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    Subject[83/98] md: restore ability of spare drives to spin down.
    2.6.32-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: NeilBrown <neilb@suse.de>

    commit 1176568de7e066c0be9e46c37503b9fd4730edcf upstream.

    Some time ago we stopped the clean/active metadata updates
    from being written to a 'spare' device in most cases so that
    it could spin down and say spun down. Device failure/removal
    etc are still recorded on spares.

    However commit 51d5668cb2e3fd1827a55 broke this 50% of the time,
    depending on whether the event count is even or odd.
    The change log entry said:

    This means that the alignment between 'odd/even' and
    'clean/dirty' might take a little longer to attain,

    how ever the code makes no attempt to create that alignment, so it
    could take arbitrarily long.

    So when we find that clean/dirty is not aligned with odd/even,
    force a second metadata-update immediately. There are already cases
    where a second metadata-update is needed immediately (e.g. when a
    device fails during the metadata update). We just piggy-back on that.

    Reported-by: Joe Bryant <tenminjoe@yahoo.com>
    Signed-off-by: NeilBrown <neilb@suse.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/md/md.c | 10 ++++++++--
    1 file changed, 8 insertions(+), 2 deletions(-)

    --- a/drivers/md/md.c
    +++ b/drivers/md/md.c
    @@ -2011,12 +2011,18 @@ repeat:
    if (!mddev->in_sync || mddev->recovery_cp != MaxSector) { /* not clean */
    /* .. if the array isn't clean, an 'even' event must also go
    * to spares. */
    - if ((mddev->events&1)==0)
    + if ((mddev->events&1)==0) {
    nospares = 0;
    + sync_req = 2; /* force a second update to get the
    + * even/odd in sync */
    + }
    } else {
    /* otherwise an 'odd' event must go to spares */
    - if ((mddev->events&1))
    + if ((mddev->events&1)) {
    nospares = 0;
    + sync_req = 2; /* force a second update to get the
    + * even/odd in sync */
    + }
    }
    }




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