From: Willem de Bruijn <will...@google.com>
The kernel supports zerocopy sendmsg in virtio and tap. Expand the
infrastructure to support other socket types. Introduce a completion
notification channel over the socket error queue. Notifications are
returned with ee_origin SO_EE_ORIGIN_ZEROCOPY. ee_errno is 0 to avoid
blocking the send/recv path on receiving notifications.
Add reference counting, to support the skb split, merge, resize and
clone operations possible with SOCK_STREAM and other socket types.
The patch does not yet modify any datapaths.
Signed-off-by: Willem de Bruijn <will...@google.com>
---
include/linux/skbuff.h | 60 +++++++++++++++++++
include/linux/socket.h | 1 +
include/net/sock.h | 2 +
include/uapi/linux/errqueue.h | 3 +
net/core/datagram.c | 55 ++++++++++-------
net/core/skbuff.c | 133 ++++++++++++++++++++++++++++++++++++++++++
net/core/sock.c | 2 +
7 files changed, 235 insertions(+), 21 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2f64e2bbb592..59cff7aa494e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -429,6 +429,7 @@ enum {
SKBTX_SCHED_TSTAMP = 1 << 6,
};
+#define SKBTX_ZEROCOPY_FRAG (SKBTX_DEV_ZEROCOPY | SKBTX_SHARED_FRAG)
#define SKBTX_ANY_SW_TSTAMP (SKBTX_SW_TSTAMP | \
SKBTX_SCHED_TSTAMP)
#define SKBTX_ANY_TSTAMP (SKBTX_HW_TSTAMP | SKBTX_ANY_SW_TSTAMP)
@@ -445,8 +446,28 @@ struct ubuf_info {
void (*callback)(struct ubuf_info *, bool zerocopy_success);
void *ctx;
unsigned long desc;
+ u16 zerocopy:1;
+ atomic_t refcnt;
};
+#define skb_uarg(SKB) ((struct ubuf_info *)(skb_shinfo(SKB)->destructor_arg))
+
+struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, size_t size);
+
+static inline void sock_zerocopy_get(struct ubuf_info *uarg)
+{
+ atomic_inc(&uarg->refcnt);
+}
+
+void sock_zerocopy_put(struct ubuf_info *uarg);
+void sock_zerocopy_put_abort(struct ubuf_info *uarg);
+
+void sock_zerocopy_callback(struct ubuf_info *uarg, bool success);
+
+int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
+ struct msghdr *msg, int len,
+ struct ubuf_info *uarg);
+
/* This data is invariant across clones and lives at
* the end of the header data, ie. at skb->end.
*/
@@ -1214,6 +1235,45 @@ static inline struct skb_shared_hwtstamps
*skb_hwtstamps(struct sk_buff *skb)
return &skb_shinfo(skb)->hwtstamps;
}
+static inline struct ubuf_info *skb_zcopy(struct sk_buff *skb)
+{
+ bool is_zcopy = skb && skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY;
+
+ return is_zcopy ? skb_uarg(skb) : NULL;
+}
+
+static inline void skb_zcopy_set(struct sk_buff *skb, struct ubuf_info *uarg)
+{
+ if (skb && uarg && !skb_zcopy(skb)) {
+ sock_zerocopy_get(uarg);
+ skb_shinfo(skb)->destructor_arg = uarg;
