Messages in this thread | | | Date | Tue, 25 Jul 2023 14:45:48 +0200 | From | Stefano Garzarella <> | Subject | Re: [PATCH net-next v3 4/4] vsock/virtio: MSG_ZEROCOPY flag support |
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On Tue, Jul 25, 2023 at 08:39:17AM -0400, Michael S. Tsirkin wrote: >On Tue, Jul 25, 2023 at 02:28:02PM +0200, Stefano Garzarella wrote: >> On Tue, Jul 25, 2023 at 12:16:11PM +0300, Arseniy Krasnov wrote: >> > >> > >> > On 25.07.2023 11:46, Arseniy Krasnov wrote: >> > > >> > > >> > > On 25.07.2023 11:43, Stefano Garzarella wrote: >> > > > On Fri, Jul 21, 2023 at 08:09:03AM +0300, Arseniy Krasnov wrote: >> > > > > >> > > > > >> > > > > On 21.07.2023 00:42, Arseniy Krasnov wrote: >> > > > > > This adds handling of MSG_ZEROCOPY flag on transmission path: if this >> > > > > > flag is set and zerocopy transmission is possible (enabled in socket >> > > > > > options and transport allows zerocopy), then non-linear skb will be >> > > > > > created and filled with the pages of user's buffer. Pages of user's >> > > > > > buffer are locked in memory by 'get_user_pages()'. Second thing that >> > > > > > this patch does is replace type of skb owning: instead of calling >> > > > > > 'skb_set_owner_sk_safe()' it calls 'skb_set_owner_w()'. Reason of this >> > > > > > change is that '__zerocopy_sg_from_iter()' increments 'sk_wmem_alloc' >> > > > > > of socket, so to decrease this field correctly proper skb destructor is >> > > > > > needed: 'sock_wfree()'. This destructor is set by 'skb_set_owner_w()'. >> > > > > > >> > > > > > Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >> > > > > > --- >> > > > > > Changelog: >> > > > > > v5(big patchset) -> v1: >> > > > > > * Refactorings of 'if' conditions. >> > > > > > * Remove extra blank line. >> > > > > > * Remove 'frag_off' field unneeded init. >> > > > > > * Add function 'virtio_transport_fill_skb()' which fills both linear >> > > > > > and non-linear skb with provided data. >> > > > > > v1 -> v2: >> > > > > > * Use original order of last four arguments in 'virtio_transport_alloc_skb()'. >> > > > > > v2 -> v3: >> > > > > > * Add new transport callback: 'msgzerocopy_check_iov'. It checks that >> > > > > > provided 'iov_iter' with data could be sent in a zerocopy mode. >> > > > > > If this callback is not set in transport - transport allows to send >> > > > > > any 'iov_iter' in zerocopy mode. Otherwise - if callback returns 'true' >> > > > > > then zerocopy is allowed. Reason of this callback is that in case of >> > > > > > G2H transmission we insert whole skb to the tx virtio queue and such >> > > > > > skb must fit to the size of the virtio queue to be sent in a single >> > > > > > iteration (may be tx logic in 'virtio_transport.c' could be reworked >> > > > > > as in vhost to support partial send of current skb). This callback >> > > > > > will be enabled only for G2H path. For details pls see comment >> > > > > > 'Check that tx queue...' below. >> > > > > > >> > > > > > include/net/af_vsock.h | 3 + >> > > > > > net/vmw_vsock/virtio_transport.c | 39 ++++ >> > > > > > net/vmw_vsock/virtio_transport_common.c | 257 ++++++++++++++++++------ >> > > > > > 3 files changed, 241 insertions(+), 58 deletions(-) >> > > > > > >> > > > > > diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h >> > > > > > index 0e7504a42925..a6b346eeeb8e 100644 >> > > > > > --- a/include/net/af_vsock.h >> > > > > > +++ b/include/net/af_vsock.h >> > > > > > @@ -177,6 +177,9 @@ struct vsock_transport { >> > > > > > >> > > > > > /* Read a single skb */ >> > > > > > int (*read_skb)(struct vsock_sock *, skb_read_actor_t); >> > > > > > + >> > > > > > + /* Zero-copy. */ >> > > > > > + bool (*msgzerocopy_check_iov)(const struct iov_iter *); >> > > > > > }; >> > > > > > >> > > > > > /**** CORE ****/ >> > > > > > diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c >> > > > > > index 7bbcc8093e51..23cb8ed638c4 100644 >> > > > > > --- a/net/vmw_vsock/virtio_transport.c >> > > > > > +++ b/net/vmw_vsock/virtio_transport.c >> > > > > > @@ -442,6 +442,43 @@ static void virtio_vsock_rx_done(struct virtqueue *vq) >> > > > > > queue_work(virtio_vsock_workqueue, &vsock->rx_work); >> > > > > > } >> > > > > > >> > > > > > +static bool >> > > > > > virtio_transport_msgzerocopy_check_iov(const struct >> > > > > > iov_iter *iov) >> > > > > > +{ >> > > > > > + struct virtio_vsock *vsock; >> > > > > > + bool res = false; >> > > > > > + >> > > > > > + rcu_read_lock(); >> > > > > > + >> > > > > > + vsock = rcu_dereference(the_virtio_vsock); >> > > > > > + if (vsock) { >> >> Just noted, what about the following to reduce the indentation? >> >> if (!vsock) { >> goto out; >> } > >no {} pls
ooops, true, too much QEMU code today, but luckily checkpatch would have spotted it ;-)
> >> ... >> ... >> out: >> rcu_read_unlock(); >> return res; > >indentation is quite modest here. Not sure goto is worth it.
It's a pattern we follow a lot in this file, and I find the early return/goto more readable. Anyway, I don't have a strong opinion, it's fine the way it is now, actually we don't have too many indentations for now in this function.
Thanks, Stefano
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