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Subject[PATCH 38/40] netlink: add SOCK_VMIO support to AF_NETLINK
Modify the netlink code so that SOCK_VMIO has the desired effect on the
user-space side of the connection.

Modify sys_{send,recv}msg to use sk->sk_allocation instead of GFP_KERNEL,
this should not change existing behaviour because the default of
sk->sk_allocation is GFP_KERNEL, and no user-space exposed socket would
have it any different at this time.

This change allows the system calls to succeed for SOCK_VMIO sockets
(who have sk->sk_allocation |= GFP_EMERGENCY) even under extreme memory
pressure.

Since netlink_sendmsg is used to transfer msgs from user- to kernel-space
treat the skb allocation there as a receive allocation.

Also export netlink_lookup, this is needed to locate the kernel side struct
sock object associated with the user-space netlink socket.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: David Miller <davem@davemloft.net>
Cc: Mike Christie <michaelc@cs.wisc.edu>
---
include/linux/netlink.h | 1 +
net/compat.c | 2 +-
net/netlink/af_netlink.c | 12 +++++++++---
net/socket.c | 6 +++---
4 files changed, 14 insertions(+), 7 deletions(-)

Index: linux-2.6-git/net/netlink/af_netlink.c
===================================================================
--- linux-2.6-git.orig/net/netlink/af_netlink.c
+++ linux-2.6-git/net/netlink/af_netlink.c
@@ -203,7 +203,7 @@ netlink_unlock_table(void)
wake_up(&nl_table_wait);
}

-static __inline__ struct sock *netlink_lookup(int protocol, u32 pid)
+struct sock *netlink_lookup(int protocol, u32 pid)
{
struct nl_pid_hash *hash = &nl_table[protocol].hash;
struct hlist_head *head;
@@ -1157,7 +1157,7 @@ static int netlink_sendmsg(struct kiocb
if (len > sk->sk_sndbuf - 32)
goto out;
err = -ENOBUFS;
- skb = alloc_skb(len, GFP_KERNEL);
+ skb = __alloc_skb(len, GFP_KERNEL, SKB_ALLOC_RX, -1);
if (skb==NULL)
goto out;

@@ -1186,8 +1186,13 @@ static int netlink_sendmsg(struct kiocb
}

if (dst_group) {
+ gfp_t gfp_mask = sk->sk_allocation;
+
+ if (skb_emergency(skb))
+ gfp_mask |= __GFP_EMERGENCY;
+
atomic_inc(&skb->users);
- netlink_broadcast(sk, skb, dst_pid, dst_group, GFP_KERNEL);
+ netlink_broadcast(sk, skb, dst_pid, dst_group, gfp_mask);
}
err = netlink_unicast(sk, skb, dst_pid, msg->msg_flags&MSG_DONTWAIT);

@@ -1850,6 +1855,7 @@ panic:

core_initcall(netlink_proto_init);

+EXPORT_SYMBOL(netlink_lookup);
EXPORT_SYMBOL(netlink_ack);
EXPORT_SYMBOL(netlink_run_queue);
EXPORT_SYMBOL(netlink_broadcast);
Index: linux-2.6-git/net/socket.c
===================================================================
--- linux-2.6-git.orig/net/socket.c
+++ linux-2.6-git/net/socket.c
@@ -1817,7 +1817,7 @@ asmlinkage long sys_sendmsg(int fd, stru
err = -ENOMEM;
iov_size = msg_sys.msg_iovlen * sizeof(struct iovec);
if (msg_sys.msg_iovlen > UIO_FASTIOV) {
- iov = sock_kmalloc(sock->sk, iov_size, GFP_KERNEL);
+ iov = sock_kmalloc(sock->sk, iov_size, sock->sk->sk_allocation);
if (!iov)
goto out_put;
}
@@ -1846,7 +1846,7 @@ asmlinkage long sys_sendmsg(int fd, stru
ctl_len = msg_sys.msg_controllen;
} else if (ctl_len) {
if (ctl_len > sizeof(ctl)) {
- ctl_buf = sock_kmalloc(sock->sk, ctl_len, GFP_KERNEL);
+ ctl_buf = sock_kmalloc(sock->sk, ctl_len, sock->sk->sk_allocation);
if (ctl_buf == NULL)
goto out_freeiov;
}
@@ -1922,7 +1922,7 @@ asmlinkage long sys_recvmsg(int fd, stru
err = -ENOMEM;
iov_size = msg_sys.msg_iovlen * sizeof(struct iovec);
if (msg_sys.msg_iovlen > UIO_FASTIOV) {
- iov = sock_kmalloc(sock->sk, iov_size, GFP_KERNEL);
+ iov = sock_kmalloc(sock->sk, iov_size, sock->sk->sk_allocation);
if (!iov)
goto out_put;
}
Index: linux-2.6-git/include/linux/netlink.h
===================================================================
--- linux-2.6-git.orig/include/linux/netlink.h
+++ linux-2.6-git/include/linux/netlink.h
@@ -157,6 +157,7 @@ struct netlink_skb_parms
#define NETLINK_CREDS(skb) (&NETLINK_CB((skb)).creds)


+extern struct sock *netlink_lookup(int protocol, __u32 pid);
extern struct sock *netlink_kernel_create(int unit, unsigned int groups,
void (*input)(struct sock *sk, int len),
struct mutex *cb_mutex,
Index: linux-2.6-git/net/compat.c
===================================================================
--- linux-2.6-git.orig/net/compat.c
+++ linux-2.6-git/net/compat.c
@@ -169,7 +169,7 @@ int cmsghdr_from_user_compat_to_kern(str
* from the user.
*/
if (kcmlen > stackbuf_size)
- kcmsg_base = kcmsg = sock_kmalloc(sk, kcmlen, GFP_KERNEL);
+ kcmsg_base = kcmsg = sock_kmalloc(sk, kcmlen, sk->sk_allocation);
if (kcmsg == NULL)
return -ENOBUFS;

--

-
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