Root/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 */
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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