[RFC PATCH v3 0/9] vsock: updates for SO_RCVLOWAT handling

[RFC PATCH v3 0/9] vsock: updates for SO_RCVLOWAT handling

[Arseniy Krasnov]

Hello,

This patchset includes some updates for SO_RCVLOWAT:

1) af_vsock:
   During my experiments with zerocopy receive, i found, that in some
   cases, poll() implementation violates POSIX: when socket has non-
   default SO_RCVLOWAT(e.g. not 1), poll() will always set POLLIN and
   POLLRDNORM bits in 'revents' even number of bytes available to read
   on socket is smaller than SO_RCVLOWAT value. In this case,user sees
   POLLIN flag and then tries to read data(for example using  'read()'
   call), but read call will be blocked, because  SO_RCVLOWAT logic is
   supported in dequeue loop in af_vsock.c. But the same time,  POSIX
   requires that:

   "POLLIN     Data other than high-priority data may be read without
               blocking.
    POLLRDNORM Normal data may be read without blocking."

   See https://www.open-std.org/jtc1/sc22/open/n4217.pdf, page 293.

   So, we have, that poll() syscall returns POLLIN, but read call will
   be blocked.

   Also in man page socket(7) i found that:

   "Since Linux 2.6.28, select(2), poll(2), and epoll(7) indicate a
   socket as readable only if at least SO_RCVLOWAT bytes are available."

   I checked TCP callback for poll()(net/ipv4/tcp.c, tcp_poll()), it
   uses SO_RCVLOWAT value to set POLLIN bit, also i've tested TCP with
   this case for TCP socket, it works as POSIX required.

   I've added some fixes to af_vsock.c and virtio_transport_common.c,
   test is also implemented.

2) virtio/vsock:
   It adds some optimization to wake ups, when new data arrived. Now,
   SO_RCVLOWAT is considered before wake up sleepers who wait new data.
   There is no sense, to kick waiter, when number of available bytes
   in socket's queue < SO_RCVLOWAT, because if we wake up reader in
   this case, it will wait for SO_RCVLOWAT data anyway during dequeue,
   or in poll() case, POLLIN/POLLRDNORM bits won't be set, so such
   exit from poll() will be "spurious". This logic is also used in TCP
   sockets.

3) vmci/vsock:
   Same as 2), but i'm not sure about this changes. Will be very good,
   to get comments from someone who knows this code.

4) Hyper-V:
   As Dexuan Cui mentioned, for Hyper-V transport it is difficult to
   support SO_RCVLOWAT, so he suggested to disable this feature for
   Hyper-V.

Thank You

Arseniy Krasnov(9):
 vsock: SO_RCVLOWAT transport set callback
 hv_sock: disable SO_RCVLOWAT support
 virtio/vsock: use 'target' in notify_poll_in callback
 vmci/vsock: use 'target' in notify_poll_in callback
 vsock: pass sock_rcvlowat to notify_poll_in as target
 vsock: add API call for data ready
 virtio/vsock: check SO_RCVLOWAT before wake up reader
 vmci/vsock: check SO_RCVLOWAT before wake up reader
 vsock_test: POLLIN + SO_RCVLOWAT test

 include/net/af_vsock.h                       |   2 +
 net/vmw_vsock/af_vsock.c                     |  38 +++++++++-
 net/vmw_vsock/hyperv_transport.c             |   7 ++
 net/vmw_vsock/virtio_transport_common.c      |   7 +-
 net/vmw_vsock/vmci_transport_notify.c        |  10 +--
 net/vmw_vsock/vmci_transport_notify_qstate.c |  12 +--
 tools/testing/vsock/vsock_test.c             | 107 +++++++++++++++++++++++++++
 7 files changed, 166 insertions(+), 17 deletions(-)

 Changelog:

 v1 -> v2:
 1) Patches for VMCI transport(same as for virtio-vsock).
 2) Patches for Hyper-V transport(disabling SO_RCVLOWAT setting).
 3) Waiting logic in test was updated(sleep() -> poll()).

 v2 -> v3:
 1) Patches were reordered.
 2) Commit message updated in 0005.
 3) Check 'transport' pointer in 0001 for NULL.
 4) Check 'value' in 0001 for > buffer_size.

-- 
2.25.1

[RFC PATCH v3 1/9] vsock: SO_RCVLOWAT transport set callback

[Arseniy Krasnov]

This adds transport specific callback for SO_RCVLOWAT, because in some
transports it may be difficult to know current available number of bytes
ready to read. Thus, when SO_RCVLOWAT is set, transport may reject it.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 include/net/af_vsock.h   |  1 +
 net/vmw_vsock/af_vsock.c | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index f742e50207fb..eae5874bae35 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -134,6 +134,7 @@ struct vsock_transport {
 	u64 (*stream_rcvhiwat)(struct vsock_sock *);
 	bool (*stream_is_active)(struct vsock_sock *);
 	bool (*stream_allow)(u32 cid, u32 port);
+	int (*set_rcvlowat)(struct vsock_sock *, int);
 
 	/* SEQ_PACKET. */
 	ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index f04abf662ec6..016ad5ff78b7 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -2129,6 +2129,30 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	return err;
 }
 
+static int vsock_set_rcvlowat(struct sock *sk, int val)
+{
+	const struct vsock_transport *transport;
+	struct vsock_sock *vsk;
+	int err = 0;
+
+	vsk = vsock_sk(sk);
+
+	if (val > vsk->buffer_size)
+		return -EINVAL;
+
+	transport = vsk->transport;
+
+	if (!transport)
+		return -EOPNOTSUPP;
+
+	if (transport->set_rcvlowat)
+		err = transport->set_rcvlowat(vsk, val);
+	else
+		WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
+
+	return err;
+}
+
 static const struct proto_ops vsock_stream_ops = {
 	.family = PF_VSOCK,
 	.owner = THIS_MODULE,
@@ -2148,6 +2172,7 @@ static const struct proto_ops vsock_stream_ops = {
 	.recvmsg = vsock_connectible_recvmsg,
 	.mmap = sock_no_mmap,
 	.sendpage = sock_no_sendpage,
+	.set_rcvlowat = vsock_set_rcvlowat,
 };
 
 static const struct proto_ops vsock_seqpacket_ops = {
-- 
2.25.1

Re: [RFC PATCH v3 1/9] vsock: SO_RCVLOWAT transport set callback

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 01:51:05PM +0000, Arseniy Krasnov wrote:
>This adds transport specific callback for SO_RCVLOWAT, because in some
>transports it may be difficult to know current available number of bytes
>ready to read. Thus, when SO_RCVLOWAT is set, transport may reject it.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> include/net/af_vsock.h   |  1 +
> net/vmw_vsock/af_vsock.c | 25 +++++++++++++++++++++++++
> 2 files changed, 26 insertions(+)
>
>diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>index f742e50207fb..eae5874bae35 100644
>--- a/include/net/af_vsock.h
>+++ b/include/net/af_vsock.h
>@@ -134,6 +134,7 @@ struct vsock_transport {
> 	u64 (*stream_rcvhiwat)(struct vsock_sock *);
> 	bool (*stream_is_active)(struct vsock_sock *);
> 	bool (*stream_allow)(u32 cid, u32 port);
>+	int (*set_rcvlowat)(struct vsock_sock *, int);

checkpatch suggests to add identifier names. For some we put them in, 
for others we didn't, but I suggest putting them in for the new ones 
because I think it's clearer too.

WARNING: function definition argument 'struct vsock_sock *' should also 
have an identifier name
#25: FILE: include/net/af_vsock.h:137:
+	int (*set_rcvlowat)(struct vsock_sock *, int);

WARNING: function definition argument 'int' should also have an identifier name
#25: FILE: include/net/af_vsock.h:137:
+	int (*set_rcvlowat)(struct vsock_sock *, int);

total: 0 errors, 2 warnings, 0 checks, 44 lines checked

>
> 	/* SEQ_PACKET. */
> 	ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index f04abf662ec6..016ad5ff78b7 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -2129,6 +2129,30 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 	return err;
> }
>
>+static int vsock_set_rcvlowat(struct sock *sk, int val)
>+{
>+	const struct vsock_transport *transport;
>+	struct vsock_sock *vsk;
>+	int err = 0;
>+
>+	vsk = vsock_sk(sk);
>+
>+	if (val > vsk->buffer_size)
>+		return -EINVAL;
>+
>+	transport = vsk->transport;
>+
>+	if (!transport)
>+		return -EOPNOTSUPP;

I don't know whether it is better in this case to write it in 
sk->sk_rcvlowat, maybe we can return EOPNOTSUPP only when the trasport 
is assigned and set_rcvlowat is not defined. This is because usually the 
options are set just after creation, when the transport is practically 
unassigned.

I mean something like this:

         if (transport) {
                 if (transport->set_rcvlowat)
                         return transport->set_rcvlowat(vsk, val);
                 else
                         return -EOPNOTSUPP;
         }

         WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);

         return 0;

>+
>+	if (transport->set_rcvlowat)
>+		err = transport->set_rcvlowat(vsk, val);
>+	else
>+		WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>+
>+	return err;
>+}
>+
> static const struct proto_ops vsock_stream_ops = {
> 	.family = PF_VSOCK,
> 	.owner = THIS_MODULE,
>@@ -2148,6 +2172,7 @@ static const struct proto_ops vsock_stream_ops = {
> 	.recvmsg = vsock_connectible_recvmsg,
> 	.mmap = sock_no_mmap,
> 	.sendpage = sock_no_sendpage,
>+	.set_rcvlowat = vsock_set_rcvlowat,
> };
>
> static const struct proto_ops vsock_seqpacket_ops = {
>-- 
>2.25.1

Re: [RFC PATCH v3 1/9] vsock: SO_RCVLOWAT transport set callback

[Stefano Garzarella]

