Merge tag 'for-5.3/io_uring-20190711' of git://git.kernel.dk/linux-block

Pull io_uring updates from Jens Axboe:
"This contains:

- Support for recvmsg/sendmsg as first class opcodes.

I don't envision going much further down this path, as there are
plans in progress to support potentially any system call in an
async fashion through io_uring. But I think it does make sense to
have certain core ops available directly, especially those that can
support a "try this non-blocking" flag/mode. (me)

- Handle generic short reads automatically.

This can happen fairly easily if parts of the buffered read is
cached. Since the application needs to issue another request for
the remainder, just do this internally and save kernel/user
roundtrip while providing a nicer more robust API. (me)

- Support for linked SQEs.

This allows SQEs to depend on each other, enabling an application
to eg queue a read-from-this-file,write-to-that-file pair. (me)

- Fix race in stopping SQ thread (Jackie)"

* tag 'for-5.3/io_uring-20190711' of git://git.kernel.dk/linux-block:
io_uring: fix io_sq_thread_stop running in front of io_sq_thread
io_uring: add support for recvmsg()
io_uring: add support for sendmsg()
io_uring: add support for sqe links
io_uring: punt short reads to async context
uio: make import_iovec()/compat_import_iovec() return bytes on success

fs/aio.c

···
 	return 0;
 }
 
-static int aio_setup_rw(int rw, const struct iocb *iocb, struct iovec **iovec,
-		bool vectored, bool compat, struct iov_iter *iter)
+static ssize_t aio_setup_rw(int rw, const struct iocb *iocb,
+		struct iovec **iovec, bool vectored, bool compat,
+		struct iov_iter *iter)
 {
 	void __user *buf = (void __user *)(uintptr_t)iocb->aio_buf;
 	size_t len = iocb->aio_nbytes;
···
 		return -EINVAL;
 
 	ret = aio_setup_rw(READ, iocb, &iovec, vectored, compat, &iter);
-	if (ret)
+	if (ret < 0)
 		return ret;
 	ret = rw_verify_area(READ, file, &req->ki_pos, iov_iter_count(&iter));
 	if (!ret)
···
 		return -EINVAL;
 
 	ret = aio_setup_rw(WRITE, iocb, &iovec, vectored, compat, &iter);
-	if (ret)
+	if (ret < 0)
 		return ret;
 	ret = rw_verify_area(WRITE, file, &req->ki_pos, iov_iter_count(&iter));
 	if (!ret) {

fs/io_uring.c

···
 	struct task_struct	*sqo_thread;	/* if using sq thread polling */
 	struct mm_struct	*sqo_mm;
 	wait_queue_head_t	sqo_wait;
+	struct completion	sqo_thread_started;
 
 	struct {
 		/* CQ ring */
···
 
 	struct io_ring_ctx	*ctx;
 	struct list_head	list;
+	struct list_head	link_list;
 	unsigned int		flags;
 	refcount_t		refs;
 #define REQ_F_NOWAIT		1	/* must not punt to workers */
···
 #define REQ_F_SEQ_PREV		8	/* sequential with previous */
 #define REQ_F_IO_DRAIN		16	/* drain existing IO first */
 #define REQ_F_IO_DRAINED	32	/* drain done */
+#define REQ_F_LINK		64	/* linked sqes */
+#define REQ_F_FAIL_LINK		128	/* fail rest of links */
 	u64			user_data;
-	u32			error;	/* iopoll result from callback */
+	u32			result;
 	u32			sequence;
 
 	struct work_struct	work;
···
 	ctx->flags = p->flags;
 	init_waitqueue_head(&ctx->cq_wait);
 	init_completion(&ctx->ctx_done);
+	init_completion(&ctx->sqo_thread_started);
 	mutex_init(&ctx->uring_lock);
 	init_waitqueue_head(&ctx->wait);
 	for (i = 0; i < ARRAY_SIZE(ctx->pending_async); i++) {
···
 	req->flags = 0;
 	/* one is dropped after submission, the other at completion */
 	refcount_set(&req->refs, 2);
+	req->result = 0;
 	return req;
 out:
 	io_ring_drop_ctx_refs(ctx, 1);
···
 	}
 }
 
