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// SPDX-License-Identifier: GPL-2.0
#include <linux/cred.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/quotaops.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <net/netlink.h>
#include <net/genetlink.h>
static const struct genl_multicast_group quota_mcgrps[] = {
{ .name = "events", },
};
/* Netlink family structure for quota */
static struct genl_family quota_genl_family __ro_after_init = {
.module = THIS_MODULE,
.hdrsize = 0,
.name = "VFS_DQUOT",
.version = 1,
.maxattr = QUOTA_NL_A_MAX,
.mcgrps = quota_mcgrps,
.n_mcgrps = ARRAY_SIZE(quota_mcgrps),
};
/**
* quota_send_warning - Send warning to userspace about exceeded quota
* @qid: The kernel internal quota identifier.
* @dev: The device on which the fs is mounted (sb->s_dev)
* @warntype: The type of the warning: QUOTA_NL_...
*
* This can be used by filesystems (including those which don't use
* dquot) to send a message to userspace relating to quota limits.
*
*/
void quota_send_warning(struct kqid qid, dev_t dev,
const char warntype)
{
static atomic_t seq;
struct sk_buff *skb;
void *msg_head;
int ret;
int msg_size = 4 * nla_total_size(sizeof(u32)) +
2 * nla_total_size_64bit(sizeof(u64));
/* We have to allocate using GFP_NOFS as we are called from a
* filesystem performing write and thus further recursion into
* the fs to free some data could cause deadlocks. */
skb = genlmsg_new(msg_size, GFP_NOFS);
if (!skb) {
printk(KERN_ERR
"VFS: Not enough memory to send quota warning.\n");
return;
}
msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
"a_genl_family, 0, QUOTA_NL_C_WARNING);
if (!msg_head) {
printk(KERN_ERR
"VFS: Cannot store netlink header in quota warning.\n");
goto err_out;
}
ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
if (ret)
goto attr_err_out;
ret = nla_put_u64_64bit(skb, QUOTA_NL_A_EXCESS_ID,
from_kqid_munged(&init_user_ns, qid),
QUOTA_NL_A_PAD);
if (ret)
goto attr_err_out;
ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
if (ret)
goto attr_err_out;
ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
if (ret)
goto attr_err_out;
ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
if (ret)
goto attr_err_out;
ret = nla_put_u64_64bit(skb, QUOTA_NL_A_CAUSED_ID,
from_kuid_munged(&init_user_ns, current_uid()),
QUOTA_NL_A_PAD);
if (ret)
goto attr_err_out;
genlmsg_end(skb, msg_head);
genlmsg_multicast("a_genl_family, skb, 0, 0, GFP_NOFS);
return;
attr_err_out:
printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
err_out:
kfree_skb(skb);
}
EXPORT_SYMBOL(quota_send_warning);
static int __init quota_init(void)
{
if (genl_register_family("a_genl_family) != 0)
printk(KERN_ERR
"VFS: Failed to create quota netlink interface.\n");
return 0;
};
fs_initcall(quota_init);
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