1 files changed, 51 insertions, 23 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 32a4e2311e43..86e9f2efae5c 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1843,7 +1843,27 @@ raid_disks_show(mddev_t *mddev, char *page)
         return sprintf(page, "%d\n", mddev->raid_disks);
 }
 
-static struct md_sysfs_entry md_raid_disks = __ATTR_RO(raid_disks);
+static int update_raid_disks(mddev_t *mddev, int raid_disks);
+
+static ssize_t
+raid_disks_store(mddev_t *mddev, const char *buf, size_t len)
+{
+        /* can only set raid_disks if array is not yet active */
+        char *e;
+        int rv = 0;
+        unsigned long n = simple_strtoul(buf, &e, 10);
+
+        if (!*buf || (*e && *e != '\n'))
+                return -EINVAL;
+
+        if (mddev->pers)
+                rv = update_raid_disks(mddev, n);
+        else
+                mddev->raid_disks = n;
+        return rv ? rv : len;
+}
+static struct md_sysfs_entry md_raid_disks =
+__ATTR(raid_disks, 0644, raid_disks_show, raid_disks_store);
 
 static ssize_t
 chunk_size_show(mddev_t *mddev, char *page)
@@ -3201,6 +3221,33 @@ static int update_size(mddev_t *mddev, unsigned long size)
         return rv;
 }
 
+static int update_raid_disks(mddev_t *mddev, int raid_disks)
+{
+        int rv;
+        /* change the number of raid disks */
+        if (mddev->pers->reshape == NULL)
+                return -EINVAL;
+        if (raid_disks <= 0 ||
+            raid_disks >= mddev->max_disks)
+                return -EINVAL;
+        if (mddev->sync_thread)
+                return -EBUSY;
+        rv = mddev->pers->reshape(mddev, raid_disks);
+        if (!rv) {
+                struct block_device *bdev;
+
+                bdev = bdget_disk(mddev->gendisk, 0);
+                if (bdev) {
+                        down(&bdev->bd_inode->i_sem);
+                        i_size_write(bdev->bd_inode, mddev->array_size << 10);
+                        up(&bdev->bd_inode->i_sem);
+                        bdput(bdev);
+                }
+        }
+        return rv;
+}
+
+
 /*
  * update_array_info is used to change the configuration of an
  * on-line array.
@@ -3252,28 +3299,9 @@ static int update_array_info(mddev_t *mddev, mdu_array_info_t *info)
         if (mddev->size != info->size)
                 rv = update_size(mddev, info->size);
 
-        if (mddev->raid_disks    != info->raid_disks) {
-                /* change the number of raid disks */
-                if (mddev->pers->reshape == NULL)
-                        return -EINVAL;
-                if (info->raid_disks <= 0 ||
-                    info->raid_disks >= mddev->max_disks)
-                        return -EINVAL;
-                if (mddev->sync_thread)
-                        return -EBUSY;
-                rv = mddev->pers->reshape(mddev, info->raid_disks);
-                if (!rv) {
-                        struct block_device *bdev;
-
-                        bdev = bdget_disk(mddev->gendisk, 0);
-                        if (bdev) {
-                                down(&bdev->bd_inode->i_sem);
-                                i_size_write(bdev->bd_inode, mddev->array_size << 10);
-                                up(&bdev->bd_inode->i_sem);
-                                bdput(bdev);
-                        }
-                }
-        }
+        if (mddev->raid_disks    != info->raid_disks)
+                rv = update_raid_disks(mddev, info->raid_disks);
+
         if ((state ^ info->state) & (1<<MD_SB_BITMAP_PRESENT)) {
                 if (mddev->pers->quiesce == NULL)
                         return -EINVAL;