-static void io_free_req(struct io_kiocb *req)
+static void __io_free_req(struct io_kiocb *req)
 {
 	if (req->file && !(req->flags & REQ_F_FIXED_FILE))
 		fput(req->file);
 	io_ring_drop_ctx_refs(req->ctx, 1);
 	kmem_cache_free(req_cachep, req);
+}
+
+static void io_req_link_next(struct io_kiocb *req)
+{
+	struct io_kiocb *nxt;
+
+	/*
+	 * The list should never be empty when we are called here. But could
+	 * potentially happen if the chain is messed up, check to be on the
+	 * safe side.
+	 */
+	nxt = list_first_entry_or_null(&req->link_list, struct io_kiocb, list);
+	if (nxt) {
+		list_del(&nxt->list);
+		if (!list_empty(&req->link_list)) {
+			INIT_LIST_HEAD(&nxt->link_list);
+			list_splice(&req->link_list, &nxt->link_list);
+			nxt->flags |= REQ_F_LINK;
+		}
+
+		INIT_WORK(&nxt->work, io_sq_wq_submit_work);
+		queue_work(req->ctx->sqo_wq, &nxt->work);
+	}
+}
+
+/*
+ * Called if REQ_F_LINK is set, and we fail the head request
+ */
+static void io_fail_links(struct io_kiocb *req)
+{
+	struct io_kiocb *link;
+
+	while (!list_empty(&req->link_list)) {
+		link = list_first_entry(&req->link_list, struct io_kiocb, list);
+		list_del(&link->list);
+
+		io_cqring_add_event(req->ctx, link->user_data, -ECANCELED);
+		__io_free_req(link);
+	}
+}
+
+static void io_free_req(struct io_kiocb *req)
+{
+	/*
+	 * If LINK is set, we have dependent requests in this chain. If we
+	 * didn't fail this request, queue the first one up, moving any other
+	 * dependencies to the next request. In case of failure, fail the rest
+	 * of the chain.
+	 */
+	if (req->flags & REQ_F_LINK) {
+		if (req->flags & REQ_F_FAIL_LINK)
+			io_fail_links(req);
+		else
+			io_req_link_next(req);
+	}
+
+	__io_free_req(req);
 }
 
 static void io_put_req(struct io_kiocb *req)
···
 		req = list_first_entry(done, struct io_kiocb, list);
 		list_del(&req->list);
 
-		io_cqring_fill_event(ctx, req->user_data, req->error);
+		io_cqring_fill_event(ctx, req->user_data, req->result);
 		(*nr_events)++;
 
 		if (refcount_dec_and_test(&req->refs)) {
 			/* If we're not using fixed files, we have to pair the
 			 * completion part with the file put. Use regular
 			 * completions for those, only batch free for fixed
-			 * file.
+			 * file and non-linked commands.
 			 */
-			if (req->flags & REQ_F_FIXED_FILE) {
+			if ((req->flags & (REQ_F_FIXED_FILE|REQ_F_LINK)) ==
+			    REQ_F_FIXED_FILE) {
 				reqs[to_free++] = req;
 				if (to_free == ARRAY_SIZE(reqs))
 					io_free_req_many(ctx, reqs, &to_free);
···
 
 	kiocb_end_write(kiocb);
 
+	if ((req->flags & REQ_F_LINK) && res != req->result)
+		req->flags |= REQ_F_FAIL_LINK;
 	io_cqring_add_event(req->ctx, req->user_data, res);
 	io_put_req(req);
 }
···
 
 	kiocb_end_write(kiocb);
 
-	req->error = res;
+	if ((req->flags & REQ_F_LINK) && res != req->result)
+		req->flags |= REQ_F_FAIL_LINK;
+	req->result = res;
 	if (res != -EAGAIN)
 		req->flags |= REQ_F_IOPOLL_COMPLETED;
 }
···
 		    !kiocb->ki_filp->f_op->iopoll)
 			return -EOPNOTSUPP;
 
-		req->error = 0;
 		kiocb->ki_flags |= IOCB_HIPRI;
 		kiocb->ki_complete = io_complete_rw_iopoll;
 	} else {
···
 	return 0;
 }
 
