Date:2010-05-07 11:44:26 (12 years 4 months ago)
Author:NeilBrown
Commit:1176568de7e066c0be9e46c37503b9fd4730edcf
Message:md: restore ability of spare drives to spin down.

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>
Cc: stable@kernel.org
Files: drivers/md/md.c (1 diff)

Change Details

drivers/md/md.c
21092109        if (!mddev->in_sync || mddev->recovery_cp != MaxSector) { /* not clean */
21102110            /* .. if the array isn't clean, an 'even' event must also go
21112111             * to spares. */
2112            if ((mddev->events&1)==0)
2112            if ((mddev->events&1)==0) {
21132113                nospares = 0;
2114                sync_req = 2; /* force a second update to get the
2115                           * even/odd in sync */
2116            }
21142117        } else {
21152118            /* otherwise an 'odd' event must go to spares */
2116            if ((mddev->events&1))
2119            if ((mddev->events&1)) {
21172120                nospares = 0;
2121                sync_req = 2; /* force a second update to get the
2122                           * even/odd in sync */
2123            }
21182124        }
21192125    }
21202126

Archive Download the corresponding diff file



interactive