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@google.com>
Reviewed-by: Zhengchao Shao <shaozhengchao@huawei.com>
Link: https://lore.kernel.org/r/20240224090630.605917-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index be5792b638aa563232cdb96de8c97c4fe45b3718..765921cf119486359109a15e62ee93cca1d439e9 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1202,23 +1202,21 @@ 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;