On Mon, Aug 8, 2022 at 12:23 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> On Wed, Aug 03, 2022 at 01:51:05PM +0000, Arseniy Krasnov wrote:
> >This adds transport specific callback for SO_RCVLOWAT, because in some
> >transports it may be difficult to know current available number of bytes
> >ready to read. Thus, when SO_RCVLOWAT is set, transport may reject it.
> >
> >Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
> >---
> > include/net/af_vsock.h   |  1 +
> > net/vmw_vsock/af_vsock.c | 25 +++++++++++++++++++++++++
> > 2 files changed, 26 insertions(+)
> >
> >diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> >index f742e50207fb..eae5874bae35 100644
> >--- a/include/net/af_vsock.h
> >+++ b/include/net/af_vsock.h
> >@@ -134,6 +134,7 @@ struct vsock_transport {
> >       u64 (*stream_rcvhiwat)(struct vsock_sock *);
> >       bool (*stream_is_active)(struct vsock_sock *);
> >       bool (*stream_allow)(u32 cid, u32 port);
> >+      int (*set_rcvlowat)(struct vsock_sock *, int);
>
> checkpatch suggests to add identifier names. For some we put them in,
> for others we didn't, but I suggest putting them in for the new ones
> because I think it's clearer too.
>
> WARNING: function definition argument 'struct vsock_sock *' should also
> have an identifier name
> #25: FILE: include/net/af_vsock.h:137:
> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>
> WARNING: function definition argument 'int' should also have an identifier name
> #25: FILE: include/net/af_vsock.h:137:
> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>
> total: 0 errors, 2 warnings, 0 checks, 44 lines checked
>
> >
> >       /* SEQ_PACKET. */
> >       ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
> >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> >index f04abf662ec6..016ad5ff78b7 100644
> >--- a/net/vmw_vsock/af_vsock.c
> >+++ b/net/vmw_vsock/af_vsock.c
> >@@ -2129,6 +2129,30 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> >       return err;
> > }
> >
> >+static int vsock_set_rcvlowat(struct sock *sk, int val)
> >+{
> >+      const struct vsock_transport *transport;
> >+      struct vsock_sock *vsk;
> >+      int err = 0;
> >+
> >+      vsk = vsock_sk(sk);
> >+
> >+      if (val > vsk->buffer_size)
> >+              return -EINVAL;
> >+
> >+      transport = vsk->transport;
> >+
> >+      if (!transport)
> >+              return -EOPNOTSUPP;
>
> I don't know whether it is better in this case to write it in
> sk->sk_rcvlowat, maybe we can return EOPNOTSUPP only when the trasport
> is assigned and set_rcvlowat is not defined. This is because usually the
> options are set just after creation, when the transport is practically
> unassigned.
>
> I mean something like this:
>
>          if (transport) {
>                  if (transport->set_rcvlowat)
>                          return transport->set_rcvlowat(vsk, val);
>                  else
>                          return -EOPNOTSUPP;
>          }
>
>          WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>
>          return 0;

Since hv_sock implements `set_rcvlowat` to return EOPNOTSUPP. maybe we 
can just do the following:

        if (transport && transport->set_rcvlowat)
                return transport->set_rcvlowat(vsk, val);

        WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
        return 0;

That is, the default behavior is to set sk->sk_rcvlowat, but for 
transports that want a different behavior, they need to define 
set_rcvlowat() (like hv_sock).

Thanks,
Stefano

Re: [RFC PATCH v3 1/9] vsock: SO_RCVLOWAT transport set callback

[Arseniy Krasnov]

On 08.08.2022 13:30, Stefano Garzarella wrote:
> On Mon, Aug 8, 2022 at 12:23 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>>
>> On Wed, Aug 03, 2022 at 01:51:05PM +0000, Arseniy Krasnov wrote:
>>> This adds transport specific callback for SO_RCVLOWAT, because in some
>>> transports it may be difficult to know current available number of bytes
>>> ready to read. Thus, when SO_RCVLOWAT is set, transport may reject it.
>>>
>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>>> ---
>>> include/net/af_vsock.h   |  1 +
>>> net/vmw_vsock/af_vsock.c | 25 +++++++++++++++++++++++++
>>> 2 files changed, 26 insertions(+)
>>>
>>> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>>> index f742e50207fb..eae5874bae35 100644
>>> --- a/include/net/af_vsock.h
>>> +++ b/include/net/af_vsock.h
>>> @@ -134,6 +134,7 @@ struct vsock_transport {
>>>       u64 (*stream_rcvhiwat)(struct vsock_sock *);
>>>       bool (*stream_is_active)(struct vsock_sock *);
>>>       bool (*stream_allow)(u32 cid, u32 port);
>>> +      int (*set_rcvlowat)(struct vsock_sock *, int);
>>
>> checkpatch suggests to add identifier names. For some we put them in,
>> for others we didn't, but I suggest putting them in for the new ones
>> because I think it's clearer too.
>>
>> WARNING: function definition argument 'struct vsock_sock *' should also
>> have an identifier name
>> #25: FILE: include/net/af_vsock.h:137:
>> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>>
>> WARNING: function definition argument 'int' should also have an identifier name
>> #25: FILE: include/net/af_vsock.h:137:
>> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>>
>> total: 0 errors, 2 warnings, 0 checks, 44 lines checked
>>
>>>
>>>       /* SEQ_PACKET. */
>>>       ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>>> index f04abf662ec6..016ad5ff78b7 100644
>>> --- a/net/vmw_vsock/af_vsock.c
>>> +++ b/net/vmw_vsock/af_vsock.c
>>> @@ -2129,6 +2129,30 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>>>       return err;
>>> }
>>>
>>> +static int vsock_set_rcvlowat(struct sock *sk, int val)
>>> +{
>>> +      const struct vsock_transport *transport;
>>> +      struct vsock_sock *vsk;
>>> +      int err = 0;
>>> +
>>> +      vsk = vsock_sk(sk);
>>> +
>>> +      if (val > vsk->buffer_size)
>>> +              return -EINVAL;
>>> +
>>> +      transport = vsk->transport;
>>> +
>>> +      if (!transport)
>>> +              return -EOPNOTSUPP;
>>
>> I don't know whether it is better in this case to write it in
>> sk->sk_rcvlowat, maybe we can return EOPNOTSUPP only when the trasport
>> is assigned and set_rcvlowat is not defined. This is because usually the
>> options are set just after creation, when the transport is practically
>> unassigned.
>>
>> I mean something like this:
>>
>>          if (transport) {
>>                  if (transport->set_rcvlowat)
>>                          return transport->set_rcvlowat(vsk, val);
>>                  else
>>                          return -EOPNOTSUPP;
>>          }
>>
>>          WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>>
>>          return 0;
> 
> Since hv_sock implements `set_rcvlowat` to return EOPNOTSUPP. maybe we 
> can just do the following:
> 
>         if (transport && transport->set_rcvlowat)
>                 return transport->set_rcvlowat(vsk, val);
> 
>         WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>         return 0;
> 
> That is, the default behavior is to set sk->sk_rcvlowat, but for 
> transports that want a different behavior, they need to define 
> set_rcvlowat() (like hv_sock).
Hm ok, i see. I've implemented logic when non-empty transport is required, because hyperv transport
forbids to set SO_RCVLOWAT, so user needs to call this setsockopt AFTER transport is assigned(to check
that transport allows it. Not after socket creation as You mentioned above). Otherwise there is no sense
in such callback - it will be never used. Also in code above - for hyperv we will have different behavior
depends on when set_rcvlowat is called: before or after transport assignment. Is it ok?
> 
> Thanks,
> Stefano
> 

Re: [RFC PATCH v3 1/9] vsock: SO_RCVLOWAT transport set callback

[Arseniy Krasnov]

On 09.08.2022 12:37, Arseniy Krasnov wrote:
> On 08.08.2022 13:30, Stefano Garzarella wrote:
>> On Mon, Aug 8, 2022 at 12:23 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>>>
>>> On Wed, Aug 03, 2022 at 01:51:05PM +0000, Arseniy Krasnov wrote:
>>>> This adds transport specific callback for SO_RCVLOWAT, because in some
>>>> transports it may be difficult to know current available number of bytes
>>>> ready to read. Thus, when SO_RCVLOWAT is set, transport may reject it.
>>>>
>>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>>>> ---
>>>> include/net/af_vsock.h   |  1 +
>>>> net/vmw_vsock/af_vsock.c | 25 +++++++++++++++++++++++++
>>>> 2 files changed, 26 insertions(+)
>>>>
>>>> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>>>> index f742e50207fb..eae5874bae35 100644
>>>> --- a/include/net/af_vsock.h
>>>> +++ b/include/net/af_vsock.h
>>>> @@ -134,6 +134,7 @@ struct vsock_transport {
>>>>       u64 (*stream_rcvhiwat)(struct vsock_sock *);
>>>>       bool (*stream_is_active)(struct vsock_sock *);
>>>>       bool (*stream_allow)(u32 cid, u32 port);
>>>> +      int (*set_rcvlowat)(struct vsock_sock *, int);
>>>
>>> checkpatch suggests to add identifier names. For some we put them in,
>>> for others we didn't, but I suggest putting them in for the new ones
>>> because I think it's clearer too.
>>>
>>> WARNING: function definition argument 'struct vsock_sock *' should also
>>> have an identifier name
>>> #25: FILE: include/net/af_vsock.h:137:
>>> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>>>
>>> WARNING: function definition argument 'int' should also have an identifier name
>>> #25: FILE: include/net/af_vsock.h:137:
>>> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>>>
>>> total: 0 errors, 2 warnings, 0 checks, 44 lines checked
>>>
>>>>
>>>>       /* SEQ_PACKET. */
>>>>       ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
>>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>>>> index f04abf662ec6..016ad5ff78b7 100644
>>>> --- a/net/vmw_vsock/af_vsock.c
>>>> +++ b/net/vmw_vsock/af_vsock.c
>>>> @@ -2129,6 +2129,30 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>>>>       return err;
>>>> }
>>>>
>>>> +static int vsock_set_rcvlowat(struct sock *sk, int val)
>>>> +{
>>>> +      const struct vsock_transport *transport;
>>>> +      struct vsock_sock *vsk;
>>>> +      int err = 0;
>>>> +
>>>> +      vsk = vsock_sk(sk);
>>>> +
>>>> +      if (val > vsk->buffer_size)
>>>> +              return -EINVAL;
>>>> +
>>>> +      transport = vsk->transport;
>>>> +
>>>> +      if (!transport)
>>>> +              return -EOPNOTSUPP;
>>>
>>> I don't know whether it is better in this case to write it in
>>> sk->sk_rcvlowat, maybe we can return EOPNOTSUPP only when the trasport
>>> is assigned and set_rcvlowat is not defined. This is because usually the
>>> options are set just after creation, when the transport is practically
>>> unassigned.
>>>
>>> I mean something like this:
>>>
>>>          if (transport) {
>>>                  if (transport->set_rcvlowat)
>>>                          return transport->set_rcvlowat(vsk, val);
>>>                  else
>>>                          return -EOPNOTSUPP;
>>>          }
>>>
>>>          WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>>>
>>>          return 0;
>>
>> Since hv_sock implements `set_rcvlowat` to return EOPNOTSUPP. maybe we 
>> can just do the following:
>>
>>         if (transport && transport->set_rcvlowat)
>>                 return transport->set_rcvlowat(vsk, val);
>>
>>         WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>>         return 0;
>>
>> That is, the default behavior is to set sk->sk_rcvlowat, but for 
>> transports that want a different behavior, they need to define 
>> set_rcvlowat() (like hv_sock).
> Hm ok, i see. I've implemented logic when non-empty transport is required, because hyperv transport
> forbids to set SO_RCVLOWAT, so user needs to call this setsockopt AFTER transport is assigned(to check
> that transport allows it. Not after socket creation as You mentioned above). Otherwise there is no sense
> in such callback - it will be never used. Also in code above - for hyperv we will have different behavior
> depends on when set_rcvlowat is called: before or after transport assignment. Is it ok?
sorry, i mean: for hyperv, if user sets sk_rcvlowat before transport is assigned, it sees 0 - success, but in fact
hyperv transport forbids this option.
>>
>> Thanks,
>> Stefano
>>
> 

