vmci: simplify qp_dequeue_locked()

* no need for callback argument - it's always the same one
* fold __qp_memcpy_from_queue() into its only caller, get rid of dead code
* pass struct iov_iter * without casting to void *
* don't pass buf_size at all - it's always iov_iter_count(to)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/misc/vmw_vmci/vmci_queue_pair.c

@@ -142,9 +142,6 @@
 typedef int vmci_memcpy_to_queue_func(struct vmci_queue *queue,
 				      u64 queue_offset, const void *src,
 				      size_t src_offset, size_t size);
-typedef int vmci_memcpy_from_queue_func(void *dest, size_t dest_offset,
-					const struct vmci_queue *queue,
-					u64 queue_offset, size_t size);
 
 /* The Kernel specific component of the struct vmci_queue structure. */
 struct vmci_queue_kern_if {
@@ -411,11 +408,9 @@ static int __qp_memcpy_to_queue(struct vmci_queue *queue,
  * by traversing the offset -> page translation structure for the queue.
  * Assumes that offset + size does not wrap around in the queue.
  */
-static int __qp_memcpy_from_queue(void *dest,
-				  const struct vmci_queue *queue,
-				  u64 queue_offset,
-				  size_t size,
-				  bool is_iovec)
+static int qp_memcpy_from_queue_iter(struct iov_iter *to,
+				    const struct vmci_queue *queue,
+				    u64 queue_offset, size_t size)
 {
 	struct vmci_queue_kern_if *kernel_if = queue->kernel_if;
 	size_t bytes_copied = 0;
@@ -427,6 +422,7 @@ static int __qp_memcpy_from_queue(void *dest,
 		    (queue_offset + bytes_copied) & (PAGE_SIZE - 1);
 		void *va;
 		size_t to_copy;
+		int err;
 
 		if (kernel_if->host)
 			va = kmap(kernel_if->u.h.page[page_index]);
@@ -440,21 +436,12 @@ static int __qp_memcpy_from_queue(void *dest,
 		else
 			to_copy = size - bytes_copied;
 
-		if (is_iovec) {
-			struct iov_iter *to = dest;
-			int err;
-
-			err = copy_to_iter((u8 *)va + page_offset, to_copy, to);
-			if (err != to_copy) {
-				if (kernel_if->host)
-					kunmap(kernel_if->u.h.page[page_index]);
-				return VMCI_ERROR_INVALID_ARGS;
-			}
-		} else {
-			memcpy((u8 *)dest + bytes_copied,
-			       (u8 *)va + page_offset, to_copy);
+		err = copy_to_iter((u8 *)va + page_offset, to_copy, to);
+		if (err != to_copy) {
+			if (kernel_if->host)
+				kunmap(kernel_if->u.h.page[page_index]);
+			return VMCI_ERROR_INVALID_ARGS;
 		}
-
 		bytes_copied += to_copy;
 		if (kernel_if->host)
 			kunmap(kernel_if->u.h.page[page_index]);
@@ -591,21 +578,6 @@ static int qp_memcpy_to_queue_iov(struct vmci_queue *queue,
 	return __qp_memcpy_to_queue(queue, queue_offset, msg, size, true);
 }
 
-/*
- * Copies to a given iovec from a VMCI Queue.
- */
-static int qp_memcpy_from_queue_iov(void *dest,
-				    size_t dest_offset,
-				    const struct vmci_queue *queue,
-				    u64 queue_offset, size_t size)
-{
-	/*
-	 * We ignore dest_offset because dest is really a struct iovec * and
-	 * will maintain offset internally.
-	 */
-	return __qp_memcpy_from_queue(dest, queue, queue_offset, size, true);
-}
-
 /*
  * Allocates kernel VA space of specified size plus space for the queue
  * and kernel interface.  This is different from the guest queue allocator,
@@ -2679,11 +2651,10 @@ static ssize_t qp_enqueue_locked(struct vmci_queue *produce_q,
 static ssize_t qp_dequeue_locked(struct vmci_queue *produce_q,
 				 struct vmci_queue *consume_q,
 				 const u64 consume_q_size,
-				 void *buf,
-				 size_t buf_size,
-				 vmci_memcpy_from_queue_func memcpy_from_queue,
+				 struct iov_iter *to,
 				 bool update_consumer)
 {
+	size_t buf_size = iov_iter_count(to);
 	s64 buf_ready;
 	u64 head;
 	size_t read;
@@ -2705,15 +2676,15 @@ static ssize_t qp_dequeue_locked(struct vmci_queue *produce_q,
 	read = (size_t) (buf_ready > buf_size ? buf_size : buf_ready);
 	head = vmci_q_header_consumer_head(produce_q->q_header);
 	if (likely(head + read < consume_q_size)) {
-		result = memcpy_from_queue(buf, 0, consume_q, head, read);
+		result = qp_memcpy_from_queue_iter(to, consume_q, head, read);
 	} else {
 		/* Head pointer wraps around. */
 
 		const size_t tmp = (size_t) (consume_q_size - head);
 
-		result = memcpy_from_queue(buf, 0, consume_q, head, tmp);
+		result = qp_memcpy_from_queue_iter(to, consume_q, head, tmp);
 		if (result >= VMCI_SUCCESS)
-			result = memcpy_from_queue(buf, tmp, consume_q, 0,
+			result = qp_memcpy_from_queue_iter(to, consume_q, 0,
 						   read - tmp);
 
 	}
@@ -3162,8 +3133,7 @@ ssize_t vmci_qpair_dequeue(struct vmci_qp *qpair,
 		result = qp_dequeue_locked(qpair->produce_q,
 					   qpair->consume_q,
 					   qpair->consume_q_size,
-					   &to, buf_size,
-					   qp_memcpy_from_queue_iov, true);
+					   &to, true);
 
 		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
 		    !qp_wait_for_ready_queue(qpair))
@@ -3208,8 +3178,7 @@ ssize_t vmci_qpair_peek(struct vmci_qp *qpair,
 		result = qp_dequeue_locked(qpair->produce_q,
 					   qpair->consume_q,
 					   qpair->consume_q_size,
-					   &to, buf_size,
-					   qp_memcpy_from_queue_iov, false);
+					   &to, false);
 
 		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
 		    !qp_wait_for_ready_queue(qpair))
@@ -3292,9 +3261,7 @@ ssize_t vmci_qpair_dequev(struct vmci_qp *qpair,
 		result = qp_dequeue_locked(qpair->produce_q,
 					   qpair->consume_q,
 					   qpair->consume_q_size,
-					   &msg->msg_iter, msg_data_left(msg),
-					   qp_memcpy_from_queue_iov,
-					   true);
+					   &msg->msg_iter, true);
 
 		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
 		    !qp_wait_for_ready_queue(qpair))
@@ -3336,9 +3303,7 @@ ssize_t vmci_qpair_peekv(struct vmci_qp *qpair,
 		result = qp_dequeue_locked(qpair->produce_q,
 					   qpair->consume_q,
 					   qpair->consume_q_size,
-					   &msg->msg_iter, msg_data_left(msg),
-					   qp_memcpy_from_queue_iov,
-					   false);
+					   &msg->msg_iter, false);
 
 		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
 		    !qp_wait_for_ready_queue(qpair))