-static int io_import_iovec(struct io_ring_ctx *ctx, int rw,
-			   const struct sqe_submit *s, struct iovec **iovec,
-			   struct iov_iter *iter)
+static ssize_t io_import_iovec(struct io_ring_ctx *ctx, int rw,
+			       const struct sqe_submit *s, struct iovec **iovec,
+			       struct iov_iter *iter)
 {
 	const struct io_uring_sqe *sqe = s->sqe;
 	void __user *buf = u64_to_user_ptr(READ_ONCE(sqe->addr));
···
 	opcode = READ_ONCE(sqe->opcode);
 	if (opcode == IORING_OP_READ_FIXED ||
 	    opcode == IORING_OP_WRITE_FIXED) {
-		int ret = io_import_fixed(ctx, rw, sqe, iter);
+		ssize_t ret = io_import_fixed(ctx, rw, sqe, iter);
 		*iovec = NULL;
 		return ret;
 	}
···
 	struct iov_iter iter;
 	struct file *file;
 	size_t iov_count;
-	int ret;
+	ssize_t read_size, ret;
 
 	ret = io_prep_rw(req, s, force_nonblock);
 	if (ret)
···
 		return -EINVAL;
 
 	ret = io_import_iovec(req->ctx, READ, s, &iovec, &iter);
-	if (ret)
+	if (ret < 0)
 		return ret;
+
+	read_size = ret;
+	if (req->flags & REQ_F_LINK)
+		req->result = read_size;
 
 	iov_count = iov_iter_count(&iter);
 	ret = rw_verify_area(READ, file, &kiocb->ki_pos, iov_count);
 	if (!ret) {
 		ssize_t ret2;
 
-		/* Catch -EAGAIN return for forced non-blocking submission */
 		ret2 = call_read_iter(file, kiocb, &iter);
+		/*
+		 * In case of a short read, punt to async. This can happen
+		 * if we have data partially cached. Alternatively we can
+		 * return the short read, in which case the application will
+		 * need to issue another SQE and wait for it. That SQE will
+		 * need async punt anyway, so it's more efficient to do it
+		 * here.
+		 */
+		if (force_nonblock && ret2 > 0 && ret2 < read_size)
+			ret2 = -EAGAIN;
+		/* Catch -EAGAIN return for forced non-blocking submission */
 		if (!force_nonblock || ret2 != -EAGAIN) {
 			io_rw_done(kiocb, ret2);
 		} else {
···
 	struct iov_iter iter;
 	struct file *file;
 	size_t iov_count;
-	int ret;
+	ssize_t ret;
 
 	ret = io_prep_rw(req, s, force_nonblock);
 	if (ret)
···
 		return -EINVAL;
 
 	ret = io_import_iovec(req->ctx, WRITE, s, &iovec, &iter);
-	if (ret)
+	if (ret < 0)
 		return ret;
+
+	if (req->flags & REQ_F_LINK)
+		req->result = ret;
 
 	iov_count = iov_iter_count(&iter);
 
···
 				end > 0 ? end : LLONG_MAX,
 				fsync_flags & IORING_FSYNC_DATASYNC);
 
+	if (ret < 0 && (req->flags & REQ_F_LINK))
+		req->flags |= REQ_F_FAIL_LINK;
 	io_cqring_add_event(req->ctx, sqe->user_data, ret);
 	io_put_req(req);
 	return 0;
···
 
 	ret = sync_file_range(req->rw.ki_filp, sqe_off, sqe_len, flags);
 
