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

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Message-ID: <1566467448-9550-3-git-send-email-jan.dakinevich@virtuozzo.com>
Date:   Thu, 22 Aug 2019 09:50:51 +0000
From:   Jan Dakinevich <jan.dakinevich@...tuozzo.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Denis Lunev <den@...tuozzo.com>,
        Konstantin Khorenko <khorenko@...tuozzo.com>
Subject: [PATCH 2/3] netlink: always use vmapped memory for skb data

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@...tuozzo.com>
---
 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