btrfs: use GFP_KERNEL in btrfs_calc_avail_data_space

We don't hold any locks here. Inidirectly called from statfs.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 3371213..53d43cd 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1926,7 +1926,7 @@
 	}
 
 	devices_info = kmalloc_array(nr_devices, sizeof(*devices_info),
-			       GFP_NOFS);
+			       GFP_KERNEL);
 	if (!devices_info)
 		return -ENOMEM;