+	if (ret < 0 && (req->flags & REQ_F_LINK))
+		req->flags |= REQ_F_FAIL_LINK;
 	io_cqring_add_event(req->ctx, sqe->user_data, ret);
 	io_put_req(req);
 	return 0;
+}
+
+#if defined(CONFIG_NET)
+static int io_send_recvmsg(struct io_kiocb *req, const struct io_uring_sqe *sqe,
+			   bool force_nonblock,
+		   long (*fn)(struct socket *, struct user_msghdr __user *,
+				unsigned int))
+{
+	struct socket *sock;
+	int ret;
+
+	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
+		return -EINVAL;
+
+	sock = sock_from_file(req->file, &ret);
+	if (sock) {
+		struct user_msghdr __user *msg;
+		unsigned flags;
+
+		flags = READ_ONCE(sqe->msg_flags);
+		if (flags & MSG_DONTWAIT)
+			req->flags |= REQ_F_NOWAIT;
+		else if (force_nonblock)
+			flags |= MSG_DONTWAIT;
+
+		msg = (struct user_msghdr __user *) (unsigned long)
+			READ_ONCE(sqe->addr);
+
+		ret = fn(sock, msg, flags);
+		if (force_nonblock && ret == -EAGAIN)
+			return ret;
+	}
+
+	io_cqring_add_event(req->ctx, sqe->user_data, ret);
+	io_put_req(req);
+	return 0;
+}
+#endif
+
+static int io_sendmsg(struct io_kiocb *req, const struct io_uring_sqe *sqe,
+		      bool force_nonblock)
+{
+#if defined(CONFIG_NET)
+	return io_send_recvmsg(req, sqe, force_nonblock, __sys_sendmsg_sock);
+#else
+	return -EOPNOTSUPP;
+#endif
+}
+
+static int io_recvmsg(struct io_kiocb *req, const struct io_uring_sqe *sqe,
+		      bool force_nonblock)
+{
+#if defined(CONFIG_NET)
+	return io_send_recvmsg(req, sqe, force_nonblock, __sys_recvmsg_sock);
+#else
+	return -EOPNOTSUPP;
+#endif
 }
 
 static void io_poll_remove_one(struct io_kiocb *req)
···
 {
 	int ret, opcode;
 
+	req->user_data = READ_ONCE(s->sqe->user_data);
+
 	if (unlikely(s->index >= ctx->sq_entries))
 		return -EINVAL;
-	req->user_data = READ_ONCE(s->sqe->user_data);
 
 	opcode = READ_ONCE(s->sqe->opcode);
 	switch (opcode) {
···
 	case IORING_OP_SYNC_FILE_RANGE:
 		ret = io_sync_file_range(req, s->sqe, force_nonblock);
 		break;
+	case IORING_OP_SENDMSG:
+		ret = io_sendmsg(req, s->sqe, force_nonblock);
+		break;
+	case IORING_OP_RECVMSG:
+		ret = io_recvmsg(req, s->sqe, force_nonblock);
+		break;
 	default:
 		ret = -EINVAL;
 		break;
···
 		return ret;
 
 	if (ctx->flags & IORING_SETUP_IOPOLL) {
-		if (req->error == -EAGAIN)
+		if (req->result == -EAGAIN)
 			return -EAGAIN;
 
 		/* workqueue context doesn't hold uring_lock, grab it now */
···
 	return 0;
 }
 
-static int io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s,
-			 struct io_submit_state *state)
+static int io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
+			struct sqe_submit *s)
 {
-	struct io_kiocb *req;
 	int ret;
-
-	/* enforce forwards compatibility on users */
-	if (unlikely(s->sqe->flags & ~(IOSQE_FIXED_FILE | IOSQE_IO_DRAIN)))
-		return -EINVAL;
-
-	req = io_get_req(ctx, state);
-	if (unlikely(!req))
-		return -EAGAIN;
-
-	ret = io_req_set_file(ctx, s, state, req);
-	if (unlikely(ret))
-		goto out;
-
-	ret = io_req_defer(ctx, req, s->sqe);
-	if (ret) {
-		if (ret == -EIOCBQUEUED)
-			ret = 0;
-		return ret;
-	}
 
 	ret = __io_submit_sqe(ctx, req, s, true);
 	if (ret == -EAGAIN && !(req->flags & REQ_F_NOWAIT)) {
···
 
 			/*
 			 * Queued up for async execution, worker will release
-			 * submit reference when the iocb is actually
-			 * submitted.
+			 * submit reference when the iocb is actually submitted.
 			 */
 			return 0;
 		}
 	}
 
-out:
 	/* drop submission reference */
 	io_put_req(req);
 
