1 files changed, 26 insertions, 0 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 0ac712efcdf2..32fe8b33cc1c 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -913,6 +913,32 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
         return 0;
 }
 
+/* Used to sort the devices by max_avail(descending sort) */
+static int btrfs_cmp_device_free_bytes(const void *dev_info1,
+                                       const void *dev_info2)
+{
+        if (((struct btrfs_device_info *)dev_info1)->max_avail >
+            ((struct btrfs_device_info *)dev_info2)->max_avail)
+                return -1;
+        else if (((struct btrfs_device_info *)dev_info1)->max_avail <
+                 ((struct btrfs_device_info *)dev_info2)->max_avail)
+                return 1;
+        else
+        return 0;
+}
+
+/*
+ * sort the devices by max_avail, in which max free extent size of each device
+ * is stored.(Descending Sort)
+ */
+static inline void btrfs_descending_sort_devices(
+                                        struct btrfs_device_info *devices,
+                                        size_t nr_devices)
+{
+        sort(devices, nr_devices, sizeof(struct btrfs_device_info),
+             btrfs_cmp_device_free_bytes, NULL);
+}
+
 /*
  * The helper to calc the free space on the devices that can be used to store
  * file data.