Btrfs: add btrfs_scratch_superblock() function

This new function is used by the device replace procedure in
a later patch.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 96bb2e4446aa..6cd8a32c4484 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5106,3 +5106,21 @@ int btrfs_get_dev_stats(struct btrfs_root *root,
                 stats->nr_items = BTRFS_DEV_STAT_VALUES_MAX;
         return 0;
 }
+
+int btrfs_scratch_superblock(struct btrfs_device *device)
+{
+        struct buffer_head *bh;
+        struct btrfs_super_block *disk_super;
+
+        bh = btrfs_read_dev_super(device->bdev);
+        if (!bh)
+                return -EINVAL;
+        disk_super = (struct btrfs_super_block *)bh->b_data;
+
+        memset(&disk_super->magic, 0, sizeof(disk_super->magic));
+        set_buffer_dirty(bh);
+        sync_dirty_buffer(bh);
+        brelse(bh);
+
+        return 0;
+}