 	/* and drop final reference, if we failed */
-	if (ret)
+	if (ret) {
+		io_cqring_add_event(ctx, req->user_data, ret);
+		if (req->flags & REQ_F_LINK)
+			req->flags |= REQ_F_FAIL_LINK;
 		io_put_req(req);
+	}
 
 	return ret;
+}
+
+#define SQE_VALID_FLAGS	(IOSQE_FIXED_FILE|IOSQE_IO_DRAIN|IOSQE_IO_LINK)
+
+static void io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s,
+			  struct io_submit_state *state, struct io_kiocb **link)
+{
+	struct io_uring_sqe *sqe_copy;
+	struct io_kiocb *req;
+	int ret;
+
+	/* enforce forwards compatibility on users */
+	if (unlikely(s->sqe->flags & ~SQE_VALID_FLAGS)) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	req = io_get_req(ctx, state);
+	if (unlikely(!req)) {
+		ret = -EAGAIN;
+		goto err;
+	}
+
+	ret = io_req_set_file(ctx, s, state, req);
+	if (unlikely(ret)) {
+err_req:
+		io_free_req(req);
+err:
+		io_cqring_add_event(ctx, s->sqe->user_data, ret);
+		return;
+	}
+
+	ret = io_req_defer(ctx, req, s->sqe);
+	if (ret) {
+		if (ret != -EIOCBQUEUED)
+			goto err_req;
+		return;
+	}
+
+	/*
+	 * If we already have a head request, queue this one for async
+	 * submittal once the head completes. If we don't have a head but
+	 * IOSQE_IO_LINK is set in the sqe, start a new head. This one will be
+	 * submitted sync once the chain is complete. If none of those
+	 * conditions are true (normal request), then just queue it.
+	 */
+	if (*link) {
+		struct io_kiocb *prev = *link;
+
+		sqe_copy = kmemdup(s->sqe, sizeof(*sqe_copy), GFP_KERNEL);
+		if (!sqe_copy) {
+			ret = -EAGAIN;
+			goto err_req;
+		}
+
+		s->sqe = sqe_copy;
+		memcpy(&req->submit, s, sizeof(*s));
+		list_add_tail(&req->list, &prev->link_list);
+	} else if (s->sqe->flags & IOSQE_IO_LINK) {
+		req->flags |= REQ_F_LINK;
+
+		memcpy(&req->submit, s, sizeof(*s));
+		INIT_LIST_HEAD(&req->link_list);
+		*link = req;
+	} else {
+		io_queue_sqe(ctx, req, s);
+	}
 }
 
 /*
···
 			  unsigned int nr, bool has_user, bool mm_fault)
 {
 	struct io_submit_state state, *statep = NULL;
-	int ret, i, submitted = 0;
+	struct io_kiocb *link = NULL;
+	bool prev_was_link = false;
+	int i, submitted = 0;
 
 	if (nr > IO_PLUG_THRESHOLD) {
 		io_submit_state_start(&state, ctx, nr);
···
 	}
 
 	for (i = 0; i < nr; i++) {
+		/*
+		 * If previous wasn't linked and we have a linked command,
+		 * that's the end of the chain. Submit the previous link.
+		 */
+		if (!prev_was_link && link) {
+			io_queue_sqe(ctx, link, &link->submit);
+			link = NULL;
+		}
+		prev_was_link = (sqes[i].sqe->flags & IOSQE_IO_LINK) != 0;
+
 		if (unlikely(mm_fault)) {
-			ret = -EFAULT;
+			io_cqring_add_event(ctx, sqes[i].sqe->user_data,
+						-EFAULT);
 		} else {
 			sqes[i].has_user = has_user;
 			sqes[i].needs_lock = true;
 			sqes[i].needs_fixed_file = true;
-			ret = io_submit_sqe(ctx, &sqes[i], statep);
-		}
-		if (!ret) {
+			io_submit_sqe(ctx, &sqes[i], statep, &link);
 			submitted++;
-			continue;
 		}
-
-		io_cqring_add_event(ctx, sqes[i].sqe->user_data, ret);
 	}
 
+	if (link)
+		io_queue_sqe(ctx, link, &link->submit);
 	if (statep)
 		io_submit_state_end(&state);
 