Re: [RFC PATCH v3 1/9] vsock: SO_RCVLOWAT transport set callback

[Stefano Garzarella]

On Tue, Aug 09, 2022 at 09:45:47AM +0000, Arseniy Krasnov wrote:
>On 09.08.2022 12:37, Arseniy Krasnov wrote:
>> On 08.08.2022 13:30, Stefano Garzarella wrote:
>>> On Mon, Aug 8, 2022 at 12:23 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>>>>
>>>> On Wed, Aug 03, 2022 at 01:51:05PM +0000, Arseniy Krasnov wrote:
>>>>> This adds transport specific callback for SO_RCVLOWAT, because in some
>>>>> transports it may be difficult to know current available number of bytes
>>>>> ready to read. Thus, when SO_RCVLOWAT is set, transport may reject it.
>>>>>
>>>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>>>>> ---
>>>>> include/net/af_vsock.h   |  1 +
>>>>> net/vmw_vsock/af_vsock.c | 25 +++++++++++++++++++++++++
>>>>> 2 files changed, 26 insertions(+)
>>>>>
>>>>> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>>>>> index f742e50207fb..eae5874bae35 100644
>>>>> --- a/include/net/af_vsock.h
>>>>> +++ b/include/net/af_vsock.h
>>>>> @@ -134,6 +134,7 @@ struct vsock_transport {
>>>>>       u64 (*stream_rcvhiwat)(struct vsock_sock *);
>>>>>       bool (*stream_is_active)(struct vsock_sock *);
>>>>>       bool (*stream_allow)(u32 cid, u32 port);
>>>>> +      int (*set_rcvlowat)(struct vsock_sock *, int);
>>>>
>>>> checkpatch suggests to add identifier names. For some we put them in,
>>>> for others we didn't, but I suggest putting them in for the new ones
>>>> because I think it's clearer too.
>>>>
>>>> WARNING: function definition argument 'struct vsock_sock *' should also
>>>> have an identifier name
>>>> #25: FILE: include/net/af_vsock.h:137:
>>>> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>>>>
>>>> WARNING: function definition argument 'int' should also have an identifier name
>>>> #25: FILE: include/net/af_vsock.h:137:
>>>> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>>>>
>>>> total: 0 errors, 2 warnings, 0 checks, 44 lines checked
>>>>
>>>>>
>>>>>       /* SEQ_PACKET. */
>>>>>       ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
>>>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>>>>> index f04abf662ec6..016ad5ff78b7 100644
>>>>> --- a/net/vmw_vsock/af_vsock.c
>>>>> +++ b/net/vmw_vsock/af_vsock.c
>>>>> @@ -2129,6 +2129,30 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>>>>>       return err;
>>>>> }
>>>>>
>>>>> +static int vsock_set_rcvlowat(struct sock *sk, int val)
>>>>> +{
>>>>> +      const struct vsock_transport *transport;
>>>>> +      struct vsock_sock *vsk;
>>>>> +      int err = 0;
>>>>> +
>>>>> +      vsk = vsock_sk(sk);
>>>>> +
>>>>> +      if (val > vsk->buffer_size)
>>>>> +              return -EINVAL;
>>>>> +
>>>>> +      transport = vsk->transport;
>>>>> +
>>>>> +      if (!transport)
>>>>> +              return -EOPNOTSUPP;
>>>>
>>>> I don't know whether it is better in this case to write it in
>>>> sk->sk_rcvlowat, maybe we can return EOPNOTSUPP only when the trasport
>>>> is assigned and set_rcvlowat is not defined. This is because usually the
>>>> options are set just after creation, when the transport is practically
>>>> unassigned.
>>>>
>>>> I mean something like this:
>>>>
>>>>          if (transport) {
>>>>                  if (transport->set_rcvlowat)
>>>>                          return transport->set_rcvlowat(vsk, val);
>>>>                  else
>>>>                          return -EOPNOTSUPP;
>>>>          }
>>>>
>>>>          WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>>>>
>>>>          return 0;
>>>
>>> Since hv_sock implements `set_rcvlowat` to return EOPNOTSUPP. maybe we
>>> can just do the following:
>>>
>>>         if (transport && transport->set_rcvlowat)
>>>                 return transport->set_rcvlowat(vsk, val);
>>>
>>>         WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>>>         return 0;
>>>
>>> That is, the default behavior is to set sk->sk_rcvlowat, but for
>>> transports that want a different behavior, they need to define
>>> set_rcvlowat() (like hv_sock).
>> Hm ok, i see. I've implemented logic when non-empty transport is required, because hyperv transport
>> forbids to set SO_RCVLOWAT, so user needs to call this setsockopt AFTER transport is assigned(to check
>> that transport allows it. Not after socket creation as You mentioned above). Otherwise there is no sense
>> in such callback - it will be never used. Also in code above - for hyperv we will have different behavior
>> depends on when set_rcvlowat is called: before or after transport assignment. Is it ok?
>sorry, i mean: for hyperv, if user sets sk_rcvlowat before transport is assigned, it sees 0 - success, but in fact
>hyperv transport forbids this option.

I see, but I think it's better to set it and not respect in hyperv (as 
we've practically done until now with all transports) than to prevent 
the setting until we assign a transport.

At most when we use hyperv anyway we get notified per byte, so we should 
just get more notifications than we expect.

Thanks,
Stefano

Re: [RFC PATCH v3 1/9] vsock: SO_RCVLOWAT transport set callback

[Arseniy Krasnov]

On 09.08.2022 13:03, Stefano Garzarella wrote:
> On Tue, Aug 09, 2022 at 09:45:47AM +0000, Arseniy Krasnov wrote:
>> On 09.08.2022 12:37, Arseniy Krasnov wrote:
>>> On 08.08.2022 13:30, Stefano Garzarella wrote:
>>>> On Mon, Aug 8, 2022 at 12:23 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>>>>>
>>>>> On Wed, Aug 03, 2022 at 01:51:05PM +0000, Arseniy Krasnov wrote:
>>>>>> This adds transport specific callback for SO_RCVLOWAT, because in some
>>>>>> transports it may be difficult to know current available number of bytes
>>>>>> ready to read. Thus, when SO_RCVLOWAT is set, transport may reject it.
>>>>>>
>>>>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>>>>>> ---
>>>>>> include/net/af_vsock.h   |  1 +
>>>>>> net/vmw_vsock/af_vsock.c | 25 +++++++++++++++++++++++++
>>>>>> 2 files changed, 26 insertions(+)
>>>>>>
>>>>>> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>>>>>> index f742e50207fb..eae5874bae35 100644
>>>>>> --- a/include/net/af_vsock.h
>>>>>> +++ b/include/net/af_vsock.h
>>>>>> @@ -134,6 +134,7 @@ struct vsock_transport {
>>>>>>       u64 (*stream_rcvhiwat)(struct vsock_sock *);
>>>>>>       bool (*stream_is_active)(struct vsock_sock *);
>>>>>>       bool (*stream_allow)(u32 cid, u32 port);
>>>>>> +      int (*set_rcvlowat)(struct vsock_sock *, int);
>>>>>
>>>>> checkpatch suggests to add identifier names. For some we put them in,
>>>>> for others we didn't, but I suggest putting them in for the new ones
>>>>> because I think it's clearer too.
>>>>>
>>>>> WARNING: function definition argument 'struct vsock_sock *' should also
>>>>> have an identifier name
>>>>> #25: FILE: include/net/af_vsock.h:137:
>>>>> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>>>>>
>>>>> WARNING: function definition argument 'int' should also have an identifier name
>>>>> #25: FILE: include/net/af_vsock.h:137:
>>>>> +       int (*set_rcvlowat)(struct vsock_sock *, int);
>>>>>
>>>>> total: 0 errors, 2 warnings, 0 checks, 44 lines checked
>>>>>
>>>>>>
>>>>>>       /* SEQ_PACKET. */
>>>>>>       ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
>>>>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>>>>>> index f04abf662ec6..016ad5ff78b7 100644
>>>>>> --- a/net/vmw_vsock/af_vsock.c
>>>>>> +++ b/net/vmw_vsock/af_vsock.c
>>>>>> @@ -2129,6 +2129,30 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>>>>>>       return err;
>>>>>> }
>>>>>>
>>>>>> +static int vsock_set_rcvlowat(struct sock *sk, int val)
>>>>>> +{
>>>>>> +      const struct vsock_transport *transport;
>>>>>> +      struct vsock_sock *vsk;
>>>>>> +      int err = 0;
>>>>>> +
>>>>>> +      vsk = vsock_sk(sk);
>>>>>> +
>>>>>> +      if (val > vsk->buffer_size)
>>>>>> +              return -EINVAL;
>>>>>> +
>>>>>> +      transport = vsk->transport;
>>>>>> +
>>>>>> +      if (!transport)
>>>>>> +              return -EOPNOTSUPP;
>>>>>
>>>>> I don't know whether it is better in this case to write it in
>>>>> sk->sk_rcvlowat, maybe we can return EOPNOTSUPP only when the trasport
>>>>> is assigned and set_rcvlowat is not defined. This is because usually the
>>>>> options are set just after creation, when the transport is practically
>>>>> unassigned.
>>>>>
>>>>> I mean something like this:
>>>>>
>>>>>          if (transport) {
>>>>>                  if (transport->set_rcvlowat)
>>>>>                          return transport->set_rcvlowat(vsk, val);
>>>>>                  else
>>>>>                          return -EOPNOTSUPP;
>>>>>          }
>>>>>
>>>>>          WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>>>>>
>>>>>          return 0;
>>>>
>>>> Since hv_sock implements `set_rcvlowat` to return EOPNOTSUPP. maybe we
>>>> can just do the following:
>>>>
>>>>         if (transport && transport->set_rcvlowat)
>>>>                 return transport->set_rcvlowat(vsk, val);
>>>>
>>>>         WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
>>>>         return 0;
>>>>
>>>> That is, the default behavior is to set sk->sk_rcvlowat, but for
>>>> transports that want a different behavior, they need to define
>>>> set_rcvlowat() (like hv_sock).
>>> Hm ok, i see. I've implemented logic when non-empty transport is required, because hyperv transport
>>> forbids to set SO_RCVLOWAT, so user needs to call this setsockopt AFTER transport is assigned(to check
>>> that transport allows it. Not after socket creation as You mentioned above). Otherwise there is no sense
>>> in such callback - it will be never used. Also in code above - for hyperv we will have different behavior
>>> depends on when set_rcvlowat is called: before or after transport assignment. Is it ok?
>> sorry, i mean: for hyperv, if user sets sk_rcvlowat before transport is assigned, it sees 0 - success, but in fact
>> hyperv transport forbids this option.
> 
> I see, but I think it's better to set it and not respect in hyperv (as we've practically done until now with all transports) than to prevent the setting until we assign a transport.
> 
> At most when we use hyperv anyway we get notified per byte, so we should just get more notifications than we expect.
see it, ok, thanks
> 
> Thanks,
> Stefano
> 

