fs/quota/netlink.c

   1
   2 #include <linux/cred.h>
   3 #include <linux/init.h>
   4 #include <linux/module.h>
   5 #include <linux/kernel.h>
   6 #include <linux/quotaops.h>
   7 #include <linux/sched.h>
   8 #include <linux/slab.h>
   9 #include <net/netlink.h>
  10 #include <net/genetlink.h>
  11
  12 /* Netlink family structure for quota */
  13 static struct genl_family quota_genl_family = {
  14         .id = GENL_ID_GENERATE,
  15         .hdrsize = 0,
  16         .name = "VFS_DQUOT",
  17         .version = 1,
  18         .maxattr = QUOTA_NL_A_MAX,
  19 };
  20
  21 /**
  22  * quota_send_warning - Send warning to userspace about exceeded quota
  23  * @type: The quota type: USRQQUOTA, GRPQUOTA,...
  24  * @id: The user or group id of the quota that was exceeded
  25  * @dev: The device on which the fs is mounted (sb->s_dev)
  26  * @warntype: The type of the warning: QUOTA_NL_...
  27  *
  28  * This can be used by filesystems (including those which don't use
  29  * dquot) to send a message to userspace relating to quota limits.
  30  *
  31  */
  32
  33 void quota_send_warning(short type, unsigned int id, dev_t dev,
  34                         const char warntype)
  35 {
  36         static atomic_t seq;
  37         struct sk_buff *skb;
  38         void *msg_head;
  39         int ret;
  40         int msg_size = 4 * nla_total_size(sizeof(u32)) +
  41                        2 * nla_total_size(sizeof(u64));
  42
  43         /* We have to allocate using GFP_NOFS as we are called from a
  44          * filesystem performing write and thus further recursion into
  45          * the fs to free some data could cause deadlocks. */
  46         skb = genlmsg_new(msg_size, GFP_NOFS);
  47         if (!skb) {
  48                 printk(KERN_ERR
  49                   "VFS: Not enough memory to send quota warning.\n");
  50                 return;
  51         }
  52         msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
  53                         &quota_genl_family, 0, QUOTA_NL_C_WARNING);
  54         if (!msg_head) {
  55                 printk(KERN_ERR
  56                   "VFS: Cannot store netlink header in quota warning.\n");
  57                 goto err_out;
  58         }
  59         ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, type);
  60         if (ret)
  61                 goto attr_err_out;
  62         ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID, id);
  63         if (ret)
  64                 goto attr_err_out;
  65         ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
  66         if (ret)
  67                 goto attr_err_out;
  68         ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
  69         if (ret)
  70                 goto attr_err_out;
  71         ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
  72         if (ret)
  73                 goto attr_err_out;
  74         ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID, current_uid());
  75         if (ret)
  76                 goto attr_err_out;
  77         genlmsg_end(skb, msg_head);
  78
  79         genlmsg_multicast(skb, 0, quota_genl_family.id, GFP_NOFS);
  80         return;
  81 attr_err_out:
  82         printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
  83 err_out:
  84         kfree_skb(skb);
  85 }
  86 EXPORT_SYMBOL(quota_send_warning);
  87
  88 static int __init quota_init(void)
  89 {
  90         if (genl_register_family(&quota_genl_family) != 0)
  91                 printk(KERN_ERR
  92                        "VFS: Failed to create quota netlink interface.\n");
  93         return 0;
  94 };
  95
  96 module_init(quota_init);