md: add 'size' as a personality method

In preparation for giving userspace control over ->array_sectors we need
to be able to retrieve the 'default' size, and the 'anticipated' size
when a reshape is requested.  For personalities that do not reshape emit
a warning if anything but the default size is requested.

In the raid5 case we need to update ->previous_raid_disks to make the
new 'default' size available.

Reviewed-by: Andre Noll <maan@systemlinux.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index 87accf74e4b4..a3f6d8668bb3 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -406,6 +406,14 @@ static void multipathd (mddev_t *mddev)
         spin_unlock_irqrestore(&conf->device_lock, flags);
 }
 
+static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
+{
+        WARN_ONCE(sectors || raid_disks,
+                  "%s does not support generic reshape\n", __func__);
+
+        return mddev->dev_sectors;
+}
+
 static int multipath_run (mddev_t *mddev)
 {
         multipath_conf_t *conf;
@@ -502,7 +510,7 @@ static int multipath_run (mddev_t *mddev)
         /*
          * Ok, everything is just fine now
          */
-        mddev->array_sectors = mddev->dev_sectors;
+        mddev->array_sectors = multipath_size(mddev, 0, 0);
 
         mddev->queue->unplug_fn = multipath_unplug;
         mddev->queue->backing_dev_info.congested_fn = multipath_congested;
@@ -547,6 +555,7 @@ static struct mdk_personality multipath_personality =
         .error_handler  = multipath_error,
         .hot_add_disk   = multipath_add_disk,
         .hot_remove_disk= multipath_remove_disk,
+        .size           = multipath_size,
 };
 
 static int __init multipath_init (void)