[RFC PATCH v3 2/9] hv_sock: disable SO_RCVLOWAT support

[Arseniy Krasnov]

For Hyper-V it is quiet difficult to support this socket option,due to
transport internals, so disable it.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
---
 net/vmw_vsock/hyperv_transport.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
index e111e13b6660..5fab8f356a86 100644
--- a/net/vmw_vsock/hyperv_transport.c
+++ b/net/vmw_vsock/hyperv_transport.c
@@ -802,6 +802,12 @@ int hvs_notify_send_post_enqueue(struct vsock_sock *vsk, ssize_t written,
 	return 0;
 }
 
+static
+int hvs_set_rcvlowat(struct vsock_sock *vsk, int val)
+{
+	return -EOPNOTSUPP;
+}
+
 static struct vsock_transport hvs_transport = {
 	.module                   = THIS_MODULE,
 
@@ -837,6 +843,7 @@ static struct vsock_transport hvs_transport = {
 	.notify_send_pre_enqueue  = hvs_notify_send_pre_enqueue,
 	.notify_send_post_enqueue = hvs_notify_send_post_enqueue,
 
+	.set_rcvlowat             = hvs_set_rcvlowat
 };
 
 static bool hvs_check_transport(struct vsock_sock *vsk)
-- 
2.25.1

Re: [RFC PATCH v3 2/9] hv_sock: disable SO_RCVLOWAT support

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 01:53:23PM +0000, Arseniy Krasnov wrote:
>For Hyper-V it is quiet difficult to support this socket option,due to
>transport internals, so disable it.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>Reviewed-by: Dexuan Cui <decui@microsoft.com>
>---
> net/vmw_vsock/hyperv_transport.c | 7 +++++++
> 1 file changed, 7 insertions(+)

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

[RFC PATCH v3 3/9] virtio/vsock: use 'target' in notify_poll_in callback

[Arseniy Krasnov]

This callback controls setting of POLLIN,POLLRDNORM output bits of poll()
syscall,but in some cases,it is incorrectly to set it, when socket has
at least 1 bytes of available data. Use 'target' which is already exists
and equal to sk_rcvlowat in this case.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 net/vmw_vsock/virtio_transport_common.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index ec2c2afbf0d0..8f6356ebcdd1 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -634,10 +634,7 @@ virtio_transport_notify_poll_in(struct vsock_sock *vsk,
 				size_t target,
 				bool *data_ready_now)
 {
-	if (vsock_stream_has_data(vsk))
-		*data_ready_now = true;
-	else
-		*data_ready_now = false;
+	*data_ready_now = vsock_stream_has_data(vsk) >= target;
 
 	return 0;
 }
-- 
2.25.1

Re: [RFC PATCH v3 3/9] virtio/vsock: use 'target' in notify_poll_in callback

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 01:55:36PM +0000, Arseniy Krasnov wrote:
>This callback controls setting of POLLIN,POLLRDNORM output bits of poll()
>syscall,but in some cases,it is incorrectly to set it, when socket has
>at least 1 bytes of available data. Use 'target' which is already exists
>and equal to sk_rcvlowat in this case.

Little suggestion:
We should update the commit description, since so far 'target' is not 
equal to sk_rcvlowat.

With that fixed (and adding some spaces after the commas):

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/virtio_transport_common.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index ec2c2afbf0d0..8f6356ebcdd1 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -634,10 +634,7 @@ virtio_transport_notify_poll_in(struct vsock_sock *vsk,
> 				size_t target,
> 				bool *data_ready_now)
> {
>-	if (vsock_stream_has_data(vsk))
>-		*data_ready_now = true;
>-	else
>-		*data_ready_now = false;
>+	*data_ready_now = vsock_stream_has_data(vsk) >= target;
>
> 	return 0;
> }
>-- 
>2.25.1

[RFC PATCH v3 4/9] vmci/vsock: use 'target' in notify_poll_in callback

[Arseniy Krasnov]

This callback controls setting of POLLIN,POLLRDNORM output bits of poll()
syscall,but in some cases,it is incorrectly to set it, when socket has
at least 1 bytes of available data. Use 'target' which is already exists
and equal to sk_rcvlowat in this case.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 net/vmw_vsock/vmci_transport_notify.c        | 8 ++++----
 net/vmw_vsock/vmci_transport_notify_qstate.c | 8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/vmw_vsock/vmci_transport_notify.c b/net/vmw_vsock/vmci_transport_notify.c
index d69fc4b595ad..852097e2b9e6 100644
--- a/net/vmw_vsock/vmci_transport_notify.c
+++ b/net/vmw_vsock/vmci_transport_notify.c
@@ -340,12 +340,12 @@ vmci_transport_notify_pkt_poll_in(struct sock *sk,
 {
 	struct vsock_sock *vsk = vsock_sk(sk);
 
-	if (vsock_stream_has_data(vsk)) {
+	if (vsock_stream_has_data(vsk) >= target) {
 		*data_ready_now = true;
 	} else {
-		/* We can't read right now because there is nothing in the
-		 * queue. Ask for notifications when there is something to
-		 * read.
+		/* We can't read right now because there is not enough data
+		 * in the queue. Ask for notifications when there is something
+		 * to read.
 		 */
 		if (sk->sk_state == TCP_ESTABLISHED) {
 			if (!send_waiting_read(sk, 1))
diff --git a/net/vmw_vsock/vmci_transport_notify_qstate.c b/net/vmw_vsock/vmci_transport_notify_qstate.c
index 0f36d7c45db3..12f0cb8fe998 100644
--- a/net/vmw_vsock/vmci_transport_notify_qstate.c
+++ b/net/vmw_vsock/vmci_transport_notify_qstate.c
@@ -161,12 +161,12 @@ vmci_transport_notify_pkt_poll_in(struct sock *sk,
 {
 	struct vsock_sock *vsk = vsock_sk(sk);
 
-	if (vsock_stream_has_data(vsk)) {
+	if (vsock_stream_has_data(vsk) >= target) {
 		*data_ready_now = true;
 	} else {
-		/* We can't read right now because there is nothing in the
-		 * queue. Ask for notifications when there is something to
-		 * read.
+		/* We can't read right now because there is not enough data
+		 * in the queue. Ask for notifications when there is something
+		 * to read.
 		 */
 		if (sk->sk_state == TCP_ESTABLISHED)
 			vsock_block_update_write_window(sk);
-- 
2.25.1

Re: [RFC PATCH v3 4/9] vmci/vsock: use 'target' in notify_poll_in callback

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 01:57:54PM +0000, Arseniy Krasnov wrote:
>This callback controls setting of POLLIN,POLLRDNORM output bits of poll()
>syscall,but in some cases,it is incorrectly to set it, when socket has
>at least 1 bytes of available data. Use 'target' which is already exists
>and equal to sk_rcvlowat in this case.

Ditto as the previous patch.
With that fixed:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

@Bryan, @Vishnu, if you're happy with this change, can you ack/review?

