the new communication commands supports the
    ability to force a write around of the adapter cache on a command by
    command basis. In the attached patch we enable mode page 8 and 3f and
    spoof the results as needed in order to *convince* the layers above to
    submit writes with the FUA (Force Unit Attention) bit set if the file
    system or application requires it, if the Firmware supports the write
    through, or instead to submit a SYNCHRONIZE_CACHE if the Firmware does
    not. The added value here is for file systems that benefit from this
    functionality and for clustering or redundancy scenarios.
    
    Caveats: By convince, we are responding with a minimal short 3 byte
    content mode page 8, with only the data the SCSI layer needs and that we
    can fill confidently. Applications that require the customarily larger
    mode page 8 results may be confused by this(?). The FUA, or the
    SYNCHRONIZE_CACHE only affect the cache on the controller. Our firmware
    by default ensure that the underlying physical drives of the array have
    their cache turned off so normally this is not a problem.
    
    This attached patch is against current scsi-misc-2.6 and was unit tested
    on RHEL5. Since this is a feature enhancement, it should not be
    considered for any current stabilization efforts.
    Signed-off-by: default avatarMark Salyzyn <aacraid@adaptec.com>
    Signed-off-by: default avatarJames Bottomley <James.Bottomley@SteelEye.com>
    9d399cc7
aachba.c 75.4 KB