md/raid5: allow layout/chunksize to be changed on an active 2-drive raid5.

2-drive raid5's aren't very interesting.  But if you are converting
a raid1 into a raid5, you will at least temporarily have one.  And
that it a good time to set the layout/chunksize for the new RAID5
if you aren't happy with the defaults.

layout and chunksize don't actually affect the placement of data
on a 2-drive raid5, so we just do some internal book-keeping.

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

1 files changed, 24 insertions, 13 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 05b613b5e4b2..0689d89d263c 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2771,12 +2771,18 @@ layout_store(mddev_t *mddev, const char *buf, size_t len)
         if (!*buf || (*e && *e != '\n'))
                 return -EINVAL;
 
-        if (mddev->pers)
-                return -EBUSY;
-
-        mddev->new_layout = n;
-        if (mddev->reshape_position == MaxSector)
-                mddev->layout = n;
+        if (mddev->pers) {
+                int err;
+                if (mddev->pers->reconfig == NULL)
+                        return -EBUSY;
+                err = mddev->pers->reconfig(mddev, n, -1);
+                if (err)
+                        return err;
+        } else {
+                mddev->new_layout = n;
+                if (mddev->reshape_position == MaxSector)
+                        mddev->layout = n;
+        }
         return len;
 }
 static struct md_sysfs_entry md_layout =
@@ -2833,19 +2839,24 @@ chunk_size_show(mddev_t *mddev, char *page)
 static ssize_t
 chunk_size_store(mddev_t *mddev, const char *buf, size_t len)
 {
-        /* can only set chunk_size if array is not yet active */
         char *e;
         unsigned long n = simple_strtoul(buf, &e, 10);
 
         if (!*buf || (*e && *e != '\n'))
                 return -EINVAL;
 
-        if (mddev->pers)
-                return -EBUSY;
-
-        mddev->new_chunk = n;
-        if (mddev->reshape_position == MaxSector)
-                mddev->chunk_size = n;
+        if (mddev->pers) {
+                int err;
+                if (mddev->pers->reconfig == NULL)
+                        return -EBUSY;
+                err = mddev->pers->reconfig(mddev, -1, n);
+                if (err)
+                        return err;
+        } else {
+                mddev->new_chunk = n;
+                if (mddev->reshape_position == MaxSector)
+                        mddev->chunk_size = n;
+        }
         return len;
 }
 static struct md_sysfs_entry md_chunk_size =