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         /*
  15          * Needed due to multicast group ID abuse - old code assumed
  16          * the family ID was also a valid multicast group ID (which
  17          * isn't true) and userspace might thus rely on it. Assign a
  18          * static ID for this group to make dealing with that easier.
  19          */
  20         .id = GENL_ID_VFS_DQUOT,
  21         .hdrsize = 0,
  22         .name = "VFS_DQUOT",
  23         .version = 1,
  24         .maxattr = QUOTA_NL_A_MAX,
  25 };
  26
  27 static struct genl_multicast_group quota_mcgrp = {
  28         .name = "events",
  29 };
  30
  31 /**
  32  * quota_send_warning - Send warning to userspace about exceeded quota
  33  * @type: The quota type: USRQQUOTA, GRPQUOTA,...
  34  * @id: The user or group id of the quota that was exceeded
  35  * @dev: The device on which the fs is mounted (sb->s_dev)
  36  * @warntype: The type of the warning: QUOTA_NL_...
  37  *
  38  * This can be used by filesystems (including those which don't use
  39  * dquot) to send a message to userspace relating to quota limits.
  40  *
  41  */
  42
  43 void quota_send_warning(struct kqid qid, dev_t dev,
  44                         const char warntype)
  45 {
  46         static atomic_t seq;
  47         struct sk_buff *skb;
  48         void *msg_head;
  49         int ret;
  50         int msg_size = 4 * nla_total_size(sizeof(u32)) +
  51                        2 * nla_total_size(sizeof(u64));
  52
  53         /* We have to allocate using GFP_NOFS as we are called from a
  54          * filesystem performing write and thus further recursion into
  55          * the fs to free some data could cause deadlocks. */
  56         skb = genlmsg_new(msg_size, GFP_NOFS);
  57         if (!skb) {
  58                 printk(KERN_ERR
  59                   "VFS: Not enough memory to send quota warning.\n");
  60                 return;
  61         }
  62         msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
  63                         &quota_genl_family, 0, QUOTA_NL_C_WARNING);
  64         if (!msg_head) {
  65                 printk(KERN_ERR
  66                   "VFS: Cannot store netlink header in quota warning.\n");
  67                 goto err_out;
  68         }
  69         ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
  70         if (ret)
  71                 goto attr_err_out;
  72         ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID,
  73                           from_kqid_munged(&init_user_ns, qid));
  74         if (ret)
  75                 goto attr_err_out;
  76         ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
  77         if (ret)
  78                 goto attr_err_out;
  79         ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
  80         if (ret)
  81                 goto attr_err_out;
  82         ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
  83         if (ret)
  84                 goto attr_err_out;
  85         ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID,
  86                           from_kuid_munged(&init_user_ns, current_uid()));
  87         if (ret)
  88                 goto attr_err_out;
  89         genlmsg_end(skb, msg_head);
  90
  91         genlmsg_multicast(skb, 0, quota_mcgrp.id, GFP_NOFS);
  92         return;
  93 attr_err_out:
  94         printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
  95 err_out:
  96         kfree_skb(skb);
  97 }
  98 EXPORT_SYMBOL(quota_send_warning);
  99
 100 static int __init quota_init(void)
 101 {
 102         if (genl_register_family(&quota_genl_family) != 0)
 103                 printk(KERN_ERR
 104                        "VFS: Failed to create quota netlink interface.\n");
 105         if (genl_register_mc_group(&quota_genl_family, &quota_mcgrp))
 106                 printk(KERN_ERR
 107                        "VFS: Failed to register quota mcast group.\n");
 108         return 0;
 109 };
 110
 111 module_init(quota_init);