RE: [RFC 08/13] cifs: Add a function to read into an iter from a socket

David Laight
2023-01-26T09:27:10Z

From: David Howells
> Sent: 25 January 2023 21:46

> Add a helper function to read data from a socket into the given iterator.
...
> +int
> +cifs_read_iter_from_socket(struct TCP_Server_Info *server, struct iov_iter *iter,
> + unsigned int to_read)
> +{
> + struct msghdr smb_msg;
> + int ret;
> +
> + smb_msg.msg_iter = *iter;
> + if (smb_msg.msg_iter.count > to_read)
> + smb_msg.msg_iter.count = to_read;
> + ret = cifs_readv_from_socket(server, &smb_msg);
> + if (ret > 0)
> + iov_iter_advance(iter, ret);
> + return ret;
> +}

On the face of it that passes a largely uninitialised 'struct msghdr'
to cifs_readv_from_socket() in order to pass an iov_iter.
That seems to be asking for trouble.

I'm also not 100% sure that taking a copy of an iov_iter is a good idea.

If cifs_readv_from_socket() only needs the iov_iter then wouldn't
it be better to do the wrapper the other way around?
(Probably as an inline function)
Something like:

int
cifs_readv_from_socket(struct TCP_Server_Info *server, struct msghdr *smb_msg)
{
return cifs_read_iter_from_socket(server, &smb_msg->msg_iter, smb_msg->msg_iter.count);
}

and then changing cifs_readv_from_socket() to just use the iov_iter.

David

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