ext4_mb_discard_lg_preallocations(struct super_block *sb,
					struct ext4_locality_group *lg,
					int order, int total_entries)
{
	ext4_group_t group = 0;
	struct ext4_buddy e4b;
	struct list_head discard_list;
	struct ext4_prealloc_space *pa, *tmp;

	mb_debug(sb, "discard locality group preallocation\n");

	INIT_LIST_HEAD(&discard_list);

	spin_lock(&lg->lg_prealloc_lock);
	list_for_each_entry_rcu(pa, &lg->lg_prealloc_list[order],
				pa_inode_list,
				lockdep_is_held(&lg->lg_prealloc_lock)) {
		spin_lock(&pa->pa_lock);
		if (atomic_read(&pa->pa_count)) {
			/*
			 * This is the pa that we just used
			 * for block allocation. So don't
			 * free that
			 */
			spin_unlock(&pa->pa_lock);
			continue;
		}
		if (pa->pa_deleted) {
			spin_unlock(&pa->pa_lock);
			continue;
		}
		/* only lg prealloc space */
		BUG_ON(pa->pa_type != MB_GROUP_PA);

		/* seems this one can be freed ... */
		pa->pa_deleted = 1;
		spin_unlock(&pa->pa_lock);

		list_del_rcu(&pa->pa_inode_list);
		list_add(&pa->u.pa_tmp_list, &discard_list);

		total_entries--;
		if (total_entries <= 5) {
			/*
			 * we want to keep only 5 entries
			 * allowing it to grow to 8. This
			 * mak sure we don't call discard
			 * soon for this list.
			 */
			break;
		}
	}
	spin_unlock(&lg->lg_prealloc_lock);

	list_for_each_entry_safe(pa, tmp, &discard_list, u.pa_tmp_list) {
		int err;

		group = ext4_get_group_number(sb, pa->pa_pstart);
		err = ext4_mb_load_buddy_gfp(sb, group, &e4b,
					     GFP_NOFS|__GFP_NOFAIL);
		if (err) {
			ext4_error_err(sb, -err, "Error %d loading buddy information for %u",
				       err, group);
			continue;
		}
		ext4_lock_group(sb, group);
		list_del(&pa->pa_group_list);
		ext4_mb_release_group_pa(&e4b, pa);
		ext4_unlock_group(sb, group);

		ext4_mb_unload_buddy(&e4b);
		list_del(&pa->u.pa_tmp_list);
		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
	}
}
ext4_mb_discard_lg_preallocations(struct super_block *sb,
					struct ext4_locality_group *lg,
					int order, int total_entries)
{
	ext4_group_t group = 0;
	struct ext4_buddy e4b;
	struct list_head discard_list;
	struct ext4_prealloc_space *pa, *tmp;

	mb_debug(sb, "discard locality group preallocation\n");

	INIT_LIST_HEAD(&discard_list);

	spin_lock(&lg->lg_prealloc_lock);
	list_for_each_entry_rcu(pa, &lg->lg_prealloc_list[order],
				pa_inode_list,
				lockdep_is_held(&lg->lg_prealloc_lock)) {
		spin_lock(&pa->pa_lock);
		if (atomic_read(&pa->pa_count)) {
			 
			spin_unlock(&pa->pa_lock);
			continue;
		}
		if (pa->pa_deleted) {
			spin_unlock(&pa->pa_lock);
			continue;
		}
		 
		BUG_ON(pa->pa_type != MB_GROUP_PA);

		 
		pa->pa_deleted = 1;
		spin_unlock(&pa->pa_lock);

		list_del_rcu(&pa->pa_inode_list);
		list_add(&pa->u.pa_tmp_list, &discard_list);

		total_entries--;
		if (total_entries <= 5) {
			 
			break;
		}
	}
	spin_unlock(&lg->lg_prealloc_lock);

	list_for_each_entry_safe(pa, tmp, &discard_list, u.pa_tmp_list) {
		int err;

		group = ext4_get_group_number(sb, pa->pa_pstart);
		err = ext4_mb_load_buddy_gfp(sb, group, &e4b,
					     GFP_NOFS|__GFP_NOFAIL);
		if (err) {
			ext4_error_err(sb, -err, "Error %d loading buddy information for %u",
				       err, group);
			continue;
		}
		ext4_lock_group(sb, group);
		list_del(&pa->pa_group_list);
		ext4_mb_release_group_pa(&e4b, pa);
		ext4_unlock_group(sb, group);

		ext4_mb_unload_buddy(&e4b);
		list_del(&pa->u.pa_tmp_list);
		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
	}
}