linux/fs/quota/netlink.c
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   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 */
  13static 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
  33void 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;
  81attr_err_out:
  82        printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
  83err_out:
  84        kfree_skb(skb);
  85}
  86EXPORT_SYMBOL(quota_send_warning);
  87
  88static 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
  96module_init(quota_init);
  97
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