[PATCH] md: Support suspending of IO to regions of an md array

This allows user-space to access data safely.  This is needed for raid5
reshape as user-space needs to take a backup of the first few stripes before
allowing reshape to commence.

It will also be useful in cluster-aware raid1 configurations so that all
cluster members can leave a section of the array untouched while a
resync/recovery happens.

A 'start' and 'end' of the suspended range are written to 2 sysfs attributes.
Note that only one range can be suspended at a time.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 002ee631fabb..c0d3097846a7 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -151,6 +151,10 @@ struct mddev_s
         sector_t                        resync_mismatches; /* count of sectors where
                                                             * parity/replica mismatch found
                                                             */
+
+        /* allow user-space to request suspension of IO to regions of the array */
+        sector_t                        suspend_lo;
+        sector_t                        suspend_hi;
         /* if zero, use the system-wide default */
         int                             sync_speed_min;
         int                             sync_speed_max;