Thanks,
Stefano

>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/vmci_transport_notify.c        | 8 ++++----
> net/vmw_vsock/vmci_transport_notify_qstate.c | 8 ++++----
> 2 files changed, 8 insertions(+), 8 deletions(-)
>
>diff --git a/net/vmw_vsock/vmci_transport_notify.c b/net/vmw_vsock/vmci_transport_notify.c
>index d69fc4b595ad..852097e2b9e6 100644
>--- a/net/vmw_vsock/vmci_transport_notify.c
>+++ b/net/vmw_vsock/vmci_transport_notify.c
>@@ -340,12 +340,12 @@ vmci_transport_notify_pkt_poll_in(struct sock *sk,
> {
> 	struct vsock_sock *vsk = vsock_sk(sk);
>
>-	if (vsock_stream_has_data(vsk)) {
>+	if (vsock_stream_has_data(vsk) >= target) {
> 		*data_ready_now = true;
> 	} else {
>-		/* We can't read right now because there is nothing in the
>-		 * queue. Ask for notifications when there is something to
>-		 * read.
>+		/* We can't read right now because there is not enough data
>+		 * in the queue. Ask for notifications when there is something
>+		 * to read.
> 		 */
> 		if (sk->sk_state == TCP_ESTABLISHED) {
> 			if (!send_waiting_read(sk, 1))
>diff --git a/net/vmw_vsock/vmci_transport_notify_qstate.c b/net/vmw_vsock/vmci_transport_notify_qstate.c
>index 0f36d7c45db3..12f0cb8fe998 100644
>--- a/net/vmw_vsock/vmci_transport_notify_qstate.c
>+++ b/net/vmw_vsock/vmci_transport_notify_qstate.c
>@@ -161,12 +161,12 @@ vmci_transport_notify_pkt_poll_in(struct sock *sk,
> {
> 	struct vsock_sock *vsk = vsock_sk(sk);
>
>-	if (vsock_stream_has_data(vsk)) {
>+	if (vsock_stream_has_data(vsk) >= target) {
> 		*data_ready_now = true;
> 	} else {
>-		/* We can't read right now because there is nothing in the
>-		 * queue. Ask for notifications when there is something to
>-		 * read.
>+		/* We can't read right now because there is not enough data
>+		 * in the queue. Ask for notifications when there is something
>+		 * to read.
> 		 */
> 		if (sk->sk_state == TCP_ESTABLISHED)
> 			vsock_block_update_write_window(sk);
>-- 
>2.25.1

Re: [RFC PATCH v3 4/9] vmci/vsock: use 'target' in notify_poll_in callback

[Vishnu Dasa]

> On Aug 8, 2022, at 3:36 AM, Stefano Garzarella <sgarzare@redhat.com> wrote:
> 
> On Wed, Aug 03, 2022 at 01:57:54PM +0000, Arseniy Krasnov wrote:
>> This callback controls setting of POLLIN,POLLRDNORM output bits of poll()
>> syscall,but in some cases,it is incorrectly to set it, when socket has
>> at least 1 bytes of available data. Use 'target' which is already exists
>> and equal to sk_rcvlowat in this case.
> 
> Ditto as the previous patch.
> With that fixed:
> 
> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
> 
> @Bryan, @Vishnu, if you're happy with this change, can you ack/review?

This patch looks good to me.

Thank you, Arseniy for running the test with VMCI.  I also ran some of
our internal tests successfully with this patch series.

> Thanks,
> Stefano
> 
>> 
>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>

Reviewed-by: Vishnu Dasa <vdasa@vmware.com>

>> ---
>> net/vmw_vsock/vmci_transport_notify.c        | 8 ++++----
>> net/vmw_vsock/vmci_transport_notify_qstate.c | 8 ++++----
>> 2 files changed, 8 insertions(+), 8 deletions(-)
>> 
>> diff --git a/net/vmw_vsock/vmci_transport_notify.c b/net/vmw_vsock/vmci_transport_notify.c
>> index d69fc4b595ad..852097e2b9e6 100644
>> --- a/net/vmw_vsock/vmci_transport_notify.c
>> +++ b/net/vmw_vsock/vmci_transport_notify.c
>> @@ -340,12 +340,12 @@ vmci_transport_notify_pkt_poll_in(struct sock *sk,
>> {
>>      struct vsock_sock *vsk = vsock_sk(sk);
>> 
>> -      if (vsock_stream_has_data(vsk)) {
>> +      if (vsock_stream_has_data(vsk) >= target) {
>>              *data_ready_now = true;
>>      } else {
>> -              /* We can't read right now because there is nothing in the
>> -               * queue. Ask for notifications when there is something to
>> -               * read.
>> +              /* We can't read right now because there is not enough data
>> +               * in the queue. Ask for notifications when there is something
>> +               * to read.
>>               */
>>              if (sk->sk_state == TCP_ESTABLISHED) {
>>                      if (!send_waiting_read(sk, 1))
>> diff --git a/net/vmw_vsock/vmci_transport_notify_qstate.c b/net/vmw_vsock/vmci_transport_notify_qstate.c
>> index 0f36d7c45db3..12f0cb8fe998 100644
>> --- a/net/vmw_vsock/vmci_transport_notify_qstate.c
>> +++ b/net/vmw_vsock/vmci_transport_notify_qstate.c
>> @@ -161,12 +161,12 @@ vmci_transport_notify_pkt_poll_in(struct sock *sk,
>> {
>>      struct vsock_sock *vsk = vsock_sk(sk);
>> 
>> -      if (vsock_stream_has_data(vsk)) {
>> +      if (vsock_stream_has_data(vsk) >= target) {
>>              *data_ready_now = true;
>>      } else {
>> -              /* We can't read right now because there is nothing in the
>> -               * queue. Ask for notifications when there is something to
>> -               * read.
>> +              /* We can't read right now because there is not enough data
>> +               * in the queue. Ask for notifications when there is something
>> +               * to read.
>>               */
>>              if (sk->sk_state == TCP_ESTABLISHED)
>>                      vsock_block_update_write_window(sk);
>> --
>> 2.25.1

[RFC PATCH v3 5/9] vsock: pass sock_rcvlowat to notify_poll_in as target

[Arseniy Krasnov]

This callback controls setting of POLLIN,POLLRDNORM output bits of poll()
syscall,but in some cases,it is incorrectly to set it, when socket has
at least 1 bytes of available data.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 net/vmw_vsock/af_vsock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 016ad5ff78b7..3a1426eb8baa 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1066,8 +1066,9 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
 		if (transport && transport->stream_is_active(vsk) &&
 		    !(sk->sk_shutdown & RCV_SHUTDOWN)) {
 			bool data_ready_now = false;
+			int target = sock_rcvlowat(sk, 0, INT_MAX);
 			int ret = transport->notify_poll_in(
-					vsk, 1, &data_ready_now);
+					vsk, target, &data_ready_now);
 			if (ret < 0) {
 				mask |= EPOLLERR;
 			} else {
-- 
2.25.1

Re: [RFC PATCH v3 5/9] vsock: pass sock_rcvlowat to notify_poll_in as target

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 01:59:49PM +0000, Arseniy Krasnov wrote:
>This callback controls setting of POLLIN,POLLRDNORM output bits of poll()
>syscall,but in some cases,it is incorrectly to set it, when socket has
>at least 1 bytes of available data.

I suggest you refrase the description a bit, which should describe what 
was the problem and what the patch does, so I was thinking something 
like this:

   Passing 1 as the target to notify_poll_in(), we don't honor
   what the user has set via SO_RCVLOWAT, going to set POLLIN
   and POLLRDNORM, even if we don't have the amount of bytes
   expected by the user.

   Let's use sock_rcvlowat() to get the right target to pass to
   notify_poll_in().

Anyway, the patch LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/af_vsock.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 016ad5ff78b7..3a1426eb8baa 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1066,8 +1066,9 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
> 		if (transport && transport->stream_is_active(vsk) &&
> 		    !(sk->sk_shutdown & RCV_SHUTDOWN)) {
> 			bool data_ready_now = false;
>+			int target = sock_rcvlowat(sk, 0, INT_MAX);
> 			int ret = transport->notify_poll_in(
>-					vsk, 1, &data_ready_now);
>+					vsk, target, &data_ready_now);
> 			if (ret < 0) {
> 				mask |= EPOLLERR;
> 			} else {
>-- 
>2.25.1

[RFC PATCH v3 6/9] vsock: add API call for data ready

[Arseniy Krasnov]

This adds 'vsock_data_ready()' which must be called by transport to kick
sleeping data readers. It checks for SO_RCVLOWAT value before waking
user,thus preventing spurious wake ups.Based on 'tcp_data_ready()' logic.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 include/net/af_vsock.h   |  1 +
 net/vmw_vsock/af_vsock.c | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index eae5874bae35..7b79fc5164cc 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -77,6 +77,7 @@ struct vsock_sock {
 s64 vsock_stream_has_data(struct vsock_sock *vsk);
 s64 vsock_stream_has_space(struct vsock_sock *vsk);
 struct sock *vsock_create_connected(struct sock *parent);
+void vsock_data_ready(struct sock *sk);
 
 /**** TRANSPORT ****/
 
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 3a1426eb8baa..47e80a7cbbdf 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -882,6 +882,16 @@ s64 vsock_stream_has_space(struct vsock_sock *vsk)
 }
 EXPORT_SYMBOL_GPL(vsock_stream_has_space);
 
+void vsock_data_ready(struct sock *sk)
+{
+	struct vsock_sock *vsk = vsock_sk(sk);
+
+	if (vsock_stream_has_data(vsk) >= sk->sk_rcvlowat ||
+	    sock_flag(sk, SOCK_DONE))
+		sk->sk_data_ready(sk);
+}
+EXPORT_SYMBOL_GPL(vsock_data_ready);
+
 static int vsock_release(struct socket *sock)
 {
 	__vsock_release(sock->sk, 0);
-- 
2.25.1

Re: [RFC PATCH v3 6/9] vsock: add API call for data ready

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 02:01:57PM +0000, Arseniy Krasnov wrote:
>This adds 'vsock_data_ready()' which must be called by transport to kick
>sleeping data readers. It checks for SO_RCVLOWAT value before waking
>user,thus preventing spurious wake ups.Based on 'tcp_data_ready()' logic.
>

Since it's an RFC, I suggest you add a space after the punctuation. :-)

The patch LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> include/net/af_vsock.h   |  1 +
> net/vmw_vsock/af_vsock.c | 10 ++++++++++
> 2 files changed, 11 insertions(+)
>
>diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>index eae5874bae35..7b79fc5164cc 100644
>--- a/include/net/af_vsock.h
>+++ b/include/net/af_vsock.h
>@@ -77,6 +77,7 @@ struct vsock_sock {
> s64 vsock_stream_has_data(struct vsock_sock *vsk);
> s64 vsock_stream_has_space(struct vsock_sock *vsk);
> struct sock *vsock_create_connected(struct sock *parent);
>+void vsock_data_ready(struct sock *sk);
>
> /**** TRANSPORT ****/
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 3a1426eb8baa..47e80a7cbbdf 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -882,6 +882,16 @@ s64 vsock_stream_has_space(struct vsock_sock *vsk)
> }
> EXPORT_SYMBOL_GPL(vsock_stream_has_space);
>
>+void vsock_data_ready(struct sock *sk)
>+{
>+	struct vsock_sock *vsk = vsock_sk(sk);
>+
>+	if (vsock_stream_has_data(vsk) >= sk->sk_rcvlowat ||
>+	    sock_flag(sk, SOCK_DONE))
>+		sk->sk_data_ready(sk);
>+}
>+EXPORT_SYMBOL_GPL(vsock_data_ready);
>+
> static int vsock_release(struct socket *sock)
> {
> 	__vsock_release(sock->sk, 0);
>-- 
>2.25.1

