LXR linux/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
  12static const struct genl_multicast_group quota_mcgrps[] = {
  13        { .name = "events", },
  14};
  15
  16/* Netlink family structure for quota */
  17static 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 * @type: The quota type: USRQQUOTA, GRPQUOTA,...
  36 * @id: The user or group id of the quota that was exceeded
  37 * @dev: The device on which the fs is mounted (sb->s_dev)
  38 * @warntype: The type of the warning: QUOTA_NL_...
  39 *
  40 * This can be used by filesystems (including those which don't use
  41 * dquot) to send a message to userspace relating to quota limits.
  42 *
  43 */
  44
  45void quota_send_warning(struct kqid qid, dev_t dev,
  46                        const char warntype)
  47{
  48        static atomic_t seq;
  49        struct sk_buff *skb;
  50        void *msg_head;
  51        int ret;
  52        int msg_size = 4 * nla_total_size(sizeof(u32)) +
  53                       2 * nla_total_size(sizeof(u64));
  54
  55        /* We have to allocate using GFP_NOFS as we are called from a
  56         * filesystem performing write and thus further recursion into
  57         * the fs to free some data could cause deadlocks. */
  58        skb = genlmsg_new(msg_size, GFP_NOFS);
  59        if (!skb) {
  60                printk(KERN_ERR
  61                  "VFS: Not enough memory to send quota warning.\n");
  62                return;
  63        }
  64        msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
  65                        &quota_genl_family, 0, QUOTA_NL_C_WARNING);
  66        if (!msg_head) {
  67                printk(KERN_ERR
  68                  "VFS: Cannot store netlink header in quota warning.\n");
  69                goto err_out;
  70        }
  71        ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
  72        if (ret)
  73                goto attr_err_out;
  74        ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID,
  75                          from_kqid_munged(&init_user_ns, qid));
  76        if (ret)
  77                goto attr_err_out;
  78        ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
  79        if (ret)
  80                goto attr_err_out;
  81        ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
  82        if (ret)
  83                goto attr_err_out;
  84        ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
  85        if (ret)
  86                goto attr_err_out;
  87        ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID,
  88                          from_kuid_munged(&init_user_ns, current_uid()));
  89        if (ret)
  90                goto attr_err_out;
  91        genlmsg_end(skb, msg_head);
  92
  93        genlmsg_multicast(&quota_genl_family, skb, 0, 0, GFP_NOFS);
  94        return;
  95attr_err_out:
  96        printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
  97err_out:
  98        kfree_skb(skb);
  99}
 100EXPORT_SYMBOL(quota_send_warning);
 101
 102static int __init quota_init(void)
 103{
 104        if (genl_register_family(&quota_genl_family) != 0)
 105                printk(KERN_ERR
 106                       "VFS: Failed to create quota netlink interface.\n");
 107        return 0;
 108};
 109
 110module_init(quota_init);
 111