LXR linux/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
  10static const struct genl_multicast_group quota_mcgrps[] = {
  11        { .name = "events", },
  12};
  13
  14/* Netlink family structure for quota */
  15static 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
  42void 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_64bit(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_64bit(skb, QUOTA_NL_A_EXCESS_ID,
  72                                from_kqid_munged(&init_user_ns, qid),
  73                                QUOTA_NL_A_PAD);
  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_64bit(skb, QUOTA_NL_A_CAUSED_ID,
  86                                from_kuid_munged(&init_user_ns, current_uid()),
  87                                QUOTA_NL_A_PAD);
  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;
  94attr_err_out:
  95        printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
  96err_out:
  97        kfree_skb(skb);
  98}
  99EXPORT_SYMBOL(quota_send_warning);
 100
 101static 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};
 108fs_initcall(quota_init);
 109