[RFC PATCH v3 7/9] virtio/vsock: check SO_RCVLOWAT before wake up reader

[Arseniy Krasnov]

This adds extra condition to wake up data reader: do it only when number
of readable bytes >= SO_RCVLOWAT. Otherwise, there is no sense to kick
user,because it will wait until SO_RCVLOWAT bytes will be dequeued.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 net/vmw_vsock/virtio_transport_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 8f6356ebcdd1..35863132f4f1 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1081,7 +1081,7 @@ virtio_transport_recv_connected(struct sock *sk,
 	switch (le16_to_cpu(pkt->hdr.op)) {
 	case VIRTIO_VSOCK_OP_RW:
 		virtio_transport_recv_enqueue(vsk, pkt);
-		sk->sk_data_ready(sk);
+		vsock_data_ready(sk);
 		return err;
 	case VIRTIO_VSOCK_OP_CREDIT_REQUEST:
 		virtio_transport_send_credit_update(vsk);
-- 
2.25.1

Re: [RFC PATCH v3 7/9] virtio/vsock: check SO_RCVLOWAT before wake up reader

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 02:03:58PM +0000, Arseniy Krasnov wrote:
>This adds extra condition to wake up data reader: do it only when number
>of readable bytes >= SO_RCVLOWAT. Otherwise, there is no sense to kick
>user,because it will wait until SO_RCVLOWAT bytes will be dequeued.

Maybe we can mention that these are done in vsock_data_ready().

Anyway, the patch LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/virtio_transport_common.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 8f6356ebcdd1..35863132f4f1 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -1081,7 +1081,7 @@ virtio_transport_recv_connected(struct sock *sk,
> 	switch (le16_to_cpu(pkt->hdr.op)) {
> 	case VIRTIO_VSOCK_OP_RW:
> 		virtio_transport_recv_enqueue(vsk, pkt);
>-		sk->sk_data_ready(sk);
>+		vsock_data_ready(sk);
> 		return err;
> 	case VIRTIO_VSOCK_OP_CREDIT_REQUEST:
> 		virtio_transport_send_credit_update(vsk);
>-- 
>2.25.1

[RFC PATCH v3 8/9] vmci/vsock: check SO_RCVLOWAT before wake up reader

[Arseniy Krasnov]

This adds extra condition to wake up data reader: do it only when number
of readable bytes >= SO_RCVLOWAT. Otherwise, there is no sense to kick
user,because it will wait until SO_RCVLOWAT bytes will be dequeued.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 net/vmw_vsock/vmci_transport_notify.c        | 2 +-
 net/vmw_vsock/vmci_transport_notify_qstate.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/vmw_vsock/vmci_transport_notify.c b/net/vmw_vsock/vmci_transport_notify.c
index 852097e2b9e6..7c3a7db134b2 100644
--- a/net/vmw_vsock/vmci_transport_notify.c
+++ b/net/vmw_vsock/vmci_transport_notify.c
@@ -307,7 +307,7 @@ vmci_transport_handle_wrote(struct sock *sk,
 	struct vsock_sock *vsk = vsock_sk(sk);
 	PKT_FIELD(vsk, sent_waiting_read) = false;
 #endif
-	sk->sk_data_ready(sk);
+	vsock_data_ready(sk);
 }
 
 static void vmci_transport_notify_pkt_socket_init(struct sock *sk)
diff --git a/net/vmw_vsock/vmci_transport_notify_qstate.c b/net/vmw_vsock/vmci_transport_notify_qstate.c
index 12f0cb8fe998..e96a88d850a8 100644
--- a/net/vmw_vsock/vmci_transport_notify_qstate.c
+++ b/net/vmw_vsock/vmci_transport_notify_qstate.c
@@ -84,7 +84,7 @@ vmci_transport_handle_wrote(struct sock *sk,
 			    bool bottom_half,
 			    struct sockaddr_vm *dst, struct sockaddr_vm *src)
 {
-	sk->sk_data_ready(sk);
+	vsock_data_ready(sk);
 }
 
 static void vsock_block_update_write_window(struct sock *sk)
@@ -282,7 +282,7 @@ vmci_transport_notify_pkt_recv_post_dequeue(
 		/* See the comment in
 		 * vmci_transport_notify_pkt_send_post_enqueue().
 		 */
-		sk->sk_data_ready(sk);
+		vsock_data_ready(sk);
 	}
 
 	return err;
-- 
2.25.1

Re: [RFC PATCH v3 8/9] vmci/vsock: check SO_RCVLOWAT before wake up reader

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 02:05:52PM +0000, Arseniy Krasnov wrote:
>This adds extra condition to wake up data reader: do it only when number
>of readable bytes >= SO_RCVLOWAT. Otherwise, there is no sense to kick
>user,because it will wait until SO_RCVLOWAT bytes will be dequeued.

Ditto as previous patch.

@Bryan, @Vishnu, plaese, can you review/ack also this patch?

Thanks,
Stefano

>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/vmci_transport_notify.c        | 2 +-
> net/vmw_vsock/vmci_transport_notify_qstate.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/net/vmw_vsock/vmci_transport_notify.c b/net/vmw_vsock/vmci_transport_notify.c
>index 852097e2b9e6..7c3a7db134b2 100644
>--- a/net/vmw_vsock/vmci_transport_notify.c
>+++ b/net/vmw_vsock/vmci_transport_notify.c
>@@ -307,7 +307,7 @@ vmci_transport_handle_wrote(struct sock *sk,
> 	struct vsock_sock *vsk = vsock_sk(sk);
> 	PKT_FIELD(vsk, sent_waiting_read) = false;
> #endif
>-	sk->sk_data_ready(sk);
>+	vsock_data_ready(sk);
> }
>
> static void vmci_transport_notify_pkt_socket_init(struct sock *sk)
>diff --git a/net/vmw_vsock/vmci_transport_notify_qstate.c b/net/vmw_vsock/vmci_transport_notify_qstate.c
>index 12f0cb8fe998..e96a88d850a8 100644
>--- a/net/vmw_vsock/vmci_transport_notify_qstate.c
>+++ b/net/vmw_vsock/vmci_transport_notify_qstate.c
>@@ -84,7 +84,7 @@ vmci_transport_handle_wrote(struct sock *sk,
> 			    bool bottom_half,
> 			    struct sockaddr_vm *dst, struct sockaddr_vm *src)
> {
>-	sk->sk_data_ready(sk);
>+	vsock_data_ready(sk);
> }
>
> static void vsock_block_update_write_window(struct sock *sk)
>@@ -282,7 +282,7 @@ vmci_transport_notify_pkt_recv_post_dequeue(
> 		/* See the comment in
> 		 * vmci_transport_notify_pkt_send_post_enqueue().
> 		 */
>-		sk->sk_data_ready(sk);
>+		vsock_data_ready(sk);
> 	}
>
> 	return err;
>-- 
>2.25.1

Re: [RFC PATCH v3 8/9] vmci/vsock: check SO_RCVLOWAT before wake up reader

[Vishnu Dasa]

> On Aug 8, 2022, at 4:01 AM, Stefano Garzarella <sgarzare@redhat.com> wrote:
> 
> On Wed, Aug 03, 2022 at 02:05:52PM +0000, Arseniy Krasnov wrote:
>> This adds extra condition to wake up data reader: do it only when number
>> of readable bytes >= SO_RCVLOWAT. Otherwise, there is no sense to kick
>> user,because it will wait until SO_RCVLOWAT bytes will be dequeued.

Nit: add space after comma.

> Ditto as previous patch.
> 
> @Bryan, @Vishnu, plaese, can you review/ack also this patch?

This patch looks good to me.

Thank you, Arseniy for running the new test with VMCI.  I also ran some
of our internal tests successfully with this patch series.

> Thanks,
> Stefano
> 
>> 
>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>

Reviewed-by: Vishnu Dasa <vdasa@vmware.com>

>> ---
>> net/vmw_vsock/vmci_transport_notify.c        | 2 +-
>> net/vmw_vsock/vmci_transport_notify_qstate.c | 4 ++--
>> 2 files changed, 3 insertions(+), 3 deletions(-)
>> 
>> diff --git a/net/vmw_vsock/vmci_transport_notify.c b/net/vmw_vsock/vmci_transport_notify.c
>> index 852097e2b9e6..7c3a7db134b2 100644
>> --- a/net/vmw_vsock/vmci_transport_notify.c
>> +++ b/net/vmw_vsock/vmci_transport_notify.c
>> @@ -307,7 +307,7 @@ vmci_transport_handle_wrote(struct sock *sk,
>>      struct vsock_sock *vsk = vsock_sk(sk);
>>      PKT_FIELD(vsk, sent_waiting_read) = false;
>> #endif
>> -      sk->sk_data_ready(sk);
>> +      vsock_data_ready(sk);
>> }
>> 
>> static void vmci_transport_notify_pkt_socket_init(struct sock *sk)
>> diff --git a/net/vmw_vsock/vmci_transport_notify_qstate.c b/net/vmw_vsock/vmci_transport_notify_qstate.c
>> index 12f0cb8fe998..e96a88d850a8 100644
>> --- a/net/vmw_vsock/vmci_transport_notify_qstate.c
>> +++ b/net/vmw_vsock/vmci_transport_notify_qstate.c
>> @@ -84,7 +84,7 @@ vmci_transport_handle_wrote(struct sock *sk,
>>                          bool bottom_half,
>>                          struct sockaddr_vm *dst, struct sockaddr_vm *src)
>> {
>> -      sk->sk_data_ready(sk);
>> +      vsock_data_ready(sk);
>> }
>> 
>> static void vsock_block_update_write_window(struct sock *sk)
>> @@ -282,7 +282,7 @@ vmci_transport_notify_pkt_recv_post_dequeue(
>>              /* See the comment in
>>               * vmci_transport_notify_pkt_send_post_enqueue().
>>               */
>> -              sk->sk_data_ready(sk);
>> +              vsock_data_ready(sk);
>>      }
>> 
>>      return err;
>> --
>> 2.25.1

