#include <linux/cred.h>
  #include <linux/init.h>

  #include <linux/kernel.h>
  #include <linux/quotaops.h>
  #include <linux/sched.h>

  #include <linux/slab.h>

  #include <net/netlink.h>
  #include <net/genetlink.h>

  static const struct genl_multicast_group quota_mcgrps[] = {
  	{ .name = "events", },
  };

  /* Netlink family structure for quota */
  static struct genl_family quota_genl_family = {

  	/*
  	 * Needed due to multicast group ID abuse - old code assumed
  	 * the family ID was also a valid multicast group ID (which
  	 * isn't true) and userspace might thus rely on it. Assign a
  	 * static ID for this group to make dealing with that easier.
  	 */
  	.id = GENL_ID_VFS_DQUOT,

  	.hdrsize = 0,
  	.name = "VFS_DQUOT",
  	.version = 1,
  	.maxattr = QUOTA_NL_A_MAX,

  	.mcgrps = quota_mcgrps,
  	.n_mcgrps = ARRAY_SIZE(quota_mcgrps),

  };

  /**
   * quota_send_warning - Send warning to userspace about exceeded quota

   * @qid: The kernel internal quota identifier.

   * @dev: The device on which the fs is mounted (sb->s_dev)
   * @warntype: The type of the warning: QUOTA_NL_...
   *
   * This can be used by filesystems (including those which don't use
   * dquot) to send a message to userspace relating to quota limits.
   *
   */

  void quota_send_warning(struct kqid qid, dev_t dev,

  			const char warntype)
  {
  	static atomic_t seq;
  	struct sk_buff *skb;
  	void *msg_head;
  	int ret;
  	int msg_size = 4 * nla_total_size(sizeof(u32)) +

  		       2 * nla_total_size_64bit(sizeof(u64));

  
  	/* We have to allocate using GFP_NOFS as we are called from a
  	 * filesystem performing write and thus further recursion into
  	 * the fs to free some data could cause deadlocks. */
  	skb = genlmsg_new(msg_size, GFP_NOFS);
  	if (!skb) {
  		printk(KERN_ERR
  		  "VFS: Not enough memory to send quota warning.
  ");
  		return;
  	}
  	msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
  			&quota_genl_family, 0, QUOTA_NL_C_WARNING);
  	if (!msg_head) {
  		printk(KERN_ERR
  		  "VFS: Cannot store netlink header in quota warning.
  ");
  		goto err_out;
  	}

  	ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);

  	if (ret)
  		goto attr_err_out;

  	ret = nla_put_u64_64bit(skb, QUOTA_NL_A_EXCESS_ID,
  				from_kqid_munged(&init_user_ns, qid),
  				QUOTA_NL_A_PAD);

  	if (ret)
  		goto attr_err_out;
  	ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
  	if (ret)
  		goto attr_err_out;
  	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
  	if (ret)
  		goto attr_err_out;
  	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
  	if (ret)
  		goto attr_err_out;

  	ret = nla_put_u64_64bit(skb, QUOTA_NL_A_CAUSED_ID,
  				from_kuid_munged(&init_user_ns, current_uid()),
  				QUOTA_NL_A_PAD);

  	if (ret)
  		goto attr_err_out;
  	genlmsg_end(skb, msg_head);

  	genlmsg_multicast(&quota_genl_family, skb, 0, 0, GFP_NOFS);

  	return;
  attr_err_out:
  	printk(KERN_ERR "VFS: Not enough space to compose quota message!
  ");
  err_out:
  	kfree_skb(skb);
  }
  EXPORT_SYMBOL(quota_send_warning);
  
  static int __init quota_init(void)
  {
  	if (genl_register_family(&quota_genl_family) != 0)
  		printk(KERN_ERR
  		       "VFS: Failed to create quota netlink interface.
  ");
  	return 0;
  };

  fs_initcall(quota_init);