fs/quota/netlink.c

   1 #include <linux/cred.h>
   2 #include <linux/init.h>
   3 #include <linux/kernel.h>
   4 #include <linux/quotaops.h>
   5 #include <linux/sched.h>
   6 #include <linux/slab.h>
   7 #include <net/netlink.h>
   8 #include <net/genetlink.h>
   9
  10 static const struct genl_multicast_group quota_mcgrps[] = {
  11         { .name = "events", },
  12 };
  13
  14 /* Netlink family structure for quota */
  15 static struct genl_family quota_genl_family = {
  16         /*
  17          * Needed due to multicast group ID abuse - old code assumed
  18          * the family ID was also a valid multicast group ID (which
  19          * isn't true) and userspace might thus rely on it. Assign a
  20          * static ID for this group to make dealing with that easier.
  21          */
  22         .id = GENL_ID_VFS_DQUOT,
  23         .hdrsize = 0,
  24         .name = "VFS_DQUOT",
  25         .version = 1,
  26         .maxattr = QUOTA_NL_A_MAX,
  27         .mcgrps = quota_mcgrps,
  28         .n_mcgrps = ARRAY_SIZE(quota_mcgrps),
  29 };
  30
  31 /**
  32  * quota_send_warning - Send warning to userspace about exceeded quota
  33  * @qid: The kernel internal quota identifier.
  34  * @dev: The device on which the fs is mounted (sb->s_dev)
  35  * @warntype: The type of the warning: QUOTA_NL_...
  36  *
  37  * This can be used by filesystems (including those which don't use
  38  * dquot) to send a message to userspace relating to quota limits.
  39  *
  40  */
  41
  42 void quota_send_warning(struct kqid qid, dev_t dev,
  43                         const char warntype)
  44 {
  45         static atomic_t seq;
  46         struct sk_buff *skb;
  47         void *msg_head;
  48         int ret;
  49         int msg_size = 4 * nla_total_size(sizeof(u32)) +
  50                        2 * nla_total_size(sizeof(u64));
  51
  52         /* We have to allocate using GFP_NOFS as we are called from a
  53          * filesystem performing write and thus further recursion into
  54          * the fs to free some data could cause deadlocks. */
  55         skb = genlmsg_new(msg_size, GFP_NOFS);
  56         if (!skb) {
  57                 printk(KERN_ERR
  58                   "VFS: Not enough memory to send quota warning.\n");
  59                 return;
  60         }
  61         msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
  62                         &quota_genl_family, 0, QUOTA_NL_C_WARNING);
  63         if (!msg_head) {
  64                 printk(KERN_ERR
  65                   "VFS: Cannot store netlink header in quota warning.\n");
  66                 goto err_out;
  67         }
  68         ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
  69         if (ret)
  70                 goto attr_err_out;
  71         ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID,
  72                           from_kqid_munged(&init_user_ns, qid));
  73         if (ret)
  74                 goto attr_err_out;
  75         ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
  76         if (ret)
  77                 goto attr_err_out;
  78         ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
  79         if (ret)
  80                 goto attr_err_out;
  81         ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
  82         if (ret)
  83                 goto attr_err_out;
  84         ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID,
  85                           from_kuid_munged(&init_user_ns, current_uid()));
  86         if (ret)
  87                 goto attr_err_out;
  88         genlmsg_end(skb, msg_head);
  89
  90         genlmsg_multicast(&quota_genl_family, skb, 0, 0, GFP_NOFS);
  91         return;
  92 attr_err_out:
  93         printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
  94 err_out:
  95         kfree_skb(skb);
  96 }
  97 EXPORT_SYMBOL(quota_send_warning);
  98
  99 static int __init quota_init(void)
 100 {
 101         if (genl_register_family(&quota_genl_family) != 0)
 102                 printk(KERN_ERR
 103                        "VFS: Failed to create quota netlink interface.\n");
 104         return 0;
 105 };
 106 fs_initcall(quota_init);