[RFC PATCH v3 9/9] vsock_test: POLLIN + SO_RCVLOWAT test

[Arseniy Krasnov]

This adds test to check,that when poll() returns POLLIN,POLLRDNORM bits,
next read call won't block.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 tools/testing/vsock/vsock_test.c | 107 +++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)

diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index dc577461afc2..920dc5d5d979 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -18,6 +18,7 @@
 #include <sys/socket.h>
 #include <time.h>
 #include <sys/mman.h>
+#include <poll.h>
 
 #include "timeout.h"
 #include "control.h"
@@ -596,6 +597,107 @@ static void test_seqpacket_invalid_rec_buffer_server(const struct test_opts *opt
 	close(fd);
 }
 
+static void test_stream_poll_rcvlowat_server(const struct test_opts *opts)
+{
+#define RCVLOWAT_BUF_SIZE 128
+	int fd;
+	int i;
+
+	fd = vsock_stream_accept(VMADDR_CID_ANY, 1234, NULL);
+	if (fd < 0) {
+		perror("accept");
+		exit(EXIT_FAILURE);
+	}
+
+	/* Send 1 byte. */
+	send_byte(fd, 1, 0);
+
+	control_writeln("SRVSENT");
+
+	/* Wait until client is ready to receive rest of data. */
+	control_expectln("CLNSENT");
+
+	for (i = 0; i < RCVLOWAT_BUF_SIZE - 1; i++)
+		send_byte(fd, 1, 0);
+
+	/* Keep socket in active state. */
+	control_expectln("POLLDONE");
+
+	close(fd);
+}
+
+static void test_stream_poll_rcvlowat_client(const struct test_opts *opts)
+{
+	unsigned long lowat_val = RCVLOWAT_BUF_SIZE;
+	char buf[RCVLOWAT_BUF_SIZE];
+	struct pollfd fds;
+	ssize_t read_res;
+	short poll_flags;
+	int fd;
+
+	fd = vsock_stream_connect(opts->peer_cid, 1234);
+	if (fd < 0) {
+		perror("connect");
+		exit(EXIT_FAILURE);
+	}
+
+	if (setsockopt(fd, SOL_SOCKET, SO_RCVLOWAT,
+			&lowat_val, sizeof(lowat_val))) {
+		perror("setsockopt");
+		exit(EXIT_FAILURE);
+	}
+
+	control_expectln("SRVSENT");
+
+	/* At this point, server sent 1 byte. */
+	fds.fd = fd;
+	poll_flags = POLLIN | POLLRDNORM;
+	fds.events = poll_flags;
+
+	/* Try to wait for 1 sec. */
+	if (poll(&fds, 1, 1000) < 0) {
+		perror("poll");
+		exit(EXIT_FAILURE);
+	}
+
+	/* poll() must return nothing. */
+	if (fds.revents) {
+		fprintf(stderr, "Unexpected poll result %hx\n",
+			fds.revents);
+		exit(EXIT_FAILURE);
+	}
+
+	/* Tell server to send rest of data. */
+	control_writeln("CLNSENT");
+
+	/* Poll for data. */
+	if (poll(&fds, 1, 10000) < 0) {
+		perror("poll");
+		exit(EXIT_FAILURE);
+	}
+
+	/* Only these two bits are expected. */
+	if (fds.revents != poll_flags) {
+		fprintf(stderr, "Unexpected poll result %hx\n",
+			fds.revents);
+		exit(EXIT_FAILURE);
+	}
+
+	/* Use MSG_DONTWAIT, if call is going to wait, EAGAIN
+	 * will be returned.
+	 */
+	read_res = recv(fd, buf, sizeof(buf), MSG_DONTWAIT);
+	if (read_res != RCVLOWAT_BUF_SIZE) {
+		fprintf(stderr, "Unexpected recv result %zi\n",
+			read_res);
+		exit(EXIT_FAILURE);
+	}
+
+	control_writeln("POLLDONE");
+
+	close(fd);
+}
+
 static struct test_case test_cases[] = {
 	{
 		.name = "SOCK_STREAM connection reset",
@@ -646,6 +748,11 @@ static struct test_case test_cases[] = {
 		.run_client = test_seqpacket_invalid_rec_buffer_client,
 		.run_server = test_seqpacket_invalid_rec_buffer_server,
 	},
+	{
+		.name = "SOCK_STREAM poll() + SO_RCVLOWAT",
+		.run_client = test_stream_poll_rcvlowat_client,
+		.run_server = test_stream_poll_rcvlowat_server,
+	},
 	{},
 };
 
-- 
2.25.1

Re: [RFC PATCH v3 9/9] vsock_test: POLLIN + SO_RCVLOWAT test

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 02:07:58PM +0000, Arseniy Krasnov wrote:
>This adds test to check,that when poll() returns POLLIN,POLLRDNORM bits,
>next read call won't block.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> tools/testing/vsock/vsock_test.c | 107 +++++++++++++++++++++++++++++++
> 1 file changed, 107 insertions(+)
>
>diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
>index dc577461afc2..920dc5d5d979 100644
>--- a/tools/testing/vsock/vsock_test.c
>+++ b/tools/testing/vsock/vsock_test.c
>@@ -18,6 +18,7 @@
> #include <sys/socket.h>
> #include <time.h>
> #include <sys/mman.h>
>+#include <poll.h>
>
> #include "timeout.h"
> #include "control.h"
>@@ -596,6 +597,107 @@ static void test_seqpacket_invalid_rec_buffer_server(const struct test_opts *opt
> 	close(fd);
> }
>
>+static void test_stream_poll_rcvlowat_server(const struct test_opts *opts)
>+{
>+#define RCVLOWAT_BUF_SIZE 128

Since we use this macro on both server and client functions, I suggest 
to move this define outside the function.

Other than that the test LGTM. I also ran it and everything is fine :-) 
thanks for adding it!

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Re: [RFC PATCH v3 9/9] vsock_test: POLLIN + SO_RCVLOWAT test

[Stefano Garzarella]

On Wed, Aug 03, 2022 at 02:07:58PM +0000, Arseniy Krasnov wrote:
>This adds test to check,that when poll() returns POLLIN,POLLRDNORM bits,
>next read call won't block.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> tools/testing/vsock/vsock_test.c | 107 +++++++++++++++++++++++++++++++
> 1 file changed, 107 insertions(+)
>
>diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
>index dc577461afc2..920dc5d5d979 100644
>--- a/tools/testing/vsock/vsock_test.c
>+++ b/tools/testing/vsock/vsock_test.c
>@@ -18,6 +18,7 @@
> #include <sys/socket.h>
> #include <time.h>
> #include <sys/mman.h>
>+#include <poll.h>
>
> #include "timeout.h"
> #include "control.h"
>@@ -596,6 +597,107 @@ static void test_seqpacket_invalid_rec_buffer_server(const struct test_opts *opt
> 	close(fd);
> }
>
>+static void test_stream_poll_rcvlowat_server(const struct test_opts *opts)
>+{
>+#define RCVLOWAT_BUF_SIZE 128
>+	int fd;
>+	int i;
>+
>+	fd = vsock_stream_accept(VMADDR_CID_ANY, 1234, NULL);
>+	if (fd < 0) {
>+		perror("accept");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	/* Send 1 byte. */
>+	send_byte(fd, 1, 0);
>+
>+	control_writeln("SRVSENT");
>+
>+	/* Wait until client is ready to receive rest of data. */
>+	control_expectln("CLNSENT");
>+
>+	for (i = 0; i < RCVLOWAT_BUF_SIZE - 1; i++)
>+		send_byte(fd, 1, 0);
>+
>+	/* Keep socket in active state. */
>+	control_expectln("POLLDONE");
>+
>+	close(fd);
>+}
>+
>+static void test_stream_poll_rcvlowat_client(const struct test_opts *opts)
>+{
>+	unsigned long lowat_val = RCVLOWAT_BUF_SIZE;
>+	char buf[RCVLOWAT_BUF_SIZE];
>+	struct pollfd fds;
>+	ssize_t read_res;
>+	short poll_flags;
>+	int fd;
>+
>+	fd = vsock_stream_connect(opts->peer_cid, 1234);
>+	if (fd < 0) {
>+		perror("connect");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	if (setsockopt(fd, SOL_SOCKET, SO_RCVLOWAT,
>+			&lowat_val, sizeof(lowat_val))) {

A small checkpatch warning that you can fix since you have to resend:

CHECK: Alignment should match open parenthesis
#76: FILE: tools/testing/vsock/vsock_test.c:645:
+	if (setsockopt(fd, SOL_SOCKET, SO_RCVLOWAT,
+			&lowat_val, sizeof(lowat_val))) {

total: 0 errors, 0 warnings, 1 checks, 125 lines checked

Thanks,
Stefano

Re: [RFC PATCH v3 0/9] vsock: updates for SO_RCVLOWAT handling

[Stefano Garzarella]

Hi Arseniy,
sorry but I didn't have time to review this series. I will definitely do 
it next Monday!

