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, 25 insertions, 10 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 70b50af2bcd7..2cd619ff0761 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4166,6 +4166,20 @@ static struct attribute_group raid5_attrs_group = {
         .attrs = raid5_attrs,
 };
 
+static sector_t
+raid5_size(mddev_t *mddev, sector_t sectors, int raid_disks)
+{
+        raid5_conf_t *conf = mddev_to_conf(mddev);
+
+        if (!sectors)
+                sectors = mddev->dev_sectors;
+        if (!raid_disks)
+                raid_disks = conf->previous_raid_disks;
+
+        sectors &= ~((sector_t)mddev->chunk_size/512 - 1);
+        return sectors * (raid_disks - conf->max_degraded);
+}
+
 static raid5_conf_t *setup_conf(mddev_t *mddev)
 {
         raid5_conf_t *conf;
@@ -4460,8 +4474,7 @@ static int run(mddev_t *mddev)
         mddev->queue->backing_dev_info.congested_data = mddev;
         mddev->queue->backing_dev_info.congested_fn = raid5_congested;
 
-        mddev->array_sectors = mddev->dev_sectors *
-                (conf->previous_raid_disks - conf->max_degraded);
+        mddev->array_sectors = raid5_size(mddev, 0, 0);
 
         blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);
 
@@ -4684,11 +4697,8 @@ static int raid5_resize(mddev_t *mddev, sector_t sectors)
          * any io in the removed space completes, but it hardly seems
          * worth it.
          */
-        raid5_conf_t *conf = mddev_to_conf(mddev);
-
         sectors &= ~((sector_t)mddev->chunk_size/512 - 1);
-        mddev->array_sectors = sectors * (mddev->raid_disks
-                                          - conf->max_degraded);
+        mddev->array_sectors = raid5_size(mddev, sectors, mddev->raid_disks);
         set_capacity(mddev->gendisk, mddev->array_sectors);
         mddev->changed = 1;
         if (sectors > mddev->dev_sectors && mddev->recovery_cp == MaxSector) {
@@ -4824,10 +4834,12 @@ static void end_reshape(raid5_conf_t *conf)
         struct block_device *bdev;
 
         if (!test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery)) {
-                conf->mddev->array_sectors = conf->mddev->dev_sectors *
-                        (conf->raid_disks - conf->max_degraded);
-                set_capacity(conf->mddev->gendisk, conf->mddev->array_sectors);
-                conf->mddev->changed = 1;
+                mddev_t *mddev = conf->mddev;
+
+                mddev->array_sectors = raid5_size(mddev, 0, conf->raid_disks);
+                set_capacity(mddev->gendisk, mddev->array_sectors);
+                mddev->changed = 1;
+                conf->previous_raid_disks = conf->raid_disks;
 
                 bdev = bdget_disk(conf->mddev->gendisk, 0);
                 if (bdev) {
@@ -5076,6 +5088,7 @@ static struct mdk_personality raid6_personality =
         .spare_active   = raid5_spare_active,
         .sync_request   = sync_request,
         .resize         = raid5_resize,
+        .size           = raid5_size,
 #ifdef CONFIG_MD_RAID5_RESHAPE
         .check_reshape  = raid5_check_reshape,
         .start_reshape  = raid5_start_reshape,
@@ -5098,6 +5111,7 @@ static struct mdk_personality raid5_personality =
         .spare_active   = raid5_spare_active,
         .sync_request   = sync_request,
         .resize         = raid5_resize,
+        .size           = raid5_size,
 #ifdef CONFIG_MD_RAID5_RESHAPE
         .check_reshape  = raid5_check_reshape,
         .start_reshape  = raid5_start_reshape,
@@ -5122,6 +5136,7 @@ static struct mdk_personality raid4_personality =
         .spare_active   = raid5_spare_active,
         .sync_request   = sync_request,
         .resize         = raid5_resize,
+        .size           = raid5_size,
 #ifdef CONFIG_MD_RAID5_RESHAPE
         .check_reshape  = raid5_check_reshape,
         .start_reshape  = raid5_start_reshape,