+ skb_shinfo(skb)->tx_flags |= SKBTX_ZEROCOPY_FRAG;
+ }
+}
+
+/* Release a reference on a zerocopy structure */
+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;
+ }
+}
+
+/* Abort a zerocopy operation and revert zckey on error in send syscall */
+static inline void skb_zcopy_abort(struct sk_buff *skb)
+{
+ struct ubuf_info *uarg = skb_zcopy(skb);
+
+ if (uarg) {
+ sock_zerocopy_put_abort(uarg);
+ skb_shinfo(skb)->tx_flags &= ~SKBTX_ZEROCOPY_FRAG;
+ }
+}
+
/**
* skb_queue_empty - check if a queue is empty
* @list: queue head
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 8b13db5163cc..8ad963cdc88c 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -287,6 +287,7 @@ struct ucred {
#define MSG_BATCH 0x40000 /* sendmmsg(): more messages coming */
#define MSG_EOF MSG_FIN
+#define MSG_ZEROCOPY 0x4000000 /* Use user data in kernel path */
#define MSG_FASTOPEN 0x20000000 /* Send data in TCP SYN */
#define MSG_CMSG_CLOEXEC 0x40000000 /* Set close_on_exec for file
descriptor received through
diff --git a/include/net/sock.h b/include/net/sock.h
index 0f778d3c4300..fe1a0bc25cd3 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -294,6 +294,7 @@ struct sock_common {
* @sk_stamp: time stamp of last packet received
* @sk_tsflags: SO_TIMESTAMPING socket options
* @sk_tskey: counter to disambiguate concurrent tstamp requests
+ * @sk_zckey: counter to order MSG_ZEROCOPY notifications
* @sk_socket: Identd and reporting IO signals
* @sk_user_data: RPC layer private data
* @sk_frag: cached page frag
@@ -462,6 +463,7 @@ struct sock {
u16 sk_tsflags;
u8 sk_shutdown;
u32 sk_tskey;
+ atomic_t sk_zckey;
struct socket *sk_socket;
void *sk_user_data;
#ifdef CONFIG_SECURITY
diff --git a/include/uapi/linux/errqueue.h b/include/uapi/linux/errqueue.h
index 07bdce1f444a..78fdf52d6b2f 100644
--- a/include/uapi/linux/errqueue.h
+++ b/include/uapi/linux/errqueue.h
@@ -18,10 +18,13 @@ struct sock_extended_err {
#define SO_EE_ORIGIN_ICMP 2
#define SO_EE_ORIGIN_ICMP6 3
#define SO_EE_ORIGIN_TXSTATUS 4
+#define SO_EE_ORIGIN_ZEROCOPY 5
#define SO_EE_ORIGIN_TIMESTAMPING SO_EE_ORIGIN_TXSTATUS
#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/datagram.c b/net/core/datagram.c
index ee5647bd91b3..2f3277945d35 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -573,27 +573,12 @@ int skb_copy_datagram_from_iter(struct sk_buff *skb, int
offset,
}
EXPORT_SYMBOL(skb_copy_datagram_from_iter);
-/**
- * zerocopy_sg_from_iter - Build a zerocopy datagram from an iov_iter
- * @skb: buffer to copy
- * @from: the source to copy from
- *
- * The function will first copy up to headlen, and then pin the userspace
- * pages and build frags through them.
- *
- * Returns 0, -EFAULT or -EMSGSIZE.
