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, 13 insertions, 1 deletions

diff --git a/drivers/md/faulty.c b/drivers/md/faulty.c
index 18793c137278..d76c87f2a831 100644
--- a/drivers/md/faulty.c
+++ b/drivers/md/faulty.c
@@ -283,6 +283,17 @@ static int reconfig(mddev_t *mddev, int layout, int chunk_size)
         return 0;
 }
 
+static sector_t faulty_size(mddev_t *mddev, sector_t sectors, int raid_disks)
+{
+        WARN_ONCE(raid_disks,
+                  "%s does not support generic reshape\n", __func__);
+
+        if (sectors == 0)
+                return mddev->dev_sectors;
+
+        return sectors;
+}
+
 static int run(mddev_t *mddev)
 {
         mdk_rdev_t *rdev;
@@ -301,7 +312,7 @@ static int run(mddev_t *mddev)
         list_for_each_entry(rdev, &mddev->disks, same_set)
                 conf->rdev = rdev;
 
-        mddev->array_sectors = mddev->dev_sectors;
+        mddev->array_sectors = faulty_size(mddev, 0, 0);
         mddev->private = conf;
 
         reconfig(mddev, mddev->layout, -1);
@@ -328,6 +339,7 @@ static struct mdk_personality faulty_personality =
         .stop           = stop,
         .status         = status,
         .reconfig       = reconfig,
+        .size           = faulty_size,
 };
 
 static int __init raid_init(void)