···
 	DEFINE_WAIT(wait);
 	unsigned inflight;
 	unsigned long timeout;
+
+	complete(&ctx->sqo_thread_started);
 
 	old_fs = get_fs();
 	set_fs(USER_DS);
···
 static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit)
 {
 	struct io_submit_state state, *statep = NULL;
+	struct io_kiocb *link = NULL;
+	bool prev_was_link = false;
 	int i, submit = 0;
 
 	if (to_submit > IO_PLUG_THRESHOLD) {
···
 
 	for (i = 0; i < to_submit; i++) {
 		struct sqe_submit s;
-		int ret;
 
 		if (!io_get_sqring(ctx, &s))
 			break;
+
+		/*
+		 * If previous wasn't linked and we have a linked command,
+		 * that's the end of the chain. Submit the previous link.
+		 */
+		if (!prev_was_link && link) {
+			io_queue_sqe(ctx, link, &link->submit);
+			link = NULL;
+		}
+		prev_was_link = (s.sqe->flags & IOSQE_IO_LINK) != 0;
 
 		s.has_user = true;
 		s.needs_lock = false;
 		s.needs_fixed_file = false;
 		submit++;
-
-		ret = io_submit_sqe(ctx, &s, statep);
-		if (ret)
-			io_cqring_add_event(ctx, s.sqe->user_data, ret);
+		io_submit_sqe(ctx, &s, statep, &link);
 	}
 	io_commit_sqring(ctx);
 
+	if (link)
+		io_queue_sqe(ctx, link, &link->submit);
 	if (statep)
 		io_submit_state_end(statep);
 
···
 static void io_sq_thread_stop(struct io_ring_ctx *ctx)
 {
 	if (ctx->sqo_thread) {
+		wait_for_completion(&ctx->sqo_thread_started);
 		/*
 		 * The park is a bit of a work-around, without it we get
 		 * warning spews on shutdown with SQPOLL set and affinity

fs/splice.c

···
 	struct iovec iovstack[UIO_FASTIOV];
 	struct iovec *iov = iovstack;
 	struct iov_iter iter;
-	long error;
+	ssize_t error;
 	struct fd f;
 	int type;
 
···
 
 	error = import_iovec(type, uiov, nr_segs,
 			     ARRAY_SIZE(iovstack), &iov, &iter);
-	if (!error) {
+	if (error >= 0) {
 		error = do_vmsplice(f.file, &iter, flags);
 		kfree(iov);
 	}
···
 	struct iovec iovstack[UIO_FASTIOV];
 	struct iovec *iov = iovstack;
 	struct iov_iter iter;
-	long error;
+	ssize_t error;
 	struct fd f;
 	int type;
 
···
 
 	error = compat_import_iovec(type, iov32, nr_segs,
 			     ARRAY_SIZE(iovstack), &iov, &iter);
-	if (!error) {
+	if (error >= 0) {
 		error = do_vmsplice(f.file, &iter, flags);
 		kfree(iov);
 	}

include/linux/socket.h

···
 
 struct pid;
 struct cred;
+struct socket;
 
 #define __sockaddr_check_size(size)	\
 	BUILD_BUG_ON(((size) > sizeof(struct __kernel_sockaddr_storage)))
···
 extern int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg,
 			  unsigned int vlen, unsigned int flags,
 			  bool forbid_cmsg_compat);
+extern long __sys_sendmsg_sock(struct socket *sock,
+			       struct user_msghdr __user *msg,
+			       unsigned int flags);
+extern long __sys_recvmsg_sock(struct socket *sock,
+			       struct user_msghdr __user *msg,
+			       unsigned int flags);
 
 /* helpers which do the actual work for syscalls */
 extern int __sys_recvfrom(int fd, void __user *ubuf, size_t size,

include/linux/uio.h

···
 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
 		struct iov_iter *i);
 
-int import_iovec(int type, const struct iovec __user * uvector,
+ssize_t import_iovec(int type, const struct iovec __user * uvector,
 		 unsigned nr_segs, unsigned fast_segs,
 		 struct iovec **iov, struct iov_iter *i);
 
