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, 2 deletions

diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index d5d99290041a..b6bb976123da 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -101,6 +101,16 @@ static int linear_congested(void *data, int bits)
         return ret;
 }
 
+static sector_t linear_size(mddev_t *mddev, sector_t sectors, int raid_disks)
+{
+        linear_conf_t *conf = mddev_to_conf(mddev);
+
+        WARN_ONCE(sectors || raid_disks,
+                  "%s does not support generic reshape\n", __func__);
+
+        return conf->array_sectors;
+}
+
 static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
 {
         linear_conf_t *conf;
@@ -253,7 +263,7 @@ static int linear_run (mddev_t *mddev)
         if (!conf)
                 return 1;
         mddev->private = conf;
-        mddev->array_sectors = conf->array_sectors;
+        mddev->array_sectors = linear_size(mddev, 0, 0);
 
         blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
         mddev->queue->unplug_fn = linear_unplug;
@@ -287,7 +297,7 @@ static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
         newconf->prev = mddev_to_conf(mddev);
         mddev->private = newconf;
         mddev->raid_disks++;
-        mddev->array_sectors = newconf->array_sectors;
+        mddev->array_sectors = linear_size(mddev, 0, 0);
         set_capacity(mddev->gendisk, mddev->array_sectors);
         return 0;
 }
@@ -385,6 +395,7 @@ static struct mdk_personality linear_personality =
         .stop           = linear_stop,
         .status         = linear_status,
         .hot_add_disk   = linear_add,
+        .size           = linear_size,
 };
 
 static int __init linear_init (void)