2 files changed, 32 insertions, 0 deletions

diff --git a/Documentation/md.txt b/Documentation/md.txt
index 4cf5972821a9..80f158745ca5 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -200,6 +200,11 @@ All md devices contain:
      This can be written only while the array is being assembled, not
      after it is started.
 
+  layout
+     The "layout" for the array for the particular level.  This is
+     simply a number that is interpretted differently by different
+     levels.  It can be written while assembling an array.
+
    new_dev
      This file can be written but not read.  The value written should
      be a block device number as major:minor.  e.g. 8:0
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4b74c77213c3..e3261c438a65 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2155,6 +2155,32 @@ level_store(mddev_t *mddev, const char *buf, size_t len)
 static struct md_sysfs_entry md_level =
 __ATTR(level, 0644, level_show, level_store);
 
+
+static ssize_t
+layout_show(mddev_t *mddev, char *page)
+{
+        /* just a number, not meaningful for all levels */
+        return sprintf(page, "%d\n", mddev->layout);
+}
+
+static ssize_t
+layout_store(mddev_t *mddev, const char *buf, size_t len)
+{
+        char *e;
+        unsigned long n = simple_strtoul(buf, &e, 10);
+        if (mddev->pers)
+                return -EBUSY;
+
+        if (!*buf || (*e && *e != '\n'))
+                return -EINVAL;
+
+        mddev->layout = n;
+        return len;
+}
+static struct md_sysfs_entry md_layout =
+__ATTR(layout, 0655, layout_show, layout_store);
+
+
 static ssize_t
 raid_disks_show(mddev_t *mddev, char *page)
 {
@@ -2741,6 +2767,7 @@ __ATTR(suspend_hi, S_IRUGO|S_IWUSR, suspend_hi_show, suspend_hi_store);
 
 static struct attribute *md_default_attrs[] = {
         &md_level.attr,
+        &md_layout.attr,
         &md_raid_disks.attr,
         &md_chunk_size.attr,
         &md_size.attr,