- */
-int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
+int __zerocopy_sg_from_iter(struct sock *sk, struct sk_buff *skb,
+ struct iov_iter *from, size_t length)
{
- int len = iov_iter_count(from);
- int copy = min_t(int, skb_headlen(skb), len);
- int frag = 0;
+ int frag = skb_shinfo(skb)->nr_frags;
- /* copy up to skb headlen */
- if (skb_copy_datagram_from_iter(skb, 0, from, copy))
- return -EFAULT;
-
- while (iov_iter_count(from)) {
+ while (length && iov_iter_count(from)) {
struct page *pages[MAX_SKB_FRAGS];
size_t start;
ssize_t copied;
@@ -603,18 +588,24 @@ int zerocopy_sg_from_iter(struct sk_buff *skb, struct
iov_iter *from)
if (frag == MAX_SKB_FRAGS)
return -EMSGSIZE;
- copied = iov_iter_get_pages(from, pages, ~0U,
+ copied = iov_iter_get_pages(from, pages, length,
MAX_SKB_FRAGS - frag, &start);
if (copied < 0)
return -EFAULT;
iov_iter_advance(from, copied);
+ length -= copied;
truesize = PAGE_ALIGN(copied + start);
skb->data_len += copied;
skb->len += copied;
skb->truesize += truesize;
- refcount_add(truesize, &skb->sk->sk_wmem_alloc);
+ if (sk && sk->sk_type == SOCK_STREAM) {
+ sk->sk_wmem_queued += truesize;
+ sk_mem_charge(sk, truesize);
+ } else {
+ refcount_add(truesize, &skb->sk->sk_wmem_alloc);
+ }
while (copied) {
int size = min_t(int, copied, PAGE_SIZE - start);
skb_fill_page_desc(skb, frag++, pages[n], start, size);
@@ -625,6 +616,28 @@ int zerocopy_sg_from_iter(struct sk_buff *skb, struct
iov_iter *from)
}
return 0;
}
+EXPORT_SYMBOL(__zerocopy_sg_from_iter);
+
+/**
+ * zerocopy_sg_from_iter - Build a zerocopy datagram from an iov_iter
+ * @skb: buffer to copy
+ * @from: the source to copy from
+ *
+ * The function will first copy up to headlen, and then pin the userspace
+ * pages and build frags through them.
+ *
+ * Returns 0, -EFAULT or -EMSGSIZE.
+ */
+int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
+{
+ int copy = min_t(int, skb_headlen(skb), iov_iter_count(from));
+
+ /* copy up to skb headlen */
+ if (skb_copy_datagram_from_iter(skb, 0, from, copy))
+ return -EFAULT;
+
+ return __zerocopy_sg_from_iter(NULL, skb, from, ~0U);
+}
EXPORT_SYMBOL(zerocopy_sg_from_iter);
static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index a95877a8ac8b..0603e44950da 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -915,6 +915,139 @@ struct sk_buff *skb_morph(struct sk_buff *dst, struct
sk_buff *src)
}
EXPORT_SYMBOL_GPL(skb_morph);
+struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, size_t size)
+{
+ struct ubuf_info *uarg;
+ struct sk_buff *skb;
+
+ WARN_ON_ONCE(!in_task());
+
+ skb = sock_omalloc(sk, 0, GFP_KERNEL);
+ if (!skb)
+ return NULL;
+
+ BUILD_BUG_ON(sizeof(*uarg) > sizeof(skb->cb));
+ uarg = (void *)skb->cb;
+
+ uarg->callback = sock_zerocopy_callback;
+ uarg->desc = atomic_inc_return(&sk->sk_zckey) - 1;
+ uarg->zerocopy = 1;
+ atomic_set(&uarg->refcnt, 0);
+ sock_hold(sk);
+
+ return uarg;
+}
+EXPORT_SYMBOL_GPL(sock_zerocopy_alloc);
+
+static inline struct sk_buff *skb_from_uarg(struct ubuf_info *uarg)
+{
+ return container_of((void *)uarg, struct sk_buff, cb);
+}
+
+void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
+{
+ struct sk_buff *skb = skb_from_uarg(uarg);
+ struct sock_exterr_skb *serr;
+ struct sock *sk = skb->sk;
+ u16 id = uarg->desc;
+
+ if (sock_flag(sk, SOCK_DEAD))
+ goto release;
+
+ serr = SKB_EXT_ERR(skb);
+ memset(serr, 0, sizeof(*serr));
+ serr->ee.ee_errno = 0;
+ serr->ee.ee_origin = SO_EE_ORIGIN_ZEROCOPY;
+ serr->ee.ee_data = id;
+ if (!success)
+ serr->ee.ee_code |= SO_EE_CODE_ZEROCOPY_COPIED;
+
+ skb_queue_tail(&sk->sk_error_queue, skb);
+ skb = NULL;
+
+ sk->sk_error_report(sk);
+
+release:
+ consume_skb(skb);
+ sock_put(sk);
+}
+EXPORT_SYMBOL_GPL(sock_zerocopy_callback);
+
+void sock_zerocopy_put(struct ubuf_info *uarg)
+{
+ if (uarg && atomic_dec_and_test(&uarg->refcnt)) {
+ if (uarg->callback)
+ uarg->callback(uarg, uarg->zerocopy);
+ else
+ consume_skb(skb_from_uarg(uarg));
+ }
+}
+EXPORT_SYMBOL_GPL(sock_zerocopy_put);
+
+void sock_zerocopy_put_abort(struct ubuf_info *uarg)
+{
+ if (uarg) {
+ struct sock *sk = skb_from_uarg(uarg)->sk;
+
+ atomic_dec(&sk->sk_zckey);
+
+ /* sock_zerocopy_put expects a ref. Most sockets take one per
+ * skb, which is zero on abort. tcp_sendmsg holds one extra, to
+ * avoid an skb send inside the main loop triggering uarg free.
