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