md: allow parallel resync of md-devices.

In some configurations, a raid6 resync can be limited by CPU speed
(Calculating P and Q and moving data) rather than by device speed.  In
these cases there is nothing to be gained byt serialising resync of arrays
that share a device, and doing the resync in parallel can provide benefit.
 So add a sysfs tunable to flag an array as being allowed to resync in
parallel with other arrays that use (a different part of) the same device.

Signed-off-by: Bernd Schubert <bs@q-leap.de>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 812ffa590cf..a6d7ab688ed 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -180,6 +180,9 @@ struct mddev_s
         int                             sync_speed_min;
         int                             sync_speed_max;
 
+        /* resync even though the same disks are shared among md-devices */
+        int                             parallel_resync;
+
         int                             ok_start_degraded;
         /* recovery/resync flags 
          * NEEDED:   we might need to start a resync/recover