+ */
+ if (sk->sk_type != SOCK_STREAM)
+ atomic_inc(&uarg->refcnt);
+
+ sock_zerocopy_put(uarg);
+ }
+}
+EXPORT_SYMBOL_GPL(sock_zerocopy_put_abort);
+
+extern int __zerocopy_sg_from_iter(struct sock *sk, struct sk_buff *skb,
+ struct iov_iter *from, size_t length);
+
+int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
+ struct msghdr *msg, int len,
+ struct ubuf_info *uarg)
+{
+ struct iov_iter orig_iter = msg->msg_iter;
+ int err, orig_len = skb->len;
+
+ err = __zerocopy_sg_from_iter(sk, skb, &msg->msg_iter, len);
+ if (err == -EFAULT || (err == -EMSGSIZE && skb->len == orig_len)) {
+ /* Streams do not free skb on error. Reset to prev state. */
+ msg->msg_iter = orig_iter;
+ ___pskb_trim(skb, orig_len);
+ return err;
+ }
+
+ skb_zcopy_set(skb, uarg);
+ return skb->len - orig_len;
+}
+EXPORT_SYMBOL_GPL(skb_zerocopy_iter_stream);
+
+/* unused only until next patch in the series; will remove attribute */
+static int __attribute__((unused))
+ skb_zerocopy_clone(struct sk_buff *nskb, struct sk_buff *orig,
+ gfp_t gfp_mask)
+{
+ if (skb_zcopy(orig)) {
+ if (skb_zcopy(nskb)) {
+ /* !gfp_mask callers are verified to !skb_zcopy(nskb) */
+ if (!gfp_mask) {
+ WARN_ON_ONCE(1);
+ return -ENOMEM;
+ }
+ if (skb_uarg(nskb) == skb_uarg(orig))
+ return 0;
+ if (skb_copy_ubufs(nskb, GFP_ATOMIC))
+ return -EIO;
+ }
+ skb_zcopy_set(nskb, skb_uarg(orig));
+ }
+ return 0;
+}
+
/**
* skb_copy_ubufs - copy userspace skb frags buffers to kernel
* @skb: the skb to modify
diff --git a/net/core/sock.c b/net/core/sock.c
index 1261880bdcc8..e8b696858cad 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1670,6 +1670,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const
gfp_t priority)
atomic_set(&newsk->sk_drops, 0);
newsk->sk_send_head = NULL;
newsk->sk_userlocks = sk->sk_userlocks &
~SOCK_BINDPORT_LOCK;
+ atomic_set(&newsk->sk_zckey, 0);
sock_reset_flag(newsk, SOCK_DONE);
@@ -2722,6 +2723,7 @@ void sock_init_data(struct socket *sock, struct sock *sk)
sk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
sk->sk_stamp = SK_DEFAULT_STAMP;
+ atomic_set(&sk->sk_zckey, 0);
#ifdef CONFIG_NET_RX_BUSY_POLL
sk->sk_napi_id = 0;
--
2.14.0.rc1.383.gd1ce394fe2-goog
