9pfs: introduce init_out/in_iov_from_pdu

Not all 9pfs transports share memory between request and response. For
those who don't, it is necessary to know how much memory is required in
the response.

Split the existing init_iov_from_pdu function in two:
init_out_iov_from_pdu (for writes) and init_in_iov_from_pdu (for reads).
init_in_iov_from_pdu takes an additional size parameter to specify the
memory required for the response message.

Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Greg Kurz <groug@kaod.org>

3 files changed, 27 insertions, 13 deletions

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index f9acd63..97c2926 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1652,7 +1652,11 @@ static void v9fs_init_qiov_from_pdu(QEMUIOVector *qiov, V9fsPDU *pdu,
     struct iovec *iov;
     unsigned int niov;
 
-    pdu->s->transport->init_iov_from_pdu(pdu, &iov, &niov, is_write);
+    if (is_write) {
+        pdu->s->transport->init_out_iov_from_pdu(pdu, &iov, &niov);
+    } else {
+        pdu->s->transport->init_in_iov_from_pdu(pdu, &iov, &niov, size);
+    }
 
     qemu_iovec_init_external(&elem, iov, niov);
     qemu_iovec_init(qiov, niov);
diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
index c8c9aa8..4c4feaf 100644
--- a/hw/9pfs/9p.h
+++ b/hw/9pfs/9p.h
@@ -349,8 +349,10 @@ struct V9fsTransport {
                                 va_list ap);
     ssize_t     (*pdu_vunmarshal)(V9fsPDU *pdu, size_t offset, const char *fmt,
                                   va_list ap);
-    void        (*init_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
-                                     unsigned int *pniov, bool is_write);
+    void        (*init_in_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
+                                        unsigned int *pniov, size_t size);
+    void        (*init_out_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
+                                         unsigned int *pniov);
     void        (*push_and_notify)(V9fsPDU *pdu);
 };
 
diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
index 273425b..27a4a32 100644
--- a/hw/9pfs/virtio-9p-device.c
+++ b/hw/9pfs/virtio-9p-device.c
@@ -171,26 +171,34 @@ static ssize_t virtio_pdu_vunmarshal(V9fsPDU *pdu, size_t offset,
     return v9fs_iov_vunmarshal(elem->out_sg, elem->out_num, offset, 1, fmt, ap);
 }
 
-static void virtio_init_iov_from_pdu(V9fsPDU *pdu, struct iovec **piov,
-                                     unsigned int *pniov, bool is_write)
+/* The size parameter is used by other transports. Do not drop it. */
+static void virtio_init_in_iov_from_pdu(V9fsPDU *pdu, struct iovec **piov,
+                                        unsigned int *pniov, size_t size)
 {
     V9fsState *s = pdu->s;
     V9fsVirtioState *v = container_of(s, V9fsVirtioState, state);
     VirtQueueElement *elem = v->elems[pdu->idx];
 
-    if (is_write) {
-        *piov = elem->out_sg;
-        *pniov = elem->out_num;
-    } else {
-        *piov = elem->in_sg;
-        *pniov = elem->in_num;
-    }
+    *piov = elem->in_sg;
+    *pniov = elem->in_num;
+}
+
+static void virtio_init_out_iov_from_pdu(V9fsPDU *pdu, struct iovec **piov,
+                                         unsigned int *pniov)
+{
+    V9fsState *s = pdu->s;
+    V9fsVirtioState *v = container_of(s, V9fsVirtioState, state);
+    VirtQueueElement *elem = v->elems[pdu->idx];
+
+    *piov = elem->out_sg;
+    *pniov = elem->out_num;
 }
 
 static const struct V9fsTransport virtio_9p_transport = {
     .pdu_vmarshal = virtio_pdu_vmarshal,
     .pdu_vunmarshal = virtio_pdu_vunmarshal,
-    .init_iov_from_pdu = virtio_init_iov_from_pdu,
+    .init_in_iov_from_pdu = virtio_init_in_iov_from_pdu,
+    .init_out_iov_from_pdu = virtio_init_out_iov_from_pdu,
     .push_and_notify = virtio_9p_push_and_notify,
 };