[PATCH net-next 07/13] sock: add ee_code SO_EE_CODE_ZEROCOPY_COPIED

[Willem de Bruijn]

From: Willem de Bruijn <will...@google.com>

A send request with MSG_ZEROCOPY falls back to copying when a request
cannot be completed in zerocopy mode.

Notify processes when the call reverted to copying through a new bit
in the completion notification, so that they can optionally decline
passing the flag on subsequent calls on the same path.

Signed-off-by: Willem de Bruijn <will...@google.com>
---
 include/linux/skbuff.h        | 2 ++
 include/uapi/linux/errqueue.h | 2 ++
 net/core/skbuff.c             | 5 ++++-
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 1d842860f074..24479da9905c 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -416,6 +416,7 @@ struct ubuf_info {
                struct {
                        u32 id;
                        u16 len;
+                       u16 zerocopy:1;
                        u32 bytelen;
                };
        };
@@ -1257,6 +1258,7 @@ static inline void skb_zcopy_clear(struct sk_buff *skb, 
bool zerocopy)
        struct ubuf_info *uarg = skb_zcopy(skb);
 
        if (uarg) {
+               uarg->zerocopy = uarg->zerocopy && zerocopy;
                sock_zerocopy_put(uarg);
                skb_shinfo(skb)->tx_flags &= ~SKBTX_ZEROCOPY_FRAG;
        }
diff --git a/include/uapi/linux/errqueue.h b/include/uapi/linux/errqueue.h
index 0f15a77c9e39..78fdf52d6b2f 100644
--- a/include/uapi/linux/errqueue.h
+++ b/include/uapi/linux/errqueue.h
@@ -23,6 +23,8 @@ struct sock_extended_err {
 
 #define SO_EE_OFFENDER(ee)     ((struct sockaddr*)((ee)+1))
 
+#define SO_EE_CODE_ZEROCOPY_COPIED     1
+
 /**
  *     struct scm_timestamping - timestamps exposed through cmsg
  *
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 41fedc4e651f..35a7a7b1192f 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -943,6 +943,7 @@ struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, 
size_t size)
        uarg->callback = sock_zerocopy_callback;
        uarg->id = ((u32)atomic_inc_return(&sk->sk_zckey)) - 1;
        uarg->len = 1;
+       uarg->zerocopy = 1;
        uarg->bytelen = size;
        atomic_set(&uarg->refcnt, 0);
        sock_hold(sk);
@@ -1039,6 +1040,8 @@ void sock_zerocopy_callback(struct ubuf_info *uarg, bool 
success)
        serr->ee.ee_origin = SO_EE_ORIGIN_ZEROCOPY;
        serr->ee.ee_data = hi;
        serr->ee.ee_info = lo;
+       if (!success)
+               serr->ee.ee_code |= SO_EE_CODE_ZEROCOPY_COPIED;
 
        spin_lock_irqsave(&q->lock, flags);
        tail = skb_peek_tail(q);
@@ -1061,7 +1064,7 @@ void sock_zerocopy_put(struct ubuf_info *uarg)
 {
        if (uarg && atomic_dec_and_test(&uarg->refcnt)) {
                if (uarg->callback)
-                       uarg->callback(uarg, true);
+                       uarg->callback(uarg, uarg->zerocopy);
                else
                        consume_skb(skb_from_uarg(uarg));
        }
-- 
2.13.1.518.g3df882009-goog