linux/drivers/scsi/scsi_netlink.c
Denis V. Lunev cd40b7d398 [NET]: make netlink user -> kernel interface synchronious
This patch make processing netlink user -> kernel messages synchronious.
This change was inspired by the talk with Alexey Kuznetsov about current
netlink messages processing. He says that he was badly wrong when introduced 
asynchronious user -> kernel communication.

The call netlink_unicast is the only path to send message to the kernel
netlink socket. But, unfortunately, it is also used to send data to the
user.

Before this change the user message has been attached to the socket queue
and sk->sk_data_ready was called. The process has been blocked until all
pending messages were processed. The bad thing is that this processing
may occur in the arbitrary process context.

This patch changes nlk->data_ready callback to get 1 skb and force packet
processing right in the netlink_unicast.

Kernel -> user path in netlink_unicast remains untouched.

EINTR processing for in netlink_run_queue was changed. It forces rtnl_lock
drop, but the process remains in the cycle until the message will be fully
processed. So, there is no need to use this kludges now.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-10 21:15:29 -07:00

180 lines
3.9 KiB
C

/*
* scsi_netlink.c - SCSI Transport Netlink Interface
*
* Copyright (C) 2006 James Smart, Emulex Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <linux/time.h>
#include <linux/jiffies.h>
#include <linux/security.h>
#include <net/sock.h>
#include <net/netlink.h>
#include <scsi/scsi_netlink.h>
#include "scsi_priv.h"
struct sock *scsi_nl_sock = NULL;
EXPORT_SYMBOL_GPL(scsi_nl_sock);
/**
* scsi_nl_rcv_msg -
* Receive message handler. Extracts message from a receive buffer.
* Validates message header and calls appropriate transport message handler
*
* @skb: socket receive buffer
*
**/
static void
scsi_nl_rcv_msg(struct sk_buff *skb)
{
struct nlmsghdr *nlh;
struct scsi_nl_hdr *hdr;
uint32_t rlen;
int err;
while (skb->len >= NLMSG_SPACE(0)) {
err = 0;
nlh = nlmsg_hdr(skb);
if ((nlh->nlmsg_len < (sizeof(*nlh) + sizeof(*hdr))) ||
(skb->len < nlh->nlmsg_len)) {
printk(KERN_WARNING "%s: discarding partial skb\n",
__FUNCTION__);
return;
}
rlen = NLMSG_ALIGN(nlh->nlmsg_len);
if (rlen > skb->len)
rlen = skb->len;
if (nlh->nlmsg_type != SCSI_TRANSPORT_MSG) {
err = -EBADMSG;
return;
}
hdr = NLMSG_DATA(nlh);
if ((hdr->version != SCSI_NL_VERSION) ||
(hdr->magic != SCSI_NL_MAGIC)) {
err = -EPROTOTYPE;
goto next_msg;
}
if (security_netlink_recv(skb, CAP_SYS_ADMIN)) {
err = -EPERM;
goto next_msg;
}
if (nlh->nlmsg_len < (sizeof(*nlh) + hdr->msglen)) {
printk(KERN_WARNING "%s: discarding partial message\n",
__FUNCTION__);
return;
}
/*
* We currently don't support anyone sending us a message
*/
next_msg:
if ((err) || (nlh->nlmsg_flags & NLM_F_ACK))
netlink_ack(skb, nlh, err);
skb_pull(skb, rlen);
}
}
/**
* scsi_nl_rcv_event -
* Event handler for a netlink socket.
*
* @this: event notifier block
* @event: event type
* @ptr: event payload
*
**/
static int
scsi_nl_rcv_event(struct notifier_block *this, unsigned long event, void *ptr)
{
struct netlink_notify *n = ptr;
if (n->protocol != NETLINK_SCSITRANSPORT)
return NOTIFY_DONE;
/*
* Currently, we are not tracking PID's, etc. There is nothing
* to handle.
*/
return NOTIFY_DONE;
}
static struct notifier_block scsi_netlink_notifier = {
.notifier_call = scsi_nl_rcv_event,
};
/**
* scsi_netlink_init -
* Called by SCSI subsystem to intialize the SCSI transport netlink
* interface
*
**/
void
scsi_netlink_init(void)
{
int error;
error = netlink_register_notifier(&scsi_netlink_notifier);
if (error) {
printk(KERN_ERR "%s: register of event handler failed - %d\n",
__FUNCTION__, error);
return;
}
scsi_nl_sock = netlink_kernel_create(&init_net, NETLINK_SCSITRANSPORT,
SCSI_NL_GRP_CNT, scsi_nl_rcv_msg, NULL,
THIS_MODULE);
if (!scsi_nl_sock) {
printk(KERN_ERR "%s: register of recieve handler failed\n",
__FUNCTION__);
netlink_unregister_notifier(&scsi_netlink_notifier);
}
return;
}
/**
* scsi_netlink_exit -
* Called by SCSI subsystem to disable the SCSI transport netlink
* interface
*
**/
void
scsi_netlink_exit(void)
{
if (scsi_nl_sock) {
sock_release(scsi_nl_sock->sk_socket);
netlink_unregister_notifier(&scsi_netlink_notifier);
}
return;
}