Linux Virtualization - Mar 2023 - [RFC PATCH v3 0/4] several updates to virtio/vsock

On Thu, Mar 09, 2023 at 07:20:20PM +0300, Arseniy Krasnov
wrote:
>
>
>On 09.03.2023 19:21, Stefano Garzarella wrote:
>> On Thu, Mar 09, 2023 at 01:10:36PM +0300, Arseniy Krasnov wrote:
>>> Hello,
>>>
>>> this patchset evolved from previous v2 version (see link below). It
does
>>> several updates to virtio/vsock:
>>> 1) Changes 'virtio_transport_inc/dec_rx_pkt()' interface.
Now instead of
>>> ? using skbuff state ('head' and 'data' pointers)
to update 'fwd_cnt'
>>> ? and 'rx_bytes', integer value is passed as an input
argument. This
>>> ? makes code more simple, because in this case we don't need to
udpate
>>> ? skbuff state before calling
'virtio_transport_inc/dec_rx_pkt()'. In
>>> ? more common words - we don't need to change skbuff state to
update
>>> ? 'rx_bytes' and 'fwd_cnt' correctly.
>>> 2) For SOCK_STREAM, when copying data to user fails, current skbuff
is
>>> ? not dropped. Next read attempt will use same skbuff and last
offset.
>>> ? Instead of 'skb_dequeue()', 'skb_peek()' +
'__skb_unlink()' are used.
>>> ? This behaviour was implemented before skbuff support.
>>> 3) For SOCK_SEQPACKET it removes unneeded 'skb_pull()'
call, because for
>>> ? this type of socket each skbuff is used only once: after removing
it
>>> ? from socket's queue, it will be freed anyway.
>>>
>>> Test for 2) also added:
>>> Test tries to 'recv()' data to NULL buffer, then does
'recv()' with valid
>>> buffer. For SOCK_STREAM second 'recv()' must return data,
because skbuff
>>> must not be dropped, but for SOCK_SEQPACKET skbuff will be dropped
by
>>> kernel, and 'recv()' will return EAGAIN.
>>>
>>> Link to v1 on lore:
>>> https://lore.kernel.org/netdev/c2d3e204-89d9-88e9-8a15-3fe027e56b4b
at sberdevices.ru/
>>>
>>> Link to v2 on lore:
>>> https://lore.kernel.org/netdev/a7ab414b-5e41-c7b6-250b-e8401f335859
at sberdevices.ru/
>>>
>>> Change log:
>>>
>>> v1 -> v2:
>>> - For SOCK_SEQPACKET call 'skb_pull()' also in case of copy
failure or
>>> ? dropping skbuff (when we just waiting message end).
>>> - Handle copy failure for SOCK_STREAM in the same manner (plus free
>>> ? current skbuff).
>>> - Replace bug repdroducer with new test in vsock_test.c
>>>
>>> v2 -> v3:
>>> - Replace patch which removes 'skb->len' subtraction
from function
>>> ? 'virtio_transport_dec_rx_pkt()' with patch which updates
functions
>>> ? 'virtio_transport_inc/dec_rx_pkt()' by passing integer
argument
>>> ? instead of skbuff pointer.
>>> - Replace patch which drops skbuff when copying to user fails with
>>> ? patch which changes this behaviour by keeping skbuff in queue
until
>>> ? it has no data.
>>> - Add patch for SOCK_SEQPACKET which removes redundant
'skb_pull()'
>>> ? call on read.
>>> - I remove "Fixes" tag from all patches, because all of
them now change
>>> ? code logic, not only fix something.
>>
>> Yes, but they solve the problem, so we should use the tag (I think at
>> least in patch 1 and 3).
>>
>> We usually use the tag when we are fixing a problem introduced by a
>> previous change. So we need to backport the patch to the stable
branches
>> as well, and we need the tag to figure out which branches have the
patch
>> or not.
>Ahh, sorry. Ok. I see now :)
No problem at all :-)

I think also patch 2 can have the Fixes tag.

Thanks,
Stefano
>
>Thanks, Arseniy
>>
>> Thanks,
>> Stefano
>>
>>>
>>> Arseniy Krasnov (4):
>>> ?virtio/vsock: don't use skbuff state to account credit
>>> ?virtio/vsock: remove redundant 'skb_pull()' call
>>> ?virtio/vsock: don't drop skbuff on copy failure
>>> ?test/vsock: copy to user failure test
>>>
>>> net/vmw_vsock/virtio_transport_common.c |? 29 +++---
>>> tools/testing/vsock/vsock_test.c??????? | 118
++++++++++++++++++++++++
>>> 2 files changed, 131 insertions(+), 16 deletions(-)
>>>
>>> --?
>>> 2.25.1
>>>
>>
>