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 static const struct genl_multicast_group quota_mcgrps[] = {
  13         { .name = "events", },
  14 };
  15
  16 /* Netlink family structure for quota */
  17 static struct genl_family quota_genl_family = {
  18         /*
  19          * Needed due to multicast group ID abuse - old code assumed
  20          * the family ID was also a valid multicast group ID (which
  21          * isn't true) and userspace might thus rely on it. Assign a
  22          * static ID for this group to make dealing with that easier.
  23          */
  24         .id = GENL_ID_VFS_DQUOT,
  25         .hdrsize = 0,
  26         .name = "VFS_DQUOT",
  27         .version = 1,
  28         .maxattr = QUOTA_NL_A_MAX,
  29         .mcgrps = quota_mcgrps,
  30         .n_mcgrps = ARRAY_SIZE(quota_mcgrps),
  31 };
  32
  33 /**
  34  * quota_send_warning - Send warning to userspace about exceeded quota
  35  * @qid: The kernel internal quota identifier.
  36  * @dev: The device on which the fs is mounted (sb->s_dev)
  37  * @warntype: The type of the warning: QUOTA_NL_...
  38  *
  39  * This can be used by filesystems (including those which don't use
  40  * dquot) to send a message to userspace relating to quota limits.
  41  *
  42  */
  43
  44 void quota_send_warning(struct kqid qid, dev_t dev,
  45                         const char warntype)
  46 {
  47         static atomic_t seq;
  48         struct sk_buff *skb;
  49         void *msg_head;
  50         int ret;
  51         int msg_size = 4 * nla_total_size(sizeof(u32)) +
  52                        2 * nla_total_size(sizeof(u64));
  53
  54         /* We have to allocate using GFP_NOFS as we are called from a
  55          * filesystem performing write and thus further recursion into
  56          * the fs to free some data could cause deadlocks. */
  57         skb = genlmsg_new(msg_size, GFP_NOFS);
  58         if (!skb) {
  59                 printk(KERN_ERR
  60                   "VFS: Not enough memory to send quota warning.\n");
  61                 return;
  62         }
  63         msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
  64                         &quota_genl_family, 0, QUOTA_NL_C_WARNING);
  65         if (!msg_head) {
  66                 printk(KERN_ERR
  67                   "VFS: Cannot store netlink header in quota warning.\n");
  68                 goto err_out;
  69         }
  70         ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
  71         if (ret)
  72                 goto attr_err_out;
  73         ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID,
  74                           from_kqid_munged(&init_user_ns, qid));
  75         if (ret)
  76                 goto attr_err_out;
  77         ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
  78         if (ret)
  79                 goto attr_err_out;
  80         ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
  81         if (ret)
  82                 goto attr_err_out;
  83         ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
  84         if (ret)
  85                 goto attr_err_out;
  86         ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID,
  87                           from_kuid_munged(&init_user_ns, current_uid()));
  88         if (ret)
  89                 goto attr_err_out;
  90         genlmsg_end(skb, msg_head);
  91
  92         genlmsg_multicast(&quota_genl_family, skb, 0, 0, GFP_NOFS);
  93         return;
  94 attr_err_out:
  95         printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
  96 err_out:
  97         kfree_skb(skb);
  98 }
  99 EXPORT_SYMBOL(quota_send_warning);
 100
 101 static int __init quota_init(void)
 102 {
 103         if (genl_register_family(&quota_genl_family) != 0)
 104                 printk(KERN_ERR
 105                        "VFS: Failed to create quota netlink interface.\n");
 106         return 0;
 107 };
 108
 109 module_init(quota_init);