 #ifdef CONFIG_COMPAT
 struct compat_iovec;
-int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
+ssize_t compat_import_iovec(int type, const struct compat_iovec __user * uvector,
 		 unsigned nr_segs, unsigned fast_segs,
 		 struct iovec **iov, struct iov_iter *i);
 #endif

include/uapi/linux/io_uring.h

···
 		__u32		fsync_flags;
 		__u16		poll_events;
 		__u32		sync_range_flags;
+		__u32		msg_flags;
 	};
 	__u64	user_data;	/* data to be passed back at completion time */
 	union {
···
  */
 #define IOSQE_FIXED_FILE	(1U << 0)	/* use fixed fileset */
 #define IOSQE_IO_DRAIN		(1U << 1)	/* issue after inflight IO */
+#define IOSQE_IO_LINK		(1U << 2)	/* links next sqe */
 
 /*
  * io_uring_setup() flags
···
 #define IORING_OP_POLL_ADD	6
 #define IORING_OP_POLL_REMOVE	7
 #define IORING_OP_SYNC_FILE_RANGE	8
+#define IORING_OP_SENDMSG	9
+#define IORING_OP_RECVMSG	10
 
 /*
  * sqe->fsync_flags

lib/iov_iter.c

···
  * on-stack array was used or not (and regardless of whether this function
  * returns an error or not).
  *
- * Return: 0 on success or negative error code on error.
+ * Return: Negative error code on error, bytes imported on success
  */
-int import_iovec(int type, const struct iovec __user * uvector,
+ssize_t import_iovec(int type, const struct iovec __user * uvector,
 		 unsigned nr_segs, unsigned fast_segs,
 		 struct iovec **iov, struct iov_iter *i)
 {
···
 	}
 	iov_iter_init(i, type, p, nr_segs, n);
 	*iov = p == *iov ? NULL : p;
-	return 0;
+	return n;
 }
 EXPORT_SYMBOL(import_iovec);
 
 #ifdef CONFIG_COMPAT
 #include <linux/compat.h>
 
-int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
-		 unsigned nr_segs, unsigned fast_segs,
-		 struct iovec **iov, struct iov_iter *i)
+ssize_t compat_import_iovec(int type,
+		const struct compat_iovec __user * uvector,
+		unsigned nr_segs, unsigned fast_segs,
+		struct iovec **iov, struct iov_iter *i)
 {
 	ssize_t n;
 	struct iovec *p;
···
 	}
 	iov_iter_init(i, type, p, nr_segs, n);
 	*iov = p == *iov ? NULL : p;
-	return 0;
+	return n;
 }
 #endif
 

net/compat.c

···
 
 	kmsg->msg_iocb = NULL;
 
-	return compat_import_iovec(save_addr ? READ : WRITE,
+	err = compat_import_iovec(save_addr ? READ : WRITE,
 				   compat_ptr(msg.msg_iov), msg.msg_iovlen,
 				   UIO_FASTIOV, iov, &kmsg->msg_iter);
+	return err < 0 ? err : 0;
 }
 
 /* Bleech... */

net/socket.c

···
 
 	kmsg->msg_iocb = NULL;
 
-	return import_iovec(save_addr ? READ : WRITE,
+	err = import_iovec(save_addr ? READ : WRITE,
 			    msg.msg_iov, msg.msg_iovlen,
 			    UIO_FASTIOV, iov, &kmsg->msg_iter);
+	return err < 0 ? err : 0;
 }
 
 static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
···
 /*
  *	BSD sendmsg interface
  */
+long __sys_sendmsg_sock(struct socket *sock, struct user_msghdr __user *msg,
+			unsigned int flags)
+{
+	struct msghdr msg_sys;
+
+	return ___sys_sendmsg(sock, msg, &msg_sys, flags, NULL, 0);
+}
 
 long __sys_sendmsg(int fd, struct user_msghdr __user *msg, unsigned int flags,
 		   bool forbid_cmsg_compat)
···
 /*
  *	BSD recvmsg interface
  */
+
+long __sys_recvmsg_sock(struct socket *sock, struct user_msghdr __user *msg,
+			unsigned int flags)
+{
+	struct msghdr msg_sys;
+
+	return ___sys_recvmsg(sock, msg, &msg_sys, flags, 0);
+}
 
 long __sys_recvmsg(int fd, struct user_msghdr __user *msg, unsigned int flags,
 		   bool forbid_cmsg_compat)