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, 22 insertions, 2 deletions

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index c2059e25d03f..5bf1b24ae802 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -2023,6 +2023,25 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
         goto skipped;
 }
 
+static sector_t
+raid10_size(mddev_t *mddev, sector_t sectors, int raid_disks)
+{
+        sector_t size;
+        conf_t *conf = mddev_to_conf(mddev);
+
+        if (!raid_disks)
+                raid_disks = mddev->raid_disks;
+        if (!sectors)
+                sectors = mddev->dev_sectors;
+
+        size = sectors >> conf->chunk_shift;
+        sector_div(size, conf->far_copies);
+        size = size * raid_disks;
+        sector_div(size, conf->near_copies);
+
+        return size << conf->chunk_shift;
+}
+
 static int run(mddev_t *mddev)
 {
         conf_t *conf;
@@ -2174,8 +2193,8 @@ static int run(mddev_t *mddev)
         /*
          * Ok, everything is just fine now
          */
-        mddev->array_sectors = size << conf->chunk_shift;
-        mddev->resync_max_sectors = size << conf->chunk_shift;
+        mddev->array_sectors = raid10_size(mddev, 0, 0);
+        mddev->resync_max_sectors = mddev->array_sectors;
 
         mddev->queue->unplug_fn = raid10_unplug;
         mddev->queue->backing_dev_info.congested_fn = raid10_congested;
@@ -2261,6 +2280,7 @@ static struct mdk_personality raid10_personality =
         .spare_active   = raid10_spare_active,
         .sync_request   = sync_request,
         .quiesce        = raid10_quiesce,
+        .size           = raid10_size,
 };
 
 static int __init raid_init(void)