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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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