[PATCH 2/3] netlink: always use vmapped memory for skb data

From: Jan Dakinevich
Date: Thu Aug 22 2019 - 09:45:17 EST


Don't make an exception for broadcast skb and allocate buffer for it in
the same way as for unicast skb.

- this makes needless calling of special destructor to free memory
under ->head,

- ...then, there is no need to reassign this destructor to cloned skb,

- ...then, netlink_skb_clone() become equal to generic skb_clone()
and can be dropped.

Signed-off-by: Jan Dakinevich <jan.dakinevich@xxxxxxxxxxxxx>
---
include/linux/netlink.h | 16 ----------------
net/ipv4/fib_frontend.c | 2 +-
net/netfilter/nfnetlink.c | 2 +-
net/netlink/af_netlink.c | 16 +++-------------
4 files changed, 5 insertions(+), 31 deletions(-)

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 205fa7b..daacffc 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -146,22 +146,6 @@ int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
int netlink_sendskb(struct sock *sk, struct sk_buff *skb);

-static inline struct sk_buff *
-netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
-{
- struct sk_buff *nskb;
-
- nskb = skb_clone(skb, gfp_mask);
- if (!nskb)
- return NULL;
-
- /* This is a large skb, set destructor callback to release head */
- if (is_vmalloc_addr(skb->head))
- nskb->destructor = skb->destructor;
-
- return nskb;
-}
-
/*
* skb should fit one page. This choice is good for headerless malloc.
* But we should limit to 8K so that userspace does not have to
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index e8bc939..cbbd75d 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1371,7 +1371,7 @@ static void nl_fib_input(struct sk_buff *skb)
nlmsg_len(nlh) < sizeof(*frn))
return;

- skb = netlink_skb_clone(skb, GFP_KERNEL);
+ skb = skb_clone(skb, GFP_KERNEL);
if (!skb)
return;
nlh = nlmsg_hdr(skb);
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 4abbb45..6ae22c9c 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -311,7 +311,7 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
replay:
status = 0;

- skb = netlink_skb_clone(oskb, GFP_KERNEL);
+ skb = skb_clone(oskb, GFP_KERNEL);
if (!skb)
return netlink_ack(oskb, nlh, -ENOMEM, NULL);

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 90b2ab9..04a3457 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -360,13 +360,6 @@ static void netlink_rcv_wake(struct sock *sk)

static void netlink_skb_destructor(struct sk_buff *skb)
{
- if (is_vmalloc_addr(skb->head)) {
- if (!skb->cloned ||
- !atomic_dec_return(&(skb_shinfo(skb)->dataref)))
- vfree(skb->head);
-
- skb->head = NULL;
- }
if (skb->sk != NULL)
sock_rfree(skb);
}
@@ -1164,13 +1157,12 @@ struct sock *netlink_getsockbyfilp(struct file *filp)
return sock;
}

-static struct sk_buff *netlink_alloc_large_skb(unsigned int size,
- int broadcast)
+static struct sk_buff *netlink_alloc_large_skb(unsigned int size)
{
struct sk_buff *skb;
void *data;

- if (size <= NLMSG_GOODSIZE || broadcast)
+ if (size <= NLMSG_GOODSIZE)
return alloc_skb(size, GFP_KERNEL);

size = SKB_DATA_ALIGN(size) +
@@ -1183,8 +1175,6 @@ static struct sk_buff *netlink_alloc_large_skb(unsigned int size,
skb = __build_skb(data, size);
if (skb == NULL)
vfree(data);
- else
- skb->destructor = netlink_skb_destructor;

return skb;
}
@@ -1889,7 +1879,7 @@ static int netlink_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
if (len > sk->sk_sndbuf - 32)
goto out;
err = -ENOBUFS;
- skb = netlink_alloc_large_skb(len, dst_group);
+ skb = netlink_alloc_large_skb(len);
if (skb == NULL)
goto out;

--
2.1.4