netdev - [PATCH net-next] netlink: use kvmalloc() in netlink_alloc_large

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Message-ID: <20240224090630.605917-1-edumazet@google.com>
Date: Sat, 24 Feb 2024 09:06:30 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>, Zhengchao Shao <shaozhengchao@...wei.com>
Subject: [PATCH net-next] netlink: use kvmalloc() in netlink_alloc_large_skb()

This is a followup of commit 234ec0b6034b ("netlink: fix potential
sleeping issue in mqueue_flush_file"), because vfree_atomic()
overhead is unfortunate for medium sized allocations.

1) If the allocation is smaller than PAGE_SIZE, do not bother
   with vmalloc() at all. Some arches have 64KB PAGE_SIZE,
   while NLMSG_GOODSIZE is smaller than 8KB.

2) Use kvmalloc(), which might allocate one high order page
   instead of vmalloc if memory is not too fragmented.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Zhengchao Shao <shaozhengchao@...wei.com>
---
 net/netlink/af_netlink.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 9c962347cf859f16fc76e4d8a2fd22cdb3d142d6..90ca4e0ed9b3632bf223bf29fd864dbb76f3c89c 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1206,23 +1206,21 @@ struct sock *netlink_getsockbyfilp(struct file *filp)
 
 struct sk_buff *netlink_alloc_large_skb(unsigned int size, int broadcast)
 {
+	size_t head_size = SKB_HEAD_ALIGN(size);
 	struct sk_buff *skb;
 	void *data;
 
-	if (size <= NLMSG_GOODSIZE || broadcast)
+	if (head_size <= PAGE_SIZE || broadcast)
 		return alloc_skb(size, GFP_KERNEL);
 
-	size = SKB_DATA_ALIGN(size) +
-	       SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
-
-	data = vmalloc(size);
-	if (data == NULL)
+	data = kvmalloc(head_size, GFP_KERNEL);
+	if (!data)
 		return NULL;
 
-	skb = __build_skb(data, size);
-	if (skb == NULL)
-		vfree(data);
-	else
+	skb = __build_skb(data, head_size);
+	if (!skb)
+		kvfree(data);
+	else if (is_vmalloc_addr(data))
 		skb->destructor = netlink_skb_destructor;
 
 	return skb;
-- 
2.44.0.rc1.240.g4c46232300-goog