Re: [virtio-dev] Re: [PATCH 2/6] vsock: return errors other than -ENOMEM to socket

[Arseniy Krasnov]

On 16.08.2022 05:30, Bobby Eshleman wrote:
> CC'ing virtio-dev@xxxxxxxxxxxxxxxxxxxx
> 
> On Mon, Aug 15, 2022 at 10:56:05AM -0700, Bobby Eshleman wrote:
>> This commit allows vsock implementations to return errors
>> to the socket layer other than -ENOMEM. One immediate effect
>> of this is that upon the sk_sndbuf threshold being reached -EAGAIN
>> will be returned and userspace may throttle appropriately.
>>
>> Resultingly, a known issue with uperf is resolved[1].
>>
>> Additionally, to preserve legacy behavior for non-virtio
>> implementations, hyperv/vmci force errors to be -ENOMEM so that behavior
>> is unchanged.
>>
>> [1]: https://gitlab.com/vsock/vsock/-/issues/1
>>
>> Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
>> ---
>>  include/linux/virtio_vsock.h            | 3 +++
>>  net/vmw_vsock/af_vsock.c                | 3 ++-
>>  net/vmw_vsock/hyperv_transport.c        | 2 +-
>>  net/vmw_vsock/virtio_transport_common.c | 3 ---
>>  net/vmw_vsock/vmci_transport.c          | 9 ++++++++-
>>  5 files changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>> index 17ed01466875..9a37eddbb87a 100644
>> --- a/include/linux/virtio_vsock.h
>> +++ b/include/linux/virtio_vsock.h
>> @@ -8,6 +8,9 @@
>>  #include <net/sock.h>
>>  #include <net/af_vsock.h>
>>  
>> +/* Threshold for detecting small packets to copy */
>> +#define GOOD_COPY_LEN  128
>> +
>>  enum virtio_vsock_metadata_flags {
>>  	VIRTIO_VSOCK_METADATA_FLAGS_REPLY		= BIT(0),
>>  	VIRTIO_VSOCK_METADATA_FLAGS_TAP_DELIVERED	= BIT(1),
>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> index e348b2d09eac..1893f8aafa48 100644
>> --- a/net/vmw_vsock/af_vsock.c
>> +++ b/net/vmw_vsock/af_vsock.c
>> @@ -1844,8 +1844,9 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
>>  			written = transport->stream_enqueue(vsk,
>>  					msg, len - total_written);
>>  		}
>> +
>>  		if (written < 0) {
>> -			err = -ENOMEM;
>> +			err = written;
>>  			goto out_err;
>>  		}
IIUC, for stream, this thing will have effect, only one first transport access fails. In this
case 'total_written' will be 0, so 'err' == 'written' will be returned. But when 'total_written > 0',
'err' will be overwritten by 'total_written' below, preserving current behaviour. Is it what You
supposed?

Thanks
>>  
>> diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
>> index fd98229e3db3..e99aea571f6f 100644
>> --- a/net/vmw_vsock/hyperv_transport.c
>> +++ b/net/vmw_vsock/hyperv_transport.c
>> @@ -687,7 +687,7 @@ static ssize_t hvs_stream_enqueue(struct vsock_sock *vsk, struct msghdr *msg,
>>  	if (bytes_written)
>>  		ret = bytes_written;
>>  	kfree(send_buf);
>> -	return ret;
>> +	return ret < 0 ? -ENOMEM : ret;
>>  }
>>  
>>  static s64 hvs_stream_has_data(struct vsock_sock *vsk)
>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> index 920578597bb9..d5780599fe93 100644
>> --- a/net/vmw_vsock/virtio_transport_common.c
>> +++ b/net/vmw_vsock/virtio_transport_common.c
>> @@ -23,9 +23,6 @@
>>  /* How long to wait for graceful shutdown of a connection */
>>  #define VSOCK_CLOSE_TIMEOUT (8 * HZ)
>>  
>> -/* Threshold for detecting small packets to copy */
>> -#define GOOD_COPY_LEN  128
>> -
>>  static const struct virtio_transport *
>>  virtio_transport_get_ops(struct vsock_sock *vsk)
>>  {
>> diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
>> index b14f0ed7427b..c927a90dc859 100644
>> --- a/net/vmw_vsock/vmci_transport.c
>> +++ b/net/vmw_vsock/vmci_transport.c
>> @@ -1838,7 +1838,14 @@ static ssize_t vmci_transport_stream_enqueue(
>>  	struct msghdr *msg,
>>  	size_t len)
>>  {
>> -	return vmci_qpair_enquev(vmci_trans(vsk)->qpair, msg, len, 0);
>> +	int err;
>> +
>> +	err = vmci_qpair_enquev(vmci_trans(vsk)->qpair, msg, len, 0);
>> +
>> +	if (err < 0)
>> +		err = -ENOMEM;
>> +
>> +	return err;
>>  }
>>  
>>  static s64 vmci_transport_stream_has_data(struct vsock_sock *vsk)
>> -- 
>> 2.35.1
>>
> 
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