1 files changed, 51 insertions, 23 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 32a4e2311e4..86e9f2efae5 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;