btrfs: use list_for_each_entry_safe in free_reloc_roots

The function always works on a local copy of the reloc root list, which
cannot be modified outside of it so using list_for_each_entry is fine.
Additionally the macro handles empty lists so drop list_empty checks of
callers. No semantic changes.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

@@ -1884,13 +1884,10 @@ int prepare_to_merge(struct reloc_control *rc, int err)
 static noinline_for_stack
 void free_reloc_roots(struct list_head *list)
 {
-	struct btrfs_root *reloc_root;
+	struct btrfs_root *reloc_root, *tmp;
 
-	while (!list_empty(list)) {
-		reloc_root = list_entry(list->next, struct btrfs_root,
-					root_list);
+	list_for_each_entry_safe(reloc_root, tmp, list, root_list)
 		__del_reloc_root(reloc_root);
-	}
 }
 
 static noinline_for_stack
@@ -1949,14 +1946,12 @@ void merge_reloc_roots(struct reloc_control *rc)
 out:
 	if (ret) {
 		btrfs_handle_fs_error(fs_info, ret, NULL);
-		if (!list_empty(&reloc_roots))
 		free_reloc_roots(&reloc_roots);
 
 		/* new reloc root may be added */
 		mutex_lock(&fs_info->reloc_mutex);
 		list_splice_init(&rc->reloc_roots, &reloc_roots);
 		mutex_unlock(&fs_info->reloc_mutex);
-		if (!list_empty(&reloc_roots))
 		free_reloc_roots(&reloc_roots);
 	}
 
@@ -3869,7 +3864,6 @@ int btrfs_recover_relocation(struct btrfs_root *root)
 	unset_reloc_control(rc);
 	free_reloc_control(rc);
 out:
-	if (!list_empty(&reloc_roots))
 	free_reloc_roots(&reloc_roots);
 
 	btrfs_free_path(path);