Re: [PATCH net-next v13 11/13] net: add SO_DEVMEM_DONTNEED setsockopt to release RX frags

On 6/25/24 03:47, Mina Almasry wrote:

Add an interface for the user to notify the kernel that it is done reading the devmem dmabuf frags returned as cmsg. The kernel will drop the reference on the frags to make them available for reuse.

The sock_devmem_dontneed loop is a bit crude, but that can be handled by follow up patches.

Reviewed-by: Pavel Begunkov asml.silence@gmail.com

diff --git a/net/core/sock.c b/net/core/sock.c index 9abc4fe259535..040c66ac26244 100644 --- a/net/core/sock.c +++ b/net/core/sock.c

...

+#ifdef CONFIG_PAGE_POOL +static noinline_for_stack int +sock_devmem_dontneed(struct sock *sk, sockptr_t optval, unsigned int optlen) +{

• unsigned int num_tokens, i, j, k, netmem_num = 0;
• struct dmabuf_token *tokens;
• netmem_ref netmems[16];
• int ret = 0;
• if (sk->sk_type != SOCK_STREAM || sk->sk_protocol != IPPROTO_TCP)

• return -EBADF;
  

• if (optlen % sizeof(struct dmabuf_token) ||

•    optlen > sizeof(*tokens) * 128)
  

• return -EINVAL;
  

• tokens = kvmalloc_array(128, sizeof(*tokens), GFP_KERNEL);
• if (!tokens)

• return -ENOMEM;
  

• num_tokens = optlen / sizeof(struct dmabuf_token);
• if (copy_from_sockptr(tokens, optval, optlen)) {

• kvfree(tokens);
  

• return -EFAULT;
  

• }
• xa_lock_bh(&sk->sk_user_frags);
• for (i = 0; i < num_tokens; i++) {

• for (j = 0; j < tokens[i].token_count; j++) {
  

• 	netmem_ref netmem = (__force netmem_ref)__xa_erase(
  

• 		&sk->sk_user_frags, tokens[i].token_start + j);
  

• 	if (netmem &&
  

• 	    !WARN_ON_ONCE(!netmem_is_net_iov(netmem))) {
  

• 		netmems[netmem_num++] = netmem;
  

• 		if (netmem_num == ARRAY_SIZE(netmems)) {
  

• 			xa_unlock_bh(&sk->sk_user_frags);
  

• 			for (k = 0; k < netmem_num; k++)
  

• 				WARN_ON_ONCE(!napi_pp_put_page(netmems[k]));
  

• 			netmem_num = 0;
  

• 			xa_lock_bh(&sk->sk_user_frags);
  

• 		}
  

• 		ret++;
  

• 	}
  

• }
  

• }
• xa_unlock_bh(&sk->sk_user_frags);
• for (k = 0; k < netmem_num; k++)

• WARN_ON_ONCE(!napi_pp_put_page(netmems[k]));
  

• kvfree(tokens);
• return ret;

+} +#endif