Have a nice weekend,
Stefano

On Wed, Aug 03, 2022 at 01:48:06PM +0000, Arseniy Krasnov wrote:
>Hello,
>
>This patchset includes some updates for SO_RCVLOWAT:
>
>1) af_vsock:
>   During my experiments with zerocopy receive, i found, that in some
>   cases, poll() implementation violates POSIX: when socket has non-
>   default SO_RCVLOWAT(e.g. not 1), poll() will always set POLLIN and
>   POLLRDNORM bits in 'revents' even number of bytes available to read
>   on socket is smaller than SO_RCVLOWAT value. In this case,user sees
>   POLLIN flag and then tries to read data(for example using  'read()'
>   call), but read call will be blocked, because  SO_RCVLOWAT logic is
>   supported in dequeue loop in af_vsock.c. But the same time,  POSIX
>   requires that:
>
>   "POLLIN     Data other than high-priority data may be read without
>               blocking.
>    POLLRDNORM Normal data may be read without blocking."
>
>   See https://www.open-std.org/jtc1/sc22/open/n4217.pdf, page 293.
>
>   So, we have, that poll() syscall returns POLLIN, but read call will
>   be blocked.
>
>   Also in man page socket(7) i found that:
>
>   "Since Linux 2.6.28, select(2), poll(2), and epoll(7) indicate a
>   socket as readable only if at least SO_RCVLOWAT bytes are available."
>
>   I checked TCP callback for poll()(net/ipv4/tcp.c, tcp_poll()), it
>   uses SO_RCVLOWAT value to set POLLIN bit, also i've tested TCP with
>   this case for TCP socket, it works as POSIX required.
>
>   I've added some fixes to af_vsock.c and virtio_transport_common.c,
>   test is also implemented.
>
>2) virtio/vsock:
>   It adds some optimization to wake ups, when new data arrived. Now,
>   SO_RCVLOWAT is considered before wake up sleepers who wait new data.
>   There is no sense, to kick waiter, when number of available bytes
>   in socket's queue < SO_RCVLOWAT, because if we wake up reader in
>   this case, it will wait for SO_RCVLOWAT data anyway during dequeue,
>   or in poll() case, POLLIN/POLLRDNORM bits won't be set, so such
>   exit from poll() will be "spurious". This logic is also used in TCP
>   sockets.
>
>3) vmci/vsock:
>   Same as 2), but i'm not sure about this changes. Will be very good,
>   to get comments from someone who knows this code.
>
>4) Hyper-V:
>   As Dexuan Cui mentioned, for Hyper-V transport it is difficult to
>   support SO_RCVLOWAT, so he suggested to disable this feature for
>   Hyper-V.
>
>Thank You
>
>Arseniy Krasnov(9):
> vsock: SO_RCVLOWAT transport set callback
> hv_sock: disable SO_RCVLOWAT support
> virtio/vsock: use 'target' in notify_poll_in callback
> vmci/vsock: use 'target' in notify_poll_in callback
> vsock: pass sock_rcvlowat to notify_poll_in as target
> vsock: add API call for data ready
> virtio/vsock: check SO_RCVLOWAT before wake up reader
> vmci/vsock: check SO_RCVLOWAT before wake up reader
> vsock_test: POLLIN + SO_RCVLOWAT test
>
> include/net/af_vsock.h                       |   2 +
> net/vmw_vsock/af_vsock.c                     |  38 +++++++++-
> net/vmw_vsock/hyperv_transport.c             |   7 ++
> net/vmw_vsock/virtio_transport_common.c      |   7 +-
> net/vmw_vsock/vmci_transport_notify.c        |  10 +--
> net/vmw_vsock/vmci_transport_notify_qstate.c |  12 +--
> tools/testing/vsock/vsock_test.c             | 107 +++++++++++++++++++++++++++
> 7 files changed, 166 insertions(+), 17 deletions(-)
>
> Changelog:
>
> v1 -> v2:
> 1) Patches for VMCI transport(same as for virtio-vsock).
> 2) Patches for Hyper-V transport(disabling SO_RCVLOWAT setting).
> 3) Waiting logic in test was updated(sleep() -> poll()).
>
> v2 -> v3:
> 1) Patches were reordered.
> 2) Commit message updated in 0005.
> 3) Check 'transport' pointer in 0001 for NULL.
> 4) Check 'value' in 0001 for > buffer_size.
>
>-- 
>2.25.1

Re: [RFC PATCH v3 0/9] vsock: updates for SO_RCVLOWAT handling

[Arseniy Krasnov]

On 05.08.2022 19:05, Stefano Garzarella wrote:
> Hi Arseniy,
> sorry but I didn't have time to review this series. I will definitely do it next Monday!
> 
> Have a nice weekend,
> Stefano
Hello,
no problem

Thank You
> 
> On Wed, Aug 03, 2022 at 01:48:06PM +0000, Arseniy Krasnov wrote:
>> Hello,
>>
>> This patchset includes some updates for SO_RCVLOWAT:
>>
>> 1) af_vsock:
>>   During my experiments with zerocopy receive, i found, that in some
>>   cases, poll() implementation violates POSIX: when socket has non-
>>   default SO_RCVLOWAT(e.g. not 1), poll() will always set POLLIN and
>>   POLLRDNORM bits in 'revents' even number of bytes available to read
>>   on socket is smaller than SO_RCVLOWAT value. In this case,user sees
>>   POLLIN flag and then tries to read data(for example using  'read()'
>>   call), but read call will be blocked, because  SO_RCVLOWAT logic is
>>   supported in dequeue loop in af_vsock.c. But the same time,  POSIX
>>   requires that:
>>
>>   "POLLIN     Data other than high-priority data may be read without
>>               blocking.
>>    POLLRDNORM Normal data may be read without blocking."
>>
>>   See https://www.open-std.org/jtc1/sc22/open/n4217.pdf, page 293.
>>
>>   So, we have, that poll() syscall returns POLLIN, but read call will
>>   be blocked.
>>
>>   Also in man page socket(7) i found that:
>>
>>   "Since Linux 2.6.28, select(2), poll(2), and epoll(7) indicate a
>>   socket as readable only if at least SO_RCVLOWAT bytes are available."
>>
>>   I checked TCP callback for poll()(net/ipv4/tcp.c, tcp_poll()), it
>>   uses SO_RCVLOWAT value to set POLLIN bit, also i've tested TCP with
>>   this case for TCP socket, it works as POSIX required.
>>
>>   I've added some fixes to af_vsock.c and virtio_transport_common.c,
>>   test is also implemented.
>>
>> 2) virtio/vsock:
>>   It adds some optimization to wake ups, when new data arrived. Now,
>>   SO_RCVLOWAT is considered before wake up sleepers who wait new data.
>>   There is no sense, to kick waiter, when number of available bytes
>>   in socket's queue < SO_RCVLOWAT, because if we wake up reader in
>>   this case, it will wait for SO_RCVLOWAT data anyway during dequeue,
>>   or in poll() case, POLLIN/POLLRDNORM bits won't be set, so such
>>   exit from poll() will be "spurious". This logic is also used in TCP
>>   sockets.
>>
>> 3) vmci/vsock:
>>   Same as 2), but i'm not sure about this changes. Will be very good,
>>   to get comments from someone who knows this code.
>>
>> 4) Hyper-V:
>>   As Dexuan Cui mentioned, for Hyper-V transport it is difficult to
>>   support SO_RCVLOWAT, so he suggested to disable this feature for
>>   Hyper-V.
>>
>> Thank You
>>
>> Arseniy Krasnov(9):
>> vsock: SO_RCVLOWAT transport set callback
>> hv_sock: disable SO_RCVLOWAT support
>> virtio/vsock: use 'target' in notify_poll_in callback
>> vmci/vsock: use 'target' in notify_poll_in callback
>> vsock: pass sock_rcvlowat to notify_poll_in as target
>> vsock: add API call for data ready
>> virtio/vsock: check SO_RCVLOWAT before wake up reader
>> vmci/vsock: check SO_RCVLOWAT before wake up reader
>> vsock_test: POLLIN + SO_RCVLOWAT test
>>
>> include/net/af_vsock.h                       |   2 +
>> net/vmw_vsock/af_vsock.c                     |  38 +++++++++-
>> net/vmw_vsock/hyperv_transport.c             |   7 ++
>> net/vmw_vsock/virtio_transport_common.c      |   7 +-
>> net/vmw_vsock/vmci_transport_notify.c        |  10 +--
>> net/vmw_vsock/vmci_transport_notify_qstate.c |  12 +--
>> tools/testing/vsock/vsock_test.c             | 107 +++++++++++++++++++++++++++
>> 7 files changed, 166 insertions(+), 17 deletions(-)
>>
>> Changelog:
>>
>> v1 -> v2:
>> 1) Patches for VMCI transport(same as for virtio-vsock).
>> 2) Patches for Hyper-V transport(disabling SO_RCVLOWAT setting).
>> 3) Waiting logic in test was updated(sleep() -> poll()).
>>
>> v2 -> v3:
>> 1) Patches were reordered.
>> 2) Commit message updated in 0005.
>> 3) Check 'transport' pointer in 0001 for NULL.
>> 4) Check 'value' in 0001 for > buffer_size.
>>
>> -- 
>> 2.25.1
> 

Re: [RFC PATCH v3 0/9] vsock: updates for SO_RCVLOWAT handling

[Stefano Garzarella]

Hi Arseniy,

On Wed, Aug 03, 2022 at 01:48:06PM +0000, Arseniy Krasnov wrote:
>Hello,
>
>This patchset includes some updates for SO_RCVLOWAT:

I have reviewed all the patches, run tests and everything seems okay :-)

I left some minor comments and asked Bryan and Vishnu to take a better 
look at VMCI patches.

In general I ask you to revisit the patch descriptions a bit (for 
example adding a space after punctuation). The next version I think can 
be without RFC.

Remember to send it with the net-next tag.
Note: net-next is closed for now since we are in the merge window.
It should re-open in a week (you can check here: 
http://vger.kernel.org/~davem/net-next.html).

I'll be on vacation the next 2 weeks (Aug 15 - 28), but I'll try to 
check out your patches!

Thanks,
Stefano

Re: [RFC PATCH v3 0/9] vsock: updates for SO_RCVLOWAT handling

[Arseniy Krasnov]

On 08.08.2022 14:22, Stefano Garzarella wrote:
> Hi Arseniy,
> 
> On Wed, Aug 03, 2022 at 01:48:06PM +0000, Arseniy Krasnov wrote:
>> Hello,
>>
>> This patchset includes some updates for SO_RCVLOWAT:
> 
> I have reviewed all the patches, run tests and everything seems okay :-)
Thank You
> 
> I left some minor comments and asked Bryan and Vishnu to take a better look at VMCI patches.
Ok, let's wait their reply before v4
> 
> In general I ask you to revisit the patch descriptions a bit (for example adding a space after punctuation). The next version I think can be without RFC.
ack
> 
> Remember to send it with the net-next tag.
> Note: net-next is closed for now since we are in the merge window.
> It should re-open in a week (you can check here: http://vger.kernel.org/~davem/net-next.html).
> 
> I'll be on vacation the next 2 weeks (Aug 15 - 28), but I'll try to check out your patches!
No problem, thanks
> 
> Thanks,
> Stefano
>