Btrfs: don't skip writing out a empty block groups cache

I noticed a slight bug where we will not bother writing out the block group
cache's space cache if it's space tree is empty.  Since it could have a cluster
or pinned extents that need to be written out this is just not a valid test.
Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 0a8ccdbdd464..b81556ca75ea 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -575,10 +575,6 @@ int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
 
         INIT_LIST_HEAD(&bitmap_list);
 
-        node = rb_first(&ctl->free_space_offset);
-        if (!node)
-                return -1;
-
         if (!i_size_read(inode))
                 return -1;
 
@@ -639,6 +635,12 @@ int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
         if (block_group)
                 start = block_group->key.objectid;
 
+        node = rb_first(&ctl->free_space_offset);
+        if (!node && cluster) {
+                node = rb_first(&cluster->root);
+                cluster = NULL;
+        }
+
         /* Write out the extent entries */
         do {
                 struct btrfs_free_space_entry *entry;