md/raid10: set dev_sectors properly when resizing devices in array.

raid10 stores dev_sectors in 'conf' separately from the one in
'mddev' because it can have a very significant effect on block
addressing and so need to be updated carefully.

However raid10_resize isn't updating it at all!

To update it correctly, we need to make sure it is a proper
multiple of the chunksize taking various details of the layout
in to account.
This calculation is currently done in setup_conf.   So split it
out from there and call it from raid10_resize as well.
Then set conf->dev_sectors properly.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 32 insertions, 24 deletions

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index c8dbb84d5357..3e7b1548111a 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3164,12 +3164,40 @@ raid10_size(struct mddev *mddev, sector_t sectors, int raid_disks)
         return size << conf->chunk_shift;
 }
 
+static void calc_sectors(struct r10conf *conf, sector_t size)
+{
+        /* Calculate the number of sectors-per-device that will
+         * actually be used, and set conf->dev_sectors and
+         * conf->stride
+         */
+
+        size = size >> conf->chunk_shift;
+        sector_div(size, conf->far_copies);
+        size = size * conf->raid_disks;
+        sector_div(size, conf->near_copies);
+        /* 'size' is now the number of chunks in the array */
+        /* calculate "used chunks per device" */
+        size = size * conf->copies;
+
+        /* We need to round up when dividing by raid_disks to
+         * get the stride size.
+         */
+        size = DIV_ROUND_UP_SECTOR_T(size, conf->raid_disks);
+
+        conf->dev_sectors = size << conf->chunk_shift;
+
+        if (conf->far_offset)
+                conf->stride = 1 << conf->chunk_shift;
+        else {
+                sector_div(size, conf->near_copies);
+                conf->stride = size << conf->chunk_shift;
+        }
+}
 
 static struct r10conf *setup_conf(struct mddev *mddev)
 {
         struct r10conf *conf = NULL;
         int nc, fc, fo;
-        sector_t stride, size;
         int err = -EINVAL;
 
         if (mddev->new_chunk_sectors < (PAGE_SIZE >> 9) ||
@@ -3219,28 +3247,7 @@ static struct r10conf *setup_conf(struct mddev *mddev)
         if (!conf->r10bio_pool)
                 goto out;
 
-        size = mddev->dev_sectors >> conf->chunk_shift;
-        sector_div(size, fc);
-        size = size * conf->raid_disks;
-        sector_div(size, nc);
-        /* 'size' is now the number of chunks in the array */
-        /* calculate "used chunks per device" in 'stride' */
-        stride = size * conf->copies;
-
-        /* We need to round up when dividing by raid_disks to
-         * get the stride size.
-         */
-        stride += conf->raid_disks - 1;
-        sector_div(stride, conf->raid_disks);
-
-        conf->dev_sectors = stride << conf->chunk_shift;
-
-        if (fo)
-                stride = 1;
-        else
-                sector_div(stride, fc);
-        conf->stride = stride << conf->chunk_shift;
-
+        calc_sectors(conf, mddev->dev_sectors);
 
         spin_lock_init(&conf->device_lock);
         INIT_LIST_HEAD(&conf->retry_list);
@@ -3468,7 +3475,8 @@ static int raid10_resize(struct mddev *mddev, sector_t sectors)
                 mddev->recovery_cp = oldsize;
                 set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
         }
-        mddev->dev_sectors = sectors;
+        calc_sectors(conf, sectors);
+        mddev->dev_sectors = conf->dev_sectors;
         mddev->resync_max_sectors = size;
         return 0;
 }